title: Okadaic acid-sensitive protein phosphatases dephosphorylate MARCKS, a major protein kinase C substrate.
abstract: The myristoylated alanine-rich C kinase substrate (MARCKS) undergoes a rapid and, in certain circumstances, transient increase in phosphorylation in response to stimuli that activate protein kinase C. We have investigated the protein-serine/threonine phosphatase activity responsible for reversing the phosphorylation of MARCKS. In cell-free assays, protein phosphatases 1, 2A and 2C (PP1, PP2A and PP2C) all dephosphorylate recombinant MARCKS or a synthetic peptide based on its phosphorylation site domain. In intact Swiss 3T3 cells, okadaic acid, a specific inhibitor of PP1 and PP2A, had little effect on MARCKS phosphorylation on its own, but largely prevented the dephosphorylation of MARCKS that occurred following activation of protein kinase C by bombesin with subsequent receptor blockade. These results indicate that although the dephosphorylation of MARCKS can be mediated by PP2C in vitro, this protein is dephosphorylated by okadaic acid-sensitive phosphatases in the intact cell.
authors.affiliation: Department of Biochemistry, University of Dundee, Scotland, UK.
authors.forename: P R
authors.initials: PR
authors.lastname: Clarke
authors.forename: S R
authors.initials: SR
authors.lastname: Siddhanti
authors.forename: P
authors.initials: P
authors.lastname: Cohen
authors.forename: P J
authors.initials: PJ
authors.lastname: Blackshear
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D004988:Ethers, Cyclic / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004988:Ethers, Cyclic; D047908:Intracellular Signaling Peptides and Proteins; C000619711:Marcks protein, mouse; D008565:Membrane Proteins; D011506:Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D019319:Okadaic Acid; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases