dsRNA Binding Domain of PKR Is Proteolytically Released by Enterovirus A71 to Facilitate Viral Replication

Chang, Yu‐Hsin; Lau, Kean Seng; Kuo, Rei-Lin; Horng, Jim-Tong

doi:10.3389/fcimb.2017.00284

Cited by 26 publications

(26 citation statements)

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“…SG formation is induced upon the activation of eIF2␣ kinases, such as PKR and PERK. While enterovirus infection induces PKR activation, leading to an increase in both phosphorylated PKR (p-PKR) and p-eIF2␣ levels (55,56), FMDV infection was shown to block the activation of this pathway (57), possibly via 3C pro -dependent lysosomal degradation of PKR (57). It has also been reported that the titers of FMDV LLV can be rescued in PKR knockout cells (58), hinting at a possible role for L pro in suppressing PKR signaling.…”

Section: Discussionmentioning

confidence: 99%

Foot-and-Mouth Disease Virus Leader Protease Cleaves G3BP1 and G3BP2 and Inhibits Stress Granule Formation

Visser

Medina

Rabouw

et al. 2019

J Virol

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Like other viruses, the picornavirus foot-and-mouth disease virus (FMDV; genus Aphthovirus), one of the most notorious pathogens in the global livestock industry, needs to navigate antiviral host responses to establish an infection. There is substantial insight into how FMDV suppresses the type I interferon (IFN) response, but it is largely unknown whether and how FMDV modulates the integrated stress response. Here, we show that the stress response is suppressed during FMDV infection. Using a chimeric recombinant encephalomyocarditis virus (EMCV), in which we functionally replaced the endogenous stress response antagonist by FMDV leader protease (L pro ) or 3C pro , we demonstrate an essential role for L pro in suppressing stress granule (SG) formation. Consistently, infection with a recombinant FMDV lacking L pro resulted in SG formation. Additionally, we show that L pro cleaves the known SG scaffold proteins G3BP1 and G3BP2 but not TIA-1. We demonstrate that the closely related equine rhinitis A virus (ERAV) L pro also cleaves G3BP1 and G3BP2 and also suppresses SG formation, indicating that these abilities are conserved among aphthoviruses. Neither FMDV nor ERAV L pro interfered with phosphorylation of RNAdependent protein kinase (PKR) or eIF2␣, indicating that L pro does not affect SG formation by inhibiting the PKR-triggered signaling cascade. Taken together, our data suggest that aphthoviruses actively target scaffolding proteins G3BP1 and G3BP2 and antagonize SG formation to modulate the integrated stress response. IMPORTANCE The picornavirus foot-and-mouth disease virus (FMDV) is a notorious animal pathogen that puts a major economic burden on the global livestock industry. Outbreaks have significant consequences for animal health and product safety. Like many other viruses, FMDV must manipulate antiviral host responses to establish infection. Upon infection, viral double-stranded RNA (dsRNA) is detected, which results in the activation of the RNA-dependent protein kinase (PKR)-mediated stress response, leading to a stop in cellular and viral translation and the formation of stress granules (SG), which are thought to have antiviral properties. Here, we show that FMDV can suppress SG formation via its leader protease (L pro ). Simultaneously, we observed that L pro can cleave the SG scaffolding proteins G3BP1 and G3BP2. Understanding the molecular mechanisms of the antiviral host response evasion strategies of FMDV may help to develop countermeasures to control FMDV infections in the future.

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Section: Discussionmentioning

confidence: 99%

Foot-and-Mouth Disease Virus Leader Protease Cleaves G3BP1 and G3BP2 and Inhibits Stress Granule Formation

Visser

Medina

Rabouw

et al. 2019

J Virol

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“…However, this does not seem to be the case for enteroviruses. It has been reported that PKR and eIF2␣ are phosphorylated during infection with several enteroviruses (37,(56)(57)(58), indicating that the viruses do not block activation of the ISR. Consistently, we did not observe an effect of 2A pro on the phosphorylation of PKR and eIF2␣.…”

Section: Discussionmentioning

confidence: 99%

Essential Role of Enterovirus 2A Protease in Counteracting Stress Granule Formation and the Induction of Type I Interferon

Visser

Langereis

Rabouw

et al. 2019

J Virol

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Most viruses have acquired mechanisms to suppress antiviral alpha/beta interferon (IFN-␣/␤) and stress responses. Enteroviruses (EVs) actively counteract the induction of IFN-␣/␤ gene transcription and stress granule (SG) formation, which are increasingly implicated as a platform for antiviral signaling, but the underlying mechanisms remain poorly understood. Both viral proteases (2A pro and 3C pro ) have been implicated in the suppression of these responses, but these conclusions predominantly rely on ectopic overexpression of viral proteases or addition of purified viral proteases to cell lysates. Here, we present a detailed and comprehensive comparison of the effect of individual enterovirus proteases on the formation of SGs and the induction of IFN-␣/␤ gene expression in infected cells for representative members of the enterovirus species EV-A to EV-D. First, we show that SG formation and IFN-␤ induction are suppressed in cells infected with EV-A71, coxsackie B3 virus (CV-B3), CV-A21, and EV-D68. By introducing genes encoding CV-B3 proteases in a recombinant encephalomyocarditis virus (EMCV) that was designed to efficiently activate antiviral responses, we show that CV-B3 2A pro , but not 3C pro , is the major antagonist that counters SG formation and IFN-␤ gene transcription and that 2A pro 's proteolytic activity is essential for both functions. 2A pro efficiently suppressed SG formation despite protein kinase R (PKR) activation and ␣ subunit of eukaryotic translation initiation factor 2 phosphorylation, suggesting that 2A pro antagonizes SG assembly or promotes its disassembly. Finally, we show that the ability to suppress SG formation and IFN-␤ gene transcription is conserved in the 2A pro of EV-A71, CV-A21, and EV-D68. Collectively, our results indicate that enterovirus 2A pro plays a key role in inhibiting innate antiviral cellular responses. IMPORTANCE Enteroviruses are important pathogens that can cause a variety of diseases in humans, including aseptic meningitis, myocarditis, hand-foot-and-mouth disease, conjunctivitis, and acute flaccid paralysis. Like many other viruses, enteroviruses must counteract antiviral cellular responses to establish an infection. It has been suggested that enterovirus proteases cleave cellular factors to perturb antiviral pathways, but the exact contribution of viral proteases 2A pro and 3C pro remains elusive. Here, we show that 2A pro , but not 3C pro , of all four human EV species (EV-A to EV-D) inhibits SG formation and IFN-␤ gene transcription. Our observations suggest that enterovirus 2A pro has a conserved function in counteracting antiviral host responses and thereby is the main enterovirus "security protein." Understanding the molecular mechanisms of enterovirus immune evasion strategies may help to develop countermeasures to control infections with these viruses. FIG 5 Enterovirus 2A pro suppresses the induction of type I IFN gene expression. (A)HeLa R19 cells were infected with the indicated viruses at an MOI of 10, and the cells were lysed at 8 hpi, total cell...

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“…Under such a condition, the doublestranded RNA-dependent protein kinase PKR phosphorylates the regulatory α subunit of eukaryotic translation initiation factor 2 (eIF2α) to block translation of both cellular and viral mRNAs. After EV-A71 infection, 3C pro cleaves PKR to activate viral translation and replication [23]. Notably, a cleavage fragment of eIF5B, a product of viral 3C pro , can be substituted for eIF2 to deliver Met-tRNAi to the 40S ribosomal subunit, while eIF2α is phosphorylated and inactivated by viral infection [24].…”

Section: Inhibition Of Host Cell Translation After Ev-a71 Infectionmentioning

confidence: 99%

Translation control of Enterovirus A71 gene expression

Lai

Chen

et al. 2020

J Biomed Sci

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Upon EV-A71 infection of a host cell, EV-A71 RNA is translated into a viral polyprotein. Although EV-A71 can use the cellular translation machinery to produce viral proteins, unlike cellular translation, which is capdependent, the viral RNA genome of EV-A71 does not contain a 5′ cap and the translation of EV-A71 protein is cap-independent, which is mediated by the internal ribosomal entry site (IRES) located in the 5′ UTR of EV-A71 mRNA. Like many other eukaryotic viruses, EV-A71 manipulates the host cell translation devices, using an elegant RNA-centric strategy in infected cells. During viral translation, viral RNA plays an important role in controlling the stage of protein synthesis. In addition, due to the cellular defense mechanism, viral replication is limited by down-regulating translation. EV-A71 also utilizes protein factors in the host to overcome antiviral responses or even use them to promote viral translation rather than host cell translation. In this review, we provide an introduction to the known strategies for EV-A71 to exploit cellular translation mechanisms.

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dsRNA Binding Domain of PKR Is Proteolytically Released by Enterovirus A71 to Facilitate Viral Replication

Cited by 26 publications

References 50 publications

Foot-and-Mouth Disease Virus Leader Protease Cleaves G3BP1 and G3BP2 and Inhibits Stress Granule Formation

Foot-and-Mouth Disease Virus Leader Protease Cleaves G3BP1 and G3BP2 and Inhibits Stress Granule Formation

Essential Role of Enterovirus 2A Protease in Counteracting Stress Granule Formation and the Induction of Type I Interferon

Translation control of Enterovirus A71 gene expression

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