PLC-gamma1 enzyme activity is required for insulin-induced DNA synthesis.
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.
Eichhorn
Jens
J
Medical Research Service, San Diego Veterans Affairs Healthcare System, San Diego, California 92161, USA.
Kayali
Ayse G
AG
Resor
Laura
L
Austin
Darrell A
DA
Rose
David W
DW
Webster
Nicholas J G
NJ
D000818:Animals; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis*; D005347:Fibroblasts; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation; D051381:Rats; D011972:Receptor, Insulin / Q000187:drug effects; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction / Q000187:drug effects; D013268:Stimulation, Chemical; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018909:src Homology Domains
D007004:Hypoglycemic Agents; D007328:Insulin; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D004247:DNA; D005982:Glutathione Transferase; D011972:Receptor, Insulin; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma