TY - JOUR
T1 - Destabilization of the VCP-Ufd1-Npl4 complex is associated with decreased levels of ERAD substrates
AU - Nowis, Dominika
AU - McConnell, Elizabeth
AU - Wójcik, Cezary
N1 - Funding Information:
This work was supported by the Biomedical Research Grant from Indiana University School of Medicine (22-812-57) and by the American Cancer Society grant IRG-84-002-22 (both to C.W.). We acknowledge the generous gifts of pCDNA3.1-HA-α-TCR from Dr. Ron Kopito (Stanford University); pEGFP-N1-Ub-R-GFP from Dr. Maria Masucci (Karolinska Institutet, Sweden), pCDNA3.1-HA-δ-CD3 from Dr. Allan Weissman (National Cancer Institute), the anti-p47 serum from Dr. Graham Warren (Yale University), the anti-Rpt2 serum from Dr. George N. DeMartino (UT Southwestern, Dallas, TX) and anti-derlin-1 serum from Dr. Tom Rapoport (Harvard University, Boston, MA).
PY - 2006/9/10
Y1 - 2006/9/10
N2 - 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.
AB - 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.
KW - ER-associated degradation (ERAD)
KW - Endoplasmic reticulum
KW - Proteasome
KW - Proteolysis
KW - Retrotranslocation
KW - T cell receptor (TCR)
KW - Ubiquitin
UR - http://www.scopus.com/inward/record.url?scp=33747371085&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33747371085&partnerID=8YFLogxK
U2 - 10.1016/j.yexcr.2006.05.013
DO - 10.1016/j.yexcr.2006.05.013
M3 - Article
C2 - 16822501
AN - SCOPUS:33747371085
SN - 0014-4827
VL - 312
SP - 2921
EP - 2932
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 15
ER -