丙型肝炎病毒非结构蛋白NS4B诱导细胞非折叠蛋白反应

用RT-PCR和免疫印迹的方法检测稳定表达NS4B的HeLa细胞中的XBP1;通过RT-PCR的方法在表达NS4B的HeLa和Huh-7细胞中检测ATF6,Grp78和caspase-12的转录,并且通过报告基因的方法分析XBP1和Grp78启动子活性。实验结果表明:在表达NS4B的HeLa细胞中检测到XBP1的两种形式(剪接和未剪接),此外,在细胞中ATF6、Grp78的转录水平和XBP1、Grp78启动子的荧光素酶活性较没有表达NS4B的HeLa和Huh-7细胞中的量有所增加;通过染色质免疫沉淀实验(ChIP)分析,这些增加可能是由于XBP1结合到了这些基因的启动子上引起的。总之,实验结果可提示HCVNS4B通过ATF6或XBP1途径引起内质网压力,导致UPR反应。NS4B可能在HCV的致病性中起着重要的作用,特别是在慢性肝炎,甚至肝细胞癌中。     

丙型肝炎病毒非结构蛋白NS4B抑制IFN介导的抗病毒反应

丙型肝炎病毒(Hepatitis C Virus,HCV)非结构蛋白NS4B的功能仍不很清楚。本实验旨在研究NS4B对干扰素介导的抗病毒反应的影响。建立稳定表达NS4B的细胞系后,用空斑实验研究NS4B在不同浓度的IFN_α下对水泡口炎病毒(VSV)的影响,利用代表2308个信号传导相关的基因的微点阵研究其对细胞基因表达的影响,和流式细胞仪分析IFNGR1的荧光强度。结果显示HCV_NS4B能微弱地抑制IFN_α介导的抗病毒反应,可能原因是HCV_NS4B抑制一些与免疫反应相关的基因的表达,特别是与IFN_γ信号传导有关的基因。因此,NS4B对HCV耐受干扰素治疗起一定的作用。     

丙型肝炎病毒非结构蛋白NS2的研究进展

丙型肝炎病毒（hepatitis C virus,HCV）是一种严重危害人类健康的病原体,全球感染率约3％,中国普通人群抗HCV阳性率约3．2％。然而,到目前为止,HCV感染还没有有效的治疗方法。近年的研究发现,HCV非结构蛋白NS2在HCV感染中扮演着重要角色,具有许多重要功能。NS2可以在HCV病毒的包装过程中发挥其功能,还可调节宿主细胞的基因表达及凋亡过程。此外,NS2蛋自还可参与NS5A磷酸蛋白的高度磷酸化修饰过程及为感染性HCV病毒粒子产生所必需。本文综述近几年来关于NS2蛋白的研究进展。     

丙型肝炎病毒非结构蛋白5B的研究进展

已知丙型肝炎病毒非结构蛋白(NS5B)具有RNA依赖的RNA聚合酶的功能,负责病毒基因组的复制。通过体外表达及晶体衍射分析,目前对NS5B的三维结构已有了清晰的描述,对顺B催化该病毒基因组复制的分子机制也有了初步了解;对RNA聚合酶抑制物的研究将为人工设计特异性的抗该病毒药物奠定扎实基础。     

丙型肝炎病毒的非结构蛋白3抑制剂

丙型肝炎严重威胁人类健康,非结构蛋白3（NS3）在丙型肝炎病毒（HCV）多聚蛋白水解过程中起重要作用,被公认为治疗丙型肝炎的有效药物靶标。该文介绍目前国内外有关NS3蛋白酶抑制剂（包括寡肽类抑制剂和非肽小分子抑制剂）的研究进展。     

四环素诱导的丙型肝炎病毒非结构蛋白5B稳定细胞株的构建和检测

丙型肝炎病毒(HCV)感染个体后在宿主细胞内长时间保持低水平复制,与慢性肝炎、肝硬化及肝细胞肝癌的发生密切相关.目前,HCV感染后肝细胞发生转化的具体机制还不清楚.非结构蛋白5B(NS5B)是HCV编码的非结构蛋白之一,具有RNA依赖的RNA聚合酶活性(RdRp),是病毒复制所需的关键酶.除参与病毒复制外,NS5B通过...     

丙型肝炎病毒蛋白的分子生物学研究进展

丙型肝炎病毒(Hepatitis C virus,HCV)是造成慢性肝炎,肝硬化及肝癌的重要原因之一。目前全球发现约有1亿7千万人口感染HCV。HCV的急性感染通常是没有症状的,但50％～80％的病人会转变成为慢性感染患者,而且大约20％的患者会在20年内转变成为肝硬化。一旦确诊为肝硬化,     

丙型肝炎病毒非结构蛋白3在致病中的作用

本文就近几年有关丙型肝炎病毒非结构蛋白３基因（ＨＣＶｎｓ３）的研究进展分别从该基因的结构功能特点,编码产物（ＮＳ３）的免疫原性等方面作了综述,其中重点介绍了ＮＳ３蛋白与肝细胞癌（ＨＣＣ）发生的相关性研究,对目前有关ＨＣＶ研究体系,临床治疗中存在的问题,新进展也作了简要介绍。     

丙型肝炎病毒蛋白的分子生物学研究进展

丙型肝炎病毒(Hepatitis C viruS,HCV)是造成慢性肝炎,肝硬化及肝癌的重要原因之一.目前全球发现约有1亿7千万人口感染HCV.HCV的急性感染通常是没有症状的,但50%～80%的病人会转变成为慢性感染患者,而且大约20%的患者会在20年内转变成为肝硬化.     

丙型肝炎病毒核心蛋白结构及功能研究进展

大量研究结果表明丙型肝炎病毒（ＨＣＶ）核心蛋白是多功能蛋白质,它可能与ＨＣＶ致病（癌）有密切关系。本文简述近年来关于核心蛋白结构与功能的最新进展。并初步探讨了ＨＣＶ核心蛋白可能的致病机制。     

Decrease in Membrane Phospholipid Unsaturation Induces Unfolded Protein Response

Various kinds of fatty acids are distributed in membrane phospholipids in mammalian cells and tissues. The degree of fatty acid unsaturation in membrane phospholipids affects many membrane-associated functions and can be influenced by diet and by altered activities of lipid-metabolizing enzymes such as fatty acid desaturases. However, little is known about how mammalian cells respond to changes in phospholipid fatty acid composition. In this study we showed that stearoyl-CoA desaturase 1 (SCD1) knockdown increased the amount of saturated fatty acids and decreased that of monounsaturated fatty acids in phospholipids without affecting the amount or the composition of free fatty acid and induced unfolded protein response (UPR), evidenced by increased expression of C/EBP homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) mRNAs and splicing of Xbox-binding protein 1 (XBP1) mRNA. SCD1 knockdown-induced UPR was rescued by various unsaturated fatty acids and was enhanced by saturated fatty acid. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), which incorporates preferentially polyunsaturated fatty acids into phosphatidylcholine, was up-regulated in SCD1 knockdown cells. Knockdown of LPCAT3 synergistically enhanced UPR with SCD1 knockdown. Finally we showed that palmitic acid-induced UPR was significantly enhanced by LPCAT3 knockdown as well as SCD1 knockdown. These results suggest that a decrease in membrane phospholipid unsaturation induces UPR.     

丙型肝炎病毒NS3蛋白辅助T细胞表位研究

对2例HCV持续性感染者2个时间点NS3区C末端克隆测序,研究HCV NS3蛋白一个辅助T细胞表位(氨基酸位1248-1261)在HCV感染者体内的保守性;人工合成该表位进行淋巴细胞增殖试验和抑制试验,观察该表位引起免疫应答的水平和特点;通过"刺激-休息-刺激"多轮循环建立该表位特异性的T细胞系,并用流式细胞仪鉴定表型.结果发现该表位在2个病人2个时间点均未变化;观察的2例HCV持续性感染者和1例感染恢复者均对该表位有较强CD4+T细胞应答.建立了针对该表位的表型均一的CD4+辅助T细胞系.本研究提示该表位是一个序列保守的强辅助T细胞表位,对HCV T细胞疫苗的研制有一定意义.     

Modulation of Hepatitis C Virus Genome Encapsidation by Nonstructural Protein 4B

Hepatitis C Virus (HCV) NS4B protein has many roles in HCV genome replication. Recently, our laboratory (Q. Han, J. Aligo, D. Manna, K. Belton, S. V. Chintapalli, Y. Hong, R. L. Patterson, D. B. van Rossum, and K. V. Konan, J. Virol. 85:6464–6479, 2011) and others (D. M. Jones, A. H. Patel, P. Targett-Adams, and J. McLauchlan, J. Virol. 83:2163–2177, 2009; D. Paul, I. Romero-Brey, J. Gouttenoire, S. Stoitsova, J. Krijnse-Locker, D. Moradpour, and R. Bartenschlager, J. Virol. 85:6963–6976, 2011) have also reported NS4B''s function in postreplication steps. Indeed, replacement of the NS4B C-terminal domain (CTD) in the HCV JFH1 (genotype 2a [G2a]) genome with sequences from Con1 (G1b) or H77 (G1a) had a negligible impact on JFH1 genome replication but attenuated virus production. Since NS4B interacts weakly with the HCV genome, we postulated that NS4B regulates the function of host or virus proteins directly involved in HCV production. In this study, we demonstrate that the integrity of the JFH1 NS4B CTD is crucial for efficient JFH1 genome encapsidation. Further, two adaptive mutations (NS4B N216S and NS5A C465S) were identified, and introduction of these mutations into the chimera rescued virus production to various levels, suggesting a genetic interaction between the NS4B and NS5A proteins. Interestingly, cells infected with chimeric viruses displayed a markedly decreased NS5A hyperphosphorylation state (NS5A p58) relative to JFH1, and the adaptive mutations differentially rescued NS5A p58 formation. However, immunofluorescence staining indicated that the decrease in NS5A p58 did not alter NS5A colocalization with the core around lipid droplets (LDs), the site of JFH1 assembly, suggesting that NS5A fails to facilitate the transfer of HCV RNA to the capsid protein on LDs. Alternatively, NS4B''s function in HCV genome encapsidation may entail more than its regulation of the NS5A phosphorylation state.     

丙型肝炎病毒NS3蛋白辅助T细胞表位研究

对２例ＨＣＶ持续性感染者２个时间点ＮＳ３区Ｃ末端克隆测序,研究ＨＣＶ ＮＳ３蛋白一个辅助Ｔ细胞表位（氨基酸位１２４８－１２６１）在ＨＣＶ感染者体内的保守性;人工合成该表位进行淋巴细胞增殖试验和抑制试验,观察该表位引起免疫应答的水平和特点;通过“刺激－休息－刺激”多轮循环建立该表位特异性的Ｔ细胞系,并用流式细胞仪鉴定表型。结果发现该表位在２个病人２个时间点均未变化;观察的２例ＨＣＶ持续性感染者和１例     

The Hepatitis C Virus Non-structural NS5A Protein Impairs Both the Innate and Adaptive Hepatic Immune Response in Vivo

The role of hepatitis C virus (HCV) protein non-structural (NS) 5A in HCV-associated pathogenesis is still enigmatic. To investigate the in vivo role of NS5A for viral persistence and virus-associated pathogenesis a transgenic (Tg) mouse model was established. Mice with liver-targeted NS5A transgene expression were generated using the albumin promoter. Alterations in the hepatic immune response were determined by Western blot, infection by lymphocytic choriomeningitis virus (LCMV), and using transient NS3/4A Tg mice generated by hydrodynamic injection. Cytotoxic T lymphocyte (CTL) activity was investigated by the Cr-release assay. The stable NS5A Tg mice did not reveal signs of spontaneous liver disease. The intrahepatic immunity was disrupted in the NS5A Tg mice as determined by clearance of LCMV infection or transiently NS3/4A Tg hepatocytes in vivo. This impaired immunity was explained by a reduced induction of interferon β, 2′,5′-OAS, and PKR after LCMV infection and an impairment of the CTL-mediated elimination of NS3-expressing hepatocytes. In conclusion, these data indicate that in the present transgenic mouse model, NS5A does not cause spontaneous liver disease. However, we discovered that NS5A could impair both the innate and the adaptive immune response to promote chronic HCV infection.Chronic hepatitis C virus (HCV)⁴ infection is associated with an increased risk of liver cirrhosis and hepatocellular carcinoma (HCC). The HCV genome is a single-stranded positive-sense RNA molecule of ∼9600 bp (1). The viral RNA codes for one large polyprotein of ∼3100 amino acids that is post-translationally processed by cellular and viral proteases, leading to the structural proteins core, E1 and E2, the p7 protein, and the non-structural proteins NS2, NS3, NS4A, NS4B, NS5A, and NS5B (2). The mature NS5A protein is generated by the action of the NS3/NS4A serine protease. NS5A is a phosphoprotein that exists in a basal or in a hyperphosphorylated state (p56 and p58) (3). Through an amphipathic α-helix, NS5A is associated with the cytoplasmic face of the ER (4) and is an integral part of the replication complex (5). Mutations in NS5A affect the rate of HCV replication suggesting a role of NS5A in modulating viral expression and replication (6). Moreover, NS5A is able to interfere with a variety of cellular proteins. Some of these interaction partners, such as Grb2, PI3K, p53, or Raf-1 are important key players in host cell signal transduction, enabling NS5A to deregulate important cellular check points (7–10). Recent reports even suggest that NS5A may deregulate cell cycle progression by modulating the expression of cell cycle regulatory genes (11). In light of these observations and that it has been suggested to transform murine fibroblasts (12), it is speculated that NS5A could represent an important factor for the development of HCV-associated HCC (13).Infection of transgenic mice expressing the complete HCV polyprotein with lymphocytic choriomeningitis virus (LCMV) showed a reduced IFN response and a delayed viral elimination (14). Cell culture-based experiments have shown that NS5A interacts directly with the interferon-dependent induced protein kinase R (PKR), a key player in the cellular antiviral response and that this interaction results in an inhibition of PKR function (15). Therefore, a role of NS5A for the establishment of a chronic HCV infection by inhibiting the innate immunity is conceivable.To enable in vivo studies of NS5A-specific effects transgenic mice were generated with a liver-specific expression of NS5A. We used these mice to show that NS5A affects both the innate and the adaptive hepatic immunity.     

Hepatitis C Virus Non-structural Protein 3 (HCV NS3): A Multifunctional Antiviral Target

Hepatitis C virus non-structural protein 3 contains a serine protease and an RNA helicase. Protease cleaves the genome-encoded polyprotein and inactivates cellular proteins required for innate immunity. Protease has emerged as an important target for the development of antiviral therapeutics, but drug resistance has turned out to be an obstacle in the clinic. Helicase is required for both genome replication and virus assembly. Mechanistic and structural studies of helicase have hurled this enzyme into a prominent position in the field of helicase enzymology. Nevertheless, studies of helicase as an antiviral target remain in their infancy.     

Hepatitis C Virus Induces the Cannabinoid Receptor 1

Background

Activation of hepatic CB₁ receptors (CB₁) is associated with steatosis and fibrosis in experimental forms of liver disease. However, CB₁ expression has not been assessed in patients with chronic hepatitis C (CHC), a disease associated with insulin resistance, steatosis and metabolic disturbance. We aimed to determine the importance and explore the associations of CB₁ expression in CHC.

Methods

CB₁ receptor mRNA was measured by real time quantitative PCR on extracted liver tissue from 88 patients with CHC (genotypes 1 and 3), 12 controls and 10 patients with chronic hepatitis B (CHB). The Huh7/JFH1 Hepatitis C virus (HCV) cell culture model was used to validate results.

Principal Findings

CB₁ was expressed in all patients with CHC and levels were 6-fold higher than in controls (P<0.001). CB₁ expression increased with fibrosis stage, with cirrhotics having up to a 2 fold up-regulation compared to those with low fibrosis stage (p<0.05). Even in mild CHC with no steatosis (F0-1), CB₁ levels remained substantially greater than in controls (p<0.001) and in those with mild CHB (F0-1; p<0.001). Huh7 cells infected with JFH-1 HCV showed an 8-fold upregulation of CB₁, and CB₁ expression directly correlated with the percentage of cells infected over time, suggesting that CB₁ is an HCV inducible gene. While HCV structural proteins appear essential for CB₁ induction, there was no core genotype specific difference in CB₁ expression. CB₁ significantly increased with steatosis grade, primarily driven by patients with genotype 3 CHC. In genotype 3 patients, CB₁ correlated with SREBP-1c and its downstream target FASN (SREBP-1c; R = 0.37, FASN; R = 0.39, p<0.05 for both).

Conclusions/Significance

CB₁ is up-regulated in CHC and is associated with increased steatosis in genotype 3. It is induced by the hepatitis C virus.