Abstract
Norovirus is an acute infection of the gastrointestinal tract causing rapid induction of vomiting and diarrhoea. The infection is sensed and controlled by the innate immune system, particularly by the RNA helicase MDA-5 and type I and III interferons (IFNs). We have observed that intracellular replication of murine norovirus (MNV) occurs in membranous clusters proximal to the microtubule organising centre, a localisation dependent on intact microtubules. Recently, it was shown that the host protein guanine nucleotide exchange factor-H1 (GEF-H1) is a microtubule-associated innate immune sensor that activates interferon Regulatory Factor 3 to induce the production of type I IFNs. Thus, we interrogated the potential role of GEF-H1 in controlling MNV infections. We observed that GEF-H1 was recruited to the MNV replication complex; however RNAi-mediated suppression of GEF-H1 did not outwardly affect replication. We furthered our studies to investigate the impact of GEF-H1 on MNV innate detection and observed that GEF-H1 did not contribute to type I IFN induction during MNV infection or influenza virus infection but did result in a small reduction of interferon–β (IFNβ) during West Nile virus infection. Intriguingly, we discovered an interaction of GEF-H1 with the viral MNV non-structural protein 3 (NS3), an interaction that altered the location of GEF-H1 within the cell and prevented the formation of GEF-H1-induced microtubule fibres. Thus, our results indicate that GEF-H1 does not contribute significantly to the innate immune sensing of MNV, although its function may be modulated via interaction with the viral NS3 protein.
Highlights
Norovirus (NoV) infects approximately 700 million people each year resulting in an estimated220,000 deaths in developing countries [1,2,3] and an economic burden of USD $60 billion due to healthcare costs and productivity loss [4,5]
We previously investigated the interaction of murine norovirus (MNV) with the cytoskeleton of the host cell and observed that tubulin, a major component of microtubules, co-localises with the MNV replication complex (RC) and the MNV non-structural protein 3 (NS3) [15,16]
guanine nucleotide exchange factor-H1 (GEF-H1) Is Found within the MNV Replication Complex
Summary
Norovirus (NoV) infects approximately 700 million people each year resulting in an estimated220,000 deaths in developing countries [1,2,3] and an economic burden of USD $60 billion due to healthcare costs and productivity loss [4,5]. Norovirus (NoV) infects approximately 700 million people each year resulting in an estimated. NoVs are positive sense single-stranded RNA (ssRNA). Little is known about human NoV replication and pathogenesis due to the difficulty of cultivating the virus in the laboratory. It was recently observed that human B cells exposed to enteric bacteria or enteroid cultures were permissive and susceptible to human NoV infection [9,10]. Until this point the only norovirus to be studied in culture was the recently discovered genogroup V murine norovirus (MNV) [11,12].
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