title: Role of Abl kinase and the Wave2 signaling complex in HIV-1 entry at a post-hemifusion step.
abstract: Entry of human immunodeficiency virus type 1 (HIV-1) commences with binding of the envelope glycoprotein (Env) to the receptor CD4, and one of two coreceptors, CXCR4 or CCR5. Env-mediated signaling through coreceptor results in Galphaq-mediated Rac activation and actin cytoskeleton rearrangements necessary for fusion. Guanine nucleotide exchange factors (GEFs) activate Rac and regulate its downstream protein effectors. In this study we show that Env-induced Rac activation is mediated by the Rac GEF Tiam-1, which associates with the adaptor protein IRSp53 to link Rac to the Wave2 complex. Rac and the tyrosine kinase Abl then activate the Wave2 complex and promote Arp2/3-dependent actin polymerization. Env-mediated cell-cell fusion, virus-cell fusion and HIV-1 infection are dependent on Tiam-1, Abl, IRSp53, Wave2, and Arp3 as shown by attenuation of fusion and infection in cells expressing siRNA targeted to these signaling components. HIV-1 Env-dependent cell-cell fusion, virus-cell fusion and infection were also inhibited by Abl kinase inhibitors, imatinib, nilotinib, and dasatinib. Treatment of cells with Abl kinase inhibitors did not affect cell viability or surface expression of CD4 and CCR5. Similar results with inhibitors and siRNAs were obtained when Env-dependent cell-cell fusion, virus-cell fusion or infection was measured, and when cell lines or primary cells were the target. Using membrane curving agents and fluorescence microscopy, we showed that inhibition of Abl kinase activity arrests fusion at the hemifusion (lipid mixing) step, suggesting a role for Abl-mediated actin remodeling in pore formation and expansion. These results suggest a potential utility of Abl kinase inhibitors to treat HIV-1 infected patients.
authors.affiliation: Division of Molecular Oncology, Washington University School of Medicine, St Louis, Missouri, United States of America.
authors.forename: Brooke
authors.initials: B
authors.lastname: Harmon
authors.forename: Nancy
authors.initials: N
authors.lastname: Campbell
authors.forename: Lee
authors.initials: L
authors.lastname: Ratner
mesh_terms: D000199:Actins / Q000378:metabolism; D001254:Astrocytoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D015704:CD4 Antigens / Q000378:metabolism; D002459:Cell Fusion; D002478:Cells, Cultured; D003599:Cytoskeleton; D005434:Flow Cytometry; D015752:Genes, env; D015658:HIV Infections / Q000378:metabolism* / Q000821:virology*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016315:Proto-Oncogene Proteins c-abl / Q000235:genetics / Q000378:metabolism*; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes; D014771:Virion / Q000378:metabolism*; D053586:Virus Internalization; D014779:Virus Replication; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D015704:CD4 Antigens; D047428:Protein Kinase Inhibitors; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; C120152:WASF2 protein, human; D051300:Wiskott-Aldrich Syndrome Protein Family; D016315:Proto-Oncogene Proteins c-abl