Delineation of a LRR family of BK channel auxiliary subunits

描述（由申请人提供）：大电导，钙和电压激活钾（BK）通道是钾通道家族的独特成员，具有最大的单通道电导，并由电压和胞质游离Ca2+ ([Ca2+]i)双重激活，由孔隙形成，电压和Ca2+感应亚基（BK）组成，单独或与组织特异性调节亚基相关（1 - 4）。BK通道通常难以打开，需要同时膜去极化和[Ca2+]i升高才能在体内激活。然而，通过蛋白质组学和电生理学的方法，我们最近发现了一种新的BK通道辅助亚基，富含亮氨酸的重复序列（LRR）含有膜蛋白LRRC26，它在电压依赖性中引起前所未有的大负位移（~ -150 mV），允许BK通道在接近静息电压和钙水平时激活，在可兴奋和不可兴奋的细胞中。LRRC26代表了一个新的BK通道辅助亚基家族，它在结构上与四个已知的-亚基不同，被称为-亚基。就像存在多种具有不同调节功能的组织特异性BK通道亚基一样，我们假设存在lrrc26样亚基的其他成员，它们在广泛的不同细胞类型中差异调节BK通道。以下两个具体目标旨在描述BK通道亚单元的家族成员并定义其结构和功能特征：1)识别和表征BK通道亚单元的新成员；2)确定BK通道-亚基调节功能的结构决定因素。我们从蛋白数据库中鉴定出LRRC26的5个类似物LRRC38、LRRC52、LRRC55、LRTM1和LRTM2。实验旨在确定这些LRRC26类似物对BK通道功能的调节作用，并确定LRR蛋白作为BK通道调节剂的关键结构元件。总的来说，拟议的研究旨在确定新的家族成员，并定义BK通道亚单位的结构和功能特征。本研究结果可能建立广泛的LRR离子通道辅助亚基家族，深入了解LRRC26在BK通道调节中的独特能力，为BK通道相关疾病的治疗和药物开发提供新的蛋白靶点。

DESCRIPTION (provided by applicant): Large conductance, calcium and voltage-activated potassium (BK) channel is a unique member of potassium channel family, which has the largest single channel conductance and is dually activated by voltage and cytosolic free Ca2+ ([Ca2+]i), consisting of the pore-forming, voltage and Ca2+-sensing -subunits (BK) either alone or in association with tissue specific regulatory -subunits (1 - 4). BK channels are generally hard to open, requiring coincident membrane depolarization and [Ca2+]i rise for activation in vivo. However, with proteomic and electrophysiological approaches, we have recently identified a novel BK channel auxiliary subunit, leucine-rich repeat (LRR) containing membrane protein LRRC26 that causes an unprecedented large negative shift (~ -150 mV) in voltage dependence, allowing BK channel activation at even near resting voltages and calcium levels in excitable and non-excitable cells. LRRC26 represents a new family of BK channel auxiliary subunits, which is structurally distinct from the four known -subunits and designated as a -subunit. Like the presence of multiple tissue specific BK channel -subunits with different modulatory functions, we hypothesized that there exist other members of the LRRC26-like -subunits, which differentially modulate BK channels over a wide range of different cell types. The following two specific aims are designed to delineate the family members and to define the structural and functional features of the BK channel -subunits: 1) Identify and characterize new members of BK channel -subunits; 2) identify the structural determinants for modulatory function of the BK channel -subunits. We have identified five LRRC26 paralogs, LRRC38, LRRC52, LRRC55, LRTM1 and LRTM2, from protein database. Experiments are designed to determine the modulatory effects of these LRRC26 paralogs on BK channel function, and to identify key structural elements responsible for a LRR protein to be a BK channel modulator. Overall, the proposed research is designed to identify new family members and to define the structural and functional features of the BK channel -subunits. The findings from the proposed research may establish a broad LRR family of ion channel auxiliary subunits, gain an in-depth understanding of the LRRC26's unique capacity in BK channel modulation, and provide new protein targets for BK channel related disease treatment and drug development. PUBLIC HEALTH RELEVANCE: The findings from the proposed research may establish a broad LRR family of BK channel auxiliary subunits, thus providing new protein targets for BK channel related disease treatment and drug development.