Charge movement and calcium currents in skeletal muscle fibers are enhanced by GTP?S

Garcı́a, Jesús; Gamboa-Aldeco, R.; Stefani, Enrico

doi:10.1007/bf00370779

Cited by 34 publications

(17 citation statements)

References 20 publications

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“…A control peptide in which the putative amphipathic helix was disrupted by replacing two isoleucine residues with proline had no effect on voltage-dependent channel potentiation. Stimulation of PKA is widely reported to increase skeletal muscle Ca2+ channel activity (32)(33)(34)(35)(36)(37)(38). Surprisingly, neither Ht 31 peptide alone nor Ht 31 peptide with PKA catalytic subunit was found to alter basal channel activity or its voltage dependence.…”

Section: Discussionmentioning

confidence: 99%

Voltage-dependent potentiation of L-type Ca2+ channels in skeletal muscle cells requires anchored cAMP-dependent protein kinase.

Johnson

Scheuer

Catterall

1994

Proc. Natl. Acad. Sci. U.S.A.

177

114

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Skeletal muscle L-type Ca2+ channels in the transverse tubule membrane play critical roles in initiating contraction and in regulating Ca2+ entry (1). A voltage-driven conformational change in the al subunit ofthis Ca2+ channel is thought to trigger the release ofCa2+ from the sarcoplasmic reticulum (2, 3) via protein-protein interactions at the transverse tubule-sarcoplasmic reticulum junction (4-6). The resulting Ca2+ release through the sarcoplasmic reticulum Ca2+ channel initiates contraction (7).The Ca2+ conductance ofthe skeletal muscle Ca2+ channel activates slowly, and only a small fraction of the channels open simultaneously during a single depolarizing stimulus (8).Trains of prepulses to positive membrane potentials that mimic action potentials greatly increase Ca2+ current in response to a subsequent depolarization (9). This Ca2+ channel potentiation is due to rapid phosphorylation by cAMPdependent protein kinase (PKA) at positive membrane potentials and results in a negative shift in the voltage dependence of channel activation and slowing of channel deactivation. Potentiation is reversed within seconds at repolarized membrane potentials by the action of phosphoprotein phosphatases. The force of vertebrate skeletal muscle contraction is substantially increased in response to highfrequency stimulation (10), and this effect is dependent upon extracellular Ca2+ and on the ion-conductance activity of L-type Ca2+ channels (11-13). We have hypothesized that increased contractile force may result from the increased Ca2+ entry through L-type Ca2+ channels whose activity is potentiated by voltage-dependent phosphorylation during and following depolarization (9). This increased Ca2+ entry would increase the store of Ca2+ for release from the sarcoplasmic reticulum during subsequent action potentials. Similar L-type Ca2+ channel potentiation by depolarizing prepulses is observed in cardiac myocytes (14-18) and chromaffin cells (19) and also involves voltage-dependent protein phosphorylation (19,20).A surprising feature of skeletal muscle Ca2+ channel potentiation by voltage-dependent PKA phosphorylation is its rapid response time; 200-Hz trains of positive prepulses as short as 3 msec are effective in potentiating Ca2+ channel activity (9). Many PKA-mediated events occur on a time scale of seconds because of concentration and diffusion limits. PKA is a soluble protein consisting of a central dimer ofregulatory subunits with two associated catalytic subunits. Binding of cAMP to the regulatory subunits reversibly releases active catalytic subunits (21,22). The RII regulatory subunit of PKA also binds to PKA-anchoring proteins (AKAPs) through a conserved binding domain (23), which can be disrupted by a 24-amino acid region from a human thyroid AKAP, Ht 31. Ht 31 peptide prevents RII-AKAP binding in most tissues and disrupts phosphorylation required for the basal activity of the a-amino-3-hydroxy-5-methyl4 isoxazolepropionic acid (AMPA)/kainate receptors in hippocampal neurons (24). This interaction occurs ...

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Section: Discussionmentioning

confidence: 99%

Voltage-dependent potentiation of L-type Ca2+ channels in skeletal muscle cells requires anchored cAMP-dependent protein kinase.

Johnson

Scheuer

Catterall

1994

Proc. Natl. Acad. Sci. U.S.A.

177

114

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“…In other studies on skinned fibers, however, GTP),S did not potentiate depolarization-induced release (85). In voltage-clamped cut fibers, GTP),S was reported to increase charge movement (49,101) and calcium current (49), but in other studies, it was reported to have no effect on charge movement (85). G proteins activate L-type (DHPR) calcium channels in other preparations via DHPR phosphorylation by cAMP-dependent protein kinase (57, 78), and via direct interaction with the channel (73, 136).…”

Section: Magnesium Ionsmentioning

confidence: 93%

Control of Calcium Release in Functioning Skeletal Muscle Fibers

Schneider

1994

Annu. Rev. Physiol.

292

173

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“…Indeed, CGRP has been reported to phosphorylate DHPRs in intact muscle cells, most likely via PKA [115]. First, DHPRs phosphorylation by PKA up-regulates the L-type Ca 2+ current, but does not affect the corresponding charge movement [116], which is actually the trigger for VGCR. However, the following evidence argues against this possibility.…”

Section: Potential Mechanisms Underlying Cgrp Effects On Ec Couplingmentioning

confidence: 99%

CGRP, a Vasodilator Neuropeptide that Stimulates Neuromuscular Transmission and EC Coupling

Vega¹,

Ávila

2010

CVP

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Calcitonin gene related peptide (CGRP) is a vasodilator; its plasma levels are altered in several human diseases, including migraine, hypertension and diabetes. CGRP is locally released by motor neurons, and is overexpressed in response to surgical or pharmacological blockage of neuromuscular transmission. Additionally to a brief discussion with regard to the clinical relevance of CGRP, this review focuses on the effects of CGRP on skeletal muscle excitation-contraction (EC) coupling, as well as the corresponding pathophysiological consequences. EC coupling involves activation of 2 different types of calcium channels: dihydropyridine receptors (DHPRs) located at the sarcolemma, and ryanodine receptors (RyR1s) located at the sarcoplasmic reticulum (SR). In response to electrical depolarization, DHPRs activate nearby and physically bound RyR1s, allowing Ca(2+) from the SR to move into the cytosol (termed voltage-gated Ca(2+) release, or VGCR). We recently found that CGRP stimulates VGCR by 350 % in as short as 1h. This effect, which lasts for at least 48 h, is due to activation of the CGRP receptor, and requires activation of the cAMP/PKA signaling pathway. CGRP also increases the amplitude of caffeine-induced Ca(2+) release (400 %); suggesting increased SR Ca(2+) content underlies stimulation of VGCR. Interestingly, in the long-term CGRP also increases the density of sarcolemmal DHPRs (up to 30%, within 24-48 h). We propose that these CGRP effects may contribute to prevent and/or restore symptoms in central core disease (CCD); a congenital myopathy that is linked to mutations in the gene encoding RyR1.

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Charge movement and calcium currents in skeletal muscle fibers are enhanced by GTP?S

Cited by 34 publications

References 20 publications

Voltage-dependent potentiation of L-type Ca2+ channels in skeletal muscle cells requires anchored cAMP-dependent protein kinase.

Voltage-dependent potentiation of L-type Ca2+ channels in skeletal muscle cells requires anchored cAMP-dependent protein kinase.

Control of Calcium Release in Functioning Skeletal Muscle Fibers

CGRP, a Vasodilator Neuropeptide that Stimulates Neuromuscular Transmission and EC Coupling

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