Molecular Cloning and Characterization of a cDNA, CHEMR1, Encoding a Chemokine Receptor With a Homology to the Human C-C Chemokine Receptor, CCR-4

Abstract

Chemokines refer to a rapidly expanding family of small cytokines whose primary function is recruitment of leukocytes to inflammatory sites. These are known to bind to seven-transmembrane-domain containing receptors. A cDNA clone, CHEMR1, resembling the typical G protein-coupled receptor, was isolated from a mouse cytotoxic T-lymphocyte (CTL) library. Northern blot analysis in mouse cell lines suggests that its expression is found in a variety of cells, including T cells, B cells, and macrophages. The CHEMR1 gene Scya3r2 is a single-copy gene whose open reading frame may be in a single exon and maps to the distal region of mouse Chr 9 where the mouse macrophage inflammatory protein-1alpha (MIP-1alpha) receptor gene Scya3r and two related C-C chemokine receptor-like genes reside. Amino acid sequence comparison shows that CHEMR1 is 84% identical to human CCR-4, indicating that CHEMR1 is likely to be a mouse CCR-4. Binding assays using 125I-labeled C-C chemokines in mammalian cells indicated that CHEMR1 did not bind MIP-1alpha, RANTES, or MIP-1beta, whereas CCR-1 binds MIP-1alpha and RANTES. Our result is different from the reported properties of human CCR-4. This suggests that CHEMR1 may be a receptor for unidentified C-C chemokine or a low-affinity receptor for MIP-1alpha.