Bull Ricardo, Marengo Juan José, Finkelstein José Pablo, Behrens María Isabel, Alvarez Osvaldo
Programa de Fisiología y Biofísica, Facultad de Medicina, Universidad de Chile, Santiago 838-0453, Chile.
Am J Physiol Cell Physiol. 2003 Jul;285(1):C119-28. doi: 10.1152/ajpcell.00296.2002. Epub 2003 Mar 12.
We have reported that ryanodine receptor (RyR) channels display three different responses to cytoplasmic free Ca2+ concentration ([Ca2+]) depending on their redox state (Marengo JJ, Hidalgo C, and Bull R. Biophys J 74: 1263-1277, 1998), with low, moderate, and high maximal fractional open times (Po). Activation by ATP of single RyR channels from rat brain cortex was tested in planar lipid bilayers with 10 or 0.1 microM cytoplasmic [Ca2+]. At 10 microM [Ca2+], low-Po channels presented lower apparent affinity to activation by ATP [[ATP] for half-maximal activation (KaATP) = 422 microM] than moderate-Po channels (KaATP = 82 microM). Oxidation of low-Po channels with thimerosal or 2,2'-dithiodipyridine (DTDP) gave rise to moderate-Po channels and decreased KaATP from 422 to 82 microM. At 0.1 microM cytoplasmic [Ca2+], ATP induced an almost negligible activation of low-Po channels. After oxidation to high-Po behavior, activation by ATP was markedly increased. Noise analysis of single-channel fluctuations of low-Po channels at 10 microM [Ca2+] plus ATP revealed the presence of subconductance states, suggesting a conduction mechanism that involves four independent subchannels. On oxidation the subchannels opened and closed in a concerted mode.
我们已经报道过，雷诺丁受体（RyR）通道根据其氧化还原状态对细胞质游离钙离子浓度（[Ca2+]）呈现出三种不同的反应（马伦戈JJ、伊达尔戈C和布尔R。《生物物理杂志》74: 1263 - 1277，1998），其最大开放时间分数（Po）分别为低、中、高。在具有10或0.1微摩尔细胞质[Ca2+]的平面脂质双分子层中测试了大鼠脑皮质单个RyR通道被ATP激活的情况。在10微摩尔[Ca2+]时，低Po通道对ATP激活的表观亲和力低于中Po通道[[ATP]为半最大激活时的值（KaATP） = 422微摩尔]（KaATP = 82微摩尔）。用硫柳汞或2,2'-二硫代二吡啶（DTDP）氧化低Po通道会产生中Po通道，并使KaATP从422微摩尔降至82微摩尔。在0.1微摩尔细胞质[Ca2+]时，ATP对低Po通道的激活几乎可以忽略不计。氧化至高Po状态后，ATP激活明显增加。在10微摩尔[Ca2+]加ATP条件下对低Po通道单通道波动的噪声分析揭示了亚电导状态的存在，这表明传导机制涉及四个独立的亚通道。氧化后，亚通道以协同模式打开和关闭。
