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Scientific Reports Mar 2016CLEC16A is in a locus genetically linked to autoimmune diseases including multiple sclerosis, but the function of this gene in the nervous system is unknown. Here we...
CLEC16A is in a locus genetically linked to autoimmune diseases including multiple sclerosis, but the function of this gene in the nervous system is unknown. Here we show that two mouse strains carrying independent Clec16a mutations developed neurodegenerative disease characterized by motor impairments and loss of Purkinje cells. Neurons from Clec16a-mutant mice exhibited increased expression of the autophagy substrate p62, accumulation of abnormal intra-axonal membranous structures bearing the autophagy protein LC3, and abnormal Golgi morphology. Multiple aspects of endocytosis, lysosome and Golgi function were normal in Clec16a-deficient murine embryonic fibroblasts and HeLa cells. However, these cells displayed abnormal bulk autophagy despite unimpaired autophagosome formation. Cultured Clec16a-deficient cells exhibited a striking accumulation of LC3 and LAMP-1 positive autolysosomes containing undigested cytoplasmic contents. Therefore Clec16a, an autophagy protein that is critical for autolysosome function and clearance, is required for Purkinje cell survival.
Topics: Animals; Autophagy; Cell Survival; Cells, Cultured; Golgi Apparatus; HeLa Cells; Humans; Lectins, C-Type; Lysosomes; Mice; Monosaccharide Transport Proteins; Motor Neuron Disease; Mutation; Purkinje Cells
PubMed: 26987296
DOI: 10.1038/srep23326 -
Trends in Biochemical Sciences Nov 2020Lysosomes transcend the role of degradation stations, acting as key nodes for interorganelle crosstalk and signal transduction. Lysosomes communicate with the nucleus... (Review)
Review
Lysosomes transcend the role of degradation stations, acting as key nodes for interorganelle crosstalk and signal transduction. Lysosomes communicate with the nucleus through physical proximity and functional interaction. In response to external and internal stimuli, lysosomes actively adjust their distribution between peripheral and perinuclear regions and modulate lysosome-nucleus signaling pathways; in turn, the nucleus fine-tunes lysosomal biogenesis and functions through transcriptional controls. Changes in coordination between these two essential organelles are associated with metabolic disorders, neurodegenerative diseases, and aging. In this review, we address recent advances in lysosome-nucleus communication by multi-tiered regulatory mechanisms and discuss how these regulations couple metabolic inputs with organellar motility, cellular signaling, and transcriptional network.
Topics: Animals; Cell Nucleus; Gene Regulatory Networks; Humans; Lysosomes; Signal Transduction
PubMed: 32624271
DOI: 10.1016/j.tibs.2020.06.004 -
Traffic (Copenhagen, Denmark) Jun 2017Autophagic lysosome reformation (ALR) is the terminal step of autophagy and is essential for maintaining lysosome homeostasis during autophagy. During ALR, tubules are... (Review)
Review
Autophagic lysosome reformation (ALR) is the terminal step of autophagy and is essential for maintaining lysosome homeostasis during autophagy. During ALR, tubules are extruded from autolysosomes, and small vesicles named proto-lysosomes, which are composed of lysosomal membrane components, are generated from these tubules. Eventually, proto-lysosomes mature into functional lysosomes. In this review, we will summarize recent progress in understanding the regulation, mechanisms and physiological functions of ALR.
Topics: Animals; Autophagy; Cell Membrane; Clathrin; Homeostasis; Humans; Lysosomes; TOR Serine-Threonine Kinases
PubMed: 28371052
DOI: 10.1111/tra.12484 -
EMBO Reports Sep 2014Autophagosome formation is promoted by the PI3 kinase complex and negatively regulated by myotubularin phosphatases, indicating that regulation of local...
Autophagosome formation is promoted by the PI3 kinase complex and negatively regulated by myotubularin phosphatases, indicating that regulation of local phosphatidylinositol 3-phosphate (PtdIns3P) levels is important for this early phase of autophagy. Here, we show that the Caenorhabditis elegans myotubularin phosphatase MTM-3 catalyzes PtdIns3P turnover late in autophagy. MTM-3 acts downstream of the ATG-2/EPG-6 complex and upstream of EPG-5 to promote autophagosome maturation into autolysosomes. MTM-3 is recruited to autophagosomes by PtdIns3P, and loss of MTM-3 causes increased autophagic association of ATG-18 in a PtdIns3P-dependent manner. Our data reveal critical roles of PtdIns3P turnover in autophagosome maturation and/or autolysosome formation.
Topics: Animals; Autophagy; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Lysosomes; Phagosomes; Phosphatidylinositol 3-Kinases; Phosphatidylinositol Phosphates; Phosphoric Monoester Hydrolases; Protein Tyrosine Phosphatases, Non-Receptor
PubMed: 25124690
DOI: 10.15252/embr.201438618 -
Autophagy May 2024MCOLN1 and MCOLN3 are two Ca release channels residing in the endolysosomal membrane. They are activated by phosphatidylinositol (PtdIns)-3-phosphate (PtdIns3P) and/or... (Review)
Review
MCOLN1 and MCOLN3 are two Ca release channels residing in the endolysosomal membrane. They are activated by phosphatidylinositol (PtdIns)-3-phosphate (PtdIns3P) and/or PtdIns(3,5)P. Their activities are also regulated by lumenal pH, with low pH enhancing that of MCOLN1 and high pH increasing that of MCOLN3. Recent studies further suggest that upon starvation, both MCOLN1 and MCOLN3 are activated by a reduction in MTORC1 activity; their activation in turn regulates MTORC1 activity to facilitate macroautophagic/autophagic flux. On the one hand, MCOLN3 appears to be recruited to phagophores where it is activated by PtdIns3P and high pH to inhibit MTORC1 activity using a positive feedback mechanism, thereby increasing autophagy induction. On the other hand, MCOLN1 is activated by PtdIns(3,5)P and low pH in (auto)lysosomes to increase MTORC1 activity using a negative feedback mechanism, promoting autophagic lysosome reformation. The cell uses the two feedback mechanisms to ensure efficient autophagic flux to survive adverse conditions such as nutrient deprivation and bacterial infection.
Topics: Mechanistic Target of Rapamycin Complex 1; Autophagy; Humans; Animals; Transient Receptor Potential Channels; Lysosomes; Models, Biological
PubMed: 38180017
DOI: 10.1080/15548627.2023.2300922 -
The Journal of Cell Biology Jun 2023During oxidative stress neurons release lipids that are internalized by glia. Defects in this coordinated process play an important role in several neurodegenerative...
During oxidative stress neurons release lipids that are internalized by glia. Defects in this coordinated process play an important role in several neurodegenerative diseases. Yet, the mechanisms of lipid release and its consequences on neuronal health are unclear. Here, we demonstrate that lipid-protein particle release by autolysosome exocytosis protects neurons from ferroptosis, a form of cell death driven by lipid peroxidation. We show that during oxidative stress, peroxidated lipids and iron are released from neurons by autolysosomal exocytosis which requires the exocytic machinery VAMP7 and syntaxin 4. We observe membrane-bound lipid-protein particles by TEM and demonstrate that these particles are released from neurons using cryoEM. Failure to release these lipid-protein particles causes lipid hydroperoxide and iron accumulation and sensitizes neurons to ferroptosis. Our results reveal how neurons protect themselves from peroxidated lipids. Given the number of brain pathologies that involve ferroptosis, defects in this pathway likely play a key role in the pathophysiology of neurodegenerative disease.
Topics: Humans; Ferroptosis; Iron; Lipid Peroxidation; Lipid Peroxides; Neurodegenerative Diseases; Neurons; Exocytosis; Lysosomes
PubMed: 37036445
DOI: 10.1083/jcb.202207130 -
Autophagy Nov 2016Autophagy is considered primarily a cell survival process, although it can also lead to cell death. However, the factors that dictate the shift between these 2 opposite...
Autophagy is considered primarily a cell survival process, although it can also lead to cell death. However, the factors that dictate the shift between these 2 opposite outcomes remain largely unknown. In this work, we used Δ-tetrahydrocannabinol (THC, the main active component of marijuana, a compound that triggers autophagy-mediated cancer cell death) and nutrient deprivation (an autophagic stimulus that triggers cytoprotective autophagy) to investigate the precise molecular mechanisms responsible for the activation of cytotoxic autophagy in cancer cells. By using a wide array of experimental approaches we show that THC (but not nutrient deprivation) increases the dihydroceramide:ceramide ratio in the endoplasmic reticulum of glioma cells, and this alteration is directed to autophagosomes and autolysosomes to promote lysosomal membrane permeabilization, cathepsin release and the subsequent activation of apoptotic cell death. These findings pave the way to clarify the regulatory mechanisms that determine the selective activation of autophagy-mediated cancer cell death.
Topics: Apoptosis; Autophagy; Biological Transport; Cell Line, Tumor; Cell Proliferation; Ceramides; Dronabinol; Endoplasmic Reticulum; Golgi Apparatus; Humans; Intracellular Membranes; Lysosomes; Models, Biological; Neoplasms; Permeability; Phagosomes; Sphingolipids
PubMed: 27635674
DOI: 10.1080/15548627.2016.1213927 -
Trends in Biochemical Sciences Apr 2020
Review
Topics: Animals; Chlorides; Humans; Hydrogen-Ion Concentration; Lysosomes
PubMed: 32169175
DOI: 10.1016/j.tibs.2019.12.006 -
EXS 1996Structural and functional features of plant lysozymes are reviewed. All lysozymes also have chitinase activity, but not all plant chitinases are also lysozymes. However,... (Review)
Review
Structural and functional features of plant lysozymes are reviewed. All lysozymes also have chitinase activity, but not all plant chitinases are also lysozymes. However, for many chitinases it is not yet known if they also possess lysozyme activity. Enzymes with lysozyme activity occur in different, structurally unrelated, families of chitinases. Plant chitinases with lysozyme activity are basic enzymes with high isoionic points. Their lysozyme activities have a shart pH optimum around pH 4.5-5.0, while they show chitinase activities in a much broader pH range. High lysozyme activities are observed at low ionic strength values (0.05). The X-ray structure of a lysozyme/chitinase from latex of the rubber tree, Hevea brasiliensis, is presented. This enzyme is also known under the name hevamine. It belongs to the family 18 or h-type chitinases (also called class III chitinases). The structure consists of an alpha/beta barrel fold, which has not been found in other chitinase or lysozyme structures. A glutamic acid residue may be catalytically active in the substrate-binding cleft of the enzyme. Other plant lysozymes are homologous with the family 19 or b-type chitinases (class I, II and IV). The X-ray structure of barley chitinase, a representative of this family with negligible lysozyme activity, has a similar folding as found in animal and phage lysozymes.
Topics: Amino Acid Sequence; Binding Sites; Chitinases; Hydrogen-Ion Concentration; Lysosomes; Models, Molecular; Molecular Sequence Data; Plants; Protein Conformation; Sequence Homology, Amino Acid
PubMed: 8765295
DOI: 10.1007/978-3-0348-9225-4_5 -
Viruses Jul 2017Viruses have evolved unique strategies to evade or subvert autophagy machinery. Enterovirus A71 (EV-A71) induces autophagy during infection in vitro and in vivo. In this...
Viruses have evolved unique strategies to evade or subvert autophagy machinery. Enterovirus A71 (EV-A71) induces autophagy during infection in vitro and in vivo. In this study, we report that EV-A71 triggers autolysosome formation during infection in human rhabdomyosarcoma (RD) cells to facilitate its replication. Blocking autophagosome-lysosome fusion with chloroquine inhibited virus RNA replication, resulting in lower viral titres, viral RNA copies and viral proteins. Overexpression of the non-structural protein 2BC of EV-A71 induced autolysosome formation. Yeast 2-hybrid and co-affinity purification assays showed that 2BC physically and specifically interacted with a -ethylmaleimide-sensitive factor attachment receptor (SNARE) protein, syntaxin-17 (STX17). Co-immunoprecipitation assay further showed that 2BC binds to SNARE proteins, STX17 and synaptosome associated protein 29 (SNAP29). Transient knockdown of STX17, SNAP29, and microtubule-associated protein 1 light chain 3B (LC3B), crucial proteins in the fusion between autophagosomes and lysosomes) as well as the lysosomal-associated membrane protein 1 (LAMP1) impaired production of infectious EV-A71 in RD cells. Collectively, these results demonstrate that the generation of autolysosomes triggered by the 2BC non-structural protein is important for EV-A71 replication, revealing a potential molecular pathway targeted by the virus to exploit autophagy. This study opens the possibility for the development of novel antivirals that specifically target 2BC to inhibit formation of autolysosomes during EV-A71 infection.
Topics: Cell Line, Tumor; Enterovirus A, Human; Host-Pathogen Interactions; Humans; Immunoprecipitation; Lysosomal Membrane Proteins; Lysosomes; Microtubule-Associated Proteins; Protein Binding; Protein Interaction Mapping; Qa-SNARE Proteins; Qb-SNARE Proteins; Qc-SNARE Proteins; Two-Hybrid System Techniques; Viral Nonstructural Proteins; Virus Replication
PubMed: 28677644
DOI: 10.3390/v9070169