title: Role of protein phosphatase 2A in mGluR5-regulated MEK/ERK phosphorylation in neurons.
abstract: The regulation of protein phosphorylation requires coordinated interaction between protein kinases and protein phosphatases (PPs). Recent evidence has shown that the Galphaq-protein-coupled metabotropic glutamate receptor (mGluR) 5 up-regulates phosphorylation of MAPK/ERK1/2. However, signaling mechanisms linking mGluR5 to ERK are poorly understood. In this study, roles of a major serine/threonine PP, PP2A, in this event were evaluated in cultured neurons. We found that the PP1/2A inhibitors okadaic acid and calyculin A mimicked the effect of the mGluR5 agonists (RS)-3,5-dihydroxyphenylglycine and (RS)-2-chloro-5-hydroxyphenylglycine in facilitating phosphorylation of ERK1/2 and its upstream kinase, MEK1/2, in a PP2A-dependent but not PP1-dependent manner. Co-administration of either inhibitor with an mGluR5 agonist produced additive phosphorylation of ERK1/2. Enzymatic assays showed a basal level of phosphatase activity of PP2A under normal conditions, and activation of mGluR5 selectively inhibited PP2A, but not PP1, activity. In addition, a physical association of the cytoplasmic C terminus of mGluR5 with PP2A was observed, and ligand activation of mGluR5 reduced mGluR5-PP2A binding. Additional mechanistic studies revealed that mGluR5 activation increased tyrosine (Tyr307) phosphorylation of PP2A, which was dependent on activation of a p60c-Src family tyrosine kinase, but not the epidermal growth factor receptor tyrosine kinase and resulted in dissociation of PP2A from mGluR5 and reduced PP2A activity. Together, we have identified a novel, mGluR5-triggered signaling mechanism involving use- and Src-dependent inactivation of PP2A, which contributes to mGluR5 activation of MEK1/2 and ERK1/2.
authors.affiliation: Department of Basic Medical Science, University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri 64108, USA.
authors.forename: Limin
authors.initials: L
authors.lastname: Mao
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.forename: Anish
authors.initials: A
authors.lastname: Arora
authors.forename: Eun Sang
authors.initials: ES
authors.lastname: Choe
authors.forename: Guochi
authors.initials: G
authors.lastname: Zhang
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Liu
authors.forename: Eugene E
authors.initials: EE
authors.lastname: Fibuch
authors.forename: John Q
authors.initials: JQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D047468:Immunoprecipitation; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D008387:Marine Toxins; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D010648:Phenylacetates / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D013912:Threonine / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation
chemical_list: C107349:2-chloro-5-hydroxyphenylglycine; D018690:Excitatory Amino Acid Agonists; C578937:Grm5 protein, rat; D008387:Marine Toxins; D010080:Oxazoles; D010455:Peptides; D010648:Phenylacetates; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; D019319:Okadaic Acid; D013912:Threonine; D012694:Serine; C079215:3,5-dihydroxyphenylglycine; C059041:calyculin A; D011505:Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D005998:Glycine