title: Insulin-like Growth Factor 1 Receptor Signaling Is Required for Optimal ATR-CHK1 Kinase Signaling in Ultraviolet B (UVB)-irradiated Human Keratinocytes.
abstract: UVB wavelengths of light induce the formation of photoproducts in DNA that are potentially mutagenic if not properly removed by the nucleotide excision repair machinery. As an additional mechanism to minimize the risk of mutagenesis, UVB-irradiated cells also activate a checkpoint signaling cascade mediated by the ATM and Rad3-related (ATR) and checkpoint kinase 1 (CHK1) kinases to transiently suppress DNA synthesis and cell cycle progression. Given that keratinocytes in geriatric skin display reduced activation of the insulin-like growth factor 1 receptor (IGF-1R) and alterations in DNA repair rate, apoptosis, and senescence following UVB exposure, here we used cultured human keratinocytes in vitro and skin explants ex vivo to examine how IGF-1R activation status affects ATR-CHK1 kinase signaling and the inhibition of DNA replication following UVB irradiation. We find that disruption of IGF-1R signaling with small-molecule inhibitors or IGF-1 withdrawal partially abrogates both the phosphorylation and activation of CHK1 by ATR and the accompanying inhibition of chromosomal DNA synthesis in UVB-irradiated keratinocytes. A critical protein factor that mediates both ATR-CHK1 signaling and nucleotide excision repair is replication protein A, and we find that its accumulation on UVB-damaged chromatin is partially attenuated in cells with an inactive IGF-1R. These results indicate that mutagenesis and skin carcinogenesis in IGF-1-deficient geriatric skin may be caused by defects in multiple cellular responses to UVB-induced DNA damage, including through a failure to properly suppress DNA synthesis on UVB-damaged DNA templates.
authors.affiliation: From the Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio 45435, mike.kemp@wright.edu.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Kemp
authors.affiliation: the Departments of Dermatology and.|Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, and.
authors.forename: Dan F
authors.initials: DF
authors.lastname: Spandau
authors.affiliation: From the Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio 45435.
authors.forename: Richard
authors.initials: R
authors.lastname: Simman
authors.affiliation: From the Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio 45435.|the Dayton Veterans Affairs Medical Center, Dayton, Ohio 45428.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Travers
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D000071877:Checkpoint Kinase 1 / Q000378:metabolism*; D004261:DNA Replication / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology; D017526:Receptor, IGF Type 1; D017451:Receptors, Somatomedin / Q000378:metabolism*; D051716:Replication Protein A / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects*; D012867:Skin / Q000378:metabolism*; D015595:Skin Aging; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: C000597236:IGF1R protein, human; D017451:Receptors, Somatomedin; D051716:Replication Protein A; D017526:Receptor, IGF Type 1; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1
keywords: DNA damage; DNA damage response; DNA repair; DNA replication; cell signaling; checkpoint control; keratinocyte; nucleotide excision repair; protein kinase; skin