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

Yan G Zhao, Yong Chen, Guangyan Miao, Hongyu Zhao, Wenyan Qu, Dongfang Li, Zheng Wang, Nan Liu, Lin Li, She Chen, Pingsheng Liu, Du Feng, Hong Zhang

Molecular cell 2017 Sep 21

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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. Copyright © 2017 Elsevier Inc. All rights reserved.

Citation

Yan G Zhao, Yong Chen, Guangyan Miao, Hongyu Zhao, Wenyan Qu, Dongfang Li, Zheng Wang, Nan Liu, Lin Li, She Chen, Pingsheng Liu, Du Feng, Hong Zhang. The ER-Localized Transmembrane Protein EPG-3/VMP1 Regulates SERCA Activity to Control ER-Isolation Membrane Contacts for Autophagosome Formation. Molecular cell. 2017 Sep 21;67(6):974-989.e6