Involvement of the ERK signaling cascade in protein kinase C-mediated cell cycle arrest in intestinal epithelial cells
Involvement of the ERK signaling cascade in protein kinase C-mediated cell cycle arrest in intestinal epithelial cells
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DOI：
10.1074/jbc.m312268200
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发表时间：
2004-03-05
影响因子：
4.8
通讯作者：
Black, JD
中科院分区：
文献类型：
--
作者：
Clark, JA;Black, AR;Black, JD
我们之前报道过蛋白激酶C （PKC）信号可以介导IEC-18非转化肠隐窝细胞的细胞周期退出程序，包括细胞周期蛋白D1的快速消失，Cip/Kip细胞周期蛋白依赖性激酶抑制剂的表达增加，以及口袋蛋白生长抑制功能的激活（Frey， M. R., Clark， J. a ., Leontieva， O., Uronis， J. M., Black, a . R.和Black， J. D.（2000）细胞生物学杂志，151,763 - 777）。在目前的研究中，我们提供证据支持PKC α在介导这些作用中的必要作用。此外，对PKC/PKC α激活与细胞周期调节机制变化相关的信号事件的分析涉及Ras/Raf/MEK/ERK级联。PKC/PKC α活性促进Ras的GTP负载、Raf-1的激活和ERK的磷酸化/激活。研究发现，ERK激活是PKC/PKC α激活的关键下游效应所必需的，包括cyclin D1下调、p21（Waf1/Cip1）诱导和细胞周期阻滞。PKC诱导的ERK激活相对于增殖信号产生的激活是强烈和持续的，当这些相反的刺激同时给予时，PKC激动剂的生长抑制作用优于增殖事件。PKC信号传导促进了ERK活性的细胞质和细胞核积累，而生长因子诱导的磷酸化ERK仅局限于细胞质中。比较PKC激动剂在IEC-18细胞中维持PKC α激活和生长停滞的能力不同的作用，以及选择性激酶抑制剂的使用，表明PKC介导的细胞周期退出的长度取决于输入信号的大小/持续时间（即PKC α活性）和ERK级联的激活。磷酸化- erk核定位的程度/持续时间也可能是PKC激动剂诱导的生长停滞持续时间的重要决定因素。综上所述，这些数据表明PKC α和Ras/Raf/MEK/ERK级联是肠上皮细胞细胞周期退出的关键调节因子。
We have reported previously that protein kinase C (PKC) signaling can mediate a program of cell cycle withdrawal in IEC-18 nontransformed intestinal crypt cells, involving rapid disappearance of cyclin D1, increased expression of Cip/Kip cyclin-dependent kinase inhibitors, and activation of the growth suppressor function of pocket proteins (Frey, M. R., Clark, J. A., Leontieva, O., Uronis, J. M., Black, A. R., and Black, J. D. (2000) J. Cell Biol. 151, 763 - 777). In the current study, we present evidence to support a requisite role for PKC alpha in mediating these effects. Furthermore, analysis of the signaling events linking PKC/PKC alpha activation to changes in the cell cycle regulatory machinery implicate the Ras/Raf/MEK/ERK cascade. PKC/PKC alpha activity promoted GTP loading of Ras, activation of Raf-1, and phosphorylation/activation of ERK. ERK activation was found to be required for critical downstream effects of PKC/PKC alpha activation, including cyclin D1 down-regulation, p21(Waf1/Cip1) induction, and cell cycle arrest. PKC-induced ERK activation was strong and sustained relative to that produced by proliferative signals, and the growth inhibitory effects of PKC agonists were dominant over proliferative events when these opposing stimuli were administered simultaneously. PKC signaling promoted cytoplasmic and nuclear accumulation of ERK activity, whereas growth factor-induced phospho-ERK was localized only in the cytoplasm. Comparison of the effects of PKC agonists that differ in their ability to sustain PKC alpha activation and growth arrest in IEC-18 cells, together with the use of selective kinase inhibitors, indicated that the length of PKC-mediated cell cycle exit is dictated by the magnitude/duration of input signal (i.e. PKC alpha activity) and of activation of the ERK cascade. The extent/duration of phospho-ERK nuclear localization may also be important determinants of the duration of PKC agonist-induced growth arrest in this system. Taken together, the data point to PKC alpha and the Ras/Raf/MEK/ERK cascade as key regulators of cell cycle withdrawal in intestinal epithelial cells.