Regulation of Vascular BK Channels in Diabetes

大电导钙激活钾（BK）通道是细胞内主要的离子决定因子， 介导血管舒张，是内皮源性超极化因子（EDHF）的靶点。我们 发现EDHF对BK通道的调节在糖尿病动物中是异常的， BK通道的性质在糖尿病冠状动脉中改变。冠状动脉BK通道 来自糖尿病动物的平滑肌细胞对钙和电压依赖性 activation.我们已经证明，血管BK通道调节的机制是 在1型和II型糖尿病中改变涉及高血糖诱导的氧化应激， BK通道中的半胱氨酸残基是氧化还原调节的目标。BK通道的C911残基 孔亚单位对高血糖和过氧化氢的调节特别敏感，因为 C911A突变对过氧化氢和高糖的作用不敏感。这个目标 该项目旨在进一步阐明活性氧（ROS） 调节糖尿病中的BK通道。待检验的假设为：1）血管BK通道异常 在糖尿病中的功能是由于ROS对特定半胱氨酸残基的氧化还原调节。2)BK通道 被ROS修饰的蛋白质是泛素化和蛋白酶体降解的底物。三个具体目标是 提出了目的1研究糖尿病诱导的氧化应激对BK通道的调节机制， 应力目的2将研究是否预防特定半胱氨酸残基的氧化调节， 维持糖尿病中BK通道功能的完整性。目标3将确定是否氧化还原调节 BK通道是泛素化和蛋白酶体降解的靶点。这些研究将在 使用体外和体内糖尿病模型。全细胞和单通道膜片钳技术， 抗氧化酶体外基因转移，并将采用特定的转基因小鼠来确定 糖尿病诱导的ROS产生对BK通道功能和降解的影响。的结果 该项目可能提供重要的电生理和分子机制的新见解， BK通道功能改变，可能有助于内皮依赖性和非依赖性 糖尿病的血管功能障碍

The large conductance calcium-activated potassium (BK) channels are major ionic determinants in mediating vasorelaxation and are the target of endothelium-derived hyperpolarizing factors (EDHFs). We found that regulation of BK channels by EDHFs is abnormal in diabetic animals and the intrinsic properties of BK channels are altered in diabetic coronary arteries. The BK channels in coronary arterial smooth muscle cells from diabetic animals have reduced sensitivity to calcium- and voltage-dependent activation. We have demonstrated that the mechanism whereby vascular BK channel regulation is altered in Type 1 and Type II diabetes involves hyperglycemia-induced oxidative stress, where the cysteine residues in BK channels are targets of redox modulation. The C911 residue of the BK channel pore subunit is particularly sensitive to modulation by hyperglycemia and by hydrogen peroxide, as the C911A mutation is insensitive to the effects of hydrogen peroxide and to high glucose. The goal of this project is to further delineate the molecular mechanisms through which reactive oxygen species (ROS) modulate BK channels in diabetes. The hypotheses to be tested are: 1) Abnormal vascular BK channel function in diabetes is due to redox modulation of specific cysteine residues by ROS. 2) BK channel modified by ROS is a substrate for ubiquitination and proteasomal degradation. Three specific aims are proposed. Aim 1 will examine the mechanism of BK channel modulation by diabetes-induced oxidative stress. Aim 2 will examine whether prevention of oxidative modulation of specific cysteine residues would maintain the integrity of BK channel function in diabetes. Aim 3 will determine whether redox-modulated BK channels are targets for ubiquitination and proteasomal degradation. These studies will be performed using in vitro and in vivo models of diabetes. Whole-cell and single channel patch clamp techniques, antioxidant enzyme in vitro gene transfer, and specific transgenic mice will be employed to determine the effects of diabetes-induced ROS production on BK channel function and degradation. The results of this project may provide important novel insight into the electrophysiological and molecular mechanisms of altered BK channel function that may contribute to both endothelium-dependent and -independent vascular dysfunction in diabetes.