Mitogen-activated protein kinase mediates luteinizing hormone-induced breakdown of communication and oocyte maturation in rat ovarian follicles
Mitogen-activated protein kinase mediates luteinizing hormone-induced breakdown of communication and oocyte maturation in rat ovarian follicles
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DOI：
10.1210/en.2004-1006
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发表时间：
2005-03-01
期刊：
影响因子：
4.8
通讯作者：
Dekel, N
中科院分区：
文献类型：
--
作者：
Sela-Abramovich, S;Chorev, E;Dekel, N
在LH诱导的减数分裂恢复之前，间隙连接通讯中断，这终止了cAMP从卵泡体细胞到卵母细胞的供应。最近的研究表明，LH诱导的减数分裂重新启动是由MAPK介导的;然而，参与这种酶作用的潜在分子机制仍然未知。我们假设MAPK的激活中断了卵泡内的连接通讯，进而导致卵母细胞成熟。为了验证这一假设，我们通过UO 126阻断MAPK的激活，UO 126特异性地抑制MAPK信号通路。我们使用三种互补的方法分析了连接通讯：1）膜片钳分析，确定两个相邻颗粒细胞之间的电耦合的变化; 2）刮片加载技术，监测染料通过颗粒细胞层的扩散; 3）代谢偶联试验，评价放射性标记的尿苷从卵丘细胞转移到卵母细胞。我们发现，在这里，体卵泡细胞，而不是卵母细胞，激活MAPK后立即暴露于LH。此外，抑制LH诱导的MAPK激活不仅可以阻止卵母细胞成熟，还可以阻止交界通讯的减少。此外，UO 126避免了两种磷酸化形式的差距连接蛋白连接蛋白43对LH的反应。我们的结论是，MAPK介导LH诱导的卵母细胞的成熟，中断细胞间的沟通，在卵巢卵泡，可能通过磷酸化连接蛋白43。
Resumption of meiosis, induced by LH, is preceded by the breakdown of gap junctional communication, which terminates the supply of cAMP from the somatic cells of the ovarian follicle to the oocyte. It has recently been shown that LH-induced reinitiation of meiosis is mediated by MAPK; however, the underlying molecular mechanism involved in the action of this enzyme remains unknown. We hypothesized that activation of MAPK interrupts junctional communication within the ovarian follicle, leading, in turn, to oocyte maturation. To test this hypothesis, we blocked the activation of MAPK by UO126, which specifically inhibits the MAPK signaling pathway. We analyzed junctional communication using three complementary methods: 1) patch-clamp analysis, which determined changes in the electrical coupling between two adjacent granulosa cells; 2) the scrape-loading technique, which monitored the spread of dyes through a granulosa cell layer; and 3) a metabolic coupling assay, which evaluated the transfer of radiolabeled uridine from the cumulus cells to the oocyte. We show, herein, that the somatic follicle cells, rather than the oocyte, activate MAPK immediately after their exposure to LH. Moreover, inhibition of LH-induced MAPK activation not only prevents oocyte maturation but also blocks the reduction in junctional communication. In addition, the appearance of the two phosphorylated forms of the gap junction protein, connexin 43, in response to LH, was avoided by UO126. We concluded that MAPK mediates LH-induced oocyte maturation by interrupting cell-to-cell communication within the ovarian follicle, possibly through phosphorylation of connexin 43.