The Microtubule-Associated Innate Immune Sensor GEF-H1 Does Not Influence Mouse Norovirus Replication in Murine Macrophages

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.

Regulation and functions of the RhoA regulatory guanine nucleotide exchange factor GEF-H1

“…Intriguingly, GEF-H1 has been identified in various screens as a binding partner, but reverse assays have not been reported that aimed to identify a full range of proteins that might be associating with and/or regulating GEF-H1. Although GEF-H1 knockout mice have been generated by different laboratories and, outside of a role for GEF-H1 in immune cells [ 56 , 105 , 138 ], the role of GEF-H1 in mouse cancer models has not been characterized. Given that GEF-H1 is up-regulated in various cancers, such as hepatocellular carcinoma and endometrial cancer, GEF-H1 may serve as a novel target to develop better cancer treatments, for example by disrupting the GEF-H1 interaction with RhoA.…”

Guanylate-binding protein 2 orchestrates innate immune responses against murine norovirus and is antagonized by the viral protein NS7

“…MNV NS1/2 interacts with host protein VAPA to enhance viral replication (45), and NS3 interacts with microtubule-associated protein GEF-H1, which plays a role in immune detection of viral replication (46). MNV NS7 is the viral replicase and catalyzes replication of the viral genome.…”

The Interaction between the DOCK7 Protein and the E2 Protein of Classical Swine Fever Virus Is Not Involved with Viral Replication or Pathogenicity

“…DOCK7 is a member of the Dock-C subfamily of the DOCK family, which has roles in activating G-proteins. Although the specific role for Dock7 in regards to virus infections has never been identified, other GEF proteins have been shown to play a role in virus infections [ 29 ] or in the mediation of the inflammatory response [ 30 ]. In this study, the protein–protein interaction between CSFV E2 and DOCK7 was confirmed in swine cells infected with CSFV by using two very different methodologies: co-immunoprecipitation, as a biochemical approach, and proximity ligation assay (PLA), which detects protein interactions intracellularly.…”