丙型肝炎病毒感染过程中其NS3/4A蛋白酶切割线粒体抗病毒信号蛋白的动态过程

已知丙型肝炎病毒(hepatitis C virus,HCV)可通过其蛋白酶NS3/4A切割线粒体抗病毒信号蛋白(mitochondrial antiviral signaling protein,MAVS)来逃逸天然免疫识别,但尚不清楚其切割动力学及切割在抑制干扰素中的作用。本研究旨在细胞模型中探讨HCV感染过程中病毒复制建立及病毒NS3/4A切割MAVS的动态过程,探究NS3/4A切割MAVS对病毒逃逸宿主天然免疫建立感染的贡献。首先构建基于绿色荧光蛋白(green fluorescent protein,GFP)的MAVS切割报告系统(GFP-NLS-MAVS-TM462),用 HCV Jc1-Gluc 感染Huh7.5/GFP-NLS-MAVS-TM462细胞。结果显示,病毒复制早期MAVS切割效率较低;NS3/4A高效切割MAVS发生于HCV复制晚期,且其切割效率与NS3蛋白水平相关。利用带有GFP ypet的HCV报告病毒Jc1-378-1感染Huh7.5/RFP-NLS-MAVS-TM462细胞,在单细胞水平观察HCV感染阳性细胞中MAVS被切割情况,发现HCV复制细胞中仅部分细胞MAVS被切割。进一步研究发现,不同基因型NS3/4A切割MAVS的效率仅与NS3表达水平相关。以上结果提示,HCV蛋白酶NS3/4A切割MAVS依赖NS3/4A蛋白在病毒复制过程中的累积,对在病毒复制早期逃逸宿主天然免疫建立感染可能无显著贡献。     

丙型肝炎病毒基因突变与免疫逃逸

免疫逃逸（Immune evasion）是指病原体逃避机体免疫监控的现象。在宿主和病毒的长期共同进化过程中,病毒形成了各种逃选机制以逃避宿主的免疫监控,其中病毒基因变异是最主要机制。丙型肝炎病毒（Hepatitis C virus,HCV）在感染个体中表现出极高的基因异质性,能有效地逃逸机体免疫识剐和破坏宿主免疫应答的能力,HCV还可侵袭免疫细胞来抑制机体的免疫功能,而建立HCV持续性感染。了解HCV病毒突变与免疫逃逸机制将会为预防和控制丙型肝炎提供依据。     

细胞异常信号转导:丙型肝炎病毒致病新模式

丙型肝炎病毒(HCV)感染除可致丙型肝炎外,尚可引起Ⅱ型冷球蛋白血症及非霍奇金病恶性淋巴瘤等.同为HCV感染,但却为何表现以不同细胞(肝细胞、淋巴细胞)病变为特征的疾病形式?目前认为此因HCV在不同类型细胞内引发信号转导途径不同所致,因而继"病毒增殖侵害"与"宿主免疫病理反应"的致病机制之后,又提出了细胞异常信号转导为HCV致病模式的观点.     

丙型肝炎病毒蛋白作用于细胞信号转导途径的研究进展

细胞信号转导异常往往与人类疾病的发生、发展密切相关。一些病毒致病和感染机制即为病毒抗原蛋白作用宿主细胞信号转导途径,导致宿主细胞内信号转导发生紊乱。丙型肝炎病毒（HCV）是引发慢性丙型肝炎,导致肝硬化和肝细胞癌发生的主要病原体,但目前HCV的致病机制与宿主内持续感染机制尚不清楚。HCV致病机制可能与HCV表达的蛋白质干扰宿主细胞信号转导途径而导致异常的细胞信号转导有关。研究HCV蛋白对宿主细胞信号转导途径的影响不仅有助于阐明其致病机制,还能为新药设计和寻找新的治疗方法提供新思路和新靶点。本文主要综述了近年来国内外有关HCV蛋白作用细胞信号转导途径的研究进展。     

丙型肝炎病毒致病新模式: 包膜蛋白2对MAPK/ERK途径的激活

细胞信号转导异常可揭示人类疾病发生的本质, 一些病毒的致病机制即源于其蛋白所致宿主细胞内信号转导的紊乱. 丙型肝炎病毒(HCV)感染是引起人类严重肝脏疾病的主要病因, 但致病机制尚未明确. HCV包膜蛋白2(E2蛋白)能介导病毒吸附并结合至靶细胞表面, 此乃HCV感染的前提及首发事件. 推测HCV E2蛋白经与其受体(人CD81)的相互作用而将病毒感染信号传递至宿主细胞内, 使细胞增殖和分化异常, 从而导致感染细胞发生早期病变. 为进一步验证此致病机制, 研究了HCV E2蛋白等诸因素对差异表达人CD81的U937, Molt-4细胞内MAPK/ERK途径的影响, 结果表明, HCV E2蛋白可特异性激活细胞内MAPK/ERK途径, 而HCV E2单抗、CD81单抗、 慢性HCV感染患者血清或MAPK/ERK途径上游MEK1的抑制剂(PD98059)均不同程度地减弱或抑制HCV E2蛋白对MAPK/ERK的激活. 此外, PD98059尚可抑制HCV E2蛋白对MAPK/ERK途径下游转录因子Elk-1的活化. 研究认为, HCV E2蛋白经其相应受体引发的宿主细胞跨膜信号转导异常很可能是HCV的致病机制之一.     

Journal of Hepatology:发现丙肝病毒感染关键模式识别受体

<正>中科院上海巴斯德研究所钟劲研究组通过表达突变型的MAVS蛋白,构建了丙型肝炎(HCV)病毒感染可诱导固有免疫反应的新型细胞系,发现RIG-I并不是HCV病毒感染过程中的关键模式识别受体。相关研究成果已在线发表于《肝脏病学杂志》。HCV是人类的重要病原体,能够通过逃逸宿主的免疫防御系统来建立持续性感染,导致肝硬化和肝癌。病毒在感染过程中被宿主细胞的模式识别受体识别,从而激活固有免疫系统产生抗病毒反应。研究表明RIG-I样受体解旋酶家族中的宿主蛋白RIG-I在肝细胞中转染HCV基因组的3'UTR RNA可以被RIG-I识别并激活干扰素的表达,是HCV的模式识别受体,但该现象从未在HCV病毒感染过程中得到证明。     

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。     

丙型肝炎病毒体外培养技术的新进展

丙型肝炎病毒(hepatitis C virus,HCV)是引起丙型肝炎的病原体,全球约1.7亿人感染HCV.高效体外细胞培养体系的缺乏,严重影响了HCV病毒生命周期的阐明以及抗病毒药物和预防性疫苗的研发.2005年Wakita T建立了JFH1/Huh7真正的HCV体外培养体系,为HCV研究提供了必要的研究条件.其后,研究者为提高病毒复制效率,简便病毒检测方法,在病毒株的选择替换、重组病毒构建、宿主细胞的改造筛选及病毒培养操作技术改进方面做了大量工作,取得了较好进展,为HCV的病毒学研究、药物筛选以及疫苗的研发提供了更有效的技术途径.     

探寻新型HCV同源病毒的自然宿主

丙型肝炎病毒(hepatitis C virus,HCV)感染是一个世界性的公共卫生问题,该病毒感染后可引起急、慢性肝炎。由于HCV的宿主范围较窄,一直未找到合适的动物模型来研究该病毒的致病机制、免疫预防等,至今也无证据表明动物源的HCV同源病毒可能跨种传播给人类。最近,研究者在小型野生动物(如啮齿类动物、蝙蝠)和家养动物(如犬、马、牛)中相继发现了新型HCV同源病毒(HCV样病毒和GBV样病毒),这些病毒分别属于丙型肝炎病毒属(hepacivirus)或持续性G病毒属(pegivirus),研究这些病毒的基因组结构和生物学特征有助于HCV的起源及其致病机制和免疫等研究。本综述从HCV基本特征、相关病毒谈起,着重介绍新型HCV同源病毒,并探寻其自然宿主,进而讨论了人类重要病原之一HCV的起源问题。     

丙型肝炎炎症发生与细胞信号通路异常

丙型肝炎病毒(hepatitis C virus,HCV)感染是引起慢性丙型肝炎的直接原因,炎症的持续发生会导致肝纤维化、硬化甚至是肝癌的出现。炎症发生通常与细胞信号通路异常相关,病毒感染后病毒蛋白干扰宿主细胞正常的信号转导途径,使得促炎和炎症相关分子异常表达,导致炎症的发生。了解HCV感染后炎症发生的分子机制将有助于防止丙型肝炎炎症的恶化,为临床抗病毒治疗提供参考。     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.