Membranes, calcium, and coupling

1987 ◽  
Vol 65 (4) ◽  
pp. 686-690 ◽  
Author(s):  
R. S. Eisenberg
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Electrical Coupling ◽  
Eukaryotic Cell ◽  
Charge Movement ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Sarcoplasmic Reticulum Membrane ◽  
Voltage Change ◽  
Membrane Compartments ◽  
T System

Every eukaryotic cell contains systems linking the extracellular space and internal membrane compartments. These systems allow cells to communicate and, ultimately they allow the nervous system to control most of the cytoplasmic activity. In skeletal muscle, this system is called "excitation–contraction coupling." While much is known of the early and late steps in coupling, the critical link between the cell (i.e., here the T system) membrane and sarcoplasmic reticulum membrane is not known. Electrical coupling cannot easily account for experimental results; here we show that the Ca2+ influx is not causally related to the excitation–contraction coupling. The most likely mechanism seems to be a variant of the "remote control model" in which a voltage change and accompanying charge movement in the T membrane activates an enzyme tethered to the cytoplasmic leaflet of the T membrane but spanning part of the T – sarcoplasmic reticulum gap.

scholarly journals Electrical models of excitation-contraction coupling and charge movement in skeletal muscle.

1980 ◽  
Vol 76 (1) ◽  
pp. 1-31 ◽  
Author(s):  
R T Mathias ◽  
R A Levis ◽  
R S Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Ionic Current ◽  
Charge Movement ◽  
Transient Currents ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Intramembrane Charge Movement ◽  
Terminal Cisternae ◽  
T System

The consequences of ionic current flow from the T system to the sarcoplasmic reticulum (SR) of skeletal muscle are examined. The Appendix analyzes a simple model in which the conductance gx, linking T system and SR, is in series with a parallel resistor and capacitor having fixed values. The conductance gx is supposed to increase rapidly with depolarization and to decrease slowly with repolarization. Nonlinear transient currents computed from this model have some of the properties of gating currents produced by intramembrane charge movement. In particular, the integral of the transient current upon depolarization approximates that upon repolarization. Thus, equality of nonlinear charge movement can occur without intramembrane charge movement. A more complicated model is used in the text to fit the structure of skeletal muscle and other properties of its charge movement. Rectification is introduced into gx and the membrane conductance of the terminal cisternae to give asymmetry in the time-course of the transient currents and saturation in the curve relating charge movement to depolarization, respectively. The more complex model fits experimental data quite well if the longitudinal tubules of the sarcoplasmic reticulum are isolated from the terminal cisternae by a substantial resistance and if calcium release from the terminal cisternae is, for the most part, electrically silent. Specific experimental tests of the model are proposed, and the implications for excitation-contraction coupling are discussed.

scholarly journals CYTOCHEMICAL LOCALIZATION OF CHOLINESTERASE ACTIVITY IN ADULT RABBIT HEART

1971 ◽  
Vol 19 (6) ◽  
pp. 376-381 ◽  
Author(s):  
MARTIN HAGOPIAN ◽  
VIRGINIA M. TENNYSON
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Papillary Muscle ◽  
Cholinesterase Activity ◽  
Acetylcholinesterase Activity ◽  
Rabbit Heart ◽  
Adult Rabbit ◽  
Cytochemical Localization ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
T System

The papillary muscle of the adult rabbit heart was studied by a modification of the Koelle-Friedenwald copper thiocholine technique for the localization of cholinesterase activity. Butyrylcholinesterase (BuChE), identified by its substrate and inhibitor specificity, is found mainly in the terminal sacs of the sarcoplasmic reticulum adjacent to the T system. The localization of the reaction product in this particular site suggests that BuChE may play a role in excitation-contraction coupling in the adult rabbit heart. The present findings are also discussed in comparison with our previous work on the localization of acetylcholinesterase activity in the embryonic rabbit heart.

scholarly journals Minor sarcoplasmic reticulum membrane components that modulate excitation-contraction coupling in striated muscles

2009 ◽  
Vol 587 (13) ◽  
pp. 3071-3079 ◽  
Author(s):  
Susan Treves ◽  
Mirko Vukcevic ◽  
Marcin Maj ◽  
Raphael Thurnheer ◽  
Barbara Mosca ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Striated Muscles ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Sarcoplasmic Reticulum Membrane ◽  
Membrane Components

scholarly journals Cytoskeletal Tropomyosin Tm5NM1 Is Required for Normal Excitation–Contraction Coupling in Skeletal Muscle

2009 ◽  
Vol 20 (1) ◽  
pp. 400-409 ◽  
Author(s):  
Nicole Vlahovich ◽  
Anthony J. Kee ◽  
Chris Van der Poel ◽  
Emma Kettle ◽  
Delia Hernandez-Deviez ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Actin Filaments ◽  
Skeletal Muscles ◽  
Actin Binding ◽  
Membrane Association ◽  
Actin Microfilaments ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
T System

The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation–contraction coupling in skeletal muscle.

scholarly journals Remodeling of t-system and proteins underlying excitation-contraction coupling in aging versus failing human heart

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yankun Lyu ◽  
Vipin K. Verma ◽  
Younjee Lee ◽  
Iosif Taleb ◽  
Rachit Badolia ◽  
...  
Keyword(s):  
Heart Function ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Left Ventricular Myocardium ◽  
Excitation Contraction Coupling ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Senescent Phenotype ◽  
Cellular Microstructure ◽  
T System

AbstractIt is well established that the aging heart progressively remodels towards a senescent phenotype, but alterations of cellular microstructure and their differences to chronic heart failure (HF) associated remodeling remain ill-defined. Here, we show that the transverse tubular system (t-system) and proteins underlying excitation-contraction coupling in cardiomyocytes are characteristically remodeled with age. We shed light on mechanisms of this remodeling and identified similarities and differences to chronic HF. Using left ventricular myocardium from donors and HF patients with ages between 19 and 75 years, we established a library of 3D reconstructions of the t-system as well as ryanodine receptor (RyR) and junctophilin 2 (JPH2) clusters. Aging was characterized by t-system alterations and sarcolemmal dissociation of RyR clusters. This remodeling was less pronounced than in HF and accompanied by major alterations of JPH2 arrangement. Our study indicates that targeting sarcolemmal association of JPH2 might ameliorate age-associated deficiencies of heart function.

Calmodulin and Excitation-Contraction Coupling

Physiology ◽  
2000 ◽  
Vol 15 (6) ◽  
pp. 281-284 ◽  
Author(s):  
Susan L. Hamilton ◽  
Irina Serysheva ◽  
Gale M. Strasburg
Keyword(s):  
Skeletal Muscle ◽  
Ion Channels ◽  
Sarcoplasmic Reticulum ◽  
Release Channel ◽  
Excitation Contraction Coupling ◽  
Transverse Tubule ◽  
Contraction Coupling ◽  
Voltage Dependent ◽  
Important Regulator ◽  
Precise Role

Excitation-contraction coupling in cardiac and skeletal muscle involves the transverse-tubule voltage-dependent Ca2+ channel and the sarcoplasmic reticulum Ca2+ release channel. Both of these ion channels bind and are modulated by calmodulin in both its Ca2+-bound and Ca2+-free forms. Calmodulin is, therefore, potentially an important regulator of excitation-contraction coupling. Its precise role, however, has not yet been defined.

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