title: Adenosine 3',5'-cyclic monophosphate/vanadate-sensitive phosphorylation of DARPP-32- and inhibitor-1-immunoreactive proteins.
abstract: Among the cellular actions of vanadate ions are several that have the potential to be of significance in the regulation of protein phosphorylation. The effects of vanadate on adenosine 3',5' cyclic monophosphate (cAMP)-dependent and independent, alkali-resistant protein phosphorylation in a synaptosomal preparation from rat cortex were examined in this study. Three major vanadate-stimulated, cAMP-independent phosphoproteins (58-, 50-, and 39-kDa) and two cAMP-dependent species (37- and 32-kDa) were detectable. The potentiation between vanadate and cAMP in stimulating the phosphorylation of the latter two proteins is in contrast to the nonadditive combined effect of both on the phosphorylation of other synaptosomal proteins. The two cAMP-dependent, 32P-labeled proteins possess identical or very similar physicochemical properties to two previously cited neuronal phosphoproteins, namely, dopamine- and adenosine 3',5'-monophosphate-regulated phosphoprotein-32 (DARPP-32) and inhibitor-1 (I-1). Such properties include phosphorylation by cAMP-dependent protein kinase, the presence of an alkali-resistant phosphothreonine residue, comigration on two-dimensional gel electrophoresis, dephosphorylation by type-2B protein phosphatase, and crossreactivity with specific antibodies. Costimulation by cAMP and vanadate of phosphorylation of the latter two proteins on threonine residues, at concentrations of vanadate consistent with the regulation of protein tyrosine phosphatase activity, indicates a unique interaction between these two regulators of protein phosphorylation at the nerve terminus.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Ohio, Toledo 43699-0008, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Edgar
authors.forename: L A
authors.initials: LA
authors.lastname: Dokas
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000166:cytology / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D007525:Isoelectric Focusing; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D013574:Synaptosomes / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology*
chemical_list: C087425:ANP32A protein, human; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; D016601:RNA-Binding Proteins; D014638:Vanadates; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017027:Protein Tyrosine Phosphatases