CCR5 CORECEPTOR UTILIZATION INVOLVES A HIGHLY CONSERVED ARGININE RESIDUE OF HIV TYPE-1 GP120

The seven-transmembrane CCR5 was recently found to double as a corecep tor for a genetically diverse family of human sand nonhuman primate le ntiviruses. Paradoxically, the main region of the envelope protein bel ieved to be involved in CCR5 utilization was mapped to hypervariable r egion 3, or V3, of the envelope glycoprotein gp120. In this study, we addressed the question of whether functional convergence in CCR5 utili zation is mediated by certain V3 residues that are highly conserved am ong MV type a (HIV-1), HIV type 2, and simian immunodeficiency virus. Site-directed mutagenesis carried out on three such V3 residues reveal ed that the Arg-298 of HIV-1 gp120 has an important role in CCR5 utili zation, In contrast, no effect was observed for the other residues we tested. The inability of Arg-298 mutants to use CCR5 was not attribute d to global alteration of gp120 conformation. Neither the expression, processing, and incorporation of mutant envelope proteins into virions , nor CD4 binding were significantly affected by the mutations. This i nterpretation is further supported by the finding that alanine substit utions of five residues immediately adjacent to the arginine residue h ad no effect on CCR5 utilization. Taken together, our data strongly su ggests that the highly conserved Arg-298 residue identified in the V3 of HIV-1 has a significant role in CCR5 utilization, and may represent an unusually conserved target for future anti-viral designs.