Role of Herg-like K+ Channels in G.I. Smooth Muscle

Herg 样 K 通道在 G.I. 中的作用

• 批准号: 6382024
• 负责人: HAMID I AKBARALI
• 金额: $ 21.9万
• 依托单位: UNIVERSITY OF OKLAHOMA HLTH SCIENCES CTR
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-15 至 2004-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6382024
• 关键词: acetylcholine; cisapride; gastrointestinal motility /pressure; gastrointestinal pharmacology; immunofluorescence technique; laboratory rabbit; membrane potentials; muscle function; neuromuscular transmission; opossums; potassium channel; smooth muscle; western blottings

The objective of this proposal is to pursue studies on the genesis of the resting membrane potential in visceral smooth muscle. The resting potential is one of the major determinants of smooth muscle excitability and is largely governed by the permeability to K+ ions. Preliminary studies demonstrate that the resting potential of several gastrointestinal smooth muscle is, in part, controlled by a unique human ether-a-go-go (HERG)-like K+ channel. This K+ current demonstrates inward rectification and appears to be a potential target of the commonly used prokinetic agent, cisapride. The first specific aim is to characterize the detailed biophysical properties of the HERG-like K+ current in gastrointestinal smooth muscle cells. The voltage- dependent kinetics of this current in single cells will be determined using the patch clamp technique and its physiological role in resting potential and repolarization of the action potential will be characterized. The second specific aim is to identify the pharmacological regulation of the smooth muscle HERG-like K+ currents. in these studies, the effects of class III antiarrhythmic compounds which are known HERG channel blockers will be determined, and the mechanism of action of the prokinetic agent, cisapride on the HERG currents will be investigated. Preliminary data show that cisapride attenuates the HERG currents in single gastrointestinal smooth muscle cells and depolarizes muscle strips. The effects of the excitatory neurotransmitter, acetylcholine on these K currents will be determined and the involvement of the second messenger regulation by protein kinase C will be evaluated. In the third specific aim, the protein expression of HERG-like channels will be localized by immunofluorescence techniques and by Western blotting. The fourth specific aim is to define the relationship of the HERG-like conductance with those of the other inwardly rectifying currents in smooth muscle. In these studies the role of IKi, ATP- sensitive K+ channel and the hyperpolarization-activated cation currents will be examined. Inhibitory modulators of the HERG-ike K+ channels in smooth muscle may provide new approaches to treatment of disorders that involve smooth muscle hyperexcitability.

该提案的目的是研究内脏平滑肌静息膜电位的起源。静息电位是平滑肌兴奋性的主要决定因素之一，很大程度上取决于 K+ 离子的渗透性。初步研究表明，一些胃肠道平滑肌的静息电位部分是由独特的类似人乙醚 (HERG) 的 K+ 通道控制的。该 K+ 电流表现出内向整流作用，似乎是常用促动力剂西沙必利的潜在目标。第一个具体目标是表征胃肠平滑肌细胞中 HERG 样 K+ 电流的详细生物物理特性。将使用膜片钳技术确定单细胞中该电流的电压依赖性动力学，并且将表征其在静息电位和动作电位复极化中的生理作用。第二个具体目标是确定平滑肌 HERG 样 K+ 电流的药理学调节。在这些研究中，将确定已知的 HERG 通道阻滞剂的 III 类抗心律失常化合物的作用，并研究促运动剂西沙必利对 HERG 电流的作用机制。初步数据显示，西沙必利可减弱单个胃肠道平滑肌细胞的 HERG 电流并使肌条去极化。将确定兴奋性神经递质乙酰胆碱对这些 K 电流的影响，并评估蛋白激酶 C 对第二信使调节的参与。第三个具体目标是通过免疫荧光技术和蛋白质印迹法定位 HERG 样通道的蛋白表达。第四个具体目标是定义类 HERG 电导与平滑肌中其他内向整流电流的关系。在这些研究中，将检查 IKi、ATP 敏感 K+ 通道和超极化激活的阳离子电流的作用。平滑肌中 HERG 样 K+ 通道的抑制性调节剂可能为治疗涉及平滑肌过度兴奋性的疾病提供新方法。