title: Glutamate regulation of DARPP-32 phosphorylation in neostriatal neurons involves activation of multiple signaling cascades.
abstract: Dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) plays a central role in medium spiny neurons in the neostriatum in the integration of various neurotransmitter signaling pathways. In its Thr-34-phosphorylated form, it acts as a potent protein phosphatase-1 inhibitor, and, in its Thr-75-phosphorylated form, it acts as a cAMP-dependent kinase inhibitor. Here, we investigated glutamate-dependent signaling cascades in mouse neostriatal slices by analyzing the phosphorylation of DARPP-32 at Thr-34 and Thr-75. Treatment with glutamate (5 mM) caused a complex change in DARPP-32 Thr-34 phosphorylation. An initial rapid increase in Thr-34 phosphorylation was NMDA/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/metabotropic glutamate-5 receptor-dependent and was mediated through activation of a neuronal nitric oxide synthase/nitric oxide/cGMP/cGMP-dependent kinase signaling cascade. A subsequent decrease in phosphorylation was attributable to activation of an NMDA/AMPA receptor/Ca2+/protein phosphatase-2B signaling cascade. This decrease was followed by rephosphorylation via a pathway involving metabotropic glutamate-5 receptor/phospholipase C and extracellular receptor kinase signaling cascade. Treatment with glutamate initially decreased Thr-75 phosphorylation through activation of NMDA/AMPA receptor/Ca2+/protein phosphatase-2A signaling. Thereafter, glutamate slowly increased Thr-75 phosphorylation through activation of metabotropic glutamate-1 receptor/phospholipase C signaling. Our analysis of DARPP-32 phosphorylation in the neostriatum revealed that glutamate activates at least five different signaling cascades with different time dependencies, resulting in complex regulation of protein kinase and protein phosphatase activities.
authors.affiliation: Department of Pharmacology, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan. nishia@med.kurume-u.ac.jp
authors.forename: Akinori
authors.initials: A
authors.lastname: Nishi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Hideho
authors.initials: H
authors.lastname: Higashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tanaka
authors.forename: Angus C
authors.initials: AC
authors.lastname: Nairn
authors.forename: Paul
authors.initials: P
authors.lastname: Greengard
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D018698:Glutamic Acid / Q000494:pharmacology*; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D017072:Neostriatum / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology; D054799:Phospholipase C beta; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D018698:Glutamic Acid; D017869:Cyclic GMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D002118:Calcium