新型三明治样荧光偏振筛选模型在新型冠状病毒主蛋白酶小分子抑制剂筛选中的应用北大核心CSCD

新型冠状病毒主蛋白酶(main protease, Mpro)通过水解多聚蛋白质体(polyprotein)调控病毒基因组RNA复制,且人体不存在其同源蛋白酶,这使Mpro成为抗新型冠状病毒药物开发的理想靶标之一。本研究基于荧光偏振技术(fluorescence polarization,FP)和生物素-亲和素反应(biotin-avidin system, BAS)原理,成功地建立了三明治样荧光偏振筛选模型用于Mpro小分子抑制剂的快速筛选。通过对天然产物化合物库进行高通量筛选,发现了漆树酸(anacardic acid,AA)是Mpro的竞争型抑制剂,1,2,3,4,6-O-五没食子酰葡萄糖(1,2,3,4,6-O-pentagalloylglucose,PGG)是Mpro的混合型抑制剂,且已报道的部分抑制剂是非特异性Mpro小分子抑制剂。文中建立的三明治样荧光偏振筛选模型具有良好的简便性、灵敏性和稳定性,初步证实了漆树酸和PGG是一类新型苗头化合物,建立科学严谨的活性评价体系对于抗新型冠状病毒药物的筛选与发现是至关重要的。     

靶向β-catenin/TCF4相互作用小分子抑制剂酶联免疫吸附法高通量筛选模型的优化与应用

在经典的Wnt/β-catenin信号通路中,β-catenin/TCF4 (T-cell factor 4) 相互作用在非小细胞肺癌 (Non-small cell lung cancer,NSCLC) 的生长分化、化疗耐药、转移复发等过程中发挥着重要的促进作用,已成为新型靶向性抗NSCLC转移药物开发的理想靶标之一。为了高效地发现抑制β-catenin/TCF4相互作用的苗头化合物,本研究在应用酶联免疫吸附实验 (Enzyme-linked immunosorbent assay,ELISA) 原理的基础上,通过优化GST-TCF4 βBD包被浓度和β-catenin反应浓度,建立ELISA高通量筛选模型并成功应用于苗头化合物的筛选。ELISA筛选模型优化实验结果表明,选用2 μg/mL GST-TCF4 βBD和0.5 μg/mL β-catenin建立ELISA高通量筛选模型,其Z′因子值为0.83,并成功筛选到具有良好抑制活性的白花丹素 (Plumbagin)。肿瘤细胞增殖实验结果表明,白花丹素对A549、H1299、MCF7和SW480细胞具有明显的细胞毒性。TOPFlash实验结果证实,白花丹素对转染的HEK293细胞内β-catenin介导的转录活性具有显著的抑制作用,β-catenin/TCF4相互作用可能是白花丹素抗癌活性的潜在分子靶标之一。文中以β-catenin/TCF4相互作用为靶标,通过系统的实验优化方案,成功地建立了适用于药物高通量筛选的ELISA筛选模型,为高效筛选靶向β-catenin/TCF4相互作用的小分子抑制剂奠定了实验基础。     

基于密码子优化策略的新型冠状病毒主蛋白酶在大肠杆菌中的表达条件优化与活性鉴定

新型冠状病毒主蛋白酶 (Main protease,Mpro) 在调控新冠病毒RNA复制中具有重要的生物学功能,且Mpro在冠状病毒中的进化高度保守并不易突变,已成为新型广谱抗冠状病毒药物开发的理想靶标之一。为了制备高纯度、高活性的Mpro,根据密码子偏爱性原则,将优化的Mpro基因分别连接到pET-21a与pET-28a表达载体中构建重组质粒。将重组质粒转化到大肠杆菌Escherichia coli Rosetta(DE3) 感受态细胞中,分别进行原核表达条件优化,所表达的重组蛋白质命名为Mpro与Mpro-28。Mpro与Mpro-28经HisTrapTM亲和层析法分离纯化后,以荧光共振能量转移 (Fluorescence resonance energy transfer,FRET) 实验进行生物学活性鉴定。FRET实验结果表明,纯化的Mpro具有良好的水解活性,Km值为11.68 μmol/L,kcat值为0.037/s,比活力不低于25 000 U/mg,约为Mpro-28的25倍,说明天然的氨基端对Mpro的生物学功能是必需的,羧基端残留的多聚组氨酸标签对其水解活性影响较小。文中基于密码子优化策略,成功地进行了新冠病毒Mpro在大肠杆菌中的表达条件优化与活性鉴定,为靶向Mpro广谱抗冠状病毒药物高通量筛选模型的建立奠定了实验基础。     

基于β-catenin/Lef1相互作用为靶标的新型抗肿瘤药物高通量筛选模型的建立

旨在以β-catenin/Lef1相互作用为靶标,建立基于ELISA原理的适用于靶向β-catenin/Lef1相互作用小分子抑制剂筛选的高通量筛选模型。利用DNA重组技术,将构建的β-catenin-pET-30a(+)重组质粒转化大肠杆菌Escherichia coli Rosetta (DE3),经诱导培养后进行β-catenin原核表达。采用亲和层析方法分离纯化β-catenin后,以GSTPulldown实验进行生物学活性鉴定。利用ELISA原理建立β-catenin/GST-Lef1结合的分子模型,通过优选GST-Lef1最佳包被浓度和β-catenin最佳反应浓度,建立适用于靶向β-catenin/Lef1相互作用小分子抑制剂筛选的高通量筛选模型。SDS-PAGE和Western blotting实验证实β-catenin的原核表达。GST Pulldown实验证实纯化的β-catenin具有良好的生物学活性。通过对基于ELISA原理建立的β-catenin/GST-Lef1结合的分子模型优化,选用10μg/mL GST-Lef1和6μg/mLβ-catenin建立ELISA高通量筛选模型,其Z?因子为0.76。本研究成功建立了基于ELISA原理的β-catenin/GST-Lef1结合的分子模型,为靶向β-catenin/Lef1相互作用小分子抑制剂的高通量筛选奠定了基础。     

新型冠状病毒主蛋白酶抑制剂的筛选方法研究进展

新型冠状病毒肺炎(coronavirus disease 2019,COVID-19)席卷全球,具有较高的传染性和死亡率,但目前尚缺乏安全有效的COVID-19疫苗与治疗药物。新型冠状病毒主蛋白酶(main protease,Mpro)的进化高度保守,在调控新冠病毒RNA复制中具有重要的生物学功能,已成为新型广谱抗冠状病毒药物开发的理想靶标之一。简便、快速、灵敏、经济的药物高通量筛选模型的建立是高选择性Mpro抑制剂高效筛选与开发的重要基础和关键技术。本文对Mpro分子结构及其抑制剂的筛选方法研究进展进行了综述和展望,以期为靶向Mpro广谱抗冠状病毒药物的筛选与开发提供有益的借鉴和参考。     

新冠病毒主蛋白酶特异性荧光底物ddRFP-M的制备与鉴定

传统的新冠病毒主蛋白酶(main protease, Mpro)多肽底物具有制备成本高、稳定性差和合成工艺复杂等缺点,积极开发廉价稳定的新型底物具有重要意义。本研究基于二聚化红色荧光蛋白(dimerization-dependent red fluorescent protein, ddRFP)原理,以AVLQS为连接肽,利用基因工程技术制备Mpro特异性荧光底物ddRFP-M,用于Mpro抑制剂的药理活性评价。将连接肽基因插入到密码子优化的RFP-A₁与RFP-B₁基因之间,构建ddRFP-M基因,再将其克隆到pET-28a载体中构建重组质粒。将重组质粒转化至大肠杆菌Rosetta(DE3)感受态细胞中,以卡那霉素抗性法筛选重组子。重组子经低温诱导后,在大肠杆菌中进行荧光底物ddRFP-M的可溶表达,并以HisTrap^TM层析柱进行分离纯化。以荧光动力学检测法和电泳法测定ddRFP-M的底物特异性,并利用荧光底物ddRFP-M评价恩赛特韦和黄芩素的药理活性。结果显示,荧光底物ddRFP-M在大肠杆菌中呈可溶表达并成功进行了分离纯化,其具有良好的底物特异性、灵敏性和可靠性。新冠病毒Mpro特异性荧光底物ddRFP-M的制备,为新冠病毒Mpro抑制剂的药理活性评价奠定了基础。     

组蛋白去乙酰化酶6(HDAC6)抑制剂分子水平高通量筛选模型的建立

旨在建立分子水平HDAC6小分子抑制剂的高通量筛选模型,用于新型HDAC6特异性小分子抑制剂的发现。建立HDAC6的昆虫表达系统,分离纯化HDAC6蛋白,利用底物Boc-Lys(Ac)-AMC对纯化的HDAC6进行测活,并对测活体系进行优化,以SAHA为阳性抑制剂,确定适合高通量筛选的酶及底物浓度,反应时间等。首先构建HDAC6昆虫真核细胞表达载体,转入昆虫细胞中表达,并利用GST亲和柱纯化获得较高纯度的GST-HDAC6融合蛋白;建立体外HDAC6分子测活方法,表明昆虫表达的GST-HDAC6融合蛋白具有去乙酰化酶活性,并通过对多种参数优化使得Z’因子达到0.60,表明分子水平的HDAC6小分子抑制剂高通量筛选体系成功建立。     

以MIF为靶标的抑制剂药物高通量筛选模型的建立和应用

旨在以巨噬细胞迁移抑制因子(MIF)为靶标,采用紫外-分光光度法建立高通量药物筛选体系。对目的基因进行分子克隆,利用大肠杆菌原核表达系统进行纯化得到高纯度的目的蛋白,利用紫外-分光光度法构建酶活体系,并优化体系条件,建立合适的高通量药物筛选模型,最终从384种小分子中筛选出潜在的酶抑制剂。筛选模型构建成功,并筛选出酶活抑制率较高的小分子2种,测得半数抑制浓度IC50分别为59.07μmol/L、44.12μmol/L。针对MIF蛋白,建立了较理想的高通量药物筛选模型,适用于MIF蛋白酶活抑制剂的筛选,有利于后期的药物研发。     

模拟α-螺旋多肽类似物抑制剂设计的研究进展

抑制剂筛选主要是通过反复、高通量地筛选化合物库,这个过程存在着对已有化合物库的依赖性和一定的机遇性。通过分析蛋白质数据库(PDB)发现,大多数蛋白质-蛋白质相互作用(PPI)界面以α-螺旋结构为主体。α-螺旋多肽的骨架结构及其热点氨基酸残基(hotspots)为高效理性设计小分子抑制剂提供了模板。对近几年来依据多肽类似物和小分子化合物模拟α-螺旋结构设计抑制剂的研究进展进行了概述,同时对依据模拟α-螺旋设计抑制剂骨架的结构原理进行了讨论。     

以蛋白激酶G为靶点的抗结核药物筛选模型的建立和初步应用

结核分枝杆菌可以产生11种丝氨酸/苏氨酸蛋白激酶,其中蛋白激酶G(PknG)对于结核分枝杆菌在巨噬细胞内以"持留"状态长期存活有着重要作用。本研究以结核分枝杆菌基因组DNA为模板,在大肠杆菌中克隆表达了MTBPknG蛋白,并分离纯化得到PknG纯酶。本研究还采用三步级联反应方法测定了PknG酶活性,建立和优化了PknG抑制剂高通量筛选模型。利用此模型共筛选发酵液样品2120个,化合物样品2300个,筛选得到阳性化合物1个,阳性发酵液13个,阳性率0.32%。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.