Activation of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase by G protein and tyrosine kinase oncoproteins.
Activation of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase by G protein and tyrosine kinase oncoproteins.
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DOI：
10.1016/s0021-9258(17)46789-5
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发表时间：
1993-08
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影响因子：
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通讯作者：
Anne M. Gardner;R. Vaillancourt;Gary L. Johnson;Gary L. Johnson
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文献类型：
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作者：
Anne M. Gardner;R. Vaillancourt;Gary L. Johnson;Gary L. Johnson
丝裂原活化蛋白激酶（MAPK）在许多不同细胞类型中响应于多种细胞外刺激而迅速磷酸化和活化。活化MAPK的激酶，MAPK/ERK激酶（MEK），也通过磷酸化活化。我们研究了特定癌基因对NIH3T3和Rat1a成纤维细胞中MEK活性调节的影响。我们发现，一个类似的MEK活性磷酸化和激活MAPK在生长因子刺激（表皮生长因子和凝血酶）和癌基因（gip2，v-src和v-raf）转染细胞。Gip2和v-Src在转染的Rat 1a细胞中激活MEK-1，而v-Raf在转染的NIH 3T3细胞中激活MEK-1。MEK活化的这些细胞选择性差异与这些细胞系中的组成性MAPK活化平行。V-ras癌基因的稳定表达导致两种细胞系中几乎没有组成性MEK活化，即使两者都高度转化。生长因子和癌蛋白调节的MEK活性通过Mono S层析与45-kDa MEK-1蛋白共分级分离。我们进一步证明在NIH3T3和大鼠1a细胞中，Raf-1被激活，如通过其磷酸化MEK-1的能力所测量的，响应于表皮生长因子而不是凝血酶。因此，激活MAPK的蛋白激酶的调节网络在MEK处会聚，但与磷酸化和激活MEK的激酶发散。
Mitogen-activated protein kinases (MAPKs) are rapidly phosphorylated and activated in response to a variety of extracellular stimuli in many different cell types. The kinases that activate MAPK, the MAPK/ERK Kinases (MEKs), are also activated by phosphorylation. We have studied the influence of specific oncogenes on the regulation of MEK activity in NIH3T3 and Rat1a fibroblasts. We show that a similar MEK activity phosphorylates and activates MAPK in both growth factor-stimulated (epidermal growth factor and thrombin) and oncogene (gip2, v-src, and v-raf)-transfected cells. Gip2 and v-Src activated MEK-1 in transfected Rat 1a cells, whereas v-Raf activated MEK-1 in transfected NIH3T3 cells. These cell-selective differences in MEK activation parallel constitutive MAPK activation in these cell lines. Stable expression of the v-ras oncogene resulted in little constitutive MEK activation in either cell line, even though both were highly transformed. The growth factor and oncoprotein regulated MEK activity co-fractionated by Mono S chromatography with the 45-kDa MEK-1 protein. We further demonstrate in NIH3T3 and Rat 1a cells that Raf-1 is activated, as measured by its ability to phosphorylate MEK-1, in response to epidermal growth factor but not thrombin. Thus, the regulatory network of protein kinases that activate MAPK converges at MEK but diverges with the kinases that phosphorylate and activate MEK.