TRAFFICKING SIGNALS ON KATP CHANNELS SUBUNITS

KATP通道的胰岛β细胞亚型，包括 Suri和KIR6.2亚基在糖代谢偶联到 膜的电活动。任何一个亚基的突变都会导致隐性遗传 新生儿低血糖的形式称为持续性高胰岛素低血糖 婴儿期，或PHHI。最近的研究表明，这两个亚基都有人口贩运 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末端有一个额外的信号， 即使在没有内质网的情况下，表面表达也需要这一点 保留信号。ER保持信号在信道期间被“屏蔽” 组装，这两组信号一起充当质量控制 确保只有完全组装的通道，(SUR1/KIR6.2)4， 两个核苷酸结合折叠完好无损地到达细胞表面。一批 PHHI突变截断SurI；有人建议这些缺失移除 C端信号，然后SURIAC通道不能到达该单元 表面，这解释了观察到的通道活动的损失。大自然 这些最近发现的贩运信号，它们是如何发挥作用的，以及它们是什么 它们与之相互作用的蛋白质尚不清楚。这样做的目的是 应用的是研究膜在正确表面运输中的作用 通过确定SurI C-末端如何表达KATP通道 “顺势”信号起作用，特别是调查人员建议： 1.确定移除Suri C-末端信号是否会导致 降解速度或针对不同的降解途径。 2.鉴定可能介导苏里羧基活性的“受体(S)” 终点站。 3.检查我们所展示的Suri错义突变的行为 贩卖缺陷。 4.表征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.