Structural basis for nucleotide-modulated p97 association with the ER membrane

Wai Kwan Tang,Yihong Ye,Ting Zhang,Di Xia

doi:10.1038/celldisc.2017.45

Abstract

Association of the cytosolic AAA (ATPases associated with various cellular activities) protein p97 to membranes is essential for various cellular processes including endoplasmic reticulum (ER)-associated degradation. The p97 consists of two ATPase domains and an N domain that interacts with numerous cofactors. The N domain of p97 is known to undergo a large nucleotide-dependent conformation switch, but its physiological relevance is unclear. Here we show p97 is recruited to canine ER membranes predominantly by interacting with VCP-interacting membrane protein (VIMP), an ER-resident protein. We found that the recruitment is modulated through a nucleotide-dependent conformation switch of the N domain in wild-type p97, but this modulation is absent in pathogenic mutants. We demonstrate the molecular mechanism of the modulation by a series of structures of p97, VIMP and their complexes and suggest a physiological role of the nucleotide-dependent N domain conformation switch. The lack of modulation in pathogenic mutants is caused by changes in interactions between the N and D1 domain, as demonstrated by multiple intermediate positions adopted by N domains of mutant p97. Our findings suggest the nucleotide-modulated membrane association may also have a role in other p97-dependent processes.

Highlights

Protein quality control eliminates misfolded or unwanted proteins to maintain protein homeostasis and is an essential cellular process that has been identified in every subcellular compartment
VCPinteracting membrane protein (VIMP) is the p97 receptor on canine endoplasmic reticulum (ER) membranes As part of an ER membrane protein complex that mediates retrotranslocation, VIMP was shown previously to interact with p97 in conjunction with Derlin1 and this interaction was found to be independent of Ufd1-Npl4 [34]
This result is consistent with a previous finding that the complex of Derlin-1 and VIMP was the major component coprecipitated with p97 from these membranes, further supporting VIMP as a major mediator of p97 membrane association in the context of pancreatic ER membranes

Summary

Introduction

Protein quality control eliminates misfolded or unwanted proteins to maintain protein homeostasis and is an essential cellular process that has been identified in every subcellular compartment. In the endoplasmic reticulum (ER), an organelle that houses most nascent secretory and membrane proteins, misfolded or unwanted protein substrates are recognized by chaperones, directed to the ER membrane for retrotranslocation or dislocation to the cytosol, and subsequently targeted for degradation by the ubiquitin–proteasome system This process has been dubbed ER-associated degradation (ERAD, for reviews, see Vembar and Brodsky [1] and Meyer and Weihl [2]). Assembly of the mammalian ERAD apparatus is thought to be initiated by the association of luminal substrates with a member of the rhomboid pseudoprotease family consisting of Derlin and 3 This is followed by the recruitment of Hrd, a ubiquitin ligase thought to form a retrotranslocation channel, and p97, an ATPase, together with its adaptor proteins Ufd and Npl (UN). The interaction of the p97-Ufd1-Npl complex with the ER membrane in mammalian cells appears to be mediated by several proteins residing in the ER membrane, including gp, UbxD8, Erasin and Derlins [3], VCPinteracting membrane protein (VIMP) was identified as a major adaptor for p97 in studies using canine pancreas ER membranes [4,5,6]

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Results

Conclusion