RAF-1 ACTIVATES MAP KINASE-KINASE
RAF-1 ACTIVATES MAP KINASE-KINASE
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DOI：
10.1038/358417a0
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发表时间：
1992-07-30
期刊：
影响因子：
64.8
通讯作者：
AVRUCH, J
中科院分区：
文献类型：
--
作者：
KYRIAKIS, JM;APP, H;AVRUCH, J
急性转化癌基因v-raf的正常细胞同源物是c-raf-1，它编码一种丝氨酸/苏氨酸蛋白激酶，可被多种细胞外刺激激活1。蛋白质c-Raf-1的生理底物是未知的。有丝分裂原活化蛋白（MAP）激酶Erk 1和2也被有丝分裂原通过Erk酪氨酸和苏氨酸残基的磷酸化活化，该磷酸化由相对分子量为50，000的蛋白激酶MAP激酶-激酶（MAPK-K）2-7催化。在这里，我们报告，MAPK-K以及Erk 1和2是组成型活性的v-raf转化细胞。从v-raf转化细胞或有丝分裂原处理的细胞3中部分纯化的MAPK-K可以被磷酸酶2A灭活。在体外，经丝裂原刺激后纯化的c-Raf-1可使磷酸酶2A失活的MAPK-K再活化30倍以上。MAPK-K的c-Raf-1再活化与M（r）50，000的多肽的丝氨酸/苏氨酸残基的选择性磷酸化一致，所述多肽在阳离子交换色谱上与可被c-Raf-1活化的MAPK-K精确共洗脱。这些结果表明c-Raf-1是体内MAPK-K的直接上游激活剂。据我们所知，MAPK-K是第一个被鉴定的c-raf-1原癌基因产物的生理底物。
THE normal cellular homologue of the acutely transforming oncogene v-raf is c-raf-1, which encodes a serine/threonine protein kinase that is activated by many extracellular stimuli1. The physiological substrates of the protein c-Raf-1 are unknown. The mitogen-activated protein (MAP) kinases Erk1 and 2 are also activated by mitogens through phosphorylation of Erk tyrosine and threonine residues catalysed by a protein kinase of relative molecular mass 50,000, MAP kinase-kinase (MAPK-K)2-7. Here we report that MAPK-K as well as Erk1 and 2 are constitutively active in v-raf-transformed cells. MAPK-K partially purified from v-raf-transformed cells or from mitogen-treated cells3 can be deactivated by phosphatase 2A. c-Raf-1 purified after mitogen stimulation can reactivate the phosphatase 2A-inactivated MAPK-K over 30-fold in vitro. c-Raf-1 reactivation of MAPK-K coincides with the selective phosphorylation at serine/threonine residues of a polypeptide with M(r) 50,000 which coelutes precisely on cation-exchange chromatography with the MAPK-K activatable by c-Raf-1. These results indicate that c-Raf-1 is an immediate upstream activator of MAPK-K in vivo. To our knowledge, MAPK-K is the first physiological substrate of the c-raf-1 protooncogene product to be identified.