Regulation of MAPK/ERK phosphorylation via ionotropic glutamate receptors in cultured rat striatal neurons

Abstract

Extracellular signals may regulate mitogen-activated protein kinase (MAPK) cascades through a receptor-mediated mechanism. As a signaling superhighway to the nucleus, active Ras-MAPK cascades phosphorylate transcription factors and facilitate gene expression. In cultured rat striatal neurons, the present work systemically examined the linkage between glutamate receptors and the extracellular signal-regulated kinase 1/2 (ERK1/2) subclass of MAPK. We found that glutamate induced a rapid and transient phosphorylation of ERK1/2. Similar responses of ERK1/2 phosphorylation were also induced by the ligands selective for each of three subtypes of ionotropic receptors (NMDA, AMPA and kainate), although not by the subgroup-selective agonists for three subgroups of metabotropic glutamate receptors after 8-9 days in culture. The ERK1/2 phosphorylation induced by all ionotropic receptor agents was dose-, time- and Ca(2+) influx-dependent and occurred in neurons, but not glia. The NMDA-, AMPA- and kainate-induced ERK1/2 phosphorylation was blocked only by the antagonists selective for respective subtypes. The ERK1/2 phosphorylation induced by these agents was also sensitive to the MAPK kinase 1 (MEK1) inhibitor PD98059 and the MEK1/2 inhibitor U0126. In a further attempt to evaluate the role of active ERK1/2 in activating a downstream transcription factor cAMP response element-binding protein (CREB), NMDA, AMPA, and kainate were found to increase CREB phosphorylation. The NMDA- and AMPA/kainate-induced CREB phosphorylation was completely and partially blocked by U0126, respectively. These results revealed a positive linkage between ionotropic glutamate receptors and MEK-sensitive ERK1/2 phosphorylation in striatal neurons. The active ERK1/2 cascade activates the downstream transcription factor CREB to participate in the regulation of gene expression.

Zn2+-dependent Activation of the Trk Signaling Pathway Induces Phosphorylation of the Brain-enriched Tyrosine Phosphatase STEP

“…To ensure the efficacy of the pharmacological inhibitors in the above experiments, in control studies neurons were treated with glutamate (100 M, 5 min) in the presence of MK801 or APV; kainic acid (100 M, 5 min) in the presence of CNQX; or KCl (60 mM, 5 min) in the presence of nifedipine and analyzed for phosphorylation of ERK2. Consistent with earlier findings (21,38,39) each of these pharmacological inhibitors effectively blocked glutamate, kainic acid, or KCl-mediated phosphorylation of ERK2 (Fig. 5, E and F).…”

Metabotropic Glutamate Receptors and Dopamine Receptors Cooperate to Enhance Extracellular Signal-Regulated Kinase Phosphorylation in Striatal Neurons

“…We used primary striatal cultures to minimize circuit-based interactions that might confound our analysis. Because the properties of some receptors can change dramatically under different culture conditions (Mao et al, 2004), we first established that mGluR1/5 activation was coupled to calcium mobilization in our cultures. Calcium concentrations increased throughout the cell in response to DHPG and exhibited oscillatory behavior typical of mGluR5 (Flint et al, 1999) (data not shown).…”

A Signaling Mechanism from Gαq-Protein-Coupled Metabotropic Glutamate Receptors to Gene Expression: Role of the c-Jun N-Terminal Kinase Pathway

“…Agonist ligands for ionotropic glutamate receptors (NMDA or AMPA) or for group I mGluRs increased striatal ERK1/2 phosphorylation via distinct signaling mechanisms involving Ca 2ϩ -sensitive or Ca 2ϩ -insensitive kinases (Sgambato et al, 1998;Perkinton et al, 1999Perkinton et al, , 2002; Vanhoutte et al, 1999;Thandi et al, 2002;Mao et al, 2004Mao et al, , 2005aYang et al, 2004). Similarly, glutamate increased JNK phosphorylation on their Thr 183 and Tyr 185 sites in striatal neurons (Schwarzschild et al, 1997;Mukherjee et al, 1999;Vanhoutte et al, 1999;Crossthwaite et al, 2004).…”