The pure inhibitor of cAMP-dependent protein kinase initiates Xenopus laevis meiotic maturation A 4-step scheme for meiotic maturation
The pure inhibitor of cAMP-dependent protein kinase initiates Xenopus laevis meiotic maturation A 4-step scheme for meiotic maturation
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cAMP 依赖性蛋白激酶的纯抑制剂启动非洲爪蟾减数分裂成熟 减数分裂成熟的 4 步方案
DOI：
10.1016/0303-7207(81)90092-7
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发表时间：
1981
影响因子：
4.1
通讯作者：
J. Demaille
中科院分区：
文献类型：
--
作者：
D. Huchon;R. Ozon;E. Fischer;J. Demaille
cAMP依赖性蛋白激酶的纯抑制剂的可用性促使重新检查的cardior-induced减数分裂成熟ofXenopus laevisoocytes。注射抑制剂（1.5 μM）触发100%的萌发囊泡破裂比孕酮快，比促成熟因子慢：在0.15 μM时，抑制剂仍然触发100%的减数分裂，但动力学慢得多。相比之下，注射24 μM钙调素导致小于50%的GVBD，并且结果因雌性而异。抑制剂和钙调蛋白的联合注射未能显示任何协同作用，这不利于钙调蛋白通过激活环核苷酸磷酸二酯酶起作用的假设。抑制剂的净效应是降低cAMP依赖性蛋白激酶的游离催化亚基的浓度，其在未刺激的卵母细胞中完全解离，如用霍乱毒素预处理对大肠杆菌诱导的成熟没有影响所示。在这种减少约1 μM后，成熟蛋白Mp-P被磷蛋白磷酸酶去磷酸化。脱磷酸-Mp在环己酰亚胺敏感步骤中触发MPF的合成。最后，MPF在对放线菌酮不敏感的步骤中触发GVBD。这样一个4步骤的计划下降cAMP水平，然后在C亚单位水平，MP的去磷酸化导致MPF的合成，最后MPF触发GVBD的证据，并进行了讨论。
The availability of the pure inhibitor of cAMP-dependent protein kinase prompted a re-examination of the inhibitor-induced meiotic maturation ofXenopus laevisoocytes. Injection of the inhibitor (1.5 μM) triggered 100% germinal vesicle breakdown faster than progesterone and slower than the maturation-promoting factor: at 0.15 μM, the inhibitor still triggered 100% meiosis, but with a much slower kinetics. In contrast, injection of 24 μM calmodulin resulted in less than 50% GVBD, and results were variable from female to female. Combined injection of inhibitor and calmodulin failed to show any synergism, which does not favour hypotheses according to which calmodulin acts by activation of cyclic nucleotide phosphodiesterase.The net effect of the inhibitor is to decrease the concentration of the free catalytic sub-unit of cAMP-dependent protein kinase, fully dissociated in the unstimulated oocyte, as shown by the absence of effect of pretreatment with cholera toxin on the inhibitor-induced maturation. After such decrease by about 1 μM, a maturation protein, Mp-P, is dephosphorylated by phosphoprotein phosphatases. Dephospho-Mp triggers the synthesis of MPF in cycloheximide-sensitive steps. Finally, MPF triggers GVBD in steps insensitive to cycloheximide. Evidence for such a 4-step scheme—fall in cAMP levels, then in C sub-unit levels, dephosphorylation of Mp leading to the synthesis of MPF and finally MPF-triggered GVBD—is presented and discussed.