CALMODULIN-DEPENDENT PROTEIN KINASE-II MEDIATES INACTIVATION OF MPF AND CSF UPON FERTILIZATION OF XENOPUS EGGS
CALMODULIN-DEPENDENT PROTEIN KINASE-II MEDIATES INACTIVATION OF MPF AND CSF UPON FERTILIZATION OF XENOPUS EGGS
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DOI：
10.1038/366270a0
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发表时间：
1993-11-18
期刊：
影响因子：
64.8
通讯作者：
DOREE, M
中科院分区：
文献类型：
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作者：
LORCA, T;CRUZALEGUI, FH;DOREE, M
在脊椎动物中，未受精卵在第二次减数分裂中期被一种细胞抑制因子(CSF)1阻止，其基本成分是c-mos原癌基因2的产物。CSF阻止依赖泛素的有丝分裂周期蛋白的降解，从而使M期促进因子(MPF)3，4失活。受精或孤雌生殖激活触发细胞质内游离钙的一过性增加(参考文献5和6)，使CSF和MPF失活，并从减数分裂中期停滞中释放卵子7-10。当游离钙浓度在生理微摩尔范围内短暂升高时，从中期II受阻卵子制备的无细胞提取物(脑脊液提取物)需要钙调素依赖的过程才能发生周期蛋白降解。在这里，我们表明，当钙调素依赖的蛋白激酶II的结构性活性突变体(CaM K(II))被添加到脑脊液提取物中时，即使在没有钙离子的情况下也会发生细胞周期蛋白降解和CDc2激酶失活，并且当被转移到胚胎中时，提取物失去了导致中期停滞的能力。此外，CaM K(II)的特异性抑制剂可阻止钙添加后细胞周期蛋白的降解。最后，向未受精卵中直接微量注射具有结构性活性的CaM K(II)，即使在没有钙瞬变的情况下，也可以使CDC2激酶和CSF失活。因此，钙-钙调蛋白的靶标是CaM K(II)。
IN vertebrates, unfertilized eggs are arrested at second meiotic metaphase by a cytostatic factor (CSF)1, an essential component of which is the product of the c-mos proto-oncogene2. CSF prevents ubiquitin-dependent degradation of mitotic cyclins and thus inactivation of the M phase-promoting factor (MPF)3,4. Fertilization or parthenogenetic activation triggers a transient increase in the cytoplasmic free Ca2+ (reviewed in refs 5 and 6), inactivates both CSF and MPF, and releases eggs from meiotic metaphase arrest7-10. A calmodulin-dependent process is required for cyclin degradation to occur in cell-free extracts prepared from metaphase II-arrested eggs (CSF extracts) when the free Ca2+ concentration is transiently raised in the physiological micromolar range10. Here we show that when a constitutively active mutant of calmodulin-dependent protein kinase II (CaM K(II)) is added to a CSF extract, cyclin degradation and Cdc2 kinase inactivation occur even in the absence of Ca2+, and the extract loses its ability to cause metaphase arrest when transferred into embryos. Furthermore, specific inhibitors of CaM K(II) prevent cyclin degradation after calcium addition. Finally, the direct microinjection of constitutively active CaM K(II) into unfertilized eggs inactivates Cdc2 kinase and CSF, even in the absence of a Ca2+ transient. The target for Ca2+-calmodulin is thus CaM K(II).