Quantitative label-free imaging of membrane protein interaction kinetics on cells

描述（由申请人提供）：嵌入或附着在细胞膜上的蛋白质执行许多至关重要的生物学功能，包括细胞信号传导、通信和将重要物质转运进出细胞。它们也是最重要的药物靶标和疾病生物标志物。尽管重要，研究膜蛋白，特别是量化它们与其他分子（如候选药物）的相互作用，一直是一个艰巨的挑战。目前的方法依赖于用荧光标签标记蛋白质或从其天然膜环境中提取它们，然后将它们纯化并固定在表面上用于结合动力学研究。前者是一种终点分析法，不能提供定量蛋白质相互作用所需的动力学信息，而后者不仅劳动密集，而且容易改变天然结构 和膜蛋白的功能。 该项目的重点是开发一种新的技术，用于研究和量化膜蛋白在其天然细胞环境中的相互作用，而无需提取，纯化或固定。该技术的核心是PI实验室最近发明的基于等离子体的电阻抗显微镜（P-EIM），它具有以下几个独特的功能：1）它是无标记的，可以提供定量分析， 结合动力学; 2）它具有高空间分辨率（亚微米），因此适用于分析单细胞的膜蛋白结合活性，并用于绘制单细胞内膜蛋白的局部结合动力学; 3）它是快速的（毫秒时间分辨率），这使得能够实时跟踪由小分子与膜蛋白结合触发的细胞信号转导级联。此外，该技术允许同时进行等离子体、阻抗和荧光成像，并将这些方法的优点结合在一个系统中。

DESCRIPTION (provided by applicant): Proteins embedded in or attached to cell membranes perform many critically important biological functions, including cell signaling, communication and the transport of vital substances into and out of cells. They are also the most important drug targets and disease biomarkers. Despite the importance, studying membrane proteins, especially quantifying their interactions with other molecules, such as drug candidates, has been a difficult challenge. Current methods rely on either labeling the proteins with fluorescent tags or extracting them from their native membrane environment, and then purifying and immobilizing them on a surface for binding kinetic studies. The former approach is an end-point-assay, which does not provide kinetics information required for quantifying protein interactions, while the latter is not only labor-intensive but also prone to alternation of the native structures and functions of the membrane proteins. This project focuses on developing a novel technique for studying and quantifying membrane protein interactions in their native cellular environment without the need of extraction, purification, or immobilization. The core of the technique is plasmonic-based electrical impedance microscopy (P-EIM) recently invented in the PIs' lab, which has several unique capabilities: 1) It is label free and can provide quantitative analysis of binding kinetics; 2) It has a high spatial resolution (sub-microns), and thus is suitable for analyzing membrane protein binding activities of single cells, and for mapping local binding kinetics of membrane proteins within a single cell; 3) It is fast (millisecond time resolution), which enables real-time tracking of cell signal transduction cascade triggered by small molecule binding to membrane proteins. Additionally, the technique allows for simultaneous plasmonic, impedance and fluorescence imaging, and combines the strengths of these methods in one system.