A conserved ATG2‐GABARAP family interaction is critical for phagophore formation

Abstract

The intracellular trafficking pathway, macroautophagy, is a recycling and disposal service that can be upregulated during periods of stress to maintain cellular homeostasis. An essential phase is the elongation and closure of the phagophore to seal and isolate unwanted cargo prior to lysosomal degradation. Human ATG2A and ATG2B proteins, through their interaction with WIPI proteins, are thought to be key players during phagophore elongation and closure, but little mechanistic detail is known about their function. We have identified a highly conserved motif driving the interaction between human ATG2 and GABARAP proteins that is in close proximity to the ATG2‐WIPI4 interaction site. We show that the ATG2A‐GABARAP interaction mutants are unable to form and close phagophores resulting in blocked autophagy, similar to ATG2A/ATG2B double‐knockout cells. In contrast, the ATG2A‐WIPI4 interaction mutant fully restored phagophore formation and autophagy flux, similar to wild‐type ATG2A. Taken together, we provide new mechanistic insights into the requirements for ATG2 function at the phagophore and suggest that an ATG2‐GABARAP/GABARAP‐L1 interaction is essential for phagophore formation, whereas ATG2‐WIPI4 interaction is dispensable.

Structure and Dynamics in the ATG8 Family From Experimental to Computational Techniques

“…The LIR motifs of the autophagy-related proteins ATG2A and ATG2B have also been shown to interact preferentially with GABARAP and GABARAPL1 (Bozic et al, 2020). ATG2A and ATG2B did not interact with LC3B/C or GABARAPL2, and only weakly with LC3A in co-immunoprecipitation assays (Bozic et al, 2020).…”

Mitochondrial Dysfunction, Oxidative Stress and Neuroinflammation in Neurodegeneration with Brain Iron Accumulation (NBIA)

“…WD40 proteins play a role in coordinating protein–protein interactions in order to perform a variety of functions, such as signal transduction, autophagy or transcriptional regulation. In particular, the WDR45 protein, by binding to phosphatidylinositol-3-phosphate (PtdIns3P), regulates autophagosome formation [ 149 , 150 , 151 ]. In this way, defective autophagic flux associated with WDR45 mutations have been described in different cellular and animal studies [ 147 , 152 , 153 , 154 , 155 ].…”

“…KO mice for Wdr45 show an impaired autophagic flux with accumulation of SQSTM1- and ubiquitin-positive aggregates in neurons and swollen axons. Furthermore, KO male animals displayed learning and memory defects and axonal swelling, although without iron deposition in the basal ganglia [ 151 ]. In line with this, accumulated ER proteins have been observed as a result of WDR45 deficiency, together with increased ER stress and impaired ER quality control.…”

The role of lipids in autophagy and its implication in neurodegeneration

“…The authors showed that ATG2A can bind multiple glycerophospholipids and, in turn, transport them between membranes. While there is still controversy concerning the protein partners and the molecular mechanism that modulates the ATG2 lipid transfer, a recent paper established that GABARAP (γ-aminobutyric acid receptorassociated protein) is a crucial anchor protein for ATG2A whereas its binding to WIPI4 is not required in mammals for the formation and closing of the autophagosome [67]. Interestingly, other cellular compartments related with autophagosomes, like the endosomal compartment, are also enriched in PI3P and further research on the lipid transfer from these structures into the nascent autophagosomes would be necessary to fully understand the source of the autophagosomal membrane in different cellular compartments.…”