ChemiSCREEN Membrane Preparation Recombinant Human CXCR5 Chemokine Receptor

CXCR5 (also known as BLR1) is a GPCR that binds selectively to the chemokine CXCL13 (also known as BLC and BCA-1) to mediate immune system development and function (Förster et al., 1996; Gunn et al., 1998). CXCR5 cooperates with CCR7 to determine functional organization of lymphoid organs such as lymph nodes and Peyer’s patches (Ohl et al., 2003). In addition, CXCR5 mediates migration of B cells into the follicles of the splenic white pulp, thus permitting antigen deposition on follicular dendritic cells (Förster et al., 1996; Cinamon et al., 2008). Patients with rheumatoid arthritis (RA) displayed upregulated expression of CXCR5 to a greater extent than other chemokine receptors, and CXCR5-null mice subjected to antigen-induced arthritis display reduced joint destruction (Schmutz et al, 2004; Wengner et al, 2007). Therefore, CXCR5 represents a potential target for treatment of rheumatoid arthritis. Millipore′s CXCR5 Membrane Preparation for GTPγS Assay is a crude membrane preparation made from the proprietary stable recombinant cell line that is also used for Millipore’s CXCR5 Calcium Optimized Cell Line (HTS055C). This CXCR5 Membrane Preparation has been optimized for low basal activity in GTPγS binding assays; thus it is an ideal HTS tool for screening of compounds for agonist and antagonist activities. The membrane preparations exhibits EC50 of 1.8 nM for CXCL13 in a GTPγS binding assay.

Human CXCR5

Protein Target: CXCR5

Inucbation Conditions
Membranes are permeabilized by addition of saponin to an equal concentration by mass, then mixed with [³⁵S]-GTPγS (final concentration of 0.3 nM) in 20 mM HEPES, pH 7.4/100 mM NaCl/10 mM MgCl2/0.5 μM GDP in a nonbinding 96-well plate. Unlabeled CXCL13 was added to the final concentration indicated in Figure 1 (final volume 100 μL), and incubated for 30 min at 30°C. The binding reaction is transferred to an FB filter plate (Millipore MAHF B1H) previously prewetted with water. The plate is washed 3 times (1 mL per well per wash) with cold 10 mM sodium phosphate, pH 7.4, then dried and counted.

One package contains enough membranes for at least 200 assays (units), where one unit is the amount of membrane that will yield greater than 1000 cpm specific CXCL13-stimulated [³⁵S]-GTPγS binding.

1 unit = 5 μg
EC50 in GTPγS binding assay by CXCL13: ~ 1.8 nM

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