Nucleotide excision repair is not required for the antiapoptotic function of insulin-like growth factor 1.
The expression of ERCC1, a member of the nucleotide excision repair (NER) family, is enhanced in cells transfected with insulin-like growth factor 1 (IGF-1) receptors. Of interest, an excellent concordance between ERCC1 expression and NER-mediated cell survival has been demonstrated. The two aims of the present study were to determine the signaling pathways used by IGF-1 to confer protection against apoptotic cell death in Chinese hamster ovary (CHO) cells and to assess the role of NER in this IGF-1 action. Experiments with pharmacological inhibitors indicated that phosphatidylinositol 3-kinase (PI 3-kinase) but not mitogen-activated protein kinase (ERK1/ERK2) mediates IGF-1 antiapoptotic activity. Using two series of CHO cells that have altered expression of ERCC1 or XPB/ERCC3, we examined IGF-1's ability to delay apoptotic death and reduction of mitochondrial oxidative function mediated by growth factor withdrawal. IGF-1 effectively blocked apoptosis, concomitant with increased MTT activity, in a pair of CHO cell lines expressing inactive ERCC1 (43-3B cells) and the transfected line of the mutant carrying the expressed human ERCC1 gene (83-G5 cells). Similarly, repair-deficient UV24 cells, which lack XPB/ERCC3, and their parental line AA8 were also responsive to the IGF-1's antiapoptotic capacity. In the presence of IGF-1, these cell lines became resistant to the cleavage of poly(ADP-ribose) polymerase, a key player in DNA damage recognition and DNA repair. These results suggest that PI 3-kinase activation plays a determinant role in the antiapoptotic function of IGF-1, but that functional NER does not play a critical part in mediating this IGF-1 response.
Lee-Kwon
W
W
Laboratory of Clinical Investigation, National Institutes of Health, Baltimore, Maryland, 21224-6825, USA.
Park
D
D
Bernier
M
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D016466:CHO Cells; D006224:Cricetinae; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins; D004720:Endonucleases; D005786:Gene Expression Regulation; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology* / Q000502:physiology*; D009154:Mutation; D011506:Proteins / Q000502:physiology*; D017526:Receptor, IGF Type 1 / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology*
D004268:DNA-Binding Proteins; D011506:Proteins; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; C071447:ERCC1 protein, human; D004720:Endonucleases