Staurosporine inhibits a tyrosine protein kinase in human hepatoma cell membranes.
Membranes from the human hepatoma cell line HepG2 mediate the phosphorylation on tyrosine of the asialoglycoprotein receptor. Manganese was the preferred divalent for phosphorylation although magnesium was effective at an 8-fold higher concentration. Calcium was ineffective at promoting phosphorylation and zinc was inhibitory. The protein kinase inhibitor staurosporine blocked asialoglycoprotein receptor phosphorylation on tyrosine in nanomolar concentrations (IC50 = 70 nM). In contrast another protein kinase C inhibitor, H7, was not inhibitory, suggesting that the effect of staurosporine was not mediated by protein kinase C inhibition. Concentrations of staurosporine that inhibit receptor phosphorylation by greater than 90% did not inhibit the phosphorylation of other protein substrates identified on SDS-polyacrylamide gels. These data suggest that staurosporine selectively and directly inhibits a membrane-associated tyrosine protein kinase.
Fallon
R J
RJ
Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology*; D037263:Asialoglycoprotein Receptor; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000378:metabolism; D002413:Cations, Divalent / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D008113:Liver Neoplasms / Q000201:enzymology* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D019311:Staurosporine; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
D000470:Alkaloids; D037263:Asialoglycoprotein Receptor; D002413:Cations, Divalent; D007546:Isoquinolines; D008565:Membrane Proteins; D010879:Piperazines; D011971:Receptors, Immunologic; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D019311:Staurosporine