How human immunodeficiency virus type 1 uses alternative receptors and coreceptors to enter cells [electronic resource].

Berson, Joanne Fraher.
197 p.
Molecular biology.
Local subjects:
Penn dissertations -- Cell biology. (search)
Cell biology -- Penn dissertations. (search)
Penn dissertations -- Molecular biology. (search)
Molecular biology -- Penn dissertations. (search)
System Details:
Mode of access: World Wide Web.
The human immunodeficiency virus type 1 (HIV-1) utilizes multiple cell surface molecules to mediate entry into host cells. Binding of the envelope glycoprotein (Env) of HIV-1 to these cellular receptors induces conformational changes in Env required for fusion of the viral and cellular membranes. CD4 is the primary HIV-1 receptor, however, HIV-1 infects some cell types which lack CD4, demonstrating that one or more alternative receptors exist. In addition, CD4 is not sufficient to mediate entry into non-human cells, indicating that one or more human accessory factors are required for virus infection. The glycosphingolipid galactosylceramide (GalCer) has been identified as an alternative HIV-1 receptor. To study the interaction of Env and GalCer in the context of a lipid bilayer, we developed a liposome flotation assay. Binding of Env to liposomes was critically dependent upon the concentration of GalCer, suggesting that binding occurs to glycolipid rich domains and that GalCer conformation may be important for Env recognition. The GalCer binding site was highly conserved, but the ability to bind GalCer did not necessarily confer infection of a GalCer-positive, CD4-negative cell line. To confirm the finding that the chemokine receptor CXCR4 serves as an HIV-1 coreceptor, we demonstrated that expression of CXCR4 in non-human cell lines, in conjunction with CD4, rendered these cells fully permissive for T cell-tropic Env-mediated cell-cell fusion and infection. Macrophage-tropic Env proteins did not fuse with cells expressing CXCR4 and CD4, suggesting that macrophage-tropic viruses utilize a coreceptor other than CXCR4. Using CXCR4/CXCR2 receptor chimeras, we found that the second extracellular loop of CXCR4 was a critical determinant of coreceptor function. Our results lead to a model as to how changes in Env enable the virus to switch coreceptor utilization. Finally, a single amino acid change in the second extracellular loop of CXCR4 conferred the ability of macrophage-tropic viruses to utilize CXCR4, emphasizing that only minimal structural changes must occur to lead to a productive interaction between macrophage-tropic Env proteins and CXCR4.
Thesis (Ph.D. in Cell and Molecular Biology) -- University of Pennsylvania, 1997.
Source: Dissertation Abstracts International, Volume: 58-11, Section: B, page: 5784.
Adviser: Robert W. Doms.
Local notes:
School code: 0175.
Doms, Robert W., advisor
University of Pennsylvania.
Contained In:
Dissertation Abstracts International 58-11B.
Access Restriction:
Restricted for use by site license.
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