title: Interactions between cyclic AMP- and phorbol ester-dependent phosphorylation systems in S49 mouse lymphoma cells.
abstract: High-resolution two-dimensional gel electrophoresis of proteins labeled with either 32Pi or [35S]methionine was used to study interactions between cyclic AMP and tetradecanoyl phorbol acetate (TPA) at the level of intracellular protein phosphorylation. Cultured S49 mouse lymphoma cells were used as a model system, and mutant sublines lacking either the catalytic subunit of cyclic AMP-dependent protein kinase or the guanyl nucleotide-binding "Ns" factor of adenylate cyclase provided tools to probe mechanisms underlying the interactions observed. Three sets of phosphoproteins responded differently to TPA treatment of wild-type and mutant cells: Phosphorylations shown previously to be responsive to activation of intracellular cyclic AMP-dependent protein kinase were stimulated by TPA in wild-type cells but not in mutant cells, a subset of phosphorylations stimulated strongly by TPA in mutant cells was inhibited in wild-type cells, and two novel phosphoprotein species appeared in response to TPA only in wild-type cells. The latter two classes of TPA-mediated responses specific to wild-type cells could be evoked in adenylate cyclase-deficient cells by treating concomitantly with TPA and either forskolin or an analog of cyclic AMP. Three conclusions are drawn from our results: 1) TPA stimulates adenylate cyclase in wild-type cells causing increased phosphorylation of endogenous substrates by cyclic AMP-dependent protein kinase, 2) activated cyclic AMP-dependent protein kinase inhibits phosphorylation (or enhances dephosphorylation) of a specific subset of TPA-dependent phosphoproteins, and 3) cyclic AMP-dependent events facilitate TPA-dependent phosphorylation of some substrate proteins.
mesh_terms: D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004357:Drug Synergism; D008223:Lymphoma / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D010704:Phorbols / Q000494:pharmacology*; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D010704:Phorbols; D011506:Proteins; D005576:Colforsin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate