Foot-and-Mouth Disease Virus Counteracts on Internal Ribosome Entry Site Suppression by G3BP1 and Inhibits G3BP1-Mediated Stress Granule Assembly via Post-Translational Mechanisms.

Xu Ye,Yanling Shi,Ting Pan,Shaobo Xiao,Xinyu Zhu,Kui Li,Haixue Zheng,Huanchun Chen,Liurong Fang,Dang Wang,Keshan Zhang,Jun Ma

doi:10.3389/fimmu.2018.01142

Abstract

Foot-and-mouth disease (FMD) is a highly contagious, severe viral illness notifiable to the World Organization for Animal Health. The causative agent, FMD virus (FMDV), replicates rapidly and efficiently inhibits host translation and the innate immune response for it has developed multiple tactics to evade host defenses and takes over gene expression machinery in the host cell. Here, we report a systemic analysis of the proteome and phosphoproteome of FMDV-infected cells. Bioinformatics analysis suggested that FMDV infection shuts off host cap-dependent translation, but leaves intact internal ribosome entry site (IRES)-mediated translation for viral proteins. Interestingly, several FMDV IRES-transacting factors, including G3BP stress granule assembly factor 1 (G3BP1), were dephosphorylated during FMDV infection. Ectopic expression of G3BP1 inhibited FMDV IRES activity, promoted assembly of stress granules, and activated innate immune responses, collectively suppressing FMDV replication. To counteract these host protective responses, FMDV-induced dephosphorylation of G3BP1, compromising its inhibitory effect on viral IRES. In addition, FMDV also proteolytically cleaved G3BP1 by its 3C protease (3Cpro). G3BP1 was cleaved at glutamic acid-284 (E284) by FMDV 3Cpro, and this cleavage completely lost the abilities of G3BP1 to activate innate immunity and to inhibit FMDV replication. Together, these data provide new insights into the post-translational mechanisms by which FMDV limits host stress and antiviral responses and indicate that G3BP1 dephosphorylation and its proteolysis by viral protease are important factors in the failure of host defense against FMDV infection.

Highlights

Foot-and-mouth disease (FMD) severely compromises livestock production, ensuing high economic losses, and international restrictions on the export of animals and animal products [1]
In order to get a comprehensive assessment of changes in host protein phosphorylation and signaling pathways induced by FMD virus (FMDV) infection, we subjected control and FMDV-infected samples to SILAC coupled with phosphopeptide enrichment by
The specific immunofluorescence corresponding to capsid protein VP3 of FMDV was readily detected in almost all of IBRS-2 cells infected with FMDV (MOI = 5) at 6 hpi, but no fluorescence was detected in mock-infected cells (Figure 1D)

Summary

Introduction

Foot-and-mouth disease (FMD) severely compromises livestock production, ensuing high economic losses, and international restrictions on the export of animals and animal products [1]. The etiologic agent, FMD virus (FMDV), is a positive-stranded RNA virus that belongs to the Aphthovirus genus of the Picornaviridae family. FMDV genome consists of a single-stranded RNA genome of 8.5 kb that encodes a large polyprotein translated under control of an internal ribosome entry site (IRES) located in the 5’ untranslated region [2]. During most picornavirus infections, cellular cap-dependent translation is shutdown, giving way to IRES-mediated translation of viral RNAs that synthesizes the viral polyprotein [3]. To propagate rapidly and efficiently at initial site of infection, FMDV has evolved multipronged strategies to regulate cellular gene expression, stress responses, and host innate immune responses [4,5,6]. Significant progress has been made in recent years in identifying the vital players in both the host and the pathogen, the complex interactions between FMDV and host cell, and the underlying molecular mechanisms, remain to be elucidated

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Conclusion