Methanethiosulfonate derivatives inhibit current through the ryanodine receptor/channel.
To identify regions of the ryanodine receptor (RyR) important for ion conduction we modified the channel with sulfhydryl-reacting compounds. After addition of methanethiosulfonate (MTS) compounds channel conductance was decreased while other channel properties, including channel regulation by ATP, caffeine, or Ca, were unaffected. The site of action was accessible to the MTS compounds from the cytoplasmic, but not the luminal, side of the channel. In addition, the hydrophilic MTS compounds were only effective when the channel was open, suggesting that the compounds covalently modify the channel from within the water-filled ion conducting pathway. The decrease in channel current amplitude occurred in a step-wise fashion and was irreversible and cumulative over time, eventually leading to the complete block of channel current. However, the time required for each consecutive modification during continuous exposure to the MTS compounds increased, suggesting that successive modification by the MTS compounds is not independent. These results are consistent with the hypothesis that the channel forms a wide vestibule on the cytoplasmic side and contains a much smaller opening on the luminal side. Furthermore, our results indicate that the MTS compounds can serve as functional markers for specific residues of the RyR to be identified in molecular studies.
Quinn
K E
KE
Department of Physiology, University of Connecticut Health Center, Farmington 06030, USA. kquinn@neuron.uchc.edu
Ehrlich
B E
BE
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005020:Ethyl Methanesulfonate / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008051:Lipid Bilayers; D008741:Methyl Methanesulfonate / Q000031:analogs & derivatives* / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013885:Thiosulfates / Q000494:pharmacology*
D015220:Calcium Channels; D007473:Ion Channels; D008051:Lipid Bilayers; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D013438:Sulfhydryl Compounds; D013885:Thiosulfates; C093171:methanethiosulfonate ethylammonium; D012433:Ryanodine; C014674:methyl methanethiosulfonate; D005020:Ethyl Methanesulfonate; D008741:Methyl Methanesulfonate