scholarly journals Calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum in skeletal muscle fibers.

1991 ◽  
Vol 97 (3) ◽  
pp. 437-471 ◽  
Author(s):  
B J Simon ◽  
M G Klein ◽  
M F Schneider
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Calcium Transients ◽  
Calcium Dependence ◽  
Fura 2 ◽  
Test Pulse ◽  
Calcium Dependent

The steady-state calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum was studied in voltage-clamped, cut segments of frog skeletal muscle fibers containing two calcium indicators, fura-2 and anti-pyrylazo III (AP III). Fura-2 fluorescence was used to monitor resting calcium and relatively small calcium transients during small depolarizations. AP III absorbance signals were used to monitor larger calcium transients during larger depolarizations. The rate of release (Rrel) of calcium from the sarcoplasmic reticulum was calculated from the calcium transients. The equilibrium calcium dependence of inactivation of calcium release was determined using 200-ms prepulses of various amplitudes to elevate [Ca2+] to various steady levels. Each prepulse was followed by a constant test pulse. The suppression of peak Rrel during the test pulse provided a measure of the extent of inactivation of release at the end of the prepulse. The [Ca2+] dependence of inactivation indicated that binding of more than one calcium ion was required to inactivate each release channel. Half-maximal inactivation was produced at a [Ca2+] of approximately 0.3 microM. Variation of the prepulse duration and amplitude showed that the suppression of peak release was consistent with calcium-dependent inactivation of calcium release but not with calcium depletion. The same calcium dependence of inactivation was obtained using different amplitude test pulses to determine the degree of inactivation. Prepulses that produced near maximal inactivation of release during the following test pulse produced no suppression of intramembrane charge movement during the test pulse, indicating that inactivation occurred at a step beyond the voltage sensor for calcium release. Three alternative set of properties that were assumed for the rapidly equilibrating calcium-binding sites intrinsic to the fibers gave somewhat different Rrel records, but gave very similar calcium dependence of inactivation. Thus, equilibrium inactivation of calcium release appears to be produced by rather modest increases in [Ca2+] above the resting level and in a steeply calcium-dependent manner. However, the inactivation develops relatively slowly even during marked elevation of [Ca2+], indicating that a calcium-independent transition appears to occur after the initial calcium-binding step.

Calsequestrin targeting to sarcoplasmic reticulum of skeletal muscle fibers

2006 ◽  
Vol 291 (2) ◽  
pp. C245-C253 ◽  
Author(s):  
Alessandra Nori ◽  
Giorgia Valle ◽  
Elena Bortoloso ◽  
Federica Turcato ◽  
Pompeo Volpe
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Structural Information ◽  
Muscle Fibers ◽  
Physiological Role ◽  
Homogeneous Distribution ◽  
Skeletal Muscle Fibers ◽  
Domain Iii

Calsequestrin (CS) is the low-affinity, high-capacity calcium binding protein segregated to the lumen of terminal cisternae (TC) of the sarcoplasmic reticulum (SR). The physiological role of CS in controlling calcium release from the SR depends on both its intrinsic properties and its localization. The mechanisms of CS targeting were investigated in skeletal muscle fibers and C2C12 myotubes, a model of SR differentiation, with four deletion mutants of epitope (hemagglutinin, HA)-tagged CS: CS-HAΔ24NH2, CS-HAΔ2D, CS-HAΔ3D, and CS-HAΔHT, a double mutant of the NH2 terminus and domain III. As judged by immunofluorescence of transfected skeletal muscle fibers, only the double CS-HA mutant showed a homogeneous distribution at the sarcomeric I band, i.e., it did not segregate to TC. As shown by subfractionation of microsomes derived from transfected skeletal muscles, CS-HAΔHT was largely associated to longitudinal SR whereas CS-HA was concentrated in TC. In C2C12 myotubes, as judged by immunofluorescence, not only CS-HAΔHT but also CS-HAΔ3D and CS-HAΔ2D were not sorted to developing SR. Condensation competence, a property referable to CS oligomerization, was monitored for the several CS-HA mutants in C2C12 myoblasts, and only CS-HAΔ3D was found able to condense. Together, the results indicate that 1) there are at least two targeting sequences at the NH2 terminus and domain III of CS, 2) SR-specific target and structural information is contained in these sequences, 3) heterologous interactions with junctional SR proteins are relevant for segregation, 4) homologous CS-CS interactions are involved in the overall targeting process, and 5) different targeting mechanisms prevail depending on the stage of SR differentiation.

scholarly journals Effects of low myoplasmic Mg2+ on calcium binding by parvalbumin and calcium uptake by the sarcoplasmic reticulum in frog skeletal muscle.

1992 ◽  
Vol 100 (1) ◽  
pp. 115-135 ◽  
Author(s):  
V Jacquemond ◽  
M F Schneider
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Muscle Fiber ◽  
Calcium Binding ◽  
Calcium Uptake ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Frog Skeletal Muscle ◽  
Fura 2 ◽  
Calcium Removal

The effects of low intracellular free Mg2+ on the myoplasmic calcium removal properties of skeletal muscle were studied in voltage-clamped frog skeletal muscle fibers by analyzing the changes in intracellular calcium and magnesium due to membrane depolarization under various conditions of internal free [Mg2+]. Batches of fibers were internally equilibrated with cut end solutions containing two calcium indicators, antipyrylazo III (AP III) and fura-2, and different concentrations of free Mg2+ (25 microM-1 mM) obtained by adding appropriate total amounts of ATP and magnesium to the solutions. Changes in AP III absorbance were used to monitor [Ca2+] and [Mg2+] transients, whereas fura-2 fluorescence was mostly used to monitor resting [Ca2+]. Shortly after applying an internal solution containing less than 60 microM free Mg2+ to the cut ends of depolarized fibers most of the fibers exhibited spontaneous repetitive movements, suggesting that free internal Mg2+ might affect the activity of the sarcoplasmic reticulum (SR) calcium channels at rest. The spontaneous contractions generally subsided. In polarized fibers the maximal amplitude of the calcium transient elicited by a depolarizing pulse was about the same whatever the internal [Mg2+], but its decay after the end of the pulse slower in low [Mg2+]. In low [Mg2+] (less than 0.14 mM), the mean rate constant of decay obtained from fitting a single exponential plus a constant to the decay of the calcium transients was approximately 30% of its value in the control fibers (1 mM internal [Mg2+]). A model characterizing the main calcium removal properties of a frog skeletal muscle fiber, including the SR pump and the Ca-Mg sites on parvalbumin, was fitted to the decay of the calcium transients. Results of the fits show that in low internal [Mg2+] the slowing of the decay of the calcium transient can be well predicted by both a decreased rate of SR calcium uptake and an expected decreased resting magnesium occupancy of parvalbumin leading to a reduced contribution of parvalbumin to the overall rate of calcium removal. These results are thus consistent with the known properties of parvalbumin as a Ca-Mg buffer and furthermore suggest that in an intact portion of a muscle fiber, the activity of the SR calcium pump can be affected by the level of free Mg2+.

scholarly journals The Effect of Calcium Ionophores on Fragmented Sarcoplasmic Reticulum

1972 ◽  
Vol 60 (6) ◽  
pp. 735-749 ◽  
Author(s):  
Antonio Scarpa ◽  
Judith Baldassare ◽  
Giuseppe Inesi
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Electron Microscopic ◽  
Microscopic Appearance ◽  
Calcium Accumulation ◽  
Calcium Dependent ◽  
Dependent Atpase

X-537 A and A 23187, two antibiotics which form liphophilic complexes with divalent cations, function as ionophores in vesicular fragments of sarcoplasmic reticulum (SR). Addition of either ionophore to SR preloaded with calcium in the presence of adenosine triphosphate (ATP), causes rapid release of calcium. Furthermore, net calcium accumulation by SR is prevented, when the ionophores are added to the reaction mixture before ATP. On the contrary, ATP-independent calcium binding to SR is not inhibited. This effect is specific for the two antibiotics and could not be reproduced, either by inactive derivatives, or by other known ionophores. Neither ionophore produces alterations of the electron microscopic appearance of SR membranes or inhibition of the calcium-dependent ATPase. In fact, the burst of ATP hydrolysis obtained on addition of calcium, is prolonged in the presence of the ionophores. Lanthanum inhibits ATP-independent calcium binding to SR, ATP-dependent calcium accumulation and calcium-dependent ATPase. However, addition of lanthanum to SR preloaded in the presence of ATP, does not cause calcium release. The reported experiments indicated that: (a) ATP-dependent calcium accumulation by SR results in primary formation of calcium ion gradients across the membrane. (b) Most of the accumulated calcium is not available for displacement by lanthanum on the outer surface of the membrane. (c) Calcium ionophores induce rapid equilibration of the gradients, by facilitating cation diffusion across the membrane.

scholarly journals The Influence of Hydrogen Ion Concentration on Calcium Binding and Release by Skeletal Muscle Sarcoplasmic Reticulum

1972 ◽  
Vol 59 (1) ◽  
pp. 22-32 ◽  
Author(s):  
Yoshiaki Nakamaru ◽  
Arnold Schwartz
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Ph Change ◽  
Release Process ◽  
Hydrogen Ion Concentration ◽  
Calcium Loading

Calcium release and binding produced by alterations in pH were investigated in isolated sarcoplasmic reticulum (SR) from skeletal muscle. When the pH was abruptly increased from 6.46 to 7.82, after calcium loading for 30 sec, 80–90 nanomoles (nmole) of calcium/mg protein were released. When the pH was abruptly decreased from 7.56 to 6.46, after calcium loading for 30 sec, 25–30 nmole of calcium/mg protein were rebound. The calcium release process was shown to be a function of pH change: 57 nmole of calcium were released per 1 pH unit change per mg protein. The amount of adenosine triphosphate (ATP) bound to the SR was not altered by the pH changes. The release phenomenon was not due to alteration of ATP concentration by the increased pH. Native actomyosin was combined with SR in order to study the effectiveness of calcium release from the SR by pH change in inducing super-precipitation of actomyosin. It was found that SR, in an amount high enough to inhibit superprecipitation at pH 6.5, did not prevent the process when the pH was suddenly increased to 7.3, indicating that the affinity of SR for calcium depends specifically on pH. These data suggest the possible participation of hydrogen ion concentration in excitation-contraction coupling.

The Modulation of the Calcium Transport by Skeletal Muscle Sarcoplasmic Reticulum in the Hibernating European Hamster

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1109-1126 ◽  
Author(s):  
◽  
Luisa De Martino ◽  
Barbara Soltau ◽  
Wilhelm Hasselbach
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Release ◽  
Ion Homeostasis ◽  
Free Calcium ◽  
Type I ◽  
Calcium Dependent ◽  
Calcium Affinity

Calcium transport of skeletal muscle sarcoplasmic reticulum was comparatively studied in hibernating and summer active European hamsters (Cricetus cricetus L.). Crude homogenates from psoas, soleus and mixed skeletal muscles were used. Protein yield was strongly reduced in the muscle homogenates of hibernating hamsters. The calcium concentration in the muscle of hibernating hamsters was increased to a much higher content than in the serum. In the same animals the maximal rate of calcium uptake and the calcium storing capacity of sarcoplasmic reticulum were augmented by 43% and respectively 17%. Kinetic experiments with various concentrations of free calcium revealed in the hibernating animals higher uptake rates and a lower apparent calcium affinity than in the summer active hamsters. Some shift of calcium uptake rate and calcium affinity similar to that of a fast-twitch muscle was also observed in winter active animals kept at 22 C under natural photoperiod. By contrast, the activity of the calcium dependent ATPase was not increased, suggesting a tighter coupling during hibernation between calcium dependent ATP-hydrolysis and calcium transport. No seasonal difference was observed in the calcium release by KCl-caffeine from calcium loaded vesicles of sarcoplasmic reticulum.Proportion and size of fibre types were studied with cold cross sections from psoas and soleus muscles. An average atrophy of about 25% was found during hibernation in both muscles. Cytochemistry revealed, however, a different reduction of cross area between type-I- and type-11-fibres, which reaches values up to 46% in the type-I I-fast-fibres of the slow soleus muscle. Electron microscopy did not show any definite change in the distribution and amount of sarcoplasmic reticulum.The results suggest that during hibernation a modulation in the properties of calcium transport ATPase of sarcoplasmic reticulum occurs to better support the calcium transport function at low temperatures, which in turn warrants the restoration of ion homeostasis in the course of the arousal.

scholarly journals Inhibitors of Calmodulin-Dependent Phosphorylation Simultaneously Inhibit Calcium Uptake and Calcium-Dependent ATPase Activity in Skeletal Muscle Sarcoplasmic Reticulum and Transiently Induce Calcium Release

1984 ◽  
Vol 39 (11-12) ◽  
pp. 1189-1191 ◽  
Author(s):  
Wilhelm Hasselbach
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Uptake ◽  
Calcium Release ◽  
Atp Hydrolysis ◽  
Calmodulin Antagonists ◽  
Experimental Conditions ◽  
Calcium Dependent ◽  
Inhibiting Effect ◽  
Hydrolysis Of

Keywords Under adequate experimental conditions calmodulin antagonists like compound 48/80 do not dissociate calcium uptake from the calcium -dependent ATP hydrolysis of skeletal muscle sarcoplasmic reticulum membranes but simultaneously inhibit both processes. Apart from the agent’s pump inhibiting effect, they interact with the caffeine sensitive calcium channel in the sarcoplasmic reticulum causing a rapid transient calcium release.

scholarly journals Ca2+ dependence of transverse tubule-mediated calcium release in skinned skeletal muscle fibers.

1986 ◽  
Vol 87 (2) ◽  
pp. 271-288 ◽  
Author(s):  
P Volpe ◽  
E W Stephenson
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Transverse Tubule ◽  
Force Development ◽  
Skeletal Muscle Fibers ◽  
Gramicidin D ◽  
45Ca Efflux ◽  
Stimulation Of

Isometric force and 45Ca efflux from the sarcoplasmic reticulum were measured at 19 degrees C in frog skeletal muscle fibers skinned by microdissection. After Ca2+ loading, application of the ionophores monensin, an Na+(K+)/H+ exchanger, or gramicidin D, an H+ greater than K+ greater than Na+ channel-former, evoked rapid force development and stimulated release of approximately 30% of the accumulated 45Ca within 1 min, whereas CCCP (carbonyl cyanide pyruvate p-trichloromethoxyphenylhydrazone), a protonophore, and valinomycin, a neutral, K+-specific ionophore, did not. When monensin was present in all bathing solutions, i.e., before and during Ca2+ loading, subsequent application failed to elicit force development and to stimulate 45Ca efflux. 5 min pretreatment of the skinned fibers with 50 microM digitoxin, a permeant glycoside that specifically inhibits the Na+,K+ pump, inhibited monensin and gramicidin D stimulation of 45Ca efflux; similar pretreatment with 100 microM ouabain, an impermeant glycoside, was ineffective. Monensin stimulation of 45Ca efflux was abolished by brief pretreatment with 5 mM EGTA, which chelates myofilament-space calcium. These results suggest that: monensin and gramicidin D stimulate Ca2+ release from the sarcoplasmic reticulum that is mediated by depolarization of the transverse tubules, which seal off after sarcolemma removal and form closed compartments; a transverse tubule membrane potential (myofilament space-negative) is maintained and/or established by the operation of the Na+,K+ pump in the transverse tubule membranes and is sensitive to the permeant inhibitor digitoxin; the transverse tubule-mediated stimulation of 45Ca efflux appears to be entirely Ca2+ dependent.

scholarly journals Impaired Sarcoplasmic Reticulum Calcium Release In Skeletal Muscle Fibers From Myotubularin-Deficient Mice

2009 ◽  
Vol 96 (3) ◽  
pp. 10a ◽  
Author(s):  
Norbert Weiss ◽  
Lama Al-Qusairi ◽  
Celine Berbey ◽  
Bruno Allard ◽  
Jean Louis Mandel ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Skeletal Muscle Fibers ◽  
Sarcoplasmic Reticulum Calcium ◽  
Deficient Mice
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