Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The seroprevalence of antibody to hepatitis C virus (anti-HCV) and the possible modes of transmission of HCV were investigated in Gizan, southern Saudi Arabia. The sample size chosen to give an adequate estimate of the seroprevalence, about 1500, was based on the assumption that 5% of the population in Gizan were anti-HCV-positive. Sera from 1482 subjects (705 males, 777 females; aged > or = 10 years) were initially screened for anti-HCV using a commercial, ubiquitin-based enzyme immunoassay. Repeatedly reactive sera were confirmed positive using second-generation immunoassays. Serum samples were also tested by ELISA for hepatitis B surface antigen (HbsAg) and antibodies to this antigen and to the hepatitis B core antigen. Of the subjects tested, 27 (1.8%) were anti-HCV-positive. Exposure to HCV was generally similar in both sexes, age-prevalence curves for anti-HCV peaking in males aged > 49 years (6.2%) and in females aged 40-49 years (5.0%). In the youngest subjects, those aged 10-19 years, the HbsAg carrier rate was significantly higher in males (10.4%) than in females (3.6%). Exposure to the hepatitis B virus was similar in both sexes (31.0% in males v. 28.6% in females). Some 7.4% and 14.8% of the 27 anti-HCV-positive cases had histories of schistosomiasis and blood transfusion, respectively. The corresponding values for the 1455 anti-HCV-negative cases investigated, 1.1% for schistosomiasis and 3.5% for blood transfusion, were much lower. The spouses and other family members of eight anti-HCV-positive index cases were investigated but none was anti-HCV-positive.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Profile of hepatitis C virus and the possible modes of transmission of the virus in the Gizan area of Saudi Arabia: a community-based study. 748 30

Evaluation of liver biopsies in hepatitis C is aimed at confirming the clinical and serologic diagnosis, grading of necroinflammatory activity, staging of consecutive fibrosis, ruling out or confirming liver diseases of different etiology, and assessment of therapeutic effects. Usually, the course of chronic hepatitis C virus (HCV) infection is slow, with mild inflammatory changes. Nevertheless, even in mild asymptomatic chronic hepatitis C episodes of higher inflammatory activity associated with extensive piecemeal necrosis and porto-central bridging, necrosis can accelerate the course of the disease. For this reason, the traditional, morphologically based classification of chronic hepatitis and the term "chronic persistent hepatitis" have lost their predictive usefulness, especially in hepatitis C. Chronic hepatitis should be characterized by etiologic designation as well as grade and stage of the disease. Portal lymphoid aggregates, some inflammatory bile duct damage and mild steatosis are the most characteristic features by which hepatitis C can be differentiated from other progressive inflammatory liver diseases. Antibodies directed against HCV antigens allow identification of viral proteins by immunohistochemistry. Immunostaining for hepatitis B antigens, for alpha-1-antitrypsin and copper staining are helpful in detecting hepatitis B and congenital liver diseases (Wilson's disease, alpha-1-antitrypsin deficiency) as possible causes of chronic progressive inflammatory liver disease. Centrilobular Mallory's hyalin, identified by immunostaining for ubiquitin in combination with perivenular fibrosis, is helpful in diagnosing concomitant alcoholic liver disease. In our own biopsy material (n = 100) and autopsy material (n = 58), HIV/HCV-coinfected patients have a significantly higher rate of fibrosis and cirrhosis than HIV patients without HCV infection. Hepatitis C can apparently aggravate the course of HIV infection. Our morphologic findings support the clinical observation that chronic HCV infection seems to be the main cause of liver failure, especially in the risk group of HCV/HIV-coinfected hemophiliacs.
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PMID:Histopathologic findings in chronic hepatitis C. 883 87

The hepatitis B virus X protein (HBX) is essential for the establishment of HBV infection in vivo and exerts a pleiotropic effect on diverse cellular functions. The yeast two-hybrid system had indicated that HBX could interact with two subunits of the 26S proteasome. Here we demonstrate an association in vivo of HBX with the 26S proteasome complex by coimmunoprecipitation and colocalization upon sucrose gradient centrifugation. Expression of HBX in HepG2 cells caused a modest decrease in the proteasome's chymotrypsin- and trypsin-like activities and in hydrolysis of ubiquitinated lysozyme, suggesting that HBX functions as an inhibitor of proteasome. In these cells, HBX is degraded with a half-life of 30 min. Proteasome inhibitors retarded this rapid degradation and caused a marked increase in the level of HBX and an accumulation of HBX in polyubiquitinated form. Thus, the low intracellular level of HBX is due to rapid proteolysis by the ubiquitin-proteasome pathway. Surprisingly, the proteasome inhibitors blocked the transactivation by HBX, and this effect was not a result of a squelching phenomenon due to HBX accumulation. Therefore, proteasome function is possibly required for the transactivation function of HBX. The inhibition of protein breakdown by proteasomes may account for the multiple actions of HBX and may be an important feature of HBV infection, possibly in helping stabilize viral gene products and suppressing antigen presentation.
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PMID:Hepatitis B virus X protein is both a substrate and a potential inhibitor of the proteasome complex. 1043 10

Hepatitis B virus (HBV) has a unique fourth open reading frame coding for a 16.5-kDa protein known as hepatitis B virus X protein (HBX). The importance of HBX in the life cycle of HBV has been well established, but the underlying molecular function of HBX remains controversial. We previously identified a proteasome subunit PSMA7 that interacts specifically with HBX in the Saccharomyces cerevisiae two-hybrid system. Here we demonstrate that PSMC1, an ATPase-like subunit of the 19 S proteasome component, also interacts with HBX and PSMA7. Analysis of the interacting domains among PSMA7, PSMC1, and HBX by deletion and site-directed mutagenesis suggested a mutually competitive structural relationship among these polypeptides. The competitive nature of these interactions is further demonstrated using a modified yeast two-hybrid dissociator system. The crucial HBX sequences involved in interaction with PSMA7 and PSMC1 are important for its function as a transcriptional coactivator. HBX, while functioning as a coactivator of AP-1 and acidic activator VP-16 in mammalian cells, had no effect on the transactivation function of their functional orthologs GCN4 and Gal4 in yeast. Overexpression of PSMC1 seemed to suppress the expression of various reporters in mammalian cells; this effect, however, was overcome by coexpression of HBX. In addition, HBX expression inhibited the cellular turnover of c-Jun and ubiquitin-Arg-beta-galactosidase, two well known substrates of the ubiquitin-proteasome pathway. Thus, interaction of HBX with the proteasome complex in metazoan cells may underlie the functional basis of proteasome as a cellular target of HBX.
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PMID:Structural and functional characterization of interaction between hepatitis B virus X protein and the proteasome complex. 1074 18

We have previously shown that alpha/beta interferon (IFN-alpha/beta) and IFN-gamma inhibit hepatitis B virus (HBV) replication noncytopathically in the livers of HBV transgenic mice and in hepatocyte cell lines derived from these mice. The present study was designed to identify transcriptionally controlled hepatocellular genes that are tightly associated with the inhibition of HBV replication and that might, therefore, mediate the antiviral effect of these cytokines. Twenty-nine genes were identified, many of which have known or potential antiviral activity. Notably, multiple components of the immunoproteasome and ubiquitin-like proteins were strongly induced by both IFN-alpha/beta and IFN-gamma, as were a number of GTP-binding proteins, including GTPases with known antiviral activity, chemokines, signaling molecules, and miscellaneous genes associated with antigen processing, DNA-binding, or cochaperone activity and several expressed sequence tags. The results suggest that one or more members of this relatively small subset of genes may mediate the antiviral effect of IFN-alpha/beta and IFN-gamma against HBV. We have already exploited this information by demonstrating that the antiviral activity of IFN-alpha/beta and IFN-gamma is proteasome dependent.
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PMID:Searching for interferon-induced genes that inhibit hepatitis B virus replication in transgenic mouse hepatocytes. 1250 40

Mallory bodies (MBs) are aggresomes, composed of cytokeratin and various other proteins, which form in diseased liver because of disruption in the ubiquitin-proteasome protein degradation pathway. Heat shock proteins (hsp's) are thought to be involved in this process because it was discovered that MB formation is induced by heat shock in drug-primed mice. It has been reported that ubiquitin and a mutant form of ubiquitin (UBB(+1)) are found in aggresomes formed in the neurons in Alzheimer's disease and in the liver MBs in various liver diseases. In addition, hsp 70 has been found in aggresomes in Alzheimer's and in MBs in drug-primed mice. Therefore, we hypothesized that hsp's might be involved in MB formation in human liver diseases. Liver biopsy sections were double-stained using ubiquitin and hsp 70 or 90b antibodies. Both hsps 70 and 90b were found in MBs in all liver diseases investigated including primary billiary cirrhosis, nonalcoholic steatohepatitis, hepatitis B and C, idiopathic cirrhosis, alcoholic hepatitis, and hepatocellular carcinoma. Ubiquitin and the hsp's colocalized in all MBs in the diseased liver sections. These results indicate that hsp involvement in MB formation is similar to that seen in aggresome formation in other conformational diseases.
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PMID:Heat shock proteins are present in mallory bodies (cytokeratin aggresomes) in human liver biopsy specimens. 1271 Sep 48

Hepatitis B virus X protein (HBx) is closely involved in the development of hepatocellular carcinoma, a highly vascularized solid tumor. Here we show that HBx increases the transcriptional activity and protein level of hypoxia-inducible factor-1alpha (HIF-1alpha) under both normoxic and hypoxic conditions, and it also stimulates angiogenesis. HBx directly interacted with the bHLH/PAS domain of HIF-1alpha but not with the von Hippel-Lindau protein (pVHL). HBx decreased the binding of pVHL to HIF-1alpha and prevented ubiquitin-dependent degradation of HIF-1alpha. In HBx-transgenic mice, HIF-1alpha and vascular endothelial growth factor were strongly detected in the dysplastic lesion, where HBx was also more highly expressed than in the non-neoplastic region of the liver. An immunohistochemical study showed that microvessels are more abundant in the dysplastic lesion than in the non-neoplastic region. Our data suggest that HBx stabilizes HIF-1alpha and leads to angiogenesis during hepatocarcinogenesis.
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PMID:Hepatitis B virus X protein induces angiogenesis by stabilizing hypoxia-inducible factor-1alpha. 1468 11

Hepatitis B surface antigen (HBsAg) is the major component of the envelope of hepatitis B virus (HBV). As a resident membrane protein in the endoplasmic reticulum, it plays a key role in the viral morphogenesis. Little is known about cellular proteins that interact with HBsAg and thereby contributing to HBV morphogenesis. Using the yeast split-ubiquitin system, a number of cellular membrane proteins have been isolated in this study. These include a resident protein of endoplasmic reticulum (thioredoxin-related transmembrane protein 2), an adaptor protein involved in clathrin-mediated endocytosis and HIV-mediated downregulation of CD4, and a co-receptor of coxsakie B virus. The significance of our findings is suggested by the identification of cellular membrane proteins interacting with other virus proteins. Further functional analysis of these HBsAg- interacting cellular membrane proteins should shed new insights on their role in HBV morphogenesis.
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PMID:Identification of cellular membrane proteins interacting with hepatitis B surface antigen using yeast split-ubiquitin system. 1600 63

Hepatitis B virus (HBV) budding from infected cells is a tightly regulated process that requires both core and envelope structures. Here we report that HBV uses cellular gamma2-adaptin and Nedd4, possibly in conjunction with ubiquitin, to coordinate its assembly and release. In search of interaction partners of the viral L envelope protein, we previously discovered gamma2-adaptin, a putative endosomal sorting and trafficking adaptor of the adaptor protein complex family. We now demonstrate that the viral core interacts with the same gamma2-adaptor and that disruption of the HBV/gamma2-adaptin interactions inhibits virus production. Mutational analyses revealed a hitherto unknown ubiquitin-binding activity of gamma2-adaptin, specified by a ubiquitin-interacting motif, which contributes to its interaction with core. For core, the lysine residue at position 96, a potential target for ubiquitination, was identified to be essential for both gamma2-adaptin-recognition and virus production. The participation of the cellular ubiquitin system in HBV assembly was further suggested by our finding that core interacts with the endosomal ubiquitin ligase Nedd4, partly via its late domain-like PPAY sequence. Overexpression of a catalytically inactive Nedd4 mutant diminished HBV egress, indicating that protein ubiquitination is functionally involved in virus production. Additional evidence for a link of HBV assembly to the endosomal machinery was provided by immunolabeling studies that demonstrated colocalization of core and L with gamma2-adaptin in compartments positive for the late endosomal marker CD63. Together, these data indicate that an enveloped DNA virus exploits a new ubiquitin receptor together with endosomal pathway functions for egress from hepatocytes.
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PMID:Gamma-adaptin, a novel ubiquitin-interacting adaptor, and Nedd4 ubiquitin ligase control hepatitis B virus maturation. 1686 82

Hepatitis B virus (HBV) is an enveloped DNA virus that presumably buds at intracellular membranes of infected cells. HBV budding involves two endocytic host proteins, the ubiquitin-interacting adaptor gamma 2-adaptin and the Nedd4 ubiquitin ligase. Here, we demonstrate that HBV release also requires the cellular machinery that generates internal vesicles of multivesicular bodies (MVBs). In order to perturb the MVB machinery in HBV-replicating liver cells, we used ectopic expression of dominant-negative mutants of different MVB components, like the ESCRT-III complex-forming CHMP proteins and the Vps4 ATPases. Upon coexpression of mutated CHMP3, CHMP4B, or CHMP4C forms, as well as of ATPase-defective Vps4A or Vps4B mutants, HBV assembly and egress were potently blocked. Each of the MVB inhibitors arrested virus particle maturation by entrapping the viral core and large and small envelope proteins in detergent-insoluble membrane structures that closely resembled aberrant endosomal class E compartments. In contrast, HBV subvirus particle release was not affected by MVB inhibitors, hinting at different export routes used by viral and subviral particles. To further define the role gamma 2-adaptin plays in HBV formation, we examined the effects of its overexpression in virus-replicating cells. Intriguingly, excess gamma 2-adaptin blocked HBV production in a manner similar to the actions of CHMP and Vps4 mutants. Moreover, overexpressed gamma 2-adaptin perturbed the endosomal morphology and diminished the budding of a retroviral Gag protein, implying that it may act as a principal inhibitor of the MVB sorting pathway. Together, these results demonstrate that HBV exploits the MVB machinery with the aid of gamma 2-adaptin.
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PMID:Hepatitis B virus maturation is sensitive to functional inhibition of ESCRT-III, Vps4, and gamma 2-adaptin. 1755 70


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