title: HIV-1 activates Cdc42 and induces membrane extensions in immature dendritic cells to facilitate cell-to-cell virus propagation.
abstract: 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-1(env) 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.
authors.affiliation: Department of Dermatology and Venereology, Microbiology and Molecular Medicine, University Hospitals and Medical School of Geneva, Geneva, Switzerland. benedicte.neven@nck.aphp.fr
authors.forename: Damjan S
authors.initials: DS
authors.lastname: Nikolic
authors.forename: Martin
authors.initials: M
authors.lastname: Lehmann
authors.forename: Richard
authors.initials: R
authors.lastname: Felts
authors.forename: Eduardo
authors.initials: E
authors.lastname: Garcia
authors.forename: Fabien P
authors.initials: FP
authors.lastname: Blanchet
authors.forename: Sriram
authors.initials: S
authors.lastname: Subramaniam
authors.forename: Vincent
authors.initials: V
authors.lastname: Piguet
mesh_terms: D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation; D022081:Cell Surface Extensions / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D004789:Enzyme Activation; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism / Q000821:virology; D015497:HIV-1 / Q000254:growth & development* / Q000472:pathogenicity / Q000502:physiology*; D006367:HeLa Cells; D054884:Host-Pathogen Interactions / Q000502:physiology; D006801:Humans; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D015854:Up-Regulation / Q000502:physiology; D053586:Virus Internalization; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D020764:cdc42 GTP-Binding Protein