title: Ca2+/calmodulin-dependent phosphorylation of the 100-kDa protein in chick embryonic muscle cells in culture.
abstract: The pattern of protein phosphorylation was found to change in differentiating chick embryonic myoblasts in culture. The extent of phosphorylation of 42-, 50-, and 100-kDa proteins increased while that of a 63-kDa protein declined in extracts of myoblasts that had been cultured for increasing periods. Of these, the increase in phosphorylation of the 100-kDa protein occurred most dramatically in extracts of myoblasts in an early stage of differentiation and was specifically inhibited by trifluoperazine (TFP) and other calmodulin (CaM) antagonists including chlorpromazine and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7). Treatment of increasing concentrations of TFP to culture medium also decreased the phosphorylation state of the 100-kDa protein and the degree of myoblast fusion in parallel. In addition, levels of both the kinase activity and the 100-kDa protein but not of CaM appeared to rise in the cells cultured for longer periods. These results suggest that (1) a Ca2+/CaM-dependent protein kinase is responsible for phosphorylation of the 100-kDa protein, (2) the TFP-mediated myoblast fusion block may be associated with the inhibitory effect of the drug against the kinase activity, and (3) the increase in phosphorylation state of the 100-kDa protein during myogenic differentiation is due to the rise in levels of the kinase and its substrate.
authors.affiliation: Department of Molecular Biology, College of Natural Sciences, Seoul National University, Korea.
authors.forename: H S
authors.initials: HS
authors.lastname: Kim
authors.forename: I H
authors.initials: IH
authors.lastname: Lee
authors.forename: C H
authors.initials: CH
authors.lastname: Chung
authors.forename: M S
authors.initials: MS
authors.lastname: Kang
authors.forename: D B
authors.initials: DB
authors.lastname: Ha
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D002454:Cell Differentiation; D002459:Cell Fusion / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D002746:Chlorpromazine / Q000494:pharmacology; D002848:Chromatography, DEAE-Cellulose; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009132:Muscles / Q000166:cytology / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification*; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D009124:Muscle Proteins; D010750:Phosphoproteins; D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium; D002746:Chlorpromazine