Protein synthesis is required for the transition to Ca(2+)-dependent regulated secretion in progesterone-matured Xenopus oocytes.
Protein synthesis is required for the transition to Ca(2+)-dependent regulated secretion in progesterone-matured Xenopus oocytes.
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在黄体酮成熟的非洲爪蟾卵母细胞中，蛋白质合成是过渡到 Ca(2) 依赖性调节分泌所必需的。
DOI：
10.1002/jez.a.10317
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Gundersen,CameronB
中科院分区：
文献类型：
--
作者：
Kohan,SirusA;Gundersen,CameronB
Calcium (Ca) ionophores trigger cortical granule exocytosis in progesterone‐matured Xenopus oocytes (eggs), but not in immature oocytes. Prior work suggested that this secretory transition involved a Ca‐dependent isoform of protein kinase C (PKC). To address this possibility, we treated eggs with several different inhibitors of Ca‐dependent PKCs. Although these agents (eg., staurosporine, Ro31–8220) completely blocked cortical granule exocytosis that is triggered in eggs by phorbol esters, they had no impact on ionomycin‐evoked secretion of cortical granule lectin. These data suggest that Ca‐dependent PKCs do not mediate secretory triggering in eggs. Instead, further investigation revealed that protein synthesis (but not RNA synthesis) was required for eggs to secrete in response to ionomycin. Moreover, we observed that when oocytes were matured by injection of maturation promoting factor (MPF), they failed to secrete in response to ionomycin. Collectively, these results suggest that the progesterone‐dependent maturation pathway induces these cells either to synthesize de novo, a protein that mediates Ca‐dependent secretory triggering, or that intrinsic Ca‐sensing machinery is modified in a protein‐synthesis‐dependent fashion. Initial efforts to distinguish between these possibilities (using Ca overlay, pharmacological and immunoblot strategies) revealed that such Ca‐binding proteins as calmodulin, synaptotagmin1, CAPS, rabphilin–3A and calcineurin were unlikely to transduce the secretory effects of ionomycin in eggs. Thus, the cortical reaction in these cells may rely on a novel mechanism for initiating Ca‐dependent exocytosis.J. Exp. Zool. 300A:113–125, 2003. © 2003 Wiley‐Liss, Inc.
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