ChemiScreenHuman CGRP1 Calcitonin Receptor Membrane Preparation

Full-length human CALCRL and RAMP1 cDNAs encoding CGRP1

The calcitonin family of peptides, which includes calcitonin, two calcitonin-related gene peptides (CGRPs), adrenomedullin, and amylin, share a disulfide-bonded loop, an amphipathic a-helix, and an amidated C-terminus. The peptides influence a variety of physiological effects, including vascular tone, food intake and bone metabolism. The biological effects of the peptides are mediated by two class B GPCRs, CT receptor (calcitonin receptor) and CL receptor (calcitonin receptor-like receptor) (Poyner et al., 2002). The pharmacology of the CT and CL receptors is strongly influenced by their association with a family of three receptor activity modifying proteins (RAMPs), which are 14-17 kD single pass transmembrane proteins. CGRP (calcitonin gene-related peptide) induces vasodilation, and its activity is primarily mediated by CGRP1, composed of CL in complex with RAMP1 (Hasbak et al., 2003). As a consequence of its role as a vasodilator, CGRP acting via CGRP1 appears to play an important role in hypertension (Deng and Li, 2005). Millipore′s CGRP1 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 CGRP1 interactions with CGRP. The membrane preparations exhibit a Kd of 1.1-1.7 nM for [¹²⁵I]-hCGRP. With 5 µg/well CGRP1 Membrane Prep and 1 nM [¹²⁵I]-hCGRP, a greater than 15-fold signal-to-background ratio was obtained.

GPCR Class: B

Protein Target: CGRP1

Target Sub-Family: Calcitonin

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, 0.5% BSA. 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, 0.2% BSA, filtered and stored at 4°C
Radioligand: [¹²⁵I] hCGRP (Perkin Elmer # NEX354)
Wash Buffer: 50 mM Hepes, pH 7.4, 500mM NaCl , 0.1% BSA, filtered and stored at 4°C.

One package contains enough membranes for at least 200 assays (units), where an unit is the amount of membrane that will yield greater than 15-fold signal:background with ¹²⁵I-labeled hCGRP at 1 nM. Liquid in packaging buffer: 50 mM Tris pH 7.4, 10% glycerol and 1% BSA with no preservatives. Packaging method: Membranes protein were adjusted to the indicated concentration in packaging buffer, rapidly frozen, and stored at -80°C.

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.

SPECIFICATIONS:
Signal:background and specific binding values obtained in a competition binding assay with varying amounts of CGRP1 membrane prep:

	10 µg/well	5 µg/well
Signal:Background	26.5	29.3
Specific Binding (cpm)	55556	47919

1 unit = 5 µg membrane preparation
Bmax: 10.8 pmol/mg
Kd: 1.4 nM

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