Proteomic profiling of SupT1 cells reveal modulation of host proteins by HIV-1 Nef variants

HIV-1 Nef hijacks both exocytic and endocytic pathways of host intracellular trafficking through differential regulation of Rab GTPases

HIV-1 Nef regulates several cellular functions in an infected cell which results in viral persistence and AIDS pathogenesis. The currently understood molecular mechanism(s) underlying Nef-dependent cellular function(s) are unable to explain how events are coordinately regulated in the host cell. Intracellular membranous trafficking maintains cellular homeostasis and is regulated by Rab GTPases - a member of the Ras superfamily. In the current study, we tried to decipher the role of Nef on the Rab GTPases-dependent complex and vesicular trafficking. Expression profiling of Rabs in Nef-expressing cells showed that Nef differentially regulates the expression of individual Rabs in a cell-specific manner. Further analysis of Rabs in HIV-1_NL4-3 or ΔNef infected cells demonstrated that the Nef protein is responsible for variation in Rabs expression. Using a panel of competitive peptide inhibitors against Nef, we identified the critical domain of HIV-1 Nef involved in modulation of Rabs expression. The molecular function of Nef-mediated upregulation of Rab5 and Rab7 and downregulation of Rab11 increased the transport of SERINC5 from the cell surface to the lysosomal compartment. Moreover, the Nef-dependent increase in Rab27 expression assists exosome release. Reversal of Rabs expression using competitive inhibitors against Nef and manipulation of Rabs expression reduced viral release and infectivity of progeny virions. Overall, this study demonstrates that Nef differentially regulates the expression of Rab proteins in HIV-1 infected cells to hijack the host intracellular trafficking, which augments viral replication and HIV-1 pathogenesis. This article is protected by copyright. All rights reserved.

Effect of the Rho GTPase inhibitor-1 on the entry of dengue serotype 2 virus into EAhy926 cells

Dengue virus (DV) is the most rapidly spreading arbovirus in the world. Our previous studies indicated that Rac1, a kind of Rho GTPase, was related with the increased vascular permeability in DV infection. However, the molecular mechanisms that regulate the activity of the Rac1 pathway during DV infection is not fully understood yet. Recently, Rho-specific guanine nucleotide dissociated inhibitors (Rho GDIs), as a pivotal upstream regulator of Rho GTPase, attract our attention. To identify the role of GDI-1 in DV2 infection, the expression of GDI in Eahy926 cells was detected. Moreover, a GDI-1 down-regulated cell line was constructed to explore the correlation between GDI-1 and Rac1 and to further evaluate the function of GDI in DV life cycle. Our results indicated that DV2 infection could up-regulate GDI-1 expression, and down-regulation of GDI enhanced the activity of Rac1. In addition, down-regulated GDI-1 significantly inhibited all steps of DV2 replication cycle. GDI-1 plays an important role in DV2 infection via negatively regulating the activation of the Rac1-actin pathway. These results not only contribute to our further understanding of the pathogenesis of severe dengue but also provide further insight into the development of antiviral drugs.

HIV-1 Nef and host proteome analysis: Current perspective

Proteome represents the set of proteins being produced by an organism at a given time. Comparative proteomic profiling of a healthy and diseased state is likely to reflect the dynamics of a disease process. Proteomic techniques are widely used to discover novel biomarkers and decipher mechanisms of HIV-1 pathogenesis. Proteomics is thus emerging as an indispensable tool of monitoring a disease process and intense interactions between HIV-1 and host. Nef is known to regulate various functions in the host to establish the state of infection. This review gives an overview of all proteomic studies done on HIV infection and HIV associated disorders including recent developments in Nef-host proteomic profiling. Here, we propose an emphasis on Nef based proteomic studies. We also discuss the future prospects and the technical and biological challenges involved in proteomic studies. Future studies with Nef related proteomic investigation are likely to identify more targets for diagnosis and therapy.

Alpha-enolase regulates hepatitis B virus replication through suppression of the interferon signalling pathway

Persistent chronic infection with hepatitis B virus (HBV) is a major risk factor for the development of HBV-related diseases. The molecular mechanisms that underlie HBV infection and associated carcinogenesis are not fully understood. The aim of this study was to explore the role of ENO1 in HBV replication processes. Here, we examined ENO1 expression levels in HBV-infected and non-HBV-infected liver tissues and cells by Western blot analysis, real-time PCR and immunohistochemistry. In addition, HBsAg and HBeAg in the media of transfected HepG2.2.15 cells were detected using an electrochemical luminescence analyser within 48 hours after ENO1-specific siRNA transfection. The expression levels of HBV DNA, type I interferon and 5 downstream IFN-stimulated genes in HepG2.2.15 cells were examined using real-time PCR. We found ENO1 expression was upregulated in the HBV-infected liver tissues and cells. Silencing of ENO1 resulted in a significant reduction in HBV replication, and this siRNA-mediated reaction also caused the upregulation of expression of type I interferon and downstream IFN-stimulated genes. Therefore, we come to the conclusion ENO1 is involved in HBV replication. It is therefore likely that HBV replication is enhanced following suppression of the IFN signalling pathway. However, the mechanisms that underpin ENO1-mediated modulation of the IFN signalling pathway remain to be elucidated.

Recent 5-year Findings and Technological Advances in the Proteomic Study of HIV-associated Disorders

Human immunodeficiency virus-1 (HIV-1) mainly relies on host factors to complete its life cycle. Hence, it is very important to identify HIV-regulated host proteins. Proteomics is an excellent technique for this purpose because of its high throughput and sensitivity. In this review, we summarized current technological advances in proteomics, including general isobaric tags for relative and absolute quantitation (iTRAQ) and stable isotope labeling by amino acids in cell culture (SILAC), as well as subcellular proteomics and investigation of posttranslational modifications. Furthermore, we reviewed the applications of proteomics in the discovery of HIV-related diseases and HIV infection mechanisms. Proteins identified by proteomic studies might offer new avenues for the diagnosis and treatment of HIV infection and the related diseases.

Chemical Methods for Probing Virus-Host Proteomic Interactions

Interactions between host and pathogen proteins constitute an important aspect of both infectivity and the host immune response. Different viruses have evolved complex mechanisms to hijack host-cell machinery and metabolic pathways to redirect resources and energy flow toward viral propagation. These interactions are often critical to the virus, and thus understanding these interactions at a molecular level gives rise to opportunities to develop novel antiviral strategies for therapeutic intervention. This review summarizes current advances in chemoproteomic methods for studying these molecular altercations between different viruses and their hosts.

Proteomics in India: the clinical aspect

Proteomics has emerged as a highly promising bioanalytical technique in various aspects of applied biological research. In Indian academia, proteomics research has grown remarkably over the last decade. It is being extensively used for both basic as well as translation research in the areas of infectious and immune disorders, reproductive disorders, cardiovascular diseases, diabetes, eye disorders, human cancers and hematological disorders. Recently, some seminal works on clinical proteomics have been reported from several laboratories across India. This review aims to shed light on the increasing use of proteomics in India in a variety of biological conditions. It also highlights that India has the expertise and infrastructure needed for pursuing proteomics research in the country and to participate in global initiatives. Research in clinical proteomics is gradually picking up pace in India and its future seems very bright.