title: Protein kinase C-stimulated phosphorylation in vitro of a Mr 80,000 protein phosphorylated in response to phorbol esters and growth factors in intact fibroblasts. Distinction from protein kinase C and prominence in brain.
abstract: In previous studies in intact 3T3-L1 fibroblasts and adipocytes, we demonstrated that the phosphorylation state of an acidic, multicomponent Mr 80,000 protein appeared to be a specific and useful marker for the activation state of protein kinase C (Blackshear, P.J., Witters, L.A., Girard, P.R., Kuo, J.F., and Quamo, S.N. (1985) J. Biol. Chem. 260, 13304-13315). In the present studies, we demonstrate that the Mr 80,000 protein from rat adipose tissue was a substrate for protein kinase C in vitro, and co-migrated on two-dimensional gels with the analogous protein from murine 3T3-L1 adipocytes labeled by exposure of intact cells to 32Pi and phorbol 12-myristate 13-acetate. Partial proteolytic maps of the two 32P-proteins were nearly identical, supporting the postulate that the sites phosphorylated by protein kinase C in vitro, and in response to phorbol 12-myristate 13-acetate in vivo, were similar or identical. Despite their similar apparent molecular weights, we were able to distinguish between the Mr 80,000 protein and protein kinase C by several physical criteria. The Mr 80,000 protein kinase C substrate was found in fractions of all rat tissues examined, but was most prominent in rat brain. Phorbol 12-myristate 13-acetate also stimulated phosphorylation of the Mr 80,000 protein in several types of cultured neuronal cells, suggesting a possible role for this protein in cholinergic neurotransmission. The Mr 80,000 protein appears to be a useful marker for protein kinase C activation in a variety of cell types.
authors.forename: P J
authors.initials: PJ
authors.lastname: Blackshear
authors.forename: L
authors.initials: L
authors.lastname: Wen
authors.forename: B P
authors.initials: BP
authors.lastname: Glynn
authors.forename: L A
authors.initials: LA
authors.lastname: Witters
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D002460:Cell Line; D002645:Chickens; D006224:Cricetinae; D004533:Egtazic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006133:Growth Substances / Q000494:pharmacology*; D006358:Hot Temperature; D006801:Humans; D007163:Immunosorbent Techniques; D051379:Mice; D008970:Molecular Weight; D010703:Phorbol Esters / Q000494:pharmacology*; D010750:Phosphoproteins / Q000032:analysis*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D006133:Growth Substances; D010703:Phorbol Esters; D010750:Phosphoproteins; D004533:Egtazic Acid; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate