Molecular regulation of calcium-activated (BK) potassium channels

描述（由申请人提供）：电兴奋性主要由离子通道蛋白介导，离子通道蛋白选择性地传导不同的离子。酶对离子通道的调节是赋予其生物多样性和对生理变化作出反应的核心。离子通道具有感知电信号和化学信号的能力，在多种生物系统中起着至关重要的作用。大电导钙激活（BK）钾通道受膜电位电压和细胞质钙浓度的门控。由于动作电位是膜兴奋性的核心，并且细胞内钙浓度与多种生物过程相耦合，因此BK通道的功能作用也相应多样化且具有重要意义。编码功能多样性的一个重要机制是通过孔形成亚基的选择性剪接，称为α亚基。目前对BK结构和功能的理解，几乎完全是基于一种被称为BK_ERL的c端剪接变体的研究。将天然BK通道特性与相应的BK亚基分子异构体联系起来的直接证据尚不足以完全确定ERL异构体是体内功能中最重要的形式。另一种c端剪接变体BK_DEC与通常研究的ERL形式不同，具有额外的61个氨基酸。我们现在展示了这个区域密集地挤满了功能基序，代表了一个酶组装域，招募了许多酶和调节因子。本课题旨在研究新发现的由BKJDEC组织的酶配合物。具体目的包括这些新发现的蛋白质复合物的生化，细胞生物学和功能表征。BK通道对多种生物过程至关重要，从激素分泌到神经元放电特性的控制。已经开发出药物来调节这些通道的活动，以治疗人类疾病，如中风、癫痫和其他神经系统疾病。因此，了解不同BK亚型的功能和生理对治疗具有重要意义。

DESCRIPTION (provided by applicant): Electrical excitability is primarily mediated by ion channel proteins which selectively conduct different ions. Regulation of ion channels by enzymes is central to confer their biological diversity and respond to physiological changes. The ability to sense both electrical signals and chemical signals endows an ion channel critical roles in diverse biological systems. The large conductance calcium-activated (BK) potassium channels are gated both by membrane potential voltage and by cytoplasmic calcium concentration. Because action potential is central to membrane excitability and the intracellular calcium concentration is coupled with a wide variety of biological processes, the functional roles of BK channels are accordingly diverse and of great significance. One important mechanism of coding functional diversity is through alternative splicing of pore-forming subunit, known as alpha subunit. The current understanding of BK structure and function is, almost exclusively, based on studies of one type of C-terminal splice variants known as BK_ERL. The direct evidence linking native BK channel properties and the corresponding molecular isoforms of BK subunits is not yet adequate to fully establish that the ERL isoform is the most important form for the in vivo function. Another C-terminal splice variant, BK_DEC, has additional 61 aa distinct from commonly studied ERL form. We now show this region is densely packed with functional motifs and represents an enzymatic assembly domain recruiting a number of enzymes and regulatory factors. This research proposal is aimed at investigating newly identified enzymatic complexes organized by BKJDEC. The specific aims include biochemical, cell biological and functional characterization of these newly identified protein complexes. BK channels are critical for a variety of biological processes ranging from hormone secretion to control of neuronal firing properties. Drugs have been developed to regulate these channels' activity to treat human diseases such as stroke, epilepsy and other neurological disorders. Thus, understanding of the function and physiology of different BK subtypes is of therapeutics importance.