Mechanism of Chloride Conduction in the CFTR Anion Channel

我们身体中的每个细胞都被一层薄膜包围着，这层薄膜形成了一道屏障，将细胞的内容物与环境隔开。为了跨越这一屏障，小物质必须使用存在于膜中的蛋白质分子。一个例子是一种名为cftr的蛋白质，它控制着盐和水进出细胞的运动。当这种蛋白质不能正常工作时，就会导致致命的囊性纤维化。我实验室的研究使用精确的电子记录技术来研究氯离子的运动，氯离子是盐的一种成分，当它们通过CFTR并穿过细胞膜时。这些电子记录是如此精确，以至于我们能够检测和研究单个CFTR蛋白分子在细胞膜上进行正常活动时的氯运输。我们希望了解CFTR如何以极快的速度移动氯离子，同时不允许其他类似的小离子通过，这一过程被称为不同离子之间的“选择性”。我们认为，CFTR蛋白中一定有特定的部分能够识别氯离子，并以这种方式“选择”它们进行跨膜运输。为了了解CFTR蛋白质分子的工作原理，我们利用实验室分子生物学技术，通过将设计好的变化引入其基因来改变其结构。然后将正常的和“设计的”改变形式的CFTR引入实验室培养中的细胞中。这使我们能够利用电子记录，详细地计算出CFTR的结构如何决定其运输氯化物的能力。我们特别感兴趣的是了解CFTR蛋白是如何识别氯离子的，以及一旦它们被选中，它们是如何如此快速地跨膜运输的。我们认为，氯离子必须沿其移动才能跨膜的途径中有不止一部分作为氯离子识别位点，并且存在于这条途径中不同位置的氯离子必须以某种方式能够感知彼此的存在，以便继续它们通过CFTR和跨膜的旅程。这项拟议的研究旨在了解氯识别和快速氯运输的这些过程，这是这种重要蛋白质正常工作的核心方面。其他氯转运蛋白也存在，我们希望我们对CFTR的了解也有助于了解这些其他转运蛋白是如何工作的。

Each cell in our body is surrounded by a thin membrane that forms a barrier that separates the cell's contents from its environment. To cross this barrier, small substances have to use protein molecules that are present in the membrane. One example is a protein called CFTR, which controls salt and water movement in and out of cells. When this protein does not work properly, this results in the fatal disease cystic fibrosis. Research in my lab uses precise electrical recording techniques to study the movement of chloride ions, one component of salt, as they move through CFTR and across the cell membrane. These electrical recordings are so precise that we are able to detect and study chloride transport by a single CFTR protein molecule undergoing its normal activity in the cell membrane. We hope to understand how CFTR moves chloride ions extremely rapidly while at the same time not allowing other, similar small ions to pass through, a process known as “selectivity” between different ions. We believe that there must be specific parts of the CFTR protein that are able to recognize chloride ions and in this way “select” them for transport across the membrane. To understand how the CFTR protein molecule works, we change its structure by introducing designed changes into its gene using techniques of laboratory molecular biology. Normal and “designer” altered forms of CFTR are then introduced into cells growing in culture in the lab. This allows us to figure out, in fine detail, how the structure of CFTR determines its ability to transport chloride, using electrical recordings. We are particularly interested in understanding how the CFTR protein recognizes chloride ions, and once they have been selected, how they are transported across the membrane so quickly. We believe that more than one part of the pathway that chloride ions must move along to cross the membrane acts as a chloride recognition site, and that chloride ions present at different places within this pathway must somehow be able to sense one another's presence in order to continue their journey through CFTR and across the membrane. The proposed research is aimed at understanding these processes of chloride recognition and rapid chloride transport, central aspects to the normal job of this important protein. Other chloride transporting proteins also exist, and we expect much of what we learn about CFTR to also help understand how these other transport proteins work.