chieko itakura

<p>(A) Specificity of the two independently generated anti-PfAtg8 antibodies (#1 and #2). Crude antisera and purified antibodies were used for immunoblotting of lysates of asynchronized <i>P. falciparum</i> parasites. (B) Expression of PfAtg8 increases during the erythrocytic stage of development. Highly synchronized <i>P. falciparum</i> parasites were collected at 0, 12, 24, 32, and 40 h after invasion. The duration of one cycle of the erythrocyte stage was approximately 42 h. Expression levels of PfAtg8 were analyzed by immunoblotting. An antibody against HSP70 was used as a loading control. (C) PfAtg8 exogenously expressed in mammalian cells (lane 1), endogenous PfAtg8 expressed in <i>P. falciparum</i> (lane 2), and the mixture of these two samples were subjected to immunoblot analysis using anti-PfAtg8 antibody. (D) Lysates of asynchronized <i>Plasmodium</i> were separated into low-speed (13,000×<i>g</i>) pellet (LSP), high-speed (100,000×<i>g</i>) pellet (HSP), and high-speed supernatant (HSS) fractions, and analyzed by immunoblotting using anti-PfAtg8 antibody. (E) The LSP fraction prepared in (D) was treated with 2 M urea or 2% Triton-X 100 and separated into 100,000×<i>g</i> pellet (P) and supernatant (S). (F) Infected erythrocytes were cultured in the presence of the indicated concentration of chloroquine and expression of PfAtg8 was analyzed.</p

Adaptive changes in lysosomal capacity are driven by the transcription factors TFEB and TFE3 in response to increased autophagic flux and endolysosomal stress, yet the molecular details of their activation are unclear. LC3 and GABARAP members of the ATG8 protein family are required for selective autophagy and sensing perturbation within the endolysosomal system. Here we show that during single membrane ATG8 conjugation (SMAC), Parkin-dependent mitophagy, and Salmonella-induced xenophagy, the membrane conjugation of GABARAP, but not LC3, is required for activation of TFEB/TFE3 to control lysosomal homeostasis and capacity. GABARAP directly binds to a novel LC3-interacting motif (LIR) in the FLCN/FNIP tumor suppressor complex with picomolar affinity and regulates its relocalization to these GABARAP-conjugated membrane compartments. This disrupts the regulation of RagC/D by the FLCN/FNIP GAP complex, resulting in impaired mTOR-dependent phosphorylation of TFEB without changing mTOR act...

<p>(A) <i>P. falciparum</i> FCR3 parasites at the schizont stage were analyzed by immunoelectron microscopy (immunogold and silver enhancement method) with an antibody against PfAtg8 (#1). (a) A schizont in an erythrocyte. (b) A magnified image of the area indicated in (a). (c) Another typical image of a PfAtg8-positive structure. (B) <i>P. falciparum</i> transfectant expressing ACP-GFP was analyzed as in panel (A) with an antibody against GFP. A, apicoplast; Mt, mitochondrion. Scale bars, (A, a) 1 μm, (A, b and c, and B) 200 nm.</p

<p><i>P. falciparum</i> FCR3 (A–E) and <i>P. falciparum</i> 3D7 transfected with ACP-GFP (F–H) were stained with the indicated organelle markers and visualized by confocal microscopy (because ACP-GFP was not uniformly expressed, some merozoites displayed only faint GFP signals). Anti-PfAtg8 antibody #1 was used in (A–F), and anti-PfAtg8 antibody #2 was used in (G). Apical membrane antigen 1 (AMA1) as a microneme marker (A), rhoptry-associated protein 1 (RAP1) as a rhoptry body marker (B), rhoptry neck protein 2 (RON2) as a rhoptry neck marker (C), the ring-infected erythrocyte surface antigen (RESA) as a dense granule marker (D), MitoTrackerRed CMXRos as a mitochondria marker (E), ACP-GFP (F–H) and the organellar histone-like protein PfHU (H) as an apicoplast marker were used. Scale bar, 1 μm.</p

Myosins of class VI are unique actin based motor proteins that move cargo towards the minus ends of actin filaments. This motor interacts with a wide variety of adaptor proteins, which regulate cargo attachment and thus mediate the very specific intracellular functions of myosin VI in the endocytic and exocytic membrane trafficking pathways. These adaptor proteins may also act as molecular switches to regulate the on/off state of myosin VI. Our new data shows that myosin VI, in concert with its adaptor proteins optineurin, NDP52, T6BP and Tom1 plays a crucial role in autophagy, a degradative pathway that the cell uses to clear pathogens, damaged organelles and protein aggregates. The ESCRT-0 protein Tom1 is a novel myosin VI adaptor protein in mammalian cells that is involved in targeting of myosin VI to early endosomes. The loss of either myosin VI or Tom1 reduces delivery of endocytic cargo to autophagosomes, thereby preventing autophagosome maturation and autophagosome-lysosome f...

Mitochondrial quality control is essential to maintain cellular homeostasis and is achieved by removing damaged, ubiquitinated mitochondria via Parkin-mediated mitophagy. Here, we demonstrate that MYO6 (myosin VI), a unique myosin that moves toward the minus end of actin filaments, forms a complex with Parkin and is selectively recruited to damaged mitochondria via its ubiquitin-binding domain. This myosin motor initiates the assembly of F-actin cages to encapsulate damaged mitochondria by forming a physical barrier that prevents refusion with neighboring populations. Loss of MYO6 results in an accumulation of mitophagosomes and an increase in mitochondrial mass. In addition, we observe downstream mitochondrial dysfunction manifesting as reduced respiratory capacity and decreased ability to rely on oxidative phosphorylation for energy production. Our work uncovers a crucial step in mitochondrial quality control: the formation of MYO6-dependent actin cages that ensure isolation of da...

In this chapter we describe the use of correlative light-electron microscopy (CLEM) to study, in cultured cells, the turnover of damaged mitochondria by PINK1/Parkin-dependent mitophagy. CLEM combines the advantages of light microscopy, which allows to image and rapidly screen a large number of the cells, while electron microscopy provides high-resolution imaging of these selected cells and a detailed structural analysis of their cellular organelles. We describe in detail how to prepare the cell cultures for optimum preservation of their cellular ultrastructure for CLEM using the most suitable buffers, fixatives, and embedding resins. These protocols are applicable for detailed ultrastructural analysis in a wide variety of organisms and cells, ranging from prokaryotic bacteria to mammalian cells.

Autophagy is mediated by a unique organelle, the autophagosome. Autophagosome formation involves a number of autophagy-related (ATG) proteins and complicated membrane dynamics. Although the hierarchical relationships of ATG proteins have been investigated, how individual ATG proteins or their complexes contribute to the organization of the autophagic membrane remains largely unknown. Here, systematic ultrastructural analysis of mouse embryonic fibroblasts (MEFs) and HeLa cells deficient in various ATG proteins reveals that the emergence of the isolation membrane (phagophore) requires FIP200 (also known as RB1CC1), ATG9A and phosphatidylinositol (PtdIns) 3-kinase activity. By contrast, small premature isolation-membrane-like and autophagosome-like structures were generated in cells lacking VMP1 and both ATG2A and ATG2B, respectively. The isolation membranes could elongate in cells lacking ATG5, but did not mature into autophagosomes. We also found that ferritin clusters accumulated a...

Mitochondria can be degraded by autophagy; this process is termed mitophagy. The Parkinson disease-associated ubiquitin ligase Parkin can trigger mitophagy of depolarized mitochondria. However, how the autophagy machinery is involved in this specific type of autophagy remains to be determined. It has been speculated that adaptor proteins such as p62 may mediate interaction between the autophagosomal LC3 family of proteins and ubiquitinated protein on mitochondria. Here, we describe our systematic analysis of the recruitment of Atg proteins in Parkin-dependent mitophagy. Structures containing upstream Atg proteins, including ULK1, Atg14, DFCP1, WIPI-1, and Atg16L1, can associate with depolarized mitochondria even in the absence of membrane-bound LC3. Atg9A structures are also recruited to these damaged mitochondria as well as the autophagosome formation site during starvation-induced canonical autophagy. At initial steps of Parkin-mediated mitophagy, the structures containing the ULK...