海星卵母細胞成熟期間PRK2調節機制之探討﹝3/3﹞

海星卵中內蛋白磷酸脢C 二號相關磷酸脢 (Protein kinase C-related kinase 2, PRK2)的 活性在海星卵在成熟前被活化，使PRK2 被認為是調節海星卵成熟的可能因子。因此我們 在本研究中探討在體外試驗中被證明為PRK2 活化因子之Rho 及LPA 對海星卵PRK2 活性 及海星卵核成熟之影響。結果卻顯示Rho 及LPA 對海星卵PRK2 活性及海星卵核成熟均無 影響，其可能原因是其他因子亦參與這些過程之調節，而使試驗效果無法顯著，或PRK2 真的與海星卵核成熟無關。為進一步釐清，我們製作了可抑制或活化PRK2 的PRK2 變種 重組蛋白，並研究其對海星卵核成熟之影響，結果證明PRK2 變種重組蛋白對海星卵核成 熟無任何影響，綜合以上結果我們認為PRK2 並非調節海星卵成熟的因子。然而為何PRK2 的活性在海星卵在成熟前被活化，其可能原因乃為蛋白質的新生成及後續胚發育過成程之 細胞骨架重組作準備，而一些初步試驗證明PRK2 活性在腔腸胚形成前會降低，是否PRK2 活性與海星腔腸化過程中細胞遷徙有關則有賴進一步試驗證明！PRK2 has been suggested to involve in the regulation of meiotic maturation in starfish oocytes as evident by its activation prior to germinal vesicle breakdown (GVBD). In this study, we have tested the upstream regulators of PRK2, including Rho and LPA as well as PRK2 recombinant mutants on their effects on the regulation of PRK2 activity and the nuclear maturation during meiotic maturation in starfish oocytes. A Rho inhibitor C3 exoenzyme and a Rho activator LPA failed to affect PRK2 hyperphosphorylation and GVBD. It suggests that either Rho is not involved or other factors may compensate the activation of PRK2. Directly modulating PRK2 activity by dominant-negative or constitutively active PRK2 did not affect the GVBD. These results rule out the possibility of involvement PRK2 in nuclear maturation. Preliminary data showed the down-regulation of PRK2 phosphorylation prior to gastrulation. It implies a role of PRK2 in mediating cellular migration during gastrulation