用于蛋白质磷酸化定量的优化单分子下拉测定
Summary
本方案描述了样品制备和数据分析，以使用改进的单分子下拉（SiMPull）测定来量化蛋白质磷酸化。
Abstract
磷酸化是一种必要的翻译后修饰，可调节蛋白质功能并指导细胞信号传导结果。目前测量蛋白质磷酸化的方法不能保持单个蛋白质磷酸化的异质性。单分子下拉（SiMPull）测定是通过在玻璃盖玻片 上免疫沉淀 蛋白质然后进行单分子成像来研究大分子复合物的组成。目前的技术是对SiMPull的改编，可在单分子水平上对全长膜受体的磷酸化状态进行强有力的定量。以这种方式对数千个个体受体进行成像可以量化蛋白质磷酸化模式。本实验方案详细介绍了优化的SiMPull程序，从样品制备到成像。玻璃制备和抗体固定方案的优化进一步提高了数据质量。目前的方案为单分子数据分析提供了代码，该数据分析计算样品中磷酸化的受体的比例。虽然这项工作的重点是表皮生长因子受体（EGFR）的磷酸化，但该方案可以推广到其他膜受体和胞质信号分子。
Introduction
膜相关信号传导通过配体诱导的膜受体激活和募集传播信号的下游辅助蛋白的组合进行调整。受体细胞质尾部中关键酪氨酸的磷酸化对于启动信号复合物或信号体1，2的形成至关重要。因此，生物学中的一个重要问题是如何创建和维护磷酸化模式以招募信号伙伴并决定细胞结果。这包括了解受体磷酸化的异质性，无论是在丰度上还是在特定的磷酸酪氨酸模式中，都可以通过决定信号体3，4，5，6，7的组成来提供操纵信号输出的方法。然而，目前询问蛋白质磷酸化的方法存在局限性。蛋白质印迹分析非常适合描述蛋白质磷酸化的趋势，但半定量8，并且不能提供有关系统异质性的信息，因为数千到数百万个受体被平均在一起。虽然蛋白质印迹允许使用磷酸特异性抗体对特定酪氨酸进行探查样品，但它们不能提供有关同一蛋白质内多位磷酸化模式的信息。定量磷酸化蛋白质组学报告了磷酸酪氨酸丰度，但检测多位磷酸化存在局限性，因为感兴趣的残基需要位于酶消化产生的相同肽（通常为7-35个氨基酸）内9，10，11。
为了克服上述限制，单分子下拉（SiMPull）测定已被调整为在单分子水平上量化完整受体的磷酸化状态。SiMPull首先被耆那教等人证明是询问大分子复合物的强大工具。12，13。在SiMPull中，在抗体功能化玻璃盖玻片上对大分子复合物进行免疫沉淀（IP），然后通过单分子显微镜分析蛋白质亚基数和与复合组分12的共IP。Kim等人14的一项修改，称为SiMBlot，是第一个使用SiMPull的变体来分析变性蛋白质的磷酸化。SiMBlot方案依赖于使用NeutrAvidin包被的盖玻片捕获生物素化的细胞表面蛋白，然后用磷酸特异性抗体标记14探测磷酸化。尽管取得了这些进展，但仍需要改进，以使翻译后修饰的定量更加稳健，并适用于更广泛的蛋白质。
本方案描述了一种优化的SiMPull方法，该方法用于量化完整表皮生长因子受体（EGFR）的磷酸化模式，以响应一系列配体条件和致癌突变15。虽然这项工作侧重于EGFR，但这种方法可以应用于任何膜受体和感兴趣的胞质蛋白（POI），其具有高质量的抗体。该协议包括减少样品自发荧光的步骤，需要最小样品体积的样品阵列设计，同时制备多达20个样品，以及优化抗体标记和固定条件。已经开发了用于磷酸化蛋白的单分子检测和定量的数据分析算法。
Protocol
1. 盖玻片准备 注意：对于此步骤，需要穿戴个人防护装备（PPE），其中包括双层丁腈手套，安全眼镜或面罩以及实验室外套。 进行食人鱼蚀刻以清除玻璃上的有机碎屑。注意：食人鱼溶液是一种强氧化剂，与有机材料接触时具有腐蚀性和高度反应性。与有机碎片的反应是放热的，具有潜在的爆炸性。因此，该过程必须在降低窗扇的化学通风橱中进行。…
Representative Results
图 1A显示了一幅描绘SiMPull过程的卡通。使用新链阿维丁作为生物素化抗EGFR抗体的锚点，从总蛋白裂解物中捕获EGFR-GFP，盖玻片被功能化。洗去未结合的蛋白质后，磷酸化的受体用抗磷酸酪氨酸（anti-PY）抗体15标记。 图1B 显示了疏水阵列的图像，其中可以制备多个样品并在同一盖玻片上成像。该样品架的一个优点是需要~10 μL的最小样?…
Discussion
这里描述的方案经过优化，可以在单一蛋白质水平上定量测量受体磷酸化。对SiMPull方案进行了一些简单但重要的修改，提高了磷酸酪氨酸检测测量的可靠性，包括通过NaBH4 处理减少自发荧光和后固定样品以防止抗体解离。使用绿色通道掩模识别受体位置以计算与抗PY抗体的共定位，还可以通过消除抗体与细胞裂解物的非特异性结合中的潜在伪影来提高测量精度。利用双色成像来检测磷酸?…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
这项工作得到了美国国立卫生研究院R35GM126934，R01AI153617和R01CA248166的支持。EMB通过阿塞特-伊拉克开发区计划（NIH K12GM088021）和UNM MARC计划（NIH 2T34GM008751-20）提供支持。我们非常感谢使用新墨西哥大学综合癌症中心荧光显微镜共享资源，由NIH P30CA118100支持。我们要感谢安库尔·贾恩博士和哈太基吉普博士，他们最初对SiMPull的开发启发了这项工作。
ES-C现在地址：免疫动力学组，综合癌症免疫学实验室，癌症研究中心，国家癌症研究所，贝塞斯达
Materials
| 1.5 mL microcentrifuge tubes | MTC Bio | C2000 | |
| 10 mM Tris-HCl pH 7.4 | |||
| 10 mM Tris-HCl pH 8.0/ 50 mM NaCl | T50 Buffer | ||
| 100 mm Tissue Culture dish | CELLTREAT | 229620 | Storage of piranha etched glass/arrays |
| 15 mL conical tube | |||
| 16% Paraformaldehyde Aqueous Solution | Electron Microscopy Sciences | 15710 | Hazardous |
| 50 mL conical tube | Functionalized Glass storage/ KOH reuse | ||
| 50 mM Tris-HCl pH 7.2/150 mM NaCl | Lysis Buffer Component | ||
| 60 mm Tissue Culture dish | Corning | 430166 | |
| 8% Glutaraldehyde Aqueous Solution | Electron Microscopy Sciences | 16020 | Hazardous |
| Acetone (C3H6O) | Millipore Sigma | 270725 | Hazardous |
| Alexa Fluor 647 NHS Ester | Thermo Fisher Scientific | A-20006 | |
| Animal-Free Recombinant Human EGF | Peprotech | AF-100-15 | |
| Anti-Human EGFR (External Domain) – Biotin | Leinco Technologies, Inc | E101 | |
| Anti-p-Tyr Antibody (PY99) Alexa Fluor 647 | Santa Cruz Biotechnology | sc-7020 AF647 | |
| Bath-sonicator | Branson | 1200 | |
| BCA Protein Assay Kit | Pierce | 23227 | |
| Biotin-PEG | Laysan Bio | Biotin-PEG-SVA, MW 5,000 | |
| Bovine serum albumin | Gold Biotechnology | A-420-1 | Tyrode's Buffer Component |
| Buchner funnel | |||
| Bunsen burner | |||
| Calcium Chloride (CaCl2) | Millipore Sigma | C4901 | Tyrode's Buffer Component |
| Cell Scraper | Bioworld | 30900017-1 | |
| Conical Filtering Flask | Fisher Scientific | S15464 | |
| Coplin Jar | WHEATON | 900470 | |
| Countess II Automated Cell Counter | Thermo Fisher Scientific | AMQAX1000 | |
| Coverslips 24 x 60 #1.5 | Electron Microscopy Sciences | 63793 | |
| DipImage | https://diplib.org/ | ||
| DMEM | Caisson Labs | DML19-500 | |
| emCCD camera | Andor iXon | ||
| Fetal Bovine Serum, Optima | Bio-Techne | S12450H | Heat Inactivated |
| Fusion 360 software | Autodesk | ||
| Geneticin G418 Disulfate | Caisson Labs | G030-5GM | |
| Glacial Acetic Acid (CH3COOH) | JT Baker | JTB-9526-01 | Hazardous |
| Glass serological pipettes | |||
| Glass Stir Rod | |||
| Glucose (D-(+)-Glucose) | Millipore Sigma | D9434 | Tyrode's Buffer Component |
| Halt Phosphotase and Protease Inhibitor Cocktail (100X) | Thermo Fisher Scientific | 78446 | Lysis Buffer Component |
| HEPES | Millipore Sigma | H3375 | Tyrode's Buffer Component |
| Hydrochloric Acid (HCl) | VWR | BDH7204-1 | Hazardous |
| Hydrogen Peroxide (H2O2) (3%) | HX0645 | ||
| Hydrogen Peroxide (H2O2) (30%) | EMD Millipore | HX0635-2 | |
| Ice | |||
| IGEPAL CA-630 (NP-40) | Sigma Aldrich | I8896 | Lysis Buffer Component |
| ImmEdge Hydrophobic Barrier Pen | Vector Laboratories | H-4000 | |
| Immersol 518F immersion oil | Zeiss | 444960-0000-000 | |
| in-house vacuum line | |||
| L-glutamine | Thermo Fisher Scientific | 25030-164 | |
| Magnessium Chloride Hexahydrate (MgCl2-6H2O) | MPBio | 2191421 | Tyrode's Buffer Component |
| Matlab | Mathworks | Curve Fitting Toolbox, Parallel Computing Toolbox, and Statistics and Machine Learning toolbox | |
| Methanol (CH3OH) | IBIS Scientific | MX0486-1 | Hazardous |
| Milli-Q water | |||
| Mix-n-Stain CF Dye Antibody Labeling Kits | Biotium | 92245 | Suggested conjugation kit |
| mPEG | Laysan Bio | mPEG-succinimidyl valerate, MW 5,000 | |
| N-(2-aminoethyl)-3-aminopropyltrimethoxysilane | UCT United Chemical | A0700 | Hazardous |
| Nanogrid | Miraloma Tech | ||
| NeutrAvidin Biotin Binding Protein | Thermo Fisher Scientific | 31000 | |
| Nitrogen (compressed gas) | |||
| NVIDIA GPU with CUDA | Look for compatibility at https://www.mathworks.com/help/parallel-computing/gpu-support-by-release.html | ||
| Olympus iX71 Microscope | Olympus | ||
| Parafilm M Sealing Film | The Lab Depot | HS234526C | |
| PBS pH 7.4 | Caisson Labs | PBL06 | |
| PC-200 Analog Hot Plate | Corning | 6795-200 | |
| Penicillin-Streptomycin (10,000 U/mL) | Thermo Fisher Scientific | 15140-163 | |
| Phospho-EGF Receptor (Tyr1068) (1H12) Mouse mAb | Cell Signaling Technology | 2236BF | |
| Potassium Chloride (KCl) | Millipore Sigma | 529552 | Tyrode's Buffer Component |
| Potassium Hydroxide (KOH) | Millipore Sigma | 1050330500 | Hazardous |
| Premium PLA Filament, 1.75 mm diameter | Raise 3D | PMS:2035U/RAL:3028 | Printing temperature range: 205-235 °C |
| Pro2 3D printer | Raise 3D | ||
| Pyrex 1 L beaker | |||
| PYREX 100 mL storage bottles | Corning | 1395-100 | CH3OH/C3H6O reuse |
| Pyrex 250 mL beakers | |||
| Pyrex 4 L beaker | |||
| Quad-view Image Splitter | Photometrics | Model QV2 | |
| Refrigerated centrifuge | Eppendorf | EP-5415R | |
| RevCount Cell Counters, EVE Cell Counting Slides | VWR | 10027-446 | |
| Semrock emission filters: blue (445/45 nm), green (525/45 nm), red (600/37 nm), far-red (685/40 nm) | Semrock | LF405/488/561/635-4X4M-B-000 | |
| Serological pipette controller | |||
| Serological Pipettes | |||
| smite single molecule analysis package | https://github.com/LidkeLab/smite.git | ||
| Sodium Bicarbonate (NaHCO3) | Sigma Aldrich | S6014 | Hazardous |
| Sodium Borohydride (NaBH4) | Millipore Sigma | 452874 | Tyrode's Buffer Component |
| Sodium Chloride (NaCl) | Millipore Sigma | S9625 | Activate by successive heat and pH cycling |
| Sodium Hydroxide | VWR | BDH3247-1 | |
| Sodium Orthovanadate (Na3VO4) | Millipore Sigma | S6508 | Hazardous |
| Sulfuric Acid (H2SO4) | Millipore Sigma | 258105 | Hazardous |
| TetraSpeck Microspheres | Thermo Fisher Scientific | T7279 | multi-fluorescent beads |
| Tris (Trizma) base | Millipore Sigma | T1503 | |
| Trypan blue stain, 0.4% | Thermo Fisher Scientific | 15250061 | |
| Trypsin-EDTA 0.05% | Thermo Fisher Scientific | 25300120 |
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Citazione di questo articolo
Bailey, E. M., Salazar-Cavazos, E., Grattan, R. M., Wester, M. J., Schodt, D. J., Rojo, J. A., Lidke, K. A., Lidke, D. S. An Optimized Single-Molecule Pull-Down Assay for Quantification of Protein Phosphorylation. J. Vis. Exp. (184), e63665, doi:10.3791/63665 (2022).