Regulation of protein phosphorylation by insulin and an insulinomimetic oligosaccharide in 3T3-L1 adipocytes and Fao hepatoma cells.
The ability of insulin and an insulinomimetic oligosaccharide (IOS) isolated from conditioned medium of Reuber hepatoma cells to regulate protein phosphorylation in 3T3-L1 adipocytes and Fao hepatoma cells has been examined in extracts prepared from 32P-labeled cells and by immunoblotting of unlabeled extracts with an anti-phosphotyrosine antibody. In 32P-labeled 3T3-L1 cells, both insulin and IOS stimulate the dephosphorylation of a 55K membrane-associated protein, yet only insulin stimulates the phosphorylation of the ribosomal S6 protein and a 22K heat-stable soluble protein. In 32P-labeled Fao cells, both insulin and IOS stimulate the phosphorylation of a 16K protein, but only insulin stimulates S6 phosphorylation. As judged by immunoblotting, IOS does not stimulate the tyrosine phosphorylation of the beta subunit of the insulin receptor and a 180K soluble protein in a manner similar to insulin. These data indicate that the insulinomimetic effects of IOS are selective for certain insulin-regulated pathways and that the effects of IOS are unlikely to be operating through stimulation of the insulin receptor tyrosine kinase.
Witters
L A
LA
Department of Medicine, Dartmouth Medical School, Hanover, N.H. 03756.
Watts
T D
TD
Gould
G W
GW
Lienhard
G E
GE
Gibbs
E M
EM
D000273:Adipose Tissue / Q000187:drug effects*; D000818:Animals; D002460:Cell Line; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008970:Molecular Weight; D009844:Oligosaccharides / Q000494:pharmacology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin; D014443:Tyrosine / Q000378:metabolism
D007328:Insulin; D009844:Oligosaccharides; D011506:Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin