ChemiSCREEN Membrane Preparation Recombinant Human GLP-1

Glucagon-like peptide-I (GLP-1), a member of the glucagon-secretin peptide family, is secreted from L-cells of the small intestine and binds to a class B (class 2) G protein-coupled receptor (Mayo et al. 2003). The GLP-1 receptor is expressed in pancreatic beta cells and upon binding to GLP-1, it couples to G_s to increase cAMP levels and insulin secretion (Drucker et al. 1987). In addition, GLP-1 has been shown to delay gastric emptying and regulate appetite. Therefore, the GLP-1 receptor represents an important therapeutic target for type II diabetes, and a degradation-resistant analog of GLP-1, exanatide, is used clinically in combination with other glucose-lowering drugs to control type II diabetes (D’Alessio et al. 2004). Millipore′s GLP-1 receptor 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 for agonists and antagonists at the GLP-1 receptor. The membrane preparations exhibit a Kd of 0.27 nM for [¹²⁵I]-GLP-1. With 10 μg/well GLP-1 Receptor Membrane Prep and 0.5 nM [¹²⁵I]-GLP-1, a greater than 9-fold signal-to-background ratio was obtained.

Human GLP-1

Radioligand binding assay, and GTPγS binding.

GPCR Class: B

Protein Target: GLP-1

Target Sub-Family: Glucagon

SPECIFICATIONS:
Signal:background and specific binding values obtained in a competition binding assay with varying amounts of GLP-1 membrane prep:

	20 µg/well	10 µg/well
Signal:Background	12.0	14.9
Specific Binding (cpm)	31366	27411

1 unit = 10 µg membrane preparation


Bmax: 3.96 pmol/mg


Kd: 0.27 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, 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] GLP-1(7-36) (Perkin Elmer # NEX308)
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 9-fold signal:background with ¹²⁵I-labeled GLP-1 at 0.5 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.

Maintain frozen at -70°C for up to 2 years. Do not freeze and thaw.

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