title: Identification of protein phosphatase 2A as the major tyrosine hydroxylase phosphatase in adrenal medulla and corpus striatum: evidence from the effects of okadaic acid.
abstract: (i) The major sites on bovine adrenal tyrosine hydroxylase (TH) phosphorylated by calmodulin-dependent multiprotein kinase (CaM-MPK) and cyclic AMP-dependent protein kinase were shown to be Ser-19 and Ser-40, respectively, while Ser-40 was also phosphorylated slowly by CaM-MPK. (ii) Type 2A and type 2C phosphatases accounted for approximately 90% and approximately 10% of TH phosphatase activity, respectively, in extracts of adrenal medulla and corpus striatum assayed at near physiological free Mg2+ (1 mM), while type 1 and type 2B phosphatases had negligible activity towards TH. (iii) Incubation of adrenal chromaffin cells with okadaic acid increased TH phosphorylation by 206% and activity by 77%, establishing that type 2A phosphatases play a major role in regulating TH in vivo.
authors.affiliation: Department of Biochemistry, University of Bergen, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Haavik
authors.forename: D L
authors.initials: DL
authors.lastname: Schelling
authors.forename: D G
authors.initials: DG
authors.lastname: Campbell
authors.forename: K K
authors.initials: KK
authors.lastname: Andersson
authors.forename: T
authors.initials: T
authors.lastname: Flatmark
authors.forename: P
authors.initials: P
authors.lastname: Cohen
mesh_terms: D000313:Adrenal Medulla / Q000201:enzymology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002417:Cattle; D002838:Chromaffin System / Q000201:enzymology; D003342:Corpus Striatum / Q000201:enzymology*; D004533:Egtazic Acid / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D054648:Protein Phosphatase 2; D011817:Rabbits; D051381:Rats; D014268:Trifluoperazine / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D004988:Ethers, Cyclic; D047428:Protein Kinase Inhibitors; D019319:Okadaic Acid; D014268:Trifluoperazine; D004533:Egtazic Acid; D014446:Tyrosine 3-Monooxygenase; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D008274:Magnesium