Lysosome damage triggers direct ATG8 conjugation and ATG2 engagement via CASM

Abstract

Cells harness multiple pathways to maintain lysosome integrity, a central homeostatic process. Damaged lysosomes can be repaired, or targeted for degradation by lysophagy, a selective autophagy process involving ATG8/LC3. Here, we describe a parallel ATG8/LC3 response to lysosome damage, mechanistically distinct from lysophagy. Using a comprehensive series of biochemical, pharmacological and genetic approaches, we show that lysosome damage induces rapid Conjugation of ATG8s to Single Membranes (CASM). ATG8 proteins are recruited directly onto damaged membranes, independently of ATG13/WIPI2, and conjugated to PS, as well as PE, a molecular hallmark of CASM. Lysosome damage drives V-ATPase V0-V1 association, and direct recruitment of ATG16L1, dependent on K490 (WD40-domain), and sensitive to Salmonella SopF. Lysosome damage-induced CASM is associated with the formation of dynamic LC3A-positive tubules, and promotes robust LC3A engagement with ATG2, a lipid transfer protein central to lysosome repair. Together, our data identify direct ATG8 conjugation as a rapid response to lysosome damage, with important links to lipid transfer and dynamics.