Enterovirus 71 3C Inhibits Cytokine Expression through Cleavage of the TAK1/TAB1/TAB2/TAB3 Complex

Enterovirus 71 (EV71) is an emerging pathogen causing hand, foot, and mouth disease (HFMD) and fatal neurological diseases in infants and young children due to their underdeveloped immunocompetence. EV71 infection can induce cellular apoptosis through a variety of pathways, which promotes EV71 release. The viral protease 3C plays an important role in EV71-induced apoptosis. However, the molecular mechanism responsible for 3C-triggered apoptosis remains elusive. Here, we found that EV71 3C directly interacted with PinX1, a telomere binding protein. Furthermore, 3C cleaved PinX1 at the site of Q50-G51 pair through its protease activity. Overexpression of PinX1 reduced the level of EV71-induced apoptosis and EV71 release, whereas depletion of PinX1 by small interfering RNA promoted apoptosis induced by etoposide and increased EV71 release. Taken together, our study uncovered a mechanism that EV71 utilizes to promote host cell apoptosis through cleavage of cellular protein PinX1 by 3C.IMPORTANCE EV71 3C plays an important role in processing viral proteins and interacting with host cells. In this study, we showed that 3C promoted apoptosis through cleaving PinX1, a telomere binding protein, and that this cleavage facilitated EV71 release. Our study demonstrated that PinX1 plays an important role in EV71 release and revealed a novel mechanism that EV71 utilizes to induce apoptosis. This finding is important in understanding EV71-host cell interactions and has potential impact on understanding other enterovirus-host cell interactions.KEYWORDS enterovirus 71, 3C, PinX1, apoptosis E nterovirus 71 (EV71) is an emerging pathogen that was originally isolated from an infant with central nervous system disease in California (1). Since then, EV71 has caused several large-scale epidemic outbreaks throughout the world, especially in the Asia-Pacific region (2-4). These outbreaks caused significant morbidity and mortality and severely endangered the public health (5). EV71 infection causes hand, foot, and mouth disease (HFMD) and fatal neurological diseases, such as aseptic meningitis, brainstem encephalitis, and neurogenic pulmonary edema (NPE), in infants and young children due to their underdeveloped immunocompetence (6). To date, there are no effective therapeutic medicines or vaccines for EV71.EV71 belongs to the Picornaviridae family with a single positive-stranded RNA genome. Translation of the RNA genome produces a single polyprotein precursor that is subsequently processed into structural (VP1, VP2, VP3, and VP4) and nonstructural (2A, 2B, 2C, 3A, 3B, 3C, and 3D) proteins (7). In addition to its role in viral precursor processing (8), 3C is also involved in a number of biological processes. It has been reported that 3C cleaves cellular CstF-64 protein, which inhibits host RNA processing and polyadenylation (9). Interferon-regulatory factor 7 (IRF7) (10), TIR domain-containing adaptor inducing beta interferon (TRIF) (11) and the TAK1/TAB1/

“…Several host factors have been found to be cleaved by 3C (9)(10)(11)(12). In this study, we identified PinX1 as a novel target of EV71 3C.…”

Section: Discussionmentioning

confidence: 77%

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confidence: 99%

Enterovirus 71 3C Promotes Apoptosis through Cleavage of PinX1, a Telomere Binding Protein

Yao

et al. 2017

“…Several studies have suggested that EV71 suppresses antiviral immunity (9,10,(13)(14)(15)(16)(17). In addition to inhibition of type I IFN induction, EV71 has evolved strategies to counter inflammasome activation through cleavage of NLRP3 by viral proteases 2A and 3C (18).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the 3C protease induces apoptosis by inducing cleavage of PinX1, an intrinsic telomerase inhibitor, to facilitate EV71 release (12). Other important roles of 3C are to dampen immune responses by impeding the RIG-I-MAVS interaction or by cleaving a series of host factors, including TIR domain-containing adaptor inducing IFN-␤ (TRIF), interferon regulatory factor 7/9, and TAK1/TAB1/TAB2/TAB3 complex (13)(14)(15)(16)(17).…”

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confidence: 99%

Enterovirus 71 Inhibits Pyroptosis through Cleavage of Gasdermin D

Lei

Zhang

Xiao

et al. 2017

Self Cite

120

Enterovirus 71 (EV71) can cause hand-foot-and-mouth disease (HFMD) in young children. Severe infection with EV71 can lead to neurological complications and even death. However, the molecular basis of viral pathogenesis remains poorly understood. Here, we report that EV71 induces degradation of gasdermin D (GSDMD), an essential component of pyroptosis. Remarkably, the viral protease 3C directly targets GSDMD and induces its cleavage, which is dependent on the protease activity. Further analyses show that the Q193-G194 pair within GSDMD is the cleavage site of 3C. This cleavage produces a shorter N-terminal fragment spanning amino acids 1 to 193 (GSDMD ). However, unlike the N-terminal fragment produced by caspase-1 cleavage, this fragment fails to trigger cell death or inhibit EV71 replication. Importantly, a T239D or F240D substitution abrogates the activity of GSDMD consisting of amino acids 1 to 275 (GSDMD ). This is correlated with the lack of pyroptosis or inhibition of viral replication. These results reveal a previously unrecognized strategy for EV71 to evade the antiviral response.IMPORTANCE Recently, it has been reported that GSDMD plays a critical role in regulating lipopolysaccharide and NLRP3-mediated interleukin-1␤ (IL-1␤) secretion. In this process, the N-terminal domain of p30 released from GSDMD acts as an effector in cell pyroptosis. We show that EV71 infection downregulates GSDMD. EV71 3C cleaves GSDMD at the Q193-G194 pair, resulting in a truncated N-terminal fragment disrupted for inducing cell pyroptosis. Notably, GSDMD 1-275 (p30) inhibits EV71 replication whereas GSDMD 1-193 does not. These results reveal a new strategy for EV71 to evade the antiviral response. KEYWORDS EV71, HFMD, 3C, GSDMDE nterovirus 71 (EV71) is a major etiological agent of hand-foot-and-mouth disease (HFMD) which affects infants and children younger than 5 years of age. Most of these infections are self-limited with mild symptoms, including fever and vesicular eruptions mainly on the skin of hands and feet and in the mouth. However, some patients show severe neurological diseases, including aseptic meningitis, acute flaccid paralysis, encephalitis, and pulmonary edema. Since it was first isolated in California in 1974 (1-3), EV71 infection has caused many large-scale epidemics in the world, especially in the Asia-Pacific region (1, 4-6). To date, there are no effective therapeutic drugs for EV71 infection.EV71 belongs to the Enterovirus genus of the family Picornaviridae. The viral genome is approximately 7,500 nucleotides in length, with a single open reading frame that encodes a large precursor protein that is subsequently processed into three structural (VP0, VP1, and VP3) and seven nonstructural (2A, 2B, 2C, 3A, 3B, 3C, and 3D) proteins by the virus-encoded protease 2A or 3C (7). The three structural proteins and the RNA form provirions, in which VP0 is cleaved into VP2 and VP4 by RNA or 3CD, but the

“…It possesses both proteolytic and RNA binding activities (32,33), which enable the protease to perform multiple tasks in systems involving viral replication and pathogen-host interactions. Increasing evidence suggests that EV-A71 3C pro targets innate immune factors, such as RIG-I, TRIF, IRF7/9, the TAK1/TAB1/TAB2/TAB3 complex, and NLRP3, to modulate type I IFN and cytokine responses (34)(35)(36)(37)(38). Recently, EV-D68 3C pro has been reported to target IRF7 and TRIF to disable innate sensing responses (39,40).…”

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confidence: 99%

Disruption of MDA5-Mediated Innate Immune Responses by the 3C Proteins of Coxsackievirus A16, Coxsackievirus A6, and Enterovirus D68

Rui

Wang

et al. 2017

Coxsackievirus A16 (CV-A16), CV-A6, and enterovirus D68 (EV-D68) belong to the Picornaviridae family and are major causes of hand, foot, and mouth disease (HFMD) and pediatric respiratory disease worldwide. The biological characteristics of these viruses, especially their interplay with the host innate immune system, have not been well investigated. In this study, we discovered that the 3C pro proteins from CV-A16, CV-A6, and EV-D68 bind melanoma differentiation-associated gene 5 (MDA5) and inhibit its interaction with MAVS. Consequently, MDA5-triggered type I interferon (IFN) signaling in the retinoic acid-inducible gene I-like receptor (RLR) pathway was blocked by the CV-A16, CV-A6, and EV-D68 3C pro proteins. Furthermore, the CV-A16, CV-A6, and EV-D68 3C pro proteins all cleave transforming growth factor ␤-activated kinase 1 (TAK1), resulting in the inhibition of NF-B activation, a host response also critical for Toll-like receptor (TLR)-mediated signaling. Thus, our data demonstrate that circulating HFMD-associated CV-A16 and CV-A6, as well as severe respiratory disease-associated EV-D68, have developed novel mechanisms to subvert host innate immune responses by targeting key factors in the RLR and TLR pathways. Blocking the ability of 3C pro proteins from diverse enteroviruses and coxsackieviruses to interfere with type I IFN induction should restore IFN antiviral function, offering a potential novel antiviral strategy.IMPORTANCE CV-A16, CV-A6, and EV-D68 are emerging pathogens associated with hand, foot, and mouth disease and pediatric respiratory disease worldwide. The pathogenic mechanisms of these viruses are largely unknown. Here we demonstrate that the CV-A16, CV-A6, and EV-D68 3C pro proteins block MDA5-triggered type I IFN induction. The 3C pro proteins of these viruses bind MDA5 and inhibit its interaction with MAVS. In addition, the CV-A16, CV-A6, and EV-D68 3C pro proteins cleave TAK1 to inhibit the NF-B response. Thus, our data demonstrate that circulating HFMDassociated CV-A16 and CV-A6, as well as severe respiratory disease-associated EV-D68, have developed a mechanism to subvert host innate immune responses by simultaneously targeting key factors in the RLR and TLR pathways. These findings indicate the potential merit of targeting the CV-A16, CV-A6, and EV-D68 3C pro proteins as an antiviral strategy.KEYWORDS MDA5, TAK1, MAVS, 3C protease, CV-A16, CV-A6, EV-D68, HFMD, innate immune response