Abstract
Mutations in the human autophagy gene EPG5 cause the multisystem disorder Vici syndrome. Here we demonstrated that EPG5 is a Rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. EPG5 is recruited to late endosomes/lysosomes by direct interaction with Rab7 and the late endosomal/lysosomal R-SNARE VAMP7/8. EPG5 also binds to LC3/LGG-1 (mammalian and C. elegans Atg8 homolog, respectively) and to assembled STX17-SNAP29 Qabc SNARE complexes on autophagosomes. EPG5 stabilizes and facilitates the assembly of STX17-SNAP29-VAMP7/8 trans-SNARE complexes, and promotes STX17-SNAP29-VAMP7-mediated fusion of reconstituted proteoliposomes. Loss of EPG5 activity causes abnormal fusion of autophagosomes with various endocytic vesicles, in part due to elevated assembly of STX17-SNAP25-VAMP8 complexes. SNAP25 knockdown partially suppresses the autophagy defect caused by EPG5 depletion. Our study reveals that EPG5 is a Rab7 effector involved in autophagosome maturation, providing insight into the molecular mechanism underlying Vici syndrome.
Keywords:
LC3; RAB effector; SNARE; autophagosome maturation; epg-5.
Copyright © 2016 Elsevier Inc. All rights reserved.
MeSH terms
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Agenesis of Corpus Callosum / genetics*
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Agenesis of Corpus Callosum / metabolism
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Agenesis of Corpus Callosum / pathology
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Amino Acid Sequence
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Animals
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Autophagosomes / metabolism*
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Autophagosomes / ultrastructure
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Autophagy / genetics
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Autophagy-Related Proteins
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Caenorhabditis elegans / genetics
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Caenorhabditis elegans / metabolism
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Caenorhabditis elegans Proteins / genetics
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Caenorhabditis elegans Proteins / metabolism
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Cataract / genetics*
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Cataract / metabolism
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Cataract / pathology
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Endosomes / metabolism*
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Endosomes / ultrastructure
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Gene Expression Regulation
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HeLa Cells
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Humans
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Lysosomal Membrane Proteins
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Lysosomes / metabolism*
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Lysosomes / ultrastructure
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Membrane Fusion
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Microtubule-Associated Proteins / genetics
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Microtubule-Associated Proteins / metabolism
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Protein Binding
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Proteins / genetics*
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Proteins / metabolism
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Qa-SNARE Proteins / genetics
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Qa-SNARE Proteins / metabolism
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Qb-SNARE Proteins / genetics
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Qb-SNARE Proteins / metabolism
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Qc-SNARE Proteins / genetics
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Qc-SNARE Proteins / metabolism
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R-SNARE Proteins / genetics
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R-SNARE Proteins / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Signal Transduction
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Synaptosomal-Associated Protein 25 / genetics
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Synaptosomal-Associated Protein 25 / metabolism
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Vesicular Transport Proteins
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rab GTP-Binding Proteins / genetics*
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rab GTP-Binding Proteins / metabolism
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rab7 GTP-Binding Proteins
Substances
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Autophagy-Related Proteins
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Caenorhabditis elegans Proteins
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EPG5 protein, human
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LGG-1 protein, C elegans
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Lysosomal Membrane Proteins
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MAP1LC3A protein, human
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Microtubule-Associated Proteins
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Proteins
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Qa-SNARE Proteins
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Qb-SNARE Proteins
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Qc-SNARE Proteins
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R-SNARE Proteins
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SNAP25 protein, human
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SNAP29 protein, human
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STX17 protein, human
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Synaptosomal-Associated Protein 25
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VAMP7 protein, human
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VAMP8 protein, human
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Vesicular Transport Proteins
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rab7 GTP-Binding Proteins
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rab7 GTP-binding proteins, human
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rab GTP-Binding Proteins
Supplementary concepts
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Absent corpus callosum cataract immunodeficiency