scholarly journals Neuromuscular synaptic patterning requires the function of skeletal muscle dihydropyridine receptors

2011 ◽  
Vol 14 (5) ◽  
pp. 570-577 ◽  
Author(s):  
Fujun Chen ◽  
Yun Liu ◽  
Yoshie Sugiura ◽  
Paul D Allen ◽  
Ronald G Gregg ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Dihydropyridine Receptors

scholarly journals Cooh-Terminal Truncated Alpha1S Subunits Conduct Current Better than Full-Length Dihydropyridine Receptors

2000 ◽  
Vol 116 (3) ◽  
pp. 341-348 ◽  
Author(s):  
James A. Morrill ◽  
Stephen C. Cannon
Keyword(s):  
Skeletal Muscle ◽  
Expression System ◽  
Ionic Currents ◽  
Full Length ◽  
Charge Movement ◽  
Functional Roles ◽  
Dihydropyridine Receptors ◽  
Gating Charge ◽  
Channel Opening ◽  
Voltage Gated Channels

Skeletal muscle dihydropyridine (DHP) receptors function both as voltage-activated Ca2+ channels and as voltage sensors for coupling membrane depolarization to release of Ca2+ from the sarcoplasmic reticulum. In skeletal muscle, the principal or α1S subunit occurs in full-length (∼10% of total) and post-transcriptionally truncated (∼90%) forms, which has raised the possibility that the two functional roles are subserved by DHP receptors comprised of different sized α1S subunits. We tested the functional properties of each form by injecting oocytes with cRNAs coding for full-length (α1S) or truncated (α1SΔC) α subunits. Both translation products were expressed in the membrane, as evidenced by increases in the gating charge (Qmax 80–150 pC). Thus, oocytes provide a robust expression system for the study of gating charge movement in α1S, unencumbered by contributions from other voltage-gated channels or the complexities of the transverse tubules. As in recordings from skeletal muscle, for heterologously expressed channels the peak inward Ba2+ currents were small relative to Qmax. The truncated α1SΔC protein, however, supported much larger ionic currents than the full-length product. These data raise the possibility that DHP receptors containing the more abundant, truncated form of the α1S subunit conduct the majority of the L-type Ca2+ current in skeletal muscle. Our data also suggest that the carboxyl terminus of the α1S subunit modulates the coupling between charge movement and channel opening.

scholarly journals Overexpression of IGF-1 Exclusively in Skeletal Muscle Prevents Age-related Decline in the Number of Dihydropyridine Receptors

1998 ◽  
Vol 273 (44) ◽  
pp. 28845-28851 ◽  
Author(s):  
Muthukrishnan Renganathan ◽  
Marı́a Laura Messi ◽  
Osvaldo Delbono
Keyword(s):  
Skeletal Muscle ◽  
Dihydropyridine Receptors ◽  
Age Related

scholarly journals Extensive but Coordinated Reorganization of the Membrane Skeleton in Myofibers of Dystrophic (mdx) Mice

1999 ◽  
Vol 144 (6) ◽  
pp. 1259-1270 ◽  
Author(s):  
McRae W. Williams ◽  
Robert J. Bloch
Keyword(s):  
Skeletal Muscle ◽  
Membrane Proteins ◽  
Muscle Fibers ◽  
Membrane Skeleton ◽  
Confocal Imaging ◽  
Mdx Mouse ◽  
Mdx Mice ◽  
Intracellular Membrane ◽  
Dystrophic Muscle ◽  
Dihydropyridine Receptors

We used immunofluorescence techniques and confocal imaging to study the organization of the membrane skeleton of skeletal muscle fibers of mdx mice, which lack dystrophin. β-Spectrin is normally found at the sarcolemma in costameres, a rectilinear array of longitudinal strands and elements overlying Z and M lines. However, in the skeletal muscle of mdx mice, β-spectrin tends to be absent from the sarcolemma over M lines and the longitudinal strands may be disrupted or missing. Other proteins of the membrane and associated cytoskeleton, including syntrophin, β-dystroglycan, vinculin, and Na,K-ATPase are also concentrated in costameres, in control myofibers, and mdx muscle. They also distribute into the same altered sarcolemmal arrays that contain β-spectrin. Utrophin, which is expressed in mdx muscle, also codistributes with β-spectrin at the mutant sarcolemma. By contrast, the distribution of structural and intracellular membrane proteins, including α-actinin, the Ca-ATPase and dihydropyridine receptors, is not affected, even at sites close to the sarcolemma. Our results suggest that in myofibers of the mdx mouse, the membrane- associated cytoskeleton, but not the nearby myoplasm, undergoes widespread coordinated changes in organization. These changes may contribute to the fragility of the sarcolemma of dystrophic muscle.

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 Multiple Regions of RyR1 Mediate Functional and Structural Interactions with α1S-Dihydropyridine Receptors in Skeletal Muscle

2002 ◽  
Vol 83 (6) ◽  
pp. 3230-3244 ◽  
Author(s):  
Feliciano Protasi ◽  
Cecilia Paolini ◽  
Junichi Nakai ◽  
Kurt G. Beam ◽  
Clara Franzini-Armstrong ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Dihydropyridine Receptors ◽  
Structural Interactions ◽  
Multiple Regions
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