Different interactions of cardiac and skeletal muscle ryanodine receptors with FK-506 binding protein isoforms

1997 ◽  
Vol 272 (5) ◽  
pp. C1726-C1733 ◽  
Author(s):  
S. Barg ◽  
J. A. Copello ◽  
S. Fleischer
Keyword(s):  
Skeletal Muscle ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Protein Isoforms ◽  
Channel Activity ◽  
Functional Interaction ◽  
Fk 506 ◽  
Receptor Isoforms ◽  
Functional Consequences

In the present study, we compare functional consequences of dissociation and reconstitution of binding proteins FKBP12 and FKBP12.6 with ryanodine receptors from cardiac (RyR2) and skeletal muscle (RyR1). The skeletal muscle RyR1 channel became activated on removal of endogenously bound FKBP12, consistent with previous reports. Both FKBP12 and FKBP12.6 rebind to FKBP-depleted RyR1 and restore its quiescent channel behavior by altering ligand sensitivity, as studied by single-channel recordings in planar lipid bilayers, and macroscopic behavior of the channels (ryanodine binding and net energized Ca2- uptake). By contrast, removal of FKBP12.6 from the cardiac RyR2 did not modulate the function of the channel using the same types of assays as for RyR1. FKBP12 or FKBP12.6 had no effect on channel activity of FKBP12.6-depleted cardiac RyR2, although FKBP12.6 rebinds. Our studies reveal important differences between the two ryanodine receptor isoforms with respect to their functional interaction with FKBP12 and FKBP12.6.

scholarly journals Imperatoxin A Induces Subconductance States in Ca2+ Release Channels (Ryanodine Receptors) of Cardiac and Skeletal Muscle

1998 ◽  
Vol 111 (5) ◽  
pp. 679-690 ◽  
Author(s):  
Ashutosh Tripathy ◽  
Wolfgang Resch ◽  
Le Xu ◽  
Hector H. Valdivia ◽  
Gerhard Meissner
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Binding Site ◽  
Lipid Bilayers ◽  
Rate Constant ◽  
Single Channel ◽  
Voltage Drop ◽  
Ryanodine Receptors ◽  
Subconductance States ◽  
Single Channel Currents

Single-channel and [3H]ryanodine binding experiments were carried out to examine the effects of imperatoxin activator (IpTxa), a 33 amino acid peptide isolated from the venom of the African scorpion Pandinus imperator, on rabbit skeletal and canine cardiac muscle Ca2+ release channels (CRCs). Single channel currents from purified CRCs incorporated into planar lipid bilayers were recorded in 250 mM KCl media. Addition of IpTxa in nanomolar concentration to the cytosolic (cis) side, but not to the lumenal (trans) side, induced substates in both ryanodine receptor isoforms. The substates displayed a slightly rectifying current–voltage relationship. The chord conductance at −40 mV was ∼43% of the full conductance, whereas it was ∼28% at a holding potential of +40 mV. The substate formation by IpTxa was voltage and concentration dependent. Analysis of voltage and concentration dependence and kinetics of substate formation suggested that IpTxa reversibly binds to the CRC at a single site in the voltage drop across the channel. The rate constant for IpTxa binding to the skeletal muscle CRC increased e-fold per +53 mV and the rate constant of dissociation decreased e-fold per +25 mV applied holding potential. The effective valence of the reaction leading to the substate was ∼1.5. The IpTxa binding site was calculated to be located at ∼23% of the voltage drop from the cytosolic side. IpTxa induced substates in the ryanodine-modified skeletal CRC and increased or reduced [3H]ryanodine binding to sarcoplasmic reticulum vesicles depending on the level of channel activation. These results suggest that IpTxa induces subconductance states in skeletal and cardiac muscle Ca2+ release channels by binding to a single, cytosolically accessible site different from the ryanodine binding site.

A calcium-activated chloride channel in sarcoplasmic reticulum vesicles from rabbit skeletal muscle

1996 ◽  
Vol 270 (6) ◽  
pp. C1675-C1686 ◽  
Author(s):  
J. I. Kourie ◽  
D. R. Laver ◽  
G. P. Ahern ◽  
A. F. Dulhunty
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Lipid Bilayers ◽  
Chloride Channel ◽  
Single Channel ◽  
Single Channels ◽  
Channel Activity ◽  
Open Probability ◽  
Single Channel Activity ◽  
Maximum Conductance

A Ca(2+)-activated Cl- channel is described in sarcoplasmic reticulum (SR) enriched vesicles of skeletal muscle incorporated into lipid bilayers. Small chloride (SCl) channels (n = 20) were rapidly and reversibly activated when cis- (cytoplasmic) [Ca2+] was increased above 10(-7) M, with trans-(luminal) [Ca2+] at either 10(-3) or 10(-7) M. The open probability of single channels increased from zero when cis-[Ca2+] was 10(-7) M to 0.61 +/- 0.12 when [Ca2+] was 10(-4) M. High- and low-conductance levels in single-channel activity were activated at different cis-[Ca2+]. Channel openings to the maximum conductance, 65-75 pS (250/50 mM Cl-, cis/ trans), were active when cis-[Ca2+] was increased above 5 x 10(-6) M. In contrast to the maximum conductance, channel openings to submaximal levels between 5 and 40 pS were activated at a lower cis-[Ca2+] and dominated channel activity between 5 x 10(-7) and 5 x 10(-6) M. Activation of SCl channels was Ca2+ specific and not reproduced by cytoplasmic Mg2+ concentrations of 10(-3) M. We suggest that the SCl channel arises in the SR membrane. The Ca2+ dependence of this channel implies that it is active at [Ca2+] achieved during muscle contraction.

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.

scholarly journals Apparent lack of physical or functional interaction between CaV1.1 and its distal C terminus

2015 ◽  
Vol 145 (4) ◽  
pp. 303-314 ◽  
Author(s):  
Joshua D. Ohrtman ◽  
Christin F. Romberg ◽  
Ong Moua ◽  
Roger A. Bannister ◽  
S. Rock Levinson ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Channel Activity ◽  
Functional Interaction ◽  
Adult Skeletal Muscle ◽  
Apparent Lack ◽  
Terminal Domain ◽  
C Terminus ◽  
Decay Times

CaV1.1 acts as both the voltage sensor that triggers excitation–contraction coupling in skeletal muscle and as an L-type Ca2+ channel. It has been proposed that, after its posttranslational cleavage, the distal C terminus of CaV1.1 remains noncovalently associated with proximal CaV1.1, and that tethering of protein kinase A to the distal C terminus is required for depolarization-induced potentiation of L-type Ca2+ current in skeletal muscle. Here, we report that association of the distal C terminus with proximal CaV1.1 cannot be detected by either immunoprecipitation of mouse skeletal muscle or by colocalized fluorescence after expression in adult skeletal muscle fibers of a CaV1.1 construct labeled with yellow fluorescent protein (YFP) and cyan fluorescent protein on the N and C termini, respectively. We found that L-type Ca2+ channel activity was similar after expression of constructs that either did (YFP-CaV1.11860) or did not (YFP-CaV1.11666) contain coding sequence for the distal C-terminal domain in dysgenic myotubes null for endogenous CaV1.1. Furthermore, in response to strong (up to 90 mV) or long-lasting prepulses (up to 200 ms), tail current amplitudes and decay times were equally increased in dysgenic myotubes expressing either YFP-CaV1.11860 or YFP-CaV1.11666, suggesting that the distal C-terminal domain was not required for depolarization-induced potentiation. Thus, our experiments do not support the existence of either biochemical or functional interactions between proximal CaV1.1 and the distal C terminus.

scholarly journals Caffeine-induced inhibition of inositol(1,4,5)-trisphosphate-gated calcium channels from cerebellum.

1994 ◽  
Vol 5 (1) ◽  
pp. 97-103 ◽  
Author(s):  
I Bezprozvanny ◽  
S Bezprozvannaya ◽  
B E Ehrlich
Keyword(s):  
Lipid Bilayers ◽  
Inhibitory Action ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Single Channels ◽  
Ca Channels ◽  
Open Time ◽  
Inositol 1,4,5 Trisphosphate ◽  
Insp3 Receptors ◽  
Intracellular Ca

Effects of the xanthine drug caffeine on inositol (1,4,5)-trisphosphate (InsP3)-gated calcium (Ca) channels from canine cerebellum were studied using single channels incorporated into planar lipid bilayers. Caffeine, used widely as an agonist of ryanodine receptors, inhibited the activity of InsP3-gated Ca channels in a noncooperative fashion with half-inhibition at 1.64 mM caffeine. The frequency of channel openings was decreased more than threefold after addition of 5 mM caffeine; there was only a small effect on mean open time of the channels, and the single channel conductance was unchanged. Increased InsP3 concentration overcame the inhibitory action of caffeine, but caffeine did not reduce specific [3H]InsP3 binding to the receptor. The inhibitory action of caffeine on InsP3 receptors suggests that the action of caffeine on the intracellular Ca pool must be interpreted with caution when both ryanodine receptors and InsP3 receptors are present in the cell.

Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle

2000 ◽  
Vol 279 (5) ◽  
pp. R1889-R1898 ◽  
Author(s):  
Jeffery Morrissette ◽  
Le Xu ◽  
Alexandra Nelson ◽  
Gerhard Meissner ◽  
Barbara A. Block
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Fiber Type ◽  
Ryanodine Receptors ◽  
Open Probability ◽  
Dependent Inhibition ◽  
Single Channel Activity ◽  
Intracellular Ca ◽  
Slow Twitch ◽  
Fast Twitch

Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type–specific manner in fish skeletal muscle (11). In this study, we compare [3H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [3H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (Po) of RyR1-slow was threefold less than the maximum Po of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest Po of all the RyR channels and displayed less inhibition at millimolar Ca2+. The addition of 5 mM Mg-ATP or 2.5 mM β,γ-methyleneadenosine 5′-triphosphate (AMP-PCP) to the channels increased the Po and [3H]ryanodine binding of both RyR1s but also caused a shift in the Ca2+ dependency curve of RyR1-slow such that Ca2+-dependent inactivation was attenuated. [3H]ryanodine binding data also showed that Mg2+-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca2+ is regulated in these muscle types.

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.

Calcium-dependent halothane activation of sarcoplasmic reticulum calcium channels from frog skeletal muscle

1994 ◽  
Vol 266 (2) ◽  
pp. C391-C396 ◽  
Author(s):  
R. Bull ◽  
J. J. Marengo
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Channels ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Free Calcium ◽  
Frog Skeletal Muscle ◽  
Time Constants ◽  
Calcium Dependent ◽  
Open Time

The effect of halothane on calcium channels present in sarcoplasmic reticulum membranes isolated from frog skeletal muscle was studied at the single channel level after fusing the isolated vesicles into planar lipid bilayers. Addition of 91 microM halothane to the cytosolic compartment containing 1 microM free calcium activated the channel by increasing fractional open time from 0.11 to 0.59, without changing the channel conductance. The activation of the channels by halothane was calcium dependent. At resting calcium concentrations in the cytosolic compartment, halothane failed to activate the channel, whereas maximal activation was found at 10 microM calcium. The free energy of halothane binding to the channel decreased from -5.8 kcal/mol at 1 microM calcium to -6.6 kcal/mol at 10 microM calcium. Halothane increased the open time constants and decreased the closed time constants, indicating that it binds to both the open and the closed configurations of the channel.

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