ATG2 is a rod-shaped membrane-tethering protein suggested to mediate the endoplasmic reticulum (ER)-phagophore association and the expansion of the phagophore. We recently demonstrated that human ATG2A transfers lipids between membranes in vitro, which led us to propose a model that the phagophore expands upon the transfer of lipids from the ER by ATG2. Here, we summarize our findings and arising issues that need to be addressed to establish the mechanism of phagophore expansion.
Keywords: ATG18; ATG2; WIPI; lipid transfer; membrane tethering.