JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 249
Journal of Molecular Neuroscience
Copyright © 2006 Humana Press Inc.
All rights of any nature whatsoever are reserved.
ISSN0895-8696/06/30:249–266/$30.00
JMN (Online)ISSN 1559-1166
DOI 10.1385/JMN/30:03:249
REVIEW
Chaperones and Proteases
Cellular Fold-Controlling Factors of Proteins in Neurodegenerative Diseases and Aging
Marie-Pierre Hinault,1 Anat Ben-Zvi ,2 and Pierre Goloubinoff *,1
1DBMV,
Faculty of Biology and Medicine, Lausanne University, CH-1015 Lausanne,
Switzerland; and 2Rice Institute for Biomedical Research, Department of Biochemistry,
Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL
Received February 23, 2006; Revised April 25, 2006; Accepted April 26, 2006
Abstract
The formation of toxic protein aggregates is a common denominator to many neurodegenerative diseases
and aging. Accumulation of toxic, possibly infectious protein aggregates induces a cascade of events, such as
excessive inflammation, the production of reactive oxygen species, apoptosis and neuronal loss. A network of
highly conserved molecular chaperones and of chaperone-related proteases controls the fold-quality of proteins
in the cell. Most molecular chaperones can passively prevent protein aggregation by binding misfolding intermediates. Some molecular chaperones and chaperone-related proteases, such as the proteasome, can also hydrolyse ATP to forcefully convert stable harmful protein aggregates into harmless natively refoldable, or
protease-degradable, polypeptides. Molecular chaperones and chaperone-related proteases thus control the
delicate balance between natively folded functional proteins and aggregation-prone misfolded proteins, which
may form during the lifetime and lead to cell death. Abundant data now point at the molecular chaperones and
the proteases as major clearance mechanisms to remove toxic protein aggregates from cells, delaying the onset
and the outcome of protein-misfolding diseases. Therapeutic approaches include treatments and drugs that can
specifically induce and sustain a strong chaperone and protease activity in cells and tissues prone to toxic
protein aggregations.
DOI 10.1385/JMN/30:03:249
Index Entries: Proteasome; heat shock proteins; Hsp70; Hsp90; Hsp27; NSAIDs; inflammation; aggresome; fever.
The Folding Pathway Leading to Native
and “Alter-Native” States
The polypeptide primary sequence contains all of
the necessary information for it to reach a native
three-dimensional structure, without the apparent
need for external factors (Anfinsen, 1973). During de
novo synthesis, or translocation into the mitochondria, proteins emerge unfolded from the ribosome
or the translocation pores. When exposed to water,
hydrophobic segments tend to spontaneously
collapse into water-excluding hydrophobic cores,
surrounded by hydrophilic residues (Morgan et al.,
1998). The spontaneous formation of secondary
structures therein may then lead to a discrete native
structure (Fig. 1, reaction 1), which is, in principle,
more stable than the unfolded state. Anatively folded
monomer may already be fully functional, as in the
case of myoglobin. Yet, evolutionally more complex
enzymes may form discrete native oligomers composed of several near-native monomers, as in the
case of the hemoglobin tetramer (Suzuki and Imai,
1998). Although very similar to functional myoglobin, the unassembled nonfunctional hemoglobin
*Author to whom all correspondence and reprint requests should be addressed. E-mail: Pierre.Goloubinoff@unil.ch
Journal of Molecular Neuroscience
249
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 250
250
Hinault, Ben-Zvi, and Goloubinoff
Fig. 1. Model for the role of molecular chaperones in protein unfolding. Under physiological conditions (upper path),
an unfolded newly synthetised, or translocated polypeptide may spontaneously fold (1) into a native monomer, and/or
(2) further assemble into an “alter-native” discrete oligomer. ATPase unfolding chaperones can actively deoligomerize
(-2) “alter-native” oligomers into monomers and further unfold (-1) near-native monomers to be translocated across membranes
or degraded. Under stressful conditions (lower path), or because of mutations, a newly synthesized may spontaneously
misfold (3) into a soluble, possibly toxic monomer, which may further assemble (4) into a continuum of small toxic oligomers
that may further condense (5) into less toxic, compact amyloids. Specific organic molecules, may destabilize, and ATPase
chaperones, actively scavenge (-5, -4) compact amyloids and fibbers into looser, albeit more toxic oligomers. ATPase
chaperones may further unfold (-3) and detoxify misfolded monomers into harmless protease products or natively refolded
proteins. The leftward reactions are against entropy and ATP hydrolysis may be needed for the chaperones and proteases
to forcefully unfold stably misfolded or alternatively folded protein structures.
monomer is in a near-native state, which is, in contrast, prone to degradation by proteases. The ability
of folded proteins to alternate between native, nearnative or “alter-native” states (Fig 1, upper path),
demonstrates that within the native folding pathway, a single polypeptide chain may reach several
distinct native states, separated only by shallow
kinetic barriers (Fig. 1, reaction 2). Thus, to regulate
a given activity, cells may modulate the equilibrium
between an active native state and an inactive “alternative” state of a given polypeptide, instead of more
costly modulations of protein amounts by balancing synthesis with degradation. However, this energetically more favourable level of control necessitates
the presence of fold-controlling factors that can
specifically distinguish between native, “alternative” and nonnative states of thousands of different proteins in the cell. Experimental data now point
at the molecular chaperones, in particular at Hsp90
and Hsp70, as being such fold-controlling factors
that can regulate transitions between native
Journal of Molecular Neuroscience
monomeric and oligomeric states and thus regulate
the activity of a plethora of native protein functions
in the cell (for a review about Hsp90, see Pratt and
Toft, 2003).
The Misfolding Pathway Leading
to Aggregation
Although the polypeptide primary sequence may
contain all of the necessary information to reach a
native three-dimensional structure (Anfinsen, 1973),
under physiological conditions of temperatures,
molecular crowding and when the concentration of
un/folding intermediates is high, mistakes in the
folding/refolding process may occur, leading to
aggregation (Ellis, 2001). Some native proteins are
intrinsically more stable than others. Destabilizing
mutations, the presence of degradation or secretory
signals, transit-peptides or tags (SsrAor ubiquitin), can
increase the rate of spontaneous unfolding and the
conversion of native proteins into protease-sensitive
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 251
Hsp Chaperones and Conformational Diseases
or translocation-competent polypeptides (Prakash
and Matouschek, 2004).
Conceptually, protein misfolding is to be clearly
distinguished from unfolding and aggregation.
Unfolding is the partial, or global, loss of tertiary
and secondary structures in a protein. Misfolding
addresses possible intramolecular rearrangements
that may take place during synthesis, or following
stress-induced unfolding, within the tertiary and
secondary structures of a given polypeptide, as
compared to its native structure. The propensity of
a protein to misfold depends on intrinsic properties,
such as the relative amount and distribution of
hydrophobic and charged residues (Chiti et al., 2002),
and on the length of the polypeptide (Mogk et al.,
1999; Uversky, 2002). In contrast, aggregation is a
concentration-dependent, intermolecular process,
whereby already formed misfolded monomers tend
to associate mostly by hydrophobic interactions in
a highly cooperative manner.
Noticeably, a minority of proteins, such as Tau
and α-synuclein in neural cells, Late Embryogenesis Abundant (LEA) proteins, and dehydrins in plant
seeds are “natively unfolded” proteins that are
inclined to stay naturally devoid of secondary structures in the cytoplasm under normal conditions
(Uversky, 2002). In contrast, the remaining majority
of proteins characterized by an average chargeto-hydrophobicity ratio are highly unstable when
partially unfolded in the cell. Depending on the
degree and duration of an unfolding stress, they tend
to readily acquire nonnative misfolded structures
enriched in β-sheets that gradually aggregate into
larger, more compact and less soluble complexes
(Fig. 1, reactions 3–5). Hence, in the misfolding pathway, the protein structure is much less controlled by
the primary sequence than in the native folding pathway. Misfolding intermediates spontaneously accumulate short default cross β-conformations, some
with hydrophobic surfaces, at the expense of more
labile native α-helices (Uversky, 2003). Although proteins in their misfolded state must be thermodynamically less stable than in their native state, stable
ensembles of misfolded proteins can accumulate and
affect cells because exposed hydrophobic surfaces
must cooperatively associate to escape direct contact with water and thus form highly cohesive aggregates, fibrils, and amyloids. Here, unlike with
discrete native oligomers, aggregates span a wide
range of sizes and morphologies, depending on the
concentration of the misfolded monomers, the presence of mutations, or on the intensity and duration
Journal of Molecular Neuroscience
251
of a stress applied (for a review, see Jahn and Radford, 2005). Compared to native proteins, aggregates
may be detrimental to the cell, as they are devoid of
biological activity in the classical sense. Large aggregates can physically disrupt cells and tissues. They
expose hydrophobic surfaces that can interfere with
other misfolding proteins and with membranes. Disturbance of membrane function is of particular
importance to neurons because minor alterations
causing ion leakage (Lashuel et al., 2002), may have
dramatic consequences on neural activity (for a
review, see Caughey and Lansbury 2003). Moreover,
misfolding protein intermediates may interfere with
the native folding pathway of other proteins in the
cell and induce cross-aggregations (Satyal et al., 2000;
Ben-Zvi and Goloubinoff, 2002; Gidalevitz, et al.,
2006), a proteinaceous infectious behavior, which is
particularly effective in the case of mammalian and
yeast prions (Prusiner, 1989; Jones and Tuite, 2005).
The Cellular Role of Molecular
Chaperones
Molecular chaperones are composed of several
classes of conserved proteins (Table 1) with essential
physiological functions such as assisting the folding
of nascent polypeptides and pulling proteins across
membranes (Neupert and Brunner, 2002; Deuerling
and Bukau, 2004; De Los Rios et al., 2006). In addition,
most molecular chaperones are stressed-induced
proteins (Hsps) that can prevent the aggregation and
facilitate the correct refolding of stress-labile, or
mutation-sensitive proteins (Hartl and Hayer-Hartl,
2002). Some chaperones, in particular the small
Hsps, can also protect membrane from environmental stresses (Torok et al., 1997). By virtue of their
strong buffering on the deleterious effects of mild
aggregation-inducing mutations, the molecular
chaperones serve as capacitors for phenotypic variations, modulating the pace of molecular evolution
(Queitsch et al., 2002).
The stress-inducible nature of many molecular
chaperones has led to their early classification among
the heat shock proteins (Hsps) according to their
apparent molecular weights in gels: Hsp100, Hsp90,
Hsp70 (Hsp40, Hsp20), Hsp60 (Hsp10), and
Hsp22/27 in eukaryotes (co-chaperones in brackets), corresponding in Escherichia coli to ClpB, HtpG,
DnaK (DnaJ, GrpE), GroEL(GroES), IbpA/B, respectively (Table 1). Various mechanisms by which different individual molecular chaperones may assist
the native folding of proteins have been studied
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 252
252
Hinault, Ben-Zvi, and Goloubinoff
Table 1
Major Classes of Molecular Chaperones In Mammals: Cellular Location
and Central Functions in Protein Misfolding Diseases
Name
Cellular
location
Eukaryotes
Prokaryotes
Eukaryotes
Hsp100
Hsp90
Hsp70, Hsc70
Hsp40
Clp B
HtpG
DnaK
DnaJ
MT
Cyt, ER, MT
Cyt, ER, MT
Cyt, ER, MT
Hsp60
Hsp22/27
GroEL
IbpA, IbpB
MT
Cyt, ER, MT
ATPase
+
+
+
− (catalyzes
ATPase
in Hsp70)
+
−
Passive
prevention
of aggregation
Active
unfolding
Signalling
& prevention
of apoptosis
(overexpression)
−
+
+
+
+
?
+
−
?
+
+
+
+
+
+
−
−
+
Cyt, cytoplasm; ER, endoplasmic reticulum; MT, mitochondria; Hsp, heat-shock protein.
in vivo using mutagenesis and genetic approaches,
and in vitro using biochemical, biophysical and even
physical approaches (Goloubinoff et al., 1989;
Goloubinoff et al., 1999; Ben-Zvi et al., 2004; De Los
Rios et al., 2006). Different chaperones display mutually nonexclusive properties. Some “binding” chaperones, such as Hsp90, Hsp70, Hsp60, Hsp40, and
Hsp22/27, can provide adhesive surfaces which,
upon interaction with partially denatured polypeptides, can passively reduce the degree of aggregation (Chatellier et al., 2000; Mogk et al., 1999).
“Folding” chaperones, such as Hsp100, Hsp70, and
Hsp60 (possibly also Hsp90), are involved in the
ATP-dependent native refolding of artificially denatured polypeptides (Table 1) (Goloubinoff et al., 1989;
Goloubinoff et al., 1999; for a review, see Ben-Zvi and
Goloubinoff, 2001). Misfolded polypeptides may be
transferred from “binding” to “unfolding” chaperones, thereby allowing optimal cooperation in the
recovery of native proteins by the various chaperone systems (Veinger et al., 1998; Ben-Zvi and
Goloubinoff, 2001; Mogk et al., 2003).
The remarkable ability of the disaggregating chaperones Hsp70 and Hsp100 to recognize, bind misfolded and aggregated proteins, and forcefully
convert the latter into natively refoldable polypeptides demonstrates that chaperones can act as true
enzymes. Like enzymes, they accelerate the conversion of stable, high-affinity misfolded substrates into
more stable, low-affinity natively refolded products.
Some chaperones can use the energy of ATP-hydrolysis to overcome the high kinetic barrier between the
two states (Fig 1, reactions -5, -4, -3) (Goloubinoff
Journal of Molecular Neuroscience
et al., 1999; Ben-Zvi et al., 2004). Understanding the
mechanisms by which the chaperone and protease
network can specifically recognize toxic misfolded
protein conformers in the cell and convert them into
nontoxic, natively refolded or degraded polypeptides is central to the comprehension of proteinmisfolding neuropathologies and for conceiving
possible therapies.
The Role of the Molecular Chaperones
in Neurodegenerative Diseases
The accumulation in and outside neurons, of protein aggregates compacted into amyloid plaques,
fibrils or neurofibrillary tangles, which is accompanied by an excessive inflammatory response, oxidative stress, and cell death, are common characteristics
of most neurodegenerative diseases, such as
Alzheimer’s, Parkinson’s, Huntington’s diseases,
amyotrophic lateral sclerosis, and prion
encephalopathies (Dobson, 1999; Muchowski and
Wacker, 2005). Age is the main risk factor in most
protein-conformation neurodegenerative diseases.
Moreover, several protein conformational disorders
may develop in the same aging patients, suggesting
a general failure of the protein fold-quality control
in aging tissues (Hamilton and Bowser 2004; Forman
et al., 2002; Soti and Csermely, 2003).
There is now a large body of evidence indicating
that the molecular chaperones and chaperonecontrolled proteases, such as the proteasome, belong
to a cellular network that can prevent and reduce
the formation of toxic aggregates and possibly
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 253
Hsp Chaperones and Conformational Diseases
eliminate already formed toxic protein aggregates
in neurodegenerative diseases (Muchowski et al.,
2000; Barral et al., 2004; Klucken et al., 2004; for a
review, see Muchowski and Wacker, 2005).
Most reports thus far correlate between the presence of one, or a selective choice of molecular chaperones (typically Hsp70, Hsp40, Hsp90, and/or
Hsp27) with reduced amounts of a given neurotoxic
aggregate and, more rarely, with the clearance of
pre-existing aggregates. The general picture is as
follows.
1. Overexpression of one, or better, of the whole chaperone and protease network strongly correlates with
a diminution of protein aggregation, toxicity, inflammation, and neuronal loss. Overexpression of Hsp70
inhibits inflammation, the production of reactive
oxygen species (ROS) and consequent apoptosis.
2. Underexpression of members of the chaperone or the
protease network, as in aging, by RNA inhibition,
mutations or by using specific inhibitors, strongly
increases toxic protein aggregation, inflammation and
cell death.
3. Molecular chaperones act ubiquitously. No particular chaperone can be assigned to the relieving or curing
of a specific protein conformation disorder. All protein-misfolding diseases, among them neurodegenerative ones, favourably respond to chaperone
overexpression and negatively respond to chaperone
underexpression, mutation or inhibition.
4. Seldom, imbalanced expression between the various
chaperones (typically Hsp70 and co-chaperones) can
lead to deleterious effects.
Below, we have summarized some milestone
observations about the central role of molecular
chaperones as factors that control the fold-quality of
proteins in the cell, in the particular context of neurodegenerative diseases.
Alzheimer disease (AD) is characterized by the
extra-cellular accumulation of Aβ-amyloids and the
intracellular accumulation of neurofibrillary tangles
of the otherwise natively unfolded Tau protein (for
a review, see LaFerla and Oddo, 2005). Direct interactions among Hsp70, Hsp90, and Tau have been
observed in COS-1 cells expressing human Tau.
Induction of Hsp70 and Hsp90 by mild poisoning
with geldanamycin, correlated with increased Tau
solubility, whereas Hsp70 and Hsp90 suppression
by RNA interference significantly decreased Tau
solubility (Dou et al., 2003).
Parkinson’s disease (PD) is characterized by intracellular and membrane-interfering aggregates of the
presynaptic neuronal protein: α-synuclein (Tofaris
et al., 2005). Whereas expression of α-synuclein in
Journal of Molecular Neuroscience
253
Drosophila flies leads to neuronal loss, its co-expression with human Hsp70 significantly decreased neuronal loss (Auluck et al., 2002). This strongly suggests
that human Hsp70 can reduce neurotoxicity by
actively unfolding α-synuclein aggregates. In mammalian cells, expression of Hsp27 has protective
effects against α-synuclein and huntingtin-induced
cell-death (Zourlidou et al., 2004), probably by
passively sequestering the toxic interactive surfaces
of the aggregates.
Familial amyotrophic lateral sclerosis is a neurodegenerative disease associated with mutationinduced aggregation of Cu/Zn superoxide dismutase
(SOD-1) (Selverstone Valentine et al., 2005). Hsp70
co-expression with aggregation-prone SOD-1 can significantly lower SOD-1 aggregation and prolong cell
viability (Bruening et al., 1999). A direct association
of Hsp70, Hsp40, and αB-crystallin with mutant
SOD-1 was demonstrated by coimmunoprecipitation.
In human cell lines, a direct association between
human mutant SOD-1 and Hsp70, Hsp40 and
α−crystallin has been shown (Shinder et al., 2001).
Neuronal loss from various polyglutamine diseases results from mutations in different proteins
that generate in-frame expansions of glutamine
repeats (polyQ tracks). In a cellular model for Huntington’s disease, human neuroblastoma cells
expressing huntingtin (with extended polyQ tracts),
and the co-expression of both Hsp70 and Hsp40 or
of only Hsp40, significantly lowered huntingtin
aggregation and cell death (Wyttenbach et al., 2000).
Hsp40 is the central co-chaperone of Hsp70 that can
bind aggregates by itself, as well as catalyze Hsp70
binding onto the aggregate (Table 1) (Laufen et al.,
1999; Ben-Zvi et al., 2004). Thus, excess Hsp40 may
sequester toxic conformers. Similarly, the co-expression in mouse of the yeast chaperone Hsp104 with
the first 171 residues of a huntingtin mutant resulted
in a decrease of aggregate formation and in a 20%
increased survival as compared to mice expressing
only the mutant huntingtin (Vacher et al., 2005).
Hsp27 expression was also shown to significantly
inhibit polyQ-induced cell death, although without
reducing the formation of detectable aggregates
(Wyttenbach et al., 2002). As with excess of Hsp40,
passive binding of toxic hydrophobic surfaces by
Hsp27 may suffice to prevent the onset of an apoptotic signal. Moreover, indicating that the protective mechanism mediated by Hsp27 differs from
active aggregate-scavenging by Hsp70/Hsp40,
some endogenous Hsp70 and Hsp40, but not Hsp27,
were found sequestered into the insoluble protein
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 254
254
inclusions. In this case, alongside with neutralizing
toxic soluble aggregates in the cytosol and passively
preventing the formation of hydrophobic poreforming neurotoxic aggregates (Lashuel et al., 2002),
small Hsps may also stabilize aggregate-damaged
membranes (Torok et al., 2001).
In a cellular model of spinocerebellar ataxias,
Hsc70 and two Hsp40 isoforms were colocalized
with polyQ aggregates of mutant ataxin-3 fragments.
Coexpression of human Hsp40 suppressed ataxin-3
aggregates, whereas coexpression of Hsp70 or Hsp27
remained ineffective (Chai et al., 1999). Expression
of another human Hsp40, Hdj-2, could also suppress
aggregation of mutant androgen receptor and of
ataxin-1 (Cummings et al., 1998; Stenoien et al., 1999).
In a system modeling spinal and bulbar muscular
atrophy—cultured neuronal cells expressing truncated androgen receptor protein with an expanded
polyQ tract—only the combination of overexpressed
Hsp70 and Hsp40 can reduce the formation of aggregates and prevent apoptosis, whereas over expressing Hsp40 alone has no effect (Kobayashi et al., 2000).
Prion related-diseases are particular in that the
toxic protein aggregates can also propagate and
induce neighbouring cells to produce toxic protein
aggregates (Prusiner, 1989) and undergo apoptosis.
Prion disease in mammals results from the conformational conversion of a native, α−helix rich PrPc
protein, into an aggregation-prone, β-sheet-enriched,
infectious PrPsc species. In yeast, several nonpathological prions have been identified, from proteins
such as Sup35, Ure2, and Rnq1 (Jones and Tuite,
2005). Overproduction of the ATPase chaperone
Hsp104 (the yeast homologue of bacterial ClpB), or
of a cytosolic Hsp70 (Ssb) can transiently cure the
[PSI+] yeast prion phenotype of the Sup35 protein,
suggesting that disaggregating molecular chaperones can act upon prion particles (Chernoff et al.,
1995). The role of Hsp70 chaperones in prion curing
is, however, to be considered cautiously as overproduction of another member of the Hsp70 family,
Ssa1, resulted in the propagation of the yeast prion
(Chernoff et al., 1999).
Possible Detrimental Effects
of Chaperone Activity
Strong evidence points at abnormally exposed
hydrophobic surfaces as being the pathogenic and
infectious parts of the protein aggregates (Bieschke
et al., 2004). Simply because of differences in the
surface/volume ratio, the specific pathogenicity and
Journal of Molecular Neuroscience
Hinault, Ben-Zvi, and Goloubinoff
infectiousness of a given misfolded protein is expected
to be the highest when it is in a least-compacted
monomeric state, and the lowest when it is assembled within large compact aggregates (Fig. 1, reactions -5 and -4). Eukaryotic cells have developed a
dynein- and microtubule-dependent transport
mechanism, named the aggresome, which can
actively concentrate small toxic aggregates into
denser, presumably less harmful inclusion bodies
(Kopito, 2000). This raises the possibility of a conflict
between aggregate-detoxification by aggresomemediated compaction (Fig. 1, reaction 6) vs detoxification by chaperone-mediated unfolding of
aggregates (Fig. 1, reactions -5, -4, -3), the latter being
able to transiently generate smaller but more toxic
forms from larger less toxic amyloids. Increased
infectiousness has been demonstrated in vitro with
sonication treatments which, mimicking scavenging
chaperones, artificially converted large noninfectious
PrPsc particles into smaller infectious ones (Bieschke
et al., 2004). In yeast, although overexpression of
the scavenging chaperone Hsp104 can virtually cure
the [PSI+] prion phenotype, deletion of the hsp104
gene inhibits [PSI+] propagation (Chernoff et al.,
1995). This confirms that under specific conditions,
such as during “unprotected” scavenging by Hsp104
or Hsp70, some toxic aggregates may form and
prions may propagate from larger inactive forms
of aggregates.
Although there is overwhelming evidence that
Hsp70 overexpression, prior to or during early neurotoxic protein aggregation, has powerful neuroprotective and anti-apoptotic effects (Magrane et al.,
2004), occasional reports indicate that Hsp70 overexpression may accelerate cell death, as in the case
of tumor necrosis factor (TNF)-treated Cos-1 cells
(Ran et al., 2004) or of lentiviral-mediated overexpression of Hsp70, alongside α-synuclein in rat
brains (P. Aebischer, personal communication). Interestingly, Hsp70 has a unique molecular mechanism
whereby the energy of ATP is used to recruit random
movements of the chaperone molecule to apply a
local unfolding force on the misfolded polypeptide
susbstrate (Ben-Zvi et al., 2004; De Los Rios et al.,
2006). Thus, individual Hsp70 molecules fully suffice to breakdown large aggregated particles into
smaller ones. However, the cooperativity of at least
three Hsp70 molecules, independently bound to the
same misfolded polypeptide, is necessary to complete the unfolding of the latter into a natively refoldable species (Ben-Zvi et al., 2004). This implies that
a mild but insufficient expression of Hsp70 in the
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:51 PM
Page 255
Hsp Chaperones and Conformational Diseases
cell, as in the neuronal tissues of aging mammals,
may suffice to initiate partial breakdown of some
least-harmful amyloids into fragmented, more toxic
particles. However, at this stage, the reaction could
become stalled for lack of sufficient Hsp70 molecules
to cooperate in the final conversion of most toxic
species into harmless natively refoldable, or protease-degradable, species (De Los Rios et al., 2006).
There is no obvious Hsp104 homolog in human that
can assist Hsp70-mediated protein disaggregation.
However, neural cells may still recruit binding chaperones, such as Hsp27 (Patel et al., 2005), to reduce
the transient toxicity of newly formed hydrophobic
surfaces during amyloid scavenging by Hsp70.
The Role of the Proteasome
in Neurodegenerative Diseases
In agreement with the observations that chaperones
and the proteasome carry complementing protective
cellular mechanisms against protein-conformational
diseases (Fig. 1, reaction 7), immunostaining has
revealed the presence of ubiquitin, proteasomal subunits and of Hsp70 in neuronal nuclei of cells with
amyloids of several diseases, including AD, Parkinson’s disease, and prion diseases (Adori et al., 2005).
Inhibition of the proteasome activity with MG-132
in mouse cell lines and primary neurons, or inhibition of calpain or other cytosolic proteases, favors
the cytosolic accumulation of PrPsc and prion pathogenesis (Wang et al., 2005c). Noticeably, the endoplasmic reticulum Hsp70 (BIP) controls the folding
of PrP, and an anomalous, prolonged association
between BIP and mutant PrP32 inhibits subsequent
proteasome-mediated degradation of the misfolded
PrP32, leading to prion disease (Jin et al., 2000). Similarly, aggregated α-synuclein strongly associates and
inhibits proteasome activity, suggesting that proteasome-mediated degradation of misfolded α-synuclein
is a central cytoprotective mechanism in Parkinson’s
disease. Indeed, rats treated with proteasome
inhibitors developed typical Parkinson pathologies
(Nomoto and Nagai, 2005). In human neuroblastoma
cells expressing the α-synuclein mutant A53T,
co-expression of Parkin, a E3-ubiquitin-ligase, alleviates the α-synuclein toxicity (Petrucelli et al., 2002).
Similarly, in human neuroglioma cells, co-expression
of CHIP, an Hsp70 co-chaperone with an E3-ubiquitin-ligase activity acting as a molecular switch between
proteasomal and lysosomal degradation pathways,
decreases the levels of aggregated α-synuclein (Shin
et al., 2005). In COS cells, CHIP co-expression with a
Journal of Molecular Neuroscience
255
truncated polyQ-rich human huntingtin suppressed
both huntingtin aggregation and toxicity (Miller et
al., 2005). In mouse neuroblastoma cell lines, overexpression of another E3 ubiquitin ligase, Dorfin,
provided protection from neurotoxic mutant SOD-1
(Niwa et al., 2002). Because E3 ubiquitin-ligases have
a significantly more restricted spectrum of substrates
than the molecular chaperones and proteases, it is
possible that targeted degradation of specific neurotoxic aggregates can be achieved by overexpressing
specific E3 ubiquitin-ligases.
Aging
A general age-dependent decrease in the ability
to express Hsps and antioxidant enzymes under
stress is observed in all multicellular organisms, from
mammals, nematodes, and insects, to plants (Morrison et al., 2005; Starnes et al., 2005). Failure of aging
humans to induce and maintain a molecular heatshock response consequent to an abiotic, or a cellular stress, strongly correlates with the onset of
protein-conformation disorders, in particular of
neurodegenerative diseases (Soti and Csermely,
2003). Figure 2A shows a scheme of the various agedependent processes, correlating the decline of chaperone and proteasome activity in the cell, with
expected levels of toxic aggregates and of inflammation leading to fatal neuronal loss. Because the
stability of the native state is primarily an intrinsic
property of each protein, the rate of spontaneous
protein unfolding, leading to misfolding and aggregation, is expected to be rather constant during
lifetime, with a possible mild increase later in life due to
cumulative mutations and damages from polluting
chemicals such as heavy metals (Basha et al., 2005),
ionizing radiations, ozone, tobacco smoke, and
environmental stresses (ultraviolet light, temperature variations etc.) (Manton et al., 2004; Landrigan
et al., 2005). Early in life, however, the chaperone
and protease network is optimally inducible and can
effectively prevent the steady formation of small
toxic aggregates and, furthermore, actively unfold,
reactivate, or eliminate all the misfolded species that
may form in young unstressed cells. Later in life,
when the chaperone and protease network becomes
gradually deficient (Heydari et al., 2000), toxic
aggregates may accumulate, but partial protection
may still be achieved by active secretion, lysosomal
degradation, or aggresome-mediated sequestration
of the most toxic species into dense fibbers and
compact amyloids (Kopito, 2000). Yet, above a critical
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 256
256
Fig. 2. Scheme of the age-dependent processes leading
to fatal neuronal loss. Early in life, the chaperone and protease networks are optimally inducible and active. They
effectively prevent the accumulation of toxic protein aggregates. The rate of spontaneous misfolding and aggregation
is constant, with a possible mild increase later in life because
of cumulative mutations and stress-induced damages. Later
in life, the chaperone and protease network become deficient and toxic aggregates accumulate. Some aggregates
are partially sequestered by the aggresome, others induce
inflammation and reactive oxygen species, leading to fatal
neuronal loss. (A) Early failure of the chaperone and protease network lead to early death by neurodegeneration.
(B) Effect of improved activity (arrow) of the chaperone and
protease network, by Hsp-inducing drugs or treatments,
delay in fatal neuronal loss and increase in life expectancy.
threshold of aggregation, the various cell defences
may become overpowered, inducing an inflammatory
response with the release of ROS, leading to apoptosis
(Soti and Csermely, 2003).
The Proteasome and Aging
The activity of the proteasome has been reported
to decrease with age in cell cultures and in vivo
(for a review, see Gaczynska et al., 2001). Decline of
proteasome activity has been reported in several
aged human tissues, such as lens, muscle, lymphocytes, and epidermis, as well as in senescing human
primary cultures. A similar tendency was observed
Journal of Molecular Neuroscience
Hinault, Ben-Zvi, and Goloubinoff
in aging tissues of other mammals (for a review see
Chondrogianni and Gonos 2005). Free ROS produced
by chronic inflammation can cause cumulative
damages to cellular macromolecules and in particular lipids and proteins, and seems to contribute
to senescence and aging, age-related disorders, and
neuromuscular degenerative diseases. The accumulation of oxidized proteins has been reported
in many aging and models of protein-misfolding
diseases. In young individuals, mildly oxidized
and aggregated proteins are rapidly degraded by
the proteasome. As in the case of molecular chaperones, the specificity of the proteasome could
depend on the extent of misfolding in oxidized proteins. The 20S proteasome may directly bind and
degrade such mildly damaged proteins, without
needing the ubiquitin targeting. Severely oxidized,
aggregated, and crosslinked proteins, however, are
less efficient substrates for degradation and may
stall the proteasome during aging and in many
age-related conformational disorders (Ferrington
et al., 2005; Davies and Shringarpure, 2005). During
cellular aging and inflammatory degenerative
diseases, the combination between the steady
increase of protein damage from ROS and the
steady decrease in proteasome expression and
activity may result in the accumulation of toxic
protein species, leading to cell death (for a review,
see Ciechanover, 2006).
The artificial triggering of a heat-shock response
in neural cells during the onset of neurodegenerative diseases, or during aging, is expected to improve
cellular levels of chaperones and proteases (Fig. 2B,
arrow) and consequently delay the accumulation of
toxic protein aggregates. To lower neuronal loss and
increase life quality and expectancy, therapeutic
approaches may include the use of Hsps inducers,
in turn preventing and actively reverting protein
aggregation. Complementing therapeutic approaches
may include the use of direct inhibitors of protein
aggregation and of anti-oxidants able to directly
quench ROS damages, and inhibit ROS-mediated
apoptotic signals.
Therapeutic Approaches: AggregateInterfering Compounds
A number of small organic molecules have been
shown to retard and, more rarely, to reverse the
formation of toxic protein aggregates in various in
vivo and in vitro model systems. Compounds with
high affinity for aggregated proteins, such as the
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 257
Hsp Chaperones and Conformational Diseases
amphiphilic fluorescent dye Bis-ANS, can inhibit the
in vitro aggregation of PrPsc (Cordeiro et al., 2004).
Similarly, congo red, a dye used to detect amyloid
deposits in histological slices, can inhibit α-synuclein formation in vitro and in cell cultures (Heiser
et al., 2000). Feeding congo red or cystamine to
Drosophila flies expressing a polypeptide with an
expanded polyQ-repeat suppressed degeneration of
photoreceptors and neurons (Apostol et al., 2003).
In a transgenic mouse model for Huntington disease, the transglutaminase inhibitor cystamine,
increased survival and improved motor function
(Dedeoglu et al., 2002). Rifampicin applied to rat
cells inhibited the aggregation and neurotoxicity of
synthetic Amyloid-β peptides (Tomiyama et al.,
1996). Interestingly, rifampicin can strongly bind to
α-synuclein monomers, inhibit fibrillation, and possibly mediate the solubilization of preformed
α-synuclein fibbers in vitro, suggesting a direct interference of rifampicin with toxic α-synuclein aggregates in the cell (Li et al., 2004b). Similarly, curcumin
treatments abrogated retention of myelin protein
zero aggregates into the endoplamic reticulum (ER)
and reduced aggregate-induced apoptosis (Khajavi
et al., 2005), as well as the formation of Amyloid-β
oligomers and fibrils (Yang et al., 2005).
The various beneficial effects of small organic
compounds, such as Bis-ANS, Thyoflavin-T, curcumin, and congo Red, on aggregate reduction in
cells raises the question of their precise mechanism
of action. In a cell-free system, interfering compounds often bind strongly to stable aggregates,
although without causing solubilization. Therefore,
similar high-affinity binding of such compounds
in the cell may not necessarily drive to the solubilization of compact amyloids. Consequently,
candidate therapeutic molecules should first be
tested for their potential ability to induce the
expression of molecular chaperones and proteases.
This should allow one to distinguish between direct
aggregate-interfering compounds and Hsp-inducing
compounds acting indirectly on aggregates by
way of increasing the aggregate- scavenging activity
of the cell.
Hsp-Inducing Treatments
The demonstrated ability of stress-inducible chaperones and proteases to prevent the accumulation of
toxic protein aggregates in the cell implies that drugs
capable of increasing Hsp expression, without
increasing the misfolding propensity of sensitive
Journal of Molecular Neuroscience
257
proteins, may delay the onset of, and possibly cure,
protein-misfolding and age-related diseases.
Caloric Restriction and Hormonal Treatments
In mammalian cells, glucose starvation induces
the massive accumulation of a specific subset of ERlocated molecular chaperones, such as Grp78 and
Grp94 (for a review, see Lee, 2001). Grp78 overexpression provides protection of cells against induced
apoptosis (Liu et al., 1997; Reddy et al., 1999). Interestingly, high levels of both chaperones in the brain
of young rats correlate with higher resistance to
seizures, compared to older rats expressing less
Grp78 and Grp94 (Little et al., 1996). Mild hypoglycemia may thus suffice to induce ER chaperones,
which in turn may increase the resistance of cells
to various stresses, age-dependent protein aggregations in the ER, and aggregate-induced apoptosis.
Noticeably, caloric restriction is the most effective
anti-aging treatment in mammals (for a review, see
Kirkwood and Shanley, 2005). Caloric restriction,
while increasing levels of molecular chaperones,
also prevents age-related declines of glycolytic
enzymes in the neural retina of aging rats (Li et al.,
2004a). Interestingly, treatments with estrogens and
androgens, in addition to glucose regulating hormones, also increased Hsp70 levels in human
neurons and induced resistance to toxic intracellular amyloids (Zhang et al., 2004). It is therefore
possible that the anti-aging effect of mild caloric
restriction and of some hormonal treatments affecting glucose uptake are mediated, in part, by way
of induced Hsp-expression with anti-inflammatory, anti-apoptotic, and anti-protein aggregation
activities.
Heat-Shock
Since antiquity, repeated mild heat-shock treatments, in the form of hot baths and saunas, are
considered to have age-retarding and relieving
effects on age-related chronic diseases. It is now
well established in all organisms that repeated mild
thermal treatments can prime the accumulation of
heat-inducible proteins, most of which being
transcription factors, molecular chaperones and
proteases (Kregel, 2002). Indeed, mild heat-shock
treatments are the simplest way to induce Hsps in
the cell and gain protection, both against direct
damages from subsequent harsher environmental
stresses, and against indirect damages from
ROS-induced inflammation leading to cell death
(Beere, 2004).
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 258
258
The Role of Fever
Hippocrates (460–377 B.C.) is quoted to have said:
“Give me the power to create a fever and I shall cure
every illness.” During inflammation, homeothermal
organisms develop high fever, during which high
levels of Hsps accumulate everywhere, including in
the central nervous system, in correlation with the
onset of various healing processes (for a review, see
Moseley, 1998). As in the case of the response to heatshock, the ability of animals to induce high fever and
Hsps decreases with age (Soti and Csermely, 2003;
Macario and Conway de Macario, 2005). Elevated
levels of heat-shock proteins are nonetheless often
observed associated to various forms of amyloids
and protein aggregates in degenerated neural tissues
of deceased aged patients, which is not necessarily
in contradiction with the general observation that
Hsp-inducibility late in life is mediocre: aging tissues
exposed to toxic aggregates may have first attempted
to recruit some Hsps, but having failed to recruit
enough of them, succumb to programmed cell death.
Noticeably, repeated mild heat-shock treatments can
partially restore Hsp-inducibility in aging flies
(Hercus et al., 2003) and increase post-heat stress
survival of organisms as different as bacteria, yeast,
plants, nematodes, and mammals (Rattan, 2004). This
suggests that repeated mild heat-treatments in aging
humans with protein conformational diseases may
restore some ability to induce and accumulate
molecular chaperones and proteases, and thus
prevent toxic aggregation in neurones, delaying the
onset of cell death.
Aging mammals, humans in particular, also show
deregulated inflammatory responses (Bruunsgaard
et al., 2001). For example, aging rats become increasingly
defective at developing high fever (Plata-Salaman
et al., 1998). In aging humans and patients suffering
from chronic inflammatory diseases, a positive correlation exists between serum levels of Hsp70 and
various inflammatory markers, such as TNF-α,
C-reactive protein, and fibrinogen. This suggests
that Hsp70 is directly linked to the inflammatory
response, as well as to the immune and autoimmune
responses (Njemini et al., 2004). For example, in
rheumatoid arthritis and other spondyloarthropathies, with a pathogenesis attributed, in part, to
the interaction between genetic and environmental
factors, synovial cells continuously over-express
Hsp70 or Hsc70 (Vargas-Alarcon et al., 2002). Hsc70
may be upregulated as a result of the high activity
of these cells in several respects, including antigen
processing and presentation (Schick et al., 2004). The
Journal of Molecular Neuroscience
Hinault, Ben-Zvi, and Goloubinoff
most recent hypothesis implies a special interaction
between HLA-DR chains from rheumatoid arthritis
and members of the Hsp70s, which may affect antigen
processing and antigen presentation (Roth et al.,
2002). Indeed, the loading of the DR molecules with
T-cell epitopes and presentation apparently depends
on Hsc70 levels. Moreover, Hsp70 and Hsp60 have
been shown to protect against cell death by interfering with the mitochondrial apoptosis pathway
(Saleh et al., 2000; Zamostiano et al., 1999). Yet, when
applied on the external surface of cells, Hsp70 may
have a pro-inflammatory role (Asea et al., 2000; Asea
et al., 2002). This is exemplified in the case of the
acute respiratory distress syndrome (ARDS), which
is an inflammatory response in the lungs resulting
from severe damage to alveolar cells, culminating
in necrosis and fatal apoptosis, especially in aging
patients. Sepsis-induced ARDS in rats has been
shown to correlate with the specific failure of Hsp70
to be expressed in alveolar tissues (Weiss et al., 2000).
In a rat model of sepsis-induced ARDS, adenovirusmediated transient expression of Hsp70 in the lungs,
effectively prevented apoptosis and lung failure. It
dramatically improved survival (Weiss et al., 2002).
These effects are partly due to a mechanism whereby
Hsp70 directly impairs proteasomal degradation of
IkBα (Weiss Y., personal communication). Interestingly, during the viral infection that caused the Severe
Acute Respiratory Syndrome (SARS) outbreak, the
death toll from an ARDS was lower than 10% in
patients younger than 35 yr, but reached 66% in
patients older than 75 years (Ghani et al., 2005). It is
tempting to speculate that the diminished ability of
aging SARS patients to induce Hsp70 accumulation
in septic lungs could partly account for the strong
age-dependent death toll in SARS patients.
Hsp-Inducing Drugs by Partial Poisoning
Some successful attempts to reduce neurotoxic
protein aggregations have been obtained with a class
of chemicals that can induce a heat-shock response
at physiological temperature, as a result of partial
poisoning by inhibition of protein synthesis, of chaperone-mediated protein un-folding, or of the protein
degradation machinery. Chinese hamster ovary
cells treated with intermediate concentrations of
puromycin (20 mg/mL) showed a 1.5-fold increase
in the synthesis of Hsps, including Hsp70. However,
higher concentrations of puromycin (e.g., 100
mg/mL) resulted in an inhibition of Hsp synthesis
(Lee and Dewey, 1987). Similarly, subsaturating
concentrations of specific inhibitors of Hsp90
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 259
Hsp Chaperones and Conformational Diseases
(geldanamycin and radicicol) (Hay et al., 2004) or of
the proteasome (MG-132 and lactacystin) were also
shown to induce a strong heat-shock response, leading
to Hsp accumulation and some anti-aggregation
effects (Holmberg et al., 2000). Thus, subinhibitory
amounts of geldanamycin and radicicol in mice
cells increased the sodium dodecyl sulfate (SDS)solubility of polyQ-aggregates and of α-synuclein
in human and Drosophila cells (McLean et al., 2004).
In a rat model for Parkinson’s disease, exposure to
the proteasome inhibitor 6-hydroxyl dopamine
showed a protective effect on dopaminergic cell
death. Co-treatment of lactacystin and MG-132
significantly prevented the nigral degeneration and
appearance of α-synuclein and ubiquitin-positive
inclusions in substantia nigra (Inden et al., 2005).
However, Hsp induction by poisoning is expectedly
prone to severe adverse effects. Most inhibitors are
hydrophobic and cannot be simply delivered to neural
cells at precise low Hsp-inducing concentrations while
being safely kept below excessive concentrations
capable of inducing apoptosis. There is a significant
risk that treatment with a mild excess of Hsp90 or
proteasome inhibitors may induce apoptosis, as they
do in anti-cancer protocols (Setsuie et al., 2005).
Anti-Inflammatory and Hsp-Inducing Drugs
As alternatives to partial poisoning drugs and
problematic thermotherapies, other drugs can specifically induce a heat-shock-like response at physiological temperature, without apparent cell poisoning.
Cyclopentenone prostaglandins (PGA2 and D12PGJ2) were among the first compounds to show a
strong activation of Hsp70 synthesis in HeLa cells
(Ohno et al., 1988). More recently, treatment of human
cells with the antiproliferative prostaglandin A1 activated the heat-shock transcription factor (Hsf1) and
consequently the accumulation of Hsp70 and Hsp90
(Amici et al., 1992). Whereas a moderate inflammatory response, in part mediated by high fewer
following infection (as in septic lungs) or by protein
aggregation in brain tissues, may contribute to the
general induction and accumulation of anti-apoptotic
heat-shock proteins, an excessive deregulated inflammatory response can lead to cell death and tissue
degeneration (Beere and Green, 2001; Craft et al., 2005).
This suggests possible therapies for neurodegenerative diseases with anti-inflammatory drugs. Yet,
because anti-inflammatory drugs may also decrease
fever, they should be chosen according to their
ability to maintain Hsp accumulation despite their
ability to decrease fever (Marchetti and Abbracchio,
Journal of Molecular Neuroscience
259
2005). This is the case for some famous commercial
remedies, such as the nonsteroidal anti-inflammatory
drug (NSAIDs) ibuprofen (Wang et al., 2005b), and
acetyl-salicylic acid (aspirin), which can both reduce
fever and inflammation while keeping a strong heatshock like response at physiological temperatures, in
terms of nuclear relocalization of Heat-shock factor-1
and of massive production molecular chaperones such
as Hsp70 and Hsp90, not only in animals (Jurivich et
al., 1992; Westerheide and Morimoto, 2005), but also
in plants (Saidi et al., 2005). The ability of some
NSAIDs to maintain high Hsp levels while decreasing unwanted effects of excessive inflammation could
account for their significant healing effects on inflammation-induced neuronal loss (Marchetti and
Abbracchio, 2005). For example, in HeLa cells,
ibuprofen induction of Hsp70 correlates with a
reduced aggregation of a polyalanine expansion
mutant of poly(A)-binding protein, a hallmark of
oculopharyngeal muscular dystrophy (Wang et al.,
2005b). Epidemiological data have shown that constant treatment with NSAIDs reduces the risk of
Parkinson’s diseases by 45%, compared to patients
taking NSAIDs on a nonregular basis (Schiess, 2003).
Similarly, prolonged use of NSAIDs was shown to
reduce the risk of developing AD and delay the onset
of the disease. Studies with Flurbiprofen or ibuprofen in AD transgenic mice have shown that the effects
of these NSAIDs on Aβ deposition are reached at
plasma levels similar to those achieved in humans
at therapeutic dosage (for a review, see Gasparini
et al., 2004).
Other Hsp-Inducing Drugs
Recently, very old and new compounds were
added to the list of least poisonous heat-shock
response inducers, such as Bimoclomol (Vigh et al.,
1997), Arimoclomol (Kieran et al., 2004), Arachidonic
acid, Curcumin, Resveratrol (the French paradox,
Delmas et al., 2005), Geranylgeranylacetone (Susuki
et al., 2005) and Celastrol (Westerheide et al., 2004).
Very low concentrations of these compounds can
strongly induce Hsf-1 expression and heat-shock protein accumulation in eukaryotic cells, likely by way
of modulating membrane fluidity or by interfering
with the heat-shock signalling pathway (Jurivich
et al., 1992; Vigh et al., 1997; Hargitai et al., 2003). The
antiulcer drug Geranylgeranylacetone strongly
induced Hsp70 in various tissues without apparent
adverse effects and caused a marked inhibition of
apoptosis and of oxydative damages related to
ischemic heart reperfusion, renal failure and liver
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 260
260
transplantation (Suzuki et al., 2005). Moreover, oral
uptake of Geranylgeranylacetone leads to neuroprotection against cerebral infarction in rats and
alleviates polyglutamine-mediated motor neuron
disease (Katsuno et al., 2005; Uchida et al., 2006). The
membrane fluidizer Arimoclomol can significantly
delay the progression of amyotrophic lateral sclerosis in transgenic mice overexpressing mutant human
SOD-1 (Kieran et al., 2004). Micromolar amounts of
Celastrol, a quinone triterpene from the Chinese pharmacopoeia, also strongly activates the heat shock
transcription factor Hsf1 and chaperone accumulation in plants (Saidi and Goloubinoff, personal communication) and in human cells, with kinetics similar
to heat stress (Westerheide et al., 2004). Celastrol is
also effective at reversing the abnormal cellular localization of full-length mutant Huntingtin observed in
striatal cells (Wang et al., 2005a).
Hsp-Inducing Peptides
Whereas external application of short insoluble
peptide aggregates, such as β-amyloid, can induce
neural cell death in vitro, soluble neurotrophic peptides, such as the vasoactive intestinal peptide (VIP)
and the activity-dependent neurotrophic factor
(ADNF), can protect neural cells from β-amyloid
induced apoptosis (for a review, see Gozes et al., 2005).
Hence, VIP-stimulated astrocytes can secrete short
peptides, such as ADNF, which, already at femtomolar
concentrations, can increase the levels of mitochondrial Hsp60 while protecting neurons from death
associated with a broad range of toxins, including
those related to Alzheimer’s disease (Zamostiano et al.,
1999). It is therefore possible that by way of inducing
mitochondrial chaperonins, natural neuropeptides
may arrest apoptosis, leading to the development of
possible peptide-based drugs against proteinmisfolding diseases (Gozes and Brenneman, 1996).
Hinault, Ben-Zvi, and Goloubinoff
3. Passive protection: binding chaperones can bind
hydrophobic surfaces of already formed aggregates
and protect membranes and proteins from toxic
interactions.
4. Active unfolding: ATPase chaperones can forcefully
unfold misfolded and aggregated proteins and allow
their native refolding into nontoxic functional proteins (see Table 1).
5. Sequestration: the aggresome can actively sequester
by compaction toxic misfolded species into inclusion
bodies.
6. Secretion: toxic aggregates such as Aβ−amyloids or
PrPsc can be secreted outside the cell.
7. Controlled degradation: chaperone-gated proteases
degrade and recycle non-recoverable damaged
proteins (see Fig 1).
In aging cells, or during abiotic stress or pathogen
attack, the chaperone and protease network may
become overloaded because of massive protein
damage, deficient responsiveness, and insufficient
Hsp accumulation, or because of mutations in substrate proteins or in the chaperones (Fig 2). Several
therapeutic approaches were discussed here that can
potentially improve neurone responsiveness to toxic
protein aggregation or to heat- and oxidative stresses,
thereby increasing the cellular levels of Hsps. Combinations of treatments such as caloric restriction,
mild heat-shocks, peptides, and drugs capable of
increasing chaperone and protease levels without
overloading or poisoning the cell, and without
increasing the amount of protein aggregates in the
cell, are likely to improve cell survival to protein
misfolding and reduce neuronal loss. In addition to
treating various neurodegenerative diseases, Hspinducing treatments, possibly in combination with
dietary antioxidants (for a review, see Cui et al., 2004),
may also relieve other protein misfolding and inflammatory diseases such as cystic fibrosis (Gelman and
Kopito, 2002), diabetes (Hayden et al., 2005), and, in
general, aging (for a review, see Macario and Conway
de Macario, 2005).
Conclusions
Molecular chaperones are fold-controlling factors
(see Table 1) that can specifically recognize misfolded
or alternatively folded protein structures in the cell.
Chaperones can single out and remove atypical,
potentially toxic, and infectious protein structures
by various cellular programs:
1. Prevention: binding chaperones can bind misfolded
proteins and prevent them from forming large aggregates.
2. Passive unfolding: aggregate-interfering compounds
can destabilize aggregated proteins.
Journal of Molecular Neuroscience
Acknowledgments
We thank Jacques Beckmann, Hilal Lashuel, and
Yoram Weiss for discussions. Funded in part by
grant 31-65211.01 from the Swiss National Science
Foundation and the Zwahlen fund for research on
Parkinson’s disease, Lausanne, Switzerland.
References
Adori C., Kovacs G., Low P., et al. (2005) The ubiquitinproteasome system in Creutzfeldt-Jakob and Alzheimer
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 261
Hsp Chaperones and Conformational Diseases
disease: intracellular redistribution of components
correlates with neuronal vulnerability. Neurobiol. Dis.
19, 427–435.
Amici C., Sistonen L., Santoro M. G., and Morimoto R. I.
(1992) Antiproliferative prostaglandins activate heat
shock transcription factor. Proc. Natl. Acad. Sci. U. S. A.
89, 6227–6231.
Anfinsen C. B. (1973) Principles that govern the folding
of protein chains. Science 181, 223–230.
Apostol B. L., Kazantsev A., Raffioni S., et al. (2003) A cellbased assay for aggregation inhibitors as therapeutics
of polyglutamine-repeat disease and validation in
Drosophila. Proc. Natl. Acad. Sci. U. S. A. 100, 5950–5955.
Asea A., Kraeft S. K., Kurt-Jones E. A., et al. (2000) HSP70
stimulates cytokine production through a CD14- dependant pathway, demonstrating its dual role as a chaperone and cytokine. Nat. Med. 6, 435–442.
Asea A., Rehli M., Kabingu E., et al. (2002) Novel signal
transduction pathway utilized by extracellular HSP70:
role of toll-like receptor (TLR) 2 and TLR4. J. Biol. Chem.
277, 15,028–15,034.
Auluck P. K., Chan H. Y., Trojanowski J. Q., Lee V. M., and
Bonini N. M. (2002) Chaperone suppression of alphasynuclein toxicity in a Drosophila model for Parkinson’s disease. Science 295, 865–868.
Barral J. M., Broadley S. A., Schaffar G., and Hartl F. U.
(2004) Roles of molecular chaperones in protein misfolding diseases. Semin. Cell. Dev. Biol. 15, 17–29.
Basha M. R., Wei W., Bakheet S. A., et al. (2005) The fetal
basis of amyloidogenesis: exposure to lead and latent
overexpression of amyloid precursor protein and betaamyloid in the aging brain. J. Neurosci. 25, 823–829.
Beere H. M. (2004) “The stress of dying”: the role of heat
shock proteins in the regulation of apoptosis. J. Cell.
Sci. 117, 2641–2651.
Beere H. M. and Green D. R. (2001). Stress management—
heat shock protein-70 and the regulation of apoptosis.
Trends Cell. Biol. 11, 6–10.
Ben-Zvi A. P. and Goloubinoff P. (2001) Review: mechanisms of disaggregation and refolding of stable protein
aggregates by molecular chaperones. J. Struct. Biol. 135,
84–93.
Ben-Zvi A. P. and Goloubinoff P. (2002) Proteinaceous
infectious behavior in non-pathogenic proteins is
controlled by molecular chaperones. J. Biol. Chem. 277,
49,422–49,427.
Ben-Zvi A., De Los Rios P., Dietler G., and Goloubinoff P.
(2004) Active solubilization and refolding of stable
protein aggregates by cooperative unfolding action of
individual hsp70 chaperones. J. Biol. Chem. 279, 37,298–
37,303.
Bieschke J., Weber P., Sarafoff N., Beekes M., Giese A., and
Kretzschmar H. (2004) Autocatalytic self-propagation
of misfolded prion protein. Proc. Natl. Acad. Sci. U. S. A.
101, 12,207–12,211.
Bruening W., Roy J., Giasson B., Figlewicz D. A., Mushynski W. E., and Durham H. D. (1999) Up-regulation of
protein chaperones preserves viability of cells expressing toxic Cu/Zn- superoxide dismutase mutants asso-
Journal of Molecular Neuroscience
261
ciated with amyotrophic lateral sclerosis. J. Neurochem.
72, 693–699.
Bruunsgaard H., Pedersen M., and Pedersen B. K. (2001)
Aging and proinflammatory cytokines. Curr. Opin.
Hematol. 8, 131–136.
Chai Y., Koppenhafer S. L., Bonini N. M., and Paulson H. L.
(1999) Analysis of the role of heat shock protein
(Hsp) molecular chaperones in polyglutamine disease.
J. Neurosci. 19, 10,338–10,347.
Chatellier J., Hill F., and Fersht A. R. (2000) From minichaperone to GroEL 2: importance of avidity of the multisite ring structure. J. Mol. Biol. 304, 883–896.
Caughey B. and Lansbury P. T. (2003) Protofibrils, pores,
fibrils, and neurodegeneration: separating the responsible protein aggregates from the innocent bystanders.
Annu. Rev. Neurosci. 26, 267–298.
Chernoff Y. O., Lindquist S. L., Ono B., Inge-Vechtomov
S.G., and Liebman S. W. (1995) Role of the chaperone
protein Hsp104 in propagation of the yeast prion-like
factor [psi+]. Science 268, 880–884.
Chernoff Y. O., Newnam G. P., Kumar J., Allen K., and
Zink A. D. (1999) Evidence for a protein mutator in
yeast: role of the Hsp70-related chaperone ssb in
formation, stability, and toxicity of the [PSI] prion. Mol.
Cell. Biol. 19, 8103–8112.
Chiti F., Taddei N., Baroni F., et al. (2002) Kinetic partitioning of protein folding and aggregation. Nat. Struct.
Biol. 9, 137–143.
Chondrogianni N. and Gonos E. S. (2005) Proteasome dysfunction in mammalian aging: steps and factors
involved. Exp. Gerontol. 40, 931–938.
Ciechanover A. (2006) The Ubiquitin proteolytic system:
from a vague idea, through basic mechanisms and onto
human diseases and drug targeting Neurology 66,
S7–S19.
Cordeiro Y., Lima L. M., Gomes M. P., Foguel D., and Silva
J. L. (2004) Modulation of prion protein oligomerization, aggregation, and beta-sheet conversion by 4,4′dianilino-1,1′binaphthyl- 5,5′-sulfonate (bis-ANS).
J. Biol. Chem. 279, 5346–5352.
Craft J. M., Watterson D. M., and Van Eldik L. J. (2005)
Neuroinflammation: a potential therapeutic target.
Expert Opin. Ther. Targets 9, 887–900.
Cui K., Luo X., Xu K., and Ven Murthy M. R. (2004) Role
of oxidative stress in neurodegeneration: recent developments in assay methods for oxidative stress and
nutraceutical antioxidants. Prog. Neuropsychopharmacol. Biol. Psychiatry. 28, 771–799.
Cummings C. J., Mancini M. A., Antalffy B., DeFranco D. B.,
Orr H.T., and Zoghbi H.Y. (1998) Chaperone suppression of aggregation and altered subcellular proteasome
localization imply protein misfolding in SCA1. Nat.
Genet. 19, 148–154.
Davies K. J. and Shringarpure R. (2005) Preferential degradation of oxidized proteins by the 20S proteasome may
be inhibited in aging and in inflammatory neuromuscular diseases. Neurology, in press.
De Los Rios P., Ben-Zvi A., Slutsky O., Azem A., and
Goloubinoff P. (2006) Hsp70 chaperones accelerate
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 262
262
protein translocation and the unfolding of stable
protein aggregates by entropic pulling. Proc. Natl.
Acad. Sci. U. S. A. 103, 6166–6171.
Dedeoglu A., Kubilus J. K., Jeitner T. M., et al. (2002) Therapeutic effects of cystamine in a murine model of Huntington’s disease. J. Neurosci. 22, 8942–8950.
Delmas D., Jannin B., and Latruffe N. (2005) Resveratrol:
preventing properties against vascular alterations and
ageing. Mol. Nutr. Food. Res. 49, 377–395.
Deuerling E. and Bukau B. (2004) Chaperone-assisted folding of newly synthesized proteins in the cytosol. Crit.
Rev. Biochem. Mol. Biol. 39, 261–277.
Dobson C. M. (1999) Protein misfolding, evolution and
disease. Trends Biochem. Sci. 24, 329–332.
Dou F., Netzer W. J., Tanemura K., et al. (2003) Chaperones increase association of tau protein with microtubules. Proc. Natl. Acad. Sci. U. S. A. 100, 721–726.
Ellis R. J. (2001) Macromolecular crowding, obvious but
underappreciated. Trends Biochem. Sci. 26, 597–604.
Ferrington D. A., Husom A. D., and Thompson L. V. (2005)
Altered proteasome structure, function, and oxidation
in aged muscle. FASEB J. 19, 644–646.
Forman M. S., Schmidt M. L., Kasturi S., Perl D. P., Lee V. M.,
and Trojanowski J. Q. (2002) Tau and alpha-synuclein
pathology in amygdala of Parkinsonism-dementia
complex patients of Guam. Am. J. Pathol. 160, 1725–1731.
Gaczynska M., Osmulski P. A., and Ward W. F. (2001) Caretaker or undertaker? The role of the proteasome in
aging. Mech. Ageing Dev. 122, 235–254.
Gasparini L., Ongini E., and Wenk G. (2004) Non-steroidal
anti-inflammatory drugs (NSAIDs) in Alzheimer’s disease, old and new mechanisms of action. J. Neurochem.
91, 521–536.
Gelman M.S. and Kopito R. R. (2002) Rescuing protein
conformation: prospects for pharmacological therapy
in cystic fibrosis. J. Clin. Invest. 110, 1591–1597.
Ghani A. C., Donnelly C. A., Cox D. R., et al. (2005) Methods for estimating the case fatality ratio for a novel, emerging infectious disease. Am. J. Epidemiol. 162, 479–486.
Gidalevitz T., Ben-Zvi A., Ho K. H., Brignull H. R., and
Morimoto R. I. (2006) Progressive disruption of cellular protein folding in models of polyglutamine diseases. Science. 311, 1471–1474.
Goloubinoff P., Christeller J. T., Gatenby A. A., and Lorimer
G. H. (1989) Reconstitution of active dimeric ribulose
bisphosphate carboxylase from an unfolded state
depends on two chaperonin proteins and Mg-ATP.
Nature 342, 884–889.
Goloubinoff P., Mogk A., Zvi A. P., Tomoyasu T., and Bukau
B. (1999) Sequential mechanism of solubilization and
refolding of stable protein aggregates by a bichaperone
network. Proc. Natl. Acad. Sci. U. S. A. 96, 13,732–13,737.
Gozes I. and Brenneman D. E. (1996) Activity-dependent
neurotrophic factor (ADNF). An extracellular neuroprotective chaperonin? J. Mol. Neurosci. 7, 235–244.
Gozes I., Vulih I., Spivak-Pohis I., and Furman S. (2005)
Neuroendocrine aspects of the molecular chaperones
ADNF and ADNP, in Molecular Chaperones and Cell
Journal of Molecular Neuroscience
Hinault, Ben-Zvi, and Goloubinoff
Signalling (Hendeson B. and Pockley G., eds.). Cambridge
University Press, UK: pp. 251–262.
Hamilton R. L. and Bowser R. (2004) Alzheimer disease
pathology in amyotrophic lateral sclerosis. Acta
Neuropathol. (Berl) 107, 515–522.
Hargitai J., Lewis H., Boros I., et al. (2003) Bimoclomol, a
heat shock protein co-inducer, acts by the prolonged
activation of heat shock factor-1. Biochem. Biophys. Res.
Commun. 307, 689–695.
Hartl F. U. and Hayer-Hartl M. (2002) Molecular chaperones in the cytosol: from nascent chain to folded
protein. Science 295, 1852–1858.
Hay D. G., Sathasivam K., Tobaben S., et al. (2004) Progressive decrease in chaperone protein levels in a mouse
model of Huntington’s disease and induction of stress
proteins as a therapeutic approach. Hum. Mol. Genet.
13, 1389–1405.
Hayden M. R., Tyagi S. C., Kerklo M. M., and Nicolls M. R.
(2005) Type 2 diabetes mellitus as a conformational disease. JOP 6, 287–302.
Heiser V., Scherzinger E., Boeddrich A., et al. (2000) Inhibition of huntingtin fibrillogenesis by specific antibodies
and small molecules: implications for Huntington’s
disease therapy. Proc. Natl. Acad. Sci U. S. A. 97,
6739–6744.
Hercus M. J., Loeschcke V., and Rattan S. I. (2003) Lifespan
extension of Drosophila melanogaster through hormesis
by repeated mild heat stress. Biogerontology 4, 149–156.
Heydari A. R., You S., Takahashi R., Gutsmann-Conrad
A., Sarge K. D., and Richardson A. (2000) Age-related
alterations in the activation of heat shock transcription
factor 1 in rat hepatocytes. Exp. Cell. Res. 256, 83–93.
Holmberg C. I., Illman S. A., Kallio M., Mikhailov A., and
Sistonen L. (2000) Formation of nuclear HSF1 granules
varies depending on stress stimuli. Cell Stress Chaperones 3, 219–228.
Inden M., Kitamura Y., Kondo J., et al. (2005) Serofendic
acid prevents 6-hydroxydopamine-induced nigral neurodegeneration and drug-induced rotational asymmetry
in hemi-parkinsonian rats. J. Neurochem. 95, 950–961.
Jahn T. R. and Radford S. E. (2005) The Yin and Yang of
protein folding. FEBS J. 272, 5962–5970.
Jin T., Gu Y., Zanusso G., et al. (2000) The chaperone protein BiP binds to a mutant prion protein and mediates
its degradation by the proteasome. J. Biol. Chem. 275,
38,699-38,704.
Jones G. W. and Tuite M. F. (2005) Chaperoning prions:
the cellular machinery for propagating an infectious
protein? Bioessays 27, 823–832.
Jurivich D. A., Sistonen L., Kroes R. A., and Morimoto R. I.
(1992) Effect of sodium salicylate on the human heat
shock response. Science 255, 1243–1245.
Katsuno M., Sang C., Adachi H., et al. (2005) Pharmacological induction of heat-shock proteins alleviates
polyglutamine-mediated motor neuron disease. Proc.
Natl. Acad. Sci. U. S. A. 102, 16,801–16,806.
Khajavi M., Inoue K., Wiszniewski W., Ohyama T.,
Snipes G.J., and Lupski J.R. (2005) Curcumin treatment
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 263
Hsp Chaperones and Conformational Diseases
abrogates endoplasmic reticulum retention and aggregation induced apoptosis associated with neuropathycausing myelin protein zero-truncating mutants. Am.
J. Hum. Genet. 77, 841–850.
Kieran D., Kalmar B., Dick J. R., Riddoch-Contreras J.,
Burnstock G., and Greensmith L. (2004) Treatment with
arimoclomol, a coinducer of heat shock proteins, delays
disease progression in ALS mice. Nat. Med. 10, 402–405.
Kirkwood T. B. and Shanley D. P. (2005) Food restriction:
evolution and ageing. Mech. Ageing. Dev. 126, 1011–1016.
Klucken J., Shin Y., Masliah E., Hyman B. T., and McLean
P. J. (2004) Hsp70 Reduces alphaSynuclein Aggregation and Toxicity. J. Biol. Chem. 279, 25,497–25,502.
Kobayashi Y., Kume A., Li M., et al. (2000) Chaperones
Hsp70 and Hsp40 suppress aggregate formation and
apoptosis in cultured neuronal cells expressing truncated androgen receptor protein with expanded polyglutamine tract. J. Biol. Chem. 275, 8772–8778.
Kopito R. R. (2000) Aggresomes, inclusion bodies and protein aggregation. Trends. Cell. Biol. 10, 524–530.
Kregel K. C. (2002) Heat shock proteins: modifying factors in physiological stress responses and acquired thermotolerance. J. Appl. Physiol. 92, 2177–2186.
LaFerla F. M. and Oddo S. (2005) Alzheimer’s disease:
Abeta, tau and synaptic dysfunction. Trends. Mol. Med.
11, 170–176.
Landrigan P. J., Sonawane B., Butler R. N., Trasande L.,
Callan R., and Droller D. (2005) Early environmental
origins of neurodegenerative disease in later life.
Environ. Health. Perspect. 113, 1230-1233.
Lashuel H. A., Hartley D., Petre B. M., Walz T., and Lansbury P. T., Jr. (2002) Neurodegenerative disease: amyloid pores from pathogenic mutations. Nature 418, 291.
Laufen T., Mayer M. P., Beisel C., et al. (1999) Mechanism
of regulation of hsp70 chaperones by DnaJ cochaperones. Proc. Natl. Acad. Sci. U. S. A. 96, 5452–5457.
Lee A.S. (2001) The glucose-regulated proteins: stress
induction and clinical applications. Trends Biochem. Sci.
26, 504–510.
Lee Y. J. and Dewey W. C. (1987) Induction of heat shock
proteins in Chinese hamster ovary cells and development of thermotolerance by intermediate concentrations of puromycin. J. Cell. Physiol. 132, 1–11.
Li D., Sun F., and Wang K. (2004a) Protein profile of aging
and its retardation by caloric restriction in neural retina.
Biochem. Biophys. Res. Commun. 318, 253–258.
Li J., Zhu M., Rajamani S., Uversky V. N., and Fink A. L.
(2004b) Rifampicin inhibits alpha-synuclein fibrillation
and disaggregates fibrils. Chem. Biol. 11, 1513–1521.
Little E., Tocco G., Baudry M., Lee A. S., and Schreiber S. S.
(1996) Induction of glucose-regulated protein (glucoseregulated protein 78/BiP and glucose-regulated protein
94) and heat shock protein 70 transcripts in the
immature rat brain following status epilepticus. Neuroscience 75, 209–219.
Liu H., Bowes R.C., 3rd., van de Water B., Sillence C.,
Nagelkerke J. F., and Stevens J. L. (1997) Endoplasmic
reticulum chaperones GRP78 and calreticulin prevent
Journal of Molecular Neuroscience
263
oxidative stress, Ca2+ disturbances, and cell death in
renal epithelial cells. J. Biol. Chem. 272, 21,751–21,759.
Macario A. J. and Conway de Macario E. (2005) Sick chaperones, cellular stress, and disease. N. Engl. J. Med. 353,
1489–1501.
Magrane J., Smith R. C., Walsh K., and Querfurth H. W.
(2004) Heat shock protein 70 participates in the neuroprotective response to intracellularly expressed betaamyloid in neurons. J. Neurosci. 24, 1700–1706.
Manton K. G., Volovik S., and Kulminski A. (2004) ROS
effects on neurodegeneration in Alzheimer’s disease
and related disorders: on environmental stresses of
ionizing radiation. Curr. Alzheimer Res. 1, 277–293.
Marchetti B. and Abbracchio M. P. (2005) To be or not to
be (inflamed)—is that the question in anti-inflammatory
drug therapy of neurodegenerative disorders? Trends.
Pharmacol. Sci. 26, 517–525.
McLean P. J., Klucken J., Shin Y., and Hyman B. T. (2004)
Geldanamycin induces Hsp70 and prevents alphasynuclein aggregation and toxicity in vitro. Biochem.
Biophys. Res. Commun. 321, 665–669.
Miller V. M., Nelson R. F., Gouvion C. M., e tal. (2005)
CHIP suppresses polyglutamine aggregation and
toxicity in vitro and in vivo. J. Neurosci. 25, 9152–9161.
Mogk A., Deuerling E., Vorderwulbecke S., Vierling E.,
and Bukau B. (2003) Small heat shock proteins, ClpB
and the DnaK system form a functional triade in
reversing protein aggregation. Mol. Microbiol. 50,
585–595.
Mogk A., Tomoyasu T., Goloubinoff P., et al. (1999) Identification of thermolabile Escherichia coli proteins:
prevention and reversion of aggregation by DnaK and
ClpB. EMBO J. 18, 6934–6949.
Morgan C. J., Miranker A., and Dobson C. M. (1998) Characterization of collapsed states in the early stages of
the refolding of hen lysozyme. Biochemistry 37,
8473–8480.
Morrison J. P., Coleman M. C., Aunan E. S., Walsh S. A.,
Spitz D.R., and Kregel K.C. (2005) Aging reduces
responsiveness to BSO- and heat stress-induced perturbations of glutathione and antioxidant enzymes.
Am. J. Physiol. Regul. Integr. Comp. Physiol. 289,
1035–1041.
Moseley P. L. (1998) Heat shock proteins and the inflammatory response. Ann. NY Acad. Sci. 856, 206–213.
Muchowski P. J., Schaffar G., Sittler A., Wanker E. E., HayerHartl M. K., and Hartl F. U. (2000) Hsp70 and hsp40
chaperones can inhibit self-assembly of polyglutamine
proteins into amyloid-like fibrils. Proc. Natl. Acad. Sci.
U. S. A. 97, 7841–7846.
Muchowski P.J. and Wacker J. L. (2005) Modulation of
neurodegeneration by molecular chaperones. Nat. Rev.
Neurosci. 6, 11–22.
Neupert W. and Brunner M. (2002) The protein import
motor of mitochondria. Nat. Rev. Mol. Cell. Biol. 3,
555–565.
Niwa J., Ishigaki S., Hishikawa N., et al. (2002) Dorfin
ubiquitylates mutant SOD1 and prevents mutant
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 264
264
SOD1-mediated neurotoxicity. J. Biol. Chem. 277,
36,793–36,798.
Njemini R., Demanet C., and Mets T. (2004) Inflammatory
status as an important determinant of heat shock protein 70 serum concentrations during aging. Biogerontology 5, 31–38.
Nomoto M. and Nagai M. (2005) Proteasome function and
pathological proteins in the pathogenesis of Parkinson’s disease. J. Pharmacol. Sci. 97, 455–456.
Ohno K., Fukushima M., Fujiwara M., and Narumiya S.
(1988) Induction of 68,000-dalton heat shock proteins
by cyclopentenone prostaglandins. Its association with
prostaglandininduced G1 block in cell cycle progression. J. Biol. Chem. 263, 19,764–19,770.
Patel Y. J., Payne Smith M. D., de Belleroche J., and Latchman D.S. (2005) Hsp27 and Hsp70 administered in combination have a potent protective effect against
FALS-associated SOD1-mutant-induced cell death in
mammalian neuronal cells. Brain. Res. Mol. Brain. Res.
134, 256–274.
Petrucelli L., O’Farrell C., Lockhart P. J., et al. (2002) Parkin
protects against the toxicity associated with mutant
alpha-synuclein: proteasome dysfunction selectively
affects catecholaminergic neurons. Neuron 36, 1007–1019.
Plata-Salaman C. R., Peloso E., and Satinoff E. (1998)
Interleukin-1beta-induced fever in young and old
Long-Evans rats. Am. J. Physiol. 275, 1633–1638.
Prakash S. and Matouschek A. (2004) Protein unfolding
in the cell. Trends. Biochem. Sci. 29, 593–600.
Pratt W. B. and Toft D. O. (2003) Regulation of signaling
protein function and trafficking by the hsp90/hsp70based chaperone machinery. Exp. Biol. Med .(Maywood)
22, 111–133.
Prusiner S. B. (1989) Scrapie Prions. Annu Rev Microbiol.
43, 345-374.
Queitsch C., Sangster T. A., Lindquist S. (2002) Hsp90 as
a capacitor of phenotypic variation. Nature 417, 618–624.
Ran R., Lu A., Zhang L., et al. (2004) Hsp70 promotes TNFmediated apoptosis by binding IKK gamma and impairing NF-kappa B survival signaling. Genes. Dev. 18,
1466–1481.
Rattan S. I. (2004) Hormetic mechanisms of anti-aging and
rejuvenating effects of repeated mild heat stress on
human fibroblasts in vitro. Rejuvenation. Res. 7, 40–48.
Reddy R. K., Lu J., and Lee A. S. (1999) The endoplasmic
reticulum chaperone glycoprotein GRP94 with Ca(2+)binding and antiapoptotic properties is a novel proteolytic target of calpain during etoposide-induced
apoptosis. J. Biol. Chem. 274, 28,476–28,483.
Roth S., Willcox N., Rzepka R., Mayer M. P., and Melchers I. (2002) Major differences in antigen-processing
correlate with a single Arg71<—>Lys substitution in
HLA-DR molecules predisposing to rheumatoid arthritis and with their selective interactions with 70-kDa
heat shock protein chaperones. J. Immunol. 169,
3015–3020.
Saidi Y., Finka A., Chakhporanian M., Zryd J. P., Schaefer
D. G., and Goloubinoff P. (2005) Controlled expression
of recombinant proteins in Physcomitrella patens by a
Journal of Molecular Neuroscience
Hinault, Ben-Zvi, and Goloubinoff
conditional heat-shock promoter: a tool for plant
research and biotechnology. Plant. Mol. Biol. 59, 697–711.
Saleh A., Srinivasula S. M., Balkir L., Robbins P. D., and
Alnemri E.S. (2000) Negative regulation of the Apaf-1
apoptosome by Hsp70. Nat. Cell. Biol. 2, 476–483.
Satyal S. H., Schmidt E., Kitagawa K., et al. (2000) Polyglutamine aggregates alter protein folding homeostasis
in Caenorhabditis elegans. Proc. Natl. Acad. Sci. U. S. A.
97, 5750–5755.
Schick C., Arbogast M., Lowka K., Rzepka R., and Melchers I (2004) Continuous enhanced expression of Hsc70
but not Hsp70 in rheumatoid arthritis synovial tissue.
Arthritis Rheum. 50, 88–93.
Schiess M. (2003) Nonsteroidal anti-inflammatory drugs
protect against Parkinson neurodegeneration: can an
NSAID a day keep Parkinson disease away? Arch.
Neurol. 60, 1043–1044.
Selverstone Valentine J., Doucette P. A., and Zittin Potter
S. (2005) Copper-zinc superoxide dismutase and amyotrophic lateral sclerosis. Annu. Rev. Biochem. 74, 563–593.
Setsuie R., Kabuta T., and Wada K. (2005) Does proteosome inhibition decrease or accelerate toxin-induced
dopaminergic neurodegeneration? J. Pharmacol. Sci. 97,
457–460.
Shin Y., Klucken J., Patterson C., Hyman B. T., and McLean
P. J. (2005) The co-chaperone carboxyl terminus
of Hsp70-interacting protein (CHIP) mediates alphasynuclein degradation decisions between proteasomal
and lysosomal pathways. J. Biol. Chem. 280,
23,727–23,734.
Shinder G. A., Lacourse M. C., Minotti S., and Durham H. D.
(2001) Mutant Cu/Zn-superoxide dismutase proteins
have altered solubility and interact with heat
shock/stress proteins in models of amyotrophic lateral
sclerosis. J. Biol. Chem. 276, 12,791–12,796.
Soti C. and Csermely P. (2003) Aging and molecular chaperones. Exp. Gerontol. 38, 1037–1040.
Starnes J. W., Choilawala A. M., Taylor R. P., Nelson M. J.,
and Delp M.D. (2005) Myocardial heat shock protein
70 expression in young and old rats after identical
exercise programs. J. Gerontol. A. Biol. Sci. Med. Sci. 60,
963–969.
Stenoien D. L., Cummings C. J., Adams H. P., et al. (1999)
Polyglutamine-expanded androgen receptors form
aggregates that sequester heat shock proteins, proteasome components and SRC-1, and are suppressed by
the HDJ-2 chaperone. Hum. Mol. Genet. 8, 731–741.
Suzuki T. and Imai K. (1998) Evolution of myoglobin. Cell
Mol Life Sci. 54, 979–1004.
Suzuki S., Maruyama S., Sato W., et al. (2005) Geranylgeranylacetone ameliorates ischemic acute renal failure via induction of Hsp70. Kidney Int. 67, 2210–2220.
Tofaris G. K. and Spillantini M.G. (2005) Alpha-synuclein
dysfunction in Lewy Bodies diseaes. Mov. Disord. 20,
S37–S44.
Tomiyama T., Shoji A., Kataoka K., et al. (1996) Inhibition
of amyloid beta protein aggregation and neurotoxicity
by rifampicin. Its possible function as a hydroxyl
radical scavenger. J. Biol. Chem. 271, 6839–6844.
Volume 30, 2006
JMN06_0017_Goloubinoff
12/4/06
2:52 PM
Page 265
Hsp Chaperones and Conformational Diseases
Torok Z., Goloubinoff P., Horvath I., Tsvetkova N. M.,
et al. (2001) Synechocystis HSP17 is an amphitropic
protein that stabilizes heat-stressed membranes and
binds denatured proteins for subsequent chaperonemediated refolding. Proc. Natl. Acad. Sci. U. S. A. 98,
3098–3103.
Torok Z., Horvath I., Goloubinoff P., et al. (1997) Evidence
for a lipochaperonin: association of active protein-folding GroESL oligomers with lipids can stabilize membranes under heat shock conditions. Proc. Natl. Acad.
Sci. U.S.A. 94, 2192–2197.
Uchida S., Fujiki M., Nagai Y., Abe T., and Kobayashi H.
(2006) Geranylgeranylacetone, a noninvasive heat
shock protein inducer, induces protein kinase C and
leads to neuroprotection against cerebral infarction in
rats. Neurosci Lett., in press.
Uversky V. N. (2002) Cracking the folding code. Why do
some proteins adopt partially folded conformations,
whereas other don’t? FEBS. Lett. 514, 181–183.
Uversky V. N. (2003) Protein folding revisited. A polypeptide chain at the folding-misfoldingnonfolding crossroads: which way to go? Cell. Mol. Life. Sci. 60, 1852–1871.
Vacher C., Garcia-Oroz L., and Rubinsztein D. C. (2005)
Overexpression of yeast hsp 104 reduces polyglutamine aggregation and prolongs survival of a transgenic
mouse model of Huntington’s disease. Hum. Mol. Gen.
14, 3425–3433.
Vargas-Alarcon G., Londono J. D., Hernandez-Pacheco
G., et al. (2002) Heat shock protein 70 gene polymorphisms
in Mexican patients with spondyloarthropathies. Ann.
Rheum. Dis. 61, 48–51.
Veinger L., Diamant S., Buchner J., and Goloubinoff P.
(1998) The small heat-shock protein IbpB from
Escherichia coli stabilizes stress-denatured proteins for
subsequent refolding by a multichaperone network. J.
Biol. Chem. 273, 11,032–11,037.
Vigh L., Literati P. N., Horvath I., et al. (1997) Bimoclomol: a nontoxic, hydroxylamine derivative with stress
protein-inducing activity and cytoprotective effects.
Nat. Med. 3, 1150–1154.
Wang J., Gines S., MacDonald M. E., and Gusella J. F.
(2005a) Reversal of a full-length mutant huntingtin neuronal cell phenotype by chemical inhibitors of polyglutamine-mediated aggregation. BMC Neurosci. 6, 1.
Wang Q., Mosser D. D., and Bag J. (2005b) Induction of
HSP70 expression and recruitment of HSC70 and
HSP70 in the nucleus reduce aggregation of a polyalanine expansion mutant of PABPN1 in HeLa cells. Hum.
Mol. Genet. 14, 3673–3684.
Journal of Molecular Neuroscience
265
Wang X., Wang F., Sy M. S., and Ma J. (2005c) Calpain and
other cytosolic proteases can contribute to the degradation of retro-translocated prion protein in the cytosol.
J. Biol. Chem. 280, 317–325.
Weiss Y. G., Bouwman A., Gehan B., Schears G., Raj N.,
and Deutschman C.S. (2000) Cecal ligation and double
puncture impairs heat shock protein 70 (HSP70) expression in the lungs of rats. Shock. 13, 19–23.
Weiss Y. G., Maloyan A., Tazelaar J., Raj N., and
Deutschman C.S. (2002) Adenoviral transfer of HSP70 into pulmonary epithelium ameliorates experimental acute respiratory distress syndrome. J. Clin.
Invest. 110, 801–806.
Westerheide S. D., Bosman J. D., Mbadugha B. N., et al.
(2004) Celastrols as inducers of the heat shock response
and cytoprotection. J. Biol. Chem. 279, 56,053–56,060.
Westerheide S. D. and Morimoto R. I. (2005) Heat shock
response modulators as therapeutic tools for diseases
of protein conformation. J. Biol. Chem. 280, 33,097–
33,100.
Wyttenbach A., Carmichael J., Swartz J., et al. (2000) Effects
of heat shock, heat shock protein 40 (HDJ-2), and proteasome inhibition on protein aggregation in cellular
models of Huntington’s disease. Proc. Natl. Acad. Sci.
U. S. A. 97, 2898–2903.
Wyttenbach A., Sauvageot O., Carmichael J., et al. (2002)
Heat shock protein 27 prevents cellular polyglutamine
toxicity and suppresses the increase of reactive oxygen
species caused by huntingtin. Hum. Mol. Genet. 11,
1137–1151.
Yang F., Lim G. P., Begum A. N., et al. (2005) Curcumin
inhibits formation of amyloid beta oligomers and fibrils, binds plaques, and reduces amyloid in vivo. J. Biol.
Chem. 280, 5892–5901.
Zamostiano R., Pinhasov A., Bassan M., et al. (1999) A
femtomolar-acting neuroprotective peptide induces
increased levels of heat shock protein 60 in rat cortical
neurons: a potential neuroprotective mechanism.
Neurosci Lett. 264, 9–12.
Zhang Y., Champagne N., Beitel L. K., Goodyer C. G., Trifiro M., and LeBlanc A. (2004) Estrogen and androgen
protection of human neurons against intracellular
amyloid beta1-42 toxicity through heat shock protein
70. J. Neurosci. 24, 5315–5321.
Zourlidou A., Payne Smith M. D., and Latchman D. S.
(2004) HSP27 but not HSP70 has a potent protective
effect against alpha-synuclein-induced cell death
in mammalian neuronal cells. J. Neurochem. 88,
1439–1448.
Volume 30, 2006