CHARACTERIZATION OF MACROPHAGE INFLAMMATORY PROTEIN-5 HUMAN CC CYTOKINE-2, A MEMBER OF THE MACROPHAGE-INFLAMMATORY-PROTEIN FAMILY OF CHEMOKINES

A human monocyte-activating CC chemokine has been identified based on sequences in an expressed sequence tag (EST) cDNA database. The protei n shows highest sequence identity to the macrophage inflammatory prote in (MIP) group of chemokines, particularly MIP-3 (76.6%) and MIP-1 alp ha (75.4%), and has been named MIP-5. Model building confirms that the protein has a similar three dimensional structure to other chemokines , but has an additional third disulphide bond. Northern blot analysis and reverse-transcriptase PCR show that the mRNA for MIP-5 expressed a t a high levels in liver, intestine and in lung leukocytes. MIP-5 indu ces chemotaxis of human monocytes, T-lymphocytes and, to a lesser degr ee, eosinophils at nanomolar concentrations; it has no effect on neutr ophil migration. In receptor-binding assays, MIP-5 shows IC50 values o f 12 nM for competition with I-125-MIP-1 alpha for binding to CC-chemo kine receptor (CCR)1, and 2.5 nM for competition with I-125-MCP-3 for binding to CCR3. It shows no ability to compete with ligand for bindin g to the two interleukin (IL)-8 receptors (CXC-chemokine receptors 1 a nd 2) or to CCR2, CCR4 or CCR5. Consistent with this binding data, MIP -5 was only able to induce calcium fluxes in CHO cells stably transfec ted with CCR1 or CCR3.