Channel Activity of Cardiac Ryanodine Receptors (RyR2) Determines Potency and Efficacy of Flecainide and R-Propafenone against Arrhythmogenic Calcium Waves in Ventricular Cardiomyocytes

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.

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Nanoscale Organization of Junctophilin-2 and Ryanodine Receptors within Peripheral Couplings of Rat Ventricular Cardiomyocytes

Biophysical Journal ◽

10.1016/j.bpj.2012.01.034 ◽

2012 ◽

Vol 102 (5) ◽

pp. L19-L21 ◽

Cited By ~ 41

Author(s):

Isuru D. Jayasinghe ◽

David Baddeley ◽

Cherrie H.T. Kong ◽

Xander H.T. Wehrens ◽

Mark B. Cannell ◽

...

Keyword(s):

Ryanodine Receptors ◽

Ventricular Cardiomyocytes

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Canstatin modulates L-type calcium channel activity in rat ventricular cardiomyocytes

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2018.04.026 ◽

2018 ◽

Vol 499 (4) ◽

pp. 954-959 ◽

Cited By ~ 7

Author(s):

Keisuke Imoto ◽

Masaki Hirakawa ◽

Muneyoshi Okada ◽

Hideyuki Yamawaki

Keyword(s):

Calcium Channel ◽

Channel Activity ◽

Ventricular Cardiomyocytes

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Effects of canstatin on L-type Ca2+ channel activity in rat ventricular cardiomyocytes

Proceedings for Annual Meeting of The Japanese Pharmacological Society ◽

10.1254/jpssuppl.wcp2018.0_po4-2-9 ◽

2018 ◽

Vol WCP2018 (0) ◽

pp. PO4-2-9

Author(s):

Keisuke Imoto ◽

Masaki Hirakawa ◽

Muneyoshi Okada ◽

Hideyuki Yamawaki

Keyword(s):

Channel Activity ◽

Ventricular Cardiomyocytes

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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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Nanoscale remodeling of ryanodine receptor cluster size underlies cerebral microvascular dysfunction in Duchenne muscular dystrophy

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1804593115 ◽

2018 ◽

Vol 115 (41) ◽

pp. E9745-E9752 ◽

Cited By ~ 12

Author(s):

Harry A. T. Pritchard ◽

Paulo W. Pires ◽

Evan Yamasaki ◽

Pratish Thakore ◽

Scott Earley

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Ryanodine Receptors ◽

Microvascular Dysfunction ◽

Bk Channels ◽

Bk Channel ◽

Myogenic Tone ◽

Channel Activity ◽

Pial Arteries ◽

Electrophysiological Recordings

Duchenne muscular dystrophy (DMD) results from mutations in the gene encoding dystrophin which lead to impaired function of skeletal and cardiac muscle, but little is known about the effects of the disease on vascular smooth muscle cells (SMCs). Here we used the mdx mouse model to study the effects of mutant dystrophin on the regulation of cerebral artery and arteriole SMC contractility, focusing on an important Ca2+-signaling pathway composed of type 2 ryanodine receptors (RyR2s) on the sarcoplasmic reticulum (SR) and large-conductance Ca2+-activated K+ (BK) channels on the plasma membrane. Nanoscale superresolution image analysis revealed that RyR2 and BKα were organized into discrete clusters, and that the mean size of RyR2 clusters that colocalized with BKα was larger in SMCs from mdx mice (∼62 RyR2 monomers) than in controls (∼40 RyR2 monomers). We further found that the frequency and signal mass of spontaneous, transient Ca2+-release events through SR RyR2s (“Ca2+ sparks”) were greater in SMCs from mdx mice. Patch-clamp electrophysiological recordings indicated a corresponding increase in Ca2+-dependent BK channel activity. Using pressure myography, we found that cerebral pial arteries and parenchymal arterioles from mdx mice failed to develop appreciable spontaneous myogenic tone. Inhibition of RyRs with tetracaine and blocking of BK channels with paxilline restored myogenic tone to control levels, demonstrating that enhanced RyR and BK channel activity is responsible for the diminished pressure-induced constriction of arteries and arterioles from mdx mice. We conclude that increased size of RyR2 protein clusters in SMCs from mdx mice increases Ca2+ spark and BK channel activity, resulting in cerebral microvascular dysfunction.

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RyR2 Channel Activity Determines the Potency of State-Dependent RyR2 Blockers for Suppressing Arrhythmogenic Calcium Waves

Biophysical Journal ◽

10.1016/j.bpj.2010.12.3254 ◽

2011 ◽

Vol 100 (3) ◽

pp. 560a

Author(s):

Eleonora Savio Galimberti ◽

Bjorn C. Knollmann

Keyword(s):

Calcium Waves ◽

Channel Activity ◽

State Dependent ◽

Ryr2 Channel

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Voltage-gated Ca2+channel activity modulates smooth muscle cell calcium waves in hamster cremaster arterioles

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00292.2018 ◽

2018 ◽

Vol 315 (4) ◽

pp. H871-H878 ◽

Cited By ~ 3

Author(s):

William F. Jackson ◽

Erika M. Boerman

Keyword(s):

Smooth Muscle ◽

Channel Blocker ◽

Muscle Tone ◽

Myogenic Tone ◽

Calcium Waves ◽

Cremaster Muscle ◽

Channel Activity ◽

Voltage Gated ◽

Inositol 1,4,5 Trisphosphate ◽

Trisphosphate Receptor

Cremaster muscle arteriolar smooth muscle cells (SMCs) display inositol 1,4,5-trisphosphate receptor-dependent Ca2+waves that contribute to global myoplasmic Ca2+concentration and myogenic tone. However, the contribution made by voltage-gated Ca2+channels (VGCCs) to arteriolar SMC Ca2+waves is unknown. We tested the hypothesis that VGCC activity modulates SMC Ca2+waves in pressurized (80 cmH2O/59 mmHg, 34°C) hamster cremaster muscle arterioles loaded with Fluo-4 and imaged by confocal microscopy. Removal of extracellular Ca2+dilated arterioles (32 ± 3 to 45 ± 3 μm, n = 15, P < 0.05) and inhibited the occurrence, amplitude, and frequency of Ca2+waves ( n = 15, P < 0.05), indicating dependence of Ca2+waves on Ca2+influx. Blockade of VGCCs with nifedipine (1 μM) or diltiazem (10 μM) or deactivation of VGCCs by hyperpolarization of smooth muscle with the K+channel agonist cromakalim (10 μM) produced similar inhibition of Ca2+waves ( P < 0.05). Conversely, depolarization of SMCs with the K+channel blocker tetraethylammonium (1 mM) constricted arterioles from 26 ± 3 to 14 ± 2 μm ( n = 11, P < 0.05) and increased wave occurrence (9 ± 3 to 16 ± 3 waves/SMC), amplitude (1.6 ± 0.07 to 1.9 ± 0.1), and frequency (0.5 ± 0.1 to 0.9 ± 0.2 Hz, n = 10, P < 0.05), effects that were blocked by nifedipine (1 μM, P < 0.05). Similarly, the VGCC agonist Bay K8644 (5 nM) constricted arterioles from 14 ± 1 to 8 ± 1 μm and increased wave occurrence (3 ± 1 to 10 ± 1 waves/SMC) and frequency (0.2 ± 0.1 to 0.6 ± 0.1 Hz, n = 6, P < 0.05), effects that were unaltered by ryanodine (50 μM, n = 6, P > 0.05). These data support the hypothesis that Ca2+waves in arteriolar SMCs depend, in part, on the activity of VGCCs.NEW & NOTEWORTHY Arterioles that control blood flow to and within skeletal muscle depend on Ca2+influx through voltage-gated Ca2+channels and release of Ca2+from internal stores through inositol 1,4,5-trisphosphate receptors in the form of Ca2+waves to maintain pressure-induced smooth muscle tone.

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