HCV CE2融合蛋白在家蚕培养细胞、蚕幼虫中的表达及其初步应用

目的:高效表达HCV CE2融合蛋白并进行初步应用. 方法:将2a型HCV全长CE2基因的cDNA重组于质粒pBacPAK8,构建重组转移载体pBacPAK-CE2,与经线性化修饰的家蚕核型多角体病毒(BmNPV)DNA共转染家蚕培养细胞株,构建重组病毒. 双酶切及PCR鉴定重组病毒基因组中目的片段的表达. 重组病毒感染BmN细胞株及五龄家蚕幼虫后,SDS-PAGE分析细胞培养上清、细胞抽提物及幼虫体液样品中,HCV CE2融合蛋白的特异性条带. 并用间接ELISA法初步检测表达产物的生物活性. 结果:双酶切及PCR鉴定重组病毒基因组含有约1.6 kb的目的片段,重组病毒感染后的BmN细胞培养上清、细胞抽提物及幼虫体液样品中,均可见一Mr约90×103的特异性条带;用间接ELISA检测证明表达产物具有较好的免疫原性. 结论:HCV CE2融合基因在家蚕培养细胞及蚕幼虫中获得了高效表达,并具有生物活性,为进一步进行疫苗的研究及临床诊断试剂的开发奠定基础.     

蝙蝠SARS样冠状病毒S蛋白受体结合域在昆虫细胞中的表达和纯化

目的：在昆虫细胞表达系统中表达蝙蝠SARS样冠状病毒Spike蛋白的受体结合域,并探讨其表达动力学和纯化条件。方法：以PCR扩增蝙蝠SARS样冠状病毒Spike基因的受体结合域片段,产物连接到pMD-T载体,再亚克隆至供体质粒pFAST—HTB,经序列测定确认基因正确克隆,进一步将其转座入Bacmid中,在昆虫细胞S西中进行表达,采用SDS—PAGE和Westernblotting对表达产物进行分析,并通过镍离子螯合树脂纯化重组蛋白。结果：在昆虫细胞表达系统中表达出蝙蝠SARS样冠状病毒Spike蛋白的受体结合域片段,当感染复数（multiplicityofinfectiin,MOI）为2时,重组病毒感染细胞56h后,重组蛋白的表达量达到峰值。结论：蝙蝠SARS样冠状病毒Spike蛋白的受体结合域片段在昆虫细胞表达系统中得到了有效表达,并可通过镍离子螯合树脂纯化重组蛋白。     

Expression of anticardiolipin cofactor, human beta 2-glycoprotein I, by a recombinant baculovirus/insect cell system.

A full-length cDNA coding a human beta 2-glycoprotein I (beta 2-GPI) was introduced into the baculovirus genome to construct a recombinant baculovirus. Spodoptera frugiperda (Sf9) cells were infected with the recombinant baculovirus. A protein (mol. wt 43,000) reactive with anti-beta 2-GPI antisera was produced in the insect cells and secreted into the culture medium. The recombinant beta 2-GPI was purified from the culture supernatant by sequential cardiolipin (CL)-affinity column chromatography and gel filtration. The N-terminal amino acid sequence of the protein was identical to that of the native beta 2-GPI purified from human sera, and a putative signal peptide was cleaved from the secreted form of the recombinant protein. The purified recombinant protein had a cofactor activity which enhances CL binding of anticardiolipin antibodies (aCL) in systemic lupus erythematosus (SLE) patients, as well as the native beta 2-GPI. Thus, the beta 2-GPI expressed in insect cells is an immunologically active cofactor.     

HSV-2糖蛋白D在昆虫-杆状病毒表达系统中的表达及免疫原性分析

目的：在昆虫细胞中表达2型单纯疱疹病毒（HSV-2）糖蛋白D（gD2）胞外区基因,检测其免疫原性。方法：以HSV-2病毒基因组为模板,PCR扩增得到gD2片段,构建至杆状病毒质粒Bacmind中,转染sf9细胞,包装重组杆状病毒,收集后连续感染sf9细胞,收获第4代重组杆状病毒（P4）,通过Western blotting法鉴定蛋白表达情况,采用空斑实验检测重组病毒滴度,将P4代重组病毒作为种子大量感染sf9细胞,上清经镍柱亲和层析进行纯化,将纯化后的蛋白在第0、2和4周免疫BALB/c小鼠（gD2组）,以PBS作为阴性对照（PBS组）,ELISA检测小鼠血清中gD2特异性IgG滴度。结果：PCR鉴定和DNA测序,重组表达质粒gD2-Bacmind构建正确,空斑实验检测重组病毒滴度为2.0×10⁹ pfu·mL^-1,纯化的gD2重组蛋白在相对分子质量37000处出现目标条带,纯度达90%以上。第6周gD2组小鼠免疫血清中gD2特异性IgG抗体滴度Log10平均值达到4.34,与PBS组比较差异有统计学意义（P<0.01）。结论：利用昆虫-杆状病毒表达系统表达的gD2胞外区蛋白具有良好的免疫原性,可作为HSV-2疫苗的候选。     

Nature of the 5′ residue in the M2 domain affects function of the human α1β1 GABAA receptor

The effects on the functional properties of the α₁β₁ GABA_A receptor when the 5′ (α₁ Val260; β₁ Ile255) hydrophobic amino acids in the second transmembrane (M2) region were changed to threonine were examined. In response to a saturating concentration of GABA, the current evoked in mutant receptors showed a decreased rate of desensitization and at equilibrium was a greater fraction of the peak current than in wild-type receptors. The half-saturation concentration of the peak current response to GABA in mutant receptors was comparable to that in wild-type receptors, but the Hill coefficient was reduced to less than one. It was concluded that the 5′ amino acids in the M2 region have a role in the conformational changes that occur within the α₁β₁ GABA_A receptor in response to GABA. Synapse 26:324–327, 1997. © 1997 Wiley-Liss, Inc.     

Exploitation of receptor tyrosine kinases by viral-encoded growth factors

Receptor tyrosine kinases (RTKs) are essential components of cell communication pathways utilized from the embryonic to adult stages of life. These transmembrane receptors bind polypeptide ligands, such as growth factors, inducing signalling cascades that control cellular processes such as proliferation, survival, differentiation, motility and inflammation. Many viruses have acquired homologs of growth factors encoded by the hosts that they infect. Production of growth factors during infection allows viruses to exploit RTKs for entry and replication in cells, as well as for host and environmental dissemination. This review describes the genetic diversity amongst virus-derived growth factors and the mechanisms by which RTK exploitation enhances virus survival, then highlights how viral ligands can be used to further understanding of RTK signalling and function during embryogenesis, homeostasis and disease scenarios.     

Functional analysis and molecular characterization of two acetylcholinesterases from the German cockroach,Blattella germanica

Two acetylcholinesterases (AChEs; BgAChE1 and BgAChE2) from Blattella germanica were functionally expressed using the baculovirus system. Kinetic analysis demonstrated that BgAChE2 had higher catalytic efficiency but lower substrate specificity than BgAChE1. With the exceptions of paraoxon and propoxur, BgAChE1 was generally less sensitive to inhibitors than BgAChE2. Western blot analysis using anti‐BgAChE antibodies revealed that BgAChE1 was far more abundant in all examined tissues compared to BgAChE2, which is only present in the central nervous system. Both BgAChEs existed in dimeric form, covalently connected via a disulphide bridge under native conditions. Most fractions of BgAChE1 had a glycophosphatidylinositol (GPI) anchor, but a small fraction comprised a collagen‐like tail. BgAChE2 appeared to have a collagen‐GPI‐fused tail. Based on the kinetic and molecular properties, tissue distribution and abundance, BgAChE1 was confirmed to play a major role in postsynaptic transmission.     

Cross Talk between Viruses and Insect Cells Cytoskeleton

Viruses are excellent manipulators of host cellular machinery, behavior, and life cycle, with the host cell cytoskeleton being a primordial viral target. Viruses infecting insects generally enter host cells through clathrin-mediated endocytosis or membrane fusion mechanisms followed by transport of the viral particles to the corresponding replication sites. After viral replication, the viral progeny egresses toward adjacent cells and reaches the different target tissues. Throughout all these steps, actin and tubulin re-arrangements are driven by viruses. The mechanisms used by viruses to manipulate the insect host cytoskeleton are well documented in the case of alphabaculoviruses infecting Lepidoptera hosts and plant viruses infecting Hemiptera vectors, but they are not well studied in case of other insect–virus systems such as arboviruses–mosquito vectors. Here, we summarize the available knowledge on how viruses manipulate the insect host cell cytoskeleton, and we emphasize the primordial role of cytoskeleton components in insect virus motility and the need to expand the study of this interaction.     

hTPO膜外区基因的克隆及其杆状病毒表达载体的构建

目的:探索克隆人甲状腺过氧化物酶(hTPO)膜外区基因并构建其杆状病毒表达载体。方法:PCR扩增hTPO膜外区基因,并将其先后重组入pGEM3zf(+)质粒和pFastBac1质粒,以hTPO-pFastBAC1质粒转染E.coliDH10Bac大肠杆菌,获得重组hTPO杆状病毒表达载体(hTPO-Bacmid),每一步均以PCR及酶切、基因测序等方法鉴定其正确性。结果:与预期一致,PCR扩增hTPO膜外区基因的产物为一约2.5kb的条带;hTPO-pGEM3zf(+)经EcoRⅠ+HindⅢ、EcoRⅠ+SalⅠ双酶切后均获得2.5和3.2kb条带;hTPO-pFastBAC1以EcoRⅠ+HindⅢ双酶切得到2.5和4.8kb的带,均符合预期。分别以重组hTPO-pGEM3zf(+)质粒、hTPO-pFastBAC1质粒为模板进行PCR扩增鉴定,均得到约2.5kb的目的条带;对hTPO-Bacmid进行PCR鉴定,得到约4.8kb的片段。对hTPO-pFastBAC1上下游接口测序正确无误。结论:本研究成功克隆了hTPO膜外区基因,并完成了其杆状病毒表达载体hTPO-Bacmid的构建。     

Effects of heme precursors on CYP1A2 and POR expression in the baculovirus/Spodoptera frugiperda system

Objective

CYP1A2 and NADPH-CYP450 oxidoreductase (POR) were expressed in the baculovirus/Spodoptera frugiperda (sf9) system. The aim of this study was to investigate the effects of heme precursors on the expression of CYP1A2 and POR.

Methods

The heme precursors [δ-Aminolaevulinic Acid (5-ALA), Fe³⁺ and hemin] were introduced into the system to evaluate their effects on the expression of CYP1A2, POR and their co-expression. All the proteins were identified using immunoblotting, CO-difference spectroscopy, or cytochrome c assay.

Results

In the present study, functional CYP1A2 and POR were successfully expressed in the baculovirus/sf9 system, and both of them showed high activities. Co-addition of 5-ALA and Fe³⁺ significantly improved expression of CYP1A2 by about 50% compared with the addition of 5-ALA, Fe³⁺ or hemin alone. Either co-addition of 5-ALA and Fe³⁺ or addition of 5-ALA or Fe³⁺ alone improved the POR expression level 2 fold and its activity 7-10 fold compared with control (no addition). However, unlike CYP1A2, there was no difference between the co-addition and addition of these heme precursors alone. Different ratios of BvCYP1A2 to BvPOR also affected the co-expression of CYP1A2 and POR, with a 3:1 ratio of BvCYP1A2 / BvPOR significantly increasing their co-expression. Surprisingly, the addition of 0.1 mM 5-ALA or Fe³⁺ alone, but not their co-addition, could significantly improve the CYP1A2 and POR co-expression (P < 0.05).

Conclusion

5-ALA and Fe³⁺ increased the expression of CYP1A2 and POR in a baculovirus/sf9 system, but the pattern of their expression was different between their expression alone and co-expression.