NCX-Mediated Subcellular Ca Dynamics Underlying Early Afterdepolarizations in LQT2 Cardiomyocytes.

Authors:
Mingwang Zhong
Mingwang Zhong
Northeastern University
Colin M Rees
Colin M Rees
Cardiovascular Research Center
Miami | United States
Dmitry Terentyev
Dmitry Terentyev
The Ohio State University
United States
Gideon Koren
Gideon Koren
University of Toronto
Toronto | Canada
Alain Karma
Alain Karma
Northeastern University
United States

Biophys J 2018 Sep 9;115(6):1019-1032. Epub 2018 Aug 9.

Physics Department and Center for Interdisciplinary Research in Complex Systems, Northeastern University, Boston, Massachusetts. Electronic address:

Long QT syndrome type 2 (LQT2) is a congenital disease characterized by loss of function mutations in hERG potassium channels (I). LQT2 is associated with fatal ventricular arrhythmias promoted by triggered activity in the form of early afterdepolarizations (EADs). We previously demonstrated that intracellular Ca handling is remodeled in LQT2 myocytes. Remodeling leads to aberrant late RyR-mediated Ca releases that drive forward-mode Na-Ca exchanger (NCX) current and slow repolarization to promote reopening of L-type calcium channels and EADs. Forward-mode NCX was found to be enhanced despite the fact that these late releases do not significantly alter the whole-cell cytosolic calcium concentration during a vulnerable period of phase 2 of the action potential corresponding to the onset of EADs. Here, we use a multiscale ventricular myocyte model to explain this finding. We show that because the local NCX current is a saturating nonlinear function of the local submembrane calcium concentration, a larger number of smaller-amplitude discrete Ca release events can produce a large increase in whole-cell forward-mode NCX current without increasing significantly the whole-cell cytosolic calcium concentration. Furthermore, we develop novel insights, to our knowledge, into how alterations of stochastic RyR activity at the single-channel level cause late aberrant Ca release events. Experimental measurements in transgenic LTQ2 rabbits confirm the critical arrhythmogenic role of NCX and identify this current as a potential target for antiarrhythmic therapies in LQT2.

Abstract Video

NCX-mediated Subcellular Ca2+ Dynamics Underlying Early Afterdepolarizations in LQT2 Cardiomyocytes


Source: Cell Press

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bpj.2018.08.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140381PMC

Still can't find the full text of the article?

We can help you send a request to the authors directly.
September 2018
158 Reads
3.970 Impact Factor

Publication Analysis

Top Keywords

ncx current
12
calcium concentration
12
forward-mode ncx
8
cytosolic calcium
8
release events
8
early afterdepolarizations
8
whole-cell cytosolic
8
lqt2
5
ncx
5
eads multiscale
4
multiscale ventricular
4
ventricular myocyte
4
onset eads
4
corresponding onset
4
phase action
4
action potential
4
potential corresponding
4
myocyte model
4
explain finding
4
saturating nonlinear
4

Similar Publications