Cycles of autoubiquitination and deubiquitination regulate the ERAD ubiquitin ligase Hrd1

Elife. 2019 Nov 12;8:e50903. doi: 10.7554/eLife.50903.

Abstract

Misfolded proteins in the lumen of the endoplasmic reticulum (ER) are retrotranslocated into the cytosol and polyubiquitinated before being degraded by the proteasome. The multi-spanning ubiquitin ligase Hrd1 forms the retrotranslocation channel and associates with three other membrane proteins (Hrd3, Usa1, Der1) of poorly defined function. The Hrd1 channel is gated by autoubiquitination, but how Hrd1 escapes degradation by the proteasome and returns to its inactive ground state is unknown. Here, we show that autoubiquitination of Hrd1 is counteracted by Ubp1, a deubiquitinating enzyme that requires its N-terminal transmembrane segment for activity towards Hrd1. The Hrd1 partner Hrd3 serves as a brake for autoubiquitination, while Usa1 attenuates Ubp1's deubiquitination activity through an inhibitory effect of its UBL domain. These results lead to a model in which the Hrd1 channel is regulated by cycles of autoubiquitination and deubiquitination, reactions that are modulated by the other components of the Hrd1 complex.

Keywords: ERAD; S. cerevisiae; biochemistry; cell biology; chemical biology; protein degradation; protein quality control; regulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum-Associated Degradation*
  • Enzyme Stability
  • Intracellular Membranes / metabolism
  • Membrane Glycoproteins / metabolism
  • Protein Domains
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination*

Substances

  • HRD3 protein, S cerevisiae
  • Membrane Glycoproteins
  • Saccharomyces cerevisiae Proteins
  • HRD1 protein, S cerevisiae
  • Ubiquitin-Protein Ligases