2003 Fiscal Year Final Research Report Summary
The role of calcium-mobilizing signal transduction system in fertilization
| Project/Area Number |
14380302
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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 Science (2003)
The University of Tokyo (2002) |
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Principal Investigator |
FUKAMI Kiyoko Tokyo University of Pharmacy and Life Science, School of Life Science, Professor, 生命科学部, 教授 (40181242)
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| Project Period (FY) |
2002 – 2003
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| Keywords | fertilization / calcium / Phosphatidyl inositol turnover / Phospholipase C / acrosome reaction |
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| Research Abstract |
Zona-Pellucida(ZP)-induced acrosome reaction in sperm is a required step for mammalian fertilization. However, the precise mechanism of the acrosome reaction remains unclear. We previously reported that Phospholipase C delta 4 (PLCδ4) is involved in ZP-induced acrosome reaction in mouse sperm. Here we have monitored Ca^<2+> responses in single sperm, and we report that the [Ca^<2+>]_i increase in response to ZP, which is essential for driving the acrosome reaction in vivo, is absent in PLCδ4^<-/-> sperm. Progesterone, another physiological inducer of the acrosome reaction, failed to induce sustained [Ca^<2+>]_i increases in PLCδ4^<-/-> sperm and consequently the acrosome reaction was partially inhibited. In addition, we observed oscillative [Ca^<2+>]_i increases in wild-type sperm in response to these acrosome inducers. Calcium imaging studies revealed that the [Ca^<2+>]_i increases induced by exposure to ZP and progesterone started at different sites within the sperm head, indicating that these agonists induce the acrosome reaction via different Ca^<2+> mechanisms. Furthermore, store-operated channel (SOC) activity was severely impaired in PLCδ4^<-/-> sperm. These results indicate that PLCδ4 is an important enzyme for intracellular [Ca^<2+>]_i mobilization in ZP-induced acrosome reaction and for sustained [Ca^<2+>]_i increases through SOC induced by ZP and progesterone in sperm.
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