title: Akt2, but not Akt1, is required for cell survival by inhibiting activation of JNK and p38 after UV irradiation.
abstract: The serine/threonine protein kinase, Akt/PKB, has an essential function in cell survival during response to various stresses. Recent studies have demonstrated that Akt isoforms exhibit some distinct physiological functions, but the isotype-specific functions for Akt in the stress response have not been fully identified. In this study, we analysed the cellular response to genotoxic stress using isogenic wild-type, Akt1(-/-) and Akt2(-/-) mouse embryonic fibroblasts (MEFs). Marked hypersensitivity of Akt2(-/-) MEFs was observed to UV irradiation, whereas wild-type and Akt1(-/-) MEFs showed comparable levels of resistance. Akt2(-/-) mouse aortic endothelial cells also showed hypersensitivity to UV and the reconstitution of Akt2 expression in the Akt2(-/-) MEFs restored the UV resistance of the cells. Interestingly, upon UV irradiation, JNK and p38 were significantly upregulated in Akt2(-/-) MEFs, compared to wild-type and Akt1(-/-) MEFs. Additionally, inhibition of JNK and p38 activation reduced UV-induced cell death. Furthermore, both the hyperactivation of JNK and p38 and the UV-induced cell death in Akt2(-/-) MEFs were completely inhibited by restoring Akt2 expression. These results indicate that Akt2, but not Akt1, is essential for cell survival upon UV irradiation, and that Akt2 prevents UV-induced cell death by inhibiting activation of JNK and p38.
authors.affiliation: Department of Biochemistry, College of Medicine, Dong-A University, Seo-Gu, Busan, South Korea.
authors.forename: M-A
authors.initials: MA
authors.lastname: Kim
authors.forename: H-J
authors.initials: HJ
authors.lastname: Kim
authors.forename: H J
authors.initials: HJ
authors.lastname: Jee
authors.forename: A J
authors.initials: AJ
authors.lastname: Kim
authors.forename: Y-S
authors.initials: YS
authors.lastname: Bae
authors.forename: S S
authors.initials: SS
authors.lastname: Bae
authors.forename: J
authors.initials: J
authors.lastname: Yun
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D002470:Cell Survival; D004789:Enzyme Activation; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D051379:Mice; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D014466:Ultraviolet Rays; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C514862:Akt1 protein, mouse; C494922:Akt2 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4