How to engage Cofilin

In HIV-infected people, resting CD4+ T cells are the main reservoir of latent virus and the reason for the failure of drug therapy to cure HIV infection. Still, we do not have a complete understanding of the factors regulating HIV replication in these cells. A recent paper in Cell describes a new trick that the virus uses to infect resting T cells. Interaction between the viral gp120 and cellular HIV co-receptor, CXCR4, during viral entry initiates signaling that activates cofilin, the main regulator of actin polymerization. As a result of this activation, actin is depolymerized, thus destroying the natural barrier to HIV replication. I discuss implications of this study for our understanding of HIV biology and development of novel anti-HIV therapeutic approaches

Yeast help identify cytopathic factors of Zika virus

Accumulating evidence implicates Zika virus (ZIKV) in pathogenesis of microcephaly in newborns and Guillain-Barré syndrome in adults. However, it remains unclear which viral proteins are responsible for these effects and what are the underlying mechanisms of their pathogenic activity. A recent paper by Drs. Zhao and Gallo, and their colleagues at University of Maryland in Baltimore used fission yeast for genome-wide analysis of ZIKV proteins. They demonstrated cytopathogenic activity for seven ZIKV proteins, anaC, C, prM, M, E, NS2B and NS4A. This activity was shown to be dependent on oxidative stress, and for NS4A they demonstrated involvement of the TOR stress-response pathway. Taken together, the findings presented in this paper provide the basis for further mechanistic studies that potentially can identify therapeutic means to treat neuro and immune complications of ZIKV infection

The Interaction between Nef Protein and ABCA1 Mutants in Tangier Disease

The genetic disorder Tangier Disease is characterized by mutations at a chromosomal locus, 9q31, which affect proper function of the cholesterol transporter ATP-Binding Cassette A1 (ABCA1). Individuals with mutant ABCA1 have very low levels of high-density lipoprotein and are at high risk for development of neuropathy and atherosclerosis. Two of the ABCA1 mutations, Q597R and R587W, lead to retention of ABCA1 in the endoplasmic reticulum (ER) in a pattern that is reminiscent of a previously reported ABCA1 inactivation by HIV-1 protein Nef. The mechanism of that inactivation involves Nef binding to an ER chaperone calnexin, which disrupts the interaction between calnexin and ABCA1 preventing proper maturation of ABCA1. As a result, ABCA1 is retained in the ER and not transported to the plasma membrane where its main activity takes place. Thus, we speculated that the underlying mechanism of retention of ABCA1 in the ER of patients with Q597R and R587W mutations is caused by a weakened interaction between mutated ABCA1 and calnexin. However, our preliminary data suggests that it is actually an abnormally strong interaction between these two molecules that leads to the retention of ABCA1 in the ER. The main aim of my research is to attempt to use HIV-1 Nef to decrease the strength of interaction between these mutants and calnexin, which may enable the transport of ABCA1 molecules to cellular membrane, thus restoring the cholesterol efflux from the affected cells. If successful, this approach could lead to a potential therapeutic treatment for Tangier disease using Nef-mimicking peptides

Cold Atmospheric Plasma Inhibits HIV-1 Replication in Macrophages by Targeting Both the Virus and the Cells.

Cold atmospheric plasma (CAP) is a specific type of partially ionized gas that is less than 104°F at the point of application. It was recently shown that CAP can be used for decontamination and sterilization, as well as anti-cancer treatment. Here, we investigated the effects of CAP on HIV-1 replication in monocyte-derived macrophages (MDM). We demonstrate that pre-treatment of MDM with CAP reduced levels of CD4 and CCR5, inhibiting virus-cell fusion, viral reverse transcription and integration. In addition, CAP pre-treatment affected cellular factors required for post-entry events, as replication of VSV-G-pseudotyped HIV-1, which by-passes HIV receptor-mediated fusion at the plasma membrane during entry, was also inhibited. Interestingly, virus particles produced by CAP-treated cells had reduced infectivity, suggesting that the inhibitory effect of CAP extended to the second cycle of infection. These results demonstrate that anti-HIV activity of CAP involves the effects on target cells and the virus, and suggest that CAP may be considered for potential application as an anti-HIV treatment

136 HIV-1 Nef regulates activity of endoplasmic reticulum chaperone calnexin

HIV-1 Nef promotes viral replication by downmodulating a number of cell surface transmembrane proteins, such as CD4, MHC-I and MHC-II, which are targeted by Nef to various degradation pathways. Nef is also responsible for downregulation of cellular cholesterol transporter ABCA1, and this effect contributes to development of atherosclerosis in HIV infected patients. Surprisingly, in contrast to CD4 and MHC I, to which Nef has to bind to exert downregulation, binding to ABCA1 turned out to be unnecessary for inactivation of ABCA1 by Nef. Here, we identified a novel mechanism by which Nef influences activity of host cell and viral proteins. We show that Nef interacts with an endoplasmic reticulum chaperone calnexin, which is essential for folding and maturation of glycosylated proteins. Nef disrupts calnexin interaction with ABCA1, thus impairing functionality of this protein, but increases affinity and enhances interaction of calnexin with gp160, promoting maturation and functionality of viral Env proteins. Knock-down of calnexin lead to reduced fusion activity of HIV-1 envelope and reduced virion infectivity, as well as to defective cholesterol efflux, which is mediated by ABCA1. However, gp160 and ABCA1 interacted with calnexin differently: while gp160 binding to calnexin was dependent on glycosylation, interaction of ABCA1 with calnexin was glycosylation-independent. Therefore, Nef binds to calnexin and stimulates interaction between calnexin and gp160 at the expense of ABCA1 and probably other ER proteins. These results provide a mechanistic explanation for previously unexplained effect of Nef on functionality of ABCA1, and suggest a mechanism for upregulation of HIV infectivity by Nef through stimulation of Env maturation

DNA dependent protein kinase (DNA-PK) enhances HIV transcription by promoting RNA polymerase II activity and recruitment of transcription machinery at HIV LTR.

Despite reductions in mortality from the use of highly active antiretroviral therapy (HAART), the presence of latent or transcriptionally silent proviruses prevents HIV cure/eradication. We have previously reported that DNA-dependent protein kinase (DNA-PK) facilitates HIV transcription by interacting with the RNA polymerase II (RNAP II) complex recruited at HIV LTR. In this study, using different cell lines and peripheral blood mononuclear cells (PBMCs) of HIV-infected patients, we found that DNA-PK stimulates HIV transcription at several stages, including initiation, pause-release and elongation. We are reporting for the first time that DNA-PK increases phosphorylation of RNAP II C-terminal domain (CTD) at serine 5 (Ser5) and serine 2 (Ser2) by directly catalyzing phosphorylation and by augmenting the recruitment of the positive transcription elongation factor (P-TEFb) at HIV LTR. Our findings suggest that DNA-PK expedites the establishment of euchromatin structure at HIV LTR. DNA-PK inhibition/knockdown leads to the severe impairment of HIV replication and reactivation of latent HIV provirus. DNA-PK promotes the recruitment of Tripartite motif-containing 28 (TRIM28) at LTR and assists the release of paused RNAP II through TRIM28 phosphorylation. These results provide the mechanisms through which DNA-PK controls the HIV gene expression and, likely, can be extended to cellular gene expression, including during cell malignancy, where the role of DNA-PK has been well-established