Summary

用于结构和生化研究的人溶质载体的高通量表达和纯化

Published: September 29, 2023
doi:

Summary

人膜转运蛋白的结构和生化研究需要毫克量的稳定、完整和均匀的蛋白质。在这里,我们描述了使用密码子优化基因筛选、表达和纯化人类溶质载体转运蛋白的可扩展方法。

Abstract

溶质载体 (SLC) 是膜转运蛋白,可导入和输出一系列内源性和外源性底物,包括离子、营养物质、代谢物、神经递质和药物。尽管这组蛋白质已成为有吸引力的治疗靶点和疾病标志物,但目前的药物仍然相对不足。这些转运蛋白的药物发现项目受到有限的结构、功能和生理知识的阻碍,最终是由于这类膜包埋蛋白的表达和纯化困难。在这里,我们展示了使用密码子优化基因序列获得高纯度、毫克量的人SLC转运蛋白的方法。结合对构建体设计和高通量表达的系统探索,这些方案确保了靶蛋白的结构完整性和生化活性的保存。我们还重点介绍了这些蛋白质的真核细胞表达、亲和纯化和尺寸排阻色谱的关键步骤。最终,该工作流程可产生纯净、功能活性和稳定的蛋白质制剂,适用于高分辨率结构测定、转运研究、小分子结合测定和高通量 体外 筛选。

Introduction

长期以来,膜蛋白一直是研究人员和制药行业的目标。其中,溶质载体 (SLC) 是一个由人类基因组中编码的 400 多个次级转运蛋白基因组成的家族1。这些转运蛋白参与许多分子的进出口,包括离子2、神经递质3、脂质4567、氨基酸8、营养素9、1011 和药物 12由于底物如此广泛,这些蛋白质还通过毒素 13 的转运、滥用药物1415 的转运和抑制或有害突变16 与一系列病理生理学有关。细菌同源物已成为几个SLC家族17,18,19,20,21,22,23,24,25的基本运输机制的原型。与人类蛋白质相比,原核直系同源物通常在众所周知的大肠杆菌表达系统26,27 中表达得更好,并且在较小的去污剂中更稳定这些去污剂产生用于 X 射线晶体学的有序晶体28。然而,序列和功能差异使这些远缘相关蛋白质用于药物发现变得复杂29,30。因此,通常需要对人类蛋白质进行直接研究,以破译靶向 SLC31、32、333435 的药物的作用机制。虽然冷冻电子显微镜 (Cryo-EM) 的最新进展使得在更天然的类似条件下对 SLC 进行结构表征36,37但表达和纯化这些蛋白质的困难仍然是开发靶向治疗和诊断的挑战。

为了缓解这一挑战,RESOLUTE联盟(re-solute.eu)开发了用于大规模表达和纯化人SLC家族蛋白的资源和方案38。从密码子优化基因开始,我们开发了用于SLC构建体的高通量克隆和筛选方法。这些方法被系统地应用于整个SLC家族,将基因克隆到BacMam病毒表达系统中,并基于先前描述的高通量克隆和表达测试方法40,在人类细胞系39中测试蛋白质表达。总之,SLC 基因从 pDONR221 质粒克隆到 pHTBV1.1 载体中。该构建体随后用于将目的基因转置到用于转染昆虫细胞的杆粒载体中,其中包括用于在哺乳动物细胞中表达的巨细胞病毒启动子和增强子元件。所得杆状病毒可用于转导哺乳动物细胞以表达靶标SLC蛋白。

我们进一步开发了用于大规模表达和稳定纯化选定SLC的标准化方法(图1)。该协议包括多个检查点,以促进有效的故障排除并最大限度地减少实验之间的差异。值得注意的是,链球菌和绿色荧光蛋白 (GFP) 标签41,42 有助于蛋白质表达和定位的常规监测以及单个靶标纯化条件的小规模优化。

最终,这些化学纯度和结构均质的蛋白质样品可用于通过 X 射线晶体学或冷冻电子显微镜 (Cryo-EM) 进行结构测定、生化靶标结合测定、免疫以生成粘合剂,以及通过复溶到化学定义的脂质体中进行无细胞功能研究。

Protocol

注:所有密码子优化的RESOLUTE SLC基因均已沉积在AddGene43中,其链接可在RESOLUTE公共试剂44列表中找到。这些基因已被克隆到 pDONR221 质粒中,并允许使用重组克隆45 将基因直接克隆到目标载体中。为了最大限度地提高平行性,细菌,昆虫和哺乳动物细胞以块形式生长,分别用于杆粒生产(第3节),杆状病毒扩增(第5节)和表达测试(第6节)。?…

Representative Results

SLC基因可以从RESOLUTE pDONR质粒克隆到BacMam载体中,用于哺乳动物表达所描述的克隆、表达和纯化方案已被证明对跨多个蛋白质折叠的许多 SLC 转运蛋白是成功的。然而,这些程序包括几个用于监测进展的检查点,允许优化以考虑表达、蛋白质折叠、脂质和去污剂依赖性稳定性以及对缓冲液条件的敏感性的差异。 SLC克隆和小规模表达过程中的检查点<b…

Discussion

由于缺乏对转运蛋白功能的系统表征,SLC靶向疗法的开发仍然受到阻碍。这导致相对于 GPCR 和离子通道63 靶向该蛋白质类别的药物不成比例地减少,尽管它们在正常和病理生理过程中具有许多作用。RESOLUTE是一个国际联盟,旨在开发尖端的研究技术和工具,以加速和改进当前的SLC研究。作为RESOLUTE的一部分,我们开发了这些方案,用于人类SLC的高效克隆、构建体筛选以及大规模表…

Divulgations

The authors have nothing to disclose.

Acknowledgements

这项工作是在RESOLUTE项目中完成的。RESOLUTE已根据第777372号赠款协议从创新药物倡议2联合承诺中获得资金。这项联合承诺得到了欧盟地平线2020研究和创新计划以及EFPIA的支持。本文仅反映作者的观点,IMI 、欧盟和 EFPIA 均不对其中所含信息的任何使用负责。pHTBV质粒由Frederick Boyce教授(哈佛大学)友情提供。

Materials

3C protease Produced in-house
50 or 100 kDa cut-off centrifugal concentrators Sartorius VS0242
5-Cyclohexyl-1-Pentyl-β-D-Maltoside Anatrace C325 CYMAL-5
96-well bacmid purification kit Millipore LSKP09604 Montage Plasmid Miniprep
96-well block (2 mL) Greiner Bio-One 780271
Adhesive plastic seals Qiagen 19570 Tape Pads
Agarose size exclusion chromatography column Cytiva 29091596 Superose 6 Increase 10/300 GL
Benzonase DNAse Produced in-house
BisTris Sigma Aldrich B9754
Cholesteryl Hemisuccinate Tris salt Anatrace CH210 CHS
Cobalt metal affinity resin Takara Bio 635653 TALON Metal Affinity Resin
D(+)-Biotin Sigma Aldrich 851209
Dextran-agarose size exclusion chromatography column Cytiva 28990944 Superdex 200 Increase 10/300 GL
Digitonin Apollo Scientific BID3301
Dounce tissue grinder (40 mL) DWK Life Sciences 357546
EDTA-free protease inhibitor cocktail Sigma Aldrich 4693132001 cOmplete, EDTA-free Protease Inhibitor Cocktail
Fetal Bovine Serum Thermo Fisher 10500064
Fos-Choline-12 Anatrace F308S FS-12
Glycerol Sigma Aldrich G5516
Glyco-diosgenin Anatrace GDN101 GDN
Gravity flow columns Cole-Parmer WZ-06479-25
HEK293 medium Thermo Fisher 12338018 FreeStyle 293 medium
HEPES Apollo Scientific BI8181
Hydrophilic, neutral silica UHPLC column Sepax 231300-4615 Unix-C SEC-300 4.6 x 150
Imidazole Sigma Aldrich 56750
Insect transfection reagent Sigma Aldrich 71259 Reagent
Lauryl Maltose Neopentyl Glycol Anatrace NG310 LMNG
Magnesium Chloride Hexahydrate Sigma Aldrich M2670
Micro-expression shaker Glas-Col 107A DPMINC24CE
NaCl Sigma Aldrich S9888
n-Decyl-β-D-Maltoside Anatrace D322 DM
n-Dodecyl-b-D-Maltopyranoside Anatrace D310 DDM
n-Dodecyl-N,N-Dimethylamine-N-Oxide Anatrace D360 LDAO
n-Nonyl-β-D-Glucopyranoside Anatrace N324S NG
n-Octyl-d17-β-D-Glucopyranoside Anatrace O311D OGNG
Octaethylene Glycol Monododecyl
Ether
Anatrace O330 C12E8
Octyl Glucose Neopentyl Glycol Anatrace NG311 OGNG
Phosphate Buffered Saline Sigma Aldrich D8537 DPBS
Polyoxyethylene(10)dodecyl Ether Anatrace AP1210 C12E10
Polyoxyethylene(9)dodecyl Ether Anatrace APO129 C12E9
Porous seal for tissue culture plates VWR 60941-084 Rayon Films for Biological Cultures
Proteinase K New England Biolabs P8107S
Recombination enzyme mix Thermo Fisher 11791020 Gateway LR Clonase II
Serum-free insect media Gibco 10902088 Sf-900 II serum-free media
Sodium Butyrate Sigma Aldrich 303410
Sonicator 24-head probe Sonics 630-0579
Sonicator power unit Sonics VCX 750
Strep-Tactin resin IBA Life Sciences 2-5030-025 Strep-TactinXT 4Flow high- capacity resin
Sucrose Sigma Aldrich S7903
Sucrose Monododecanoate Anatrace S350 DDS
Suspension-adapted HEK293 cells Thermo Fisher A14527 Expi293F
Transfection reagent Sigma Aldrich 70967 GeneJuice Transfection Reagent

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Raturi, S., Li, H., Chang, Y., Scacioc, A., Bohstedt, T., Fernandez-Cid, A., Evans, A., Abrusci, P., Balakrishnan, A., Pascoa, T. C., He, D., Chi, G., Kaur Singh, N., Ye, M., Li, A., Shrestha, L., Wang, D., Williams, E. P., Burgess-Brown, N. A., Dürr, K. L., Puetter, V., Ingles-Prieto, A., Sauer, D. B. High-Throughput Expression and Purification of Human Solute Carriers for Structural and Biochemical Studies. J. Vis. Exp. (199), e65878, doi:10.3791/65878 (2023).

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