The WD40 domain of ATG16L1 is required for its non-canonical role in lipidation of LC3 at single membranes

A hallmark of macroautophagy is the covalent lipidation of LC3 and insertion into the double-membrane phagophore, which is driven by the ATG16L1/ATG5-ATG12 complex. In contrast, non-canonical Autophagy is a pathway through which LC3 is lipidated and inserted into single membranes, particularly endolysosomal vacuoles during cell engulfment events such as LC3-associated phagocytosis. Factors controlling the targeting of ATG16L1 to phagophores are dispensable for non-canonical Autophagy, for which the mechanism of ATG16L1 recruitment is unknown. Here we show that the WD repeat-containing C-terminal domain (WD40 CTD) of ATG16L1 is essential for LC3 recruitment to endolysosomal membranes during non-canonical Autophagy, but dispensable for canonical Autophagy. Using this strategy to inhibit non-canonical Autophagy specifically, we show a reduction of MHC class II antigen presentation in dendritic cells from mice lacking the WD40 CTD Further, we demonstrate activation of non-canonical Autophagy dependent on the WD40 CTD during influenza A virus Infection. This suggests dependence on WD40 CTD distinguishes between macroautophagy and non-canonical use of Autophagy machinery.

ATG16L1; LC3; autophagy; influenza; phagocytosis.