A型流感病毒非结构蛋白NS1与宿主相互作用的研究进展

作为A型流感病毒的非结构蛋白,NS1蛋白是流感病毒的一个重要的毒力因子,决定了病毒在宿主细胞内的破坏作用。概述了NS1蛋白对宿主细胞蛋白合成、宿主细胞凋亡的影响,及其拮抗干扰素的作用。     

A型流感病毒NS1蛋白羧基端PL结构域影响NS1在细胞核内的定位

A型流感病毒NS1蛋白羧基端4个氨基酸可以与PDZ结构域(the domain of PSD95,Dig and ZO-1)相结合,称为PL结构域(PDZ ligand domain)．对不同亚型或毒株的流感病毒而言,其NS1蛋白PL结构域的组成存在比较大的差异．有研究发现这种差异能够影响NS1与宿主细胞蛋白的相互作用进而影响病毒的致病力．为进一步探讨PL结构域对NS1蛋白生物学特性的影响,首先构建出4种不同亚型流感病毒(H1N1、H3N2、H5N1、H9N2)来源的NS1绿色荧光蛋白表达质粒．在此基础上,对野生型H3N2病毒NS1表达质粒进行人工改造,将其PL结构域缺失或者替换为其他亚型流感病毒的PL结构域,制备出4种重组NS1蛋白表达质粒．通过比较上述不同NS1蛋白在HeLa细胞中的定位情况发现,只有野生型H3N2病毒的NS1蛋白可以定位于核仁当中,而野生型H1N1、H5N1、H9N2病毒的NS1蛋白以及PL结构域缺失或替代的H3N2病毒NS1蛋白都不能定位于核仁．而通过比较上述NS1蛋白在流感病毒易感的MDCK细胞中的定位,进一步发现所有这些蛋白均不定位于核仁．上述结果表明：PL结构域的不同可以明显影响NS1蛋白在HeLa细胞核内的定位和分布,这有可能造成其生物学功能的差异．同时,NS1蛋白在细胞核内的定位还与宿主细胞的来源有着密切关系．     

甲型流感病毒非结构蛋白的研究进展

PA、PB1和PB2以及NS1蛋白作为甲型流感病毒的非结构蛋白,虽然不直接参与病毒颗粒的组装,但是在病毒的复制周期中起到非常重要的调控作用.由PA、PB1和PB2组成的RNA聚合酶主要参与病毒mRNA的合成以及病毒基因组RNA的复制,而NS1蛋白则通过抑制宿主细胞的干扰素应激系统来拮抗宿主的抗病毒反应.通过研究甲型流感病毒非结构蛋白的结构与功能,对了解流感病毒复制及开发新型抗流感病毒药物有重要意义.     

禽流感病毒NS1蛋白对细胞的影响

NS1蛋白为流感病毒非结构蛋白,只在病毒侵入宿主细胞后产生.目前NS1蛋白对细胞整体水平上的作用仍不清楚,为了解NS1蛋白在病毒感染细胞中的作用,构建了重组质粒pCMV-myc-NS1并将其转染A549细胞,利用双向电泳技术检测了受NS1蛋白调控的宿主蛋白,以期从蛋白质组水平上研究禽流感病毒与宿主细胞间的相互作用.同时,还检测了转染NS1对细胞增殖和细胞周期的影响.结果显示,NS1在细胞中的表达,能够明显引起宿主细胞代谢的变化,并通过阻滞细胞周期的正常进行而减缓细胞的增殖.     

不同亚型流感病毒NS1蛋白在酵母菌细胞中转录激活功能的差异

非结构蛋白1（nonstructural protein1,NS1）是甲型流感病毒一种重要的调控蛋白,与病毒的毒力密切相关,本文检测了不同亚型流感病毒NS1蛋白在酵母菌细胞中的基因转录激活能力,将携带NS1基因的诱饵载体与空的猎物载体共转化AH109和Y187酵母菌细胞,观察AH109在QDO培养基上的生长情况,以X-α-gal为底物检测其分泌α-半乳糖苷酶的能力;通过ONPG实验定量分析Y187酵母菌细胞β-半乳糖苷酶活性的强弱,结果发现转化H1N1,H5N1和H9N2亚型流感病毒NS1基因的AH109酵母菌细胞能够在QDO培养基上生长,并分泌高水平的α-半乳糖苷酶,同时这些基因转化的Y187酵母菌细胞具有很强的β-半乳糖苷酶活性,与此相反,H3N2亚型流感病毒NS1基因转化AH109和Y187后,上述实验结果均为阴性,这说明H1N1,H5N1和H9N2亚型的NS1蛋白具有刺激酵母菌细胞基因转录的功能,而H3N2亚型的NS1蛋白缺乏这种能力,表明NS1蛋白型别的不同可造成其生物学活性的差异。     

A型流感病毒NS1蛋白与宿主的相互作用

A型流感病毒非结构蛋白1(nonstructural protein l, NS1)全长约为230个氨基酸,主要包括两个功能结构域,即 N-末端的RNA结合结构域和C-末端的效应结构域.NS1是一个多功能病毒蛋白,它不仅影响着该病毒其他基因的表达,更能通过与宿主细胞多种因子的相互作用干预宿主细胞的正常功能,抵抗宿主的抗病毒系统.因此, NS1被认为是A型流感病毒的一个重要毒力因子.本文综述了 NS1蛋白与宿主相互作用的最新研究进展,为进一步揭示NS1 蛋白的功能提供了参考.     

甲型流感病毒非结构蛋白NS1功能研究进展

甲型流感病毒(influenza A virus,IAV)是每年季节性流感的主要病原体,也是全球儿童急性呼吸道感染的重要病毒性病原。非结构蛋白1(nonstructural protein 1,NS1)是由病毒基因组编码的蛋白,表达于被感染的细胞中,但不存在于病毒颗粒中。近年来,大量研究表明NS1是IAV的重要毒力因素,通过NS1-RNA之间、NS1-蛋白之间的相互作用,在拮抗宿主抗病毒反应、抑制宿主细胞凋亡、调节宿主及自身基因表达等多方面发挥作用。深入研究NS1与宿主细胞的相互作用,不仅可加深对IAV致病机制的理解,还可为预防和控制IAV的传播甚至暴发奠定理论基础,在新型抗病毒药物及疫苗研制中有着重要的应用价值。     

流感病毒NS1蛋白稳定表达的A549细胞系建立

A型流感病毒的NS1(Nonstructurol 1 protein,NS1)蛋白是病毒复制、毒力等的重要调节蛋白.运用RT-PCR方法扩增A/Beijing/501/2009(H1N1)流感病毒NS1基因,克隆至真核表达载体pCMV-HA,用Lipofectamine2000将线性化pCMV-HA-NS1与neo基因共同转染A549细胞,通过G418筛选获得阳性重组细胞,并采用PCR、RT-PCR、Western blot技术检测重组细胞中NS1蛋白的表达,通过免疫荧光技术观察NS1蛋白在细胞中的定位.PCR、RT-PCR检测显示NS1基因成功整合进入细胞基因组,并转录为mRNA;Western blot检测显示重组细胞系稳定表达NS1蛋白,免疫荧光显示NS1蛋白定位于细胞核内.表明通过G418筛选,成功构建稳定表达NS1蛋白的重组A549-HA-NS1细胞系,且NS1蛋白定位于细胞核内,为进一步研究NS1蛋白的生物学功能奠定基础.     

PR8F/NS1不同位点突变株对小鼠致病性的比较研究

为了探索NS1不同位点突变对流感病毒毒力的影响以及NS1毒力相关位点的作用机制。分析流感病毒NS1蛋白的毒力相关关键基因区段和关键位点,以实验室保存的H1N1亚型流感病毒PR8F为模板,对其NS1基因的第42、81、149位氨基酸分别进行定点突变。利用反向遗传操作技术,成功拯救出突变毒株PR8F-42、PR8F-81、PR8F-149。将获救病毒接种SPF鸡胚,连续传代5代,至病毒能够稳定扩增后,通过血凝效价分析病毒复制效率。并将获救病毒与PR8F均以106 TCID50/100μL感染BALB/c小鼠,观察各组小鼠临床表现、体重变化及存活率。剖检攻毒后死亡小鼠,观察病理特征,制作肺组织病理切片。并提取小鼠肺脏RNA,通过qPCR检测各组小鼠肺脏的病毒载量。结果表明,PR8F的NS1蛋白第42位氨基酸由丝氨酸(Ser)改变为脯氨酸(Pro)对小鼠的致病性无明显改变。第81位、149位氨基酸突变则都能减弱突变株对小鼠的致病性,进而为研究NS1毒力相关位点的作用机制提供平台。     

不同亚型流感病毒NS1蛋白的细胞定位差异分析

NS1蛋白是流感病毒编码的一种小分子多功能蛋白,可在病毒的复制过程中抑制宿主细胞的抗病毒免疫应答。为研究不同亚型流感病毒的NS1蛋白在细胞内的定位差异,分别用H1N1亚型WSN、PR8和CA04毒株,H9N2亚型SD毒株及H7N9亚型AH01毒株感染A549、MDCK细胞系以及构建的可表达不同亚型流感病毒NS1蛋白的p CMV-Myc-NS1质粒转染293T细胞,用激光共聚焦显微镜观察发现不同亚型流感病毒在不同细胞系和时间点的定位差异,感染后24 h时WSN和PR8毒株的NS1主要定位于细胞质中,而CA04和SD毒株主要定位于细胞核内。另外,观察过表达的WSN、SD和AH01毒株NS1的细胞定位,转染后24 h时WSN毒株NS1定位于细胞质中,而SD和AH01毒株主要定位于细胞核中。经氨基酸序列比对,对WSN毒株NS1蛋白进行关键氨基酸点突变,结果显示单一位点的改变未导致NS1蛋白细胞定位的改变,其细胞定位的差异不是由单一位点决定的。综上所述,分析不同亚型中的NS1的定位差异,这对进一步了解NS1蛋白同宿主细胞不同区域的蛋白的相互作用、流感病毒的调节机制以及病毒感染细胞中天然免疫反应具有一定的指导意义。     

Structural and functional analysis of NS1 and NS2 proteins of H1N1 subtype

Influenza A virus (H1N1), a genetic reassortment of endemic strains of human, avian and swine flu, has crossed species barrier to human and apparently acquired the capability of human to human transmission. Some strains of H5N1 subtype are highly virulent because NS1 protein inhibits antiviral interferon α/β production. Another protein NS2 mediates export of viral ribonucleoprotein from nucleus to the cytoplasm through export signal. In this paper, we have studied structure-function relationships of these proteins of H1N1 subtype and have determined the cause of their pathogenicity. Our results showed that non-conservative mutations slightly stabilized or destabi- lized structural domains of NS1 or NS1-dsRNA complex, hence slightly increased or decreased the function of NS1 protein and consequently enhanced or reduced the pathogenicity of the H1N1 virus. NS2 protein of different strains carried non-conservative mutations in different domains, resulting in slight loss of function. These mutations slightly decreased the pathogenicity of the virus. Thus, the results confirm the structure-function relationships of these viral proteins.     

抗登革病毒NS1单抗的制备及检测NS1方法的建立

制备抗登革病毒NS1蛋白单克隆抗体,建立检测NS1的ELISA方法。表达1~4型登革病毒NS1蛋白,将1型NS1蛋白纯化后免疫BALB/c小鼠,通过杂交瘤技术制备单克隆抗体。经ELISA、Western blotting、间接免疫荧光筛选和鉴定单克隆抗体,进行纯化和HRP标记。通过鉴定每两株单抗之间是否存在竞争作用,选择非竞争单抗组合并建立NS1捕获法ELISA。结果获得7株高滴度抗NS1单抗,捕获法ELISA可以检出10ng/mL NS1。原核表达登革病毒NS1蛋白制备的单抗可以和天然病毒抗原反应,NS1捕获法ELISA可以用于登革病毒感染检测。     

NS1-binding protein abrogates the elevation of cell viability by the influenza A virus NS1 protein in association with CRKL

The influenza A virus non-structural protein 1 (NS1) is a multifunctional virulence factor consisting of an RNA binding domain and several Src-homology (SH) 2 and SH3 binding motifs, which promotes virus replication in the host cell and helps to evade antiviral immunity. NS1 modulates general host cell physiology in association with various cellular molecules including NS1-binding protein (NS1-BP) and signaling adapter protein CRK-like (CRKL), while the physiological role of NS1-BP during influenza A virus infection especially in association with NS1 remains unclear. In this study, we analyzed the intracellular association of NS1-BP, NS1 and CRKL to elucidate the physiological roles of these molecules in the host cell. In HEK293T cells, enforced expression of NS1 of A/Beijing (H1N1) and A/Indonesia (H5N1) significantly induced excessive phosphorylation of ERK and elevated cell viability, while the over-expression of NS1-BP and the abrogation of CRKL using siRNA abolished such survival effect of NS1. The pull-down assay using GST-fusion CRKL revealed the formation of intracellular complexes of NS1-BP, NS1 and CRKL. In addition, we identified that the N-terminus SH3 domain of CRKL was essential for binding to NS1-BP using GST-fusion CRKL-truncate mutants. This is the first report to elucidate the novel function of NS1-BP collaborating with viral protein NS1 in modulation of host cell physiology. In addition, an alternative role of adaptor protein CRKL in association with NS1 and NS1-BP during influenza A virus infection is demonstrated.     

Identification of human hnRNP C1/C2 as a dengue virus NS1-interacting protein

Dengue virus nonstructural protein 1 (NS1) is a key glycoprotein involved in the production of infectious virus and the pathogenesis of dengue diseases. Very little is known how NS1 interacts with host cellular proteins and functions in dengue virus-infected cells. This study aimed at identifying NS1-interacting host cellular proteins in dengue virus-infected cells by employing co-immunoprecipitation, two-dimensional gel electrophoresis, and mass spectrometry. Using lysates of dengue virus-infected human embryonic kidney cells (HEK 293T), immunoprecipitation with an anti-NS1 monoclonal antibody revealed eight isoforms of dengue virus NS1 and a 40-kDa protein, which was subsequently identified by quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS) as human heterogeneous nuclear ribonucleoprotein (hnRNP) C1/C2. Further investigation by co-immunoprecipitation and co-localization confirmed the association of hnRNP C1/C2 and dengue virus NS1 proteins in dengue virus-infected cells. Their interaction may have implications in virus replication and/or cellular responses favorable to survival of the virus in host cells.     

The PDZ-binding motif of the avian NS1 protein affects transmission of the 2009 influenza A(H1N1) virus

By nature of their segmented RNA genome, influenza A viruses (IAVs) have the potential to generate variants through a reassortment process. The influenza nonstructural (NS) gene is critical for a virus to counteract the antiviral responses of the host. Therefore, a newly acquired NS segment potentially determines the replication efficiency of the reassortant virus in a range of different hosts. In addition, the C-terminal PDZ-binding motif (PBM) has been suggested as a pathogenic determinant of IAVs. To gauge the pandemic potential from human and avian IAV reassortment, we assessed the replication properties of NS-reassorted viruses in cultured cells and in the lungs of mice and determined their transmissibility in guinea pigs. Compared with the recombinant A/Korea/01/2009 virus (rK09; 2009 pandemic H1N1 strain), the rK09/VN:NS virus, in which the NS gene was adopted from the A/Vietnam/1203/2004 virus (a human isolate of the highly pathogenic avian influenza H5N1 virus strains), exhibited attenuated virulence and reduced transmissibility. However, the rK09/VN:NS-PBM virus, harboring the PBM in the C-terminus of the NS1 protein, recovered the attenuated virulence of the rK09/VN:NS virus. In a guinea pig model, the rK09/VN:NS-PBM virus showed even greater transmission efficiency than the rK/09 virus. These results suggest that the PBM in the NS1 protein may determine viral persistence in the human and avian IAV interface.     

H5N1亚型禽流感病毒NS1基因在昆虫细胞中的表达

将H5N1亚型禽流感病毒（AIV）NS1基因插入到杆状病毒转移载体pFastBac1中,获得重组转移载体pFastBac1- NS1。将pFastBac1- NS1转化到DH10Bac感受态细胞中,筛选到重组转座子rBacmid-NS1。在脂质体转染试剂介导下将rBacmid-NS1转染对数生长期的Sf9昆虫细胞获得重组杆状病毒rBV-NS1。rBV-NS1感染Sf9细胞后,通过SDS-PAGE、Western blot和ELISA分析表明：获得了分子量为26ku的特异性NS1蛋白;并且该蛋白可与H5N1 AIV攻毒鸭的血清发生特异性免疫反应,而不能与H5N1AIV灭活疫苗免疫鸭的血清发生反应。试验结果表明：NS1在Sf9昆虫细胞中获得了高效表达,具有与天然蛋白相似的免疫活性,并可以作为区分免疫及自然感染个体的鉴别诊断抗原。本实验为建立禽流感病毒自然感染家禽与禽流感灭活苗免疫家禽的鉴别诊断方法奠定基础。     

人H5N1亚型禽流感病毒安徽株NS1基因的克隆及在原核系统的表达

利用RT-PCR方法,从人H5N1亚型禽流感病毒安徽株扩增到了NS1基因,对其进行了克隆、序列测定和分析,并在原核系统高效表达和纯化了NS1蛋白。进化分析表明,A/Anhui/01/2005毒株与近些年国内分离的水禽H5N1病毒进化关系更为接近。NS1与福建、湖南分离的禽流感病毒同源性最高,分别达到99.1%和98.2%。序列分析表明,与病毒的致病性相关的92位氨基酸为Asp,与病毒的细胞因子抗性相关的80~84位氨基酸发生缺失,与断裂/多聚腺苷酸化特异性因子结合的基序改变为GFEWN,和病毒致死性相关的PL基序为ESEV。随后在大肠杆菌高效表达并纯化了NS1蛋白。NS1基因及其编码产物的特性分析以及在原核系统的表达,为进一步研究NS1的致病机制和抗病毒药物研制奠定了基础。     

Influenza A virus NS1 protein‐induced JNK activation and apoptosis are not functionally linked

Expression of the influenza A virus (IAV) nonstructural protein (NS1) results in the activation of c‐Jun N‐terminal kinase (JNK). Both NS1 and JNK are involved in apoptosis induction. To investigate their interrelationship, we stably expressed a tamoxifen inducible NS1 oestrogen receptor fusion‐protein (NS1ERT) in mammalian cells. Upon tamoxifen stimulation, NS1ERT‐expressing cells partially rescued the attenuated replication of NS1‐deficient IAVs and also inhibited interferon up‐regulation, confirming the functional competence of NS1ERT. Tamoxifen‐induced NS1ERT created a cytopathic phenotype and led to the activation of JNK and apoptosis. Induction of NS1F103SERT mutant failed to activate JNK, but induced apoptosis, whereas the induction of NS1M106IERT led to JNK phosphorylation, but not apoptosis, indicating that JNK activation and apoptosis induction are not functionally linked. Further mutational analysis highlighted that apoptosis induction is a function of the C‐terminal effector domain of NS1. Finally, IAVs encoding mutant NS1 revealed a modulating effect of NS1 on apoptosis induction in a genuine infection. With respect to apoptogenicity, an NS1 mutant virus that results in a super activation of JNK behaves similarly to the JNK nonactivating virus expressing NS1F103S, thus confirming that NS1‐mediated JNK activation and apoptosis induction are also functionally independent from each other in vivo.     

Inhibition of highly pathogenic avian H5N1 influenza virus replication by RNA oligonucleotides targeting NS1 gene

H5N1 avian influenza virus (AIV) has caused widespread infections in poultry and wild birds, and has the potential to emerge as a pandemic threat to human. In order to explore novel approaches to inhibiting highly pathogenic H5N1 influenza virus infection, we have developed short RNA oligonucleotides, specific for conserved regions of the non-structural protein gene (NS1) of AIV. In vitro the hemagglutination (HA) titers in RNA oligonucleotide-treated cells were at least 5-fold lower than that of the control. In vivo, the treatment with three doses of RNA oligonucleotides protected the infected chickens from H5N1 virus-induced death at a rate of up to 87.5%. Plaque assay and real-time PCR analysis showed a significant reduction of the PFU and viral RNA level in the lung tissues of the infected animals treated with the mixed RNA oligonucleotides targeting the NS1 gene. Together, our findings revealed that the RNA oligonucleotides targeting at the AIV NS1 gene could potently inhibit avian H5N1 influenza virus reproduction and present a rationale for the further development of the RNA oligonucleotides as prophylaxis and therapy for highly pathogenic H5N1 influenza virus infection in humans.