The normal cellular prion protein (PrP) is a GPI-anchored, cell surface glycoprotein. But, in pan... more The normal cellular prion protein (PrP) is a GPI-anchored, cell surface glycoprotein. But, in pancreatic ductal adenocarcinoma cell (PDAC) lines, such as BxPC-3, PrP exists as a pro-PrP retaining its glycosylphosphatidylinositol (GPI) peptide signaling sequence (GPI-PSS). Here, we report the identification of another PDAC cell line, AsPC-1, which expresses a matured, GPI-anchored PrP. Comparison of the 24 genes involved in the GPI anchor modification pathway between AsPC-1 and BxPC-3 revealed 15 of the 24 genes, including PGAP1 and PIG-F were down regulated in the latter cells. We also identified 6 missense mutations in DPM2, PIG-C, PIG-N and PIG-P alongside 8 silent mutations. When BxPC-3 cells were fused with Chinese Hamster Ovary (CHO) cells, which lack endogenous PrP, pro-PrP was successfully converted into matured, GPI-anchored PrP. Expression of the individual gene, such as PGAP1, PIG-F, or PIG-C into BxPC-3 cells does not result in PI-PLC sensitivity of PrP. However, when PIG...
Prion diseases are not only genetic or sporadic neurodegenerative disorders, but more important, ... more Prion diseases are not only genetic or sporadic neurodegenerative disorders, but more important, they are transmissible diseases. The etiological agent in these unprecedented diseases is believed to be prion protein (PrP), which undergoes post-translational conversion from the predominant a-helical conformation known as PrP(C), to a b-sheet rich abnormal isoform called scrapie PrP (PrP(Sc)). Accumulating evidence has shown PrP(C) to be a copper-binding antioxidant in vivo. The prevailing view that PrP binds copper weakly is based on in vitro observations using peptides or short fragment of recombinant PrP. However, recent in vitro evidence indicates human PrP has significantly higher affinity for copper, similar to other copper-binding proteins and copper uptake experiments show that PrP expressed by cells has a Km in the nanomolar range. Besides binding copper within the octarepeats region along the N-terminus, PrP can also binds copper at a second site further upstream. More impor...
<p>(A) The level of blood HDL, LDL, TG and cholesterol in diabetics subjects with statin (n... more <p>(A) The level of blood HDL, LDL, TG and cholesterol in diabetics subjects with statin (n = 22, grey) and without statin (n = 18, white) treatment. (B) The level of blood glucose and insulin in diabetics subjects with statin (n = 22, grey) and without statin (n = 18, white) treatment. HOMA-IR values are computed with the measured blood glucose and insulin levels using the formula given in the methods section <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096874#pone.0096874-Matthews1" target="_blank">[19]</a>. Each value represents the mean ± SD of duplicate assays for individual samples. (*p = 0.011; **p = 0.026, using Student's t-test).</p
Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for sporadic Alzheimer's disea... more Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for sporadic Alzheimer's disease (AD), where inheritance of this isoform predisposes development of AD in a gene dose-dependent manner. Although the mode of action of ApoE4 on AD onset and progression remains unknown, we have previously shown that ApoE4, and not ApoE3 expression, resulted in insulin signaling deficits in the presence of amyloid beta (Aβ). However, these reports were not conducted with clinical samples that more accurately reflect human disease. In this study, we investigated the effect of ApoE genotype on the insulin signaling pathway in control and AD human brain samples. We found that targets of the insulin signaling pathway were attenuated in AD cases, regardless of ApoE isoform. We also found a decrease in GluR1 subunit expression, and an increase NR2B subunit expression in AD cases, regardless of ApoE isoform. Lastly, we observed that more insulin receptor (IR) was immunoprecipitated in control ...
Neuroinflammation and cerebrovascular disease (CeVD) have been implicated in cognitive impairment... more Neuroinflammation and cerebrovascular disease (CeVD) have been implicated in cognitive impairment and Alzheimer's disease (AD). The present study aimed to examine serum inflammatory markers in preclinical stages of dementia and in AD, as well as to investigate their associations with concomitant CeVD. We performed a cross-sectional case-control study including 96 AD, 140 cognitively impaired no dementia (CIND), and 79 noncognitively impaired participants. All subjects underwent neuropsychological and neuroimaging assessments, as well as collection of blood samples for measurements of serum samples interleukin (IL)-6, IL-8, and tumor necrosis factor α levels. Subjects were classified as CIND or dementia based on clinical criteria. Significant CeVD, including white-matter hyperintensities (WMHs), lacunes, and cortical infarcts, was assessed by magnetic resonance imaging. After controlling for covariates, higher concentrations of IL-8, but not the other measured cytokines, were ass...
It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease ... more It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neu...
Introduction Genetic polymorphisms modulate the function of human apolipoprotein E and disease su... more Introduction Genetic polymorphisms modulate the function of human apolipoprotein E and disease susceptibility. Inheriting the apolipoprotein E4 allele is linked to higher peripheral cholesterol levels and increased risk for atherosclerosis. This gene allele is also a major genetic risk factor for Alzheimer’s disease, but it is unclear how harbouring the apolipoprotein E4 allele causes earlier disease manifestation. This is because little is known about the function of human apolipoprotein E in the brain. While intranasal insulin can improve cognition, this has little effect on apolipoprotein E4 non-demented elderly subjects. These subjects are also found to have lower cerebral glucose metabolic rate. This critical review discusses the neuronal functions of human apolipoprotein E. Conclusion Put together, this suggests that apolipoprotein E isoforms could modulate brain metabolism. In this article, we have discussed a possible role for apolipoprotein E in regulating brain insulin sig...
The normal cellular prion protein (PrP) is a GPI-anchored, cell surface glycoprotein. But, in pan... more The normal cellular prion protein (PrP) is a GPI-anchored, cell surface glycoprotein. But, in pancreatic ductal adenocarcinoma cell (PDAC) lines, such as BxPC-3, PrP exists as a pro-PrP retaining its glycosylphosphatidylinositol (GPI) peptide signaling sequence (GPI-PSS). Here, we report the identification of another PDAC cell line, AsPC-1, which expresses a matured, GPI-anchored PrP. Comparison of the 24 genes involved in the GPI anchor modification pathway between AsPC-1 and BxPC-3 revealed 15 of the 24 genes, including PGAP1 and PIG-F were down regulated in the latter cells. We also identified 6 missense mutations in DPM2, PIG-C, PIG-N and PIG-P alongside 8 silent mutations. When BxPC-3 cells were fused with Chinese Hamster Ovary (CHO) cells, which lack endogenous PrP, pro-PrP was successfully converted into matured, GPI-anchored PrP. Expression of the individual gene, such as PGAP1, PIG-F, or PIG-C into BxPC-3 cells does not result in PI-PLC sensitivity of PrP. However, when PIG...
Prion diseases are not only genetic or sporadic neurodegenerative disorders, but more important, ... more Prion diseases are not only genetic or sporadic neurodegenerative disorders, but more important, they are transmissible diseases. The etiological agent in these unprecedented diseases is believed to be prion protein (PrP), which undergoes post-translational conversion from the predominant a-helical conformation known as PrP(C), to a b-sheet rich abnormal isoform called scrapie PrP (PrP(Sc)). Accumulating evidence has shown PrP(C) to be a copper-binding antioxidant in vivo. The prevailing view that PrP binds copper weakly is based on in vitro observations using peptides or short fragment of recombinant PrP. However, recent in vitro evidence indicates human PrP has significantly higher affinity for copper, similar to other copper-binding proteins and copper uptake experiments show that PrP expressed by cells has a Km in the nanomolar range. Besides binding copper within the octarepeats region along the N-terminus, PrP can also binds copper at a second site further upstream. More impor...
<p>(A) The level of blood HDL, LDL, TG and cholesterol in diabetics subjects with statin (n... more <p>(A) The level of blood HDL, LDL, TG and cholesterol in diabetics subjects with statin (n = 22, grey) and without statin (n = 18, white) treatment. (B) The level of blood glucose and insulin in diabetics subjects with statin (n = 22, grey) and without statin (n = 18, white) treatment. HOMA-IR values are computed with the measured blood glucose and insulin levels using the formula given in the methods section <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096874#pone.0096874-Matthews1" target="_blank">[19]</a>. Each value represents the mean ± SD of duplicate assays for individual samples. (*p = 0.011; **p = 0.026, using Student's t-test).</p
Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for sporadic Alzheimer's disea... more Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for sporadic Alzheimer's disease (AD), where inheritance of this isoform predisposes development of AD in a gene dose-dependent manner. Although the mode of action of ApoE4 on AD onset and progression remains unknown, we have previously shown that ApoE4, and not ApoE3 expression, resulted in insulin signaling deficits in the presence of amyloid beta (Aβ). However, these reports were not conducted with clinical samples that more accurately reflect human disease. In this study, we investigated the effect of ApoE genotype on the insulin signaling pathway in control and AD human brain samples. We found that targets of the insulin signaling pathway were attenuated in AD cases, regardless of ApoE isoform. We also found a decrease in GluR1 subunit expression, and an increase NR2B subunit expression in AD cases, regardless of ApoE isoform. Lastly, we observed that more insulin receptor (IR) was immunoprecipitated in control ...
Neuroinflammation and cerebrovascular disease (CeVD) have been implicated in cognitive impairment... more Neuroinflammation and cerebrovascular disease (CeVD) have been implicated in cognitive impairment and Alzheimer's disease (AD). The present study aimed to examine serum inflammatory markers in preclinical stages of dementia and in AD, as well as to investigate their associations with concomitant CeVD. We performed a cross-sectional case-control study including 96 AD, 140 cognitively impaired no dementia (CIND), and 79 noncognitively impaired participants. All subjects underwent neuropsychological and neuroimaging assessments, as well as collection of blood samples for measurements of serum samples interleukin (IL)-6, IL-8, and tumor necrosis factor α levels. Subjects were classified as CIND or dementia based on clinical criteria. Significant CeVD, including white-matter hyperintensities (WMHs), lacunes, and cortical infarcts, was assessed by magnetic resonance imaging. After controlling for covariates, higher concentrations of IL-8, but not the other measured cytokines, were ass...
It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease ... more It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neu...
Introduction Genetic polymorphisms modulate the function of human apolipoprotein E and disease su... more Introduction Genetic polymorphisms modulate the function of human apolipoprotein E and disease susceptibility. Inheriting the apolipoprotein E4 allele is linked to higher peripheral cholesterol levels and increased risk for atherosclerosis. This gene allele is also a major genetic risk factor for Alzheimer’s disease, but it is unclear how harbouring the apolipoprotein E4 allele causes earlier disease manifestation. This is because little is known about the function of human apolipoprotein E in the brain. While intranasal insulin can improve cognition, this has little effect on apolipoprotein E4 non-demented elderly subjects. These subjects are also found to have lower cerebral glucose metabolic rate. This critical review discusses the neuronal functions of human apolipoprotein E. Conclusion Put together, this suggests that apolipoprotein E isoforms could modulate brain metabolism. In this article, we have discussed a possible role for apolipoprotein E in regulating brain insulin sig...
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