%0 Journal Article %1 Gyoer_1998_2801 %A Gy�rke, I. %A Gy�rke, S. %D 1998 %J Biophys. J. %K 9826602 Allosteric Animals, Bilayers, Binding Biophysics, Calcium Calcium, Channel Channel, Cytosol, Dogs, Gating, Gov't, In Ion Lipid Membrane Microsomes, Myocardium, Non-U.S. P.H.S., Potentials, Receptor Regulation, Release Research Reticulum, Ryanodine Sarcoplasmic Sites, Support, U.S. Vitro, %N 6 %P 2801--2810 %T Regulation of the cardiac ryanodine receptor channel by luminal Ca$^2+$ involves luminal Ca$^2+$ sensing sites. %U http://www.biophysj.org/cgi/content/full/75/6/2801 %V 75 %X The mechanism of activation of the cardiac calcium release channel/ryanodine receptor (RyR) by luminal Ca$^2+$ was investigated in native canine cardiac RyRs incorporated into lipid bilayers in the presence of 0.01 microM to 2 mM Ca$^2+$ (free) and 3 mM ATP (total) on the cytosolic (cis) side and 20 microM to 20 mM Ca$^2+$ on the luminal (trans) side of the channel and with Cs+ as the charge carrier. Under conditions of low trans Ca$^2+$ (20 microM), increasing cis Ca$^2+$ from 0.1 to 10 microM caused a gradual increase in channel open probability (Po). Elevating cis Ca$^2+$ above 100 microM resulted in a gradual decrease in Po. Elevating trans Ca$^2+$ enhanced channel activity (EC50 approximately 2.5 mM at 1 microM cis Ca$^2+$) primarily by increasing the frequency of channel openings. The dependency of Po on trans Ca$^2+$ was similar at negative and positive holding potentials and was not influenced by high cytosolic concentrations of the fast Ca$^2+$ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N, N-tetraacetic acid. Elevated luminal Ca$^2+$ enhanced the sensitivity of the channel to activating cytosolic Ca$^2+$, and it essentially reversed the inhibition of the channel by high cytosolic Ca$^2+$. Potentiation of Po by increased luminal Ca$^2+$ occurred irrespective of whether the electrochemical gradient for Ca$^2+$ supported a cytosolic-to-luminal or a luminal-to-cytosolic flow of Ca$^2+$ through the channel. These results rule out the possibility that under our experimental conditions, luminal Ca$^2+$ acts by interacting with the cytosolic activation site of the channel and suggest that the effects of luminal Ca$^2+$ are mediated by distinct Ca$^2+$-sensitive site(s) at the luminal face of the channel or associated protein.

@article{Gyoer_1998_2801, abstract = {The mechanism of activation of the cardiac calcium release channel/ryanodine receptor (RyR) by luminal {C}a$^{2+}$ was investigated in native canine cardiac RyRs incorporated into lipid bilayers in the presence of 0.01 microM to 2 mM {C}a$^{2+}$ (free) and 3 mM ATP (total) on the cytosolic (cis) side and 20 microM to 20 mM {C}a$^{2+}$ on the luminal (trans) side of the channel and with Cs+ as the charge carrier. Under conditions of low trans {C}a$^{2+}$ (20 microM), increasing cis {C}a$^{2+}$ from 0.1 to 10 microM caused a gradual increase in channel open probability (Po). Elevating cis {C}a$^{2+}$ above 100 microM resulted in a gradual decrease in Po. Elevating trans [{C}a$^{2+}$] enhanced channel activity (EC50 approximately 2.5 mM at 1 microM cis {C}a$^{2+}$) primarily by increasing the frequency of channel openings. The dependency of Po on trans [{C}a$^{2+}$] was similar at negative and positive holding potentials and was not influenced by high cytosolic concentrations of the fast {C}a$^{2+}$ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N, N-tetraacetic acid. Elevated luminal {C}a$^{2+}$ enhanced the sensitivity of the channel to activating cytosolic {C}a$^{2+}$, and it essentially reversed the inhibition of the channel by high cytosolic {C}a$^{2+}$. Potentiation of Po by increased luminal {C}a$^{2+}$ occurred irrespective of whether the electrochemical gradient for {C}a$^{2+}$ supported a cytosolic-to-luminal or a luminal-to-cytosolic flow of {C}a$^{2+}$ through the channel. These results rule out the possibility that under our experimental conditions, luminal {C}a$^{2+}$ acts by interacting with the cytosolic activation site of the channel and suggest that the effects of luminal {C}a$^{2+}$ are mediated by distinct {C}a$^{2+}$-sensitive site(s) at the luminal face of the channel or associated protein.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Gy�rke, I. and Gy�rke, S.}, biburl = {https://www.bibsonomy.org/bibtex/21c858bf6d363fc9bb7591afc4e19c6f0/hake}, description = {The whole bibliography file I use.}, file = {Gyoer_1998_2801.pdf:Gyoer_1998_2801.pdf:PDF}, interhash = {f4ea2bdcfd8d8c6447f590f8da39c3cb}, intrahash = {1c858bf6d363fc9bb7591afc4e19c6f0}, journal = {Biophys. J.}, key = 195, keywords = {9826602 Allosteric Animals, Bilayers, Binding Biophysics, Calcium Calcium, Channel Channel, Cytosol, Dogs, Gating, Gov't, In Ion Lipid Membrane Microsomes, Myocardium, Non-U.S. P.H.S., Potentials, Receptor Regulation, Release Research Reticulum, Ryanodine Sarcoplasmic Sites, Support, U.S. Vitro,}, month = Dec, number = 6, pages = {2801--2810}, pmid = {9826602}, timestamp = {2009-06-03T11:21:13.000+0200}, title = {Regulation of the cardiac ryanodine receptor channel by luminal {C}a$^{2+}$ involves luminal {C}a$^{2+}$ sensing sites.}, url = {http://www.biophysj.org/cgi/content/full/75/6/2801}, volume = 75, year = 1998 }