| Project/Area Number |
11670989
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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 |
Hematology
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| Research Institution | Yamanashi Medical University |
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Principal Investigator |
OZAKI Yukio Yamanashi Medical University, Department of Laboratory Medicine, Professor, 医学部, 教授 (30134539)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Kaneo Yamanashi Medical University, Department of Laboratory Medicine, Assistant, 医学部, 教務職員 (20242662)
YATOMI Yutaka Yamanashi Medical University, Department of Laboratory Medcine, Associate Professor, 医学部, 助教授 (60200523)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | Platelet activation / collagen receptor / GPIa / IIa / rhodocytin / tyrosine kinase / Src / Cas / GPla / lla |
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| Research Abstract |
Although glycoprotein Ia/IIa (GpIa/IIa, integrin α_2β_1) has established its role as a collagen receptor, it remains unclear whether GPIa/IIa mediates activation signals. In this study, we show that rhodocytin, purified from the Calloselasma rhodostoma venom, induces platelet aggregation, which can be blocked by anti-GPIa mAbs. Studies with rhodocytin- coupled beads and liposomes loaded with recombinant GPIa/IIa demonstrated that rhodocytin directly binds to GPIa/IIa independently of divalent cations. In vitro kinase assays and Western blotting of GPIa immunoprecipitates revealed that Src and Lyn constitutively associate with GPIa/IIa and that Src activity increases transiently after rhodocytin stimulation. Src specifically associates with p130 Crk-associated substrate (Cas) in a manner dependent upon Cas phosphorylation, suggesting that Src is responsible for Cas tyrosine phosphorylation. While all these phenomena occur early after rhodocytin stimulation in a cAMP-resistant manner-tyrosine phosphorylation of Syk and phospholipase C γ2 (PLC γ2), intracellular Ca^<2+> mobilization, and platelet aggregation occur later in a cAMP-sensitive manner. Cytochalasin D, which interferes with actin polymerization and blocks receptor clustering, inhibits all the rhodocytin-mediated signals we examined in this study. We suggest that rhodocytin, by clustering GPIa/IIa, activates GPIa/IIa-associated Src, which then mediates downstream activation signals.
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