Abstract
Hepatitis C virus core protein is a highly basic viral protein that multimerizes with itself to form the viral capsid. When expressed in CD4+ T lymphocytes, it can induce modifications in several essential cellular and biological networks. To shed light on the mechanisms underlying the alterations caused by the viral protein, we have analyzed HCV-core subcellular localization and its associations with host proteins in Jurkat T cells. In order to investigate the intracellular localization of Hepatitis C virus core protein, we have used a lentiviral system to transduce Jurkat T cells and subsequently localize the protein using immunoelectron microscopy techniques. We found that in Jurkat T cells, Hepatitis C virus core protein mostly localizes in the nucleus and specifically in the nucleolus. In addition, we performed pull-down assays combined with Mass Spectrometry Analysis, to identify proteins that associate with Hepatitis C virus core in Jurkat T cells. We found proteins such as NOLC1, PP1γ, ILF3, and C1QBP implicated in localization and/or traffic to the nucleolus. HCV-core associated proteins are implicated in RNA processing and RNA virus infection as well as in functions previously shown to be altered in Hepatitis C virus core expressing CD4+ T cells, such as cell cycle delay, decreased proliferation, and induction of a regulatory phenotype. Thus, in the current work, we show the ultrastructural localization of Hepatitis C virus core and the first profile of HCV core associated proteins in T cells, and we discuss the functions and interconnections of these proteins in molecular networks where relevant biological modifications have been described upon the expression of Hepatitis C virus core protein. Thereby, the current work constitutes a necessary step toward understanding the mechanisms underlying HCV core mediated alterations that had been described in relevant biological processes in CD4+ T cells.
Highlights
Hepatitis C virus (HCV) infection is an important cause for chronic viral liver disease and one of the main indications for liver transplantation (Anzola, 2004; Dustin and Rice, 2007)
As studies using the whole virus do not allow for the elucidation of the specific molecular mechanisms in which each protein is implicated, in this work, we focused on a single viral protein, showing that in CD4+ T cells, HCV core protein mostly localizes in the nucleus and in the nucleolus where it is greatly enriched
HCV-core-GFP was detected in the nucleus in 35% out of 40 HCV Core GFP expressing Jurkat cells analyzed, 22% showed the presence of GFP inside both nucleus and cytoplasm, 5% of the cells only in cytoplasm (Figure 1A), while 18% showed GFP immunolabelling in nucleus with enrichment in the nucleolus (Figures 1B–F). 20% of the cells were not stained
Summary
Hepatitis C virus (HCV) infection is an important cause for chronic viral liver disease and one of the main indications for liver transplantation (Anzola, 2004; Dustin and Rice, 2007). The high level of chronicity and the absence of a protective vaccine, makes HCV infection a significant public health problem (Anzola, 2004; Dustin and Rice, 2007; Gower et al, 2014). The molecular mechanisms harnessed by HCV to establish a chronic infection and their implications in the innate and adaptive immune systems have not been fully elucidated. In this regard, several HCV viral proteins have been described as modulators of immunological phenomena (Yao et al, 2007; Krishnadas et al, 2010; Tu et al, 2012; Chen et al, 2015). The underlying molecular processes, as well as the behavior of HCV core protein or its interactions with host cell components, remain unclear
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