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Journal of Virology, February 1999, p. 1672-1681, Vol. 73, No. 2
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Hepatitis C Virus Core Protein Enhances NF-kappa B Signal Pathway Triggering by Lymphotoxin-beta Receptor Ligand and Tumor Necrosis Factor Alpha

Li-Ru You, Chun-Ming Chen, and Yan-Hwa Wu Lee*

Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan, Republic of China

Received 7 August 1998/Accepted 20 October 1998


    ABSTRACT
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Our previous study indicated that the core protein of hepatitis C virus (HCV) can associate with tumor necrosis factor receptor (TNFR)-related lymphotoxin-beta receptor (LT-beta R) and that this protein-protein interaction plays a modulatory effect on the cytolytic activity of recombinant form LT-beta R ligand (LT-alpha 1beta 2) but not tumor necrosis factor alpha (TNF-alpha ) in certain cell types. Since both TNF-alpha /TNFR and LT-alpha 1beta 2/LT-beta R are also engaged in transcriptional activator NF-kappa B activation or c-Jun N-terminal kinase (JNK) activation, the biological effects of the HCV core protein on these regards were elucidated in this study. As demonstrated by the electrophoretic mobility shift assay, the expression of HCV core protein prolonged or enhanced the TNF-alpha or LT-alpha 1beta 2-induced NF-kappa B DNA-binding activity in HuH-7 and HeLa cells. The presence of HCV core protein in HeLa or HuH-7 cells with or without cytokine treatment also enhanced the NF-kappa B-dependent reporter plasmid activity, and this effect was more strongly seen with HuH-7 cells than with HeLa cells. Western blot analysis suggested that this modulation of the NF-kappa B activity by the HCV core protein was in part due to elevated or prolonged nuclear retention of p50 or p65 species of NF-kappa B in core protein-producing cells with or without cytokine treatment. Furthermore, the HCV core protein enhanced or prolonged the Ikappa B-beta degradation triggering by TNF-alpha or LT-alpha 1beta 2 both in HeLa and HuH-7 cells. In contrast to that of Ikappa B-beta , the increased degradation of Ikappa B-alpha occurred only in LT-alpha 1beta 2-treated core-producing HeLa cells and not in TNF-alpha -treated cells. Therefore, the HCV core protein plays a modulatory effect on NF-kappa B activation triggering by both cytokines, though the mechanism of NF-kappa B activation, in particular the regulation of Ikappa B degradation, is rather cell line and cytokine specific. Studies also suggested that the HCV core protein had no effect on TNF-alpha -stimulated JNK activity in both HeLa and HuH-7 cells. These findings, together with our previous study, strongly suggest that among three signaling pathways triggered by the TNF-alpha -related cytokines, the HCV core protein potentiates NF-kappa B activation in most cell types, which in turn may contribute to the chronically activated, persistent state of HCV-infected cells.


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Hepatitis C virus (HCV) is a positive-strand RNA virus that has been identified as the major causative agent of posttransfection non-A, non-B hepatitis (25, 51). Its persistent infection may result in chronic active hepatitis, cirrhosis, and hepatocellular carcinoma (19, 83). Intriguingly, HCV persists despite the presence of virus-specific cytotoxic T-lymphocytes (11, 20, 50, 80). The reason for the failure of host immune response to resolve HCV infection is not known. This could be due in part to the effect of viral gene products on the host immune system, as had been noted for several viruses (36). Of at least 10 viral proteins encoded by the HCV genome (10, 37, 59, 100), its nucleocapsid core protein may have such a feature.

Several studies suggested that the core protein of HCV possesses several distinguishing properties. It is phosphorylated (87) and has both cytoplasmic and nuclear localization (61, 86, 88). Additionally, the core protein has regulatory roles in viral and cellular genes and also has effects on cell growth and proliferation (21, 65, 73-77, 87, 88, 113). Recently, studies from several laboratories, including ours, have identified several cellular factors that can associate with the HCV core protein. For example, the core protein forms the complex with apolipoprotein AII of the lipid droplet, which in turn may contribute to the liver steatosis in HCV-infected chimpanzee or humans (11). The interaction between the HCV core protein and the tumor necrosis factor receptor (TNFR)-related lymphotoxin-beta receptor (LT-beta R) (3, 15, 28) was also demonstrated by two different groups (21, 65). This interaction modulates one of the biological activities, i.e., cytolytic activity, of LT-beta R triggering by its recombinant ligand (LT-alpha 1beta 2) (17, 18, 108) in HeLa cells but not in HuH-7 cells (21). Moreover, the HCV core protein also interacts with TNFR 1 (TNFRI) (113), although its effect on TNF-induced cytolytic activity still remains controversial (21, 76, 113). Like the TNF ligand receptor family (reviewed in references 1, 39, 97, and 103), the LT-beta R is also engaged in activation of the transcriptional factor NF-kappa B and c-Jun in some cell types (22, 62, 71). Conceivably, the interaction of HCV core protein and LT-beta R or TNFRI may potentiate their NF-kappa B or c-Jun N-terminal kinase (JNK) signaling pathways.

The NF-kappa B signaling pathway is a key component of the cellular response to a variety of extracellular stimuli, including TNF-alpha , interleukin-1 (IL-1) and phorbol ester (reviewed in references 4, 8, 98, and 105). This transcriptional factor, known to regulate a large number of genes involved in inflammatory response, cell proliferation, and apoptosis, is composed of homo- and heterodimers of Rel family proteins (reviewed in references 4, 5, and 10). These family proteins include at least the following five distinct members: C-Rel, p50, p52, p65 (RelA), and RelB; of these, the p50/p65 heterodimer is the most abundant and ubiquitous (reviewed in references 4 and 10). In the uninduced cells, NF-kappa B is sequestered in the cytoplasm by binding to a labile Ikappa B family protein with a regulatory and inhibitory function, of which Ikappa B-alpha and Ikappa B-beta appear to be the key members (106). Upon induction by several agents, including virus, inflammatory cytokines, and stresses, the intracellular signaling pathways that generally converge on Ikappa B rapid phosphorylation and/or modification and subsequent degradation in the proteasome are activated (reviewed in references 4 and 8), thus allowing NF-kappa B complexes to enter the nucleus and activate the target genes. After degradation, the Ikappa B-alpha is rapidly replenished by NF-kappa B-mediated transcription of Ikappa B-alpha gene (57, 93), which then constitutes the autoregulatory loop of NF-kappa B-Ikappa B activation. Of note, unlike Ikappa B-alpha , which elicits only transient NF-kappa B activation, the Ikappa B-beta degradation causes a sustained activation of NF-kappa B due to a large lag period of Ikappa B-beta resynthesis (99). Recent studies have identified two cytokine-inducible Ikappa B kinases (IKK), termed IKKalpha and IKKbeta , which appear to form heterodimers in the large multiple complex (700 kDa) and catalyze Ikappa B site-specific phosphorylation (reviewed in references 64, 90, and 105). In spite of this tight regulatory loop for NF-kappa B activation, this transcriptional factor is activated by different viral proteins with oncogenic potential, such as human T-cell leukemia virus type 1 Tax (35, 43, 54, 92), Epstein-Barr virus latent membrane protein 1 (LMP-1) (40), the X protein of hepatitis B virus (24, 91).

The second branch of the stress response is the JNK pathway, which targets to the activation of transcriptional factor AP-1, ATF-2, and E1K-1 (29, 38, 49, 52, 53, 109). The signal transduction cascade of JNK activation is well defined and involves small GTP-binding proteins (Cdc42 and Rac), p21-activated protein kinase, and mitogen-activated protein kinase kinase kinase members (MEKK1 and MKK4) (27, 30, 56, 68, 84, 111). Many stimuli that induce NF-kappa B, such as TNF-alpha , UV irradiation, and lipopolysaccharide, also activate the JNK cascade (29, 79), thereby raising the possibility that the two pathways share common signal transduction components. Supporting this notion is the fact that TRAF2 and MEKK1 are two critical components of both the JNK and NF-kappa B stress response pathways (44, 58, 67, 79, 89), although contradictory findings were also reported (60). Despite these discrepancies, these two signal pathways diverge at a discrete level. For example, while JNK and its target c-Jun are critical mediators of apoptosis induced by TNF-alpha or ceramide (104, 110), the NF-kappa B in general has an anti-apoptotic effect (12, 60, 101, 107).

In this study, we examined the effects of HCV core protein on the NF-kappa B and JNK signaling pathways induced by LT-alpha 1beta 2 or TNF-alpha cytokine. Our results as shown here indicated that HCV core protein significantly potentiates NF-kappa B activation pathway triggering by LT-alpha 1beta 2 or TNF-alpha in HuH-7 cells and to a lesser extent in HeLa cells. These modulation effects are mediated by the differential sensitivity of Ikappa B-alpha and Ikappa B-beta degradation in the HCV core protein-producing cells, which in turn increases the nuclear retention of NF-kappa B subunits and potentiates both basal and cytokine-treated NF-kappa B activities. However, no significant modulation effect on JNK activation was detected in those two HCV core protein-producing cells when stimulated by LT-alpha 1beta 2 or TNF-alpha , suggesting that these two stress responses are differentially regulated by the HCV core protein.

HCV core protein enhances the NF-kappa B DNA-binding activity triggered by LT-alpha 1beta 2 or TNF-alpha in HeLa and HuH-7 cell lines. To elucidate whether the HCV core protein can modulate the NF-kappa B activation stimulated by LT-alpha 1beta 2 or TNF-alpha , the levels of induction of NF-kappa B DNA-binding activity in the nuclear extracts of both HCV core protein-expressing HeLa and HuH-7 cells (HeLa/C190 and HuH-7/C190) relative to that of their parental cells were compared at different times (30 min to 2 h) after the cytokine treatment. The NF-kappa B DNA-binding activity was examined by the electrophoretic mobility shift assay (EMSA) with a 32P-labeled 45-mer oligonucleotide probe (5'-TTGTTACAAGGGACTTTCCGCTGGGGACTTTCCAGGGAGGCGTGG-3') from the human immunodeficiency virus type 1 long terminal repeat containing two kappa B-binding sites. A mutated oligonucleotide with a single mutated kappa B site (5'-AGTTGAGGCGACTTTCCCAGGC-3') (22 mer; Santa Cruz) was also used to examine the binding specificity of NF-kappa B by EMSA. Results suggested that addition of the LT-alpha 1beta 2 ligand (500 ng/ml for 30 min to 1 h) greatly enhanced the NF-kappa B DNA-binding activity in HCV core protein-producing HuH-7/C190 and HeLa/C190 cells compared to that in their parental cells without the core protein (Fig. 1). The induction of NF-kappa B DNA-binding activity in LT-alpha 1beta 2-treated HeLa/C190 cells peaked at 30 min and slightly declined at 60 min (Fig. 1A), while in LT-alpha 1beta 2-treated HuH-7/C190 cells the induced NF-kappa B activity was still sustained at 60 min (Fig. 1B). A similar finding was obtained with TNF-alpha -treated HeLa/C190 cells. Treatment of TNF-alpha (20 ng/ml) in this cell line induced NF-kappa B activity significantly at 30 min, reached plateau at 60 min, and even remained elevated at 2 h. This NF-kappa B induction profile of HeLa/C190 cells is distinct from that observed for HeLa cells, as the NF-kappa B activity in the HeLa cells within the same period was only slightly induced by TNF-alpha (Fig. 2A). A distinct NF-kappa B activation kinetics was also observed for the TNF-alpha -treated HuH-7 and HuH-7/C190 cells (Fig. 2B). Although the NF-kappa B DNA-binding activities of these two cell lines were similar at the initial phase (30 min to 1 h) of induction, the activity of HuH-7/C190 at late phase (2 h) of treatment remained stronger than that of HuH-7 cells, suggesting a prolonged NF-kappa B activation in core-producing cells (Fig. 2B). Interestingly, a slight enhancement of NF-kappa B DNA-binding activity was also observed for both core-producing cells without the cytokine treatment (compare lanes 2 and 7 in Fig. 1A and B, and lanes 2 and 8 in Fig. 2A and B), implicating a constitutive activation of NF-kappa B in core-producing cells. It should be noted that the cytokine-induced NF-kappa B DNA-binding activity observed in these EMSAs is specific, since it was ablated by an excess of unlabeled wild-type competitor but not by the mutated one (see lanes 5, 6, 10, and 11 in Fig. 1 and lanes 6, 7, 12, and 13 in Fig. 2). Additionally, the invariant fast-migrating band was a nonspecific complex observed in NF-kappa B EMSA studies.


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  		FIG. 1.   EMSA of LT-alpha 1beta 2-stimulated NF-kappa B activation in various HCV core protein-producing cell lines. (A) NF-kappa B DNA-binding assays with nuclear extracts from untreated (lanes 2 and 7) or LT-alpha 1beta 2-treated HeLa and HeLa/C190 cells (lanes 3 to 6 and 8 to 11) were performed. The nuclear extracts were prepared as described by Mackay et al. (62) with some modification. Briefly, 2 × 106 cells after being pretreated with recombinant ligand LT-alpha 1beta 2 (500 ng/ml) (17) (kindly provided by J. L. Browning [Biogen]) for the proper time (30 min to 2 h) were harvested, washed, and suspended in a hypotonic buffer (buffer A) (20 mM HEPES [pH 7.4], 1 mM MgCl2, 10 mM KCl, 0.3% Nonidet P-40, 0.5 mM dithiothreitol [DTT], 0.1 mM EDTA) at 4°C for 30 min. Cell nuclei were collected by centrifugation, and the nuclear proteins were extracted with high-salt buffer (buffer B) (20 mM HEPES [pH 7.4], 20% glycerol, 0.42 M NaCl, 1 mM MgCl2, 10 mM KCl, and 0.5 mM DTT) for 1 h on ice. The supernatants recovered from centrifugation were stored at -70°C and used for an EMSA. For the EMSA, 5 µg of nuclear extracts was incubated with 50 fmol of 32P-end-labeled 45-mer synthetic double-stranded NF-kappa B oligonucleotide in a binding buffer (10 mM HEPES [pH 7.8], 5 mM MgCl2, 50 mM KCl, 0.5 mM DTT, 10% glycerol) containing 1 µg of poly(dI-dC) and 30 µg of bovine serum albumin. After incubation at room temperature for 45 min, the DNA-protein complex formed was separated from free oligonucleotide on a 4% native polyacrylamide gel using buffer containing 0.25× TBE (22.5 mM Tris-borate, 0.5 mM EDTA [pH 8.0]). After electrophoresis, the gel was dried and visualized with a PhosphorImager. Competition experiments were carried out by including unlabeled oligonucleotides containing either mutated (MT) (40-fold excess) (lanes 6 and 11) or wild-type (WT) (40-fold excess) (lanes 5 and 10) NF-kappa B binding sites. The main NF-kappa B-specific band shift induced is indicated. Lane 1, 32P-labeled free oligonucleotide. (B) Binding assays were identical to that described for panel A except that the nuclear extracts were prepared from HuH-7 and HuH-7/C190 cells.


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  		FIG. 2.   EMSA of TNF-alpha -stimulated NF-kappa B activation in various HCV core protein-producing cell lines. All experimental conditions were as described in the legend to Fig. 1 except that cells were stimulated with 20 ng of TNF-alpha /ml for 30, 60, or 120 min, respectively.

HCV core protein differentially enhances the NF-kappa B-dependent transcriptional activity triggered by LT-alpha 1beta 2 or TNF-alpha in HeLa and HuH-7 cells. We next assessed whether this enhancement or persistent induction of NF-kappa B DNA-binding activity in the HCV core protein-producing cells also could reflect on the NF-kappa B-dependent transcriptional activity. To this end, we examined the activity of luciferase reporter plasmid (NF-kappa B-fosp-1783:3.2Luc) (kindly provided by H. Wajant, University of Stuttgart, Stuttgart, Germany) under the control of the kappa B response element by transient transfection to HuH-7 or HeLa cells with or without the expression of core protein. Additionally, to provide a stringent control and to ensure the measured luciferase reporter plasmid activity mainly reflecting the NF-kappa B-specific transcriptional activity, an NF-kappa B-independent control plasmid (pCH110) (Pharmacia) containing beta -galactosidase reporter gene under simian virus 40 early promoter control was also cotransfected into cells, and its reporter activity was used for normalization. As shown in Fig. 3, relative to the level in the parental HeLa cells, about twofold enhancement of luciferase activity for both basal and cytokine-treated HeLa/C190 cells was noted (Fig. 3A). Likewise, the presence of core protein in HuH-7 cells exerted about 2.4-fold increase of basal NF-kappa B-dependent luciferase activity (Fig. 3B). However, treatment with either cytokine elicited a more than fivefold increase of luciferase activity in HuH-7/C190 cells relative to that of HuH cells, indicating a stronger potentiation of core-mediated NF-kappa B transcriptional activity in cytokine-stimulated HuH-7 cells than in cells without cytokine treatment (Fig. 3B). Therefore, coupled with the data from the EMSA (Fig. 1 and 2), our results clearly indicated that the HCV core protein can enhance the basal and cytokine-stimulated NF-kappa B transcriptional activities in both HeLa and HuH-7 cells, although the strength or kinetics of NF-kappa B induction may vary between cell lines.


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  		FIG. 3.   Analysis of cytokine-stimulated NF-kappa B-dependent transcriptional activity in HCV core protein-producing cells. (A) HeLa or HeLa/C190 cells seeded at 1.5 × 105 cells/well density were cotransfected with equal amounts (0.4 µg each) of NF-kappa B-dependent luciferase reporter plasmid and an internal control plasmid carrying the beta -galactosidase gene as a reporter with the SuperFect transfection reagent (Qiagen, Hilden, Germany). At 18 h posttransfection, cells were either left untreated (marked with -) or treated with TNF-alpha (20 ng/ml) or LT-alpha 1beta 2 (500 ng/ml) for 6 h prior to harvest. After three cycles of freezing and thawing, cells were lysed in 150 µl of lysis buffer (25 mM Tris-HCl [pH 7.8], 70 mM potassium phosphate buffer [pH 7.8], 2.1 mM MgCl2, 0.7 mM DTT, 0.1% Nonidet P-40, and protease inhibitor cocktail [Complete; Boehringer]). Eighty microliters of cell extracts recovered from the centrifugation was then mixed with 250 µl of luciferase assay buffer (43.2 mM glycylglycin [pH 7.8], 22 mM MgSO4, 2.4 mM EDTA, 7.4 mM ATP, 1 mM DTT, and 0.4 mg of bovine serum albumin/ml), and the resulting mixtures were assayed for luciferase activity by using 100 µl of 0.5 mM luciferin (Sigma) as the substrate and measured with AutoLumat LB953 (Berthold, Bad Wildbad, Germany). The beta -galactosidase activity in the cell extracts of cotransfected cells was determined essentially as described previously (21). The luciferase activities were normalized on the basis of beta -galactosidase expression. The NF-kappa B-dependent luciferase activity is represented as fold induction relative to that of HeLa cells without treatment. (B) All experimental conditions were similar to those described for panel A except that HuH-7 and HuH-7/C190 cells were used for study. Values shown in all panels are averages (means ± standard deviations) of one representative experiment in which each transfection was performed in triplicate.

HCV core protein does not alter the expression levels of NF-kappa B but affects their nuclear translocation. To understand the molecular basis of the enhancement of NF-kappa B activation in HCV core protein-producing cells, the total expression levels of NF-kappa B in different cell lines were examined by immunoblotting using antibodies specific for the subunits of NF-kappa B. Figures 4 reveals that although the expression levels of NF-kappa B family proteins p50, p52, and p65 in HuH-7 cells were more abundant than those in HeLa cells, the core protein did not affect their expression levels. Furthermore, following stimulation with TNF-alpha or LT-alpha 1beta 2 for 30 min or 1 h, there was little difference in the total expression levels of NF-kappa B family proteins in core-producing cells of HeLa and HuH-7 compared to those of their parental cells (data not shown). However, in response to 1 h of cytokine treatment, a marked enhancement of nuclear retention of p50 and p65, but not p52, was noted in HuH-7/C190 cells relative to that in parental HuH-7 cells (Fig. 5B and D). This enhancement of p50 or p65 nuclear retention by the core protein was not so evident in cytokine-treated HeLa cells, although a slight enhancement of the nuclear level of p50 was also noted in TNF-alpha -treated HeLa/C190 cells (compare Fig. 5A and C with Fig. 5B and D). Moreover, following the cytokine treatment a different kinetics of nuclear translocation of p50 and p65 between the LT-alpha 1beta 2-stimulated HeLa and HeLa/C190 cells was found: while the nuclear level of p50 or p65 in LT-alpha 1beta 2-treated (1 h) HeLa/C190 cells declined to the steady level, their levels in the nuclear fractions of HeLa cells within the same period remained elevated compared to pretreatment levels (Fig. 5A). Based on these results, it appears that the molecular mechanism for NF-kappa B activation in core-producing cells relative to that of their parental cells may differ between cell lines or cytokines. Additionally, a slight enhancement of the nuclear level of p50 was noted in both core-producing cells of HeLa or HuH-7 even without the cytokine treatment (Fig. 5). This suggested a constitutive activation of NF-kappa B by the HCV core protein, which is in accordance with the data from the EMSA (Fig. 1 and 2) and the reporter plasmid assay (Fig. 3).


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  		FIG. 4.   Western blot analysis of NF-kappa B/Rel and Ikappa B family proteins in various HCV core protein-producing cell lines. The total cell extracts (60 µg) from various cell lines lysed in 5× sampling buffer (55) were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis. Anti-NF-kappa B p65, p52, and p50 subunit antibodies (Upstate Biotechnology Inc.) and Ikappa B-alpha and Ikappa B-beta antibody (Santa Cruz) were used at the dilutions suggested by the manufacturer. The antigen-antibody reactions were visualized with horseradish peroxidase-coupled goat anti-rabbit immunoglobulin (Transduction) (1:2,000 dilution) using the enhanced chemiluminescence (ECL) detection system (Amersham). The control cell lysates (lane C) provided by the manufacturers are A341 cells for p65 and p50 and Raji cells for p52.


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  		FIG. 5.   Subcellular distribution of NF-kappa B family proteins in HCV core protein-producing cells after LT-alpha 1beta 2 or TNF-alpha stimulation. Cells were treated with 500 ng of LT-alpha 1beta 2 ligand/ml (panels A and B) or 20 ng of TNF-alpha /ml (panels C and D) for 30 or 60 min. The nuclear extracts (40 µg of protein each) prepared from the cytokine-treated or untreated cells were examined for the expression level of NF-kappa B family proteins (p65, p50, and p52) by immunoblotting using the ECL detection system.

HCV core protein enhances the degradation of Ikappa B-alpha and Ikappa B-beta in a cell line- and cytokine-specific manner. Since both LT-alpha 1beta 2 and TNF-alpha may elicit transient NF-kappa B activation by affecting the degradation of NF-kappa B inhibitor Ikappa B, the expression levels of Ikappa B inhibitors in HeLa and HeLa/C190 cell lines before or after the cytokine treatment were examined by immunoblot analysis using the Ikappa B-alpha - and Ikappa B-beta -specific antibodies. The results shown in Fig. 4 indicate that the HCV core protein did not alter the expression of Ikappa B-alpha and Ikappa B-beta . However, LT-alpha 1beta 2 treatment (500 ng/ml) of HeLa/C190 but not HeLa cells caused proteolytic breakdown of Ikappa B-alpha within 10- to 60-min time intervals and the amounts then returned to the control level by 1.5 h (Fig. 6A). This enhancement of Ikappa B-alpha degradation did not occur in HuH-7/C190 cells. In fact, the Ikappa B-alpha inhibitor of HuH-7 and HuH-7/C190 cells was unresponsive to LT-alpha 1beta 2 stimulation (Fig. 6A). Interestingly, compared to what occurred in their parental cells, the degradation of Ikappa B-beta inhibitor was enhanced and/or sustained in both LT-alpha 1beta 2-stimulated core-producing cells of HeLa and HuH-7 but with different kinetics. For LT-alpha 1beta 2-treated HeLa/C190 cells, the Ikappa B-beta degradation occurred within a 0.5- to 1-h time interval, while for HuH-7/C190 cells, it occurred at a 0.5- to 2-h interval (Fig. 6B). Furthermore, similar to the case of Ikappa B-alpha , the Ikappa B-beta protein in HeLa cells was unresponsive to stimulation with LT-alpha 1beta 2 (Fig. 6B). However, a slight depletion of Ikappa B-beta was observed in LT-alpha 1beta 2-treated (0.5 to 1 h) HuH-7 cells (Fig. 6B).


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  		FIG. 6.   Degradation of Ikappa B proteins in various LT-alpha 1beta 2- or TNF-alpha -stimulated HCV core protein-producing cells. Cells were stimulated with 500 ng of LT-alpha 1beta 2 ligand/ml (panels A and B) or 20 ng of TNF-alpha /ml (panels C and D) and at various time intervals (2 min to 8 h), the total cell extracts were prepared and portions of cell lysates (40 µg of protein each) were examined for the expression level of Ikappa B-alpha or Ikappa B-beta protein by using rabbit polyclonal antibody against human Ikappa B-alpha or Ikappa B-beta (Santa Cruz) and ECL detection system.

In TNF-alpha -treated cells, as expected, Ikappa B-alpha had a rapid turnover in all cells examined (Fig. 6C). However, the resynthesis of Ikappa B-alpha in both core-producing cells after TNF-alpha treatment was initiated earlier (30 min) than that of parental cells (Fig. 6C). Notably, the degradation of Ikappa B-beta was induced in both HuH-7 and HuH-7/C190 cells throughout the period (0.5 to 8 h) of treatment with TNF-alpha (Fig. 6D). For example, the degradative turnover of Ikappa B-beta in HuH-7/C190 prolonged and lasted at least 4 h before the resynthesis of this inhibitor occurred, and the level did not return to the basal one even after 8 h of treatment. In the TNF-alpha -treated HuH-7 cells, the Ikappa B-beta level was also reduced for at least 8 h but reached a minimum level after 1 h of treatment (Fig. 6D). Additionally, relative to HeLa cells, an enhancement of Ikappa B-beta breakdown was also observed with TNF-alpha -treated (1 or 4 h) HeLa/C190 cells (Fig. 6D).

Altogether, our results suggested that the degradation of Ikappa B (and in particular Ikappa B-beta ), may contribute to the enhancement of the NF-kappa B activity in cytokine-treated core-producing cells of HeLa and HuH-7. As for the role of Ikappa B-alpha degradation in core-mediated NF-kappa B activation, it seems more restricted on certain cytokines and cell lines we examined.

HCV core protein does not potentiate the TNF-alpha or LT-alpha 1beta 2-stimulated JNK activity of HeLa and HuH-7 cells. Since in addition to NF-kappa B activation, both cytokine treatments also lead to JNK activation (21, 41), we carried out experiments to determine whether the triggering of JNK activity by the cytokines was also modulated by the HCV core protein. Cytoplasmic extracts from uninduced or cytokine-treated cells were assayed for JNK activity through the immunocomplex kinase method using glutathione S-transferase-C-Jun1-79 as the substrate (14). The results indicated that although TNF-alpha (10 ng/ml) could induce a strong transient response (after 10 to 30 min) of JNK activation (maximum of eight- to ninefold in HeLa or HeLa/C190 cells and three- to fourfold in HuH-7 or HuH-7/C190 cells), the presence of HCV core protein in both HeLa and HuH-7 cells did not show any modulatory effect on JNK activation (data not shown). In the LT-alpha 1beta 2-treated cells (500 ng/ml), the cytokine-induced JNK activity was weaker than the response induced by TNF-alpha (maximum of 3- to fivefold in LT-alpha 1beta 2-treated HeLa and HeLa/C190 cells; less than twofold in LT-alpha 1beta 2-treated HuH-7 and HuH-7/C190 cells) (data not shown). Moreover, the core protein either had no effect (HuH-7/C190 cells) or slightly downregulated the LT-alpha 1beta 2-induced JNK activity (HeLa/C190 cells) (data not shown). Therefore, our results suggested that unlike in NF-kappa B activation, the HCV core protein does not potentiate JNK activation stimulated by both cytokines.

Discussion. In this study, we analyzed the mechanisms and kinetics of LT-alpha 1beta 2-stimulated NF-kappa B activation in comparison to those of TNF-alpha . Additionally, the NF-kappa B signal pathways of these two stimuli in HCV core protein-producing cells (HeLa/C190 and HuH-7/C190) were also parallel to those of their parental cells. An interesting phenomenon was noted in this study. It appears that varying patterns of NF-kappa B potentiation (in regard to the kinetics of NF-kappa B activation, NF-kappa B nuclear translocation, or Ikappa B degradation) between cell lines and stimuli were observed. These results suggest that the complexity of NF-kappa B signaling pathway triggering by either stimulus and presumably the different cell type-specific pathways are responsible for this phenomenon, as has been previously noted for both the TNF-alpha and the LT-alpha 1beta 2 system (4, 62). Despite this, our results clearly demonstrate that following either stimulus, in both cell lines expressing HCV core protein the Ikappa B-beta steady-state level substantially declined in parallel with the increase of NF-kappa B-DNA binding activity and the nuclear translocation of the p65 and p50 NF-kappa B species (Fig. 1, 2, 5, and 6). However, unlike that observed with Ikappa B-beta , the increase in Ikappa B-alpha turnover appeared only in LT-alpha 1beta 2-stimulated HeLa/C190 cells; in HuH-7 cells with or without the HCV core protein, the LT-alpha 1beta 2 ligand failed to stimulate Ikappa B-alpha turnover, and no apparent enhancement of Ikappa B-alpha degradation was found in TNF-alpha -triggering core-producing cells relative to the level in parental cells (Fig. 6). Our results also indicated that unlike the p50 and p65 members, the nuclear translocation of p52 is inert to both cytokine stimuli (Fig. 5) and may be irrelevant to the mechanism of NF-kappa B activation by these agents. These findings suggest that the enhancement of NF-kappa B-dependent transcriptional activity following cytokine stimulation in both core-producing cells (Fig. 3) may be mediated by a complex mechanism involving the deregulation of various cytoplasmic inhibitors of NF-kappa B, which may differ between the stimuli and the cell lines.

Ikappa B-alpha and Ikappa B-beta , encoded by separate genes, contain various numbers of ankyrin repeats, which bind to and inactivate p65 and C-Rel with slightly different affinities (10, 98, 106). In contrast to that of Ikappa B-alpha , Ikappa B-beta degradation occurs with slow kinetics and that degradation occurs only in cells stimulated with certain inducers, such as the bacterial LPS and IL-1 (99), although the degradation of Ikappa B-beta in TNF-alpha -stimulated or TNF-alpha - and gamma interferon-costimulated endothelial cells was also reported (23, 48). Moreover, since the expression of the Ikappa B-beta gene, unlike Ikappa B-alpha , appears not to be induced by NF-kappa B, the depleted Ikappa B-beta protein cannot be rapidly replenished through de novo protein synthesis (99). Thus, breakdown of Ikappa B-beta is generally associated with persistent activation of NF-kappa B. In our detection system, Ikappa B-beta , and to a lesser extent Ikappa B-alpha , is likely to be the major determinant that mediates the effects of HCV core protein on NF-kappa B activation. Interestingly, the dual specificity of HCV core protein for Ikappa B-alpha and Ikappa B-beta in NF-kappa B activation is closely analogous to that described for Tax-induced NF-kappa B activation (35, 54, 66).

Despite the apparent functional interplay between the HCV core protein and NF-kappa B, the underlying mechanism by which this viral protein accesses host signaling pathways for Ikappa B-beta or Ikappa B-alpha inactivation has remained elusive. Several possibilities may account for this phenomenon. First, in view of the facts that the HCV core protein physically associates with cytoplasmic domains of TNFRI and LT-beta R (21, 65, 113) and that these two receptors signaling NF-kappa B activation are mediated by receptor-association factors such as TRADD and TRAF family proteins (7, 34, 45, 46, 69, 71, 97, 102), the core protein may modulate the interaction of receptor with its cell-associated factors, accordingly enhancing the process of NF-kappa B induction. A typical example of this possibility is the LMP1 protein of Epstein-Barr virus, which activates NF-kappa B through association with TRADD and TRAF molecules (47, 69, 85). Second, the core protein may directly associate with the NF-kappa B or Ikappa B inhibitor, which then disrupts its association or affects its stability and phosphorylation, thus contributing to both basal and cytokine-stimulated NF-kappa B activation. This possibility is reminiscent of recent studies with the Tax protein of HTLV-1, which have revealed that NF-kappa B activation by Tax acts through its physical interaction with p100, p105, and p50 subunits or p65/p50- and p65/C-Rel-bound DNA complex (13, 16, 42, 43, 94-96). An alternative view is that HCV core protein may physically associate with or activate host kinases that differentially phosphorylate Ikappa B-alpha or Ikappa B-beta and that phosphorylation targets Ikappa B for degradation by proteasome. This suggestion is rather attractive, since recently candidate kinases, such as Ikappa B kinase, IKKalpha and IKKbeta , have been shown to differ in their phosphorylation efficiencies between Ikappa B-alpha and Ikappa B-beta inhibitory proteins (32, 78, 90), and their kinase activities are also differentially regulated by upstream kinases (72), thereby providing variations on the common theme of signal-regulated Ikappa B phosphorylation, which may explain the cell-type- or cytokine-specific Ikappa B inactivation by the HCV core protein. Along this line is the more recent finding (26, 112) that Tax-mediated NF-kappa B activation results from direct interaction of Tax and MEKK1 or IKK-alpha /beta , components of the Ikappa B kinase complex, leading to predominantly enhanced phosphorylation of Ikappa B-alpha , which strongly supports this view. Notably, it seems that these possible activation mechanisms of NF-kappa B are not mutually exclusive, at least in the case of Tax-mediated NF-kappa B activation. It will thus be interesting to find out whether this feature is also applicable to the core protein of HCV.

In this study, we also found evidence that the core protein of HCV apparently did not have a significant effect on JNK pathway triggering by TNF-alpha or LT-alpha 1beta 2 (data not shown). Since both JNK and NF-kappa B activation share some common signaling molecules, such as MEKK1 or TRAF2 (44, 58, 67, 79, 89), one may argue that these two common modulators may not be the target for core protein-mediated NF-kappa B activation. However, judging from the complexity or divergence of these two intracellular pathways that are regulated by a network of kinases, it is still too early to formally exclude the involvement of MEKK1 or TRAF2 in core-mediated NF-kappa B activation.

This work together with our previous study (21) strongly suggests that, with regard to three signaling pathways triggered by TNF-alpha and LT-alpha 1beta 2, in HeLa cells the direct association of LT-beta R with HCV core protein modulates the NF-kappa B and cytolytic pathways of LT-beta R/LT-alpha 1beta 2 as opposed to that of TNF-alpha , where the core protein modulates only its NF-kappa B activation pathway. However, in HuH-7 cells the core protein potentiates only the NF-kappa B signal pathway but not the cytolytic activity or JNK pathway of both cytokines. Our results therefore imply that the HCV core protein may deregulate NF-kappa B activation triggering by TNF-related cytokines in most cell types. Moreover, it appears that in HeLa cells the HCV core protein has a plethoric effect on LT-beta R/LT-alpha 1beta 2 signaling relative to that of TNF-alpha , even though core protein associates with the cytoplasmic domains of both receptors. This differential effect on the cytokine-induced biological activities exerted by the core protein may reflect the distinct nature of each receptor's signaling pathway. Additionally, a more general effect by the core protein on NF-kappa B signaling but not on the cytolytic activity of both receptors is in accordance with the effect of their signaling on the cytolytic activity relative to NF-kappa B activation being probably more diverged downstream following the receptor engagement. Supporting this view are the findings which indicate that in NF-kappa B activation, both receptors share the same adapter molecule, such as TRAF2 and TRAF5 (2, 7, 22, 45, 71, 81), which may serve as the common target for core protein in eliciting its effect on cytokine-induced NF-kappa B signaling. On the other hand, these two receptors are differentiated by having a death domain in TNFRI and lacking it in LT-beta R, which then identifies the death signaling of TNFRI as the Fas-like pathway (7, 45, 46, 70) and that of LT-beta R as TRAF mediated (34, 102). Additionally, emerging evidence shows that there are discrepancies in the core-mediated effect on TNF-alpha -stimulated cytolytic activity or NF-kappa B activation, where core protein has been shown to have the opposite effect or no effect, depending on the cell type (21, 76, 113). In light of the pleiotropic nature of HCV core protein and the complication of signaling molecules involved in cell death or NF-kappa B activation elicited by TNF-alpha , these discrepancies likely stem from the different intracellular milieus used for examination. Therefore, these findings emphasize the importance of the signaling context in determining the consequence of TNF-alpha or other cytokine signaling.

In the present study, we demonstrate that like other viruses, HCV adopts its core protein to subvert the NF-kappa B/Ikappa B autoregulatory pathway. Of particular interest and relevant to the HCV pathogenesis is the outcome of this deregulation. Since the lists of target genes for NF-kappa B transcriptional factor include both pro-apoptotic and anti-apoptotic genes, the role of NF-kappa B as a promoter or attenuator of cell death may ultimately depend upon both the cell type and the nature of the stimulus (reviewed in references 4, 6, and 106). In different cell types, NF-kappa B may perform opposite functions by activating distinct patterns of genes in conjuction with cell-type-specific transcriptional factors. Moreover, different stimuli may elicit distinct signaling pathways in addition to the ones controlling cytolytic activity and NF-kappa B. Apart from the NF-kappa B transcriptional factor, additional transcriptional factors may further influence the spectrum of induced genes to determine whether NF-kappa B can induce or protect against cell death. In view of these considerations, it appears that the role of NF-kappa B is determined by a set of genes that it can access in a given cell type. Conceivably, the consequences of NF-kappa B activation vary considerably among cell types and stimuli. Since in human hepatoma HuH-7 cells, NF-kappa B activation but not cytolytic activity is potentiated by TNF-alpha or LT-alpha 1beta 2 (reference 21 and this work), we are inclined to believe that the biological significance of core-mediated upregulation of NF-kappa B lies in its ability to deliver a survival signal and thus allow persistence of HCV in a long-lived cell compartment, thereby establishing a chronic, activated state of HCV infection. If this conjecture is correct, the feature of HCV core protein then is very similar to that of the Tax protein in establishing the chronic state of viral infection (35, 54, 66, 92). Furthermore, since both TNF-alpha /TNFRI and LT-alpha 1beta 2/LT-beta R signaling play pivotal roles in a wide range of cellular functions, including immunoregulatory responses, proliferation, differentiation, and immune organ development (1, 4, 5, 31, 33, 63, 106, 108), the association of core protein with these two sets of receptor may have a detrimental effect on these biological functions, which may, at least in part, account for the role of core protein in HCV pathogenesis.


    ACKNOWLEDGMENTS

We are very grateful to J. L. Browning for providing recombinant LT-alpha 1beta 2, H. Wajant for providing luciferase reporter plasmid NF-kappa B-fosp-1783:3.2Luc, and L.-H. Hwang for providing HeLa/C190 and HuH-7/C190 cells.

This work was supported by grant NSC87-2315-B010-001MH from the National Science Council and in part by grant DOH87-HR-502 from the National Health Research Institute of the Republic of China to Y.-H.W.L.


    FOOTNOTES

* Corresponding author. Mailing address: Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan 112. Phone: 886-2-2826-7124. Fax: 886-2-2826-4843. E-mail: yhwulee{at}ym.edu.tw.


    REFERENCES
Top
Abstract
Text
References

1. Aggarwal, B. B., and K. Natarajan. 1996. Tumor necrosis factors: developments during the last decade. Eur. Cytokine Netw. 7:93-124[Medline].
2. Arizawa, S., I. Scheffrahn, G. Mosialos, H. Brand, J. Duyster, K. Kaye, J. Harada, B. Dougall, G. Hubinger, E. Kieff, F. Herrmann, A. Leutz, and H. J. Gruss. 1997. Tumor necrosis factor receptor-associated factor (TRAF) 5 and TRAF2 are involved in CD30-mediated NF-kappa B activation. J. Biol. Chem. 272:2042-2045[Abstract/Free Full Text].
3. Baens, M., M. Chaffanet, J. J. Cassiman, H. Den Berghe, and P. Marynen. 1993. Construction and evaluation of a HNcDNA library of human 12p transcribed sequences derived from a somatic cell hybrid. Genomics 16:214-218[Medline].
4. Baeuerle, P. A., and D. Baltimore. 1996. NF-kappa B: ten years after. Cell 87:13-20[Medline].
5. Baeuerle, P. A., and T. Henkel. 1994. Function and activation of NF-kappa B in the immune system. Annu. Rev. Immunol. 12:141-179[Medline].
6. Baichwal, V. R., and P. A. Baeuerle. 1997. Apoptosis: activate NF-kappa B or die? Curr. Biol. 7:R94-R96[Medline].
7. Baker, S. J., and E. P. Reddy. 1996. Transducers of life and death: TNF receptor superfamily and associated protein. Oncogene 12:1-9[Medline].
8. Baldwin, J. A. S. 1996. The NF-kappa B and Ikappa B proteins: new discoveries and insights. Annu. Rev. Immunol. 14:649-681[Medline].
9. Barba, G., F. Harper, T. Harada, M. Kohara, S. Goulinet, Y. Matsuura, G. Eder, Z. Schaff, M. J. Chapman, T. Miyamura, and C. Brechot. 1997. Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets. Proc. Natl. Acad. Sci. USA 94:1200-1205[Abstract/Free Full Text].
10. Bartenschlager, R., L. Ahlborn-Laake, J. Mous, and H. Jacobsen. 1993. Nonstructural protein 3 of the hepatitis C virus encodes a serine-type proteinase required for cleavage at the NS3/4 and NS4/5 junctions. J. Virol. 67:3835-3844[Abstract/Free Full Text].
11. Battegay, M., J. Fikes, A. M. DiBisceglie, P. A. Wentworth, A. Sette, E. Celis, W.-M. Ching, A. Grakoui, C. M. Rice, K. Kurokohchi, J. A. Berzofsky, J. H. Hoofnagle, S. M. Feinstone, and T. Akatsuka. 1995. Patients with chronic hepatitis C have circulating cytotoxic T cells which recognize hepatitis C virus-encoded peptides binding to HLA-A2.1 molecules. J. Virol. 69:2462-2470[Abstract].
12. Beg, A. A., and D. Baltimore. 1996. An essential role for NF-kappa B in preventing TNF-alpha -induced cell death. Science 274:782-784[Abstract/Free Full Text].
13. Béraud, C., S.-C. Sun, P. Ganchi, D. W. Ballard, and W. C. Greene. 1994. Human T-cell leukemia virus type I Tax associates with and is negatively regulated by the NF-kappa B2 p100 gene product: implications for viral latency. Mol. Cell. Biol. 14:1374-1382[Abstract/Free Full Text].
14. Berberich, I., G. Shu, F. Siebelt, J. R. Woodgett, J. M. Kyriakis, and E. A. Clark. 1996. Cross-linking CD40 on B cells preferentially induces stress-activated protein kinases rather than mitogen-activated protein kinases. EMBO J. 15:92-101[Medline].
15. Beutler, B., and C. van Huffel. 1994. Unraveling functions in the TNF ligand and receptor families. Science 264:667-668[Free Full Text].
16. Bex, F., A. McDowail, A. Burny, and R. Gaynor. 1997. The human T-cell leukemia virus type 1 transactivator protein Tax colocalizes in unique nuclear structures with NF-kappa B proteins. J. Virol. 71:3484-3497[Abstract].
17. Browning, J. L., K. Miatkowski, D. A. Griffiths, P. R. Bourdon, C. Hession, C. M. Ambrose, and W. Meier. 1996. Preparation and characterization of soluble recombinant heterotrimeric complexes of human lymphotoxins alpha  and beta . J. Biol. Chem. 271:8616-8626.
18. Browning, J. L., K. Miatkowski, I. Sizing, D. Griffiths, M. Zafari, C. D. Benjamin, W. Meier, and F. Mackay. 1996. Signaling through the lymphotoxin beta  receptor induces the death of some adenocarcinoma tumor lines. J. Exp. Med. 183:867-878[Abstract/Free Full Text].
19. Bruix, J., J. M. Barrera, X. Calvet, G. Ercilla, J. Costa, J. M. Sanchez-Tapias, M. Ventura, M. Vall, M. Bruguera, C. Bru, R. Castillo, and J. Rodes. 1989. Prevalence of antibodies to hepatitis C virus in Spanish patients with hepatocellular carcinoma and hepatic cirrhosis. Lancet ii:1004-1006.
20. Cerny, A., J. G. McHutchison, C. Pasquinelli, M. E. Brown, M. A. Brothers, B. Grabscheid, P. Fowler, M. Houghton, and F. V. Chisari. 1995. Cytotoxic T lymphocyte response to hepatitis C virus-derived peptides containing the HLA A2.1 binding motif. J. Clin. Investig. 95:521-530.
21. Chen, C.-M., L.-R. You, L.-H. Hwang, and Y.-H. W. Lee. 1997. Direct interaction of hepatitis C virus core protein with the cellular lymphotoxin-beta receptor modulates the signal pathway of the lymphotoxin-beta receptor. J. Virol. 71:9417-9426[Abstract].
22. Chen, C.-M., Y.-H. W. Lee, H. Wajant, and M. Grell. Identification of the signal transducing region of the lymphotoxin-beta receptor (LT-beta R) coupling to TRAF2-dependent activation of NF-kappa B and c-Jun N-terminal kinase. Submitted for publication.
23. Cheshire, J. L., and J. A. S. Baldwin. 1997. Synergistic activation of NF-kappa B by tumor necrosis factor alpha and gamma interferon via enhanced Ikappa Balpha degradation and de novo Ikappa Bbeta degradation. Mol. Cell. Biol. 17:6746-6754[Abstract].
24. Chirillo, P., M. Falco, P. L. Puri, M. Artini, C. Balsano, M. Levrero, and G. Natoli. 1996. Hepatitis B virus pX activates NF-kappa B-dependent transcription through a Raf-independent pathway. J. Virol. 70:641-646[Abstract].
25. Choo, Q.-L., G. Kuo, A. J. Weiner, L. R. Overby, D. W. Bradley, and M. Houghton. 1989. Isolation of a cDNA clone derived from a blood-borne non-A, non-B viral hepatitis genome. Science 244:359-362[Abstract/Free Full Text].
26. Chu, Z. L., J. A. DiDonato, J. Hawiger, and D. W. Ballard. 1998. The Tax oncoprotein of human T-cell leukemia virus type 1 associates with and persistently activates Ikappa B kinases containing IKKalpha and IKKbeta . J. Biol. Chem. 273:15891-15894[Abstract/Free Full Text].
27. Coso, O. A., M. Chiarello, J.-C. Yu, H. Teramoto, P. Crespo, N. Xu, T. Miki, and J. S. Gutkind. 1995. The small GTP-binding proteins rac1 and cdc42 regulate the activity of the JNK/SAPK pathway. Cell 81:1137-1146[Medline].
28. Crowe, P. D., T. L. VanArsdale, B. N. Walter, C. F. Ware, C. Hession, B. Ehrenfels, J. L. Browning, W. S. Din, R. G. Goodwin, and C. A. Smith. 1994. A lymphotoxin-beta -specific receptor. Science 264:707-710[Abstract/Free Full Text].
29. Derijard, B., M. Hibi, I.-H. Wu, T. Barrett, B. Su, T. Deng, M. Karin, and R. J. Davis. 1994. JNK1: a protein kinase stimulated by UV light and Ha-ras that binds and phosphorylates the c-Jun activation domain. Cell 76:1025-1037[Medline].
30. Derijard, B., J. Raingeaud, T. Barrett, I.-H. Wu, J. Han, R. J. Ulevitch, and R. J. Davis. 1995. Independent human MAP kinase signal transduction pathways defined by MEK and MKK isoforms. Science 267:682-685[Abstract/Free Full Text].
31. De Togni, P., J. Goellner, N. H. Ruddle, P. R. Streeter, A. Fick, S. Mariathasan, S. C. Smith, R. Carlson, L. P. Shornick, J. Strauss-Schoenberger, J. H. Russell, R. Karr, and D. D. Chaplin. 1994. Abnormal development of peripheral lymphoid organs in mice deficient in lymphotoxin. Science 264:703-707[Abstract/Free Full Text].
32. DiDonato, J. A., M. Hayakawa, D. M. Rothwarf, E. Zandi, and M. Karin. 1997. A cytokine-responsive Ikappa B kinase that activates the transcription factor NF-kappa B. Nature 388:548-554[Medline].
33. Ettinger, R., J. L. Browning, S. A. Michie, W. van Ewijk, and H. O. McDevitt. 1996. Disrupted spenic architecture, but normal lymph node development in mice expressing a soluble lymphotoxin-beta receptor-IgG1 fusion protein. Proc. Natl. Acad. Sci. USA 93:13102-13107[Abstract/Free Full Text].
34. Force, W. R., T. C. Cheung, and C. F. Ware. 1997. Dominant negative mutants of TRAF3 reveal an important role for the coiled coil domains in cell death signaling by the lymphotoxin-beta receptor. J. Biol. Chem. 272:30835-30840[Abstract/Free Full Text].
35. Good, L., and S.-C. Sun. 1996. Persistent activation of NF-kappa B/Rel by human T-cell leukemia virus type 1 Tax involves degradation of Ikappa Bbeta . J. Virol. 70:2730-2735[Abstract].
36. Gooding, L. R. 1992. Virus proteins that counteract host immune defenses. Cell 71:5-7[Medline].
37. Grakoui, A., D. W. McCourt, C. Wychowski, S. M. Feinstone, and C. M. Rice. 1993. Characterization of the hepatitis C virus-encoded serine proteinase: determination of proteinase-dependent polyprotein cleavage sites. J. Virol. 67:2832-2843[Abstract/Free Full Text].
38. Gupta, S., D. Campbell, B. Derijard, and R. J. Davis. 1995. Transcription factor ATF2 regulation by the JNK signal transduction pathway. Science 267:389-393[Abstract/Free Full Text].
39. Heller, R. A., and M. Kronk. 1994. Tumor necrosis factor-mediated signaling pathways. J. Cell Biol. 126:5-9[Free Full Text].
40. Herrero, J. A., P. Mathew, and C. V. Paya. 1995. LMP-1 activates NF-kappa B by targeting the inhibitory molecule Ikappa Balpha . J. Virol. 69:2168-2174[Abstract].
41. Hibi, M., A. Lin, T. Smeal, A. Minden, and M. Karin. 1993. Identification of an oncoprotein- and UV-responsive protein kinase that binds and potentiates the c-Jun activation domain. Genes Dev. 7:2135-2148[Abstract/Free Full Text].
42. Hirai, H., J. Fujisawa, T. Suzuki, K. Ueda, M. Muramatsu, A. Tsuboi, N. Arai, and M. Yoshida. 1992. Transcriptional activator Tax of HTLV-1 binds to the NF-kappa B precursor p105. Oncogene 7:1737-1742[Medline].
43. Hirai, H., J. Fujisawa, T. Suzuki, J.-I. Fujisawa, J.-I. Inoue, and M. Yoshida. 1994. Tax protein of human T-cell leukemia virus type I binds to the ankyrin motifs of inhibitory factor kappa B and induces nuclear translocation of transcription factor NF-kappa B proteins for transcriptional activation. Proc. Natl. Acad. Sci. USA 91:3584-3588[Abstract/Free Full Text].
44. Hirano, M., S. Osada, T. Aoki, S. Hirai, M. Hosaka, J. Inoue, and S. Ohno. 1996. MEK kinase is involved in tumor necrosis factor alpha -induced NF-kappa B activation and degradation of Ikappa B-alpha . J. Biol. Chem. 271:13234-13238[Abstract/Free Full Text].
45. Hsu, H., H.-B. Shu, M.-G. Pan, and D. Goeddel. 1996. TRADD-TRAF2 and TRADD-FADD interaction define two distinct TNF receptor 1 signal transduction pathways. Cell 84:299-308[Medline].
46. Hsu, H., J. Xiong, and D. Goeddel. 1995. The TNF receptor 1-associated protein TRADD signals cell death and NF-kappa B activation. Cell 81:495-504[Medline].
47. Izumi, K. M., and E. D. Kieff. 1997. The Epstein-Barr virus oncogene product latent membrane protein 1 engages the tumor necrosis factor receptor-associated death domain protein to mediate B lymphocyte growth transformation and activate NF-kappa B. Proc. Natl. Acad. Sci. USA 94:12592-12597[Abstract/Free Full Text].
48. Johnson, D. R., I. Douglas, A. Jahnke, S. Ghosh, and J. S. Pober. 1996. A sustained reduction in Ikappa B-beta may contribute to persistent NF-kappa B activation in human endothelial cells. J. Biol. Chem. 271:16317-16322[Abstract/Free Full Text].
49. Karin, M. 1995. The regulation of AP-1 activity by mitogen-activated protein kinases. J. Biol. Chem. 270:16483-16486[Free Full Text].
50. Koziel, M. J., D. Dudley, N. Afdhal, Q. L. Choo, M. Houghton, R. Ralston, and B. D. Walker. 1993. Hepatitis C virus (HCV)-specific cytotoxic T lymphocytes recognize epitopes in the core and envelope proteins of HCV. J. Virol. 67:7522-7532[Abstract/Free Full Text].
51. Kuo, G., Q.-L. Choo, H. J. Alter, G. L. Gitnick, A. G. Redeker, R. H. Purcell, T. Miyamura, L. Dienstag, M. J. Alter, C. E. Stevens, G. E. Tegtmeier, F. Bonino, M. Colombo, W.-S. Lee, C. Kuo, K. Berger, J. R. Shuster, L. R. Overby, D. W. Bradely, and M. Houghton. 1989. An assay for circulating antibodies to a major etiologic virus of human non-A, non-B hepatitis. Science 244:362-364[Abstract/Free Full Text].
52. Kyriakis, J. M., and J. Avruch. 1996. Sounding the alarm: protein kinase cascades activated by stress and inflammation. J. Biol. Chem. 271:24313-24316[Free Full Text].
53. Kyriakis, J. M., P. Banerjee, E. Nikolaki, T. Dai, E. A. Ruble, M. F. Ahmad, J. Avruch, and J. R. Woodgett. 1994. The stress-activated protein kinase subfamily of c-Jun kinases. Nature 369:156-160[Medline].
54. Lacoste, J., L. Petropoulos, N. Pepin, and J. Hiscott. 1995. Constitutive phosphorylation and turn over of Ikappa Balpha in human T-cell leukemia virus type I-infected and Tax-expressing T cells. J. Virol. 69:564-569[Abstract].
55. Laemmli, U. K. 1970. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227:680-685[Medline].
56. Lange-Carter, C. A., C. M. Pleiman, A. M. Gardner, K. J. Blumer, and G. L. Johnson. 1993. A divergence in the MAP kinase regulatory network defined by MEK kinase and Raf. Science 260:315-319[Abstract/Free Full Text].
57. LeBail, O., R. Schmidt-Ulrich, and A. Israel. 1993. Promoter analysis of the gene encoding the Ikappa Balpha /MAD3 inhibitor of NF-kappa B: positive regulation by members of the rel/NF-kappa B family. EMBO J. 12:5043-5049[Medline].
58. Lee, F. S., J. Hagler, Z. J. Chen, and T. Maniatis. 1997. Activation of the Ikappa Balpha kinase complex by MEKK1, a kinase of the JNK pathway. Cell 88:213-222[Medline].
59. Lin, C., B. D. Lindenbach, B. M. Pragai, D. W. McCourt, and C. M. Rice. 1994. Processing in the hepatitis C virus E2-NS2 region: identification of p7 and two distinct E2-specific products with different C termini. J. Virol. 68:5063-5073[Abstract/Free Full Text].
60. Liu, Z.-G., H. Hsu, D. Goeddel, and M. Karin. 1996. Dissection of TNF receptor 1 effector functions: JNK activation is not linked to apoptosis while NF-kappa B activation prevents cell death. Cell 87:565-576[Medline].
61. Lo, S.-Y., F. Masiarz, S. B. Hwang, M. M. C. Lai, and J.-H. Ou. 1995. Differential subcellular localization of hepatitis C virus core gene products. Virology 213:455-461[Medline].
62. Mackay, F., G. R. Majeau, P. S. Hochman, and J. L. Browning. 1996. Lymphotoxin beta  receptor triggering induces activation of the nuclear factor kappa B transcription factor in some cell types. J. Biol. Chem. 271:24934-24938[Abstract/Free Full Text].
63. Mackay, F., G. R. Majeau, P. Lawton, P. S. Hochman, and J. L. Browning. 1997. Lymphotoxin but not tumor necrosis factor functions to maintain spenic architecture and humoral responsiveness in adult mice. Eur. J. Immunol. 27:2033-2042[Medline].
64. Maniatis, T. 1997. Catalysis by a multiprotein Ikappa B kinase complex. Science 278:818-819[Free Full Text].
65. Matsumoto, M., T.-Y. Hsieh, N. Zhu, T. Vanarsdale, S. B. Hwang, K.-S. Jeng, A. E. Gorbalenya, S.-Y. Lo, J.-H. Ou, C. F. Ware, and M. M. Lai. 1997. Hepatitis C virus core protein interacts with the cytoplasmic tail of lymphotoxin-beta receptor. J. Virol. 71:1301-1309[Abstract].
66. McKinsey, T. A., J. A. Brockman, D. C. Scherer, S. W. Al-Murrani, P. Green, and D. W. Ballard. 1996. Inactivation of Ikappa Bbeta by the Tax protein of human T-cell leukemia virus type 1: a potential mechanism for constitutive induction of NF-kappa B. Mol. Cell. Biol. 16:2083-2090[Abstract].
67. Meyer, C. F., X. Wang, C. Chang, D. Templeton, and T.-H. Tan. 1996. Interaction between C-Rel and the mitogen-activated protein kinase kinase kinase 1 signaling cascade in mediating kappa B enhancer activation. J. Biol. Chem. 271:8971-8976[Abstract/Free Full Text].
68. Minden, A., A. Lin, F.-X. Claret, A. Abo, and M. Karin. 1995. Selective activation of the JNK-signaling cascade and c-Jun transcriptional activity by the small GTPases Rac and Cdc42Hs. Cell 81:1147-1157[Medline].
69. Mosialos, G., M. Birkenbach, R. Yalamanchili, T. VanArsdale, C. F. Ware, and E. Kieff. 1995. The Epstein-Barr virus transforming protein LMP1 engages signaling proteins for the tumor necrosis factor receptor family. Cell 80:389-399[Medline].
70. Nagata, S. 1997. Apoptosis by death factor. Cell 88:355-365[Medline].
71. Nakano, H., H. Oshima, W. Chung, L. Williams-Abott, C. F. Ware, H. Yagita, and K. Okumura. 1996. TRAF5, an activator of NF-kappa B and putative signal transducer for the lymphotoxin-beta receptor. J. Biol. Chem. 271:14661-14664[Abstract/Free Full Text].
72. Nakano, H., M. Shindo, S. Sakon, S. Nishinaka, M. Mihara, H. Yagita, and K. Okumura. 1998. Differential regulation of Ikappa B kinase alpha  and beta  by two upstream kinases, NF-kappa B-inducing kinase and mitogen-activated protein kinase/ERK kinase kinase-1. Proc. Natl. Acad. Sci. USA 95:3537-3542[Abstract/Free Full Text].
73. Ray, R. B., L. M. Lagging, K. Meyer, R. Steele, and R. Ray. 1995. Transcriptional regulation of cellular and viral promoters by the hepatitis C virus core protein. Virus Res. 37:209-220[Medline].
74. Ray, R. B., L. M. Lagging, K. Meyer, R. Steele, and R. Ray. 1996. Hepatitis C virus core protein cooperates with ras and transforms primary rat embryo fibroblasts to tumorigenic phenotype. J. Virol. 70:4438-4443[Abstract].
75. Ray, R. B., K. Meyer, and R. Ray. 1996. Suppression of apoptotic cell death by hepatitis C virus core protein. Virology 226:176-182[Medline].
76. Ray, R. B., K. Meyer, A. Shrivastava, B. B. Aggarwaland, and R. Ray. 1998. Inhibition of tumor necrosis factor (TNF-alpha)-mediated apoptosis by hepatitis C virus core protein. J. Biol. Chem. 273:2256-2259[Abstract/Free Full Text].
77. Ray, R. B., R. Steele, K. Meyer, and R. Ray. 1997. Transcriptional repression of p53 promoter by hepatitis C virus core protein. J. Biol. Chem. 272:10983-10986[Abstract/Free Full Text].
78. Regnier, C. H., H. Y. Song, X. Gao, D. V. Goeddel, Z. Cao, and M. Rothe. 1997. Identification and characterization of an Ikappa B kinase. Cell 90:373-383[Medline].
79. Reinhard, C., B. Shamoon, V. Shyamala, and L. T. Williams. 1997. Tumor necrosis factor alpha -induced activation of c-Jun N-terminal kinase is mediated by TRAF2. EMBO J. 16:1080-1092[Medline].
80. Rice, C. M., and C. M. Walker. 1995. Hepatitis C virus-specific T lymphocyte responses. Curr. Opin. Immunol. 7:532-538[Medline].
81. Rothe, M., V. Sarma, V. M. Dixit, and D. V. Goeddel. 1995. TRAF2-mediated activation of NF-kappa B by TNF receptor 2 and CD40. Science 269:1424-1427[Abstract/Free Full Text].
82. Ruggieri, A., T. Harada, Y. Matsuura, and T. Miyamura. 1997. Fas-mediated apoptosis by hepatitis C virus core protein. Virology 229:68-76[Medline].
83. Saito, I., T. Miyamura, A. Ohbayashi, H. Harada, S. Katayama, S. Kikuchi, Y. Watanabe, S. Koi, M. Onji, Q.-L. Choo, M. Houghton, and G. Kuo. 1990. Hepatitis C virus infection is associated with the development of hepatocellular carcinoma. Proc. Natl. Acad. Sci. USA 87:6547-6549[Abstract/Free Full Text].
84. Sanchez, I., R. T. Hughes, B. J. Mayer, K. Yee, J. R. Woodgett, J. Avruch, J. M. Kyriakis, and L. I. Zon. 1994. Role of SAPK/ERK kinase-1 in the stress-activated pathway regulating transcription factor c-Jun. Nature 372:794-798[Medline].
85. Sandberg, M., W. Hammerschmidt, and B. Sugden. 1997. Characterization of LMP-1's association with TRAF1, TRAF2, and TRAF3. J. Virol. 71:4649-4656[Abstract].
86. Santolini, E., G. Migliaccio, and N. L. Monica. 1994. Biosynthesis and biochemical properties of the hepatitis C virus core protein. J. Virol. 68:3631-3641[Abstract/Free Full Text].
87. Shih, C.-M., C.-M. Chen, S.-Y. Chen, and Y.-H. W. Lee. 1995. Modulation of the trans-suppression activity of hepatitis C virus core protein by phosphorylation. J. Virol. 69:1160-1171[Abstract].
88. Shih, C.-M., S. J. Lo, T. Miyamura, S.-Y. Chen, and Y.-H. W. Lee. 1993. Suppression of hepatitis B virus expression and replication by hepatitis C virus core protein in HuH-7 cells. J. Virol. 67:5823-5832[Abstract/Free Full Text].
89. Song, H. Y., C. H. Regnier, C. J. Kirschning, D. V. Goeddel, and M. Rothe. 1997. TNF-mediated kinase cascades: bifurcation of NF-kappa B and JNK/SAPK pathways at TRAF2. Proc. Natl. Acad. Sci. USA 94:9792-9796[Abstract/Free Full Text].
90. Stancovski, I., and D. Baltimore. 1997. NF-kappa B activation: the Ikappa B kinase revealed? Cell 91:299-302[Medline].
91. Su, F., and R. J. Schneider. 1996. Hepatitis B virus HBx protein activates transcription factor NF-kappa B by acting on multiple cytoplasmic inhibitor of rel-related proteins. J. Virol. 70:4558-4566[Abstract].
92. Sun, S.-C., J. Elwood, C. Beraud, and W. C. Greene. 1994. Human T-cell leukemia virus type 1 Tax activation of NF-kappa B/Rel involves phosphorylation and degradation of Ikappa Balpha and RelA (p65)-mediated induction of the c-rel gene. Mol. Cell. Biol. 14:7377-7384[Abstract/Free Full Text].
93. Sun, S. C., P. A. Ganchi, D. W. Ballard, and W. C. Greene. 1993. NF-kappa B controls expression of inhibitor Ikappa B-alpha : evidence for an inducible autoregulatory pathway. Science 259:1912-1915[Abstract/Free Full Text].
94. Suzuki, T., H. Hirai, J. Fujisawa, T. Fujita, and M. Yoshda. 1993. A trans-activator Tax of human T-cell leukemia virus type 1 binds to NF-kappa B p50 and serum response factor (SRF) and associates with enhancer DNAs of the NF-kappa B site and CArG box. Oncogene 8:2391-2397[Medline].
95. Suzuki, T., H. Hirai, T. Murakami, and M. Yoshda. 1995. Tax protein of HTLV-I destabilizes the complexes of NF-kappa B and Ikappa B-alpha and induces nuclear translocation of NF-kappa B for transcriptional activation. Oncogene 10:1199-1207[Medline].
96. Suzuki, T., H. Hirai, and M. Yoshda. 1994. Tax protein of HTLV-I interacts with the Rel homology domain of NF-kappa B p65 and C-Rel protein bound to the NF-kappa B binding site and activates transcription. Oncogene 9:3099-3105[Medline].
97. Tewari, M., and V. M. Dixit. 1996. Recent advances in tumor necrosis factor and CD40 signaling. Curr. Opin. Genet. Dev. 6:39-44[Medline].
98. Thanos, D., and T. Maniatis. 1995. NF-kappa B: a lesson in family values. Cell 80:529-532[Medline].
99. Thompson, J. E., R. J. Phillips, H. Erdjument-Bromage, P. Tempst, and S. Ghosh. 1995. Ikappa B-beta regulates the persistent response in a biphasic activation of NF-kappa B. Cell 80:573-582[Medline].
100. Tomei, L., C. Failla, E. Santolini, R. D. Francesco, and N. L. Monica. 1993. NS3 is a serine protease required for processing of hepatitis C virus polyprotein. J. Virol. 67:4017-4026[Abstract/Free Full Text].
101. Van Antwerp, D. J., S. J. Martin, T. Kafri, D. R. Green, and I. M. Verma. 1996. Suppression of TNF-alpha -induced apoptosis by NF-kappa B. Science 274:787-789[Abstract/Free Full Text].
102. VanArsdale, T. L., S. L. VanArsdale, W. Force, B. N. Walker, G. Mosialos, E. Kieff, J. C. Reed, and C. F. Ware. 1997. Lymphotoxin-beta receptor signaling complex: role of tumor necrosis factor-associated factor 3 recruitment in cell death and activation of nuclear factor kappa B. Proc. Natl. Acad. Sci. USA 94:2460-2465[Abstract/Free Full Text].
103. Vandenabeele, P., W. Declercq, R. Beyaert, and W. Fiers. 1995. Two tumor necrosis factor receptors: structure and function. Trends Cell Biol. 5:392-399. [Medline]
104. Verheij, M., R. Bose, X. H. Lin, B. Yao, W. D. Jarvis, S. Grant, M. J. Birrer, E. Szabo, L. I. Zon, J. M. Kyriakis, and R. N. Kolesnick. 1996. Requirement for ceramide-initiated SAPK/JNK signalling in stress-induced apoptosis. Nature 380:75-79[Medline].
105. Verma, I. M., and J. Stevenson. 1997. Ikappa B kinase: beginning, not the end. Proc. Natl. Acad. Sci. USA 94:11758-11760[Free Full Text].
106. Verma, I. M., J. K. Stevenson, E. M. Schwartz, D. Van Antwerp, and S. Miyamoto. 1995. Rel/NF-kappa B/Ikappa B family: intimate tales of association and dissociation. Genes Dev. 9:2723-2735[Free Full Text].
107. Wang, C.-Y., M. W. Mayo, and A. S. Baldwin. 1996. TNF- and cancer therapy-induced apoptosis: potentiation by inhibition of NF-kappa B. Science 274:784-787[Abstract/Free Full Text].
108. Ware, C. F., T. L. VanArsdale, P. D. Crowe, and J. L. Browning. 1995. The ligands and receptors of the lymphotoxin system. Curr. Top. Microbiol. Immunol. 198:175-218[Medline].
109. Whitmarsh, A. J., P. Shore, A. D. Sharrocks, and R. J. Davis. 1995. Integration of MAP kinase signal transduction pathways at the serum response element. Science 269:403-407[Abstract/Free Full Text].
110. Xia, Z., M. Dickens, J. Raingeaud, R. J. Davis, and M. E. Greenberg. 1996. Opposing effects of ERK and JNK-p38 MAP kinases on apoptosis. Science 270:1326-1331[Abstract/Free Full Text].
111. Yan, M., T. Dai, J. C. Deak, J. M. Kyriakis, L. I. Zon, J. R. Woodgett, and D. J. Templeton. 1994. Activation of stress-activated protein kinase by MEKK1 phosphorylation of its activator SEK1. Nature 372:798-800[Medline].
112. Yin, M.-J., L. B. Christerson, Y. Yamamoto, Y.-T. Kwak, S. Xu, F. Mercurio, M. Barbosa, M. H. Cobb, and R. B. Gaynor. 1998. HTLV-1 Tax protein binds to MEKK1 to stimulate Ikappa B kinase activity and NF-kappa B activation. Cell 93:875-884[Medline].
113. Zhu, N., A. Khoshnan, R. Schneider, M. Matsumoto, G. Dennert, C. Ware, and M. M. C. Lai. 1998. Hepatitis C virus core protein binds to the cytoplasmic domain of tumor necrosis factor (TNF) receptor 1 and enhances TNF-induced apoptosis. J. Virol. 72:3691-3697[Abstract/Free Full Text].

Journal of Virology, February 1999, p. 1672-1681, Vol. 73, No. 2
0022-538X/99/$04.00+0
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