Akt (protein kinase B) negatively regulates SEK1 by means of protein phosphorylation
Akt (protein kinase B) negatively regulates SEK1 by means of protein phosphorylation
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DOI：
10.1074/jbc.m110299200
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发表时间：
2002-01-25
影响因子：
4.8
通讯作者：
Choi, EJ
中科院分区：
文献类型：
--
作者：
Park, HS;Kim, MS;Choi, EJ
蛋白质丝氨酸-苏氨酸激酶Akt介导由各种生长促进因子如胰岛素引发的细胞存活信号传导。在这里，我们报告说，SEK 1是Akt在完整细胞中的靶点。在293 T细胞中，胰岛素抑制茴香霉素诱导的内源性SEK 1及其底物c-Jun N-末端激酶（JNK）的刺激，但不抑制上游激酶MEKK 1的刺激。胰岛素对SEK 1或JNK 1活化的抑制作用可被磷脂酰肌醇3-激酶抑制剂LY 294002阻止。在转染的293 T细胞中，Akt的组成型活性形式的表达也抑制SEK 1和JNK 1的活化，但不抑制MEKK 1的活化。免疫共沉淀分析显示，内源性Akt与内源性SEK 1在细胞中发生物理相互作用，并且这种相互作用由胰岛素促进。在体外和体内P-32标记表明，Akt磷酸化SEK 1的丝氨酸78。SEK 1突变体SEK 1（S78 A）对Akt诱导的抑制具有抗性。最后，激活的Akt抑制SEK 1介导的细胞凋亡，并且Akt的这种作用被SEK（S78 A）的过表达所阻止。综上所述，这些结果表明Akt通过靶向SEK 1抑制应激激活的信号传导。
The protein serine-threonine kinase Akt mediates cell survival signaling initiated by various growth-promoting factors such as insulin. Here we report that SEK1 is a target of Akt in intact cells. Insulin inhibited the anisomycin-induced stimulation of both endogenous SEK1 and its substrate c-Jun N-terminal kinase (JNK), but not that of the upstream kinase MEKK1, in 293T cells. The inhibitory action of insulin on SEK1 or JNK1 activation was prevented by the phosphatidylinositol 3-kinase inhibitor LY294002. Expression of a constitutively active form of Akt also inhibited both SEK1 and JNK1 activation, but not that of MEKK1, in transfected 293T cells. Co-immunoprecipitation analysis revealed that endogenous Akt physically interacted with endogenous SEK1 in cells and that this interaction was promoted by insulin. In vitro and in vivo P-32 labeling indicated that Akt phosphorylated SEK1 on serine 78. The SEK1 mutant SEK1(S78A) was resistant to Akt-induced inhibition. Finally, activated Akt inhibited SEK1-mediated apoptosis, and this effect of Akt was prevented by overexpression of SEK(S78A). Taken together, these results suggest that Akt suppresses stress-activated signaling by targeting SEK1.