Analyses on follicular growth mechanisms, focusing on tyrosine phosphatases that are involved in cell survival and death.

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 16380196
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Basic veterinary science/Basic zootechnical science
• Research Institution: University of Tsukuba
• Principal Investigator: MIYAZAKI Hitoshi University of Tsukuba, Graduate School of Life and Environmental Sciences, Professor (40183636)
• Co-Investigator(Kenkyū-buntansha): KANAI Yukio University of Tsukuba, Graduate School of Life and Environmental Sciences, Professor (40015871)
• Project Period (FY): 2004 – 2006
• Keywords: tyrosine phosphatase / follicular grwoth / granulose cells

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.

Research Products

• [Journal Article] Effect of direct ovarian injection of vascular endothelial growth factor gene fragments on follicular development in immature female rats (2007)
  • Author(s): Shimizu, T, Iijima, K, Miyabayashi, K, Ogawa, Y, Miyazaki, H, Sasada, H, Sato, E.
  • Journal Title: Reproduction 134 Pages: 677-682
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Protein phosphatase LMW-PTP exhibits opposite roles between vascular endothelial and smooth muscle cells (2005)
  • Author(s): Shimizu, H., Toyama, O., Shiota, M., Kim-Mitsuyama, S., Miyazaki, H.
  • Journal Title: J. Recept. Signal. Transd. 25 Pages: 19-33
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Receptor-Type Protein Tyrosine Phosphatase epsilon(PTPepsilonM) is a Negative Regulator of Insulin Signaling in Primary Hepatocytes and Liver (2005)
  • Author(s): Nakagawa, Y., Aoki, N., Aoyama, K., Shimizu, H., Shimano, H., Yamada, N., Miyazaki, H.
  • Journal Title: Zool. Sci. 25 Pages: 169-175
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Heat stress diminishes gonadotropin receptor expression and enhances susceptibility to apoptosis of rat granulosa cells (2005)
  • Author(s): Shimizu, T., Ohshima, I., Ozawa, M., Takahashi, S., Tajima, A., Shiota, M., Miyazaki, H., Kanai, Y.
  • Journal Title: Reproduction 129 Pages: 463-472
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Tyrosine phosphatase epsilonM stimulates migration and survival of porcine aortic endothelial cells by activating c-Src. (2004)
  • Author(s): Nakagawa, Y., Yamada, N., Shimizu, H., Shiota, M., Tamura, M., Kim-Mitsuyama, S., Miyazaki, H.
  • Journal Title: Biochem. Biophys Res. Commun. 325 Pages: 314-319
  • Description: 「研究成果報告書概要(欧文)」より