Allosteric Regulation of Ion Channel Gating

描述（由申请人提供）：这项工作的长期目标是了解自然发生的刺激调节bk型钙（Ca2+）活化钾（K+）打开和关闭的潜在分子机制。BK通道与所有其他离子通道以及许多其他种类的蛋白质的一个共同特征是，对蛋白质一部分的生理刺激的感知与蛋白质另一部分发生的关键功能特性的调节相耦合。在BK通道的情况下，感知膜电压的变化或胞质Ca2+的变化调节通过通道的离子通量的激活。事实上，BK通道对两种不同的生理信号作出独立反应，这对于研究连接这些过程的潜在分子步骤是一个优势。

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.