Explore the vast range of titles available.

The pro-fibrogenic cytokine connective tissue growth factor (CTGF) plays an important role in the development and progression of fibrosis in many organ systems, including liver. However, its role in the pathogenesis of hepatitis C virus (HCV)-induced liver fibrosis remains unclear. In the present study, we assessed CTGF expression in HCV-infected hepatocytes using replicon cells containing full-length HCV genotype 1 and the infectious HCV clone JFH1 (HCV genotype 2) by real-time PCR, Western blot analysis and confocal microscopy. We evaluated transforming growth factor β1 (TGF-β1) as a key upstream mediator of CTGF production using neutralizing antibodies and shRNAs. We also determined the signaling molecules involved in CTGF production using various immunological techniques. We demonstrated an enhanced expression of CTGF in two independent models of HCV infection. We also demonstrated that HCV induced CTGF expression in a TGF-β1-dependent manner. Further dissection of the molecular mechanisms revealed that CTGF production was mediated through sequential activation of MAPkinase and Smad-dependent pathways. Finally, to determine whether CTGF regulates fibrosis, we showed that shRNA-mediated knock-down of CTGF resulted in reduced expression of fibrotic markers in HCV replicon cells. Our studies demonstrate a central role for CTGF expression in HCV-induced liver fibrosis and highlight the potential value of developing CTGF-based anti-fibrotic therapies to counter HCV-induced liver damage.

Heat shock protein 90 (Hsp90) is a highly conserved molecular chaperone involved in ATP-dependent client protein remodeling and activation. It also functions as a protein holdase, binding and stabilizing clients in an ATP-independent process. Hsp90 remodels over 300 client proteins and is essential for cell survival in eukaryotes. In bacteria, Hsp90 is a highly abundant protein, although very few clients have been identified and it is not essential for growth in many bacterial species. We previously demonstrated that in Escherichia coli, Hsp90 causes cell filamentation when expressed at high levels. Here, we have explored the cause of filamentation and identified a potentially important client of E. coli Hsp90 (Hsp90Ec), FtsZ. We observed that FtsZ, a bacterial tubulin homolog essential for cell division, fails to assemble into FtsZ rings (divisomes) in cells overexpressing Hsp90Ec. Additionally, Hsp90Ec interacts with FtsZ and inhibits polymerization of FtsZ in vitro, in an ATP-independent holding reaction. The FtsZ–Hsp90Ec interaction involves residues in the client-binding region of Hsp90Ec and in the C-terminal tail of FtsZ, where many cell-division proteins and regulators interact. We observed that E. coli deleted for the Hsp90Ec gene htpG turn over FtsZ more rapidly than wild-type cells. Additionally, the length of ΔhtpG cells is reduced compared to wild-type cells. Altogether, these results suggest that Hsp90Ec is a modulator of cell division, and imply that the polypeptide-holding function of Hsp90 may be a biologically important chaperone activity.

We have previously shown that hepatocytes exposed to hepatitis C virus (HCV) and human immunodeficiency virus (HIV) envelope proteins undergo apoptosis. In this article, we further elucidate the signaling mechanisms that mediate this effect. We found that, in human hepatocellular carcinoma (HepG2) cells, HCV E2 protein and HIV glycoprotein (gp) 120 significantly up-regulated the Fas ligand (FasL) and enhanced the formation of the Fas death—inducing signaling complex downstream of Fas receptor activation. Moreover, after stimulation with HCV E2 and HIV gp120, enhanced expression of caspases 2 and 7 and increased caspase 3 activity were observed. In addition, we showed up-regulation of the proapoptotic molecule Bid and its association with caspase 8 after treatment with these envelope proteins. We also found that HCV E2 and HIV gp120 induced a partial translocation of Bid to the mitochondria, which resulted in the release of cytochrome C and the apoptosis-inducing factor. Thus, the results of this study suggest that FasL and Bid play an important role in HCV and HIV envelope protein—induced apoptosis.

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure–activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase–activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigmhave the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

[This corrects the article DOI: 10.1371/journal.pone.0046526.].[This corrects the article DOI: 10.1371/journal.pone.0046526.].

- Numerous studies highlight interlaboratory performance variability in diagnostic immunohistochemistry (IHC) testing. Despite substantial improvements over the years, the inability to quantitatively and objectively assess immunostain sensitivity complicates interlaboratory standardization. - To quantitatively and objectively assess the sensitivity of the immunohistochemical stains for human epidermal growth factor receptor type 2 (HER2), estrogen receptor (ER), and progesterone receptor (PR) across IHC laboratories in a proficiency testing format. We measure sensitivity with parameters that are new to the field of diagnostic IHC: analytic response curves and limits of detection. - Thirty-nine diagnostic IHC laboratories stained a set of 3 slides, one each for HER2, ER, and PR. Each slide incorporated a positive tissue section and IHControls at 5 different concentrations. The IHControls comprise cell-sized clear microbeads coated with defined concentrations of analyte (HER2, ER, and/or PR). The laboratories identified the limits of detection and then mailed the slides for quantitative assessment. - Each commercial immunostain demonstrated a characteristic analytic response curve, reflecting strong reproducibility among IHC laboratories using the same automation and reagents prepared per current Good Manufacturing Practices. However, when comparing different commercial vendors (using different reagents), the data reveal up to 100-fold differences in analytic sensitivity. For proficiency testing purposes, quantitative assessment using analytic response curves was superior to subjective interpretation of limits of detection. - Assessment of IHC laboratory performance by quantitative measurement of analytic response curves is a powerful, objective tool for identifying outlier IHC laboratories. It uniquely evaluates immunostain performance across a range of defined analyte concentrations.

Patients coinfected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) have progressive liver disease that frequently leads to cirrhosis and death. We previously showed that hepatocytes exposed to HCV and HIV envelope proteins undergo apoptosis via an innocent-bystander mechanism as a result of the cell surface binding of these proteins, independent of direct viral infection. Here, we have defined the mechanism of this hepatocytic apoptosis. We observed enhanced signal transducer and activator of transcription factor 1 (STAT1) activation and phosphorylation after costimulation with HCV-E2 and HIV-gp120. Moreover, inhibitor studies indicated that Lyn kinase, p38 mitogen-activated protein kinase, and protein kinase Cδ might be involved in STAT1 phosphorylation. To elucidate the downstream STAT1-mediated signaling, we overexpressed wild-type STAT1α and the C-terminal domain–deleted mutant STAT1β. STAT1α overexpression increased cell apoptosis and Fas ligand expression, compared with STAT1β overexpression. STAT1α also enhanced the release of cytochrome c from the mitochondria and caspase-3 activity. These studies indicate that the HCV/HIV envelope proteins cooperatively induce hepatocytic apoptosis by activating a novel downstream STAT1 signaling pathway