SULFONYLUREA RECEPTORS AND KATP CHANNELS

描述：（申请人摘要） ATP敏感性钾通道（KATP通道）将代谢偶联到膜 电活动。在胰腺β细胞中，KATP通道改变膜 对葡萄糖驱动的ATP/ADP比值变化的反应潜力 新陈代谢.为了了解KATP通道的功能，我们克隆并 重组了它们，表征了两组编码它们的人类基因。 亚基、磺酰脲类受体（SURs）和内向整流子（KIR6.x） 分别，并表明在SUR 1和KIR6.2突变引起隐性 家族性高胰岛素血症。亚基功能紧密结合， 两者都是组装、调节和表面表达所必需的。 异聚体（SUR 1/KIR6.2）4通道;单独表达的亚基保留在 急诊室KIR6.2的C-末端截短去除了ER滞留信号， 对ATP敏感性低的K+通道的表面表达，高度修饰 动力学和没有KATP通道的药理学特性。 与SUR 1的共表达在很大程度上恢复了天然通道特性。 SUR 1与N端截短的KIR6.2的共表达提供了一个通道， 大大延长爆发和降低ATP敏感性。β-细胞（SUR 1）和 心脏（SUR 2A）通道亚型表现出不同的动力学和ATP 灵敏度SUR嵌合体已被用于鉴定两个区域， 动力学和ATP敏感性差异。这些结果开始定义了 一种相互作用的网或网络，将一个未识别的ATP结合位点置于 KIR6.2，SUR的两个细胞内片段，和KIR6.2的N-末端， 靠近海峡口。破坏这一网络 相互作用可以以复杂的方式影响ATP抑制门控。 在这次竞争性更新中，我们建议定义其中的相互作用， 利用肽展示、哺乳动物双杂交和表位标记的网络 技术来鉴定所涉及的肽段。另外还 假设在以下之间存在相互作用：1）跨膜结构域1（TMD 1）， 2）KIR6.2的N-端和一段 SUR的第一组TMD，3）SUR的C-末端和最后36个氨基酸 KIR6.2的最后52个氨基酸，和4）SUR的最后52个氨基酸和C-末端 KIR6.2的胞质结构域。

DESCRIPTION: (Applicant's Abstract) ATP-sensitive potassium channels (KATP channels) couple metabolism to membrane electrical activity. In pancreatic beta-cells KATP channels alter the membrane potential in response to changes in the ATP/ADP ratio driven by glucose metabolism. To understand how KATP channels function, we cloned and reconstituted them, characterized two sets of human genes that encode their subunits, sulfonylurea receptors (SURs) and inward rectifiers (KIR6.x) respectively, and showed that mutations in SUR1 and KIR6.2 cause a recessive form of familial hyperinsulinism. The subunit functions are tightly integrated, both are required for assembly, regulation and surface expression of the heteromeric (SUR1/KIR6.2)4 channel; subunits expressed alone are retained in the ER. C-terminal truncation of KIR6.2 removes an ER retention signal allowing surface expression of a K+ channel with low sensitivity to ATP, highly modified kinetics and none of the pharmacological properties of KATP channels. Co-expression with SUR1 largely restores the native channel properties. Co-expression of SUR1 with N-terminally truncated KIR6.2 gives a channel with greatly prolonged bursts and reduced ATP sensitivity. beta-cell (SUR1) and cardiac (SUR2A) channel isoforms exhibit different kinetics and ATP sensitivity. SUR chimeras have been used to identify two regions that specify the kinetic and ATP sensitivity differences. These results begin to define a web or network of interactions that place an unidentified ATP-binding site on KIR6.2, two intracellular segments of SUR, and the N-terminus of KIR6.2 in close proximity to the mouth of the channel. Disruption of this network of interactions can affect ATP-inhibitory gating in complex ways. In this competitive renewal we propose to define the interactions within this network using peptide display, mammalian two hybrid, and epitope tagging techniques to identify the peptide segments involved. Specifically we hypothesize there are interactions between: 1) Transmembrane domain 1 (TMD1) of KIR6.2 and the TMDs of SUR, 2) the N-terminus of KIR6.2 and a segment within the first set of TMDs of SUR, 3) the C-terminus of SUR and the last 36 amino acids of KIR6.2, and 4) the last 52 amino acids of SUR and the C-terminal cytoplasmic domain of KIR6.2.