Allosteric mechanisms of CA-activated K channel gating

描述(由申请人提供)：离子通道通过其打开和关闭(门)的能力来动态调节膜的通透性，以响应各种刺激。在识别和表征参与这一门控过程的部分通道蛋白方面已经取得了进展，包括检测刺激的“传感器”和调节离子通过通道孔流动的“门”。然而，关于传感器和门的作用的构象事件和相互作用仍然存在许多问题。对传感器/门通信的全面理解对于理解通道如何正常工作以及它们如何受到内源性因素、药物或疾病的调节很可能是至关重要的。为了确定传感器和门之间通信的性质，我们研究了BK型钙激活钾通道(Slo1)的功能，该通道同时感受膜电压和细胞内钙以及各种潜在的调节因子，包括细胞内镁、血红素和细胞外铜。BK通道参与重要的生理过程，其功能或表达的中断与高血压、癫痫和癌症等疾病有关。因此，对BK通道调节的了解可能对了解疾病机制和开发更有效的治疗方案具有直接意义。存在变构机制，通过这种机制，BK通道中传感器的激活和门的打开似乎代表着相互强烈影响的不同事件，但可以单独发生。SLO1为阐明传感器/门通讯的功能特性和分子机制提供了一个独特的机会。通过研究sL1对极端刺激的反应，并利用该通道特殊的运动和稳态特性，我们能够孤立地研究传感器的激活、通道的开放以及传感器和门之间的耦合。这些方法和分析工具将被应用于突变的Slo1通道，以确定参与传感器/门通信的残基和相互作用，并了解镁2、血红素和Cu2如何调节BK通道活性。这些结果不仅对于理解BK通道的门控和生理调节，而且对于阐明传感器和门控是如何耦合的，以及门控在其他离子通道中是如何调节的，都将是重要的。

DESCRIPTION (provided by applicant): Ion channels dynamically regulate membrane permeability through their ability to open and close (gate) in response to various stimuli. Progress has been made in identifying and characterizing parts of channel proteins that are involved in this gating process including "sensors" that detect stimuli, and "gates" that regulate the flow of ions through the channel pore. However many questions remain concerning the conformational events and interactions that couple the action of sensors and gates. A comprehensive understanding of sensor/gate communication is likely to be of fundamental importance in understanding how channels normally work and how they are modulated by endogenous factors, drugs, or disease. To determine the nature of communication between sensors and gates we have studied the function of the BK-type Ca2+- activated K+ Channel (Slo1); a channel that senses both membrane voltage and intracellular Ca2+ as well as a variety of potential regulatory factors including intracellular Mg2+, Heme, and extracellular Cu2+. BK channels participate in physiologically important processes, and disruptions in their function or expression have been associated with diseases such as hypertension, epilepsy and cancer. Therefore an understanding of BK channel regulation may have direct implications for understanding disease mechanisms and developing more effective therapeutic options. Allosteric mechanisms exist by which the activation of sensors and the opening of the gate in BK channels appear to represent distinct events that strongly influence each other but can occur in isolation. Slo1 offers a unique opportunity to elucidate the functional properties and molecular mechanisms of sensor/gate communication. By studying the response of Slo1 to extreme stimuli and taking advantage of particular kinetic and steady-state properties of this channel we are able to study, in isolation, sensor activation, channel opening, and the coupling between sensor and gate. These methods and analytical tools will be applied to mutant Slo1 channels to identify residues and interactions that are involved in sensor/gate communication, and to understand how Mg2+, Heme and Cu2+ regulate BK channel activity. The results will be important, not only for understanding the gating and physiological regulation of BK channels, but also for elucidating how sensors and gates are coupled and gating is regulated in other ion channels.