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ABSTRACT: Enterovirus 71 is a positive-stranded RNA virus which is capable of inhibiting innate immunity. Among viral encoded proteins, the 3C protein compromises the type I IFN response mediated by retinoid acid inducible gene-I (RIG-I) or Toll-like receptor 3 that activates interferon regulatory 3 (IRF3) and IRF7. In the present study, we report that enterovirus 71 down-regulates IRF7 through the 3C protein, which inhibits the function of IRF7. When expressed in mammalian cells, the 3C protein mediates cleavage of IRF7 rather than that of IRF3. This process is insensitive to inhibitors of capsase, proteasome, lysosome and autophagy. H40D substitution in the 3C active site abolishes its activity whereas R84Q or V154S substitution in the RNA binding motif has no effect. Furthermore, 3C-mediated cleavage occurs at the Q189S190 junction within the constitutive activation domain of IRF7, resulting in two cleaved IRF7 fragments that are incapable of activating IFN expression. Ectopic expression of wild type IRF7 limits EV71 replication. On the other hand, expression of the amino-terminal domain of IRF7 enhances EV71 infection, which correlates with its ability to interact with and inhibit IRF3. These results suggest that control of IRF7 by the 3C protein may represent a viral mechanism to escape cellular responses.
Journal of Virology 11/2012; · 5.40 Impact Factor
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ABSTRACT: As a brain protection strategy, antegrade selective cerebral perfusion (ASCP) is widely used in thoracic aorta surgery with deep hypothermic circulatory arrest (DHCA), yet the oxygen management for ASCP has never been standardized. The aim of this study was to investigate the possible neuroprotective effects of hyperoxia management during deep hyperthermia for ASCP combined with DHCA in a rabbit model. Rabbits were assigned into four groups: sham group, without cardiopulmonary bypass (CPB); DHCA group, DHCA for 80 minutes; ASCP group, ASCP combined with DHCA; and SH group, hyperoxia management combined with ASCP and DHCA. Hyperoxia management was performed when the nasopharyngeal temperature was below 22°C. Deep hypothermic circulatory arrest was initiated when nasopharyngeal temperature reached 16-18°C. Blood samples were withdrawn to determine blood gas indexes and neurobiochemical markers of damage, and brain tissues were stored for biochemical analysis. Cerebral oxygen balance was performed better in the SH group compared with the DHCA group and the ASCP group. Hyperoxia management did not increase lipid peroxidation with lower malondialdehyde levels in the SH group compared with the DHCA group and the ASCP group (p < 0.05). S100 calcium binding protein B in the SH group was lower compared with the DHCA group and the ASCP group (p < 0.05). There was no significant difference of neuron-specific enolase in the SH group compared with the sham group. Hyperoxia management during deep hypothermia provided substantial dissolved oxygen and demonstrated better cerebral protection over normoxia management.
ASAIO journal (American Society for Artificial Internal Organs: 1992) 05/2012; 58(4):330-6. · 1.39 Impact Factor
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ABSTRACT: Toll-like receptors (TLRs) mediated immune response is crucial for combating pathogens and must be tightly controlled. Tripartite motif (TRIM) proteins are a family of proteins that is involved in a variety of biological and physiological processes. Some members of the TRIM family are important in the regulation of innate immunity. Although it has been shown that TRIM38 negatively regulates innate immunity, the mechanisms by which it does so have not been fully addressed. In this study, we demonstrated that TRIM38 negatively regulates Toll-like receptor 3 (TLR3)-mediated type I interferon signaling by targeting TIR domain-containing adaptor inducing IFN-β (TRIF). We found that overexpression of TRIM38 inhibits TLR3-mediated type I interferon signaling, whereas knockdown of TRIM38 has the reverse effects. We further showed that TRIM38 targets TRIF, a critical adaptor protein downstream of TLR3. TRIF is co-immunoprecipitated with TRIM38, and domain mapping experiments show that PRYSPRY of TRIM38 interacts with the N-terminus of TRIF. Overexpression of TRIM38 decreased expression of overexpressed and endogenous TRIF. This effect could be inhibited by MG132 treatment. Furthermore, the RING/B-box domain of TRIM38 is critical for K48-linked polyubiquitination and proteasomal degradation of TRIF. Collectively, our results suggest that TRIM38 may act as a novel negative regulator for TLR3-mediated type I interferon signaling by targeting TRIF for degradation.
PLoS ONE 01/2012; 7(10):e46825. · 4.09 Impact Factor
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ABSTRACT: The nonstructural protein 1 (NSP1) of rotavirus has been reported to block interferon (IFN) signaling by mediating proteasome-dependent degradation of IFN-regulatory factors (IRFs) and (or) the β-transducin repeat containing protein (β-TrCP). However, in addition to these targets, NSP1 may subvert innate immune responses via other mechanisms.
The NSP1 of rotavirus OSU strain as well as the IRF3 binding domain truncated NSP1 of rotavirus SA11 strain are unable to degrade IRFs, but can still inhibit host IFN response, indicating that NSP1 may target alternative host factor(s) other than IRFs. Overexpression of NSP1 can block IFN-β promoter activation induced by the retinoic acid inducible gene I (RIG-I), but does not inhibit IFN-β activation induced by the mitochondrial antiviral-signaling protein (MAVS), indicating that NSP1 may target RIG-I. Immunoprecipitation experiments show that NSP1 interacts with RIG-I independent of IRF3 binding domain. In addition, NSP1 induces down-regulation of RIG-I in a proteasome-independent way.
Our findings demonstrate that inhibition of RIG-I mediated type I IFN responses by NSP1 may contribute to the immune evasion of rotavirus.
Virology Journal 12/2011; 8:526. · 2.34 Impact Factor
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ABSTRACT: Influenza A virus mutates rapidly, rendering antiviral therapies and vaccines directed against virus-encoded targets ineffective. Knowledge of the host factors and molecular pathways exploited by influenza virus will provide further targets for novel antiviral strategies. However, the critical host factors involved in influenza virus infection have not been fully defined.
We demonstrated that LAMP3, a member of lysosome-associated membrane glycoprotein (LAMP) family, was significantly induced in human lung epithelial (A549) cells upon influenza A virus infection. Knockdown of LAMP3 expression by RNA interference attenuated production of viral nucleoprotein (NP) as well as virus titers. Confocal microscopy results demonstrated that viral NP is colocalized within LAMP3 positive vesicles at early stages of virus infection. Furthermore, knockdown of LAMP3 expression led to a reduction in nuclear accumulation of viral NP and impeded virus replication.
LAMP3 is an influenza A virus inducible gene, and plays an important role in viral post-entry steps. Our observations may provide insights into the mechanism of influenza virus replication and potential targets for novel anti-influenza therapeutics.
Virology Journal 08/2011; 8:384. · 2.34 Impact Factor
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ABSTRACT: The tripartite motif (TRIM) proteins are a family of more than 70 members in human. However, only a few of them have been well studied. The TRIM proteins contain the conserved RING, B-box, coiled-coil, and SPRY domains, most of which are involved in protein ubiquitination. TRIM38 is a member of the TRIM protein family, which we studied in more detail here as its functions are largely unknown.
Our study shows that, similar to other TRIM family members, TRIM38 is localized in the cytoplasm. TRIM38 increases ubiquitination of other cellular proteins and catalyzes self-ubiquitination. TRIM38 also promotes K63- and K48-linked ubiquitination of cellular proteins. An intact RING domain is important for the functions of TRIM38. In addition, enterovirus 71 infection induces TRIM38 degradation.
Our observations demonstrate that TRIM38 has E3 ubiquitin ligase activity and can be degraded during virus infection. These findings may provide insight into innate immune signaling pathways.
Virology Journal 02/2011; 8(1):61. · 2.34 Impact Factor
