Ratio of ryanodine to dihydropyridine receptors in cardiac and skeletal muscle and implications for E-C coupling

Bers, Donald M.; Stiffel, Virginia M.

doi:10.1152/ajpcell.1993.264.6.c1587

Cited by 199 publications

(193 citation statements)

References 23 publications

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“…However, the relative F‐FKBP fluorescence intensity (ΔF/F 0 ) within 250 nm around the local cluster peak intensity (Figure 1D) provides a direct quantitative readout that is proportional to the number of RyRs within that local cluster (or supercluster; Figure 1E). This F‐FKBP fluorescence intensity is linear with [F‐FKBP] and has been used to titrate the overall RyR concentration in cardiac myocytes, for comparison to 3 H‐ryanodine binding data 9, 29…”

Section: Resultsmentioning

confidence: 99%

Size Matters: Ryanodine Receptor Cluster Size Affects Arrhythmogenic Sarcoplasmic Reticulum Calcium Release

Galice

Xie

Yang

et al. 2018

JAHA

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BackgroundRyanodine receptors (RyR) mediate sarcoplasmic reticulum calcium (Ca2+) release and influence myocyte Ca2+ homeostasis and arrhythmias. In cardiac myocytes, RyRs are found in clusters of various sizes and shapes, and RyR cluster size may critically influence normal and arrhythmogenic Ca2+ spark and wave formation. However, the actual RyR cluster sizes at specific Ca2+ spark sites have never been measured in the physiological setting.Methods and ResultsHere we measured RyR cluster size and Ca2+ sparks simultaneously to assess how RyR cluster size influences Ca2+ sparks and sarcoplasmic reticulum Ca2+ leak. For small RyR cluster sizes (<50), Ca2+ spark frequency is very low but then increases dramatically at larger cluster sizes. In contrast, Ca2+ spark amplitude is nearly maximal even at relatively small RyR cluster size (≈10) and changes little at larger cluster size. These properties agreed with computational simulations of RyR gating within clusters.ConclusionsOur study explains how this combination of properties may limit arrhythmogenic Ca2+ sparks and wave propagation (at many junctions) while preserving the efficacy and spatial synchronization of Ca2+‐induced Ca2+‐release during normal excitation‐contraction coupling. However, variations in RyR cluster size among individual junctions and RyR sensitivity could exacerbate heterogeneity of local sarcoplasmic reticulum Ca2+ release and arrhythmogenesis under pathological conditions.

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Section: Resultsmentioning

confidence: 99%

Size Matters: Ryanodine Receptor Cluster Size Affects Arrhythmogenic Sarcoplasmic Reticulum Calcium Release

Galice

Xie

Yang

et al. 2018

JAHA

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“…Ryanodine binding has been previously used to estimate the total numbers of RyRs within the cell. Estimates of RyR binding range from 680 to 833 fmol/mg protein in rat (25,26), which can be used to calculate that there should be 2.1 to 2.6 ϫ 10 6 RyRs in a 30-pl cell (cf. ref.…”

Section: Discussionmentioning

confidence: 99%

Analysis of ryanodine receptor clusters in rat and human cardiac myocytes

Soeller¹,

Crossman²,

Gilbert

et al. 2007

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

145

183

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Single rat ventricular myocytes and human ventricle tissue sections were labeled with antibodies against the ryanodine receptor (RyR) and ␣-actinin to examine the 3D distribution of RyRs with confocal microscopy. Image contrast was maximized by refractive index matching and deconvolution. The RyR label formed discrete puncta representing clusters of RyRs or ''couplons'' around the edges of the myofilaments with a nearest-neighbor spacing of 0.66 ؎ 0.06 m in rat and 0.78 ؎ 0.07 m in human. Each bundle of myofibrils was served by approximately six couplons, which supplied a cross-sectional area of Ϸ0.6 m 2 in rat and Ϸ0.8 m 2 in human. Although the couplons were in reasonable registration with zlines, there were discontinuities in the longitudinal position of sarcomeres so that dislocations in the order of RyR clusters occurred. There was Ϸ53% longitudinal registration of RyR clusters, suggesting a nonrandom placement of couplons around the sarcomere. These data can explain the spherical propagation of Ca 2؉ waves and provide quantitative 3D data sets needed for accurate modeling of cardiac Ca 2؉ -induced Ca 2؉ release. By quantifying labeling intensity in rat ventricular myocytes, a lower limit of 78 RyRs per cluster (on average) was obtained. By modeling the couplon as a disk wrapping around a t-tubule and fitting cluster images, 95% of couplons contained between 120 and 260 RyRs (assuming that RyRs are tight packed with a spacing of 29 nm). Assuming similar labeling efficiency in human, from the fluorescence intensity alone we estimate that human ventricular myocytes contain Ϸ30% fewer RyRs per couplon than rat.calcium-induced calcium release ͉ excitation-contraction coupling ͉ sarcoplasmic reticulum I n cardiac ventricular muscle, excitation-contraction (EC) coupling arises from Ca 2ϩ release via clusters of ryanodine receptors (RyRs) in regions of close apposition between the sarcoplasmic reticulum (SR) and surface membranes in functional units called couplons (1, 2). Current work directed at understanding cardiac EC coupling is hindered by uncertainty in the size and 3D distribution of the couplons. Previous detailed analysis from electron micrographs has shown that typically 30-270 RyRs (depending on species) may be present in a couplon (1), but the thin sectioning associated with EM limits analysis of the spatial relationship between nearby and more distant couplons. Such knowledge is important, not only to make sense of the structures that underlie Ca 2ϩ sparks (3, 4) but also for detailed mathematical modeling of cardiac Ca 2ϩ metabolism.In this study, we have used immunocytochemistry combined with 3D imaging and analysis to both reveal the 3D organization of RyR clusters and estimate the numbers of RyRs within the couplon. Our analyses generally support some detailed quantitative measurements from EM (1), but also provide insight into organization in 3D at spatial scales that would be extremely laborious (if not impossible) to achieve by using conventional thin sectioning. In addition, the antibody labe...

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“…They are arranged so that bidirectional structural and functional coupling can occur between the proteins. The molecular mechanism of E-C coupling is fundamentally different between skeletal and cardiac muscle (Rios and Brum 1987;Bers and Stiffel 1993;Garcia et al 1994;Lamb 2000). In skeletal muscle a physical interaction between Ca v 1.1 and RyR1 is required for E-C coupling and SR Ca 2þ release; referred to as voltage-induced Ca 2þ release (Lamb 2000).…”

Section: Crystal Structure Of the Amino-terminal Domainmentioning

confidence: 99%

Ryanodine Receptors: Structure, Expression, Molecular Details, and Function in Calcium Release

Lanner¹,

Georgiou²,

Joshi³

et al. 2010

Cold Spring Harbor Perspectives in Biology

680

572

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Ryanodine receptors (RyRs) are located in the sarcoplasmic/endoplasmic reticulum membrane and are responsible for the release of Ca 2þ from intracellular stores during excitation-contraction coupling in both cardiac and skeletal muscle. RyRs are the largest known ion channels (.2MDa) and exist as three mammalian isoforms (RyR 1 -3), all of which are homotetrameric proteins that interact with and are regulated by phosphorylation, redox modifications, and a variety of small proteins and ions. Most RyR channel modulators interact with the large cytoplasmic domain whereas the carboxy-terminal portion of the protein forms the ion-conducting pore. Mutations in RyR2 are associated with human disorders such as catecholaminergic polymorphic ventricular tachycardia whereas mutations in RyR1 underlie diseases such as central core disease and malignant hyperthermia. This chapter examines the current concepts of the structure, function and regulation of RyRs and assesses the current state of understanding of their roles in associated disorders.

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Ratio of ryanodine to dihydropyridine receptors in cardiac and skeletal muscle and implications for E-C coupling

Cited by 199 publications

References 23 publications

Size Matters: Ryanodine Receptor Cluster Size Affects Arrhythmogenic Sarcoplasmic Reticulum Calcium Release

Size Matters: Ryanodine Receptor Cluster Size Affects Arrhythmogenic Sarcoplasmic Reticulum Calcium Release

Analysis of ryanodine receptor clusters in rat and human cardiac myocytes

Ryanodine Receptors: Structure, Expression, Molecular Details, and Function in Calcium Release

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