Journal
AUTOPHAGY
Volume 17, Issue 2, Pages 586-587Publisher
TAYLOR & FRANCIS INC
DOI: 10.1080/15548627.2020.1846304
Keywords
Arabidopsis thaliana CDK5RAP3; ER-phagy; ER-quality control; ribosome stalling; selective autophagy; selective autophagy receptor; ufmylation
Categories
Funding
- Austrian Science Fund [P32355]
- Vienna Science and Technology Fund (WWTF) [LS17-047]
- Osterreichischen Akademie der Wissenschaften
- Austrian Science Fund (FWF) [P32355] Funding Source: Austrian Science Fund (FWF)
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This study identified a new reticulophagy receptor C53 in Arabidopsis, which interacts with ATG8 and is involved in ER quality control mechanisms during stress. C53 senses ER stress by forming a complex with UFL1 and its adaptor protein DDRK1, and its activity is regulated by UFM1.
Reticulophagy, the autophagic degradation of the endoplasmic reticulum, is crucial to maintain ER homeostasis during stress. Although several reticulophagy receptors have been discovered recently, most of them have been studied using nutrient starvation. How macroautophagy/autophagy cross-talks with other ER-quality control mechanisms is largely unknown. Using ATG8-based affinity proteomics in the model plant Arabidopsis thaliana, we identified AT5G06830/C53, a soluble protein that directly interacts with ATG8. Biochemical and biophysical characterization of C53-ATG8 interaction using both human (CDK5RAP3) and Arabidopsis proteins revealed that C53 binds ATG8 via shuffled Atg8-family interacting motifs (sAIMs) located at its intrinsically disordered region (IDR). C53 is recruited to phagophores, precursors to autophagosomes, during ER stress in an autophagy-dependent manner. Consistently, c53 mutants are highly sensitive to ER stress treatments. C53 senses ER stress by forming a tripartite receptor complex that involves UFL1, the E3 ligase that mediates ufmylation, and its ER-resident adaptor protein DDRGK1. C53 activity is regulated by another ubiquitin-like protein, UFM1, which is transferred from C53 to the ribosomes upon ribosome collision/stalling at the ER, thereby activating the C53 pathway to recycle stalled nascent chains. Altogether our findings suggest C53 forms an ancient quality control pathway that links ribosome-associated quality control with selective autophagy at the ER.
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