| Project/Area Number |
16390432
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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 |
Orthopaedic surgery
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NAKAGAWA Takumi The University of Tokyo, Faculty of Medicine, Research Associate, 医学部附属病院, 助手 (90338385)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Sakae The University of Tokyo, Faculty of Medicine, Lecture, 医学部附属病院, 講師 (50282661)
ODA Hiromi Saitama medical University, Hospital, Professor, 病院・教授 (60101698)
HARA Yukinori The University of Tokyo, Faculty of Medicine, Medical staff, 医学部附属病院, 医員 (30396741)
ISHIYAMA Noriyuki The University of Tokyo, Faculty of Medicine, Medical staff, 医学部附属病院, 医員 (60376481)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥9,600,000 (Direct Cost: ¥9,600,000)
Fiscal Year 2005: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 2004: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Keywords | Osteoclast / Rac1 / M-CSF / Akt / apoptosis / 低分子量Gタンパク質 / アデノウイルスベクター / 骨吸収 |
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| Research Abstract |
Introduction : Rac1 is a member of Rho family small G-proteins and recent studies have revealed that it mediates anti-apoptotic signals in some types of cells. Rac1 is reported to be required for the cytoskeletal organization and bone-resorbing activity of osteoclasts, but their roles in the osteoclast survival and function are not fully elucidated yet.
Materials and methods : We constructed the adenovirus vector carrying cDNA of either dominant negative Rac1 (Rac1DN) or constitutively active Rac1 (Rac1 CA) gene, and osteoclast-like cells (OCLs) generated in mouse co-culture system were infected with these viruses. To examine the role of Rac1 in osteoclast survival and function, we performed pit formation assay, survival assay and Western blotting including activated-Rac1 pull down assay using adenovirus-infected OCLs. To further clarify the mechanism of Rac1 regulation in osteoclast survival, some specific inhibitors and adenovirus vectors of signal transduction molecules were used. To
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quantify membrane movement before and after M-CSF treatment, OCLs expressing either EGFP or Rac1 DN were recorded with a time-lapse video-microscope.
Results : Adenovirus vector-mediated dominant negative Rac1 (Rac1DN) expression significantly reduced pit formation, and promoted their apoptosis. Macrophage colony-stimulating factor (M-CSF) rapidly activated Rac1, and the pro-survival effect of M-CSF for OCLs was abrogated by Rac1 DN overexpression. Constitutively active Rac1 enhanced OCL survival, which was completely suppressed by phosphatidylinositol 3'-kinase (PI3K) inhibitors, while a Mek inhibitor had only partial effect. Rac1DN also partially blocked the activation of Akt induced by overexpressing catalytic subunit of PI3K. Using time-lapse video-microscopy, we found that Rac1 DN expression reduced the membrane ruffling and spreading of OCLs in response to M-CSF.
Conclusion : Small GTPase Rac1 is critically involved in M-CSF receptor signaling, and mediates survival signaling of osteoclasts primarily by modulating PI3K/Akt pathways. Rac1 also plays a significant role in bone resorptive activity of the cells, probably by regulating the motility of osteoclasts. Less
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