title: Single-molecule analysis of human immunodeficiency virus type 1 gp120-receptor interactions in living cells.
abstract: A quantitative description of the binding interactions between human immunodeficiency virus (HIV) type 1 envelope glycoproteins and their host cell surface receptors remains incomplete. Here, we introduce a single-molecule analysis that directly probes the binding interactions between an individual viral subunit gp120 and a single receptor CD4 and/or chemokine coreceptor CCR5 in living cells. This analysis differentiates single-molecule binding from multimolecule avidity and shows that, while the presence of CD4 is required for gp120 binding to CCR5, the force required to rupture a single gp120-coreceptor bond is significantly higher and its lifetime is much longer than those of a single gp120-receptor bond. The lifetimes of these bonds are themselves shorter than those of the P-selectin/PSGL-1 bond involved in leukocyte attachment to the endothelium bonds during an inflammation response. These results suggest an amended model of HIV entry in which, immediately after the association of gp120 to its receptor, gp120 seeks its coreceptor to rapidly form a new bond. This "bond transfer" occurs only if CCR5 is in close proximity to CD4 and CD4 is still attached to gp120. The analysis presented here may serve as a general framework to study mechanisms of receptor-mediated interactions between viral envelope proteins and host cell receptors at the single-molecule level in living cells.
authors.affiliation: Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
authors.forename: Melissa I
authors.initials: MI
authors.lastname: Chang
authors.forename: Porntula
authors.initials: P
authors.lastname: Panorchan
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Dobrowsky
authors.forename: Yiider
authors.initials: Y
authors.lastname: Tseng
authors.forename: Denis
authors.initials: D
authors.lastname: Wirtz
mesh_terms: D015704:CD4 Antigens / Q000378:metabolism*; D002460:Cell Line; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D019713:Receptors, CCR5; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism*; D015728:Receptors, HIV / Q000235:genetics / Q000378:metabolism*
chemical_list: D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5; D018121:Receptors, Cytokine; D015728:Receptors, HIV