| Budget Amount *help |
¥15,400,000 (Direct Cost: ¥15,400,000)
Fiscal Year 2006: ¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 2004: ¥6,700,000 (Direct Cost: ¥6,700,000)
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| Research Abstract |
The protein tyrosine phosphorylation of intracellular signaling molecules by protein tyrosine kinases (PTKs) in ovarian granulose cells is significant for regulating the dynamics of follicular atresia, growth, and maturation. Although phosphotyrosine (p-Tyr) levels are regulated by the coordinated activities of PTKs and protein tyrosine phosphatases (PTPs), the roles of PTPs are poorly understood for controlling follicular functions. We identified the existence of 25 PTPs in granulose cells. Some of them including PTPeM and PTP20 showed dramatic changes in their expression levels during the estrus cycle. PTPeM is highly and weakly expressed in the atretic and healthy follicles, respectively, suggesting that this phosphatase may be involved in the progression of atresia accompanying apoptosis of granulose cells. Therefore, this report focuses on the role of PTPeM in the ovary.
We obtained the following results. First, overexpression of PTPeM induced retraction of the cell body with the extension of long, dendritic-like processes, decreased cell adhesion to the substratum, and then induced apoptosis. Second, actin fibers disappeared by PTPeM overexpression with a decrease in Rho activity that plays a key role for the substratum-dependent formation of actin fibers. Third, the Rho kinase inhibitor Y27632 showed the similar morphological changes and apoptosis of these cells as PTPeM overexpression. Fourth, PTPeM decreased the phosphorylation level of Tyr925 and Tyr576/ 577 of focal adhesion kinase (FAK) whose phosphorylation is critically involved in the formation of cell adhesion and actin fibers. Fifth, PTPeM coimmunoprecipitated with FAK. These data demonstrate that PTPeM induces anoikis of granulosa cells by dephosphorylating FAK with a decrease in Rho activity. Therefore, PTPeM maybe an important PTP that mediates atresia. Our data suggest that PTPs play significant roles in controlling the dynamics of ovarian functions.
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