title: An inhibitory effect of a protein kinase inhibitor, staurosporine, on delivery of endocytosed asialoglycoprotein to lysosome in monolayer culture of rat hepatocytes.
abstract: An inhibitor of protein kinases, staurosporine (ssp), was found to affect the endocytic pathway of asialoglycoproteins subsequent to endocytosis in monolayer cultures of rat hepatocytes. The effect of 5 or 10 microM staurosporine on the internalization of a synthetic ligand (galBSA-HRP: bovine serum albumin exposing galactose, horseradish peroxidase conjugates) prebound to the cell surface was minimal. The presence of 5, 7, or 10 microM ssp during a 1-h chase period resulted in the ligand remaining in a low density (1.04-1.05 g/ml), nonlysosomal subcellular fraction in a Percoll gradient. The ligand, arrested by 7 microM ssp, was further processed to the lysosome during subsequent incubation in the absence of ssp. Cells maintained the ability to internalize ligand at 37 degrees C for 1 h in the presence of these concentrations of ssp. During a 1-h continuous uptake of 0-50 micrograms/ml nonlabeled ligand, the presence of 7 microM ssp did not cause any decrease in the amount of asialoglycoprotein receptor at the cell surface, which indicates receptor recycling occurred normally. These results suggest a possible involvement of protein kinase(s), which can be inhibited by ssp, in the delivery of endocytosed ligand to the lysosome, but not in ligand endocytosis and receptor recycling.
authors.affiliation: Department of Biophysics, Faculty of Science, Kyoto University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ohashi
authors.forename: S
authors.initials: S
authors.lastname: Ohnishi
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins; D001692:Biological Transport / Q000187:drug effects; D002458:Cell Fractionation; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D004705:Endocytosis / Q000187:drug effects*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009961:Orosomucoid / Q000031:analogs & derivatives* / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D011971:Receptors, Immunologic / Q000378:metabolism*; D019311:Staurosporine
chemical_list: D000470:Alkaloids; D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins; D009961:Orosomucoid; D047428:Protein Kinase Inhibitors; D011971:Receptors, Immunologic; C017030:asialoorosomucoid; D019311:Staurosporine