title: DNA-dependent protein kinase catalytic subunit is cleaved during UV-induced apoptosis.
abstract: Ultraviolet radiation can induce the injury of epidermal keratinocytes, resulting in sunburn cell (apoptotic cell) formation. It has been demonstrated that the protease caspase-3, a downstream molecule of the CD95 pathway, is activated in UV-exposed HaCaT cells, and that the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is cleaved by interleukin-1beta converting enzyme (ICE)-like protease during apoptosis induced by X-rays, staurosporine and etoposide. Then, we studied whether the DNA-PKcs is cleaved during UV-induced apoptosis in keratinocytes. We used the well-characterized cloned human keratinocyte cell line HaCaT, which carries p53 mutations. UVB-induced apoptotic cells were observed by TdT-mediated deoxyuridine 5'-triphosphate nick end labeling (TUNEL) assay and agarose gel electrophoresis. Western blot analysis was performed using the antibody against DNA-PKcs. The cleavage occurred during UVB-induced apoptosis in HaCaT cells. It suggests that the cleavage is associated with loss of DNA-PK activity. Thus, a functional relevance of cleavage of DNA-PKcs may be to prevent rejoining fragmented DNA during apoptosis, thereby promoting apoptotic processes. Although apoptosis was not completely blocked by the caspase-3 inhibitor, the cleavage of the DNA-PKcs was blocked. These results indicate that DNA-PKcs is cleaved by the caspase-3 for UVB-induced apoptosis in HaCaT cells.
authors.affiliation: Department of Dermatology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, 570-8506, Osaka, Japan. tito@takii.kmu.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Itoh
authors.forename: T
authors.initials: T
authors.lastname: Horio
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D002384:Catalysis; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000502:physiology*; D006801:Humans; D015603:Keratinocytes / Q000502:physiology* / Q000528:radiation effects*; D009842:Oligopeptides / Q000494:pharmacology; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D004247:DNA; D011494:Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3