ChemiSCREEN™ Membrane Preparation Recombinant Human D₄ Dopamine Receptor

ChemiSCREEN™ Membrane Preparation Recombinant Human D₄ Dopamine Receptor

• Chemicon (Millipore)
• ChemiScreen

200 units

Full-length human DRD4.4 cDNA encoding the D₄ isoform with 4 andem repeats in the third cytoplasmic loop

The neurotransmitter dopamine is involved in a wide variety of neuroendocrine, emotional, cognitive and locomotor functions. These activities of dopamine are mediated by a group of 5 G protein coupled receptors, 2 of which (D₁ and D₅) couple to G_s and 3 of which (D₂, D₃, D₄) couple to G_i (Missale et al., 1998). The D₄ receptor is highly polymorphic, particularly in the third cytoplasmic loop, which contains from 2 to 7 repeats of 16 amino acids. Individuals with 7 repeats have increased risk of developing ADHD (Thapar et al., 2005). Mice engineered to lack D₄ have reduced locomotor activity, increased sensitivity to drugs of abuse that elevate dopamine (cocaine, methamphetamine and ethanol), and reduced response to novelty (Rubinstein et al., 1997; Dulawa et al., 1999). Millipore's D₄ 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 D₄ interactions and its ligands. The membrane preparations exhibit a Kd of 0.86 nM for [¹²⁵I]- iodospiperone. With 0.5 nM [¹²⁵I]- iodospiperone, 5 μg/well D₄ Membrane Prep yields greater than 6 fold signal-to-background ratio.

Radioligand binding assay and GTPγS binding

Unless otherwise stated in our catalog or other company documentation accompanying the product(s), our products are intended for research use only and are not to be used for any other purpose, which includes but is not limited to, unauthorized commercial uses, in vitro diagnostic uses, ex vivo or in vivo therapeutic uses or any type of consumption or application to humans or animals.

Human

Table 1. Signal:background and specific binding values obtained in a competition binding assay with varying amounts of D₄ membrane prep.

	5 µg/well
Signal:Background	10.7
Specific Binding (cpm)	5996

SPECIFICATIONS: 1 unit = 5 μg membrane preparation
Bmax: 4.45 pmol/mg
Kd: 0.86 nM for [¹²⁵I]-iodospiperone

Chem-1

Chemicon

: Membranes are mixed with radioactive ligand and unlabeled competitor (see Figures 1 and 2 for concentrations tested) in assay buffer in a nonbinding 96-well plate, and incubated for 1-2 h. Prior to filtration, an FC 96-well harvest plate (Millipore cat. # MAHF C1H) is coated with 0.33% polyethyleneimine for 30 min, then washed with 50mM HEPES, 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.

Assay buffer: 50 mM Tris-HCl, pH 7.4, 1 mM EDTA, 5 mM KCl, 1.5 mM CaCl₂, 4 mM MgCl₂, 120 mM NaCl, filtered and stored at 4°C

Radioligand: [¹²⁵I]-iodospiperone (PerkinElmer NEX284)

One package contains enough membranes for at least 200 assays (units), where an unit is the amount of membrane that will yield greater than 6-fold signal:background with [¹²⁵I]-iodospiperone at 0.5 nM.

Chem-1

Liquid in packaging buffer: 50 mM Tris pH 7.4, 10% glycerol and 1% BSA with no preservatives.
Packaging method: Membrane protein was adjusted to the indicated concentration in packaging buffer, rapidly frozen, and stored at -80°C.

D4

non-peptide

Store at –70°C. Product is stable for at least 6 months from the date of receipt when stored as directed. Do not freeze and thaw.

Dopamine

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A

GPCR Membrane Preparations

ChemiSCREEN™ Membrane Preparation Recombinant Human D₄ Dopamine Receptor

NM_0000797

GPCR