The ER-Localized Transmembrane Protein EPG-3/VMP1 Regulates SERCA Activity to Control ER-Isolation Membrane Contacts for Autophagosome Formation.

During autophagosome formation in mammalian cells, isolation membranes (IMs; autophagosome precursors) dynamically contact the ER. Here, we demonstrated that the ER-localized metazoan-specific autophagy protein EPG-3/VMP1 controls ER-IM contacts. Loss of VMP1 causes stable association of IMs with the ER, thus blocking autophagosome formation. Interaction of WIPI2 with the ULK1/FIP200 complex ...
and PI(3)P contributes to the formation of ER-IM contacts, and these interactions are enhanced by VMP1 depletion. VMP1 controls contact formation by promoting SERCA (sarco[endo]plasmic reticulum calcium ATPase) activity. VMP1 interacts with SERCA and prevents formation of the SERCA/PLN/SLN inhibitory complex. VMP1 also modulates ER contacts with lipid droplets, mitochondria, and endosomes. These ER contacts are greatly elevated by the SERCA inhibitor thapsigargin. Calmodulin acts as a sensor/effector to modulate the ER contacts mediated by VMP1/SERCA. Our study provides mechanistic insights into the establishment and disassociation of ER-IM contacts and reveals that VMP1 modulates SERCA activity to control ER contacts.
Mesh Terms:
Animals, Animals, Genetically Modified, Autophagosomes, Autophagy-Related Protein-1 Homolog, Autophagy-Related Proteins, COS Cells, CRISPR-Cas Systems, Caenorhabditis elegans, Caenorhabditis elegans Proteins, Calcium-Binding Proteins, Chlorocebus aethiops, Endoplasmic Reticulum, Genotype, HEK293 Cells, HeLa Cells, Humans, Intracellular Membranes, Intracellular Signaling Peptides and Proteins, Lipid Droplets, Membrane Proteins, Muscle Proteins, Phenotype, Phosphatidylinositol Phosphates, Proteolipids, RNA Interference, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Transfection
Mol Cell
Date: Sep. 21, 2017
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