IMR Press / FBL / Volume 7 / Issue 4 / DOI: 10.2741/A801

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
Structural interaction between RYRs and DHPRs in calcium release units of cardiac and skeletal muscle cells
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1 Department of Anesthesia Research, Brigham and Women’s Hospital, Harvard Medical School, Boston MA 02115, USA
Academic Editor:Hector Valdivia
Front. Biosci. (Landmark Ed) 2002, 7(4), 650–658; https://doi.org/10.2741/A801
Published: 1 March 2002
(This article belongs to the Special Issue The structure and function of calcium release channels)
Abstract

Excitation-contraction (e-c) coupling in muscle cells is a mechanism that allows transduction of exterior-membrane depolarization in Ca2+ release from the Sarcoplasmic Reticulum (SR). The communication between external and internal membranes is possible thanks to the interaction between Dihydropyridine Receptors (DHPRs), voltage-gated Ca2+ channels located in exterior membranes, and Ryanodine Receptors (RyRs), the Ca2+ release channels of the SR. In both skeletal and cardiac muscle cells the key structural element that allows DHPRs and RyRs to interact with each other is their vicinity. However, the signal that the two molecules use to communicate is not the same in the two muscle types. In the heart, the inward flux of Ca2+ through DHPRs, that follows depolarization, triggers the opening of RyRs (calcium induced calcium release). In skeletal muscle, on the other hand, Ca2+ is not needed for RyRs activation; instead the coupling between the two molecules involves a direct link between them (mechanical coupling). Ultrastructural studies show that functional differences can be explained by differences in the DHPR/RyR reciprocal association: whereas the two proteins are very close to each other in both muscles, DHPRs form tetrads only in skeletal fibers. Tetrads represent the structural DHPR/RyR link that allows Ca2+ independent coupling in skeletal muscle.

Keywords
Excitation-Contraction Coupling
Skeletal and Cardiac Muscle
Dihydropyridine Receptors
Ryanodine Receptors
Electron Microscopy
Review
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