Murine Ksr interacts with MEK and inhibits Ras-induced transformation
Murine Ksr interacts with MEK and inhibits Ras-induced transformation
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DOI：
10.1016/s0960-9822(98)70019-3
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发表时间：
1998-01-01
期刊：
影响因子：
9.2
通讯作者：
Eychène, A
中科院分区：
文献类型：
--
作者：
Denouel-Galy, A;Douville, EM;Eychène, A
背景：Ksr（Pas的激酶抑制因子）通过在果蝇和秀丽隐杆线虫中的遗传筛选被鉴定为Pas - MAP激酶（丝裂原活化蛋白激酶）通路的调节因子。Ksr是一种与Raf激酶的三个保守区域具有相似性的激酶，尤其在激酶结构域内。为了研究这些结构相似性是否与共同的功能特性相关，我们检测了Ksr的鼠同源物mKsr - 1与脊椎动物MAP激酶通路组分相互作用的能力。
结果：在酵母双杂交相互作用实验中，mKsr - 1不与Pas、B - Raf或Raf - 1结合，但与MAP激酶的激活因子MEK - 1和MEK - 2强烈相互作用。Ksr - MEK相互作用通过免疫共沉淀实验得到证实。在COS - 1细胞中，异位表达的mKsr - 1与内源性MEK - 1共沉淀，并且在PC12细胞中内源性Ksr和MEK共沉淀。然而，未检测到mKsr - 1对MEK的磷酸化。相反，在COS - 1细胞或PC12细胞中与mKsr - 1结合的MEK亚群没有显示激酶活性。Ksr以无活性形式阻断MEK的这种能力与一种生物学反应相关：mKsr - 1不会使NIH3T3细胞发生转化，而且，mKsr - 1降低了Pas诱导的转化。类似地，mKsr - 1抑制了由Pas和B - Raf诱导的胚胎神经视网膜细胞的增殖，但不抑制由MEK诱导的增殖。
结论：我们的结果表明Ksr在调节MAP激酶通路中存在一种新的机制，至少部分是通过其与MEK相互作用的能力。
Background: Ksr (kinase supressor of Pas) was identified as a regulator of the Pas-MAP kinase (mitogen-activated protein kinase) pathway by genetic screens in Drosophila and Caenorhabditis elegans, Ksr is a kinase with similarities to the three conserved regions of Raf kinases, especially within the kinase domain. To investigate whether these structural similarities correlated with common functional properties, we: examined the ability of mKsr-1, the murine homolog of Ksr, to interact with components of the vertebrate MAP kinase pathway.Results: In the yeast two-hybrid interaction assay, mKsr-1 did not bind to either Pas, B-Raf or Raf-1, but interacted strongly with both MEK-1 and MEK-2, activators of MAP kinase. The Ksr-MEK interaction was confirmed by co-immunoprecipitation experiments. Ectopically expressed mKsr-1 co-precipitated with endogenous MEK-1 in COS-l cells, and endogenous Ksr and MEK cc-precipitated from PC12 cells, Phosphorylation of MEK by mKsr-1 was not detected, however, In contrast, the MEK subpopulation complexed with mKsr-1 in COS-1 cells or PC12 cells did not display kinase activity. This ability of Ksr to block MEK in an inactive form correlated with a biological response: mKsr-1 did not transform NIH3T3 cells, and, furthermore, mKsr-1 reduced Pas-induced transformation, Similarly, mKsr-1 inhibited the proliferation of embryonic neuroretina cells induced by Pas and B-Raf but not that induced by MEK.Conclusions: Our results suggest a novel mechanism for Ksr in regulating the MAP kinase pathway, at least in part through an ability to interact with MEK.