scholarly journals Niflumic acid differentially modulates two types of skeletal ryanodine-sensitive Ca2+-release channels

1997 ◽  
Vol 273 (5) ◽  
pp. C1588-C1595 ◽  
Author(s):  
Toshiharu Oba
Keyword(s):  
Lipid Bilayers ◽  
Ryanodine Receptors ◽  
Reversal Potential ◽  
Current Treatment ◽  
Ruthenium Red ◽  
Niflumic Acid ◽  
Open Probability ◽  
Activation Curve ◽  
Release Channel ◽  
Channel Activation

The effects of niflumic acid on ryanodine receptors (RyRs) of frog skeletal muscle were studied by incorporating sarcoplasmic reticulum (SR) vesicles into planar lipid bilayers. Frog muscle had two distinct types of RyRs in the SR: one showed a bell-shaped channel activation curve against cytoplasmic Ca2+ or niflumic acid, and its mean open probability ( P o) was increased by perchlorate at 20–30 mM (termed “α-like” RyR); the other showed a sigmoidal activation curve against Ca2+ or niflumic acid, with no effect on perchlorate (termed “β-like” RyR). The unitary conductance and reversal potential of both channel types were unaffected after exposure to niflumic acid when clamped at 0 mV. When clamped at more positive potentials, the β-like RyR channel rectified this, increasing the unitary current. Treatment with niflumic acid did not inhibit the response of both channels to Ca2+ release channel modulators such as caffeine, ryanodine, and ruthenium red. The different effects of niflumic acid on P o and the unitary current amplitude in both types of channels may be attributable to the lack or the presence of inactivation sites and/or distinct responses to agonists.

Sulfhydryls associated with H2O2-induced channel activation are on luminal side of ryanodine receptors

1998 ◽  
Vol 274 (4) ◽  
pp. C914-C921 ◽  
Author(s):  
Toshiharu Oba ◽  
Tatsuya Ishikawa ◽  
Mamoru Yamaguchi
Keyword(s):  
Lipid Bilayers ◽  
Ryanodine Receptors ◽  
Reversal Potential ◽  
Skinned Fibers ◽  
Open Probability ◽  
Release Channel ◽  
Channel Activation ◽  
Channel Current ◽  
Open Time ◽  
Luminal Side

The mechanism underlying H2O2-induced activation of frog skeletal muscle ryanodine receptors was studied using skinned fibers and by measuring single Ca2+-release channel current. Exposure of skinned fibers to 3–10 mM H2O2 elicited spontaneous contractures. H2O2 at 1 mM potentiated caffeine contracture. When the Ca2+-release channels were incorporated into lipid bilayers, open probability ( P o) and open time constants were increased on intraluminal addition of H2O2 in the presence of cis catalase, but unitary conductance and reversal potential were not affected. Exposure to cis H2O2 at 1.5 mM failed to activate the channel in the presence of trans catalase. Application of 1.5 mM H2O2 to the transside of a channel that had been oxidized by cis p-chloromercuriphenylsulfonic acid (pCMPS; 50 μM) still led to an increase in P o, comparable to that elicited by trans 1.5 mM H2O2 without pCMPS. Addition of cis pCMPS to channels that had been treated with or without trans H2O2 rapidly resulted in high P o followed by closure of the channel. These results suggest that oxidation of luminal sulfhydryls in the Ca2+-release channel may contribute to H2O2-induced channel activation and muscle contracture.

Modulation of frog skeletal muscle Ca2+ release channel gating by anion channel blockers

1996 ◽  
Vol 271 (3) ◽  
pp. C819-C824 ◽  
Author(s):  
T. Oba ◽  
M. Koshita ◽  
D. F. Van Helden
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptors ◽  
Reversal Potential ◽  
Niflumic Acid ◽  
Disulfonic Acid ◽  
Frog Skeletal Muscle ◽  
Open Probability ◽  
Release Channel ◽  
Unitary Conductance ◽  
Open Time

Effects of niflumic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) on frog skeletal muscle ryanodine receptors have been studied by incorporating sarcoplasmic reticulum vesicles into planar lipid bilayers. Niflumic acid increased the mean open probability (Po) at 10 microM and decreased Po at 100 microM with no change in open time constants, unitary conductance, and reversal potential. The Po was augmented by DIDS at 5-200 microM without affecting either unitary conductance or reversal potential. DIDS induced a new third open time constant, probably contributing to a long-lived open state. Channels modified by niflumic acid or DIDS still responded to Ca2+ release channel modulators. These results provide evidence that niflumic acid and DIDS modify the gating mechanism of ryanodine receptors without affecting binding sites to the modulators and the physical pathway of the conducting pore. p-Chloromercuriphenyl sulfonic acid (pCMPS) transiently increased the Po. The channel modified by DIDS responded to pCMPS, whereas that by ryanodine did not. The long open state of the channel induced by DIDS is produced by a quite different mechanism(s) from that by ryanodine. Contrary to cardiac ryanodine receptors, Po of skeletal muscle channels was independent of voltage after DIDS modification.

cADP-ribose activates reconstituted ryanodine receptors from coronary arterial smooth muscle

2001 ◽  
Vol 280 (1) ◽  
pp. H208-H215 ◽  
Author(s):  
Pin-Lan Li ◽  
Wang-Xian Tang ◽  
Hector H. Valdivia ◽  
Ai-Ping Zou ◽  
William B. Campbell
Keyword(s):  
Smooth Muscle ◽  
Lipid Bilayers ◽  
Ryanodine Receptors ◽  
Fold Increase ◽  
Ruthenium Red ◽  
Dependent Manner ◽  
High Concentration ◽  
Open Probability ◽  
Arterial Smooth Muscle ◽  
Concentration Dependent Manner

The present study was designed to test the hypothesis that cADP-ribose (cADPR) increases Ca2+release through activation of ryanodine receptors (RYR) on the sarcoplasmic reticulum (SR) in coronary arterial smooth muscle cells (CASMCs). We reconstituted RYR from the SR of CASMCs into planar lipid bilayers and examined the effect of cADPR on the activity of these Ca2+ release channels. In a symmetrical cesium methanesulfonate configuration, a 245 pS Cs+ current was recorded. This current was characterized by the formation of a subconductance and increase in the open probability (NPo) of the channels in the presence of ryanodine (0.01–1 μM) and imperatoxin A (100 nM). A high concentration of ryanodine (50 μM) and ruthenium red (40–80 μM) substantially inhibited the activity of RYR/Ca2+ release channels. Caffeine (0.5–5 mM) markedly increased the NPo of these Ca2+release channels of the SR, but d- myo-inositol 1,4,5-trisphospate and heparin were without effect. Cyclic ADPR significantly increased the NPo of these Ca2+release channels of SR in a concentration-dependent manner. Addition of cADPR (0.01 μM) into the cis bath solution produced a 2.9-fold increase in the NPo of these RYR/Ca2+release channels. An eightfold increase in the NPo of the RYR/Ca2+ release channels (0.0056 ± 0.001 vs. 0.048 ± 0.017) was observed at a concentration of cADPR of 1 μM. The effect of cADPR was completely abolished by ryanodine (50 μM). In the presence of cADPR, Ca2+-induced activation of these channels was markedly enhanced. These results provide evidence that cADPR activates RYR/Ca2+ release channels on the SR of CASMCs. It is concluded that cADPR stimulates Ca2+ release through the activation of RYRs on the SR of these smooth mucle cells.

Single cardiac sarcoplasmic reticulum Ca2+-release channel: activation by caffeine

1989 ◽  
Vol 256 (2) ◽  
pp. H328-H333 ◽  
Author(s):  
E. Rousseau ◽  
G. Meissner
Keyword(s):  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Ruthenium Red ◽  
Planar Lipid Bilayers ◽  
Release Channel ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Channel Activation ◽  
Contraction Coupling

Caffeine is thought to affect excitation-contraction coupling in cardiac muscle by activating the sarcoplasmic reticulum (SR) Ca2+-release channel. The effect of caffeine at the single channel level was studied by incorporating canine cardiac SR vesicles into planar lipid bilayers. Cardiac Ca2+-release channels were activated in a steady-state manner by millimolar cis-caffeine and displayed a unitary conductance (77 pS in 50 mM Ca2+ trans) similar to that previously observed for the Ca2+-activated cardiac channel. The caffeine-activated channel was moderately sensitive to the voltage applied across the bilayer, was sensitive to further activation by ATP, and was inhibited by Mg2+ and ruthenium red. Kinetic analysis showed that at low Ca2+ concentration, caffeine activated the channel by increasing the frequency and the duration of open events.

Ryanodine modifies conductance and gating behavior of single Ca2+ release channel

1987 ◽  
Vol 253 (3) ◽  
pp. C364-C368 ◽  
Author(s):  
E. Rousseau ◽  
J. S. Smith ◽  
G. Meissner
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Ruthenium Red ◽  
Planar Lipid Bilayers ◽  
Open Probability ◽  
Release Channel ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling

Ryanodine affects excitation-contraction coupling in skeletal and cardiac muscle by specifically interacting with the sarcoplasmic reticulum (SR) Ca2+ release channel. The effect of the drug at the single channel level was studied by incorporating skeletal and cardiac SR vesicles into planar lipid bilayers. The two channels were activated by micromolar free Ca2+ and millimolar ATP and inhibited by Mg2+ and ruthenium red. Addition of micromolar concentrations of ryanodine decreased about twofold the unit conductance of the Ca2+- and ATP-activated skeletal and cardiac channels. A second effect of ryanodine was to increase the open probability (Po) of the channels in such a way that Po was close to unity under a variety of activating and inactivating conditions. The effects of ryanodine were long lasting in that removal of ryanodine by perfusion did not return the channels into their fully conducting state.

scholarly journals Activation of Slo2.1 channels by niflumic acid

2010 ◽  
Vol 135 (3) ◽  
pp. 275-295 ◽  
Author(s):  
Li Dai ◽  
Vivek Garg ◽  
Michael C. Sanguinetti
Keyword(s):  
Voltage Dependence ◽  
Reversal Potential ◽  
Niflumic Acid ◽  
Flufenamic Acid ◽  
Channel Activation ◽  
Outward Currents ◽  
Transmembrane Voltage ◽  
High K ◽  
Charged Residues ◽  
K Current

Slo2.1 channels conduct an outwardly rectifying K+ current when activated by high [Na+]i. Here, we show that gating of these channels can also be activated by fenamates such as niflumic acid (NFA), even in the absence of intracellular Na+. In Xenopus oocytes injected with <10 ng cRNA, heterologously expressed human Slo2.1 current was negligible, but rapidly activated by extracellular application of NFA (EC50 = 2.1 mM) or flufenamic acid (EC50 = 1.4 mM). Slo2.1 channels activated by 1 mM NFA exhibited weak voltage dependence. In high [K+]e, the conductance–voltage (G-V) relationship had a V1/2 of +95 mV and an effective valence, z, of 0.48 e. Higher concentrations of NFA shifted V1/2 to more negative potentials (EC50 = 2.1 mM) and increased the minimum value of G/Gmax (EC50 = 2.4 mM); at 6 mM NFA, Slo2.1 channel activation was voltage independent. In contrast, V1/2 of the G-V relationship was shifted to more positive potentials when [K+]e was elevated from 1 to 300 mM (EC50 = 21.2 mM). The slope conductance measured at the reversal potential exhibited the same [K+]e dependency (EC50 = 23.5 mM). Conductance was also [Na+]e dependent. Outward currents were reduced when Na+ was replaced with choline or mannitol, but unaffected by substitution with Rb+ or Li+. Neutralization of charged residues in the S1–S4 domains did not appreciably alter the voltage dependence of Slo2.1 activation. Thus, the weak voltage dependence of Slo2.1 channel activation is independent of charged residues in the S1–S4 segments. In contrast, mutation of R190 located in the adjacent S4–S5 linker to a neutral (Ala or Gln) or acidic (Glu) residue induced constitutive channel activity that was reduced by high [K+]e. Collectively, these findings indicate that Slo2.1 channel gating is modulated by [K+]e and [Na+]e, and that NFA uncouples channel activation from its modulation by transmembrane voltage and intracellular Na+.

scholarly journals Interdomain Interactions within Ryanodine Receptors Regulate Ca2+ Spark Frequency in Skeletal Muscle

2001 ◽  
Vol 119 (1) ◽  
pp. 15-32 ◽  
Author(s):  
Alexander Shtifman ◽  
Christopher W. Ward ◽  
Takeshi Yamamoto ◽  
Jianli Wang ◽  
Beth Olbinski ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Lipid Bilayers ◽  
Laser Scanning ◽  
Muscle Fibers ◽  
Mammalian Skeletal Muscle ◽  
Open Probability ◽  
Release Channel ◽  
Pronounced Increase ◽  
Open Time ◽  
Interdomain Interactions

DP4 is a 36-residue synthetic peptide that corresponds to the Leu2442-Pro2477 region of RyR1 that contains the reported malignant hyperthermia (MH) mutation site. It has been proposed that DP4 disrupts the normal interdomain interactions that stabilize the closed state of the Ca2+ release channel (Yamamoto, T., R. El-Hayek, and N. Ikemoto. 2000. J. Biol. Chem. 275:11618–11625). We have investigated the effects of DP4 on local SR Ca2+ release events (Ca2+ sparks) in saponin-permeabilized frog skeletal muscle fibers using laser scanning confocal microscopy (line-scan mode, 2 ms/line), as well as the effects of DP4 on frog SR vesicles and frog single RyR Ca2+ release channels reconstituted in planar lipid bilayers. DP4 caused a significant increase in Ca2+ spark frequency in muscle fibers. However, the mean values of the amplitude, rise time, spatial half width, and temporal half duration of the Ca2+ sparks, as well as the distribution of these parameters, remained essentially unchanged in the presence of DP4. Thus, DP4 increased the opening rate, but not the open time of the RyR Ca2+ release channel(s) generating the sparks. DP4 also increased [3H]ryanodine binding to SR vesicles isolated from frog and mammalian skeletal muscle, and increased the open probability of frog RyR Ca2+ release channels reconstituted in bilayers, without changing the amplitude of the current through those channels. However, unlike in Ca2+ spark experiments, DP4 produced a pronounced increase in the open time of channels in bilayers. The same peptide with an Arg17 to Cys17 replacement (DP4mut), which corresponds to the Arg2458-to-Cys2458 mutation in MH, did not produce a significant effect on RyR activation in muscle fibers, bilayers, or SR vesicles. Mg2+ dependence experiments conducted with permeabilized muscle fibers indicate that DP4 preferentially binds to partially Mg2+-free RyR(s), thus promoting channel opening and production of Ca2+ sparks.

scholarly journals Nicotinic acid–adenine dinucleotide phosphate activates the skeletal muscle ryanodine receptor

2002 ◽  
Vol 367 (2) ◽  
pp. 423-431 ◽  
Author(s):  
Martin HOHENEGGER ◽  
Josef SUKO ◽  
Regina GSCHEIDLINGER ◽  
Helmut DROBNY ◽  
Andreas ZIDAR
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Nicotinic Acid ◽  
Ryanodine Receptor ◽  
Spatial Information ◽  
Single Channel ◽  
Reversal Potential ◽  
Open Probability ◽  
Release Channel

Calcium is a universal second messenger. The temporal and spatial information that is encoded in Ca2+-transients drives processes as diverse as neurotransmitter secretion, axonal outgrowth, immune responses and muscle contraction. Ca2+-release from intracellular Ca2+ stores can be triggered by diffusible second messengers like InsP3, cyclic ADP-ribose or nicotinic acid—adenine dinucleotide phosphate (NAADP). A target has not yet been identified for the latter messenger. In the present study we show that nanomolar concentrations of NAADP trigger Ca2+-release from skeletal muscle sarcoplasmic reticulum. This was due to a direct action on the Ca2+-release channel/ryanodine receptor type-1, since in single channel recordings, NAADP increased the open probability of the purified channel protein. The effects of NAADP on Ca2+-release and open probability of the ryanodine receptor occurred over a similar concentration range (EC5030nM) and were specific because (i) they were blocked by Ruthenium Red and ryanodine, (ii) the precursor of NAADP, NADP, was ineffective at equimolar concentrations, (iii) NAADP did not affect the conductance and reversal potential of the ryanodine receptor. Finally, we also detected an ADP-ribosyl cyclase activity in the sarcoplasmic reticulum fraction of skeletal muscle. This enzyme was not only capable of synthesizing cyclic GDP-ribose but also NAADP, with an activity of 0.25nmol/mg/min. Thus, we conclude that NAADP is generated in the vicinity of type 1 ryanodine receptor and leads to activation of this ion channel.

Differential acidic pH sensitivity of delta F508 CFTR Cl- channel activity in lipid bilayers

1994 ◽  
Vol 266 (3) ◽  
pp. C870-C875 ◽  
Author(s):  
A. M. Sherry ◽  
J. Cuppoletti ◽  
D. H. Malinowska
Keyword(s):  
Cystic Fibrosis ◽  
Lipid Bilayers ◽  
Plasma Membranes ◽  
Reversal Potential ◽  
Fold Increase ◽  
Xenopus Laevis Oocyte ◽  
Open Probability ◽  
Cl Channel ◽  
Open Time ◽  
Intracellular Organelles

Cystic fibrosis transmembrane conductance regulator (CFTR) is present in acidic intracellular vesicles. Human normal and delta F508 CFTR Cl- channel characteristics at pH 7.4 and pH 4.5 were determined by fusing Xenopus laevis oocyte plasma membranes containing the expressed channels to planar lipid bilayers. At pH 7.4, both channels exhibited linear current-voltage curves, a 10 +/- 0.3-pS conductance using 800 mM CsCl, and a 9:1 Cl-/Cs+ discrimination ratio obtained from a 32 +/- 2 mV reversal potential with a fivefold gradient. At -80 mV, the open probability (Po) of mutant CFTR was 53% that of normal CFTR. Reduction of the trans-pH from 7.4 to 4.5 had no effect on the above characteristics except for Po, where it caused a 47% reduction in normal CFTR Po (due to a 75% decrease in mean open time) and a 75% reduction in delta F508 CFTR Po (due to a 6-fold increase in mean closed time). Normal CFTR can thus function in the environment of acidic intracellular organelles, whereas activity of mutant CFTR would be greatly reduced. These results may be of significance to understanding the cystic fibrosis defect.

BAY K 8644 and ClO4- potentiate caffeine contracture without Ca2+ release channel activation

1997 ◽  
Vol 272 (1) ◽  
pp. C41-C47 ◽  
Author(s):  
T. Oba ◽  
M. Koshita ◽  
T. Aoki ◽  
M. Yamaguchi
Keyword(s):  
Time Constant ◽  
Bay K 8644 ◽  
Open Probability ◽  
Release Channel ◽  
Channel Activation ◽  
Channel Current ◽  
Caffeine Contracture ◽  
Dihydropyridine Receptors ◽  
Open Time ◽  
External K

Effects of perchlorate (ClO4-) and BAY K 8644 on caffeine contracture and Ca2+ release channel current were studied in frog skeletal muscle. Single fibers produced a small transient contracture on addition of 2.2 mM caffeine. ClO4 at 10 mM enhanced caffeine contracture 3.7-fold. This effect was inhibited by 10 microM nifedipine pretreatment. An increase in caffeine contracture was also obtained after exposure to 0.1 microM BAY K 8644 for 1 h. At 20 mM, external K+ potentiated caffeine contracture 2.2-fold. ClO4- (< 10 mM) and BAY K 8644 (0.1-1 microM) did not affect open probability (Po), unitary conductance, and open and closed time constants of the Ca2+ release channel current. BAY K 8644 at 0.1 microM did not further enhance the channel that had been activated by 2 mM caffeine. However, 20-30 mM ClO4 increased Po significantly and led the channel to a long open state by increasing the slow open time constant and decreasing the fast closed time constant. These results suggest that binding of ClO4 and BAY K 8644 to dihydropyridine receptors elicits a further increase in Ca2+ release from the sarcoplasmic reticulum.

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