ABSTRACT
The biogenesis of mammalian autophagosomes remains to be fully defined. Here, we used cellular and in vitro membrane fusion analyses to show that autophagosomes are formed from a hitherto unappreciated hybrid membrane compartment. The autophagic precursors emerge through fusion of FIP200 vesicles, derived from the cis-Golgi, with endosomally derived ATG16L1 membranes to generate a hybrid pre-autophagosomal structure, HyPAS. A previously unrecognized apparatus defined here controls HyPAS biogenesis and mammalian autophagosomal precursor membranes. HyPAS can be modulated by pharmacological agents whereas its formation is inhibited upon severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or by expression of SARS-CoV-2 nsp6. These findings reveal the origin of mammalian autophagosomal membranes, which emerge via convergence of secretory and endosomal pathways, and show that this process is targeted by microbial factors such as coronaviral membrane-modulating proteins.
Subject(s)
Autophagosomes/virology , COVID-19/virology , Autophagy , COVID-19/metabolism , CRISPR-Cas Systems , Cell Line, Tumor , Endoplasmic Reticulum/metabolism , Endosomes/physiology , Endosomes/virology , Golgi Apparatus/physiology , HEK293 Cells , HeLa Cells , Humans , Membrane Fusion , Microscopy, Confocal , Phagosomes/metabolism , Phagosomes/virology , Qa-SNARE Proteins/biosynthesis , Receptors, sigma/biosynthesis , SARS-CoV-2 , Sarcoplasmic Reticulum Calcium-Transporting ATPases/biosynthesis , Synaptotagmins/biosynthesisABSTRACT
The integral membrane protein ATG9A plays a key role in autophagy. It displays a broad intracellular distribution and is present in numerous compartments, including the plasma membrane (PM). The reasons for the distribution of ATG9A to the PM and its role at the PM are not understood. Here, we show that ATG9A organizes, in concert with IQGAP1, components of the ESCRT system and uncover cooperation between ATG9A, IQGAP1 and ESCRTs in protection from PM damage. ESCRTs and ATG9A phenocopied each other in protection against PM injury. ATG9A knockouts sensitized the PM to permeabilization by a broad spectrum of microbial and endogenous agents, including gasdermin, MLKL and the MLKL-like action of coronavirus ORF3a. Thus, ATG9A engages IQGAP1 and the ESCRT system to maintain PM integrity.