MECHANISMS OF IONIC CHANNEL ACTIVITY

离子通道活性机制

• 批准号: 2078875
• 负责人: KARL L MAGLEBY
• 金额: $ 19.79万
• 依托单位: UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 1983
• 资助国家: 美国
• 起止时间: 1983-09-01 至 1998-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2078875
• 关键词: bioenergetics; biological transport; calcium metabolism; cell membrane; chloride channels; computer data analysis; computer simulation; hormone regulation /control mechanism; ion transport; laboratory rat; mathematical model; membrane channels; membrane permeability; membrane potentials; muscle cells; potassium channel; sarcolemma; striated muscles; tissue /cell culture; voltage /patch clamp; voltage gated channel

Ion channels are large protein macromolecules which span cell membranes. They open and close, or gate their pores, controlling the flux of ions across the membrane, and consequently, membrane potential. The long term objectives of the proposed research are to determine the gating mechanisms of ion channels. To work towards this goal, currents will be recorded from single ion channels with the patch clamp technique and analyzed by computer. The channels to be studied are the large conductance calcium-activated potassium channel (BK channel) and the fast Cl channel, obtained from the membrane of mammalian skeletal muscle cells grown in tissue culture. Seven specific projects will be carried out: (1) to determine whether the gating kinetics of ion channels are best described by models with discrete states and constant transition rates between the states (Markovian models) or by models with a continuum of states and fractal scaling (fractal models); (2) to determine whether the brief interruptions (flickers) commonly observed in currents flowing through single channels arise from complete or partial channel closures; (3) to implement an advanced method for determining kinetic gating mechanisms, which uses all of the non-redundant kinetic information in the single channel current record and which takes into account both limited time resolution and the noise in the current record. This method uses computer simulation to calculate, for a given gating mechanisms, the two-dimensional distributions of adjacent open and shut interval durations, which are then compared to the experimental distributions. This advanded method will be used to determine: (4) the steady-state gating mechanism of the fast Cl channel; (5) mechanism by which voltage modulates the activity of the fast Cl channel; (6) the Ca-activated gating mechanism for the normal mode of the BK channel; and (7) the altered gating mechanisms for the other modes of the BK channel. In each case, the most likely gating mechanisms will be defined in terms of kinetic schemes which indicate: the numbers of open and shut states, the transition pathways between the states, the energy barriers for the transitions, and how channel activity is modulated through voltage or calcium induced changes in energy barrier heights. Characterizing ion channels is an important step towards understanding the molecular basis of both normal muscle function and those muscle diseases where defects in the numbers and/or functions of ion channels are implicated. Once the normal channels are characterized, it will be possible to determine if their numbers and/or functions are altered in the disease states.

离子通道是跨越细胞膜的大蛋白质大分子。 它们打开和关闭，或者控制它们的孔，控制离子的通量 穿过膜，从而产生膜电位。 长期来看 拟议研究的目标是确定门控机制 离子通道。 为了实现这一目标，电流将被记录 采用膜片钳技术的单离子通道并通过以下方法进行分析 电脑。 要研究的通道是大电导通道 钙激活钾通道（BK 通道）和快速 Cl 通道， 从生长在哺乳动物骨骼肌细胞的膜中获得 组织培养。 实施七个具体项目：（一） 确定离子通道的门控动力学是否最好地描述为 具有离散状态和恒定转换率的模型 状态（马尔可夫模型）或具有连续状态的模型和 分形缩放（分形模型）； (2)判断是否简述 电流流过时常见的中断（闪烁） 单一通道是由完全或部分通道关闭引起的； (3) 至 实施一种确定动力学门控机制的先进方法， 它使用单个中的所有非冗余动力学信息 通道当前记录并考虑了有限时间 分辨率和当前记录中的噪声。 此方法使用电脑 对于给定的门控机制，模拟计算二维 相邻打开和关闭间隔持续时间的分布，然后是 与实验分布相比。 这种先进的方法将 用于确定： (4) 快速 Cl 的稳态门控机制 渠道; (5) 电压调节快速细胞活性的机制 氯离子通道； (6)正常模式的Ca激活门控机制 BK频道； (7) 其他模式的门控机制的改变 BK 频道。 在每种情况下，最可能的门控机制是 根据动力学方案定义，表明：开放的数量 和关闭状态、状态之间的过渡路径、能量 转型的障碍，以及如何通过以下方式调节渠道活动 电压或钙引起的能垒高度的变化。 表征离子通道是理解离子通道的重要一步 正常肌肉功能和肌肉疾病的分子基础 其中离子通道的数量和/或功能的缺陷是 受牵连。 一旦正常渠道被表征，它将被 可以确定它们的数量和/或功能是否在 疾病状态。