Akt (protein kinase B) negatively regulates SEK1 by means of protein phosphorylation.
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 (32)P 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.
Park
Hee-Sae
HS
National Creative Research Initiative Center for Cell Death, Graduate School of Biotechnology, Korea University, Seoul 136-701, Korea.
Kim
Mi-Sung
MS
Huh
Sung-Ho
SH
Park
Jihyun
J
Chung
Jongkyeong
J
Kang
Sang Sun
SS
Choi
Eui-Ju
EJ
D000841:Anisomycin / Q000494:pharmacology; D017209:Apoptosis; D002460:Cell Line; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection
D000841:Anisomycin; D002867:Chromones; D004791:Enzyme Inhibitors; D005982:Glutathione Transferase; D007328:Insulin; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D012694:Serine; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C482576:MAP3K1 protein, human; C482559:MAP2K4 protein, human