Voltage-Dependent Modulation of Cardiac Ryanodine Receptors (RyR2) by Protamine

Phosphoinositide (3,5)-bisphosphate [PI(3,5)P2] is a newly identified phosphoinositide that modulates intracellular Ca2+ by activating ryanodine receptors (RyRs). Since the contractile state of arterial smooth muscle depends on the concentration of intracellular Ca2+, we hypothesized that by mobilizing sarcoplasmic reticulum (SR) Ca2+ stores PI(3,5)P2 would increase intracellular Ca2+ in arterial smooth muscle cells and cause vasocontraction. Using immunohistochemistry, we found that PI(3,5)P2 was present in the mouse aorta and that exogenously applied PI(3,5)P2 readily entered aortic smooth muscle cells. In isolated aortic smooth muscle cells, exogenous PI(3,5)P2 elevated intracellular Ca2+, and it also contracted aortic rings. Both the rise in intracellular Ca2+ and the contraction caused by PI(3,5)P2 were prevented by antagonizing RyRs, while the majority of the PI(3,5)P2 response was intact after blockade of inositol (1,4,5)-trisphosphate receptors. Depletion of SR Ca2+ stores with thapsigargin or caffeine and/or ryanodine blunted the Ca2+ response and greatly attenuated the contraction elicited by PI(3,5)P2. The removal of extracellular Ca2+ or addition of verapamil to inhibit voltage-dependent Ca2+ channels reduced but did not eliminate the Ca2+ or contractile responses to PI(3,5)P2. We also found that PI(3,5)P2 depolarized aortic smooth muscle cells and that LaCl3 inhibited those aspects of the PI(3,5)P2 response attributable to extracellular Ca2+. Thus, full and sustained aortic contractions to PI(3,5)P2 required the release of SR Ca2+, probably via the activation of RyR, and also extracellular Ca2+ entry via voltage-dependent Ca2+ channels.

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Effects of hindlimb suspension on cytosolic Ca2+ and [3H]ryanodine binding in cardiac myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.276.4.h1131 ◽

1999 ◽

Vol 276 (4) ◽

pp. H1131-H1136

Author(s):

Guillaume Halet ◽

Patricia Viard ◽

Jean-Luc Morel ◽

Jean Mironneau ◽

Chantal Mironneau

Keyword(s):

Ventricular Myocytes ◽

Binding Capacity ◽

Ryanodine Receptors ◽

Hindlimb Suspension ◽

Scatchard Analysis ◽

Channel Activity ◽

Intrinsic Properties ◽

Release Channel ◽

Voltage Dependent ◽

Cell Capacitance

Effects of a 14-day hindlimb suspension were examined on [3H]ryanodine binding to rat ventricular microsomes and on cytosolic Ca2+ concentration ([Ca2+]i) and voltage-dependent Ca2+channels in isolated ventricular myocytes. In suspended rats, the amplitude of the twitch [Ca2+]itransient was increased without significant modifications of the basal [Ca2+]iand sarcoplasmic reticulum content. Because cell capacitance, L-type Ca2+-current density, and Ca2+-channel gating were not significantly modified after suspension, the increase in [Ca2+]iwas expected to reside in a change in ryanodine receptors. Scatchard analysis of [3H]ryanodine binding revealed that suspension enhanced binding by increasing the affinity of the receptors for [3H]ryanodine without affecting the maximal binding capacity. Both Ca2+-release channel activity and [3H]ryanodine binding are modulated by Ca2+. However, the Ca2+ sensitivity of [3H]ryanodine binding remained unchanged after suspension. Taken together, these results suggest that the increase in twitch [Ca2+]itransients after suspension may result from a change in the intrinsic properties of the ryanodine receptors but not from a change in the expression level of these receptors.

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Alkaline pH shifts Ca2+ sparks to Ca2+waves in smooth muscle cells of pressurized cerebral arteries

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00603.2002 ◽

2002 ◽

Vol 283 (6) ◽

pp. H2169-H2176 ◽

Cited By ~ 26

Author(s):

Thomas J. Heppner ◽

Adrian D. Bonev ◽

L. Fernando Santana ◽

Mark T. Nelson

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Cerebral Arteries ◽

Ryanodine Receptors ◽

Muscle Cells ◽

Alkaline Ph ◽

Voltage Dependent ◽

Intracellular Ca ◽

A Minor ◽

External Ph

The effects of external pH (7.0–8.0) on intracellular Ca2+ signals (Ca2+ sparks and Ca2+ waves) were examined in smooth muscle cells from intact pressurized arteries from rats. Elevating the external pH from 7.4 to 7.5 increased the frequency of local, Ca2+transients, or “Ca2+ sparks,” and, at pH 7.6, significantly increased the frequency of Ca2+ waves. Alkaline pH-induced Ca2+ waves were inhibited by blocking Ca2+ release from ryanodine receptors but were not prevented by inhibitors of voltage-dependent Ca2+ channels, phospholipase C, or inositol 1,4,5-trisphosphate receptors. Activating ryanodine receptors with caffeine (5 mM) at pH 7.4 also induced repetitive Ca2+ waves. Alkalization from pH 7.4 to pH 7.8–8.0 induced a rapid and large vasoconstriction. Approximately 82% of the alkaline pH-induced vasoconstriction was reversed by inhibitors of voltage-dependent Ca2+ channels. The remaining constriction was reversed by inhibition of ryanodine receptors. These findings indicate that alkaline pH-induced Ca2+ waves originate from ryanodine receptors and make a minor, direct contribution to alkaline pH-induced vasoconstriction.

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Effect of inositol 1,4,5-trisphosphate receptor stimulation on mitochondrial [Ca2+] and secretion in chromaffin cells

Biochemical Journal ◽

10.1042/bj20011722 ◽

2002 ◽

Vol 365 (2) ◽

pp. 451-459 ◽

Cited By ~ 14

Author(s):

Mayte MONTERO ◽

Maria Teresa ALONSO ◽

Almudena ALBILLOS ◽

Inmaculada CUCHILLO-IBÁÑEZ ◽

Román OLIVARES ◽

...

Keyword(s):

Chromaffin Cells ◽

Ryanodine Receptors ◽

Catecholamine Secretion ◽

Mitochondrial Inhibitors ◽

High K ◽

Inositol 1,4,5 Trisphosphate ◽

Insp3 Receptors ◽

Voltage Dependent ◽

Trisphosphate Receptor ◽

Stimulation Of

Ca2+ uptake by mitochondria is a potentially important buffering system able to control cytosolic [Ca2+]. In chromaffin cells, we have shown previously that stimulation of either Ca2+ entry or Ca2+ release via ryanodine receptors triggers large increases in mitochondrial [Ca2+] ([Ca2+]M) approaching the millimolar range, whose blockade dramatically enhances catecholamine secretion [Montero, Alonso, Carnicero, Cuchillo-Ibañez, Albillos, Garcia, Carcia-Sancho and Alvarez (2000) Nat. Cell Biol. 2, 57–61]. In the present study, we have studied the effect of stimulation of inositol 1,4,5-trisphosphate (InsP3) receptors using histamine. We find that histamine produces a heterogeneous increase in [Ca2+]M, reaching peak levels at approx. 1μM in 70% of the mitochondrial space to several hundred micromolar in 2–3% of mitochondria. Intermediate levels were found in the rest of the mitochondrial space. Single-cell imaging experiments with aequorin showed that the heterogeneity had both an intercellular and a subcellular origin. Those mitochondria responding to histamine with increases in [Ca2+]M much greater than 1μM (30%) were the same as those that also responded with large increases in [Ca2+]M following stimulation with either high-K+ medium or caffeine. Blocking mitochondrial Ca2+ uptake with protonophores or mitochondrial inhibitors also enhanced catecholamine secretion induced by histamine. These results suggest that some InsP3 receptors tightly co-localize with ryanodine receptors and voltage-dependent Ca2+ channels in defined subplasmalemmal functional units designed to control secretion induced by different stimuli.

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Mechanisms and Regulation of Cardiac CaV1.2 Trafficking

International Journal of Molecular Sciences ◽

10.3390/ijms22115927 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5927

Author(s):

Maartje Westhoff ◽

Rose E. Dixon

Keyword(s):

Acute Stress ◽

Ryanodine Receptors ◽

Ventricular Myocardium ◽

Metabolic Demand ◽

Channel Trafficking ◽

Endosomal Recycling ◽

Current Thinking ◽

Voltage Dependent ◽

Cav1.2 Channels ◽

Cardiac Excitation

During cardiac excitation contraction coupling, the arrival of an action potential at the ventricular myocardium triggers voltage-dependent L-type Ca2+ (CaV1.2) channels in individual myocytes to open briefly. The level of this Ca2+ influx tunes the amplitude of Ca2+-induced Ca2+ release from ryanodine receptors (RyR2) on the junctional sarcoplasmic reticulum and thus the magnitude of the elevation in intracellular Ca2+ concentration and ultimately the downstream contraction. The number and activity of functional CaV1.2 channels at the t-tubule dyads dictates the amplitude of the Ca2+ influx. Trafficking of these channels and their auxiliary subunits to the cell surface is thus tightly controlled and regulated to ensure adequate sarcolemmal expression to sustain this critical process. To that end, recent discoveries have revealed the existence of internal reservoirs of preformed CaV1.2 channels that can be rapidly mobilized to enhance sarcolemmal expression in times of acute stress when hemodynamic and metabolic demand increases. In this review, we provide an overview of the current thinking on CaV1.2 channel trafficking dynamics in the heart. We highlight the numerous points of control including the biosynthetic pathway, the endosomal recycling pathway, ubiquitination, and lysosomal and proteasomal degradation pathways, and discuss the effects of β-adrenergic and angiotensin receptor signaling cascades on this process.

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High Time Resolution Analysis of Voltage-Dependent and Voltage-Independent Calcium Sparks in Frog Skeletal Muscle Fibers

Frontiers in Physiology ◽

10.3389/fphys.2020.599822 ◽

2020 ◽

Vol 11 ◽

Author(s):

Henrietta Cserne Szappanos ◽

János Vincze ◽

Dóra Bodnár ◽

Beatrix Dienes ◽

Martin F. Schneider ◽

...

Keyword(s):

Skeletal Muscle ◽

Time Resolution ◽

Ryanodine Receptors ◽

High Time ◽

Fiber Axis ◽

High Time Resolution ◽

Frog Skeletal Muscle ◽

Calcium Sparks ◽

Caffeine Treatment ◽

Voltage Dependent

In amphibian skeletal muscle calcium (Ca2+) sparks occur both as voltage-dependent and voltage-independent ligand-activated release events. However, whether their properties and their origin show similarities are still in debate. Elevated K+, constant Cl– content solutions were used to initiate small depolarizations of the resting membrane potential to activate dihydropyridine receptors (DHPR) and caffeine to open ryanodine receptors (RyR) on intact fibers. The properties of Ca2+ sparks observed under control conditions were compared to those measured on depolarized cells and those after caffeine treatment. Calcium sparks were recorded on intact frog skeletal muscle fibers using high time resolution confocal microscopy (x-y scan: 30 Hz). Sparks were elicited by 1 mmol/l caffeine or subthreshold depolarization to different membrane potentials. Both treatments increased the frequency of sparks and altered their morphology. Images were analyzed by custom-made computer programs. Both the amplitude (in ΔF/F0; 0.259 ± 0.001 vs. 0.164 ± 0.001; n = 24942 and 43326, respectively; mean ± SE, p < 0.001) and the full width at half maximum (FWHM, in μm; parallel with fiber axis: 2.34 ± 0.01 vs. 1.92 ± 0.01, p < 0.001; perpendicular to fiber axis: 2.08 ± 0.01 vs. 1.68 ± 0.01, p < 0.001) of sparks was significantly greater after caffeine treatment than on depolarized cells. 9.8% of the sparks detected on depolarized fibers and about one third of the caffeine activated sparks (29.7%) overlapped with another one on the previous frame on x-y scans. Centre of overlapping sparks travelled significantly longer distances between consecutive frames after caffeine treatment then after depolarization (in μm; 1.66 ± 0.01 vs. 0.95 ± 0.01, p < 0.001). Our results suggest that the two types of ryanodine receptors, the junctional RyRs controlled by DHPRs and the parajunctional RyRs are activated independently, using alternate ways, with the possibility of cooperation between neighboring release channels.

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Sympathetic nerve stimulation induces local endothelial Ca2+ signals to oppose vasoconstriction of mouse mesenteric arteries

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00773.2011 ◽

2012 ◽

Vol 302 (3) ◽

pp. H594-H602 ◽

Cited By ~ 58

Author(s):

Lydia W. M. Nausch ◽

Adrian D. Bonev ◽

Thomas J. Heppner ◽

Yvonne Tallini ◽

Michael I. Kotlikoff ◽

...

Keyword(s):

Smooth Muscle ◽

Nerve Stimulation ◽

Sympathetic Nerve ◽

Adrenergic Receptor ◽

Ryanodine Receptors ◽

Electrical Field Stimulation ◽

Sympathetic Nerves ◽

Mesenteric Arteries ◽

Sympathetic Nerve Stimulation ◽

Voltage Dependent

It is generally accepted that the endothelium regulates vascular tone independent of the activity of the sympathetic nervous system. Here, we tested the hypothesis that the activation of sympathetic nerves engages the endothelium to oppose vasoconstriction. Local inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ signals (“pulsars”) in or near endothelial projections to vascular smooth muscle (VSM) were measured in an en face mouse mesenteric artery preparation. Electrical field stimulation of sympathetic nerves induced an increase in endothelial cell (EC) Ca2+ pulsars, recruiting new pulsar sites without affecting activity at existing sites. This increase in Ca2+ pulsars was blocked by bath application of the α-adrenergic receptor antagonist prazosin or by TTX but was unaffected by directly picospritzing the α-adrenergic receptor agonist phenylephrine onto the vascular endothelium, indicating that nerve-derived norepinephrine acted through α-adrenergic receptors on smooth muscle cells. Moreover, EC Ca2+ signaling was not blocked by inhibitors of purinergic receptors, ryanodine receptors, or voltage-dependent Ca2+ channels, suggesting a role for IP3, rather than Ca2+, in VSM-to-endothelium communication. Block of intermediate-conductance Ca2+-sensitive K+ channels, which have been shown to colocalize with IP3 receptors in endothelial projections to VSM, enhanced nerve-evoked constriction. Collectively, our results support the concept of a transcellular negative feedback module whereby sympathetic nerve stimulation elevates EC Ca2+ signals to oppose vasoconstriction.

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Governance of arteriolar oscillation by ryanodine receptors

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00711.2002 ◽

2003 ◽

Vol 285 (1) ◽

pp. R125-R131 ◽

Cited By ~ 18

Author(s):

Tsuneo Takenaka ◽

Yoichi Ohno ◽

Koichi Hayashi ◽

Takao Saruta ◽

Hiromichi Suzuki

Keyword(s):

Calcium Channels ◽

Calcium Release ◽

Calcium Influx ◽

Ryanodine Receptors ◽

Voltage Dependent ◽

Fourth Series ◽

Voltage Dependent Calcium Channels ◽

Afferent Arterioles ◽

Series Of Experiments ◽

Bayk 8644

To investigate the role of ryanodine receptors in glomerular arterioles, experiments were performed using an isolated perfused hydronephrotic kidney model. In the first series of studies, BAYK-8644 (300 nM), a calcium agonist, constricted afferent (19.6 ± 0.6 to 17.6 ± 0.5 μm, n = 6, P < 0.01) but not efferent arterioles. Furthermore, BAYK-8644 elicited afferent arteriolar oscillatory movements. Subsequent administration of nifedipine (1 μM) inhibited both afferent arteriolar oscillation and constriction by BAYK-8644 (to 19.4 ± 0.5 μm). In the second group, although BAYK-8644 constricted afferent arterioles treated with 1 μM of thapsigargin (19.7 ± 0.6 to 16.8 ± 0.6 μm, n = 5, P < 0.05), it failed to induce rhythmic contraction. Removal of extracellular calcium with EGTA (2 mM) reversed BAYK-8644-induced afferent arteriolar constriction (to 20.0 ± 0.5 μm). In the third series of investigations, ryanodine (10 μM) but not 2-aminoethoxyphenyl borate (100 μM) abolished afferent arteriolar vasomotion by BAYK-8644. In the fourth series of experiments, in the presence of caffeine (1 mM), the stronger activation of voltage-dependent calcium channels by higher potassium media resulted in greater afferent arteriolar constriction and faster oscillation. Our results indicate that L-type calcium channels are rich in preglomerular but not postglomerular microvessels. Furthermore, the present findings suggest that either prolonged calcium influx through voltage-dependent calcium channels (BAYK-8644) or sensitized ryanodine receptors (caffeine) is required to trigger periodic calcium release through ryanodine receptors in afferent arterioles.

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The Inositol Trisphosphate/Calcium Signaling Pathway in Health and Disease

Physiological Reviews ◽

10.1152/physrev.00006.2016 ◽

2016 ◽

Vol 96 (4) ◽

pp. 1261-1296 ◽

Cited By ~ 204

Author(s):

Michael J. Berridge

Keyword(s):

Signaling Pathway ◽

Ryanodine Receptors ◽

Smooth Muscle Contraction ◽

Contributory Factor ◽

Primary Role ◽

Cellular Functions ◽

Excitable Cells ◽

Voltage Dependent ◽

Health And Disease ◽

And Function

Many cellular functions are regulated by calcium (Ca2+) signals that are generated by different signaling pathways. One of these is the inositol 1,4,5-trisphosphate/calcium (InsP3/Ca2+) signaling pathway that operates through either primary or modulatory mechanisms. In its primary role, it generates the Ca2+ that acts directly to control processes such as metabolism, secretion, fertilization, proliferation, and smooth muscle contraction. Its modulatory role occurs in excitable cells where it modulates the primary Ca2+ signal generated by the entry of Ca2+ through voltage-operated channels that releases Ca2+ from ryanodine receptors (RYRs) on the internal stores. In carrying out this modulatory role, the InsP3/Ca2+ signaling pathway induces subtle changes in the generation and function of the voltage-dependent primary Ca2+ signal. Changes in the nature of both the primary and modulatory roles of InsP3/Ca2+ signaling are a contributory factor responsible for the onset of a large number human diseases.

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