Amino-Terminal Substitutions in the CCR5 Coreceptor Impair gp120 Binding and Human Immunodeficiency Virus Type 1 Entry |
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Authors: | Tatjana Dragic Alexandra Trkola Steven W Lin Kirsten A Nagashima Francis Kajumo Lu Zhao William C Olson Lijun Wu Charles R Mackay Graham P Allaway Thomas P Sakmar John P Moore and Paul J Maddon |
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Institution: | Aaron Diamond AIDS Research Center, The Rockefeller University, New York, New York 100161.; Howard Hughes Medical Institute, The Rockefeller University, New York, New York 100212.; Progenics Pharmaceuticals, Inc., Tarrytown, New York 105913.; and Leukosite Inc., Cambridge, Massachusetts 021424. |
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Abstract: | The CC-chemokine receptor CCR5 is required for the efficient fusion of macrophage (M)-tropic human immunodeficiency virus type 1 (HIV-1) strains with the plasma membrane of CD4+ cells and interacts directly with the viral surface glycoprotein gp120. Although receptor chimera studies have provided useful information, the domains of CCR5 that function for HIV-1 entry, including the site of gp120 interaction, have not been unambiguously identified. Here, we use site-directed, alanine-scanning mutagenesis of CCR5 to show that substitutions of the negatively charged aspartic acid residues at positions 2 and 11 (D2A and D11A) and a glutamic acid residue at position 18 (E18A), individually or in combination, impair or abolish CCR5-mediated HIV-1 entry for the ADA and JR-FL M-tropic strains and the DH123 dual-tropic strain. These mutations also impair Env-mediated membrane fusion and the gp120-CCR5 interaction. Of these three residues, only D11 is necessary for CC-chemokine-mediated inhibition of HIV-1 entry, which is, however, also dependent on other extracellular CCR5 residues. Thus, the gp120 and CC-chemokine binding sites on CCR5 are only partially overlapping, and the former site requires negatively charged residues in the amino-terminal CCR5 domain. |
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