2006 Fiscal Year Final Research Report Summary
Roles of calcium-mediated signal transduction pathway in the formation and function of sperm
| Project/Area Number |
16370064
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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 | Tokyo University of Pharmacy and Life Sciences |
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Principal Investigator |
FUKAMI Kiyoko Tokyo University of Pharmacy and Life Sciences, School of Life Science, Professor, 生命科学部, 教授 (40181242)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Yoshikazu Tokyo University of Pharmacy and Life Sciences, School of Life Science, Research Associate, 生命科学部, 助手 (60366416)
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| Project Period (FY) |
2004 – 2006
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| Keywords | calcium / sperm / fertilization / phospholipase C / GRIP1 / Ca channel |
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| Research Abstract |
Calcium has very important roles in various steps of fertilization. We reported previously that phospholipase Cδ4 (PLCδ4) is required for calcium mobilization in the zona pellucida-induced acrosome reaction in sperm. Here we report that glutamate receptor-interacting protein1 (GRIP1) was identified as a binding protein of the PLCδ4-C2 domain. Physiological interaction of GRIP1 with PLCδ4 in mouse testis was confirmed by immunoprecipitation with anti-PLCδ4 antibodies and the association seemed to correlate with the maturation stage of sperm. These results indicate that PLCδ4 binds via its C2 domain to GRIP1, and that this association may play a role in spermatogenesis.
Because sperm-specific phospholipase C-zeta (PLC) induces Ca^<2+> oscillations and egg activation when injected into mouse eggs, we tried to carry out the structure-function analysis. We found that EF1 and EF2 of PLCζ are important for the PLC activity, and EF3 is responsible for its high Ca2+ sensitivity. Deletion of four EF-hand domains or C-terminal C2 domain caused complete loss of PLC activity, indicating that both regions are prerequisite for the PLCζ activity.
In addition, we noted that there seems to be another sperm Ca^<2+> oscillation factor as well as PLC in porcine sperm extraction. Notably, we detected proteolytic fragments of PLCζ, presumably corresponding to cleaved forms of PLC, have the [Ca^<2+>]i oscillation-inducing activity of sperm when fragments exist together.
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