title: Differential gene expression induced by insulin and insulin-like growth factor-II through the insulin receptor isoform A.
abstract: The human insulin receptor (IR) exists in two isoforms (IR-A and IR-B). IR-A is a short isoform, generated by the skipping of exon 11, a small exon encoding for 12 amino acid residues at the carboxyl terminus of the IR alpha-subunit. Recently, we found that IR-A is the predominant isoform in fetal tissues and malignant cells and binds with a high affinity not only insulin but also insulin-like growth factor-II (IGF-II). To investigate whether the activation of IR-A by the two ligands differentially activate post-receptor molecular mechanisms, we studied gene expression in response to IR-A activation by either insulin or IGF-II, using microarray technology. To avoid the interfering effect of the IGF-IR, IGF-II binding to the IR-A was studied in IGF-IR-deficient murine fibroblasts (R- cells) transfected with the human IR-A cDNA (R-/IR-A cells). Gene expression was studied at 0.5, 3, and 8 h. We found that 214 transcripts were similarly regulated by insulin and IGF-II, whereas 45 genes were differentially transcribed. Eighteen of these differentially regulated genes were responsive to only one of the two ligands (12 to insulin and 6 to IGF-II). Twenty-seven transcripts were regulated by both insulin and IGF-II, but a significant difference between the two ligands was present at least in one time point. Interestingly, IGF-II was a more potent and/or persistent regulator than insulin for these genes. Results were validated by measuring the expression of 12 genes by quantitative real-time reverse transcriptase-PCR. In conclusion, we show that insulin and IGF-II, acting via the same receptor, may differentially affect gene expression in cells. These studies provide a molecular basis for understanding some of the biological differences between the two ligands and may help to clarify the biological role of IR-A in embryonic/fetal growth and the selective biological advantage that malignant cells producing IGF-II may acquire via IR-A overexpression.
authors.affiliation: Dipartimento di Medicina Interna e di Medicine Specialistiche, Cattedra di Endocrinologia, University of Catania, USL 34, Ospedale Garibaldi, 95123 Catania, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pandini
authors.forename: Enzo
authors.initials: E
authors.lastname: Medico
authors.forename: Enrico
authors.initials: E
authors.lastname: Conte
authors.forename: Laura
authors.initials: L
authors.lastname: Sciacca
authors.forename: Riccardo
authors.initials: R
authors.lastname: Vigneri
authors.forename: Antonino
authors.initials: A
authors.lastname: Belfiore
mesh_terms: D000818:Animals; D015703:Antigens, CD; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D005796:Genes / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000032:analysis; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
chemical_list: D015703:Antigens, CD; D007328:Insulin; D020033:Protein Isoforms; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II; C435941:INSR protein, human; D011972:Receptor, Insulin