Role of Protein Phosphatase 2A in mGluR5-regulated MEK/ERK Phosphorylation in Neurons

• Published in: The Journal of biological chemistry 2005-04, Vol.280 (13), p.12602-12610
• Main Authors: Mao, Limin, Yang, Lu, Arora, Anish, Choe, Eun Sang, Zhang, Guochi, Liu, Zhenguo, Fibuch, Eugene E., Wang, John Q.
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Brain - cytology; Brain - metabolism; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Excitatory Amino Acid Agonists - pharmacology; Glycine - analogs & derivatives; Glycine - pharmacology; Immunoprecipitation; MAP Kinase Kinase 1 - metabolism; Marine Toxins; Microscopy, Confocal; Microscopy, Fluorescence; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; Neurons - metabolism; Okadaic Acid - pharmacology; Oxazoles - pharmacology; Peptides - chemistry; Phenylacetates - pharmacology; Phosphoprotein Phosphatases - metabolism; Phosphoprotein Phosphatases - physiology; Phosphorylation; Protein Phosphatase 2; Protein Structure, Tertiary; Protein-Tyrosine Kinases - metabolism; Rats; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate - metabolism; Resorcinols - pharmacology; Serine - metabolism; Signal Transduction; Threonine - metabolism; Time Factors; Up-Regulation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M411709200

The regulation of protein phosphorylation requires coordinated interaction between protein kinases and protein phosphatases (PPs). Recent evidence has shown that the Gαq-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.