ChemiSCREEN Human D₃ Dopamine Receptor Membrane Preparation

Table 1. Signal:background and specific binding values obtained in a competition binding assay with varying amounts of D3 Receptor membrane prep.

	10 µg/well	5 µg/well
Signal:Background	4.88	5.93
Specific Binding (cpm)	1853.7	1861.3

SPECIFICATIONS: 1 unit = 5 µg membrane preparation
Bmax: 0.32 pmol/mg
Kd: 0.1 nM

Human D3 GPCR membrane preparation for Radioligand binding Assays & GTPγS binding.

Protein Target: D3

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 Tris, pH 7.4. 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 Tris, pH 7.4, 120mM NaCl, filtered and stored at 4°C
Radioligand: [125I] -Iodospiperone(Perkin Elmer # NEX284)
Wash Buffer: 50 mM Tris, pH 7.4, filtered and stored at 4°C.

Dopamine is a catecholamine neurotransmitter that functions in the CNS to control locomotor, cognitive, emotional and neurendocrine processes, and in the periphery to modulate cardiovascular, renal and gastrointestinal processes. The biological activities of dopamine are mediated by a family of five GPCRs. The D1 and D5 subtypes couple to Gs to increase intracellular cAMP, whereas the D2, D3 and D4 subtypes couple to Gi to reduce cAMP (Missale et al., 1998). The dopamine D3 receptor is expressed in phylogenetically older regions of the brain, suggesting that it plays a role in cognitive and emotional functions. It has been the target of potential drugs for psychotic disorders and Parkinson′s disease. Chemicon′s D3 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 antagonists of D3 interactions and its ligands. The membrane preparations exhibit a Kd of 0.1 nM for [125I]-Iodospiperone. With 5.0ug/well D3 membrane prep and 0.1 nM [125I]-Iodospiperone, a greater than 4-fold signal-to-background ratio was obtained.

Human D3 Receptor

One package contains enough membranes for at least 200 assays (units), where an unit is the amount of membrane that will yield greater than 4-fold signal:background with 125I-labeled Iodospiperone at 0.1 nM.

Liquid in packaging buffer: 50 mM Tris, pH 7.4, 10% glycerol with no preservatives.
Packaging method: Membranes protein was adjusted to the indicated concentration in packaging buffer, rapidly frozen, and stored at -80oC.

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