title: Naturally occurring CCR5 extracellular and transmembrane domain variants affect HIV-1 Co-receptor and ligand binding function.
abstract: Analysis of CCR5 variants in human immunodeficiency virus, type 1 (HIV-1), high risk cohorts led to the identification of multiple single amino acid substitutions in the amino-terminal third of the HIV-1 co-receptor CCR5 suggesting the possibility of protective and permissive genotypes; unfortunately, the low frequency of these mutations did not led to correlation with function. Therefore, we used analytical methods to assess the functional and structural significance of six of these variant receptors in vitro. These studies showed three categories of effects on CCR5 function. 1) Mutations in the first extracellular domain of CCR5 severely reduce specific ligand binding and chemokine-induced chemotaxis. 2) An extracellular domain variant, A29S, when co-expressed with CD4, supported HIV-1 infection whereas the others do not. 3) The transmembrane region variants of CCR5 support monotropic HIV-1 infection that is blocked by addition of some receptor agonists. Mutations in the first and second transmembrane domains increase RANTES (regulated on activation normal T-cell expressed) binding affinity but did not affect MIP1beta binding affinity presumably based on differences in ligand-receptor interaction sites. Furthermore, the CCR5 transmembrane mutants do not respond to RANTES with the classical bell-shaped chemotactic response curve, suggesting that they are resistant to RANTES-induced desensitization. These data demonstrate that single amino acid changes in the extracellular domains of CCR5 can have profound effects on both HIV-1 co-receptor and specific ligand-induced functions, whereas mutations in the transmembrane domain only affect the response to chemokine ligands.
authors.affiliation: Intramural Research Support Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA. howardz@mail.ncifcrf.gov
authors.forename: O M
authors.initials: OM
authors.lastname: Howard
authors.forename: A K
authors.initials: AK
authors.lastname: Shirakawa
authors.forename: J A
authors.initials: JA
authors.lastname: Turpin
authors.forename: A
authors.initials: A
authors.lastname: Maynard
authors.forename: G J
authors.initials: GJ
authors.lastname: Tobin
authors.forename: M
authors.initials: M
authors.lastname: Carrington
authors.forename: J J
authors.initials: JJ
authors.lastname: Oppenheim
authors.forename: M
authors.initials: M
authors.lastname: Dean
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000494:pharmacology; D002460:Cell Line; D054407:Chemokine CCL4; D018946:Chemokine CCL5 / Q000378:metabolism; D005434:Flow Cytometry; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D019402:Macrophage Inflammatory Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009282:Naphthalenesulfonates / Q000494:pharmacology; D017433:Protein Structure, Secondary; D019713:Receptors, CCR5 / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D019380:Anti-HIV Agents; D054407:Chemokine CCL4; D018946:Chemokine CCL5; D008024:Ligands; D019402:Macrophage Inflammatory Proteins; C112855:NSC 651016; D009282:Naphthalenesulfonates; D019713:Receptors, CCR5