TORC1 inactivation stimulates autophagy of nucleoporin and nuclear pore complexes

Abstract

The mechanisms underlying turnover of the nuclear pore complex (NPC) and the component nucleoporins (Nups) are still poorly understood. In this study, we found that the budding yeast Saccharomyces cerevisiae triggers NPC degradation by autophagy upon the inactivation of Tor kinase complex 1. This degradation largely depends on the selective autophagy-specific factor Atg11 and the autophagy receptor-binding ability of Atg8, suggesting that the NPC is degraded via receptor-dependent selective autophagy. Immunoelectron microscopy revealed that NPCs embedded in nuclear envelope-derived double-membrane vesicles are sequestered within autophagosomes. At least two pathways are involved in NPC degradation: Atg39-dependent nucleophagy (selective autophagy of the nucleus) and a pathway involving an unknown receptor. In addition, we found the interaction between Nup159 and Atg8 via the Atg8-family interacting motif is important for degradation of this nucleoporin not assembled into the NPC. Thus, this study provides the first evidence for autophagic degradation of the NPC and Nups, which we term "NPC-phagy" and "nucleoporinophagy."