Regulation of the potassium channel IK1 by calcium and histidine phosphorylation

 描述(申请人提供)：IK1，也被称为KCa3.1或SK4，是人类中小电导钾通道家族(SK1-3，IK1)的成员。IK1在T细胞活化中起着至关重要的作用，它通过外流钾来维持负膜电位，从而允许额外的钙内流。IK1是自身免疫性疾病和器官移植排斥反应的潜在治疗靶点。IK1和SK1-3是四聚体，通过与钙调素(CaM)结合来门控/激活，CaM结合到通道细胞质部分的一个区域(CaM结合域，CBD)。IK1激活的一个新特征是需要通过NDPK-B(二磷酸核苷激酶-B)对CBD中特定的组氨酸残基(His358)进行磷酸化。虽然组氨酸磷酸化在原核生物的双组分信号系统中得到了很好的表征，但对真核生物中组氨酸磷酸化的程度和功能的了解才刚刚开始。最近，我们假设IK1的组氨酸磷酸化是解除该通道的金属离子抑制所必需的。在这一应用中，生化、结构和功能研究被用来阐明IK1受钙和组氨酸磷酸化调控的分子机制。

 DESCRIPTION (provided by applicant): IK1, also known as KCa3.1 or SK4, is a member of a family of small- to intermediate-conductance potassium channels in humans (SK1-3, IK1). IK1 plays a crucial role in T-cell activation by effluxing potassium to maintain a negative membrane potential that allows for additional calcium influx. IK1 is a potential therapeutic target (for inhibition) for autoimmune diseases and for organ transplant rejection. IK1 and SK1-3 are tetrameric and are gated/activated through calcium binding to calmodulin (CaM), which binds to a region within the cytoplasmic portion of the channels (CaM binding domain, CBD). A novel feature of IK1 activation is the additional requirement of phosphorylation of a specific histidine residue (His358) within the CBD by NDPK-B (nucleoside diphosphate kinase-B). Although histidine phosphorylation is well characterized in two-component signaling systems in prokaryotes, the extent and function of histidine phosphorylation in eukaryotes are just beginning to be understood. Recently, we hypothesized that histidine phosphorylation of IK1 is necessary to relieve metal- ion inhibition of the channel. In this application, biochemical, structural, and functional studies are proposed to elucidate the molecular mechanisms by which IK1 is regulated by calcium and histidine phosphorylation.