DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-SIN1 association mediates ultraviolet B (UVB)-induced Akt Ser-473 phosphorylation and skin cell survival

• Published in: Molecular cancer 2013-12, Vol.12 (1), p.172-172
• Main Authors: Tu, Ying, Ji, Chao, Yang, Bo, Yang, Zhi, Gu, Hua, Lu, Chun-Cheng, Wang, Rong, Su, Zhong-Lan, Chen, Bin, Sun, Wei-Ling, Xia, Ji-Ping, Bi, Zhi-Gang, He, Li
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Animals; Apoptosis; Apoptosis - radiation effects; Cell Line, Transformed; Cell Survival - radiation effects; Chinese medicine; Chromones - pharmacology; Deoxyribonucleic acid; Disease prevention; DNA; DNA-Activated Protein Kinase - antagonists & inhibitors; DNA-Activated Protein Kinase - metabolism; Enzyme Activation; Epidermal growth factor; Humans; Keratinocytes - enzymology; Keratinocytes - physiology; Keratinocytes - radiation effects; Kinases; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Medical research; Mice; Morpholines - pharmacology; Multiprotein Complexes - metabolism; Mutagenesis; Nuclear Proteins - antagonists & inhibitors; Nuclear Proteins - metabolism; Phosphorylation; Primary Cell Culture; Protein Processing, Post-Translational - radiation effects; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Radiation Tolerance; Receptor, Epidermal Growth Factor - metabolism; Reproductive health; Signal transduction; Skin - pathology; Skin cancer; Skin Neoplasms - enzymology; Statistical analysis; TOR Serine-Threonine Kinases - metabolism; Ultraviolet Rays
• ISSN: 1476-4598; 1476-4598
• DOI: 10.1186/1476-4598-12-172

The exposure of skin keratinocytes to Ultraviolet (UV) irradiation leads to Akt phosphorylation at Ser-473, which is important for the carcinogenic effects of excessive sun exposure. The present study investigated the underlying mechanism of Akt Ser-473 phosphorylation by UVB radiation. We found that DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and mammalian target of rapamycin (mTOR) complex 2 (mTORC2) were both required for UVB-induced Akt Ser-473 phosphorylation in keratinocytes. Inhibition of DNA-PKcs activity via its inhibitor NU7026, a dominant-negative kinase-dead mutation, RNA interference (RNAi) or gene depletion led to the attenuation of UVB-induced Akt Ser-473 phosphorylation. Meanwhile, siRNA silencing or gene depletion of SIN1, a key component of mTORC2, abolished Akt Ser-473 phosphorylation by UVB. Significantly, we discovered that DNA-PKcs was associated with SIN1 in cytosol upon UVB radiation, and this complexation appeared required for Akt Ser-473 phosphorylation. Meanwhile, this DNA-PKcs-SIN1 complexation by UVB was dependent on epidermal growth factor receptor (EGFR) activation, and was disrupted by an EGFR inhibitor (AG1478) or by EGFR depletion. UVB-induced complexation between DNA-PKcs and mTORC2 components was also abolished by NU7026 and DNA-PKcs mutation. Finally, we found that both DNA-PKcs and SIN1 were associated with apoptosis resistance of UVB radiation, and inhibition of them by NU7026 or genetic depletion significantly enhanced UVB-induced cell death and apoptosis. Taken together, these results strongly suggest that DNA-PKcs-mTORC2 association is required for UVB-induced Akt Ser-473 phosphorylation and cell survival, and might be important for tumor cell transformation.