ChemiScreen Membrane Preparation
Recombinant Human SST4 SOMATOSTATIN RECEPTOR

Human SSTR4 encoding SST4

Somatostatin is a 14 or 28 amino acid regulatory peptide that inhibits hormone secretion from the pituitary, pancreas, and other endocrine sites. A family of 6 GPCRs, sst1, sst2A, sst2B, sst3, sst4 and sst5, mediate the biological activity of somatostatins. The somatostatin receptors couple to Gi to inhibit cAMP production, and also increase MAP kinase signalling. Several tumors have been shown to overexpress somatostatin receptors, and binding of somatostatin to these tumor cells stimulates or inhibits proliferation, depending on the receptor subtypes expressed (Olias et al., 2004). Somatostatin has been implicated in seizure susceptibility in animal models, and activation of sst4 with selective agonists increases seizure activity (Moneta et al., 2002). Chemicon′s SST4 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 SST4 interactions with somatostatin. The membrane preparations exhibit a Kd of 1.78 nM for [¹²⁵I]-Somatostatin 14. With 5 ug/well SST4 Membrane Prep and 1 nM [¹²⁵I]-Somatostatin 14, a greater than 20-fold signal-to-background ratio was obtained.

Human sst4 GPCR membrane preparation for Radioligand binding Assays & GTPγS binding.

Radioligand binding assay, and GTPγS binding.

GPCR Class: A

Protein Target: sst4

Target Sub-Family: Somatostatin

200 units

SPECIFICATIONS: 1 unit = 5 μg membrane preparation
Bmax: 28.2 pmol/mg
Kd: 1.78 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 50 mM 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]-Somatostatin 14 (Perkin Elmer # NEX389)
Wash Buffer: 50 mM Hepes, pH 7.4, 500 mM 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 20-fold signal:background with ¹²⁵I-labeled somatostatin 14 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.

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

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