Imperatoxin A Enhances Ca2+ Release in Developing Skeletal Muscle Containing Ryanodine Receptor Type 3

Nabhani, T.; Zhu, Xiaojuan; Simeoni, Ilenia; Sorrentino, Vincenzo; Valdivia, Héctor H.; Garcı́a, Jesús

doi:10.1016/s0006-3495(02)75487-8

Cited by 22 publications

(15 citation statements)

References 41 publications

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“…Primary cultures were prepared from the skeletal muscle of neonatal mice (postnatal day 0) of the stock CACNA1SxNIHS-BCfBR (39,47). Myotubes from wild type (mdg Ϫ/Ϫ ) or heterozygotes (mdg ϩ/Ϫ ) were undistinguishable.…”

Section: Methodsmentioning

confidence: 99%

A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle

Zhou¹,

Yi²,

Royer³

et al. 2006

American Journal of Physiology-Cell Physiology

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To activate skeletal muscle contraction, action potentials must be sensed by dihydropyridine receptors (DHPRs) in the T tubule, which signal the Ca(2+) release channels or ryanodine receptors (RyRs) in the sarcoplasmic reticulum (SR) to open. We demonstrate here an inhibitory effect of the T tubule on the production of sparks of Ca(2+) release. Murine primary cultures were confocally imaged for Ca(2+) detection and T tubule visualization. After 72 h of differentiation, T tubules extended from the periphery for less than one-third of the myotube radius. Spontaneous Ca(2+) sparks were found away from the region of cells where tubules were found. Immunostaining showed RyR1 and RyR3 isoforms in all areas, implying inhibition of both isoforms by a T tubule component. To test for a role of DHPRs in this inhibition, we imaged myotubes from dysgenic mice (mdg) that lack DHPRs. These exhibited T tubule development similar to that of normal myotubes, but produced few sparks, even in regions where tubules were absent. To increase spark frequency, a high-Ca(2+) saline with 1 mM caffeine was used. Wild-type cells in this saline plus 50 microM nifedipine retained the topographic suppression pattern of sparks, but dysgenic cells in high-Ca(2+) saline did not. Shifted excitation and emission ratios of indo-1 in the cytosol or mag-indo-1 in the SR were used to image [Ca(2+)] in these compartments. Under the conditions of interest, wild-type and mdg cells had similar levels of free [Ca(2+)] in cytosol and SR. These data suggest that DHPRs play a critical role in reducing the rate of spontaneous opening of Ca(2+) release channels and/or their susceptibility to Ca(2+)-induced activation, thereby suppressing the production of Ca(2+) sparks.

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Section: Methodsmentioning

confidence: 99%

A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle

Zhou¹,

Yi²,

Royer³

et al. 2006

American Journal of Physiology-Cell Physiology

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“…Nanomolar concentrations of IpTxa increase the binding of [ 3 H]ryanodine and induce a fast release of calcium from sarcoplasmic reticulum vesicles. More recent studies show that IpTxa prolongs the lifetime of the Ca 2+ sparks in frog skeletal muscle (Shtifman et al, 2000, Gonzalez et al, 2000) and significantly increases the amplitude and rate of Ca 2+ release in developing skeletal muscle (Nabhani et al, 2002). In single channel recordings, IpTxa stabilizes prolonged subconductance states in RyRs of skeletal and cardiac muscle, having 43 and 28% of the channel’s conductance at the holding potentials of -40 and +40 mV, respectively (Trypathy et al, 1998).…”

Section: Ca++release-channel Specific Peptides (Calcins)mentioning

confidence: 99%

Scorpion venom components that affect ion-channels function

Quintero-Hernández

Jiménez-Vargas

Gurrola

et al. 2013

Toxicon

234

168

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SUMMARY The number and types of venom components that affect ion-channel function are reviewed. These are the most important venom components responsible for human intoxication, deserving medical attention, often requiring the use of specific anti-venoms. Special emphasis is given to peptides that recognize Na+-, K+- and Ca++-channels of excitable cells. Knowledge generated by direct isolation of peptides from venom and components deduced from cloned genes, whose amino acid sequences are deposited into databanks are now adays in the order of 1.5 thousands, out of an estimate biodiversity closed to 300,000. Here the diversity of components is briefly reviewed with mention to specific references. Structural characteristic are discussed with examples taken from published work. The principal mechanisms of action of the three different types of peptides are also reviewed. Na+-channel specific venom components usually are modifier of the open and closing kinetic mechanisms of the ion-channels, whereas peptides affecting K+-channels are normally pore blocking agents. The Ryanodine Ca++-channel specific peptides are known for causing sub-conducting stages of the channels conductance and some were shown to be able to internalize penetrating inside the muscle cells.

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“…17 Only bilayers that contained a single channel were used. Channel activity was always tested for sensitivity to EGTA, which was added in the cis chamber at the end of each experiment.…”

Section: Single-channel Recordingsmentioning

confidence: 99%

Mineralocorticoid Modulation of Cardiac Ryanodine Receptor Activity Is Associated With Downregulation of FK506-Binding Proteins

et al. 2009

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Background-The mineralocorticoid pathway is involved in cardiac arrhythmias associated with heart failure through mechanisms that are incompletely understood. Defective regulation of the cardiac ryanodine receptor (RyR) is an important cause of the initiation of arrhythmias. Here, we examined whether the aldosterone pathway might modulate RyR function. Methods and Results-Using the whole-cell patch clamp method, we observed an increase in the occurrence of delayed afterdepolarizations during action potential recordings in isolated adult rat ventricular myocytes exposed for 48 hours to aldosterone 100 nmol/L, in freshly isolated myocytes from transgenic mice with human mineralocorticoid receptor expression in the heart, and in wild-type littermates treated with aldosterone. Sarcoplasmic reticulum Ca 2ϩ load and RyR expression were not altered; however, RyR activity, visualized in situ by confocal microscopy, was increased in all cells, as evidenced by an increased occurrence and redistribution to long-lasting and broader populations of spontaneous Ca

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Imperatoxin A Enhances Ca2+ Release in Developing Skeletal Muscle Containing Ryanodine Receptor Type 3

Cited by 22 publications

References 41 publications

A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle

A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle

Scorpion venom components that affect ion-channels function

Mineralocorticoid Modulation of Cardiac Ryanodine Receptor Activity Is Associated With Downregulation of FK506-Binding Proteins

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Imperatoxin A Enhances Ca2+ Release in Developing Skeletal Muscle Containing Ryanodine Receptor Type 3

Cited by 22 publications

References 41 publications

A probable role of dihydropyridine receptors in repression of Ca2+ sparks demonstrated in cultured mammalian muscle

A probable role of dihydropyridine receptors in repression of Ca2+ sparks demonstrated in cultured mammalian muscle

Scorpion venom components that affect ion-channels function

Mineralocorticoid Modulation of Cardiac Ryanodine Receptor Activity Is Associated With Downregulation of FK506-Binding Proteins

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A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle

A probable role of dihydropyridine receptors in repression of Ca²⁺ sparks demonstrated in cultured mammalian muscle