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TAK-779, a Specific Inhibitor of HIV-1 Entry, Binds within a Pocket Formed by the Trans-Membrane Domains of CCR5 T. DRAGIC*1, S. LIN2, A. TRKOLA3, D. A. D. THOMSPON1, E. G. CORMIER1, F. KAJUMO1, W. YING4, S. O. SMITH4, T. P. SAKMAR2, and J. P. MOORE3. 1Albert Einstein Coll. of Med., Bronx, NY; 3Aaron Diamond AIDS Res. Ctr., The Rockefeller Univ., New York, NY; 2Howard Hughes Med. Inst., The Rockefeller Univ., New York, NY; and 4State Univ. of New York at Stony Brook, NY TAK-779 is a small molecule inhibitor of R5, but not X4, HIV-1 replication in PBMC. It also blocks RANTES binding to CCR5 and MCP-1 binding to CCR2b, but is inactive on CCR1, CCR3 and CCR4 (Baba et al., PNAS 96, 5698-5703, 1999). To better understand structure-function relationships within CCR5, we have performed a series of studies to identify the TAK-779 binding site. After confirming that TAK-779 inhibited R5 HIV-1 replication at the virus entry stage, we showed that this compound inhibits the binding of gp120JR-FL to CCR5 with an IC90 of 30nM. Alanine-scanning mutagenesis then revealed that substitutions within the extracellular domains of CCR5, including the N-terminus, did not affect the antiviral activity of TAK-779. This suggested that TAK-779 might be interacting with residues in the TM domains. We therefore used a molecular model of CCR5, based on the tertiary structure of the rhodopsin TM domains, to predict the sites of additional alanine substitutions. Among the thirty-eight alanine substitutions in the TM domains of CCR5 that we tested, eight significantly lowered the anti-viral activity of TAK-779, suggesting that they disrupted the compound's binding site. Although these ten residues are distributed among four of the seven TM helices of CCR5, the molecular model shows that all ten are topologically clustered around a small pocket that is located between the TM helices. Characterization of this binding pocket might facilitate the development of drugs to prevent co-receptor-mediated HIV-1 entry. Key Words: entry, inhibitor, TAK-779 |
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© 7th
Conference on Retroviruses and Opportunistic Infections, |