A regulatory circuit comprising the CBP and SIRT7 regulates FAM134B-mediated ER-phagy

Abstract

Macroautophagy (autophagy) utilizes a serial of receptors to specifically recognize and degrade autophagy cargoes, including damaged organelles, to maintain cellular homeostasis. Upstream signals spatiotemporally regulate the biological functions of selective autophagy receptors through protein post-translational modifications (PTM) such as phosphorylation. However, it is unclear how acetylation directly controls autophagy receptors in selective autophagy. Here, we report that an ER-phagy receptor FAM134B is acetylated by CBP acetyltransferase, eliciting intense ER-phagy. Furthermore, FAM134B acetylation promoted CAMKII-mediated phosphorylation to sustain a mode of milder ER-phagy. Conversely, SIRT7 deacetylated FAM134B to temper its activities in ER-phagy to avoid excessive ER degradation. Together, this work provides further mechanistic insights into how ER-phagy receptor perceives environmental signals for fine-tuning of ER homeostasis and demonstrates how nucleus-derived factors are programmed to control ER stress by modulating ER-phagy.