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Long‐QT syndrome‐related sodium channel mutations probed by the dynamic action potential clamp technique
Author(s) -
Berecki Géza,
Zegers Jan G.,
Bhuiyan Zahurul A.,
Verkerk Arie O.,
Wilders Ronald,
Van Ginneken Antoni C. G.
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2005.096578
Subject(s) - sodium channel , long qt syndrome , action (physics) , patch clamp , biophysics , clamp , cardiac action potential , mutation , sodium , chemistry , genetics , electrophysiology , medicine , biology , physics , qt interval , computer science , repolarization , gene , organic chemistry , clamping , quantum mechanics , computer vision
Long‐QT3 syndrome (LQT3) is linked to cardiac sodium channel gene ( SCN5A ) mutations. In this study, we used the ‘dynamic action potential clamp’ (dAPC) technique to effectively replace the native sodium current ( I Na ) of the Priebe–Beuckelmann human ventricular cell model with wild‐type (WT) or mutant I Na generated in a human embryonic kidney (HEK)‐293 cell that is voltage clamped by the free‐running action potential of the ventricular cell. We recorded I Na from HEK cells expressing either WT or LQT3‐associated Y1795C or A1330P SCN5A at 35°C, and let this current generate and shape the action potential (AP) of subepicardial, mid‐myocardial and subendocardial model cells. The HEK cell's endogenous background current was completely removed by a real‐time digital subtraction procedure. With WT I Na , AP duration (APD) was longer than with the original Priebe–Beuckelmann model I Na , due to a late I Na component of ∼30 pA that could not be revealed with conventional voltage‐clamp protocols. With mutant I Na , this late component was larger (∼100 pA), producing a marked increase in APD (∼70–80 ms at 1 Hz for the subepicardial model cell). The late I Na magnitude showed reverse frequency dependence, resulting in a significantly steeper APD–frequency relation in the mutant case. AP prolongation was more pronounced for the mid‐myocardial cell type, resulting in increased APD dispersion for each of the mutants. For both mutants, a 2 s pause following rapid (2 Hz) pacing resulted in distorted AP morphology and beat‐to‐beat fluctuations of I Na . Our dAPC data directly demonstrate the arrhythmogenic nature of LQT3‐associated SCN5A mutations.