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  • Extracellular ATP induces t...
    Graziano, Francesca; Marion Desdouits; Livia Garzetti; Paola Podini; Massimo Alfano; Anna Rubartelli; Roberto Furlan; Philippe Benaroch; Guido Poli

    Proceedings of the National Academy of Sciences, 06/2015, Letnik: 112, Številka: 25
    Journal Article

    Significance A major obstacle to the eradication of HIV-1 by combination antiretroviral therapy (cART) is the formation of cellular reservoirs in CD4 ⁺ T lymphocytes (carrying latently integrated provirus) and tissue macrophages. Infected macrophages assemble new virions in subcellular vacuoles known as virus-containing compartments (VCC), hiding them from the immune system and, in part, from antiretroviral agents. Here we report that extracellular ATP is capable of inducing the rapid release of virions accumulated in VCC via interaction with the P2X7 receptor and without inducing cell death, whereas the antidepressant agent Imipramine blocks the release. Thus, our study identifies two “druggable” targets affecting the release of stored virions from infected human macrophages that could bear relevance for purging HIV-1 reservoirs in individuals receiving cART. HIV type 1 (HIV-1) infects CD4 ⁺ T lymphocytes and tissue macrophages. Infected macrophages differ from T cells in terms of decreased to absent cytopathicity and for active accumulation of new progeny HIV-1 virions in virus-containing compartments (VCC). For these reasons, infected macrophages are believed to act as “Trojan horses” carrying infectious particles to be released on cell necrosis or functional stimulation. Here we explored the hypothesis that extracellular ATP (eATP) could represent a microenvironmental signal potentially affecting virion release from VCC of infected macrophages. Indeed, eATP triggered the rapid release of infectious HIV-1 from primary human monocyte-derived macrophages (MDM) acutely infected with the CCR5-dependent HIV-1 strain. A similar phenomenon was observed in chronically infected promonocytic U1 cells differentiated to macrophage-like cells (D-U1) by costimulation with phorbol esters and urokinase-type plasminogen activator. Worthy of note, eATP did not cause necrotic, apoptotic, or pyroptotic cell death, and its effect on HIV-1 release was suppressed by Imipramine (an antidepressant agent known to inhibit microvesicle formation by interfering with membrane-associated acid sphingomyelinase). Virion release was not triggered by oxidized ATP, whereas the effect of eATP was inhibited by a specific inhibitor of the P2X7 receptor (P2X7R). Thus, eATP triggered the discharge of virions actively accumulating in VCC of infected macrophages via interaction with the P2X7R in the absence of significant cytopathicity. These findings suggest that the microvesicle pathway and P2X7R could represent exploitable targets for interfering with the VCC-associated reservoir of infectious HIV-1 virions in tissue macrophages.