Axial tubule junctions control rapid calcium signaling in atria

2016 | journal article; research paper. A publication with affiliation to the University of Göttingen.

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​Axial tubule junctions control rapid calcium signaling in atria​
Brandenburg, S. ; Kohl, T. ; Williams, G. S. B.; Gusev, K.; Wagner, E. ; Rog-Zielinska, E. A. & Hebisch, E. et al.​ (2016) 
Journal of Clinical Investigation126(10) pp. 3999​-4015​.​ DOI: 

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Brandenburg, Sören ; Kohl, Tobias ; Williams, George S. B.; Gusev, Konstantin; Wagner, Eva ; Rog-Zielinska, Eva A.; Hebisch, Elke; Dura, Miroslav; Didié, Michael ; Gotthardt, Michael; Nikolaev, Viacheslav O. ; Kohl, Peter; Ward, Christopher W.; Lederer, W. Jonathan; Lehnart, Stephan E. ; Hasenfuß, Gerd 
The canonical atrial myocyte (AM) is characterized by sparse transverse tubule (TT) invaginations and slow intracellular Ca2+ propagation but exhibits rapid contractile activation that is susceptible to loss of function during hypertrophic remodeling. Here, we have identified a membrane structure and Ca2+-signaling complex that may enhance the speed of atrial contraction independently of phospholamban regulation. This axial couplon was observed in human and mouse atria and is composed of voluminous axial tubules (ATs) with extensive junctions to the sarcoplasmic reticulum (SR) that include ryanodine receptor 2 (RyR2) clusters. In mouse AM, AT structures triggered Ca2+ release from the SR approximately 2 times faster at the AM center than at the surface. Rapid Ca2+ release correlated with colocalization of highly phosphorylated RyR2 clusters at AT-SR junctions and earlier, more rapid shortening of central sarcomeres. In contrast, mice expressing phosphorylation-incompetent RyR2 displayed depressed AM sarcomere shortening and reduced in vivo atrial contractile function. Moreover, left atrial hypertrophy led to AT proliferation, with a marked increase in the highly phosphorylated RyR2-pS2808 cluster fraction, thereby maintaining cytosolic Ca2+ signaling despite decreases in RyR2 cluster density and RyR2 protein expression. AT couplon "super-hubs" thus underlie faster excitation-contraction coupling in health as well as hypertrophic compensatory adaptation and represent a structural and metabolic mechanism that may contribute to contractile dysfunction and arrhythmias.
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Journal of Clinical Investigation 
SFB 1002: Modulatorische Einheiten bei Herzinsuffizienz 
SFB 1002 | A01: cAMP- und cGMP- Mikrodomänen bei Herzhypertrophie und Insuffizienz 
SFB 1002 | A09: Lokale molekulare Nanodomänen-Regulation der kardialen Ryanodin-Rezeptor-Funktion 
SFB 1002 | S01: In vivo und in vitro Krankheitsmodelle 
SFB 1002 | S02: Hochauflösende Fluoreszenzmikroskopie und integrative Datenanalyse 
SFB 1002 | Z: Zentrale Organisation und Verwaltung 
Working Group
RG Brandenburg 
RG Hasenfuß (Transition zur Herzinsuffizienz) 
RG Lehnart (Cellular Biophysics and Translational Cardiology Section) 
RG Nikolaev (Cardiovascular Research Center) 
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