SH oxidation coordinates subunits of rat brain ryanodine receptor channels activated by calcium and ATP.
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.
Bull
Ricardo
R
Programa de Fisiología y Biofísica, Facultad de Medicina, Universidad de Chile, Santiago 838-0453, Chile.
Marengo
Juan José
JJ
Finkelstein
José Pablo
JP
Behrens
María Isabel
MI
Alvarez
Osvaldo
O
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D016477:Artifacts; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004220:Disulfides / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013849:Thimerosal / Q000494:pharmacology
D004220:Disulfides; D019837:Ryanodine Receptor Calcium Release Channel; D013438:Sulfhydryl Compounds; C001105:2,2'-dipyridyl disulfide; D013849:Thimerosal; D015082:2,2'-Dipyridyl; D000255:Adenosine Triphosphate; D002118:Calcium