CCR5

CCR5 is a human CC chemokine receptor and G protein-coupled receptor that responds to chemokines including RANTES/CCL5, MIP-1α/CCL3, and MIP-1β/CCL4[1]. Mechanistically, ligand-bound CCR5 couples to Gᵢ1 and supports chemokine recognition, receptor activation, immune surveillance, and inflammation[2]. In HIV research models, CCR5 functions as the principal cofactor for entry mediated by envelope glycoproteins of primary macrophage-tropic HIV-1 strains[3]. CCR5, when coexpressed with CD4, enables infection by most primary HIV-1 isolates, whereas CCR3 supports only a more restricted subset, defining an experimentally important distinction from related chemokine receptors[4]. A homozygous CCR5 defect was identified in some multiply exposed individuals resistant to HIV-1 infection, linking receptor expression to viral-entry susceptibility[5]. Compared with related isoforms CCR1 and CCR3, natural LD78β/MIP-1α isoforms show diverging binding capacities that affect CCR5-linked anti-HIV activity and CCR1/CCR3-linked chemotactic responses. For inhibitor studies, maraviroc-bound CCR5 reveals a ligand-binding site distinct from chemokine and gp120 recognition sites, supporting allosteric inhibition of chemokine signaling and viral entry[6]. Maraviroc is a CCR5 antagonist used to block gp120 interaction with CCR5 in HIV/AIDS research and treatment contexts[7].