Phosphorylation regulates the binding of autophagy receptors to FIP200 Claw domain for selective autophagy initiation

Zixuan Zhou,Xinyu Gong,Yingli Wang,Miao Li,Chao Peng,Jianping Liu,Mingfang Zhang,Ying Li,Ping Wu,Xiaolong Xu,Tao Fu,Lifeng Pan,Yaru Wang

doi:10.1038/s41467-021-21874-1

Abstract

The ULK complex initiates the autophagosome formation, and has recently been implicated in selective autophagy by interacting with autophagy receptors through its FIP200 subunit. However, the structural mechanism underlying the interactions of autophagy receptors with FIP200 and the relevant regulatory mechanism remain elusive. Here, we discover that the interactions of FIP200 Claw domain with autophagy receptors CCPG1 and Optineurin can be regulated by the phosphorylation in their respective FIP200-binding regions. We determine the crystal structures of FIP200 Claw in complex with the phosphorylated CCPG1 and Optineurin, and elucidate the detailed molecular mechanism governing the interactions of FIP200 Claw with CCPG1 and Optineurin as well as their potential regulations by kinase-mediated phosphorylation. In addition, we define the consensus FIP200 Claw-binding motif, and find other autophagy receptors that contain this motif within their conventional LC3-interacting regions. In all, our findings uncover a general and phosphoregulatable binding mode shared by many autophagy receptors to interact with FIP200 Claw for autophagosome biogenesis, and are valuable for further understanding the molecular mechanism of selective autophagy.

Highlights

The ULK complex initiates the autophagosome formation, and has recently been implicated in selective autophagy by interacting with autophagy receptors through its FIP200 subunit
Dozens of autophagy receptors have been identified in mammals, such as SQSTM1/P62, NBR1, Optineurin, CALCOCO2/ NDP52, TAX1BP1, CCPG1, FAM134B, Nix, FUNDC1, and STBD1, all of which contain a cargo-associating domain or motif that can recognize designated autophagic cargoes, and a LC3-interacting region (LIR) that can recruit ATG8 family proteins known as LC3A, LC3B, LC3C, GABARAP, GABARAPL1, and GABARAPL2 in mammals[7,8,11,13,33,34,35,36,37]
To elucidate how the FIP200 Claw domain recognizes its binding partners, we firstly focused on the interaction of the FIP200 Claw domain with the second FIR motif (FIR2) of CCPG1, and sought to determine their complex structure

Summary

Introduction

The ULK complex initiates the autophagosome formation, and has recently been implicated in selective autophagy by interacting with autophagy receptors through its FIP200 subunit. Recent studies revealed that the ULK complex directly participates in the initiation of autophagosome formation in selective autophagy independent of nutrient status, and is required for several different types of selective autophagy processes including the CCPG1-mediated ERphagy[30], P62-mediated aggrephagy[49], and NDP52-mediated xenophagy[50,51] During those ULK complex-involved selective autophagy processes, autophagy receptor can directly recruit the ULK complex to the vicinity of the targeting cargo for autophagy initiation by interacting with the FIP200 subunit[30,49,50,51], which is a large scaffold protein and mainly contains an ATG13-binding N-terminal domain, an LIR motif followed by several coiled-coil regions and an extreme C-terminal Claw domain (Supplementary Fig. 1). Our findings provide mechanistic insights into the interactions of FIP200 with autophagy receptors CCPG1 and Optineurin, and expand our understandings of the interaction modes between FIR motifs and FIP200 Claw in general

Methods

Results

Conclusion