Affiliation:
1. Department of Cell and Developmental Biology, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA (e-mail: )
Abstract
The junctional domain of sarcoplasmic reticulum (jSR) is specialized for receiving signals from the plasmalemma–transverse tubules and for releasing Ca2+during muscle activation. The junctional face of the jSR, facing the transverse tubules, is occupied by a molecular complex composed of the transmembrane Ca2+release channels (ryanodine receptors); the luminal protein calsequestrin (CSQ); the 2 membrane proteins, junctin (Jct), and triadin (Tr), which mediate CSQ-ryanodine receptor interactions; and several other components. Under the conditions prevailing within the sarcoplasmic reticulum lumen (physiological ionic strength, mostly due to K+and Ca2+ions), CSQ forms long linear polymers and the fixed protein gel is clearly visible in the electron microscope. The luminal domains of Jct and Tr are detectable but, overall, the 2 molecules are not clearly delineated. Cardiac muscles either overexpressing or bearing null mutations for 3 proteins of the junctional complex (CSQ, Jct, and Tr) reveal the contribution of these 3 components to the general architecture of the jSR.
Publisher
Canadian Science Publishing
Subject
Physiology (medical),Nutrition and Dietetics,Physiology,General Medicine,Endocrinology, Diabetes and Metabolism
Cited by
37 articles.
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