Deacetylation of ATG16L1 is required for LC3-associated lysosomal microautophagy.

Microautophagy is a selective cellular process in which endolysosomes directly engulf cytoplasmic cargo through membrane invagination. The regulatory mechanisms governing microautophagy remain poorly understood. Here, we identified the deacetylation of ATG16L1 as a critical regulator of LC3-associated lysosomal microautophagy. We demonstrate that ATG16L1 acetylation is dynamically controlled by the acetyltransferase KAT2B and the deacetylase HDAC3. Under lysosomal osmotic stress or glucose deprivation, HDAC3-mediated deacetylation of ATG16L1 within its WD40 domain promotes its interaction with V-ATPase, facilitating ATG16L1 recruitment to lysosomal membranes. While dispensable for macroautophagy, this post-translational modification is essential for LC3 lipidation on lysosomes and enables lysosomal recovery, including the restoration of lysosomal size and degradative capacity following stress. Our results reveal a key role for ATG16L1 deacetylation in driving LC3-associated microautophagy to maintain lysosomal homeostasis.