Induction of p18(INK4c) and its predominant association with CDK4 and CDK6 during myogenic differentiation
Induction of p18(INK4c) and its predominant association with CDK4 and CDK6 during myogenic differentiation
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DOI：
10.1091/mbc.7.10.1587
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发表时间：
1996-10-01
影响因子：
3.3
通讯作者：
Xiong, Y
中科院分区：
文献类型：
--
作者：
Franklin, DS;Xiong, Y
细胞终末分化涉及细胞分裂周期的永久退出。细胞周期蛋白依赖性激酶 (CDK) 抑制剂是耦合细胞周期停滞和细胞分化的潜在分子。在小鼠 C2C12 成肌细胞中，G1 CDK 酶（CDK2、CDK4 和 CDK6）与四种 CDK 抑制剂相关：p18(INK4c)、p19(INK4d)、P21 和 p27(Kip1)。在诱导肌生成过程中，p21 及其相关 CDK 蛋白经历了最初的增加，然后随着细胞终末分化而减少。 p27蛋白水平逐渐升高，但相关CDK蛋白总量保持不变。 p19 蛋白及其相关的 CDK4 蛋白在分化过程中逐渐减少。相比之下，p18 蛋白增加了 50 倍，从增殖成肌细胞中可忽略不计的水平增加到生肌诱导 8-12 小时内清晰可检测的水平。最初的上升随后在诱导后 12 至 24 小时之间急剧增加，p18 蛋白最终在终末分化细胞中积累到最高水平。 p18 的诱导与复合物形成的增加和连续性相关——在肌原性分化过程中，首先增加与 CDK6 的关联，然后增加与 CDK4 的关联。在终末分化的 C2C12 细胞以及成年小鼠肌肉组织中，所有 CDK6 和一半 CDK4 与 p18 复合。最后，CDK2 和 CDK4 的激酶活性随着 C2C12 细胞的分化而降低，而 CDK6 激酶活性在增殖的成肌细胞和分化的肌管中均较低。我们的结果表明p18可能在引起和/或维持与成熟肌肉形成相关的永久细胞周期停滞中发挥关键作用。
Terminal cell differentiation involves permanent withdrawal from the cell division cycle. The inhibitors of cyclin-dependent kinases (CDKs) are potential molecules functioning to couple cell cycle arrest and cell differentiation. In murine C2C12 myoblast cells, G1 CDK enzymes (CDK2, CDK4, and CDK6) associate with four CDK inhibitors: p18(INK4c) p19(INK4d), P21, and p27(Kip1). During induced myogenesis, p21 and its associated CDK proteins underwent an initial increase followed by a decrease as cells became terminally differentiated. The level of p27 protein gradually increased, but the amount of total associated CDK proteins remained unchanged. p19 protein decreased gradually during differentiation, as did its associated CDK4 protein. In contrast, p18 protein increased 50-fold, from negligible levels in proliferating myoblasts to clearly detectable levels within 8-12 h of myogenic induction. This initial rise was followed by a precipitous increase between 12 and 24 h postinduction, with p18 protein finally accumulating to its highest level in terminally differentiated cells. Induction of p18 correlated with increased and sequential complex formation--first increasing association with CDK6 and then with CDK4 over the course of myogenic differentiation. All of the CDK6 and half of the CDK4 were complexed with p18 in terminally differentiated C2C12 cells as well as in adult mouse muscle tissue. Finally, kinase activity of CDK2 and CDK4 decreases as C2C12 cells differentiate, whereas the CDK6 kinase activity is low in both proliferating myoblasts and differentiated myotubes. Our results indicate that p18 may play a critical role in causing and/or maintaining permanent cell cycle arrest associated with mature muscle formation.