Local Translation in Sustained Autophagy

Abstract

Autophagy is an evolutionarily conserved catabolic process. It involves a cascade of over 35 autophagy-related genes. During this process, a cupped phagophore membrane expands to surround cytoplasmic material, and eventually seals itself to form an autophagosome, which then fuses with lysosomes. Large numbers of autophagosomes form during stress responses, while simultaneously cells drastically reduce translation to conserve energy. Here, using proximity-labeling and Fluorescence in situ Hybridization we demonstrate that multiple mRNAs encoding proteins required for autophagy preferentially localize in proximity to forming autophagosomes. Polysome fractionation and proteomics of nascent proteins in proximity to forming autophagosomes further reveal that these mRNAs are preferentially actively translated there. The ribosome-binding protein RACK1 and eIF5A were essential to the localization of these autophagy-related mRNAs to forming autophagosomes and their local translation. Depletion of RACK1 or eIF5A disrupts the synthesis of essential autophagy proteins, leading to a reduction in autophagosome formation. This suggests that local translation provides an energy-efficient mechanism for rapidly supplying autophagy-related proteins, ensuring cells to massively induce autophagy while conserving energy during cell stress. Our findings highlight the critical role of local translation in autophagy regulation and demonstrate that inhibiting this process compromises cellular homeostasis, potentially exacerbating defects in autophagy and contributing to cellular dysfunction.