HIV-1 Envelope-Induced Signaling Mediates Actin Cytoskeleton Rearrangements Necessary for Fusion and Entry

Human immunodeficiency virus type-1: HIV-1) initiates infection by direct fusion of the virus membrane with the plasma membrane of the target cell. This fusion event is a multi-step process mediated by the envelope: Env) surface subunit gp120 and the transmembrane subunit gp41 which anchors gp120 into the viral membrane. First the surface subunit gp120 binds to the primary receptor CD4. This interaction promotes actin cytoskeletal rearrangements in the target membrane that bring the chemokine coreceptor, CCR5 or CXCR4, into close proximity for binding and induces conformational changes in gp120 that allow it to couple to the coreceptor. Formation of the gp120-CD4-coreceptor complex triggers conformational changes in the transmembrane gp41 subunit that allows gp41 to insert into the target cell membrane, allowing lipid mixing or hemifusion, and pore formation. Previous studies from our lab have shown that reorganization of the actin cytoskeletal network is required for multiple steps in HIV-1 fusion. Additional data from our lab show that HIV-1 Env induced activation of Rac is critical for HIV-1-mediated membrane fusion. HIV-1 Env activates multiple signaling pathways that could potentially lead to Rac activation. In an effort to determine which signaling molecules were required both upstream and downstream of Rac activation, we utilized small interfering RNAs: siRNAs) and various small-molecule inhibitors to disrupt signaling pathways activated by HIV-1 Env through CD4 and coreceptors. Published data from our lab demonstrated that the G-alpha-q pathway, activated by CCR5, is required for Env-mediated Rac activation and fusion. Further studies have shown that the downstream effectors of Rac that promote fusion are components of the Wave2 signaling complex and at least some of these signaling components are required at a post-hemifusion step. Other studies from our lab and other labs, with mutant CD4 constructs, have shown that signaling through CD4 is also playing a role in membrane fusion, most likely at the step of forming the gp120-CD4-coreceptor complex. These results suggest a model in which gp120 signaling though CD4 promotes gp120 binding to and signaling through the coreceptor, which is necessary for full fusion and release of the viral nucleocapsid into the cell\u27s cytosol

Augustana Seniors Fall 1884: James Moody

James Moody was a senior at Augustana College, Rock Island, Illinois, in the fall of 1884. His name appears in the college catalog of 1884 – 1885, along with his birthplace, the year of his birth, and a few other facts. From this start, we researched the genealogy and family history of James Moody. This paper contains a short biography of Moody, a report on his ancestors, a report on his descendants, and some open questions for further research

Therapeutic Efficacy of a Potent Anti-venezuelan Equine Encephalitis Virus Antibody Is Contingent on FC Effector Function

The development of specific, safe, and potent monoclonal antibodies (Abs) has led to novel therapeutic options for infectious disease. In addition to preventing viral infection through neutralization, Abs can clear infected cells and induce immunomodulatory functions through engagement of their crystallizable fragment (Fc) with complement proteins and Fc receptors on immune cells. Little is known about the role of Fc effector functions of neutralizing Abs in the context of encephalitic alphavirus infection. To determine the role of Fc effector function in therapeutic efficacy against Venezuelan equine encephalitis virus (VEEV), we compared the potently neutralizing anti-VEEV human IgG F5 (hF5) Ab with intact Fc function (hF5-WT) or containing the loss of function Fc mutations L234A and L235A (hF5-LALA) in the context of VEEV infection. We observed significantly reduced binding to complement and Fc receptors, as well as differential in vitro kinetics of Fc-mediated cytotoxicity for hF5-LALA compared to hF5-WT. The in vivo efficacy of hF5-LALA was comparable to hF5-WT at −24 and + 24 h post infection, with both Abs providing high levels of protection. However, when hF5-WT and hF5-LALA were administered + 48 h post infection, there was a significant decrease in the therapeutic efficacy of hF5-LALA. Together these results demonstrate that optimal therapeutic Ab treatment of VEEV, and possibly other encephalitic alphaviruses, requires neutralization paired with engagement of immune effectors via the Fc region

Role of Abl Kinase and the Wave2 Signaling Complex in HIV-1 Entry at a Post-Hemifusion Step

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 Gαq-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

Dispersion Modeling of Nitrogen Dioxide (NO2) and Fine Particulate Matter (PM2.5) from Backup Generators at Data Centers in Prineville, Oregon

As our society becomes increasingly dependent on digital communication (e.g., social media and email) and computerized storage (e.g., digitized medical records and government documents), tech giants such as Google, Facebook, and Apple are constructing and managing an increasing number of massive Internet data centers. These data centers house a network’s most critical systems and are vital to the continuity of daily operations. Requiring as much electricity as a medium size city, data centers rely on complex auxiliary power systems to prevent disruption to service. These backup systems consist of tens of multi-megawatt diesel-powered generators that release combustion byproducts, including over populated areas, and may lead to violations of the National Ambient Air Quality Standards (NAAQS). In this study, AERMOD (American Meteorological Society/ Environmental Protection Agency Regulatory Model) was used to model the dispersion of the criteria pollutants nitrogen dioxide (NO2) and fine particulate matter (PM2.5), from backup generators at the Facebook and Apple data centers in Prineville, Oregon. Two scenarios were considered: 1) routine readiness testing, and 2) a major power outage. Modeled spatial and temporal (seasonal) distribution of the pollutants are discussed, as well as the potential health effects on communities in the proximity of these data centers. Future research will include incorporating health and economic impacts, and consideration of adjusted emissions limits using plant site emission limits (PSEL)

Induction of the Gαq Signaling Cascade by the Human Immunodeficiency Virus Envelope Is Required for Virus Entry▿

Binding of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) with the primary receptor CD4 and one of two coreceptors, CXCR4 or CCR5, activates a signaling cascade resulting in Rac-1 GTPase activation and stimulation of actin cytoskeletal reorganizations critical for HIV-1-mediated membrane fusion. The mechanism by which HIV-1 Env induces Rac-1 activation and subsequent actin cytoskeleton rearrangement is unknown. In this study, we show that Env-mediated Rac-1 activation is dependent on the activation of Gαq and its downstream targets. Fusion and Rac-1 activation are mediated by Gαq and phospholipase C (PLC), as shown by attenuation of fusion and Rac-1 activation in cells either expressing small interfering RNA (siRNA) targeting Gαq or treated with the PLC inhibitor U73122. Rac-1 activation and fusion were also blocked by multiple protein kinase C inhibitors, by inhibitors of intracellular Ca2+ release, by Pyk2-targeted siRNA, and by the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS). Fusion was blocked without altering cell viability or cell surface localization of CD4 and CCR5. Similar results were obtained when cell fusion was induced by Env expressed on viral and cellular membranes and when cell lines or primary cells were the target. Treatment with inhibitors and siRNA specific for Gαi or Gαs signaling mediators had no effect on Env-mediated Rac-1 activation or cell fusion, indicating that the Gαq pathway alone is responsible. These results could provide a new focus for therapeutic intervention with drugs targeting host signaling mediators rather than viral molecules, a strategy which is less likely to result in resistance