Destabilization of the VCP-Ufd1-Npl4 complex is associated with decreased levels of ERAD substrates

Dominika Nowis, Elizabeth McConnell, Cezary Wójcik

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

p97/VCP associated with Ufd1-Npl4 is considered a key player in ER-associated degradation (ERAD). RNA interference (RNAi) of one component of the Ufd1-Npl4 heterodimer destabilizes the VCP-Ufd1-Npl4 complex inducing proteasome-dependent degradation of the other component and releasing free VCP. In contrast to RNAi of VCP, RNAi of Ufd1 or Npl4 depleting ∼90% of the VCP-Ufd1-Npl4 complexes does not induce unfolded protein response, indicating that the Ufd1-Npl4 dimer is not involved in the regulation of ER function by VCP. RNAi of Ufd1 or Npl4 is associated with a 2-fold increase in the levels of polyubiquitinated proteins, which form dispersed aggregates often associated with calnexin-positive structures. However, contrary to the effects of proteasome inhibition, RNAi of Ufd1 or Npl4 does not induce an accumulation of α-TCR and δ-CD3, two ERAD substrates overexpressed in HeLa cells. Instead, a 60-70% decrease in their levels is observed. The decrease in α-TCR levels is associated with a 50% decrease of its half-life. Upregulation of the putative channel forming protein, derlin-1, may contribute to the increased degradation of ERAD substrates. To explain our findings, we propose a model, where association of emerging ERAD substrates with VCP-Ufd1-Npl4 is not required for their degradation but has a regulatory role.

Original languageEnglish (US)
Pages (from-to)2921-2932
Number of pages12
JournalExperimental Cell Research
Volume312
Issue number15
DOIs
StatePublished - Sep 10 2006

Keywords

  • ER-associated degradation (ERAD)
  • Endoplasmic reticulum
  • Proteasome
  • Proteolysis
  • Retrotranslocation
  • T cell receptor (TCR)
  • Ubiquitin

ASJC Scopus subject areas

  • Cell Biology

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