scholarly journals Activation of Src family kinases by hepatitis B virus HBx protein and coupled signaling to Ras.

1997 ◽  
Vol 17 (11) ◽  
pp. 6427-6436 ◽  
Author(s):  
N P Klein ◽  
R J Schneider
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Map Kinase ◽  
Tyrosine Kinases ◽  
Map Kinases ◽  
Cultured Cells ◽  
Ras Signaling ◽  
B Virus ◽  
Mitogen Activated Protein ◽  
Stimulation Of

The HBx protein of hepatitis B virus (HBV) is a small transcriptional transactivator that is essential for infection by the mammalian hepadnaviruses and is thought to be a cofactor in HBV-mediated liver cancer. HBx stimulates signal transduction pathways by acting in the cytoplasm, which accounts for many but not all of its transcriptional activities. Studies have shown that HBx protein activates Ras and downstream Ras signaling pathways including Raf, mitogen-activated protein (MAP) kinase kinase kinase (MEK), and MAP kinases. In this study, we investigated the mechanism of activation of Ras by HBx because it has been found to be central to the ability of HBx protein to stimulate transcription and to release growth arrest in quiescent cells. In contrast to the transient but strong stimulation of Ras typical of autocrine factors, activation of Ras by HBx protein was found to be constitutive but moderate. HBx induced the association of Ras upstream activating proteins Shc, Grb2, and Sos and stimulated GTP loading onto Ras, but without directly participating in complex formation. Instead, HBx is shown to stimulate Ras-activating proteins by functioning as an intracellular cytoplasmic activator of the Src family of tyrosine kinases, which can signal to Ras. HBx protein stimulated c-Src and Fyn kinases for a prolonged time. Activation of Src is shown to be indispensable for a number of HBx activities, including activation of Ras and the Ras-Raf-MAP kinase pathway and stimulation of transcription mediated by transcription factor AP-1. Importantly, HBx protein expressed in cultured cells during HBV replication is shown to activate the Ras signaling pathway. Mechanisms by which HBx protein might activate Src kinases are discussed.

scholarly journals Regulation of Hepatitis B Virus Replication by the Ras-Mitogen-Activated Protein Kinase Signaling Pathway

2003 ◽  
Vol 77 (14) ◽  
pp. 7707-7712 ◽  
Author(s):  
Yanyan Zheng ◽  
Jie Li ◽  
Deborah L. Johnson ◽  
Jing-hsiung Ou
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Map Kinase ◽  
Deletion Mapping ◽  
Hbv Replication ◽  
B Virus ◽  
Mitogen Activated Protein ◽  
Map Kinase Pathway ◽  
External Stimuli ◽  
Kinase Pathway

ABSTRACT The replication of hepatitis B virus (HBV) can be regulated by a variety of factors, including hormones, growth factors, and cytokines. However, the molecular mechanisms of these regulations are largely unknown. Ras is a small GTPase that responds to many of these external stimuli. In this study, we investigated the possible effect of Ras on the replication of HBV. Our results indicated that activated Ras could suppress the replication of HBV in both Huh7 and HepG2 cells. This suppression was independent of the X protein and most likely occurred at the transcriptional level. Deletion-mapping analysis of the HBV core promoter and its upstream ENI and ENII enhancers revealed multiple elements responsive to activated Ras. This suppression of HBV replication by activated Ras was apparently mediated by the mitogen-activated protein (MAP) kinase pathway, as it was accompanied by activation of ERK1/2 and abolished by the MEK1/2 inhibitor U0126. Our results thus indicate that external stimuli may suppress HBV replication through the Ras-MAP kinase pathway.

scholarly journals Sustained Activation of p38 Mitogen-Activated Protein Kinase and c-Jun N-Terminal Kinase Pathways by Hepatitis B Virus X Protein Mediates Apoptosis via Induction of Fas/FasL and Tumor Necrosis Factor (TNF) Receptor 1/TNF-α Expression

2004 ◽  
Vol 24 (23) ◽  
pp. 10352-10365 ◽  
Author(s):  
Wen-Horng Wang ◽  
Gérald Grégori ◽  
Ronald L. Hullinger ◽  
Ourania M. Andrisani
Keyword(s):  
Hepatitis B Virus ◽  
Tumor Necrosis Factor ◽  
Hepatitis B ◽  
Map Kinase ◽  
Tumor Necrosis ◽  
P38 Map Kinase ◽  
Tnf Α ◽  
B Virus ◽  
Mitogen Activated Protein ◽  
Necrosis Factor

ABSTRACT Activation of the cellular stress pathways (c-Jun N-terminal kinase [JNK] and p38 mitogen-activated protein [MAP] kinase) is linked to apoptosis. However, whether both pathways are required for apoptosis remains unresolved. Hepatitis B virus X protein (pX) activates p38 MAP kinase and JNK pathways and, in response to weak apoptotic signals, sensitizes hepatocytes to apoptosis. Employing hepatocyte cell lines expressing pX, which was regulated by tetracycline, we investigated the mechanism of apoptosis by p38 MAP kinase and JNK pathway activation. Inhibition of the p38 MAP kinase pathway rescues by 80% the initiation of pX-mediated apoptosis, whereas subsequent apoptotic events involve both pathways. pX-mediated activation of p38 MAP kinase and JNK pathways is sustained, inducing the transcription of the death receptor family genes encoding Fas/FasL and tumor necrosis factor receptor 1 (TNFR1)/TNF-α and the p53-regulated Bax and Noxa genes. The pX-dependent expression of Fas/FasL and TNFR1/TNF-α mediates caspase 8 activation, resulting in Bid cleavage. In turn, activated Bid, acting with pX-induced Bax and Noxa, mediates the mitochondrial release of cytochrome c, resulting in the activation of caspase 9 and apoptosis. Combined antibody neutralization of FasL and TNF-α reduces by 70% the initiation of pX-mediated apoptosis. These results support the importance of the pX-dependent activation of both the p38 MAP kinase and JNK pathways in pX-mediated apoptosis and suggest that this mechanism of apoptosis occurs in vivo in response to weak apoptotic signals.

scholarly journals ssAAVs containing cassettes encoding SaCas9 and guides targeting hepatitis B virus inactivate replication of the virus in cultured cells

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Tristan Scott ◽  
Buhle Moyo ◽  
Samantha Nicholson ◽  
Mohube Betty Maepa ◽  
Koichi Watashi ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Cultured Cells ◽  
B Virus

scholarly journals Engineered External Guide Sequences Are Highly Effective in Inhibiting Gene Expression and Replication of Hepatitis B Virus in Cultured Cells

PLoS ONE ◽  
2013 ◽  
Vol 8 (6) ◽  
pp. e65268 ◽  
Author(s):  
Zhigang Zhang ◽  
Gia-Phong Vu ◽  
Hao Gong ◽  
Chuan Xia ◽  
Yuan-Chuan Chen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Cultured Cells ◽  
B Virus ◽  
Highly Effective

scholarly journals Inactivation of Hepatitis B Virus Replication in Cultured Cells and In Vivo with Engineered Transcription Activator-Like Effector Nucleases

2013 ◽  
Vol 21 (10) ◽  
pp. 1889-1897 ◽  
Author(s):  
Kristie Bloom ◽  
Abdullah Ely ◽  
Claudio Mussolino ◽  
Toni Cathomen ◽  
Patrick Arbuthnot
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Virus Replication ◽  
Cultured Cells ◽  
Transcription Activator ◽  
B Virus

scholarly journals Activation of Focal Adhesion Kinase by Hepatitis B Virus HBx Protein: Multiple Functions in Viral Replication

2006 ◽  
Vol 80 (9) ◽  
pp. 4406-4414 ◽  
Author(s):  
Michael J. Bouchard ◽  
Lihua Wang ◽  
Robert J. Schneider
Keyword(s):  
Signal Transduction ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Viral Replication ◽  
Calcium Signaling ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Cellular Transformation ◽  
B Virus ◽  
Stimulation Of

ABSTRACT The hepatitis B virus (HBV) X protein (HBx) is a multifunctional regulator of cellular signal transduction and transcription pathways and has a critical role in HBV replication. Much of the cytoplasmic signal transduction activity associated with HBx expression and its stimulation of viral replication is attributable to HBx-induced activation of calcium signaling pathways involving Pyk2 and Src tyrosine kinases. To further characterize upstream signal transduction pathways that are required for HBx activity, including activation of Src and mitogen-activated protein kinase (MAPK) cascades, we determined whether focal adhesion kinase (FAK), a known regulator of Src family kinases and the other member of the Pyk2/FAK kinase family, is activated by HBx. We report that HBx activates FAK and that FAK activation is important for multiple HBx functions. Dominant inhibiting forms of FAK blocked HBx activation of Src kinases and downstream signal transduction, HBx stimulation of NF-κB and AP-1-dependent transcription, and HBV DNA replication. We also demonstrate that HBx-induced activation of FAK is dependent on cellular calcium signaling, which is modulated by HBx. Moreover, prolonged expression of HBx increases both FAK activity and its level of expression. FAK activation may play a role in cellular transformation and cancer progression. HBx stimulation of FAK activity and abundance may also be relevant as a potential cofactor in HBV-associated hepatocellular carcinoma.

scholarly journals Interaction between STAT-3 and HNF-3 Leads to the Activation of Liver-Specific Hepatitis B Virus Enhancer 1 Function

2002 ◽  
Vol 76 (6) ◽  
pp. 2721-2729 ◽  
Author(s):  
Gulam Waris ◽  
Aleem Siddiqui
Keyword(s):  
Gene Expression ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Transcriptional Control ◽  
Viral Gene Expression ◽  
Cooperative Interaction ◽  
Viral Gene ◽  
Mobility Shift ◽  
B Virus ◽  
Stimulation Of

ABSTRACT The signal transducer and activator of transcription 3 (STAT-3), a member of the STAT family of proteins, binds to a large number of transcriptional control elements and regulates gene expression in response to cytokines. While it binds to its cognate nucleotide sequences, it has been recently shown to directly interact with other transcriptional factors in the absence of DNA. We report here one such novel interaction between STAT-3 and hepatocyte nuclear factor 3 (HNF-3) in the absence of DNA. We have identified a STAT-3 binding site within the core domain of hepatitis B virus (HBV) enhancer 1. The HBV enhancer 1 DNA-STAT-3 protein interaction is shown to be stimulated by interleukin-6 (IL-6) and epidermal growth factor, which leads to an overall stimulation of HBV enhancer 1 function and viral gene expression. Using mobility shift assays and transient transfection schemes, we demonstrate a cooperative interaction between HNF-3 and STAT-3 in mediating the cytokine-mediated HBV enhancer function. Cytokine stimulation of HBV gene expression represents an important regulatory scheme of direct relevance to liver disease pathogenesis associated with HBV infection.

scholarly journals MicroRNA 130a Regulates both Hepatitis C Virus and Hepatitis B Virus Replication through a Central Metabolic Pathway

2018 ◽  
Vol 92 (7) ◽  
Author(s):  
Xiaoqiong Duan ◽  
Shilin Li ◽  
Jacinta A. Holmes ◽  
Zeng Tu ◽  
Yujia Li ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Target Genes ◽  
Viral Infections ◽  
Cultured Cells ◽  
Guide Rna ◽  
Hbv Replication ◽  
B Virus

ABSTRACTHepatitis C virus (HCV) infection has been shown to regulate microRNA 130a (miR-130a) in patient biopsy specimens and in cultured cells. We sought to identify miR-130a target genes and to explore the mechanisms by which miR-130a regulates HCV and hepatitis B virus (HBV) replication. We used bioinformatics software, including miRanda, TargetScan, PITA, and RNAhybrid, to predict potential miR-130a target genes. miR-130a and its target genes were overexpressed or were knocked down by use of small interfering RNA (siRNA) or clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 guide RNA (gRNA). Selected gene mRNAs and their proteins, together with HCV replication in OR6 cells, HCV JFH1-infected Huh7.5.1 cells, and HCV JFH1-infected primary human hepatocytes (PHHs) and HBV replication in HepAD38 cells, HBV-infected NTCP-Huh7.5.1 cells, and HBV-infected PHHs, were measured by quantitative reverse transcription-PCR (qRT-PCR) and Western blotting, respectively. We selected 116 predicted target genes whose expression was related to viral pathogenesis or immunity for qPCR validation. Of these, the gene encoding pyruvate kinase in liver and red blood cell (PKLR) was confirmed to be regulated by miR-130a overexpression. miR-130a overexpression (via a mimic) knocked down PKLR mRNA and protein levels. A miR-130a inhibitor and gRNA increased PKLR expression, HCV replication, and HBV replication, while miR-130a gRNA and PKLR overexpression increased HCV and HBV replication. Supplemental pyruvate increased HCV and HBV replication and rescued the inhibition of HCV and HBV replication by the miR-130a mimic and PKLR knockdown. We concluded that miR-130a regulates HCV and HBV replication through its targeting of PKLR and subsequent pyruvate production. Our data provide novel insights into key metabolic enzymatic pathway steps regulated by miR-130a, including the steps involving PKLR and pyruvate, which are subverted by HCV and HBV replication.IMPORTANCEWe identified that miR-130a regulates the target genePKLRand its subsequent effect on pyruvate production. Pyruvate is a key intermediate in several metabolic pathways, and we identified that pyruvate plays a key role in regulation of HCV and HBV replication. This previously unrecognized, miRNA-regulated antiviral mechanism has implications for the development of host-directed strategies to interrupt the viral life cycle and prevent establishment of persistent infection for HCV, HBV, and potentially other viral infections.

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