| Assay Method Information | |
| | [35S]GTPgammaS Binding |
| Description: | The human APJ receptor was cloned by polymerase chain reaction and the gene encoding the receptor was subcloned in pFLAG-CMV -3 expression vector (Sigma, Saint Louis, Mo. USA) in-house at Amgen. A GTPγS binding assay was performed on membranes prepared from CHO cells stably expressing human APJ receptor. The optimum experimental conditions for the concentrations of GDP, MgCl2, and NaCl in the assay buffer were initially determined. The assay was performed in 9 μL assay buffer [20 mM HEPES, pH 7.5, 5 mM MgCl2, 100 mM NaCl and 0.1% (w/v) BSA], 1 μL of diluted test compound (starting with 0.75 mM, 2-fold serial dilution with DMSO, total 22 points), 10 μL of 18 μM GDP (final concentration of 3 μM GDP), 20 μL of 0.25 μg/mL membrane protein expressing human APJ receptor captured with WGA PS beads (final concentration of 5 μg per well), and 20 μL of 0.3 nM [35S]GTPγS (final concentration is 0.1 nM [35S]GTPγS)(Perkin Elmer Life and Analytical Sciences, Waltham USA). One column of the plate was 1 μL of DMSO as background and another column of the plate was 1 μL of 180 μM Pyr-Apelin-13 which was used as control at a final concentration of 3 μM. Incubation was at RT for 90 min and the microplate was read using a ViewLux ultra HTS Microplate Imager (PerkinElmer, Inc.). All the results presented are means of several independent experiments and analyzed by non-linear regression methods using the commercially available program Prism (GraphPad, San Diego, Calif.) providing the EC50 values detailed in Table 40. |
| Affinity data for this assay | |
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