BK channel regulation by auxiliary LRR proteins

项目摘要：可变辅助亚基对离子通道的调节是 在不同的组织和组织中产生离子通道功能的多样性，从而产生电信号的可变性 细胞。大电导、钙和电压激活的钾(BK)通道普遍表达 并关键地参与各种细胞和生理过程，包括神经元的调节 几乎所有类型的平滑肌细胞的兴奋性和突触传递以及收缩张力的控制。 由于几种组织特异性辅助β和的存在，BK通道的结构和功能多样化 亚单位。自从我们首次鉴定了富含亮氨酸重复序列(Lrrc)的膜蛋白以来 LRRC26作为BK通道的辅助1亚基，在成百上千个LRRC蛋白中不断增加 在人类蛋白质数据库中，已发现lrrc蛋白具有离子调节蛋白的功能。 频道。目前，大多数调节者对离子通道的调控机制知之甚少。 IRRC蛋白。BK通道辅助1亚单位具有非典型的“全有或全无”的特征 调制作用，一个异常大的能力，影响BK通道的电压门控，预计 电压传感器激活和通道开孔之间的变构耦合的主要影响因素，以及 与小分子BK通道激活剂马洛毒素(Rotlerin)的竞争关系。基于我们的 以前和现在的研究，我们假设辅助1亚单位通过中枢调节BK通道 膜内机制，以及辅助的细胞外和细胞内机制。测试我们的 假设并阐明辅助亚基调节BK通道的分子机制 建议追求以下3个具体目标：1)确定非典型的“要么全或全”的分子基础。 1亚基在BK通道调制中的“无”作用；2)确定BK的分子机制 涉及跨膜结构域的1亚基对通道的调制；3)确定分子 1亚基和马洛毒素对BK通道的调控机制涉及细胞质结构域。这个 这项拨款申请中的拟议研究旨在系统地研究生物化学和 辅助1亚基和马洛毒素调控BK通道的生物物理机制。这个 本研究所获得的知识可应用于其他调节性LRRC的离子通道调节 蛋白质。拟议的研究结果将有助于阐明BK通道电压门控的机制 并深入了解1亚基的非典型“全有或全无”行为和 调制BK通道电压门控。他们还将帮助创造新的靶向治疗试剂 BK通道在治疗或预防神经生物学、心血管和其他类型的疾病以及 疾病。

PROJECT SUMMARY: Ion channel regulation by variable auxiliary subunits is a major mechanism in generating diversity of ion channel function and thus variability in electrical signaling in different tissues and cells. Large conductance, calcium- and voltage-activated potassium (BK) channels are ubiquitously expressed and critically involved in various cellular and physiological processes including regulation of neuronal excitability and synaptic transmission and control of contractile tone of almost all types of smooth muscle cells. BK channels are diversified in structure and function by the presence of several tissue specific auxiliary β and  subunits. Since our initial identification of the leucine-rich repeat containing (LRRC) membrane protein LRRC26 as the BK channel auxiliary 1 subunit, an increasing number of LRRC proteins, among hundreds of LRRC proteins in the human protein database, have been found to function as regulatory proteins of ion channels. Currently, little is known about the mechanisms underlying ion channel regulation by most regulatory LRRC proteins. The BK channel auxiliary 1 subunit have characteristics of an atypical “all-or-none” modulatory action, an exceptionally large capability in affecting the BK channel’s voltage-gating, a predicted major effect on the allosteric coupling between the voltage sensor activation and channel pore-opening, and a competitive relationship with a small molecule BK channel activator mallotoxin (rottlerin). Based on our previous and current studies, we hypothesize that the auxiliary 1 subunit modulates BK channels via a central intramembrane mechanism and also subsidiary extracellular and intracellular mechanisms. To test our hypothesis and elucidate the molecular mechanisms of BK channel modulation by auxiliary  subunits, we propose to pursue the following 3 specific aims: 1) determine the molecular basis underlying an atypical “all-or- none” action of the 1 subunit on BK channel modulation; 2) determine the molecular mechanisms of BK channel modulation by the 1 subunit involving transmembrane domains; 3) determine the molecular mechanisms of BK channel modulation by the 1 subunit and mallotoxin involving cytoplasmic domains. The proposed research in this grant application is designed to systematically investigate the biochemical and biophysical mechanisms governing BK channel regulation by the auxiliary 1 subunit and mallotoxin. The knowledge obtained in this study could be applicable to ion channel regulation by other regulatory LRRC proteins. The findings from the proposed studies will shed light on mechanisms of BK channel voltage gating and provide in-depth understanding of the 1 subunit’s atypical “all-or-none” action and exceptional capability in modulating BK channel voltage-gating. They will also help in creation of novel therapeutic reagents targeting BK channels in treatment or prevention of neurobiological, cardiovascular, and other types of disorders and diseases.