Differential Gene Expression Induced by Insulin and Insulin-like Growth Factor-II through the Insulin Receptor Isoform A

• Published in: The Journal of biological chemistry 2003-10, Vol.278 (43), p.42178-42189
• Main Authors: Pandini, Giuseppe, Medico, Enzo, Conte, Enrico, Sciacca, Laura, Vigneri, Riccardo, Belfiore, Antonino
• Format: Article
• Language: English
• Subjects: Animals; Antigens, CD; Cluster Analysis; Gene Expression Profiling; Gene Expression Regulation - drug effects; Genes - drug effects; Humans; Insulin - pharmacology; Insulin-Like Growth Factor II - pharmacology; Kinetics; Mice; Oligonucleotide Array Sequence Analysis; Protein Isoforms; Receptor, Insulin - genetics; Receptor, Insulin - metabolism; Receptor, Insulin - physiology; RNA, Messenger - analysis; Transcription, Genetic - drug effects; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M304980200

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 α-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.