Delineation of a LRR family of BK channel auxiliary subunits

描述（申请人提供）：大电导、钙离子和电压激活钾（BK）通道是钾通道家族中唯一的一个成员，具有最大的单通道电导，由电压和胞浆游离钙（[Ca 2 +]i）双重激活，包括成孔、成膜、成电压和Ca 2+感应亚基（BK）单独或与组织特异性调节亚基联合（1 - 4）。BK通道通常难以打开，需要同时的膜去极化和[Ca 2 +]i升高以在体内激活。然而，通过蛋白质组学和电生理学方法，我们最近发现了一种新的BK通道辅助亚基，富含亮氨酸重复序列（LRR）的膜蛋白LRRC 26，其导致电压依赖性前所未有的大负移（~ -150 mV），允许BK通道在可兴奋和不可兴奋细胞中甚至接近静息电压和钙水平时激活。LRRC 26代表一个新的BK通道辅助亚基家族，它在结构上不同于四个已知的-亚基，并被命名为-亚基。就像存在具有不同调节功能的多个组织特异性BK通道亚基一样，我们假设存在LRRC 26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。设计以下两个具体目标来描述家族成员并定义BK通道亚基的结构和功能特征：1）鉴定和表征BK通道亚基的新成员; 2）鉴定BK通道亚基调节功能的结构决定因素。我们从蛋白质数据库中鉴定了5个LRRC 26的旁系同源物：LRRC 38、LRRC 52、LRRC 55、LRTM 1和LRTM 2。实验的目的是确定这些LRRC 26旁系同源物对BK通道功能的调节作用，并确定负责LRR蛋白是BK通道调节剂的关键结构元件。总体而言，拟议的研究旨在确定新的家族成员，并确定BK通道亚基的结构和功能特征。这项研究的结果可能会建立一个广泛的LRR离子通道辅助亚基家族，深入了解LRRC 26在BK通道调节中的独特能力，并为BK通道相关疾病的治疗和药物开发提供新的蛋白质靶点。 公共卫生相关性：该研究结果可能建立一个广泛的BK通道辅助亚基LRR家族，从而为BK通道相关疾病的治疗和药物开发提供新的蛋白质靶点。

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.