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Sarcolemmal Ca 2+ -entry through L-type Ca 2+ channels controls the profile of Ca 2+ -activated Cl − current in canine ventricular myocytes

Sarcolemmal Ca 2+ -entry through L-type Ca 2+ channels controls the profile of Ca 2+ -activated Cl − current in canine ventricular myocytes

Authors :
Norbert Szentandrássy
László Csernoch
János Magyar
István Baczkó
Kornél Kistamás
Balázs Horváth
Krisztina Váczi
Mónika Gönczi
Bence Hegyi
Péter P. Nánási
András Varró
György Seprényi
Tamás Bányász
Beatrix Dienes
Source :
Journal of Molecular and Cellular Cardiology. 97:125-139
Publication Year :
2016
Publisher :
Elsevier BV, 2016.

Abstract

Ca 2+ -activated Cl − current (I Cl(Ca) ) mediated by TMEM16A and/or Bestrophin-3 may contribute to cardiac arrhythmias. The true profile of I Cl(Ca) during an actual ventricular action potential (AP), however, is poorly understood. We aimed to study the profile of I Cl(Ca) systematically under physiological conditions (normal Ca 2+ cycling and AP voltage-clamp) as well as in conditions designed to change [Ca 2+ ] i . The expression of TMEM16A and/or Bestrophin-3 in canine and human left ventricular myocytes was examined. The possible spatial distribution of these proteins and their co-localization with Ca v 1.2 was also studied. The profile of I Cl(Ca), identified as a 9-anthracene carboxylic acid-sensitive current under AP voltage-clamp conditions, contained an early fast outward and a late inward component, overlapping early and terminal repolarizations, respectively. Both components were moderately reduced by ryanodine, while fully abolished by BAPTA, but not EGTA. [Ca 2+ ] i was monitored using Fura-2-AM. Setting [Ca 2+ ] i to the systolic level measured in the bulk cytoplasm (1.1 μM) decreased I Cl(Ca), while application of Bay K8644, isoproterenol, and faster stimulation rates increased the amplitude of I Cl(Ca) . Ca 2+ -entry through L-type Ca 2+ channels was essential for activation of I Cl(Ca) . TMEM16A and Bestrophin-3 showed strong co-localization with one another and also with Ca v 1.2 channels, when assessed using immunolabeling and confocal microscopy in both canine myocytes and human ventricular myocardium. Activation of I Cl(Ca) in canine ventricular cells requires Ca 2+ -entry through neighboring L-type Ca 2+ channels and is only augmented by SR Ca 2+ -release. Substantial activation of I Cl(Ca) requires high Ca 2+ concentration in the dyadic clefts which can be effectively buffered by BAPTA, but not EGTA.

Details

ISSN :
00222828
Volume :
97
Database :
OpenAIRE
Journal :
Journal of Molecular and Cellular Cardiology
Accession number :
edsair.doi.dedup.....9552b492f6e0552b06332cb91deba7c0
Full Text :
https://doi.org/10.1016/j.yjmcc.2016.05.006