Mechanisms of Pi regulation of the skeletal muscle SR Ca2+ release channel

2000 ◽  
Vol 278 (3) ◽  
pp. C601-C611 ◽  
Author(s):  
Edward M. Balog ◽  
Bradley R. Fruen ◽  
Patricia K. Kane ◽  
Charles F. Louis
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Adenine Nucleotides ◽  
Muscle Fibers ◽  
Open Probability ◽  
Release Channel ◽  
High Concentrations ◽  
Channel Open Time ◽  
Stimulation Of

Inorganic phosphate (Pi) accumulates in the fibers of actively working muscle where it acts at various sites to modulate contraction. To characterize the role of Pi as a regulator of the sarcoplasmic reticulum (SR) calcium (Ca2+) release channel, we examined the action of Pi on purified SR Ca2+ release channels, isolated SR vesicles, and skinned skeletal muscle fibers. In single channel studies, addition of Pi to the cis chamber increased single channel open probability ( P o; 0.079 ± 0.020 in 0 Pi, 0.157 ± 0.034 in 20 mM Pi) by decreasing mean channel closed time; mean channel open times were unaffected. In contrast, the ATP analog, β,γ-methyleneadenosine 5′-triphosphate (AMP-PCP), enhanced P o by increasing single channel open time and decreasing channel closed time. Pi stimulation of [3H]ryanodine binding by SR vesicles was similar at all concentrations of AMP-PCP, suggesting Pi and adenine nucleotides act via independent sites. In skinned muscle fibers, 40 mM Pi enhanced Ca2+-induced Ca2+ release, suggesting an in situ stimulation of the release channel by high concentrations of Pi. Our results support the hypothesis that Pi may be an important endogenous modulator of the skeletal muscle SR Ca2+ release channel under fatiguing conditions in vivo, acting via a mechanism distinct from adenine nucleotides.

Functional sensitivity of the native skeletal Ca2+-release channel to divalent cations and the Mg–ATP complex

1992 ◽  
Vol 70 (3) ◽  
pp. 394-402 ◽  
Author(s):  
Eric Rousseau ◽  
Janet Pinkos ◽  
Diane Savaria
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Lipid Bilayers ◽  
Divalent Cation ◽  
Single Channel ◽  
Adenine Nucleotides ◽  
Buffer System ◽  
Open Probability ◽  
Release Channel ◽  
Gating Mechanism

Sarcoplasmic reticulum (SR) vesicles, prepared from rabbit skeletal muscle, were characterized by functional and binding assays and incorporated into planar lipid bilayers. Single-channel activity was recorded in an asymmetric calcium buffer system and studied under voltage clamp conditions. Under these experimental conditions, a large conductance (100 pS in 50 mM Ca2+trans) divalent cation selective channel displaying high ruthenium red and low Ca2+ sensitivity was identified. This pathway has been previously described as the Ca2+-release channel of the SR of skeletal muscle. We now report that in the presence of a Mg–ATP complex, the Ca2+ sensitivity of the open probability of this channel is increased. Furthermore, we show that micromolar cis Sr2+ concentrations also activated the Ca2+-release channel. The open probability of the Sr2+-activated channel was increased in the presence of a 2 mM Mg–ATP complex and adenine nucleotides on the cytoplasmic face of the Ca2+-release channel. These results were confirmed by isotopic flux measurements using passively 45Ca2+-loaded vesicles. In the latter case, the presence of extra vesicular AMP-PCP (the nonhydroly sable ATP analog) enhanced the percentage of 45Ca2+ release induced either by Ca2+ or Sr2+ activation. In conclusion our findings emphasize the fact that the divalent cation activation of the Ca2+-release channel may be induced by Ca2+ and Sr2+, but not by Ba2+, in the presence of adenine nucleotides. Furthermore, they support the view that in situ Ca2+ and Mg–ATP complexes are involved in modulating the gating mechanism of this specific pathway.Key words: Ca2+ release, sarcoplasmic reticulum, planar lipid bilayer, strontium.

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.

Lactate inhibits Ca2+-activated Ca2+-channel activity from skeletal muscle sarcoplasmic reticulum

1997 ◽  
Vol 82 (2) ◽  
pp. 447-452 ◽  
Author(s):  
Terence G. Favero ◽  
, Anthony C. Zable ◽  
, David Colter ◽  
Jonathan J. Abramson
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Single Channel ◽  
Channel Activity ◽  
Release Channel ◽  
Muscle Lactate ◽  
Tension Development ◽  
Contraction Coupling ◽  
Single Channel Activity ◽  
High Concentrations

Favero, Terence G., Anthony C. Zable, David Colter, and Jonathan J. Abramson. Lactate inhibits Ca2+-activated Ca2+-channel activity from skeletal muscle sarcoplasmic reticulum. J. Appl. Physiol. 82(2): 447–452, 1997.—Sarcoplasmic reticulum (SR) Ca2+-release channel function is modified by ligands that are generated during about of exercise. We have examined the effects of lactate on Ca2+- and caffeine-stimulated Ca2+ release, [3H]ryanodine binding, and single Ca2+-release channel activity of SR isolated from rabbit white skeletal muscle. Lactate, at concentrations from 10 to 30 mM, inhibited Ca2+- and caffeine-stimulated [3H]ryanodine binding to and inhibited Ca2+- and caffeine-stimulated Ca2+ release from SR vesicles. Lactate also inhibited caffeine activation of single-channel activity in bilayer reconstitution experiments. These findings suggest that intense muscle activity, which generates high concentrations of lactate, will disrupt excitation-contraction coupling. This may lead to decreases in Ca2+ transients promoting a decline in tension development and contribute to muscle fatigue.

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.

scholarly journals Effects of dihydropyridine receptor II-III loop peptides on Ca2+ release in skinned skeletal muscle fibers

2000 ◽  
Vol 279 (4) ◽  
pp. C891-C905 ◽  
Author(s):  
Graham D. Lamb ◽  
Roque El-Hayek ◽  
Noriaki Ikemoto ◽  
D. George Stephenson
Keyword(s):  
Skeletal Muscle ◽  
Direct Action ◽  
Muscle Fibers ◽  
Dihydropyridine Receptor ◽  
Intracellular Loop ◽  
Release Channel ◽  
Voltage Sensors ◽  
Skeletal Muscle Fibers ◽  
Peptide Segments

In skeletal muscle fibers, the intracellular loop between domains II and III of the α1-subunit of the dihydropyridine receptor (DHPR) may directly activate the adjacent Ca2+ release channel in the sarcoplasmic reticulum. We examined the effects of synthetic peptide segments of this loop on Ca2+ release in mechanically skinned skeletal muscle fibers with functional excitation-contraction coupling. In rat fibers at physiological Mg2+ concentration ([Mg2+]; 1 mM), a 20-residue skeletal muscle DHPR peptide [AS(20); Thr671-Leu690; 30 μM], shown previously to induce Ca2+ release in a triad preparation, caused only small spontaneous force responses in ∼40% of fibers, although it potentiated responses to depolarization and caffeine in all fibers. The COOH-terminal half of AS(20)[AS(10)] induced much larger spontaneous responses but also caused substantial inhibition of Ca2+release to both depolarization and caffeine. Both peptides induced or potentiated Ca2+ release even when the voltage sensors were inactivated, indicating direct action on the Ca2+ release channels. The corresponding 20-residue cardiac DHPR peptide [AC(20); Thr793-Ala812] was ineffective, but its COOH-terminal half [AC(10)] had effects similar to AS(20). In the presence of lower [Mg2+] (0.2 mM), exposure to either AS(20) or AC(10) (30 μM) induced substantial Ca2+ release. Peptide CS (100 μM), a loop segment reported to inhibit Ca2+ release in triads, caused partial inhibition of depolarization-induced Ca2+ release. In toad fibers, each of the A peptides had effects similar to or greater than those in rat fibers. These findings suggest that the A and C regions of the skeletal DHPR II-III loop may have important roles in vivo.

scholarly journals Chloroform extract of hog barn dust modulates skeletal muscle ryanodine receptor calcium-release channel (RyR1)

2010 ◽  
Vol 109 (3) ◽  
pp. 830-839 ◽  
Author(s):  
Chengju Tian ◽  
Chun Hong Shao ◽  
Danielle S. Fenster ◽  
Mark Mixan ◽  
Debra J. Romberger ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Muscle Weakness ◽  
Calcium Release ◽  
Single Channel ◽  
Calcium Release Channel ◽  
Open Probability ◽  
Skeletal Muscle Function ◽  
Release Channel ◽  
Skeletal Muscle Weakness

Skeletal muscle weakness is a reported ailment in individuals working in commercial hog confinement facilities. To date, specific mechanisms responsible for this symptom remain undefined. The purpose of this study was to assess whether hog barn dust (HBD) contains components that are capable of binding to and modulating the activity of type 1 ryanodine receptor Ca2+-release channel (RyR1), a key regulator of skeletal muscle function. HBD collected from confinement facilities in Nebraska were extracted with chloroform, filtered, and rotary evaporated to dryness. Residues were resuspended in hexane-chloroform (20:1) and precipitates, referred to as HBDorg, were air-dried and studied further. In competition assays, HBDorg dose-dependently displaced [3H]ryanodine from binding sites on RyR1 with an IC50 of 1.5 ± 0.1 μg/ml ( Ki = 0.4 ± 0.0 μg/ml). In single-channel assays using RyR1 reconstituted into a lipid bilayer, HBDorg exhibited three distinct dose-dependent effects: first it increased the open probability of RyR1 by increasing its gating frequency and dwell time in the open state, then it induced a state of reduced conductance (55% of maximum) that was more likely to occur and persist at positive holding potentials, and finally it irreversibly closed RyR1. In differentiated C2C12 myotubes, addition of HBD triggered a rise in intracellular Ca2+ that was blocked by pretreatment with ryanodine. Since persistent activation and/or closure of RyR1 results in skeletal muscle weakness, these new data suggest that HBD is responsible, at least in part, for the muscle ailment reported by hog confinement workers.

scholarly journals Single channel measurements of the calcium release channel from skeletal muscle sarcoplasmic reticulum. Activation by Ca2+ and ATP and modulation by Mg2+.

1986 ◽  
Vol 88 (5) ◽  
pp. 573-588 ◽  
Author(s):  
J S Smith ◽  
R Coronado ◽  
G Meissner
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Lipid Bilayers ◽  
Calcium Release ◽  
Single Channel ◽  
Ca Channel ◽  
Channel Measurements ◽  
Calcium Release Channel ◽  
Open Probability ◽  
Release Channel

A high-conductance (100 pS in 53 mM trans Ca2+) Ca2+ channel was incorporated from heavy-density skeletal muscle sarcoplasmic reticulum (SR) fractions into planar lipid bilayers of the Mueller-Rudin type. cis Ca2+ in the range of 2-950 microM increased open probability (Po) in single channel records without affecting open event lifetimes. Millimolar ATP was found to be as good as or better than Ca2+ in activation; however, both Ca2+ and ATP were required to fully activate the channel, i.e., to bring Po = 1. Exponential fits to open and closed single channel lifetimes suggested that the channel may exist in many distinct states. Two open and two closed states were identified when the channel was activated by either Ca2+ or ATP alone or by Ca2+ plus nucleotide. Mg2+ was found to permeate the SR Ca channel in a trans-to-cis direction such that iMg2+/iCa2+ = 0.40. cis Mg2+ was inhibitory and in single channel recordings produced an unresolvable flickering of Ca- and nucleotide-activated channels. At nanomolar cis Ca2+, 4 microM Mg2+ completely inhibited nucleotide-activated channels. In the presence of 2 microM cis Ca2+, the nucleotide-activated macroscopic Ba conductance was inhibited by cis Mg2+ with an IC50 equal to 1.5 mM.

scholarly journals Activation and labelling of the purified skeletal muscle ryanodine receptor by an oxidized ATP analogue

1995 ◽  
Vol 308 (1) ◽  
pp. 119-125 ◽  
Author(s):  
M Hohenegger ◽  
A Herrmann-Frank ◽  
M Richter ◽  
F Lehmann-Horn
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Single Channel ◽  
Adenine Nucleotide ◽  
Nucleotide Binding ◽  
Binding Pocket ◽  
Hill Coefficient ◽  
Dependent Manner ◽  
Open Probability ◽  
Release Channel

We have tested the periodate-oxidized ATP analogue 2′,3′-dialdehyde adenosine triphosphate (oATP) as a ligand for the skeletal muscle ryanodine receptor/Ca(2+)-release channel. Ca2+ efflux from passively loaded heavy sarcoplasmic reticulum vesicles of skeletal muscle is biphasic. oATP stimulates the initial phase of Ca2+ release in a concentration-dependent manner (EC50 160 microM), and the efflux proceeds with a half-time in the range 100-200 ms. This oATP-modulated initial rapid Ca2+ release was specifically inhibited by millimolar concentrations of Mg2+ and micromolar concentrations of Ruthenium Red, indicating that the effect of oATP was mediated via the ryanodine receptor. The purified Ca(2+)-release channel was incorporated into planar lipid bilayers, and single-channel recordings were carried out to verify a direct interaction of oATP with the ryanodine receptor. Addition of oATP to the cytoplasmic side activated the channel with an EC50 of 76 microM, which is roughly 30-fold higher than the apparent affinity of ATP. The oATP-induced increase in the open probability of the ryanodine receptor displays a steep concentration-response curve with a Hill coefficient of approximately 2, which suggests a co-operativity of the ATP binding sites in the tetrameric protein. oATP binds to the ryanodine receptor in a quasi-irreversible manner via Schiff base formation between the aldehyde groups of oATP and amino groups in the nucleotide binding pocket. This allows for the covalent specific incorporation of [alpha-32P]oATP by borhydride reduction. A typical adenine nucleotide binding site cannot be identified in the primary sequence of the ryanodine receptor. Our results demonstrate that oATP can be used to probe the structure and function of the nucleotide binding pocket of the ryanodine receptor and presumably of other ATP-regulated ion channels.

scholarly journals A new scorpion toxin (BmK-PL) stimulates Ca2+-release channel activity of the skeletal-muscle ryanodine receptor by an indirect mechanism

1999 ◽  
Vol 339 (2) ◽  
pp. 343-350 ◽  
Author(s):  
Akihiko KUNIYASU ◽  
Seiko KAWANO ◽  
Yoshiyuki HIRAYAMA ◽  
Yong-Hua JI ◽  
Ke XU ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Protein Molecule ◽  
Binding Activity ◽  
Scorpion Toxin ◽  
Channel Activity ◽  
Release Channel ◽  
Indirect Mechanism ◽  
High Concentrations

A peptide toxin isolated from the Chinese scorpion Buthus martensiKarsch (BmK-PL) stimulated Ca2+-release channel activity in both triad membranes and reconstituted ryanodine receptors partially purified from rabbit skeletal muscle. In [3H]ryanodine binding experiments, the toxin increased the affinity of ryanodine for the receptor, from a Kd of 24.3 nM to 2.9 nM, which is an enhancement similar to that seen with known receptor activators, such as ATP and high concentrations of KCl. In contrast, toxin enhancement was not observed with purified receptors, although intrinsic binding activity and stimulation by the conventional receptor activators were retained. In single channel recordings of Ca2+-release activity, the toxin increased the open channel probability (Po) from 0.019 to 0.043 (226% of control) in triad preparations. Further toxin enhancement of Po from 0.07 to 0.37 (529% of control) was observed using partially-purified receptors in the presence of ATP. When purified receptors were assayed in the presence of ATP, however, they showed a high value of Po (0.33) and no further increase was observed following application of the toxin. Results derived from two different experimental methods consistently suggest that a molecule(s) required for toxin-induced enhancement is absent from the purified receptor preparation. Western blot analysis of receptors prepared using three different protocols showed that triadin was missing from the purified receptor preparation. The scorpion toxin minimally enhanced Ca2+-release channel activity of cardiac preparations. From these results, we conclude that the toxin preferentially increases the activity of skeletal-muscle ryanodine receptors by an indirect mechanism, possibly binding to associated protein molecule(s). Triadin is a strong candidate for such a molecule.

Two Types of ACh Receptors Contribute to Fast Channel Gating on Mouse Skeletal Muscle

1997 ◽  
Vol 78 (6) ◽  
pp. 2966-2974 ◽  
Author(s):  
Dawn Shepherd ◽  
Paul Brehm
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Channel Gating ◽  
Receptor Type ◽  
Open Probability ◽  
Mouse Skeletal Muscle ◽  
Single Channel Recordings ◽  
Open Time ◽  
Channel Open Time ◽  
Ach Receptors

Shepherd, Dawn and Paul Brehm. Two types of ACh receptors contribute to fast channel gating on mouse skeletal muscle. J. Neurophysiol. 78: 2966–2974, 1997. Single-channel recordings from mouse C2 myotubes indicate that maturation of skeletal muscle is accompanied by the appearance of two types of fast acetylcholine (ACh) receptor channels that are each functionally distinct from the embryonic receptor type present at early stages of differentiation. The embryonic receptor type has a low conductance (45 pS) and long channel open time, rendering slowly decaying synaptic currents. One fast channel type that appears during muscle maturation is distinguished from the embryonic receptor type on the basis of both higher conductance (65 pS) and shorter open time. However, single-channel recordings from differentiated mouse skeletal muscle cell line (C2) point to the existence of a second fast receptor type, which has a conductance similar to the embryonic receptor type (45 pS), yet significantly reduced mean channel open time. Analyses of individual channel function at high ACh concentrations directly demonstrate the coexistence of two kinetically distinct types of 45 pS ACh receptors. Openings by fast type and slow embryonic type of 45 pS receptors occurred in bursts, allowing distinction on the basis of both mean open time and open probability for individual receptors. The embryonic type of 45 pS receptor has an open time approximately twofold longer than the fast-receptor counterpart. Additional differences were reflected in the open probability distributions for fast and slow 45 pS receptor types. Both types of 45 pS receptor were kinetically distinguishable from the 65 pS receptor. We found no support for the idea that the slow and fast 45 pS receptor types result from the interconversion of dual gating modes involving the same receptor protein. Our results are consistent with the idea that the acquisition of fast synaptic current decay, required at mature neuromuscular synapses, is the result of the up-regulation of two distinct fast types of nicotinic ACh receptors during skeletal muscle development.

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