Xenopus oocytes and the biochemistry of cell division.
Xenopus oocytes and the biochemistry of cell division.
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非洲爪蟾卵母细胞和细胞分裂的生物化学。
DOI：
10.1021/bi00465a001
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Maller,JL
中科院分区：
文献类型：
--
作者：
Maller,JL
科罗拉多大学医学院药理学系，丹佛，科罗拉多州 80262 收稿日期：1989 年 9 月 19 日；修订稿于 1989 年 10 月 27 日收到摘要：细胞增殖的控制涉及质膜启动的调节事件（控制重新进入细胞周期）和细胞内生化变化（指导细胞分裂本身的过程）。细胞生长控制的这两个方面都可以在响应有丝分裂刺激而经历减数分裂成熟的非洲爪蟾卵母细胞中进行研究。迄今为止发现的所有促有丝分裂信号通路都会导致核糖体蛋白 S6 丝氨酸残基的磷酸化，并且已经研究了该事件的生物化学。胰岛素和其他有丝分裂原可激活核糖体蛋白 S6 激酶 II，该蛋白已在卵母细胞和其他细胞中进行克隆和测序。这种酶是通过胰岛素刺激的蛋白激酶（称为 MAP-2 激酶）对丝氨酸和苏氨酸残基进行磷酸化来激活的。 MAP激酶本身也可以通过体内苏氨酸和酪氨酸残基的直接磷酸化来激活。这些结果重建了胰岛素信号传导途径的一个步骤，该途径在胰岛素受体在膜上结合后不久就很明显。有丝分裂刺激后几个小时，细胞周期细胞质控制元件被激活，足以导致进入 M 期。这种控制元件被称为成熟促进因子或 MPF，已被纯化至接近均质，并显示由 p34cdc2 蛋白激酶和细胞周期蛋白 B2 之间的复合物组成。除了细胞周期蛋白的明显磷酸化之外，MPF 活性的调节还涉及细胞周期蛋白亚基的合成及其在中期过渡阶段的周期性降解。 p34edc2 激酶亚基通过苏氨酸和酪氨酸残基的磷酸化/去磷酸化来调节，磷酸化时不活跃，去磷酸化时活跃。对 p34cdc2 组蛋白 HI 中磷酸化位点的分析揭示了 (K/R) s/xP (X) K/R 的共有序列，其中括号中的元素存在于某些位点但不是所有位点中。具有这种共有位点的位点在有丝分裂中被特异地磷酸化并且被原癌基因pp60<>，rc.中的MPF磷酸化。这些结果提供了细胞周期控制和细胞生长控制之间的联系，并表明细胞粘附和有丝分裂中细胞骨架的变化可能通过原癌基因激活而受到 MPF 的间接调节。 S6 激酶 II 在细胞中表达 MPF 时也会被激活，表明 MPF 是有丝分裂信号通路上 S6 激酶的上游。进一步研究导致 MPF 激活的信号事件和 MPF 磷酸化的底物应该有助于全面了解细胞分裂的生物化学。
Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80262 Received September 19, 1989; Revised Manuscript Received October 27, 1989 abstract: The control of cell proliferation involves bothregulatory events initiated at theplasma membrane that control reentry into thecell cycle and intracellular biochemical changes that direct the process of cell division itself. Both of these aspects of cell growth control can be studied in Xenopus oocytes undergoing meiotic maturation in response to mitogenic stimulation. All mitogenic signaling pathways so far identified lead to the phosphorylation of ribosomal protein S6 on serine residues, and the biochemistry of this event has been investigated. Insulin and other mitogens activate ribosomal protein S6 kinase II, which has been cloned and sequenced in oocytes and other cells. This enzyme is activated by phosphorylation on serine and threonine residues by an insulin-stimulated protein kinase known as MAP-2 kinase. MAP kinase itself is also activated bydirect phosphorylation on threonine and tyrosine residues in vivo. These results reconstitute one step of the insulin signaling pathway evident shortly after insulin receptor binding at the membrane. Several hours after mitogenic stimulation, a cell cycle cytoplasmic control element is activated that is sufficient to cause entry into M phase. This control element, known as maturation-promoting factor or MPF, has been purified to near homogeneity and shown to consist of a complex between p34cdc2 protein kinase and cyclin B2. In addition to apparent phosphorylation of cyclin, regulation of MPF activity involves synthesis of the cyclin subunit and its periodic degradation at the metaphaseanaphase transition. The p34edc2 kinase subunit is regulated by phosphorylation/dephosphorylation on threonine and tyrosine residues, being inactive when phosphorylated and active when dephosphorylated. Analysis of phosphorylation sites in histone HI for p34cdc2 has revealed a consensus sequence of (K/R) s/xP (X) K/R, where the elements in parentheses are present in some but not all sites. Sites with such a consensus are specifically phosphorylated in mitosis and by MPF in the protooncogene pp60<>, rc. These results provide a link between cell cycle control and cell growth control and suggest that changes in cell adhesion and the cytoskeleton in mitosismay be regulated indirectly by MPF via protooncogene activation. S6 kinase II is also activated upon expression of MPF in cells, indicating that MPF is upstream of S6 kinase on the mitogenic signaling pathway. Further study both of the signaling events that lead to MPF activation and of the substrates for phosphorylationby MPF should lead to a comprehensive understanding of the biochemistry of cell division.