MOLECULAR MECHANISMS OF GATING IN IONIC CHANNELS

离子通道门控的分子机制

• 批准号: 2175797
• 负责人: WOLFGANG F NONNER
• 金额: $ 14.78万
• 依托单位: UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 1981
• 资助国家: 美国
• 起止时间: 1981-08-01 至 1998-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2175797
• 关键词: GABA receptor; acidity /alkalinity; anions; carboxylate; chemical kinetics; cholinergic receptors; cold temperature; computer simulation; divalent cations; electrical conductance; embryo /fetus tissue /cell culture; glycine receptors; ionic bond; ionic strengths; laboratory rat; membrane potentials; myotubes; neurons; neuropharmacology; potassium channel; protein structure function; voltage /patch clamp

Biophysical studies are proposed concerning (l) the mechanisms by which excitatory and inhibitory ligand-gated ion channels select between cations and anions, (2) the gate mechanism of a large-conductance K channel at subzero temperatures. The experiments use embryonic rat central neurons (hippocampus, spinal cord) and myotubes maintained in primary tissue culture. The patch clamp technique will be used to study currents from individual channels in excised membrane patches. The excitatory or inhibitory effects of the structurally homologous ion channels operated by the neurotransmitters ACh, GABA, or glycine are determined by the channels' ability to select permeant ions by charge polarity. In the AChR channel, several treatments (high ionic strength, pH, and a carboxyl reagent) will be used to neutralize groups with negative net charges, to assess their importance in the cation/anion selection. In GABA-R and Gly-R channels, the roles of intracellular and extracellular divalent cations in establishing a high selectivity for anions will be studied (a substantial cation leakage through channels exposed to divalent-free salines and partial restoration of anion selectivity by external Ca have observed). The divalent in requirements will be determined and tests will be applied to distinguish between structural and direct electrostatic effects of divalent cations. A new level of kinetic phenomena underlying the gating of large- conductance Ca-activated K channels will be studied at temperatures down to -30 degrees C using techniques developed in our laboratory. These experiments will investigate the operation of the molecular gate by which the ionic current of the channel pore is controlled. At room temperature this gate acts like an instant switch, but at very low temperature channel transitions are slowed to an extent that a cadence of ion current changes can be measured from which the behavior of the actual gate can be inferred. These studies address fundamental questions concerning ionic channels of neurons and muscle, and thus should provide basic information important for understanding normal and impaired function in these tissues.

提出了有关（l）的生物物理研究 在阳离子之间选择兴奋性和抑制配体门控离子通道 和阴离子，（2）大传导k通道的栅极机理 亚零温度。实验使用胚胎大鼠中央神经元 （海马，脊髓）和肌管保持在原代组织中 文化。贴片夹技术将用于研究 切除的膜斑块中的单个通道。 结构同源离子的兴奋性或抑制作用 神经递质ACH，GABA或甘氨酸操作的通道是 取决于通道通过电荷选择渗透离子的能力 极性。 在ACHR通道中，几种治疗方法（高离子强度， pH和羧基试剂）将用于中和 负净收费，以评估其在阳离子/阴离子中的重要性 选择。在GABA-R和GLY-R通道中，细胞内和 细胞外二价阳离子在建立高选择性方面 将研究阴离子（通过通道大量阳离子泄漏 暴露于无二价盐水和阴离子的部分恢复 外部CA的选择性已经观察到）。要求的二价 将确定并应用测试以区分 二价阳离子的结构和直接静电效应。 大型基础的新水平的动力学现象 电导CA激活的K通道将在降低温度下进行研究 使用实验室中开发的技术至-30度。这些 实验将研究分子门的运行 控制通道孔的离子电流。 在室温下 该门像即时开关一样，但在非常低的温度通道下 过渡速度放缓，以至于离子电流的节奏变化 可以测量实际门的行为可以 推断。 这些研究涉及有关离子渠道的基本问题 神经元和肌肉，因此应提供重要的基本信息 了解这些组织中的正常和受损功能。