ChemiSCREEN Membrane Preparation Recombinant Human EP₂ Prostanoid Receptor

Full-length human PTGER2 cDNA encoding EP₂

Prostanoids bind to a family of 8 GPCRs to exert their biological effects (Narumiya and FitzGerald, 2001). The protanoid PGE₂ causes pain, vasodilation, immunosuppression of T cells, bone resorption and promotion of carcinogenesis. Four related GPCRs, EP₁, EP₂, EP₃ and EP₄, each bind to PGE₂, but the different G protein coupling status of each receptor leads to distinct biological effects. EP₂ couples primarily to Gs to increase intracellular cAMP levels. Mice deficient in EP₂ receptor showed impaired ovulation and fertilization, salt-sensitive hypertension (Kennedy et al., 1999). It has been shown that EP₂ receptors are also involved in cancer associated immunodeficiency. Thus, genetic knockout of the EP₂ receptor reduced tumor growth and prolonged survival in mice that had undergone isograft injection of MC26 or Lewis lung carcinoma cells (Yang et al., 2003). Millipore′s EP₂ membrane preparations are crude membrane preparations made from our proprietary stable recombinant cell lines to ensure high-level of GPCR surface expression; thus, they are ideal HTS tools for screening of agonists and antagonists of EP₂. The membrane preparations exhibit a Kd of 14.52 nM for [³H]-PGE₂. With 7.5 nM [³H]-PGE₂, 10µg/well EP₂ Membrane Prep typically yields greater than 3-fold signal-to-background ratio.

Human EP2 GPCR membrane preparation for Radioligand binding Assays & GTPγS binding.

Table 1. Signal:background and specific binding values obtained in a competition binding assay with varying amounts of EP₂ Receptor membrane prep.

	10 µg/well
Signal:Background	3.60
Specific Binding (cpm)	1146

1 unit = 10 µg
Bmax for [³H]-PGE₂ binding: 4.38 pmol/mg protein
Kd for [³H]-PGE₂ binding: ~14.52 nM

Inucbation Conditions
Membranes are mixed with radioactive ligand and unlabeled competitor (see Figures 1 and 2 for concentrations tested) in binding buffer in a nonbinding 96-well plate, and incubated for 1-2 h. Prior to filtration, a GF/C 96-well filter plate is coated with 0.33% polyethyleneimine for 30 min, then washed with 50mM HEPES, pH 7.4, 500mM NaCl. Binding reaction is transferred to the filter plate, and washed 3 times (1 mL per well per wash) with Wash Buffer. The plate is dried and counted.
Binding buffer: 50 mM Hepes, pH 7.4, 5 mM MgCl₂, 1 mM CaCl₂, filtered and stored at 4°C.
Radioligand: [³H]-PGE₂ (Perkin Elmer#: NET-428)
Wash Buffer: 50 mM Hepes, pH 7.4, 500mM NaCl, filtered and stored at 4°C.

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