Glutamate regulation of DARPP-32 phosphorylation in neostriatal neurons involves activation of multiple signaling cascades.
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.
Nishi
Akinori
A
Department of Pharmacology, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan. nishia@med.kurume-u.ac.jp
Watanabe
Yasuo
Y
Higashi
Hideho
H
Tanaka
Masatoshi
M
Nairn
Angus C
AC
Greengard
Paul
P
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
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