Identification and Characterization of a Rat Macrophage Inflammatory Protein-1α Receptor

A macrophage inflammatory protein-1α (MIP-1α) receptor has been cloned from rat (Rattus norvegicus) genomic DNA by PCR using oligonucleotides based on the mouse CCR1 DNA sequence and expressed in HEK293 cells to enable its characterization. The receptor was cloned three times in independent experiments to generate a consensus sequence. The rat ccr1 receptor amino acid sequence is 92% identical to mouse and 80% identical to human CCR1. A consensus clone was transfected into HEK293 cells using the expression vector pIRES, and stable receptor expressing cell lines were isolated. In competitive receptor binding assays using iodinated human MIP-1α, rat ccr1 binds hMIP1α, hMIP-1β, and hMCP-3, but not hRANTES or human interleukin-8 (hIL-8). We have been unable to demonstrate calcium mobilization by rat ccr1 in HEK293 cells using human chemokines as ligands. Therefore, we have adopted lowercase nomenclature for the receptor until signaling is observed. This receptor and cell line may be of use in the preclinical development of CCR1 antagonists.