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  • Title: Extracellular HIV-1 tat protein up-regulates the expression of surface CXC-chemokine receptor 4 in resting CD4+ T cells.
    Author: Secchiero P, Zella D, Capitani S, Gallo RC, Zauli G.
    Journal: J Immunol; 1999 Feb 15; 162(4):2427-31. PubMed ID: 9973525.
    Abstract:
    Here we report that synthetic HIV-1 Tat protein, immobilized on a solid substrate, up-regulates the surface expression of the CXC-chemokine receptor 4 (CXCR4), but not of the CC-chemokine receptor 5 in purified populations of primary resting CD4+ T cells. The Tat-mediated increase of CXCR4 occurred in a well-defined range of concentrations (1-10 nM of immobilized Tat) and time period (4-8 h postincubation). Moreover, the increase of CXCR4 was accompanied by an increased entry of the HXB2 T cell line-tropic (X4-tropic), but not of the BaL macrophage-tropic strain of HIV-1. The ability of Tat to up-regulate CXCR4 expression was abrogated by the protein synthesis inhibitor cycloheximide, clearly indicating the requirement of de novo synthesis. As Tat protein is actively released by HIV-1 infected cells, our data indicate a potentially important role for extracellular Tat in rendering bystander CD4+ T cells more susceptible to infection with X4-tropic HIV-1 isolates.
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