1. Academic Validation
  2. RNF126-Mediated Reubiquitination Is Required for Proteasomal Degradation of p97-Extracted Membrane Proteins

RNF126-Mediated Reubiquitination Is Required for Proteasomal Degradation of p97-Extracted Membrane Proteins

  • Mol Cell. 2020 Jul 16;79(2):320-331.e9. doi: 10.1016/j.molcel.2020.06.023.
Xianyan Hu 1 Linhan Wang 1 Yuancai Wang 2 Jia Ji 1 Jiqiang Li 1 Zhiyuan Wang 1 Congcong Li 1 Yaoyang Zhang 1 Zai-Rong Zhang 3
Affiliations

Affiliations

  • 1 Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 26 Qiuyue Road, Pudong New District, Shanghai 201203, China; University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, China.
  • 2 Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 26 Qiuyue Road, Pudong New District, Shanghai 201203, China.
  • 3 Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 26 Qiuyue Road, Pudong New District, Shanghai 201203, China; University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, China. Electronic address: zrzhang@sioc.ac.cn.
Abstract

Valosin-containing protein (VCP)/p97 is an AAA-ATPase that extracts polyubiquitinated substrates from multimeric macromolecular complexes and biological membranes for proteasomal degradation. During p97-mediated extraction, the substrate is largely deubiquitinated as it is threaded through the p97 central pore. How p97-extracted substrates are targeted to the Proteasome with few or no ubiquitins is unknown. Here, we report that p97-extracted membrane proteins undergo a second round of ubiquitination catalyzed by the cytosolic ubiquitin Ligase RNF126. RNF126 interacts with transmembrane-domain-specific chaperone BAG6, which captures p97-liberated substrates. RNF126 depletion in cells diminishes the ubiquitination of extracted membrane proteins, slows down their turnover, and dramatically stabilizes otherwise transient intermediates in the cytosol. We reconstitute the reubiquitination of a p97-extracted, misfolded multispanning membrane protein with purified factors. Our results demonstrate that p97-extracted substrates need to rapidly engage ubiquitin ligase-chaperone pairs that rebuild the ubiquitin signal for Proteasome targeting to prevent harmful accumulation of unfolded intermediates.

Keywords

RNF126; VCP; endoplasmic reticulum-associated degradation; membrane protein; p97/valosin-containing protein; proteasome; ubiquitination.

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