Autophagy protein ATG-16.2 and its WD40 domain mediate the beneficial effects of inhibiting early-acting autophagy genes in C. elegans neurons

Abstract

While autophagy genes are required for lifespan of long-lived animals, their tissue-specific roles in aging remain unclear. Here, we inhibited autophagy genes in Caenorhabditis elegans neurons, and found that knockdown of early-acting autophagy genes, except atg-16.2, increased lifespan, and decreased neuronal PolyQ aggregates, independently of autophagosomal degradation. Neurons can secrete protein aggregates via vesicles called exophers. Inhibiting neuronal early-acting autophagy genes, except atg-16.2, increased exopher formation and exopher events extended lifespan, suggesting exophers promote organismal fitness. Lifespan extension, reduction in PolyQ aggregates and increase in exophers were absent in atg-16.2 null mutants, and restored by full-length ATG-16.2 expression in neurons, but not by ATG-16.2 lacking its WD40 domain, which mediates noncanonical functions in mammalian systems. We discovered a neuronal role for C. elegans ATG-16.2 and its WD40 domain in lifespan, proteostasis and exopher biogenesis. Our findings suggest noncanonical functions for select autophagy genes in both exopher formation and in aging.