2005 Fiscal Year Final Research Report Summary
Regulatory mechanisms of ligand binding and signaling events of laminin-binding integrins
| Project/Area Number |
15370055
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional biochemistry
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| Research Institution | Osaka University |
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Principal Investigator |
SEKIGUCHI Kiyotoshi Osaka University, Institute for Protein Research, Professor, 蛋白質研究所, 教授 (50187845)
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| Co-Investigator(Kenkyū-buntansha) |
GU Jianguo Osaka University, Graduate School of Medicine, Associate Professor, 医学研究科, 助教授 (40260369)
YAMADA Masashi Osaka University, Institute for Protein Research, Instructor, 蛋白質研究所, 助手 (90304055)
TAKAGI Junichi Osaka University, Institute for Protein Research, Professor, 蛋白質研究所, 教授 (90212000)
FUTAKI Sugiko Osaka University, Institute for Protein Research, Instructor, 蛋白質研究所, 助手 (00403014)
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| Project Period (FY) |
2003 – 2005
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| Keywords | extracellular matrix / basement membrane / cell adhesion / laminin / integrin / signal transduction / cell / tetraspanin |
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| Research Abstract |
CD151, one of the tetraspanins, forms a stable complex with integrin alpha3beta1, the major laminin receptor on the cell surface. We found that 8C3, an anti-CD151 mAb obtained by screening for reactivity with integrin alpha3beta1-CD151 complexes, was capable of dissociating CD151 from integrin alpha3beta1, thereby allowing us to deplete CD151 from purified integrin alpha3beta1-CD151 complexes. The CD151-free integrin alpha3beta1 thus obtained showed a significant reduction in its ability to bind to laminin-10/11, a high-affinity ligand for integrin alpha3beta1, with a concomitant reduction in its reactivity with mAb AG89, which recognizes activated beta1-containing integrins. These results raised the possibility that the association of integrin alpha3beta1 with CD151 potentiates the ligand-binding activity of the integrin through sustaining its activated conformation. In support of this possibility, the ligand-binding activity was restored when CD151-free integrin alpha3beta1 was re-associated with purified CD151. 8C3-induced dissociation of CD151 from integrin alpha3beta1 was also demonstrated on the surface of living cells by FRET imaging, accompanied by a concomitant reduction in the cell adhesion to laminin-10/11-coated substrates. CD151 knock-down by RNAi also resulted in a reduction in the adhesive activity of the cells. Taken together, these results indicate that CD151 association modulates the ligand-binding activity of integrin alpha3beta1 through stabilizing its activated conformation not only with purified proteins but also in a physiological context.
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