%0 Journal Article %1 Masu_2001_39727 %A Masumiya, H. %A Li, P. %A Zhang, L. %A Chen, S. R. %D 2001 %J J. Biol. Chem. %K 11507100 Acid, Alanine, Caffeine, Calcium Calcium, Channel Channel, Dose-Response Drug, Gating, Glutamic Gov't, Humans, Ion Magnesium, Mutation, Non-U.S. Receptor Relationship, Release Research Ryanodine Ryanodine, Support, %N 43 %P 39727--39735 %R 10.1074/jbc.M106557200 %T Ryanodine sensitizes the Ca$^2+$ release channel (ryanodine receptor) to Ca$^2+$ activation. %U http://dx.doi.org/10.1074/jbc.M106557200 %V 276 %X Ryanodine, a plant alkaloid, is one of the most widely used pharmacological probes for intracellular Ca$^2+$ signaling in a variety of muscle and non-muscle cells. Upon binding to the Ca$^2+$ release channel (ryanodine receptor), ryanodine causes two major changes in the channel: a reduction in single-channel conductance and a marked increase in open probability. The molecular mechanisms underlying these alterations are not well understood. In the present study, we investigated the gating behavior and Ca$^2+$ dependence of the wild type (wt) and a mutant cardiac ryanodine receptor (RyR2) after being modified by ryanodine. Single-channel studies revealed that the ryanodine-modified wt RyR2 channel was sensitive to inhibition by Mg$^2+$ and to activation by caffeine and ATP. In the presence of Mg$^2+$, the ryanodine-modified single wt RyR2 channel displayed a sigmoidal Ca$^2+$ dependence with an EC(50) value of 110 nm, whereas the ryanodine-unmodified single wt channel exhibited an EC(50) of 120 microm for Ca$^2+$ activation, indicating that ryanodine is able to increase the sensitivity of the wt RyR2 channel to Ca$^2+$ activation by approximately 1,000-fold. Furthermore, ryanodine is able to restore Ca$^2+$ activation and ligand response of the E3987A mutant RyR2 channel that has been shown to exhibit approximately 1,000-fold reduction in Ca$^2+$ sensitivity to activation. The E3987A mutation, however, affects neither (3)Hryanodine binding to, nor the stimulatory and inhibitory effects of ryanodine on, the RyR2 channel. These results demonstrate that ryanodine does not "lock" the RyR channel into an open state as generally believed; rather, it sensitizes dramatically the channel to activation by Ca$^2+$.

@article{Masu_2001_39727, abstract = {Ryanodine, a plant alkaloid, is one of the most widely used pharmacological probes for intracellular {C}a$^{2+}$ signaling in a variety of muscle and non-muscle cells. Upon binding to the {C}a$^{2+}$ release channel (ryanodine receptor), ryanodine causes two major changes in the channel: a reduction in single-channel conductance and a marked increase in open probability. The molecular mechanisms underlying these alterations are not well understood. In the present study, we investigated the gating behavior and {C}a$^{2+}$ dependence of the wild type (wt) and a mutant cardiac ryanodine receptor (RyR2) after being modified by ryanodine. Single-channel studies revealed that the ryanodine-modified wt RyR2 channel was sensitive to inhibition by {M}g$^{2+}$ and to activation by caffeine and ATP. In the presence of {M}g$^{2+}$, the ryanodine-modified single wt RyR2 channel displayed a sigmoidal {C}a$^{2+}$ dependence with an EC(50) value of 110 nm, whereas the ryanodine-unmodified single wt channel exhibited an EC(50) of 120 microm for {C}a$^{2+}$ activation, indicating that ryanodine is able to increase the sensitivity of the wt RyR2 channel to {C}a$^{2+}$ activation by approximately 1,000-fold. Furthermore, ryanodine is able to restore {C}a$^{2+}$ activation and ligand response of the E3987A mutant RyR2 channel that has been shown to exhibit approximately 1,000-fold reduction in {C}a$^{2+}$ sensitivity to activation. The E3987A mutation, however, affects neither [(3)H]ryanodine binding to, nor the stimulatory and inhibitory effects of ryanodine on, the RyR2 channel. These results demonstrate that ryanodine does not "lock" the RyR channel into an open state as generally believed; rather, it sensitizes dramatically the channel to activation by {C}a$^{2+}$.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Masumiya, H. and Li, P. and Zhang, L. and Chen, S. R.}, biburl = {https://www.bibsonomy.org/bibtex/2d0197cd8b75e71c0cc59bed2183ea56f/hake}, description = {The whole bibliography file I use.}, doi = {10.1074/jbc.M106557200}, interhash = {f7773efa18f64eed37bd25659c42da71}, intrahash = {d0197cd8b75e71c0cc59bed2183ea56f}, journal = {J. Biol. Chem.}, keywords = {11507100 Acid, Alanine, Caffeine, Calcium Calcium, Channel Channel, Dose-Response Drug, Gating, Glutamic Gov't, Humans, Ion Magnesium, Mutation, Non-U.S. Receptor Relationship, Release Research Ryanodine Ryanodine, Support,}, month = Oct, number = 43, pages = {39727--39735}, pii = {M106557200}, pmid = {11507100}, timestamp = {2009-06-03T11:21:22.000+0200}, title = {Ryanodine sensitizes the {C}a$^{2+}$ release channel (ryanodine receptor) to {C}a$^{2+}$ activation.}, url = {http://dx.doi.org/10.1074/jbc.M106557200}, volume = 276, year = 2001 }