Molecular regulation of calcium-activated (BK) potassium channels

描述(申请人提供)：电兴奋性主要由离子通道蛋白介导，它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做出反应的核心。同时感知电信号和化学信号的能力赋予了离子通道在不同生物系统中的关键作用。大电导钙激活(BK)钾通道受膜电位和细胞内钙离子浓度的调节。由于动作电位是膜兴奋性的中心，细胞内钙离子浓度与多种生物过程相耦合，因此BK通道的功能作用是多样的，具有重要的意义。编码功能多样性的一个重要机制是通过孔道形成亚基的选择性剪接，即众所周知的阿尔法亚基。目前对BK结构和功能的了解几乎完全基于对一种称为BK_ERL的C-末端剪接变体的研究。将天然BK通道的性质与BK亚基的相应分子亚型联系起来的直接证据尚不足以充分证明ERL亚型是体内功能最重要的形式。另一个C-末端剪接变异体BK_DEC，与通常研究的ERL形式不同，另外有61个氨基酸。我们现在表明，这个区域密集地充满了功能基序，代表了一个酶组装区域，招募了许多酶和调节因子。这项研究计划旨在研究由BKJDEC组织的新发现的酶复合体。具体目标包括这些新发现的蛋白质复合体的生化、细胞生物学和功能表征。BK通道在从激素分泌到控制神经元放电特性的各种生物学过程中都是至关重要的。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、癫痫和其他神经疾病。因此，了解不同BK亚型的功能和生理学具有重要的治疗意义。

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.