Allosteric Regulation of Ion Channel Gating

描述(申请人提供)：这项工作的长期目标是了解潜在的分子机制，通过自然发生的刺激调节BK型钙(钙)激活的钾(K+)的打开和关闭。BK通道与几乎所有其他离子通道以及许多其他类别的蛋白质的一个共同特征是，对蛋白质一个部分的生理刺激的感知与对该蛋白质另一部分发生的关键功能特性的调节是耦合的。在BK通道中，对膜电压或胞浆钙离子变化的感知调节着通过该通道的离子通量的激活。BK通道独立地对两种不同的生理信号作出反应，这一事实对于研究连接这些过程的潜在分子步骤是一个优势。 这个项目将特别关注BK通道激活如何调节的两个主要方面。首先，我们将研究通道选择性过滤器区域的构象变化在通道激活中的作用。这里，我们将研究选择性滤光片选通是如何与电压变化或钙离子升高相耦合的。其次，我们将考察影响配体结合和通道激活之间耦合的BK通道的结构特征。利用电生理学和分子生物学相结合的方法，该项目将利用两个密切相关的离子通道，BK通道和它的pH调节同系物Slo3。可以利用这两个通道之间的重要功能差异来定位导致功能差异的基因座。结合机理分析，可以定义有关门控和配体依赖之间耦合的信息。这些问题共同解决了可能对各种离子通道具有广泛意义的重要的一般性问题。 BK通道在多种可兴奋细胞的正常功能中具有广泛的重要性。BK通道通过响应细胞内钙离子的升高和膜电位的变化，在细胞兴奋性的调节中发挥重要作用。在不同的组织中，BK通道参与神经元兴奋性、平滑肌松弛、突触传递和激素释放的调节。更好地了解BK通道功能的调节具有潜在的医学意义，不仅因为这些通道可能作为特定的治疗靶点，还因为特定变异体的功能改变可能导致未知的病理情况。

DESCRIPTION (provided by applicant): The long-term aim of this work is to understand the underlying molecular mechanisms by which naturally occurring stimuli regulate the opening and closing of the BK-type calcium (Ca2+)-activated potassium (K+). A common characteristic shared by BK channels with essentially all other ion channels and also many other categories of protein is that sensing of a physiological stimulus on one part of the protein is coupled to regulation of a key functional property occurring on another part of that protein. In the case of BK channels, sensing of either changes in membrane voltage or changes in cytosolic Ca2+ regulate the activation of ion flux through the channel. The fact that BK channels respond independently to two distinct physiological signals has been an advantage for investigation of the underlying molecular steps that link these processes. This project will focus specifically on two major aspects of how activation of BK channels is regulated. First, the role of conformational changes in the selectivity filter region of the channel in channel activation will be examined. Here, how selectivity filter gating is coupled to either voltage changes or Ca2+ elevations will be examined. Second, the structural features of BK channels that influence coupling between ligand binding and channel activation will be examined. Using methods of electrophysiology combined with molecular biology, this project will take advantage of two closely related ion channels, the BK channel and its pH-regulated homologue, Slo3. Important functional differences between these two channels can be exploited to map the loci responsible for the functional difference. Coupled with mechanistic analyses, information regarding the coupling between gating and ligand dependence can be defined. Together these questions address important general issues that are likely to have broad significance to a wide variety of ion channels. BK channels are of broad importance in the normal functioning of a variety of excitable cells. By responding to both elevations in cytosolic Ca2+ and changes in membrane potentials, BK channels play an important role in the regulation of cellular excitability. Among different tissues, BK channels contribute to regulation of neuronal excitability, smooth muscle relaxation, synaptic transmission and hormone release. Better understanding of the regulation of BK channel function is of potential medical importance, not only because the channels may serve as specific therapeutic targets but also because altered function of particular variants may contribute to unknown pathological conditions.