Rat hepatoma cell variants resistant to insulin-diphtheria toxin A fragment conjugates. Genetic evidence for the separate pathways for insulin receptor-mediated mitogenic and hormonal stimulation.
The rat hepatoma H35 cells in serum-free medium produce tyrosine aminotransferase (TAT) and initiate DNA synthesis and cell division upon exposure to 10(-9)-10(-10) M insulin. This insulin-dependent hormonal and mitogenic stimulation is through the insulin receptors and not through the receptors for insulin-like growth factor type I. We have isolated genetic variants of H35 cells which are resistant to a cytotoxic insulin-diphtheria toxin A fragment conjugate. These variants showed different degrees of insulin binding capacity and exhibited different sensitivities to insulin-stimulated TAT and DNA synthesis. Variant DTaI-b had a slight decrease in number of insulin receptors but completely lost sensitivity to both TAT and DNA stimulation. Variant 11-1 had a reduced number of insulin receptors but retained both TAT and DNA inducibilities. Variant 14-1, which had a high number of insulin receptors, was not responsive to DNA synthesis but was responsive to TAT induction. The beta-subunit of insulin receptors in these cell variants had different sensitivities to their insulin-dependent autophosphorylation. The rat hepatoma HTC cells used as a control showed very low insulin binding, no stimulation of TAT and DNA synthesis by insulin, and no detectable insulin-enhancement of beta-subunit phosphorylation. These characteristics provide genetic evidence for the divergence of the insulin receptor-mediated mitogenic and hormonal signals during the post-receptor pathways which is apparently regulated by the insulin-dependent phosphorylation.
Shimizu
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Shimizu
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D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D004273:DNA, Neoplasm / Q000096:biosynthesis*; D004167:Diphtheria Toxin / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000032:analysis; D017451:Receptors, Somatomedin; D014444:Tyrosine Transaminase / Q000096:biosynthesis
D004273:DNA, Neoplasm; D004167:Diphtheria Toxin; D007328:Insulin; D010446:Peptide Fragments; D011506:Proteins; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; C029795:diphtheria toxin fragment A; D014444:Tyrosine Transaminase; D011972:Receptor, Insulin