title: Activation of MAP kinase and enhanced phosphorylation of the 350-kDa protein by mitogenic stimuli in quiescent Balb/c 3T3 cells.
abstract: In quiescent Balb/c 3T3 cells, competence factors such as platelet-derived growth factor and 12-O-tetradecanoylphorbol-13-acetate (TPA) activated MAP kinase, whereas progression factors such as insulin did not. Insulin was, however, capable of activating MAP kinase in cells pretreated with TPA. Moreover, TPA plus insulin activated MAP kinase more strongly and for a longer time period than did TPA alone. Treatment of Balb/c 3T3 cells with competence factors stimulated phosphorylation of the 350-kDa protein which was immunoprecipitated with antibodies against brain high-molecular-weight microtubule-associated protein MAP1, whereas insulin treatment did not stimulate the phosphorylation. Insulin could induce, however, further increase in the phosphorylation of the 350-kDa protein, when added simultaneously with TPA or added to the TPA-treated cells. The enhanced phosphorylation of the 350-kDa protein thus correlated with the MAP kinase activation. As insulin acts synergistically with TPA to induce initiation of DNA synthesis in the quiescent Balb/c 3T3 cells, it seems that activation of MAP kinase and enhanced phosphorylation of the 350-kDa protein are accompanied by the initiation of DNA synthesis.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kawakami
authors.forename: E
authors.initials: E
authors.lastname: Nishida
authors.forename: K
authors.initials: K
authors.lastname: Tobe
authors.forename: M
authors.initials: M
authors.lastname: Hoshi
authors.forename: T
authors.initials: T
authors.lastname: Kadowaki
authors.forename: M
authors.initials: M
authors.lastname: Kasuga
authors.forename: H
authors.initials: H
authors.lastname: Sakai
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002478:Cells, Cultured; D004261:DNA Replication / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D007328:Insulin / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology*; D008970:Molecular Weight; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D007328:Insulin; D008869:Microtubule-Associated Proteins; D008934:Mitogens; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate