SH oxidation coordinates subunits of rat brain ryanodine receptor channels activated by calcium and ATP

Abstract

Bull, Ricardo, Juan Jose´ Marengo, Jose´ Pablo Finkelstein, Marı´a Isabel Behrens, and Osvaldo Alvarez. SH oxidation coordinates subunits of rat brain ryanodine receptor channels activated by calcium and ATP. Am J Physiol Cell Physiol 285: C119–C128, 2003. First published March 12, 2003; 10.1152/ajpcell.00296.2002.—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 M cytoplasmic [Ca2 ]. At 10 M [Ca2 ], low-Po channels presented lower apparent affinity to activation by ATP [[ATP] for half-maximal activation (KaATP) 422 M] than moderate-Po channels (KaATP 82 M). 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 M. At 0.1 M 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 M [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.