title: Group-I metabotropic glutamate receptors, mGlu1a and mGlu5a, couple to extracellular signal-regulated kinase (ERK) activation via distinct, but overlapping, signalling pathways.
abstract: The coupling of the group I metabotropic glutamate receptors, mGlu1a and mGlu5a, to the extracellular signal-regulated protein kinase (ERK) pathway has been studied in Chinese hamster ovary cell-lines where receptor expression is under inducible control. Both mGlu receptors stimulated comparable, robust and agonist concentration-dependent ERK activations in the CHO cell-lines. The mGlu1a receptor-mediated ERK response was almost completely attenuated by pertussis toxin (PTx) pretreatment, whereas the mGlu5a-ERK response, and the phosphoinositide response to activation of either receptor, was PTx-insensitive. mGlu1a and mGlu5a receptor coupling to ERK occurred via mechanisms independent of phosphoinositide 3-kinase activity and intracellular and/or extracellular Ca2+ concentration. While acute treatment with a protein kinase C (PKC) inhibitor did not attenuate agonist-stimulated ERK activation, down-regulation of PKCs by phorbol ester treatment for 24 h did attenuate both mGlu1a and mGlu5a receptor-mediated responses. Further, inhibition of Src non-receptor tyrosine kinase activity by PP1 attenuated the ERK response generated by both receptor subtypes, but only mGlu1a receptor-ERK activation was attenuated by PDGF receptor tyrosine kinase inhibitor AG1296. These findings demonstrate that, although expressed in a common cell background, these closely related mGlu receptors utilize different G proteins to cause ERK activation and may recruit different tyrosine kinases to facilitate this response.
authors.affiliation: Department of Cell Physiology and Pharmacology, University of Leicester, University Road, Leicester, UK.
authors.forename: Sukhwinder
authors.initials: S
authors.lastname: Thandi
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Blank
authors.forename: R A John
authors.initials: RA
authors.lastname: Challiss
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005260:Female; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D010053:Ovary / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D016318:Quisqualic Acid / Q000494:pharmacology; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
chemical_list: D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D016318:Quisqualic Acid; D037342:Pertussis Toxin; D017479:Receptors, Platelet-Derived Growth Factor; D019061:src-Family Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium