CHEMBL5735308

GTPγS binding test: CHO cells stably expressing human metabotropic glutamate receptors mGluR2 and mGluR3 were cultured at 37° C. under 5% CO2 using a Dulbecco's modified Eagle medium [1% proline, 1 mM sodium pyruvate, 1 mM succinic acid, 1 mM disodium succinate, 100 units/mL penicillin, 100 μg/mL streptomycin, 400 (mGluR2) or 300 (mGluR3) μg/mL hygromycin B, 2 mM L-glutamine (added just before use)] containing 10% dialyzed fetal bovine serum. The cells in a confluent state were washed with PBS(−), then dissociated using a cell scraper, and centrifuged at 1000 rpm for 5 minutes at 4° C. to recover the cells. The obtained pellet was suspended in a 20 mM HEPES buffer (pH 7.4) (mGluR2) or 20 mM HEPES buffer containing 1 mM EDTA (pH 7.4) (mGluR3), and the suspension was homogenized in a Teflon® homogenizer and then centrifuged at 48,000×g for 20 minutes at 4° C. to obtain a pellet again. The obtained pellet was subjected to two additional cycles of washing and centrifugation and then homogenized with the buffer described above to obtain a crude membrane fraction. The crude membrane fraction was diluted with a buffer for a binding test (final concentration: 20 mM HEPES, 100 mM NaCl, 10 mM MgCl2, 10 μM GDP, 10 ng/mL saponin, 0.1% BSA) (mGluR2) or (final concentration: 20 mM HEPES, 1 mM EDTA, 100 mM NaCl, 10 mM MgCl2, 10 μM GDP, 10 μg/mL saponin, 0.1% BSA) (mGluR3). To the crude membrane fraction containing 10 μg of membrane proteins/assay, Compounds (II)-1 to (II)-15 were each added, and the mixture was incubated at 30° C. for 20 minutes. Then, glutamate (final concentration: 20 (mGluR2) or 1 (mGluR3) μM) and [35S]GTPγS (final concentration: 0.15 nM) were added thereto, and the mixture was incubated at 30° C. for 1 hour. The solution thus incubated was filtered by suction onto Whatman GF/C filter, and the filter was washed with 1000 μL of an ice-cooled 20 mM HEPES buffer (pH 7.4) (mGluR2) or 20 mM HEPES buffer containing 1 mM EDTA (pH 7.4) (mGluR3). A scintillation cocktail was added to the obtained filter, and the membrane binding radioactivity was measured using a liquid scintillation counter. The residual radioactivity in the absence of glutamate was defined as nonspecific binding, and the difference from the residual radioactivity in the presence of glutamate was defined as specific binding.