TRAFFICKING SIGNALS ON KATP CHANNELS SUBUNITS

KATP通道的胰腺β细胞亚型，包括 SURI和KIR6.2亚基，在葡萄糖代谢偶联至 膜电活动任何一个亚基的突变都可能导致隐性遗传， 一种新生儿低血糖，称为持续性高胰岛素血症性低血糖 或PHHI。最近的工作表明，这两个小组都有贩运人口的活动， 信号. SURI和KIR6.2具有内质网（ER）滞留信号， 虽然我们已经确定SURI的C末端具有额外的信号， 即使在没有ER的情况下， 保留信号。ER保留信号在通道期间被“掩蔽”。 组装，这两组信号一起作为质量控制 机制，以确保只有完全组装的通道，（SUR 1/KIR6.2）4， 其中两个核苷酸结合折叠完整地到达细胞表面。一些 PHHI突变截短SURI;有人提出，这些缺失去除了 C-末端信号，SURIAC通道随后无法到达细胞 表面，这解释了所观察到的通道活动的损失。性质 这些最近发现的贩运信号，它们是如何运作的， 与它们相互作用的蛋白质还不清楚。的目的 应用是研究在正确的表面膜运输的作用 KATP通道的表达，通过确定SURI C-末端 “顺行”信号工作，特别是研究人员建议： 1.确定SURI C-末端信号的去除是否会导致 降解速率或针对不同的降解途径。 2.鉴定可能介导SURI羧基活性的“受体” 终点站 3.检查我们已经展示的SURI错义突变的行为， 贩运缺陷。 4.描述KATP通道亚单位的组装顺序。

The pancreatic beta-cell isoform of KATP channels, consisting of SURI and KIR6.2 subunits, plays a key role in coupling glucose metabolism to membrane electrical activity. Mutations in either subunit can cause a recessive form of neonatal hypoglycemia termed persistent hyperinsulinemic hypoglycemia of infancy, or PHHI. Recent work has shown that both subunits have trafficking signals. SURI and KIR6.2 have endoplasmic reticulum (ER) retention signals, while we have established that the C-terminus of SURI has an additional signal, which is required for surface expression even in the absence of the ER retention signals. The ER retention signals are 'masked' during channel assembly, and together these two sets of signals act as a quality control mechanism to insure that only completely assembled channels, (SUR1/KIR6.2)4, with both nucleotide-binding folds intact reach the cell surface. A number of PHHI mutations truncate SURI; it is proposed that these deletions remove the C-terminal signal and that the SURIAC channels then fail to reach the cell surface, which accounts for the observed loss of channel activity. The nature of these recently discovered trafficking signals, how they function, and what proteins they interact with is not understood. The objective of this application is to study the role of membrane trafficking in the correct surface expression of KATP channels by determining how the SURI C-terminal 'anterograde' signal works, specifically the investigators propose to: 1. Determine if removal of the SURI C-terminal signal results in increased rates of degradation or targeting to different degradation pathways. 2. Identify "receptor(s)" that may mediate the activity of the SURI carboxyl terminus. 3. Examine the behavior of SURI missense mutations that we have shown exhibit trafficking defects. 4. Characterize the order of assembly of KATP channel sub-units.