title: DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-SIN1 association mediates ultraviolet B (UVB)-induced Akt Ser-473 phosphorylation and skin cell survival.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tu
authors.affiliation: Department of Dermatology, The First Affiliated Hospital of Kunming Medical University, Yunnan Provincial Institute of Dermatology, Kunming 650032, Yunnan, China. surpassing_ji@aliyun.com.
authors.forename: Chao
authors.initials: C
authors.lastname: Ji
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Yang
authors.forename: Hua
authors.initials: H
authors.lastname: Gu
authors.forename: Chun-Cheng
authors.initials: CC
authors.lastname: Lu
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Zhong-Lan
authors.initials: ZL
authors.lastname: Su
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Wei-Ling
authors.initials: WL
authors.lastname: Sun
authors.forename: Ji-Ping
authors.initials: JP
authors.lastname: Xia
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Bi
authors.forename: Li
authors.initials: L
authors.lastname: He
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000528:radiation effects; D002867:Chromones / Q000494:pharmacology; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000201:enzymology* / Q000502:physiology / Q000528:radiation effects; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D046912:Multiprotein Complexes / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D061251:Primary Cell Culture; D011499:Protein Processing, Post-Translational / Q000528:radiation effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011836:Radiation Tolerance; D012867:Skin / Q000473:pathology; D012878:Skin Neoplasms / Q000201:enzymology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D048868:Adaptor Proteins, Signal Transducing; D002867:Chromones; C493277:MAPKAP1 protein, human; D009025:Morpholines; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors; D051747:DNA-Activated Protein Kinase; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; C497263:PRKDC protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases