| Assay Method Information | |
| | Fluorescence polarization assay |
| Description: | Rhesus PDE9A2 was amplified from rhesus whole brain cDNA (Biochain Institute) essentially as described in Hutson, et al. Neuropharmacology (2011) 61(4):665-676. HEK 293 or CHO cells over-expressing rhesus or rat PDE9A2 (created by DiscoverX from mRNA Genbank accession # NM_138543) respectively were lysed in 20 mM HEPES, 1 mM EDTA buffer with protease inhibitors (Roche, Indianapolis, Ind.). After brief homogenization, cells were pelleted via centrifugation at 75,000×g for 20 min at 4° C. The pellets were re-suspended, centrifuged and re-pelleted again in the same manner. The membrane fraction was collected in 20 mM HEPES, 1 mM MgCl2 with protease inhibitors. Human PDE9 (PDE9A2, GenBank Accession No. NM_001001567), full length with N-terminal GST tag, was purchased from BPS Bioscience. The fluorescence polarization assay for cyclic nucleotide phosphodiesterases was performed using an IMAP FP kit supplied by Molecular Devices, Sunnyvale, Calif. (product # R8139). IMAP technology has been applied previously to phosphodiesterase assays (Huang, W., et al., J. Biomol Screen, 2002, 7: 215). Assays were performed at room temperature in 384-well microtiter plates with an incubation volume of 20.2 μL. Solutions of test compounds were prepared in DMSO and serially diluted with DMSO to yield 8 μL of each of 10 solutions differing by 3-fold in concentration, at 32 serial dilutions per plate. 100% inhibition is determined using a known PDE9 inhibitor, such as 1-(2-chlorophenyl)-6-[(2R)-3,3,3-trifluoro-2-methylpropyl]-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidine-4-one (BAY 73-6691) (Wunder et al, Mol. Pharmacol., 2005, 68(6): 1775-81), (6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (PF-04447943) (Wager et al., ACS Chemical Neuroscience, 2010, 1:435-449). 0% of inhibition is determined by using DMSO (1% final concentrations). A Labcyte Echo 555 (Labcyte, Sunnyvale, Calif.) is used to dispense 200 nL from each well of the titration plate to the 384 well assay plate. Rhesus membrane preps were diluted to 4 ng/ml, rat membrane preps diluted to 13 ng/ml, and human PDE9A2 diluted to 1 ng/ml. FAM-labeled cGMP substrate (Molecular Devices, Sunnyvale, Calif.) was at a concentration of 100 nM (Km of PDE9 for cGMP is 70-170 nM) in the assay buffer (10 mM Tris HCl, pH 7.2, 10 mM MgCl2, 0.05% NaN3 0.01% Tween-20, and 1 mM DTT). PDE9 enzyme mix and compounds were mixed and incubated at room temperature for 30 min. Following which, FAMcGMP substrate was added, shaken and incubated for an additional 60 min at room temperature. The final concentrations of rhesus and rat membrane preparations were 2 ng/ml and 6.5 ng/ml, respectively, while the human PDE9 was used at a final concentration of 0.5 ng/ml. The final concentration of FAM-cGMP was 50 nM. After the incubation period, the enzymatic reaction was stopped by addition of binding solution (IMAP-FP, Molecular Devices, comprised of 80% Solution A, 20% Solution B and a 1:600 dilution of binding reagent) to each well. The plates were shaken then incubated at room temperature for 1 h prior to determining the fluorescence polarization (mP) using a Perkin Elmer EnVision plate reader (Waltham, Mass.). |
| Affinity data for this assay | |
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