Assay Method Information

Assay Name:  [35S]GTPγS Binding Assay
Description:  Measurement of mGluR2 positive allosteric modulatory activity of test compounds in membranes containing human mGluR2 was performed using frozen membranes that were thawed and briefly homogenized prior to pre-incubation in 96-well microplates (15 μg/assay well, 30 minutes, 30° C.) in assay buffer (50 mM HEPES pH 7.4, 100 mM NaCl, 3 mM MgCl2, 50 μM GDP, 10 μg/ml saponin,) with increasing concentrations of positive allosteric modulator (from 0.3 nM to 50 μM) and either a minimal pre-determined concentration of glutamate (PAM assay), or no added glutamate. For the PAM assay, membranes were pre-incubated with glutamate at EC25 concentration, i.e. a concentration that gives 25% of the maximal response glutamate, and is in accordance to published data (Pin et al. (1999) Eur. J. Pharmacol. 375:277-294). After addition of [35S]GTPγS (0.1 nM, f.c.) to achieve a total reaction volume of 200 μl, microplates were shaken briefly and further incubated to allow [35S]GTPγS incorporation on activation (30 minutes, 30° C.). The reaction was stopped by rapid vacuum filtration over glass-fibre filter plates (Unifilter 96-well GF/B filter plates, Perkin-Elmer, Downers Grove, USA) microplate using a 96-well plate cell harvester (Filtermate, Perkin-Elmer, USA), and then by washing three times with 300 μl of ice-cold wash buffer (Na2PO4.2H2O 10 mM, NaH2PO4.H2O 10 mM, pH=7.4).
Affinity data for this assay
 

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