| Project/Area Number |
13680695
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural biochemistry
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| Research Institution | Osaka City University (2002)
Himeji Institute of Technology (2001) |
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Principal Investigator |
TOKUNAGA Fuminori Osaka City University, Graduate School of Medicine, Associated Professor, 大学院・医学研究科, 助教授 (00212069)
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| Co-Investigator(Kenkyū-buntansha) |
KOIDE Takehiko Himeji Institute of Technology, Department of Life Science, Professor, 大学院・理学研究科, 教授 (60018695)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2002: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | ERAD / proteasome / N-linked oligosaccharide / ubiquitin ligase / 核内凝集体 / ユビキチン / アグリソーム |
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| Research Abstract |
The endoplasmic reticuium (ER) is known to function as a quality control machinery of nascent proteins, and various misfolded or unassembled proteins in the ER are targeted to ubiquitin/proteasome-mediated degradation after retrotranslocation to the cytosol through the Sec61 translocon. We have shown that not only proteasome inhibitors such as lactacystin and carbobenzoxy-leucyl-leucyl-leucinal (LLL), but also inhibitors of ER mannosidase I such as kifunensine and deoxyrnannojirimycin, strongly inhibit the ERAD of various misfolded proteins, suggesting that processing of N-linked oligosaccharide plays an important role on ERAD. In this study, collaborating with Dr. Yoshida in Tokyo Metropolitan Institute of Medical Science, we found that N-glycan serves as a signal for degradation by the Skpl-Cullin1-Fbx2-Rbx1 (SCF^<Fbx2>) ubiquitin ligase complex. The F-box protein Fbx2 binds specifically to proteins attached to N-inked high-mannose oligosaccharides and subsequently contributes to ubiquitination of N-glycosylated proteins. In addition, expression of the mutant Fbx2ΔF, which lacks the F-box domain that is essential for forming the SCF complex, appreciably blocks degradation of typical substrates of the ERAD pathway. Our results indicate that SCF^<Fbx2> ubiquitinates N-glycosylated proteins that are translocated from the ER to the cytosol by the quality control mechanism.
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