%0 Journal Article %1 Xu_1998_2302 %A Xu, L. %A Meissner, G. %D 1998 %J Biophys. J. %K 9788925 Acid, Adenosine Animals, Binding Blockers, Caffeine, Calcium Calcium, Calcium-Binding Cells, Channel Channel, Channels, Chimeric Cultured, Dogs, Egtazic Electrophysiology, Gov't, Heart, Humans, Immunophilins, Isoforms, Liposomes, Magnesium, Mammals, Muscle, Myocardium, Non-U.S. P.H.S., Protein Proteins, Receptor Release Research Reticulum, Ryanodine Ryanodine, Sarcoplasmic Skeletal, Support, Tacrolimus Tacrolimus, Triphosphate, Tritium, U.S. %N 5 %P 2302--2312 %T Regulation of cardiac muscle Ca$^2+$ release channel by sarcoplasmic reticulum lumenal Ca$^2+$. %U http://www.biophysj.org/cgi/content/full/75/5/2302 %V 75 %X The cardiac muscle sarcoplasmic reticulum Ca$^2+$ release channel (ryanodine receptor) is a ligand-gated channel that is activated by micromolar cytoplasmic Ca$^2+$ concentrations and inactivated by millimolar cytoplasmic Ca$^2+$ concentrations. The effects of sarcoplasmic reticulum lumenal Ca$^2+$ on the purified release channel were examined in single channel measurements using the planar lipid bilayer method. In the presence of caffeine and nanomolar cytosolic Ca$^2+$ concentrations, lumenal-to-cytosolic Ca$^2+$ fluxes >/=0.25 pA activated the channel. At the maximally activating cytosolic Ca$^2+$ concentration of 4 microM, lumenal Ca$^2+$ fluxes of 8 pA and greater caused a decline in channel activity. Lumenal Ca$^2+$ fluxes primarily increased channel activity by increasing the duration of mean open times. Addition of the fast Ca$^2+$-complexing buffer 1,2-bis(2-aminophenoxy)ethanetetraacetic acid (BAPTA) to the cytosolic side of the bilayer increased lumenal Ca$^2+$-activated channel activities, suggesting that it lowered Ca$^2+$ concentrations at cytosolic Ca$^2+$-inactivating sites. Regulation of channel activities by lumenal Ca$^2+$ could be also observed in the absence of caffeine and in the presence of 5 mM MgATP. These results suggest that lumenal Ca$^2+$ can regulate cardiac Ca$^2+$ release channel activity by passing through the open channel and binding to the channel's cytosolic Ca$^2+$ activation and inactivation sites.

@article{Xu_1998_2302, abstract = {The cardiac muscle sarcoplasmic reticulum {C}a$^{2+}$ release channel (ryanodine receptor) is a ligand-gated channel that is activated by micromolar cytoplasmic {C}a$^{2+}$ concentrations and inactivated by millimolar cytoplasmic {C}a$^{2+}$ concentrations. The effects of sarcoplasmic reticulum lumenal {C}a$^{2+}$ on the purified release channel were examined in single channel measurements using the planar lipid bilayer method. In the presence of caffeine and nanomolar cytosolic {C}a$^{2+}$ concentrations, lumenal-to-cytosolic {C}a$^{2+}$ fluxes >/=0.25 pA activated the channel. At the maximally activating cytosolic {C}a$^{2+}$ concentration of 4 microM, lumenal {C}a$^{2+}$ fluxes of 8 pA and greater caused a decline in channel activity. Lumenal {C}a$^{2+}$ fluxes primarily increased channel activity by increasing the duration of mean open times. Addition of the fast {C}a$^{2+}$-complexing buffer 1,2-bis(2-aminophenoxy)ethanetetraacetic acid (BAPTA) to the cytosolic side of the bilayer increased lumenal {C}a$^{2+}$-activated channel activities, suggesting that it lowered {C}a$^{2+}$ concentrations at cytosolic {C}a$^{2+}$-inactivating sites. Regulation of channel activities by lumenal {C}a$^{2+}$ could be also observed in the absence of caffeine and in the presence of 5 mM MgATP. These results suggest that lumenal {C}a$^{2+}$ can regulate cardiac {C}a$^{2+}$ release channel activity by passing through the open channel and binding to the channel's cytosolic {C}a$^{2+}$ activation and inactivation sites.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Xu, L. and Meissner, G.}, biburl = {https://www.bibsonomy.org/bibtex/20deae75665c24182a291d00c7550885e/hake}, description = {The whole bibliography file I use.}, file = {Xu_1998_2302.pdf:Xu_1998_2302.pdf:PDF}, interhash = {26270067ef72bc63d731b623147fecc5}, intrahash = {0deae75665c24182a291d00c7550885e}, journal = {Biophys. J.}, key = 215, keywords = {9788925 Acid, Adenosine Animals, Binding Blockers, Caffeine, Calcium Calcium, Calcium-Binding Cells, Channel Channel, Channels, Chimeric Cultured, Dogs, Egtazic Electrophysiology, Gov't, Heart, Humans, Immunophilins, Isoforms, Liposomes, Magnesium, Mammals, Muscle, Myocardium, Non-U.S. P.H.S., Protein Proteins, Receptor Release Research Reticulum, Ryanodine Ryanodine, Sarcoplasmic Skeletal, Support, Tacrolimus Tacrolimus, Triphosphate, Tritium, U.S.}, month = Nov, number = 5, pages = {2302--2312}, pmid = {9788925}, timestamp = {2009-06-03T11:21:38.000+0200}, title = {Regulation of cardiac muscle {C}a$^{2+}$ release channel by sarcoplasmic reticulum lumenal {C}a$^{2+}$.}, url = {http://www.biophysj.org/cgi/content/full/75/5/2302}, volume = 75, year = 1998 }