The WD40 domain of autophagy protein ATG-16.2 is required for lysosomal regulation and longevity in germline-less C. elegans

Abstract

Autophagy is a conserved cellular recycling pathway linked to longevity and regulated by autophagy-related (ATG) protein. Many of these proteins serve a key function in ATG8 lipidation onto autophagosomal membranes, a step that precedes subsequent lysosomal degradation. Recently, mammalian ATG16L1, a member of ATG8 lipidation machinery, have been shown to also direct ATG8 lipidation onto other membranes via its C-terminal WD40 domain in acutely stressed cells. However, whether such non-canonical functions of the ATG16L1 WD40 domain influence longevity remain largely unknown. Here, we endogenously deleted the WD40 domain of atg-16.2, the C. elegans ortholog of ATG16L1, and examined autophagy, healthspan and longevity. The ATG-16.2 WD40 domain was dispensable for healthspan measures and for ATG8 lipidation in whole animals and neurons but was required for autophagic flux across all major tissues examined. Notably, the ATG-16.2 WD40 domain was also critical in limiting lysosomal membrane damage after acute heat stress. Because long-lived C. elegans mutants are typically heat resistant, we asked whether this lysosomal function supported their thermotolerance and found the WD40 domain to be selectively required for thermotolerance induced by germline removal, but not by reduced insulin/IGF-1 signaling or dietary restriction. In germline-less animals, loss of the ATG-16.2 WD40 domain reduced nuclear TFEB/HLH-30, reduced neuronal autophagic degradation, altered neuronal lysosomal pH, and sensitized animals to heat-induced lysosomal damage. Collectively, these findings establish the ATG16 WD40 domain as a regulator of autophagic degradation and lysosomal integrity in vivo, and show that this role is associated with longevity in a pathway-selective manner.