scholarly journals Role of Ryanodine Receptors in the Assembly of Calcium Release Units in Skeletal Muscle

1998 ◽  
Vol 140 (4) ◽  
pp. 831-842 ◽  
Author(s):  
Feliciano Protasi ◽  
Clara Franzini-Armstrong ◽  
Paul D. Allen
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Dihydropyridine Receptors ◽  
Section Electron ◽  
Freeze Fracture Electron Microscopy

Abstract. In muscle cells, excitation–contraction (e–c) coupling is mediated by “calcium release units,” junctions between the sarcoplasmic reticulum (SR) and exterior membranes. Two proteins, which face each other, are known to functionally interact in those structures: the ryanodine receptors (RyRs), or SR calcium release channels, and the dihydropyridine receptors (DHPRs), or L-type calcium channels of exterior membranes. In skeletal muscle, DHPRs form tetrads, groups of four receptors, and tetrads are organized in arrays that face arrays of feet (or RyRs). Triadin is a protein of the SR located at the SR–exterior membrane junctions, whose role is not known. We have structurally characterized calcium release units in a skeletal muscle cell line (1B5) lacking Ry1R. Using immunohistochemistry and freeze-fracture electron microscopy, we find that DHPR and triadin are clustered in foci in differentiating 1B5 cells. Thin section electron microscopy reveals numerous SR–exterior membrane junctions lacking foot structures (dyspedic). These results suggest that components other than Ry1Rs are responsible for targeting DHPRs and triadin to junctional regions. However, DHPRs in 1B5 cells are not grouped into tetrads as in normal skeletal muscle cells suggesting that anchoring to Ry1Rs is necessary for positioning DHPRs into ordered arrays of tetrads. This hypothesis is confirmed by finding a “restoration of tetrads” in junctional domains of surface membranes after transfection of 1B5 cells with cDNA encoding for Ry1R.

scholarly journals Coordinated Incorporation of Skeletal Muscle Dihydropyridine Receptors and Ryanodine Receptors in Peripheral Couplings of BC3H1 Cells

1997 ◽  
Vol 137 (4) ◽  
pp. 859-870 ◽  
Author(s):  
Feliciano Protasi ◽  
Clara Franzini-Armstrong ◽  
Bernhard E. Flucher
Keyword(s):  
Skeletal Muscle ◽  
Calcium Release ◽  
Surface Membrane ◽  
Ryanodine Receptors ◽  
Freeze Fracture ◽  
Cell Periphery ◽  
Calcium Release Channels ◽  
Transverse Tubular System ◽  
Dihydropyridine Receptors ◽  
Tubular System

Rapid release of calcium from the sarcoplasmic reticulum (SR) of skeletal muscle fibers during excitation–contraction (e–c) coupling is initiated by the interaction of surface membrane calcium channels (dihydropyridine receptors; DHPRs) with the calcium release channels of the SR (ryanodine receptors; RyRs, or feet). We studied the early differentiation of calcium release units, which mediate this interaction, in BC3H1 cells. Immunofluorescence labelings of differentiating myocytes with antibodies against α1 and α2 subunits of DHPRs, RyRs, and triadin show that the skeletal isoforms of all four proteins are abundantly expressed upon differentiation, they appear concomitantly, and they are colocalized. The transverse tubular system is poorly organized, and thus clusters of e–c coupling proteins are predominantly located at the cell periphery. Freeze fracture analysis of the surface membrane reveals tetrads of large intramembrane particles, arranged in orderly arrays. These appear concomitantly with arrays of feet (RyRs) and with the appearance of DHPR/RyS clusters, confirming that the four components of the tetrads correspond to skeletal muscle DHPRs. The arrangement of tetrads and feet in developing junctions indicates that incorporation of DHPRs in junctional domains of the surface membrane proceeds gradually and is highly coordinated with the formation of RyR arrays. Within the arrays, tetrads are positioned at a spacing of twice the distance between the feet. The incorporation of individual DHPRs into tetrads occurs exclusively at positions corresponding to alternate feet, suggesting that the assembly of RyR arrays not only guides the assembly of tetrads but also determines their characteristic spacing in the junction.

NF-κB activation by depolarization of skeletal muscle cells depends on ryanodine and IP3 receptor-mediated calcium signals

2007 ◽  
Vol 292 (5) ◽  
pp. C1960-C1970 ◽  
Author(s):  
Juan Antonio Valdés ◽  
Jorge Hidalgo ◽  
José Luis Galaz ◽  
Natalia Puentes ◽  
Mónica Silva ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Field Potential ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Ip3 Receptor ◽  
Pharmacological Agents ◽  
Calcium Dependent ◽  
Element Binding Protein

Depolarization of skeletal muscle cells by either high external K+ or repetitive extracellular field potential pulses induces calcium release from internal stores. The two components of this release are mediated by either ryanodine receptors or inositol 1,4,5-trisphosphate (IP3) receptors and show differences in kinetics, amplitude, and subcellular localization. We have reported that the transcriptional regulators including ERKs, cAMP/Ca2+-response element binding protein, c- fos, c- jun, and egr-1 are activated by K+-induced depolarization and that their activation requires IP3-dependent calcium release. We presently describe the activation of the nuclear transcription factor NF-κB in response to depolarization by either high K+ (chronic) or electrical pulses (fluctuating). Calcium transients of relative short duration activate an NF-κB reporter gene to an intermediate level, whereas long-lasting calcium increases obtained by prolonged electrical stimulation protocols of various frequencies induce maximal activation of NF-κB. This activation is independent of extracellular calcium, whereas calcium release mediated by either ryanodine or IP3 receptors contribute in all conditions tested. NF-κB activation is mediated by IκBα degradation and p65 translocation to the nucleus. Partial blockade by N-acetyl-l-cysteine, a general antioxidant, suggests the participation of reactive oxygen species. Calcium-dependent signaling pathways such as those linked to calcineurin and PKC also contribute to NF-κB activation by depolarization, as assessed by blockade through pharmacological agents. These results suggest that NF-κB activation in skeletal muscle cells is linked to membrane depolarization and depends on the duration of elevated intracellular calcium. It can be regulated by sequential activation of calcium release mediated by the ryanodine and by IP3 receptors.

scholarly journals Preparation and morphology of sarcoplasmic reticulum terminal cisternae from rabbit skeletal muscle.

1984 ◽  
Vol 99 (3) ◽  
pp. 875-885 ◽  
Author(s):  
A Saito ◽  
S Seiler ◽  
A Chu ◽  
S Fleischer
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Thin Section ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Morphological Characteristics ◽  
Negative Staining ◽  
Section Electron ◽  
Terminal Cisternae

We have developed a procedure to isolate, from skeletal muscle, enriched terminal cisternae of sarcoplasmic reticulum (SR), which retain morphologically intact junctional "feet" structures similar to those observed in situ. The fraction is largely devoid of transverse tubule, plasma membrane, mitochondria, triads (transverse tubules junctionally associated with terminal cisternae), and longitudinal cisternae, as shown by thin-section electron microscopy of representative samples. The terminal cisternae vesicles have distinctive morphological characteristics that differ from the isolated longitudinal cisternae (light SR) obtained from the same gradient. The terminal cisternae consist of two distinct types of membranes, i.e., the junctional face membrane and the Ca2+ pump protein-containing membrane, whereas the longitudinal cisternae contain only the Ca2+ pump protein-containing membrane. The junctional face membrane of the terminal cisternae contains feet structures that extend approximately 12 nm from the membrane surface and can be clearly visualized in thin section through using tannic acid enhancement, by negative staining and by freeze-fracture electron microscopy. Sections of the terminal cisternae, cut tangential to and intersecting the plane of the junctional face, reveal a checkerboardlike lattice of alternating, square-shaped feet structures and spaces each 20 nm square. Structures characteristic of the Ca2+ pump protein are not observed between the feet at the junctional face membrane, either in thin section or by negative staining, even though the Ca2+ pump protein is observed in the nonjunctional membrane on the remainder of the same vesicle. Likewise, freeze-fracture replicas reveal regions of the P face containing ropelike strands instead of the high density of the 7-8-nm particles referable to the Ca2+ pump protein. The intravesicular content of the terminal cisternae, mostly Ca2+-binding protein (calsequestrin), is organized in the form of strands, sometimes appearing paracrystalline, and attached to the inner face of the membrane in the vicinity of the junctional feet. The terminal cisternae preparation is distinct from previously described heavy SR fractions in that it contains the highest percentage of junctional face membrane with morphologically well-preserved junctional feet structures.

scholarly journals Insect elementary calcium release events measured in honeybee muscle cells

2021 ◽  
Vol 154 (9) ◽  
Author(s):  
Claude Collet ◽  
Mercedes Charreton ◽  
Laszlo Szabo ◽  
Marianna Takacs ◽  
Laszlo Csernoch ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Time Lapse ◽  
Bimodal Distribution ◽  
Point Of View ◽  
Confocal Imaging ◽  
Spatial Spread ◽  
Spatio Temporal

Subcellular calcium variations are involved in physiological and pathological mechanisms. Whereas elementary calcium release events (CREs) have been known for almost three decades in intact muscle cells isolated from vertebrates, they remained not characterized in invertebrates until recently. Dynamic confocal imaging was used on intact skeletal muscle cells isolated enzymatically from the adult honeybee legs to characterize spatio-temporal features of subcellular CREs. The frequency of these insect CREs, measured in x–y time lapse series, was higher than frequencies usually described in vertebrates. Spatial spread at half maximum was larger than in vertebrates and had a slightly ellipsoidal shape, two characteristics that may be related to ultrastructural features specific to invertebrate cells. In line-scan experiments, the histogram of CREs’ duration followed a bimodal distribution, supporting the existence of both sparks and embers. Unlike in vertebrates, embers and sparks had similar amplitudes, a difference that could be related to genomic differences and/or excitation–contraction coupling specificities in honeybee skeletal muscle fibers. Arthropods muscle cells show strong genomic, ultrastructural and physiological differences with vertebrates and a comparative analysis may help to better understanding the roles and regulations of CREs. From a toxicological point of view, such a comparison will lead to better anticipating the myotoxicity of new insecticides targeting ryanodine receptors. Recent studies described the effects of these insecticides on macroscopic calcium homeostasis in bee neurons and muscle cells. Here, cyantraniliprole, the most recently approved anthranilic diamide in Europe, triggers calcium transients in bee muscle cell as well. Cyantraniliprole effects on Ca2+ sparks are currently under study.

scholarly journals Elementary calcium release events in the skeletal muscle cells of the honey bee Apis mellifera

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Claude Collet ◽  
Mercédès Charreton ◽  
Laszlo Szabo ◽  
Marianna Takacs ◽  
Laszlo Csernoch ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Honey Bee ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Research Field ◽  
Confocal Imaging ◽  
Skeletal Muscle Cells ◽  
Muscle Fibres

AbstractCalcium sparks are involved in major physiological and pathological processes in vertebrate muscles but have never been characterized in invertebrates. Here, dynamic confocal imaging on intact skeletal muscle cells isolated enzymatically from the adult honey bee legs allowed the first spatio-temporal characterization of subcellular calcium release events (CREs) in an insect species. The frequency of CREs, measured in x–y time lapse series, was higher than frequencies usually described in vertebrates. Honey bee CREs had a larger spatial spread at half maximum than their vertebrate counterparts and a slightly ellipsoidal shape, two characteristics that may be related to ultrastructural features specific to invertebrate cells. In line-scan experiments, the histogram of CREs’ duration followed a bimodal distribution, supporting the existence of both sparks and embers. Unlike in vertebrates, embers and sparks had similar amplitudes, a difference that could be related to genomic differences and/or excitation–contraction coupling specificities in honey bee skeletal muscle fibres. The first characterization of CREs from an arthropod which shows strong genomic, ultrastructural and physiological differences with vertebrates may help in improving the research field of sparkology and more generally the knowledge in invertebrates cell Ca2+ homeostasis, eventually leading to a better understanding of their roles and regulations in muscles but also the myotoxicity of new insecticides targeting ryanodine receptors.

scholarly journals Dual role of junctin in the regulation of ryanodine receptors and calcium release in cardiac ventricular myocytes

2011 ◽  
Vol 589 (24) ◽  
pp. 6063-6080 ◽  
Author(s):  
Beth A. Altschafl ◽  
Demetrios A. Arvanitis ◽  
Oscar Fuentes ◽  
Qunying Yuan ◽  
Evangelia G. Kranias ◽  
...  
Keyword(s):  
Calcium Release ◽  
Ventricular Myocytes ◽  
Ryanodine Receptors ◽  
Dual Role ◽  
Cardiac Ventricular Myocytes
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