Han J K, Lee S K
Department of Life Sciences, Pohang University of Science and Technology, South Korea.
Biochem Biophys Res Commun. 1995 Dec 26;217(3):931-9. doi: 10.1006/bbrc.1995.2860.
In this report, we investigated the possibility that a product of phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown, inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), and its downstream effector, Ca2+, is involved in oocyte maturation. Microinjection of monoclonal antibody specifically directed to PIP2 into oocytes prior to progesterone addition inhibited meiotic maturation. In addition, preventing or suppressing the progesterone-induced increase in [Ca2+]i and maintaining cytosolic free Ca2+ of oocyte at 0.1 or 0.3 microM by Br2-BAPTA buffered Ca2+ solutions, completely blocked maturation. However, raising cytosolic Ca2+ concentration of oocyte to 1.0 or 3.0 microM, the inhibitory Br2-BAPTA effects on oocyte maturation was greatly diminished. Finally, microinjection of heparin, a potent antagonist of Ins(1,4,5)P3 receptor, inhibited progesterone-induced oocyte maturation in a manner that is linearly proportional to its cytoplasmic concentration. These results strongly support the hypothesis that PIP2 turnover as well as Ins(1,4,5)P3-induced Ca2+ release play crucial roles in regulating normal meiotic cell division in Xenopus oocyte.
在本报告中，我们研究了磷脂酰肌醇4,5-二磷酸（PIP2）分解产物肌醇1,4,5-三磷酸（Ins(1,4,5)P3）及其下游效应物Ca2+参与卵母细胞成熟的可能性。在添加孕酮之前，将特异性针对PIP2的单克隆抗体显微注射到卵母细胞中可抑制减数分裂成熟。此外，通过Br2-BAPTA缓冲Ca2+溶液防止或抑制孕酮诱导的[Ca2+]i升高，并将卵母细胞的胞质游离Ca2+维持在0.1或0.3微摩尔，可完全阻断成熟。然而，将卵母细胞的胞质Ca2+浓度提高到1.0或3.0微摩尔，Br2-BAPTA对卵母细胞成熟的抑制作用会大大减弱。最后，显微注射肝素（一种有效的Ins(1,4,5)P3受体拮抗剂）以与其细胞质浓度成线性比例的方式抑制孕酮诱导的卵母细胞成熟。这些结果有力地支持了以下假设：PIP2周转以及Ins(1,4,5)P3诱导的Ca2+释放对非洲爪蟾卵母细胞正常减数分裂细胞分裂的调节起着关键作用。
