Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ebola virus (EboV) causes rapidly fatal hemorrhagic fever in humans and there is currently no effective treatment. We found that the infection of African green monkey kidney (Vero) cells by vesicular stomatitis viruses bearing the EboV glycoprotein (GP) requires the activity of endosomal cysteine proteases. Using selective protease inhibitors and protease-deficient cell lines, we identified an essential role for cathepsin B (CatB) and an accessory role for cathepsin L (CatL) in EboV GP-dependent entry. Biochemical studies demonstrate that CatB and CatL mediate entry by carrying out proteolysis of the EboV GP subunit GP1 and support a multistep mechanism that explains the relative contributions of these enzymes to infection. CatB and CatB/CatL inhibitors diminish the multiplication of infectious EboV-Zaire in cultured cells and may merit investigation as anti-EboV drugs.
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PMID:Endosomal proteolysis of the Ebola virus glycoprotein is necessary for infection. 1583 16

Ebola and Marburg viruses are the causative agents of rapidly progressive hemorrhagic fevers with high mortality rates. Pre- or post-exposure treatments against the diseases are currently not available for human use. In the field, establishment of strict quarantine measures preventing further virus transmission are still the only way to fight the infections. However, our knowledge of Ebola and Marburg viruses has markedly increased as a result of two recent discoveries discussed in this review. Chandran et al. have elucidated the mechanism by which Ebola GP is converted to a fusion-active form. Infectivity of Ebola virus was shown to be dependent on the cleavage of GP by cellular endosomal proteases, cathepsin B and L, thus opening new therapeutic approaches options. As for Jones SM et al., they have successfully vaccinated monkeys with recombinant vesicular stomatitis virus expressing Ebola or Marburg virus surface glycoprotein GP, a promising vaccine approach.
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PMID:[Ebola and Marburg viruses: the humans strike back]. 1659 10

The roles of cellular proteases in Moloney murine leukemia virus (MLV) infection were investigated using MLV particles pseudotyped with vesicular stomatitis virus (VSV) G glycoprotein as a control for effects on core MLV particles versus effects specific to Moloney MLV envelope protein (Env). The broad-spectrum inhibitors cathepsin inhibitor III and E-64d gave comparable dose-dependent inhibition of Moloney MLV Env and VSV G pseudotypes, suggesting that the decrease did not involve the envelope protein. Whereas, CA-074 Me gave a biphasic response that differentiated between Moloney MLV Env and VSV G at low concentrations, at which the drug is highly selective for cathepsin B, but was similar for both glycoproteins at higher concentrations, at which CA-074 Me inhibits other cathepsins. Moloney MLV infection was lower on cathepsin B knockout fibroblasts than wild-type cells, whereas VSV G infection was not reduced on the B-/- cells. Taken together, these results support the notion that cathepsin B acts at an envelope-dependent step while another cathepsin acts at an envelope-independent step, such as uncoating or viral-DNA synthesis. Virus binding was not affected by CA-074 Me, whereas syncytium induction was inhibited in a dose-dependent manner, consistent with cathepsin B involvement in membrane fusion. Western blot analysis revealed specific cathepsin B cleavage of SU in vitro, while TM and CA remained intact. Infection could be enhanced by preincubation of Moloney MLV with cathepsin B, consistent with SU cleavage potentiating infection. These data suggested that during infection of NIH 3T3 cells, endocytosis brings Moloney MLV to early lysosomes, where the virus encounters cellular proteases, including cathepsin B, that cleave SU.
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PMID:Host cell cathepsins potentiate Moloney murine leukemia virus infection. 1763 28

Ebolavirus (EBOV) entry into cells requires proteolytic disassembly of the viral glycoprotein, GP. This proteolytic processing, unusually extensive for an enveloped virus entry protein, is mediated by cysteine cathepsins, a family of endosomal/lysosomal proteases. Previous work has shown that cleavage of GP by cathepsin B (CatB) is specifically required to generate a critical entry intermediate. The functions of this intermediate are not well understood. We used a forward genetic strategy to investigate this CatB-dependent step. Specifically, we generated a replication-competent recombinant vesicular stomatitis virus bearing EBOV GP as its sole entry glycoprotein and used it to select viral mutants resistant to a CatB inhibitor. We obtained mutations at six amino acid positions in GP that independently confer complete resistance. All of the mutations reside at or near the GP1-GP2 intersubunit interface in the membrane-proximal base of the prefusion GP trimer. This region forms a part of the "clamp" that holds the fusion subunit GP2 in its metastable prefusion conformation. Biochemical studies suggest that most of the mutations confer CatB independence not by altering specific cleavage sites in GP but rather by inducing conformational rearrangements in the prefusion GP trimer that dramatically enhance its susceptibility to proteolysis. The remaining mutants did not show the preceding behavior, indicating the existence of multiple mechanisms for acquiring CatB independence during entry. Altogether, our findings suggest that CatB cleavage is required to facilitate the triggering of viral membrane fusion by destabilizing the prefusion conformation of EBOV GP.
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PMID:A forward genetic strategy reveals destabilizing mutations in the Ebolavirus glycoprotein that alter its protease dependence during cell entry. 1984 33

dsRNA is an important pathogen-associated molecular pattern that is primarily recognized by cytosolic pattern-recognition receptors of the innate-immune system during virus infection. This recognition results in the activation of inflammasome-associated caspase-1 and apoptosis of infected cells. In this study, we used high-throughput proteomics to identify secretome, the global pattern of secreted proteins, in human primary macrophages that had been activated through the cytoplasmic dsRNA-recognition pathway. The secretome analysis revealed cytoplasmic dsRNA-recognition pathway-induced secretion of several exosome-associated proteins, as well as basal and dsRNA-activated secretion of lysosomal protease cathepsins and cysteine protease inhibitors (cystatins). Inflammasome activation was almost completely abolished by cathepsin inhibitors in response to dsRNA stimulation, as well as encephalomyocarditis virus and vesicular stomatitis virus infections. Interestingly, Western blot analysis showed that the mature form of cathepsin D, but not cathepsin B, was secreted simultaneously with IL-18 and inflammasome components ASC and caspase-1 in cytoplasmic dsRNA-stimulated cells. Furthermore, small interfering RNA-mediated silencing experiments confirmed that cathepsin D has a role in inflammasome activation. Caspase-1 activation was followed by proteolytic processing of caspase-3, indicating that inflammasome activation precedes apoptosis in macrophages that had recognized cytoplasmic RNA. Like inflammasome activation, apoptosis triggered by dsRNA stimulation and virus infection was effectively blocked by cathepsin inhibition. In conclusion, our results emphasize the importance of cathepsins in the innate immune response to virus infection.
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PMID:Recognition of cytoplasmic RNA results in cathepsin-dependent inflammasome activation and apoptosis in human macrophages. 2125 72

The Zaire ebolavirus (EBOV) glycoprotein (GP) is cleaved into two subunits (GP1 and GP2) that are both required for virus attachment and entry into cells. Sequence changes in the GP have been proposed to increase pathogenesis and to alter virus growth properties. Mutations in GP acquired during EBOV tissue culture passage have also been reported to change virus growth properties. Here, we report the isolation of six amino acid mutations in EBOV GP that spontaneously appeared during recovery and passage of an EBOV-Makona GP-pseudotyped vesicular stomatitis virus (VSV), two of which also occur during passage of EBOV clinical isolates in tissue culture. Each of the six mutations resulted in increased virus growth in monkey and human cell lines. All mutations are located in the GP2 fusion subunit and increase entry kinetics of EBOV virus-like particles (VLPs). The gain-of-entry function mapped to two mechanistic phenotypes. Mutations in heptad repeat 1 (HR1) decreased the requirement for cathepsin B activity for viral infection. Mutations directly within the fusion loop increased entry kinetics without altering the cathepsin B dependence. Several mutations in the fusion loop were substitutions of residues present in other ebolavirus glycoproteins, illustrating the evolutionary paths for maintaining an optimally functioning fusion loop under selection pressure.IMPORTANCEZaire ebolavirus (EBOV) is the causative agent of the highly lethal Ebola virus disease and poses a significant threat to the global health community. Approved antivirals against EBOV are lacking; however, promising therapies targeting the EBOV glycoprotein are being developed. Efficacy testing of these candidate therapeutics relies on EBOV laboratory stocks, which when grown in tissue culture may acquire mutations in the glycoprotein. These mutations can produce inaccurate results in therapeutic testing. Until recently, distinguishing between tissue culture mutations and naturally occurring polymorphisms in EBOV GP was difficult in the absence of consensus clinical GP sequences. Here, we utilize recombinant VSV (rVSV) pseudotyped with the consensus clinical EBOV Makona GP to identify several mutations that have emerged or have potential to emerge in EBOV GP during tissue culture passage. Identifying these mutations informs the EBOV research community as to which mutations may arise during preparation of laboratory virus stocks.
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PMID:Growth-Adaptive Mutations in the Ebola Virus Makona Glycoprotein Alter Different Steps in the Virus Entry Pathway. 3002 90

Ebola virus (EBOV) infection can cause severe and frequently fatal disease in human patients. The EBOV glycoprotein (GP) mediates viral entry into host cells. For this, GP depends on priming by the pH-dependent endolysosomal cysteine proteases cathepsin B (CatB) and, to a lesser degree, cathepsin L (CatL), at least in most cell culture systems. However, there is limited information on whether and how EBOV-GP can acquire resistance to CatB/L inhibitors. Here, we addressed this question using replication-competent vesicular stomatitis virus bearing EBOV-GP. Five passages of this virus in the presence of the CatB/CatL inhibitor MDL28170 were sufficient to select resistant viral variants and sequencing revealed that all GP sequences contained a V37A mutation, which, in the context of native GP, is located in the base of the GP surface unit. In addition, some GP sequences harbored mutation S195R in the receptor-binding domain. Finally, mutational analysis demonstrated that V37A but not S195R conferred resistance against MDL28170 and other CatB/CatL inhibitors. Collectively, a single amino acid substitution in GP is sufficient to confer resistance against CatB/CatL inhibitors, suggesting that usage of CatB/CatL inhibitors for antiviral therapy may rapidly select for resistant viral variants.
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PMID:Analysis of Resistance of Ebola Virus Glycoprotein-Driven Entry Against MDL28170, An Inhibitor of Cysteine Cathepsins. 3161 32