RT Journal Article
SR Electronic
T1 Complex Involvement of Pertussis Toxin-Sensitive G Proteins in the Regulation of Type 1α Metabotropic Glutamate Receptor Signaling in Baby Hamster Kidney Cells
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 352
OP 360
DO 10.1124/mol.58.2.352
VO 58
IS 2
A1 Hermans, Emmanuel
A1 Saunders, Ruth
A1 Selkirk, Julie V.
A1 Mistry, Rajendra
A1 Nahorski, Stefan R.
A1 Challiss, R. A. John
YR 2000
UL http://molpharm.aspetjournals.org/content/58/2/352.abstract
AB Previously, we demonstrated that the coupling of the metabotropic glutamate receptor mGlu1α to phosphoinositide hydrolysis is enhanced by pertussis toxin (PTX) in stably transfected baby hamster kidney cells (BHK). Here, we show that the PTX effect on agonist-stimulated [3H]inositol phosphate accumulation can be resolved into two components: an immediate increase in agonist potency, and a more slowly developing increase in the magnitude of the response observed at maximally effective agonist concentrations. Using Gq/11α- and Gi/oα-selective antibodies to immunoprecipitate [35S]guanosine-5′-O-(3-thio)triphosphate-bound Gα proteins, we also show that agonist stimulation of mGlu1α in BHK membranes increases specific [35S]guanosine-5′-O-(3-thio)triphosphate binding to both Gq/11 and Gi/o proteins. Preincubation of BHK-mGlu1α with l-glutamate (300 μM) results in a progressive loss (60% in 30 min) ofl-quisqualate-induced [3H]inositol phosphate accumulation (without a change in potency), providing evidence for agonist-induced receptor desensitization. Although such desensitization of mGlu receptor signaling was mimicked by a phorbol ester, agonist-induced phosphorylation of the receptor was not observed and protein kinase C inhibition by Ro 31-8220 did not preventl-glutamate-mediated desensitization. In contrast, PTX treatment of the cells almost completely preventedl-glutamate-mediated desensitization. Together, these data provide evidence for a multifunctional coupling of mGlu1α to different types of G proteins, including PTX-sensitive Gi-type G proteins. The latter are involved in the negative control of phospholipase C activity while also influencing the rate of desensitization of the mGlu1α receptor.