Aromatic L-amino acid decarboxylase phosphorylation and activation by PKGIalpha in vitro.
Brain aromatic L-amino acid decarboxylase (AAAD) is subject to regulation, and phosphorylation might be involved in the short-term activation of the enzyme. Sites for serine/threonine phosphorylation are present in the deduced amino acid sequence of AAAD, and cAMP-dependent protein kinase phosphorylates and activates neuronal AAAD in vitro. We now report that cGMP-dependent protein kinase (PKG) is able to phosphorylate and activate neuronal AAAD. In an in vitro kinase assay, immunoprecipitated native and recombinant mouse brain AAAD was rapidly phosphorylated by exogenous PKGIalpha. When added to striatal homogenates, PKGIalpha increased AAAD activity in a temporal fashion similar to phosphorylation. Recombinant AAAD was also activated by the kinase demonstrating a direct effect. Native enzyme activation was moderate and characterized by increased V(max) and K(m) for L-DOPA. A PKG peptide inhibitor prevented AAAD phosphorylation and activation providing specificity, and causally linking the two events. Together, the findings provide evidence for PKGIalpha-dependent phosphorylation and activation of neuronal AAAD in vitro, and introduce AAAD as a putative PKGIalpha substrate. Neuronal AAAD is best known for its role in the biosynthesis of catecholamines, indoleamines and trace amines in the nervous system, and the biological importance of PKGIalpha phosphorylation in these processes remains to be determined.
Duchemin
Anne-Marie
AM
Division of Molecular Neuropsychopharmacology, Department of Psychiatry, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA.
Neff
Norton H
NH
Hadjiconstantinou
Maria
M
D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism*; D001921:Brain / Q000201:enzymology; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009474:Neurons / Q000201:enzymology; D010766:Phosphorylation
D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569720:Prkg1 protein, mouse; D001142:Aromatic-L-Amino-Acid Decarboxylases