LEAP: a novel LC3C-dependent pathway connects autophagy, endocytic trafficking and signaling

Abstract

Macroautophagy/autophagy acts to promote homeostasis and is increasingly understood to selectively target cargo for degradation. The LC3-family of proteins mediate diverse yet distinct cargo recruitment to phagophores. However, what underlies specificity for cargo engagement among LC3 proteins is poorly understood. Using an unbiased protein interaction screen of LC3B and LC3C, we uncover a novel LC3C-endocytic-associated-pathway (LEAP) that recruits selective plasma membrane (PM) cargo to phagophores. We show LC3C but not LC3B localizes to peripheral endosomes and engages proteins that traffic between the PM, endosomes and autophagosomes. We establish that endocytic LC3C binds cargo internalized from the PM, including MET receptor tyrosine kinase and TFRC (transferrin receptor), and targets them toward autophagic degradation. These findings identify LEAP as an unexpected LC3C-dependent pathway, providing new understanding of selective coupling of PM signaling and autophagic degradation with important implications in cancer and other disease states.