Evolutionary Biophysics of Slo3 Potassium Channels

 描述（由申请人提供）：钾离子被身体用于建立跨细胞膜的电势。这种电势被用作驱动分子进出细胞的能量，最著名的是驱动神经系统的电活动。钾通道是允许这些重要离子穿过膜的蛋白质，其结构和功能在60年的生物物理和结构研究中是众所周知的。钾通道的一个值得注意的组，称为Slo通道，打开和关闭取决于膜电压和各种细胞内离子的浓度。这些通道涉及生理学的各种要素，包括神经活动的时间，内耳的功能，平滑肌收缩和精子获能。Slo通道中的突变与癫痫相关，并且它们是用于各种医学目的的潜在药物靶点。 在Slo家族中， 了解通道Slo1，也称为BK通道，与最不了解的通道Slo3密切相关。尽管这两种通道类型密切相关，但它们受到不同细胞内离子的影响，并在不同组织中表达。Slo1对细胞内钙敏感，而Slo3似乎主要对pH敏感。Slo3主要在小鼠中表征，然而，目前的研究表明人类Slo3可能与小鼠非常不同。关于Slo3中质子结合的位点也有许多悬而未决的问题。我提出的工作使用了一种与Slo3研究中迄今为止所采用的方法不同的方法。我建议采用比较和进化的方法，而不是研究几种模式生物，来重建Slo3与Slo1不同的故事。 我使用比较基因组学和遗传学来了解Slo3的新知识，并对其功能的分子基础提出预测性假设。与目前认为Slo3只存在于哺乳动物中的观点相反，我在鸟类和爬行动物的基因组中发现了Slo3基因。为了重建Slo3的历史，我使用进化的统计模型预测了现存Slo3通道的祖先的序列。这些新的渠道，现存的和祖先的，告诉一个预测的故事，如何Slo3从Slo1失去已知的钙结合位点和获得新的网站，可能会感测细胞内pH值。我建议的工作将测试这些假设使用异源表达和生物物理学。这项工作将在理查德·奥尔德里奇博士的实验室完成，他对Slo通道功能的当前知识做出了很大贡献。

 DESCRIPTION (provided by applicant): Potassium ions are used by the body to build up an electrical potential across cellular membranes. This potential is used as energy to drive the movement of molecules into and out of cells, and, most famously, to drive the electrical activity that characterizes the nervous system. Potassium channels are the proteins that allow these important ions across the membrane, and their structure and function are well known from 60 years of biophysical and structural research. One notable group of potassium channels, known as Slo channels, opens and closes depending on both the membrane voltage and the concentration of various intracellular ions. These channels are involved in diverse elements of physiology, including the timing of neural activity, the function of the inner ear, smooth muscle contraction, and sperm capacitation. Mutations in Slo channels are associated with epilepsy, and they are potential drug targets for a variety of medical purposes. In the Slo family, the best understand channel, Slo1, also called the BK channel, is closely related to the least well understood channel, Slo3. Despite being closely related, the two channel types are affected by different intracellular ions and are expressed in different tissues. Slo1 is sensitive to intracelllar calcium, while Slo3 appears to be primarily sensitive to pH. Slo3 has primarily been characterized in mice, however, and current research suggests human Slo3 might be very different from mice. There are also many outstanding questions about the locus of proton binding in Slo3. My proposed work uses a different approach than the one taken so far in Slo3 research. Rather than look in a few model organisms, I propose to take a comparative and evolutionary approach that can reconstruct the story of how Slo3 came to be different from Slo1. I have used comparative genomics and phylogenetics to learn new things about Slo3 and generate predictive hypotheses about the molecular basis of its function. Contrary to the current belief that Slo3 exists only in mammals, I have found Slo3 genes in the genomes of birds and reptiles. To reconstruct the history of Slo3, I predicted the sequence of the ancestors of extant Slo3 channels using statistical models of evolution. These new channels, extant and ancestral, tell a predictive story of how Slo3 differentiated from Slo1 by losing known calcium binding sites and acquiring new sites that may sense intracellular pH. My proposed work will test these hypotheses using heterologous expression and biophysics. The work will be done in the laboratory of Dr. Richard Aldrich, who has contributed much of the current knowledge of Slo channel function.