title: Modulation of synaptosomal protein phosphorylation/dephosphorylation by calcium is antagonised by inhibition of protein phosphatases with okadaic acid.
abstract: The protein phosphatase inhibitor okadaic acid was used to investigate the protein phosphatases involved in the endogenous dephosphorylation of proteins in intact synaptosomes. Despite the fact that the calcium-dependent protein phosphatase (calcineurin) is most concentrated in synaptosomes and accounts for approximately 0.3% of synaptoplasmic protein, the majority of the dephosphorylation activity under both basal and depolarisation conditions is due to protein phosphatase type 1 (PP1) and/or protein phosphatase type 2A (PP2A). Nevertheless our results do suggest that calcineurin is active in synaptosomes and has 2 effects: a rapid, direct dephosphorylation of a limited range of substrates and an indirect activation of PP1 presumably by dephosphorylation of protein phosphatase 1 inhibitor-1.
authors.affiliation: Neuroscience Group, Faculty of Medicine, University of Newcastle, N.S.W., Australia.
authors.forename: A T
authors.initials: AT
authors.lastname: Sim
authors.forename: P R
authors.initials: PR
authors.lastname: Dunkley
authors.forename: P E
authors.initials: PE
authors.lastname: Jarvie
authors.forename: J A
authors.initials: JA
authors.lastname: Rostas
mesh_terms: D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004563:Electrochemistry; D004988:Ethers, Cyclic / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019319:Okadaic Acid; D009994:Osmolar Concentration; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D051381:Rats; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: D004988:Ethers, Cyclic; D009419:Nerve Tissue Proteins; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D002118:Calcium