利用油体表达系统生产外源重组蛋白的研究进展

植物生产外源蛋白日益受到重视,是一个安全廉价的生产系统。植物油体表达系统利用油素蛋白的高表达性和易分离特性改进了植物生物反应器下游加工技术、降低了高纯度药用蛋白的生产成本。本文介绍了油体和油素蛋白的组成结构等特征,重点阐述了国内外各领域用植物油体表达系统生产外源蛋白的研究进展,探讨了油体系统的优势和存在的问题。本实验室利用油体系统开发酸性成纤维细胞生长因子(haFGF)医类新药,生物活性检测正在进行中。油体表达系统作为药用蛋白的新来源,将得到逐步的完善及更广泛的应用。     

利用植物系统表达重组蛋白的的研究进展

植物是可以生产不同生物药剂品的成本低廉的生物反应器,综述了稳定转化系统、瞬时表达系统以及叶绿体基因组转化方法,这三种不同的植物表达系统的特点和研究现状,并对其存在的问题及未来的前景进行了分析。     

Use of FabV-Triclosan Plasmid Selection System for Efficient Expression and Production of Recombinant Proteins in Escherichia coli

Maintenance of recombinant plasmid vectors in host bacteria relies on the presence of selection antibiotics in the growth media to suppress plasmid -free segregants. However, presence of antibiotic resistance genes and antibiotics themselves is not acceptable in several applications of biotechnology. Previously, we have shown that FabV-Triclosan selection system can be used to select high and medium copy number plasmid vectors in E. coli. Here, we have extended our previous work and demonstrated that expression vectors containing FabV can be used efficiently to express heterologous recombinant proteins in similar or better amounts in E. coli host when compared with expression vectors containing β-lactamase. Use of small amount of non-antibiotic Triclosan as selection agent in growth medium, enhanced plasmid stability, applicability in various culture media, and compatibility with other selection systems for multiple plasmid maintenance are noteworthy features of FabV-Triclosan selection system.     

哺乳动物细胞中重组蛋白瞬时表达技术（TGE）的研究进展

近年来越来越多的重组蛋白,尤其是单克隆抗体,作为生物药应用于医疗。临床及实验室研究中,经常要求在短时间内生产一定量的候选蛋白供应研究需求。经典的建立稳定细胞系生产重组蛋白过程复杂冗长,而作为替代方法,瞬时基因表达技术在数周内即可生产数十至数百毫克重组蛋白,得到广泛应用。本文将总结近年来工业及学术上,在哺乳动物细胞尤其是人胚胎肾细胞（HEK293）TL中国仓鼠卵巢细胞（CHO）中瞬时表达重组蛋白的一系列研究,概述瞬时表达技术在宿主细胞改造、表达载体最优化设计、瞬时转染条件等方面的研究进展,并展望其未来发展方向。     

影响外源蛋白在巴斯德毕赤酵母中表达和分泌的研究进展

巴斯德毕赤酵母(Pichia pastoris)表达系统是基因工程研究中广泛使用的外源蛋白表达系统.但外源基因在该系统中表达时,由于受自身特性及环境等诸多因素的影响,在表达过程中出现表达量不够稳定或较低,甚至不表达的情况.本文对影响巴斯德毕赤酵母表达的各种可能因素进行了分析,并就如何提高外源基因在巴斯德毕赤酵母中表达量的问题进行了简要的综述.     

哺乳动物细胞中重组蛋白瞬时表达技术(TGE)的研究进展

近年来越来越多的重组蛋白,尤其是单克隆抗体,作为生物药应用于医疗。临床及实验室研究中,经常要求在短时间内生产一定量的候选蛋白供应研究需求。经典的建立稳定细胞系生产重组蛋白过程复杂冗长,而作为替代方法,瞬时基因表达技术在数周内即可生产数十至数百毫克重组蛋白,得到广泛应用。本文将总结近年来工业及学术上,在哺乳动物细胞尤其是人胚胎肾细胞(HEK293)及中国仓鼠卵巢细胞(CHO)中瞬时表达重组蛋白的一系列研究,概述瞬时表达技术在宿主细胞改造、表达载体最优化设计、瞬时转染条件等方面的研究进展,并展望其未来发展方向。     

Main Strategies of Plant Expression System Glycoengineering for Producing Humanized Recombinant Pharmaceutical Proteins

Most the pharmaceutical proteins are derived not from their natural sources, rather their recombinant analogs are synthesized in various expression systems. Plant expression systems, unlike mammalian cell cultures, combine simplicity and low cost of procaryotic systems and the ability for posttranslational modifications inherent in eucaryotes. More than 50% of all human proteins and more than 40% of the currently used pharmaceutical proteins are glycosylated, that is, they are glycoproteins, and their biological activity, pharmacodynamics, and immunogenicity depend on the correct glycosylation pattern. This review examines in detail the similarities and differences between N- and O–glycosylation in plant and mammalian cells, as well as the effect of plant glycans on the activity, pharmacokinetics, immunity, and intensity of biosynthesis of pharmaceutical proteins. The main current strategies of glycoengineering of plant expression systems aimed at obtaining fully humanized proteins for pharmaceutical application are summarized.     

Expression of Recombinant Potato leafroll virus Structural and Non‐structural Proteins for Antibody Production

Vector pMPM‐A4Ω and vectors pQE‐30 and pET‐45b(+) containing the 6x His‐tag sequence were used for expression of Potato leafroll virus (PLRV) structural and non‐structural proteins in Escherichia coli. Coat protein (CP) and RNA‐dependent RNA polymerase (RdRp)–fragments RdRp_43‐616 and RdRp_304‐537 were chosen for expression. A high level of CP and RdRp_304‐537 was obtained only in an expression system using pET‐45b(+) vector and E. coli Rosetta‐gami 2(DE3) cells. After purification, the His‐tagged PLRV proteins were used for immunization of rabbits.     

SPEX, a System for the Expression of Recombinant Proteins from Gram-Positive Bacterial Vectors

Using a conserved pathway for surface protein extrusion, a system has been developed for the expression and secretion of proteins from gram-positive bacteria. As proof-of-concept, theStreptococcus gordoniiChallis strain has been engineered to express a series of recombinant proteins fused to the conserved region of the M6 protein ofStreptococcus pyogenes.In the prototype surface protein expression system, the recombinant M6 protein is anchored to the surface ofS. gordoniicells expressing it. In order to overexpress the protein and easily purify it away from the bacteria, the protein was modified to enable it to be secreted into the medium. To accomplish this, a stop codon was introduced into the gene just prior to the anchor region using site-directed mutagenesis. Using enzyme-linked immunosorbent assays, it was possible to quantitate the amount of protein expressed using this system. With little or no optimization, 3 mg of protein per liter of culture was expressed and secreted into the medium of a bacterial culture grown to an OD₆₀₀equal to 1.0. This system should be broadly applicable for the expression and secretion of a variety of proteins (antigens, hormones, and enzymes) directly into the medium.     

Comparison of Expression Vectors for Transient Expression of Recombinant Proteins in Plants

Production of recombinant proteins in plants is of increasing importance for practical applications. However, the production of stable transformed transgenic plants is a lengthy procedure. Transient expression, on the other hand, can deliver recombinant proteins within a week, and many viral vectors have been constructed for that purpose. Each of them is reported to be highly efficient, robust and cost-effective. Here, a variety of expression vectors which were designed for transient and stable plant transformation, including pPZP3425, pPZP5025, pPZPTRBO, pJLTRBO, pEAQ-HT and pBY030-2R, was compared for the expression of green fluorescent protein and β-glucuronidase in Nicotiana benthamiana by Agrobacterium-mediated transient expression. Our results show that pPZPTRBO, pJLTRBO and pEAQ-HT had comparable expression levels without co-infiltration of a RNA-silencing inhibitor. The other vectors, including the non-viral vectors pPZP5025 and pPZP3425, needed co-infiltration of the RNA-silencing inhibitor P19 to give good expression levels.     

An Expression System for the Single-Step Production of Recombinant Human Amidated Calcitonin

Amidating mouse pituitary cells (AtT-20) have been engineered to secrete human calcitonin (hCT) in the fully active amidated form, without the need of additional enzymatic or chemical modifications. The 141-residue human calcitonin precursor has first been cloned in the eucaryotic expression vector pRc/RSV, and the resulting plasmid pRc/RSV/hCT introduced in AtT-20 cells. After transfection, 122 independent clones resistant to G-418 were selected and screened for calcitonin production using a competitive ELISA specifically designed to detect the amidated form of calcitonin. One of these clones was amplified and showed expression of 17 ng/ml of hCT, with a 70% increase in productivity after cAMP treatment. Calcitonin was partially purified from culture medium by two sequential steps of reverse-phase chromatography and characterized in terms of immunoreactivity and molecular weight by TOF-MALDI mass spectroscopy, which confirmed the intended chemical nature and the presence of the C-terminal amidated residue.     

毕赤酵母表达体系中重组蛋白的分离纯化

随着基因重组技术的快速发展,基因工程产品的利用越来越广泛,但其分离纯化的成本约占总成本的60%～70%.因此,探索一些简单有效的分离纯化方法尤为必要.简单介绍了目前较为流行的毕赤酵母表达体系,着重概述了重组蛋白分离纯化技术方法的应用情况.     

CHO/dhfr-细胞定点整合高效表达系统的建立

为了克服随机整合建立高表达细胞株时“位置效应”所带来的不可预知的后果,我们尝试建立基于定点整合的CHO高效表达系统。首先设计一个新的高效筛选载体pMCEscan。该载体含有报告基因(k2tPA)、扩增基因(dhfr)、重组酶识别序列(FRT)及筛选基因(neo),且neo基因的表达经过系统的弱化,确保能够对基因组中的整合位点进行大规模的高效筛选。然后利用该载体转染CHO/dhfr-细胞并进行大规模筛选以获得足够多的阳性克隆,并对阳性克隆进行系统分析,筛选出报告基因表达水平高、单拷贝且扩增效果好的克隆,此克隆被认为筛选载体整合入CHO细胞基因组中转录热点(Hotspot)区域,从而获得了能够实现外源基因在基因组中定点整合和有效表达的CHO/dhfr-细胞系。随后利用位点特异性重组系统(FLP-FRT)将外源基因定点整合到Hotspot区域,以实现外源基因在CHO细胞基因组中的定点整合及高效表达。并利用该细胞系实现了k2tPA的高表达,表达量达到17.1μg/106cell.24h。该研究致力于CHO细胞基因组中高表达位点的寻找和确认,建立基于定点整合的哺乳动物细胞高效表达系统。     

Efficient Agroinfiltration of Plants for High-level Transient Expression of Recombinant Proteins

Mammalian cell culture is the major platform for commercial production of human vaccines and therapeutic proteins. However, it cannot meet the increasing worldwide demand for pharmaceuticals due to its limited scalability and high cost. Plants have shown to be one of the most promising alternative pharmaceutical production platforms that are robust, scalable, low-cost and safe. The recent development of virus-based vectors has allowed rapid and high-level transient expression of recombinant proteins in plants. To further optimize the utility of the transient expression system, we demonstrate a simple, efficient and scalable methodology to introduce target-gene containing Agrobacterium into plant tissue in this study. Our results indicate that agroinfiltration with both syringe and vacuum methods have resulted in the efficient introduction of Agrobacterium into leaves and robust production of two fluorescent proteins; GFP and DsRed. Furthermore, we demonstrate the unique advantages offered by both methods. Syringe infiltration is simple and does not need expensive equipment. It also allows the flexibility to either infiltrate the entire leave with one target gene, or to introduce genes of multiple targets on one leaf. Thus, it can be used for laboratory scale expression of recombinant proteins as well as for comparing different proteins or vectors for yield or expression kinetics. The simplicity of syringe infiltration also suggests its utility in high school and college education for the subject of biotechnology. In contrast, vacuum infiltration is more robust and can be scaled-up for commercial manufacture of pharmaceutical proteins. It also offers the advantage of being able to agroinfiltrate plant species that are not amenable for syringe infiltration such as lettuce and Arabidopsis. Overall, the combination of syringe and vacuum agroinfiltration provides researchers and educators a simple, efficient, and robust methodology for transient protein expression. It will greatly facilitate the development of pharmaceutical proteins and promote science education.     

CHO/dhfr-细胞定点整合高效表达系统的建立

为了克服随机整合建立高表达细胞株时“位置效应”所带来的不可预知的后果,我们尝试建立基于定点整合的CHO高效表达系统。首先设计一个新的高效筛选载体pMCEscan。该载体含有报告基因(k₂tPA)、扩增基因（dhfr）、重组酶识别序列(FRT)及筛选基因（neo）,且neo基因的表达经过系统的弱化,确保能够对基因组中的整合位点进行大规模的高效筛选。然后利用该载体转染CHO/dhfr^－细胞并进行大规模筛选以获得足够多的阳性克隆,并对阳性克隆进行系统分析,筛选出报告基因表达水平高、单拷贝且扩增效果好的克隆,此克隆被认为筛选载体整合入CHO细胞基因组中转录热点（Hot spot）区域,从而获得了能够实现外源基因在基因组中定点整合和有效表达的CHO/dhfr-细胞系。随后利用位点特异性重组系统（FLP-FRT）将外源基因定点整合到Hot spot区域,以实现外源基因在CHO细胞基因组中的定点整合及高效表达。并利用该细胞系实现了k₂tPA的高表达,表达量达到17.1μg/10⁶cell·24h。该研究致力于CHO细胞基因组中高表达位点的寻找和确认,建立基于定点整合的哺乳动物细胞高效表达系统。     

CHO/dhfr-细胞定点整合高效表达系统的建立

为了克服随机整合建立高表达细胞株时“位置效应”所带来的不可预知的后果,我们尝试建立基于定点整合的CHO高效表达系统。首先设计一个新的高效筛选载体pMCEscan。该载体含有报告基因（k2tPA）、扩增基因（dhfr）、重组酶识别序列（FRT）及筛选基因（neo）,且neo基因的表达经过系统的弱化,确保能够对基因组中的整合位点进行大规模的高效筛选。然后利用该载体转染CHO／dhfr^-细胞并进行大规模筛选以获得足够多的阳性克隆,并对阳性克隆进行系统分析,筛选出报告基因表达水平高、单拷贝且扩增效果好的克隆,此克隆被认为筛选载体整合入CHO细胞基因组中转录热点（Hotspot）区域,从而获得了能够实现外源基因在基因组中定点整合和有效表达的CHO／dhfr-细胞系。随后利用位点特异性重组系统（FLP-FRT）将外源基因定点整合到Hotspot区域,以实现外源基因在CHO细胞基因组中的定点整合及高效表达。并利用该细胞系实现了k2tPA的高表达,表达量达到17．1μg／10^6cell·24h。该研究致力于CHO细胞基因组中高表达位点的寻找和确认,建立基于定点整合的哺乳动物细胞高效表达系统。     

重组蛋白药物的生产技术进展

重组蛋白药物是生物药物中的核心产品,主要是通过基因工程菌来生产功能蛋白或其突变体,用于弥补体内蛋白的缺失,从而对疾病的治疗发挥关键作用。近年来,重组蛋白药物在疾病治疗中发挥作用越来越大,相关技术也发展迅速。通过综述重组蛋白药物的中上游生产流程,并重点分析了重组蛋白药物在表达系统、细胞培养、纯化和质量控制等环节的最新技术进展,展示了重组蛋白药物制备的技术提升水平,以期为国内重组蛋白药物的生产提供一定的参考依据。     

2 Protein Folding and its Implications for the Production of Recombinant Proteins

Abstract

Humans have utilised plant derived natural products as medicines for millenia. Moreover, many contemporary pharmaceuticals are also natural products or derivatives thereof. However, the full potential of these compounds remains to be exploited because often they are: complex and difficult to synthesise; found in low quantities; produced by undomesticated and sometimes rare plants; and, their synthesis is routinely influenced by weather conditions. Potentially, the in vitro culture of cells from the corresponding plant species could circumvent some of these problems but the growth of plant cells on an industrial scale is also problematic. The recent isolation and culture of cambial meristematic cells (CMCs), stem cells which ordinarily generate the plant vasculature, may now provide a key platform technology to help realise the full potential of plant natural products.     

蜘蛛丝蛋白的模块结构性能和重组表达

蜘蛛丝是一类天然蛋白质纤维,具有独特的机械性能（高强度、高弹性和高断裂功等）和卓著的生物学特性（生物可降解性和与生物组织的相容性等）,在生物医学、材料、纺织和军事等领域都有着很高的潜在应用价值。综述了不同蜘蛛丝蛋白的模块结构特征及与其功能的关系,扼要介绍了目前利用各种基因工程方法表达重组蜘蛛丝蛋白的研究进展。