? Endoplasmic reticulum-associated degradation (ERAD) is a process by which misfolded, unassembled, and some normal proteins are targeted for degradation by the ubiquitin proteasome pathway. ERAD is essential for many normal cellular processes and its dysfunctions contribute to the pathological conditions associated with Alzheimers' and Parkinson's diseases, cystic fibrosis, and al-antitrypsin-deficiency. While it is known that ERAD involves substrate ubiquitination, retrotranslocation, and proteasomal degradation, the molecular mechanisms for these events are not clear. To begin elucidating these molecular mechanisms, we have discovered that autocrine motility factor receptor, also known as gp78, is an ER-resident ubiquitin ligase (E3) required for ERAD and have now identified two additional gp78-interacting proteins: valosin-containing protein (VCP) and ubiquitin. Interaction of VCP with gp78 appears to activate VCP-polyubiquitin binding and facilitate polyubiquitinated protein degradation. Previous studies by others have shown that VCP is an essential factor for retrotranslocation. The finding of gp78 interactions with VCP and ubiquitin provides a novel avenue for elucidating the molecular mechanisms in ERAD. We hypothesize that gp78-acivated VCPpolyubiquitin binding couples substrate ubiquitination, retrotranslocation, and degradation during ERAD. To test the hypothesis, we propose the following specific aims: (1) to characterize gp78 interaction with VCP, ubc7, ubiquitin, and sec61 channel; (2) to elucidate the mechanisms by which gp78 activates VCPpolyubiquitin interaction; and (3) to evaluate the roles of gp78-activated VCP-polyubiquitin interaction in retrotranslocation and degradation of ERAD substrates. These studies will advance the current understanding of how gp78 and VCP is involved in substrate ubiquitination, retrotranslocation, and degradation during ERAD. The proposed work is consistent with this laboratory's long-term goal of understanding the molecular mechanisms of ERAD and its implications for disease pathogenesis. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM069967-05
Application #
7459553
Study Section
Biochemistry Study Section (BIO)
Program Officer
Jones, Warren
Project Start
2004-07-01
Project End
2010-01-02
Budget Start
2008-07-01
Budget End
2010-01-02
Support Year
5
Fiscal Year
2008
Total Cost
$278,610
Indirect Cost
Name
University of MD Biotechnology Institute
Department
Type
Organized Research Units
DUNS #
603819210
City
Baltimore
State
MD
Country
United States
Zip Code
21202
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Yang, Hui; Liu, Chao; Zhong, Yongwang et al. (2010) Huntingtin interacts with the cue domain of gp78 and inhibits gp78 binding to ubiquitin and p97/VCP. PLoS One 5:e8905
Apostolou, Andria; Shen, Yuxian; Liang, Yan et al. (2008) Armet, a UPR-upregulated protein, inhibits cell proliferation and ER stress-induced cell death. Exp Cell Res 314:2454-67
Ballar, Petek; Zhong, Yongwang; Nagahama, Masami et al. (2007) Identification of SVIP as an endogenous inhibitor of endoplasmic reticulum-associated degradation. J Biol Chem 282:33908-14
Shen, Yuxian; Ballar, Petek; Apostolou, Andria et al. (2007) ER stress differentially regulates the stabilities of ERAD ubiquitin ligases and their substrates. Biochem Biophys Res Commun 352:919-24
Yang, Hui; Zhong, Xiaoyan; Ballar, Petek et al. (2007) Ubiquitin ligase Hrd1 enhances the degradation and suppresses the toxicity of polyglutamine-expanded huntingtin. Exp Cell Res 313:538-50
Ballar, Petek; Shen, Yuxian; Yang, Hui et al. (2006) The role of a novel p97/valosin-containing protein-interacting motif of gp78 in endoplasmic reticulum-associated degradation. J Biol Chem 281:35359-68
Zhang, Jun; Jiang, Yixing; Jia, Zhiliang et al. (2006) Association of elevated GRP78 expression with increased lymph node metastasis and poor prognosis in patients with gastric cancer. Clin Exp Metastasis 23:401-10
Shen, Yuxian; Ballar, Petek; Fang, Shengyun (2006) Ubiquitin ligase gp78 increases solubility and facilitates degradation of the Z variant of alpha-1-antitrypsin. Biochem Biophys Res Commun 349:1285-93
Gong, Weida; Jiang, Yixing; Wang, Liwei et al. (2005) Expression of autocrine motility factor correlates with the angiogenic phenotype of and poor prognosis for human gastric cancer. Clin Cancer Res 11:5778-83

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