scholarly journals The diamide insecticide chlorantraniliprole increases the single-channel current activity of the mammalian skeletal muscle ryanodine receptor

2019 ◽  
Vol 38 (02) ◽  
pp. 183-186
Author(s):  
Z. É. Magyar ◽  
G. Diszházi ◽  
J. Péli-Szabó ◽  
P. Szentesi ◽  
C. Collet ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Single Channel ◽  
Mammalian Skeletal Muscle ◽  
Channel Current ◽  
Single Channel Current ◽  
Current Activity ◽  
Diamide Insecticide

Postulated role of interdomain interactions within the type 1 ryanodine receptor in the low gain of Ca2+-induced Ca2+ release activity of mammalian skeletal muscle sarcoplasmic reticulum

2005 ◽  
Vol 288 (6) ◽  
pp. C1222-C1230 ◽  
Author(s):  
Takashi Murayama ◽  
Toshiharu Oba ◽  
Shigeki Kobayashi ◽  
Noriaki Ikemoto ◽  
Yasuo Ogawa
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Malignant Hyperthermia ◽  
Ryanodine Receptor ◽  
Single Channel ◽  
Common Mechanism ◽  
Mammalian Skeletal Muscle ◽  
Selective Stabilization ◽  
Interdomain Interactions

Ryanodine receptor (RyR) type 1 (RyR1) exhibits a markedly lower gain of Ca2+-induced Ca2+ release (CICR) activity than RyR type 3 (RyR3) in the sarcoplasmic reticulum (SR) of mammalian skeletal muscle (selective stabilization of the RyR1 channel), and this reduction in the gain is largely eliminated using 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS). We have investigated whether the hypothesized interdomain interactions within RyR1 are involved in the selective stabilization of the channel using [3H]ryanodine binding, single-channel recordings, and Ca2+ release from the SR vesicles. Like CHAPS, domain peptide 4 (DP4, a synthetic peptide corresponding to the Leu2442-Pro2477 region of RyR1), which seems to destabilize the interdomain interactions, markedly stimulated RyR1 but not RyR3. Their activating effects were saturable and nonadditive. Dantrolene, a potent inhibitor of RyR1 used to treat malignant hyperthermia, reversed the effects of DP4 or CHAPS in an identical manner. These findings indicate that RyR1 is activated by DP4 and CHAPS through a common mechanism that is probably mediated by the interdomain interactions. DP4 greatly increased [3H]ryanodine binding to RyR1 with only minor alterations in the sensitivity to endogenous CICR modulators (Ca2+, Mg2+, and adenine nucleotide). However, DP4 sensitized RyR1 four- to six-fold to caffeine in the caffeine-induced Ca2+ release. Thus the gain of CICR activity critically determines the magnitude and threshold of Ca2+ release by drugs such as caffeine. These findings suggest that the low CICR gain of RyR1 is important in normal Ca2+ handling in skeletal muscle and that perturbation of this state may result in muscle diseases such as malignant hyperthermia.

scholarly journals Competitive Mg2+ block of a large-conductance, Ca(2+)-activated K+ channel in rat skeletal muscle. Ca2+, Sr2+, and Ni2+ also block.

1991 ◽  
Vol 98 (1) ◽  
pp. 163-181 ◽  
Author(s):  
W B Ferguson
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Competitive Inhibition ◽  
Reversal Potential ◽  
K Channel ◽  
Dependent Manner ◽  
Rat Skeletal Muscle ◽  
Patch Clamp Technique ◽  
Channel Current ◽  
Single Channel Current

The patch-clamp technique was used to investigate the effect of intracellular Mg2+ (Mgi2+) on the conductance of the large-conductance, Ca(2+)-activated K+ channel in cultured rat skeletal muscle. Measurements of single-channel current amplitudes indicated that Mgi2+ decreased the K+ currents in a concentration-dependent manner. Increasing Mgi2+ from 0 to 5, 10, 20, and 50 mM decreased channel currents by 34%, 44%, 56%, and 73%, respectively, at +50 mV. The magnitude of the Mgi2+ block increased with depolarization. For membrane potentials of -50, +50, and +90 mV, 20 mM Mgi2+ reduced the currents 22%, 56%, and 70%, respectively. Mgi2+ did not change the reversal potential, indicating that Mg2+ does not permeate the channel. The magnitude of the Mgi2+ block decreased as the concentration of K+ was increased. At a membrane potential of +50 mv, 20 mM Mgi2+ reduced the currents 71%, 56%, and 25% for Ki+ of 75, 150, and 500 mM. These effects of Mgi2+, voltage, and K+ were totally reversible. Although the Woodhull blocking model could approximate the voltage and concentration effects of the Mgi2+ block (Kd approximately 30 mM with 150 mM symmetrical K+; electrical distance approximately 0.22 from the inner surface), the Woodhull model could not account for the effects of K+. Double reciprocal plots of 1/single channel current vs. 1/[K+] in the presence and absence of Mgi2+, indicated that the Mgi2+ block is consistent with apparent competitive inhibition between Mgi2+ and Ki+. Cai2+, Nii2+, and Sri2+ were found to have concentration- and voltage-dependent blocking effects similar, but not identical, to those of Mgi2+. These observations suggest the blocking by Mgi2+ of the large-conductance, Ca(2+)-activated K+ channel is mainly nonspecific, competitive with K+, and at least partially electrostatic in nature.

scholarly journals Triadin Binding to the C-Terminal Luminal Loop of the Ryanodine Receptor is Important for Skeletal Muscle Excitation–Contraction Coupling

2007 ◽  
Vol 130 (4) ◽  
pp. 365-378 ◽  
Author(s):  
Sanjeewa A. Goonasekera ◽  
Nicole A. Beard ◽  
Linda Groom ◽  
Takashi Kimura ◽  
Alla D. Lyfenko ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Calcium Release ◽  
Striated Muscle ◽  
Single Channel ◽  
Triple Mutant ◽  
Double Mutation ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Functional Studies

Ca2+ release from intracellular stores is controlled by complex interactions between multiple proteins. Triadin is a transmembrane glycoprotein of the junctional sarcoplasmic reticulum of striated muscle that interacts with both calsequestrin and the type 1 ryanodine receptor (RyR1) to communicate changes in luminal Ca2+ to the release machinery. However, the potential impact of the triadin association with RyR1 in skeletal muscle excitation–contraction coupling remains elusive. Here we show that triadin binding to RyR1 is critically important for rapid Ca2+ release during excitation–contraction coupling. To assess the functional impact of the triadin-RyR1 interaction, we expressed RyR1 mutants in which one or more of three negatively charged residues (D4878, D4907, and E4908) in the terminal RyR1 intraluminal loop were mutated to alanines in RyR1-null (dyspedic) myotubes. Coimmunoprecipitation revealed that triadin, but not junctin, binding to RyR1 was abolished in the triple (D4878A/D4907A/E4908A) mutant and one of the double (D4907A/E4908A) mutants, partially reduced in the D4878A/D4907A double mutant, but not affected by either individual (D4878A, D4907A, E4908A) mutations or the D4878A/E4908A double mutation. Functional studies revealed that the rate of voltage- and ligand-gated SR Ca2+ release were reduced in proportion to the degree of interruption in triadin binding. Ryanodine binding, single channel recording, and calcium release experiments conducted on WT and triple mutant channels in the absence of triadin demonstrated that the luminal loop mutations do not directly alter RyR1 function. These findings demonstrate that junctin and triadin bind to different sites on RyR1 and that triadin plays an important role in ensuring rapid Ca2+ release during excitation–contraction coupling in skeletal muscle.

Effect of Prozac on whole cell ionic currents in lens and corneal epithelia

1995 ◽  
Vol 269 (1) ◽  
pp. C250-C256 ◽  
Author(s):  
J. L. Rae ◽  
A. Rich ◽  
A. C. Zamudio ◽  
O. A. Candia
Keyword(s):  
Potassium Channels ◽  
Single Channel ◽  
Ionic Currents ◽  
Current Amplitude ◽  
Human Lens ◽  
Delayed Rectifier ◽  
Open Probability ◽  
Channel Current ◽  
Single Channel Current ◽  
Ionic Conductances

Prozac (fluoxetine), a compound used therapeutically in humans to combat depression, has substantial effects on ionic conductances in rabbit corneal epithelial cells and in cultured human lens epithelium. In corneal epithelium, it reduces the current due to the large-conductance potassium channels that dominate this preparation. Its effects seem largely to decrease the open probability while leaving the single-channel current amplitude unaltered. In cultured human epithelium, currents from calcium-activated potassium channels and inward rectifiers are unaffected by Prozac. Delayed-rectifier potassium currents are reduced by Prozac in a complicated way that involves both gating and single-channel current amplitude. Fast tetrodotoxin-blockable sodium currents are also decreased by Prozac in this preparation. For all of these ion conductance effects, Prozac concentrations of 10(-5) to 10(-4) M are required. Whereas these levels are 10- to 100-fold higher than the plasma levels achieved in therapeutic use in humans, they are comparable to or less than levels needed for many other blockers of the ionic conductances studied here.

Properties and distribution of single voltage-gated calcium channels in adult hippocampal neurons

1990 ◽  
Vol 64 (1) ◽  
pp. 91-104 ◽  
Author(s):  
R. E. Fisher ◽  
R. Gray ◽  
D. Johnston
Keyword(s):  
Guinea Pig ◽  
Calcium Channels ◽  
Single Channel ◽  
Cell Types ◽  
Voltage Gated ◽  
Channel Current ◽  
Single Channel Current ◽  
Voltage Gated Calcium Channels ◽  
Large Conductance Channel ◽  
Small Conductance

1. The properties of single voltage-gated calcium channels were investigated in acutely exposed CA3 and CA1 pyramidal neurons and granule cells of area dentata in the adult guinea pig hippocampal formation. 2. Guinea pig hippocampal slices were prepared in a conventional manner, then treated with proteolytic enzymes and gently shaken to expose the somata of the three cell types studied. Standard patch-clamp techniques were used to record current flow through calcium channels in cell-attached membrane patches with isotonic barium as the charge carrier. 3. Single-channel current amplitudes were measured at different membrane potentials. Single-channel current-voltage plots were constructed and single-channel slope conductances were found to fall into three classes. These were (approximately) 8, 14, and 25 pS, and were observed in all three cell types. 4. The three groups of channels differed from each other in voltage dependence of activation: from a holding potential of -80, the small-conductance channel began to activate at about -40 to -30 mV, the medium-conductance channel at about -20 mV, and the large-conductance channel at approximately 0 mV. 5. Ensemble averages of single-channel currents during voltage steps revealed differences in voltage-dependent inactivation. The small-conductance channel inactivated completely within approximately 50 ms during steps from -80 to -10 mV or more positive. Steps to less positive potentials resulted in less inactivation. The medium-conductance channel displayed variable inactivation during steps from -80 to 0 mV. Inactivation of this channel during a 160-ms step ranged from virtually zero to approximately 100%. The large-conductance channel displayed no significant inactivation during steps as long as 400 ms. 6. The large-conductance channel was strikingly affected by the dihydropyridine agonist Bay K8644 (0.5-2.0 microM), resulting in a high probability of channel opening, prolonged openings, and an apparent increase in the number of channels available for activation. The medium and small-conductance channels were not noticeably affected by the drug. 7. The large-conductance channel could be induced to open at very negative membrane potentials by holding the patch for several seconds at 20 or 30 mV and stepping to -30 or -40 mV. This process was enhanced by Bay K8644, resulting in prolonged openings at potentials as negative as -100 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Time-dependent expression of ryanodine receptors in sea urchin eggs, zygotes and early embryos

Zygote ◽  
2021 ◽  
pp. 1-4
Author(s):  
G. Percivale ◽  
C. Angelini ◽  
C. Falugi ◽  
C. Picco ◽  
G. Prestipino
Keyword(s):  
Single Channel ◽  
Ryanodine Receptors ◽  
Paracentrotus Lividus ◽  
Current Fluctuations ◽  
Calcium Dependent ◽  
Channel Current ◽  
Single Channel Current ◽  
Electrophysiological Recordings ◽  
Early Embryos ◽  
Zygote Stage

Summary In this work, the presence of calcium-dependent calcium channels and their receptors (RyR) has been investigated in Paracentrotus lividus eggs and early embryos, from unfertilized egg to four-blastomere stages. Electrophysiological recordings of RyR single-channel current fluctuations showed that RyRs are functional during the first developmental events with a maximum at zygote stage, c. 40 min after fertilization, corresponding to the first cleavage. The nature of vertebrate-like RyRs active at this stage was established by specific activation/blockade experiments.

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