Cooperative regulation of the cell division cycle by the protein kinases RAF and AKT
Cooperative regulation of the cell division cycle by the protein kinases RAF and AKT
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DOI：
10.1128/mcb.24.24.10868-10881.2004
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发表时间：
2004-12-01
影响因子：
5.3
通讯作者：
McMahon, M
中科院分区：
文献类型：
--
作者：
Mirza, AM;Gysin, S;McMahon, M
ras激活的RAF—>MEK—>细胞外信号调节激酶（ERK）和磷脂酰肌醇3′-激酶（PI3′-激酶）—>PDK1—>AKT信号通路被认为协同促进正常细胞的增殖和癌细胞的异常增殖。为了探索这种合作背后的机制，我们获得了含有条件活性、类固醇激素调节形式的RAF和AKT的细胞。这些细胞允许评估这些蛋白激酶单独或相互联合激活的生物学和生化效应。在既不单独激活RAF也不单独激活AKT促进s期进展的条件下，两种激酶的共激活引发了强烈的增殖反应。此外，在高水平激活RAF诱导G、细胞周期阻滞的条件下，AKT的激活绕过阻滞并促进s期进展。在细胞周期机制层面，RAF和AKT共同诱导cyclin D1，抑制p27（Kip1）的表达。p27（Kip1）的抑制伴随着Kip1 mRNA的急剧减少，并且在缺乏SKP2或表达T187A突变形式的p27（Kip1）的小鼠衍生的原代小鼠胚胎成纤维细胞中观察到。与这些观察结果一致，在NIH 3T3成纤维细胞和一组真正的人胰腺癌细胞系中，药理抑制MEK或PI3'-激酶抑制了活化的RAS对p27（Kip1）表达的影响。此外，我们证明AKT激活导致cyclin/cdk2复合物的持续激活，伴随着raf诱导的p21（Cip1）从cyclin E/cdk2复合物中去除。综上所述，这些数据强烈提示RAF—>MEK—>ERK和pi3’k—>PDK—>AKT信号通路可以协同促进正常细胞和癌细胞中G(0)—>G(1)—> s期细胞周期的进展。
The RAS-activated RAF-->MEK-->extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3'-kinase (PI3'-kinase)-->PDK1-->AKT signaling pathways are believed to cooperate to promote the proliferation of normal cells and the aberrant proliferation of cancer cells. To explore the mechanisms that underlie such cooperation, we have derived cells harboring conditionally active, steroid hormone-regulated forms of RAF and AKT. These cells permit the assessment of the biological and biochemical effects of activation of these protein kinases either alone or in combination with one another. Under conditions where activation of neither RAF nor AKT alone promoted S-phase progression, coactivation of both kinases elicited a robust proliferative response. Moreover, under conditions where high-level activation of RAF induced G, cell cycle arrest, activation of AKT bypassed the arrest and promoted S-phase progression. At the level of the cell cycle machinery, RAF and AKT cooperated to induce cyclin D1 and repress p27(Kip1) expression. Repression of p27(Kip1) was accompanied by a dramatic reduction in KIP1 mRNA and was observed in primary mouse embryo fibroblasts derived from mice either lacking SKP2 or expressing a T187A mutated form of p27(Kip1). Consistent with these observations, pharmacological inhibition of MEK or PI3'-kinase inhibited the effects of activated RAS on the expression of p27(Kip1) in NIH 3T3 fibroblasts and in a panel of bona fide human pancreatic cancer cell lines. Furthermore, we demonstrated that AKT activation led to sustained activation of cyclin/cdk2 complexes that occurred concomitantly with the removal of RAF-induced p21(Cip1) from cyclin E/cdk2 complexes. Cumulatively, these data strongly suggest that the RAF-->MEK-->ERK and PI3'K-->PDK-->AKT signaling pathways can cooperate to promote G(0)-->G(1)-->S-phase cell cycle progression in both normal and cancer cells.