scholarly journals The Builders of the Junction: Roles of Junctophilin1 and Junctophilin2 in the Assembly of the Sarcoplasmic Reticulum–Plasma Membrane Junctions in Striated Muscle

Biomolecules ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 109
Author(s):  
Stefano Perni
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Intracellular Calcium ◽  
Cardiac Muscle ◽  
Structure Prediction ◽  
Calcium Release ◽  
Striated Muscle ◽  
Short Review ◽  
Published Data ◽  
Intracellular Calcium Release

Contraction of striated muscle is triggered by a massive release of calcium from the sarcoplasmic reticulum (SR) into the cytoplasm. This intracellular calcium release is initiated by membrane depolarization, which is sensed by voltage-gated calcium channels CaV1.1 (in skeletal muscle) and CaV1.2 (in cardiac muscle) in the plasma membrane (PM), which in turn activate the calcium-releasing channel ryanodine receptor (RyR) embedded in the SR membrane. This cross-communication between channels in the PM and in the SR happens at specialized regions, the SR-PM junctions, where these two compartments come in close proximity. Junctophilin1 and Junctophilin2 are responsible for the formation and stabilization of SR-PM junctions in striated muscle and actively participate in the recruitment of the two essential players in intracellular calcium release, CaV and RyR. This short review focuses on the roles of junctophilins1 and 2 in the formation and organization of SR-PM junctions in skeletal and cardiac muscle and on the functional consequences of the absence or malfunction of these proteins in striated muscle in light of recently published data and recent advancements in protein structure prediction.

scholarly journals Membrane junctions in xenopus eggs: their distribution suggests a role in calcium regulation

1983 ◽  
Vol 96 (4) ◽  
pp. 1159-1163 ◽  
Author(s):  
DM Gardiner ◽  
RD Grey
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Egg Activation ◽  
Electron Dense Material ◽  
Intracellular Calcium Release ◽  
Cortical Endoplasmic Reticulum ◽  
Center Distance ◽  
Lines Of Evidence

We have observed the presence of membrane junctions formed between the plasma membrane and cortical endoplasmic reticulum of mature, unactivated eggs of xenopus laevis. The parallel, paired membranes of the junction are separated by a 10-mn gap within which electron-dense material is present. This material occurs in patches with an average center-to-center distance of approximately 30 nm. These junctions are rare in immature (but fully grown) oocytes (approximately 2 percent of the plasma membrane is associated with junctions) and increase dramatically during progesterone-induced maturation. Junctions in the mature, unactivated egg are two to three times more abundant in the animal hemisphere (25-30 percent of the plasma membrane associated with junction) as compared with the vegetal hemisphere (10-15 percent). Junction density decreases rapidly to values characteristic of immature oocytes in response to egg activation. The plasma membrane-ER junctions of xenopus eggs are strikingly similar in structure to membrane junctions in muscle cells thought to be essential in the triggering of intracellular calcium release from the sarcoplasmic reticulum. In addition, the junctions' distinctive, animal-vegetal polarity of distribution, their dramatic appearance during maturation, and their disapperance during activation are correlated with previously documented patterns of calcium-mediated events in anuran eggs. We discuss several lines of evidence supporting the hypothesis that these junctions in xenopus eggs are sites that transduce extracellular events into intracellular calcium release during fertilization and activation of development.

The Anatomy of the Sarcoplasmic Reticulum in Vertebrate Skeletal Muscle: Its Implications for Excitation Contraction Coupling

1982 ◽  
Vol 37 (7-8) ◽  
pp. 665-678 ◽  
Author(s):  
Joachim R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Cardiac Muscle ◽  
Calcium Release ◽  
Striated Muscle ◽  
Band Region ◽  
Terminal Cisterna ◽  
Transmitter Substance ◽  
Main Components

Abstract The sarcoplasmic reticulum in situ is an intricate tubular network that surrounds the contractile material in striated muscle cells. Its topographical relationship to other intracellular components, especially the myofibrils, is rather rigidly mainiained by a cytoskeleton which enmeshes Z line material and sarcoplasmic reticulum and, ultimately, is anchored at the plasmalemma. As a result, the two main components of the sarcoplasmic reticulum, the junctional SR and the free SR, retain their typical location in the A band region and in the I band region, respectively. The junc­tional SR, which is thought to be the site for calcium storage and release for contraction, is, thus, always well within one micron of the regulatory proteins associated with the actin filaments. The junctional SR, a synonym for terminal cisterna applying to both skeletal and cardiac muscle, is generally held to be involved in the translation of the action potential into calcium release, mainly because of the close topographic apposition between the junctional SR and the plasmalemma, especially in skeletal muscle. This attractive structure-function correlation is challenged by the observation that in bird cardiac muscle 80% of the junctional SR is spacially far removed from plas­malemma, the site of electrical activity. This anomalous topography is not in conflict with the notion that translation of the action potential into calcium release may be accomplished by a dif­fusible transmitter substance, e.g. calcium. Any hypothesis dealing with this problem must ac­ count for the anatomy of the bird heart.

Dehydroepiandrosterone inhibits intracellular calcium release in β-cells by a plasma membrane-dependent mechanism

Steroids ◽  
2006 ◽  
Vol 71 (8) ◽  
pp. 691-699 ◽  
Author(s):  
Dongmin Liu ◽  
Min Ren ◽  
Xinyu Bing ◽  
Corey Stotts ◽  
Sundeep Deorah ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Β Cells ◽  
Intracellular Calcium Release ◽  
Dependent Mechanism

scholarly journals Orientia tsutsugamushi Inhibits Apoptosis of Macrophages by Retarding Intracellular Calcium Release

2002 ◽  
Vol 70 (8) ◽  
pp. 4692-4696 ◽  
Author(s):  
Mee-Kyung Kim ◽  
Seung-Yong Seong ◽  
Ju-Young Seoh ◽  
Tae-Hee Han ◽  
Hyeon-Je Song ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Calcium Release ◽  
Cytosolic Calcium ◽  
Orientia Tsutsugamushi ◽  
Cytosolic Calcium Concentration ◽  
Infected Cells ◽  
Intracellular Calcium Release ◽  
Calcium Redistribution ◽  
In Cells

ABSTRACT Orientia tsutsugamushi shows both pro- and antiapoptotic activities in infected vertebrate cells. Apoptosis of THP-1 cells induced by beauvericin was inhibited by O. tsutsugamushi infection. Beauvericin-induced calcium redistribution was significantly reduced and retarded in cells infected with O. tsutsugamushi. Antiapoptotic activities of O. tsutsugamushi in infected cells are most probably due to inhibition of the increase in the cytosolic calcium concentration.

scholarly journals A Membrane Estrogen Receptor Mediates Intracellular Calcium Release in Astrocytes

Endocrinology ◽  
2004 ◽  
Vol 145 (8) ◽  
pp. 3788-3795 ◽  
Author(s):  
Victor V. Chaban ◽  
Alexander J. Lakhter ◽  
Paul Micevych
Keyword(s):  
Estrogen Receptor ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Intracellular Calcium Release
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