PLC-gamma1 enzyme activity is required for insulin-induced DNA synthesis

• Published in: Endocrinology (Philadelphia) Vol. 143; no. 2; pp. 655 - 664
• Main Authors: Eichhorn, Jens, Kayali, Ayse G, Resor, Laura, Austin, Darrell A, Rose, David W, Webster, Nicholas J G
• Format: Journal Article
• Language: English
• Published: United States 01.02.2002
• Subjects: Animals; Cell Line; DNA - biosynthesis; Fibroblasts; Gene Expression Regulation, Enzymologic - genetics; Glutathione Transferase - metabolism; Humans; Hypoglycemic Agents - pharmacology; Insulin - pharmacology; Isoenzymes - antagonists & inhibitors; Isoenzymes - metabolism; Mitogen-Activated Protein Kinases - metabolism; Phospholipase C gamma; Phosphorylation; Rats; Receptor, Insulin - drug effects; Recombinant Fusion Proteins; Signal Transduction - drug effects; src Homology Domains; Stimulation, Chemical; Type C Phospholipases - antagonists & inhibitors; Type C Phospholipases - metabolism
• ISSN: 0013-7227

Previously, we had shown that inhibition of PLC activity impaired the ability of insulin to activate ERK in 3T3-L1 adipocytes. In this study, we confirmed that the insulin receptor and PLC-gamma1 are physically associated in hIRcB fibroblasts, insulin stimulates PLC-gamma1 enzyme activity, and inhibition of PLC activity impairs activation of ERK. We subsequently investigated whether PLC-gamma1 is required for insulin-stimulated mitogenesis. First, inhibition of PLC activity using U73122 impairs the ability of insulin to stimulate DNA synthesis. Second, disruption of the interaction of the insulin receptor with PLC-gamma1 by microinjection of SH2 domains derived from PLC-gamma1 or Grb2 but not Shc similarly blocks insulin-induced DNA synthesis. Third, microinjection of neutralizing antibodies to PLC-gamma1 blocks DNA synthesis, but nonneutralizing antibodies do not. The blockade in all three cases is rescued by synthetic diacylglycerols but not by inositol-1,4,5-trisphosphate, indicating a requirement for PLC enzyme activity. These experimental data point to a requirement for PLC-gamma1 in insulin-stimulated mitogenesis in hIRcB cells.