HIV-1 activates Cdc42 and induces membrane extensions in immature dendritic cells to facilitate cell-to-cell virus propagation

• Published in: Blood 2011-11, Vol.118 (18), p.4841-4852
• Main Authors: Nikolic, Damjan S., Lehmann, Martin, Felts, Richard, Garcia, Eduardo, Blanchet, Fabien P., Subramaniam, Sriram, Piguet, Vincent
• Format: Article
• Language: English
• Subjects: Adaptive immunology; cdc42 GTP-Binding Protein - metabolism; Cell Communication - physiology; Cell Differentiation; Cell Surface Extensions - metabolism; Cell Surface Extensions - physiology; Cells, Cultured; Cellular Biology; Dendritic Cells - metabolism; Dendritic Cells - physiology; Dendritic Cells - ultrastructure; Enzyme Activation; HeLa Cells; HIV Infections - immunology; HIV Infections - metabolism; HIV Infections - virology; HIV-1 - growth & development; HIV-1 - pathogenicity; HIV-1 - physiology; Host-Pathogen Interactions - physiology; Humans; Immunobiology; Immunology; Innate immunity; Life Sciences; Microbiology and Parasitology; Stem Cells - metabolism; Stem Cells - physiology; Stem Cells - ultrastructure; Up-Regulation - physiology; Virology; Virus Internalization
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2010-09-305417

HIV-1 cell-to-cell transmission confers a strong advantage as it increases efficiency of transfer up to 100-fold compared with a cell-free route. Mechanisms of HIV-1 cell-to-cell transmission are still unclear and can in part be explained by the presence of actin-containing cellular protrusions. Such protrusions have been shown to facilitate cell-to-cell viral dissemination. Using fluorescence microscopy, electron tomography, and ion abrasion scanning electron microscopy we show that HIV-1 induces membrane extensions in immature dendritic cells through activation of Cdc42. We demonstrate that these extensions are induced after engagement of DC-SIGN by HIV-1env via a cascade that involves Src kinases, Cdc42, Pak1, and Wasp. Silencing of Cdc42 or treatment with a specific Cdc42 inhibitor, Secramine A, dramatically reduced the number of membrane protrusions visualized on the cell surface and decreased HIV-1 transfer via infectious synapses. Ion abrasion scanning electron microscopy of cell-cell contact regions showed that cellular extensions from immature dendritic cells that have the appearance of thin filopodia in thin section images are indeed extended membranous sheets with a narrow cross section. Our results demonstrate that HIV-1 binding on immature dendritic cells enhances the formation of membrane extensions that facilitate HIV-1 transfer to CD4+ T lymphocytes.