Role of SK channel activation in determining the action potential configuration in freshly isolated human atrial myocytes from the SKArF study

Shamsaldeen, Yousif A.; Culliford, Lucy; Clout, Madeleine; James, Andrew F.; Ascione, Raimondo; Hancox, Jules C.; Marrion, Neil V.

doi:10.1016/j.bbrc.2019.03.074

Cited by 8 publications

(8 citation statements)

References 33 publications

(66 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the present study, we have used cells from paroxysmal AF patients and there is growing evidence that SK channels may contribute to AFinduced APD abbreviation. Some laboratories report upregulation of SK channel expression in chronic AF, but this is not a consistent finding [Peyronnet and Ravens (2019) and Shamsaldeen et al (2019), and primary references cited therein]. Therefore, we cannot exclude that the apamin-induced effects we observed are influenced by the diseased state of the tissue used.…”

Section: Apamincontrasting

confidence: 58%

Patch-Clamp Recordings of Action Potentials From Human Atrial Myocytes: Optimization Through Dynamic Clamp

et al. 2021

View full text Add to dashboard Cite

Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Consequently, novel therapies are being developed. Ultimately, the impact of compounds on the action potential (AP) needs to be tested in freshly isolated human atrial myocytes. However, the frequent depolarized state of these cells upon isolation seriously hampers reliable AP recordings.Purpose: We assessed whether AP recordings from single human atrial myocytes could be improved by providing these cells with a proper inward rectifier K+ current (IK1), and consequently with a regular, non-depolarized resting membrane potential (RMP), through “dynamic clamp”.Methods: Single myocytes were enzymatically isolated from left atrial appendage tissue obtained from patients with paroxysmal AF undergoing minimally invasive surgical ablation. APs were elicited at 1 Hz and measured using perforated patch-clamp methodology, injecting a synthetic IK1 to generate a regular RMP. The injected IK1 had strong or moderate rectification. For comparison, a regular RMP was forced through injection of a constant outward current. A wide variety of ion channel blockers was tested to assess their modulatory effects on AP characteristics.Results: Without any current injection, RMPs ranged from −9.6 to −86.2 mV in 58 cells. In depolarized cells (RMP positive to −60 mV), RMP could be set at −80 mV using IK1 or constant current injection and APs could be evoked upon stimulation. AP duration differed significantly between current injection methods (p < 0.05) and was shortest with constant current injection and longest with injection of IK1 with strong rectification. With moderate rectification, AP duration at 90% repolarization (APD90) was similar to myocytes with regular non-depolarized RMP, suggesting that a synthetic IK1 with moderate rectification is the most appropriate for human atrial myocytes. Importantly, APs evoked using each injection method were still sensitive to all drugs tested (lidocaine, nifedipine, E-4031, low dose 4-aminopyridine, barium, and apamin), suggesting that the major ionic currents of the atrial cells remained functional. However, certain drug effects were quantitatively dependent on the current injection approach used.Conclusion: Injection of a synthetic IK1 with moderate rectification facilitates detailed AP measurements in human atrial myocytes. Therefore, dynamic clamp represents a promising tool for testing novel antiarrhythmic drugs.

show abstract

Section: Apamincontrasting

confidence: 58%

Patch-Clamp Recordings of Action Potentials From Human Atrial Myocytes: Optimization Through Dynamic Clamp

et al. 2021

View full text Add to dashboard Cite

show abstract

“…4 C). This I SK profile is not limited to VCMs because a recent study of I SK in human atrial myocytes under AP clamp demonstrates complex current dynamics with two peaks (63), similar to our data in rat VCMs (Fig. 4 A), further confirming biphasic regulation of SK channels by [Ca 2þ ] during the Ca 2þ transient.…”

Section: Discussionsupporting

confidence: 87%

Impact of ISK Voltage and Ca2+/Mg2+-Dependent Rectification on Cardiac Repolarization

Bronk

Kim

Polina

et al. 2020

Biophysical Journal

View full text Add to dashboard Cite

Cardiac small conductance Ca 2þ -activated K þ (SK) channels are activated solely by Ca 2þ , but the SK current (I SK ) is inwardly rectified. However, the impact of inward rectification in shaping action potentials (APs) in ventricular cardiomyocytes under b-adrenergic stimulation or in disease states remains undefined. Two processes underlie this inward rectification: an intrinsic rectification caused by an electrostatic energy barrier from positively charged amino acids at the inner pore and a voltage-dependent Ca 2þ /Mg 2þ block. Thus, Ca 2þ has a biphasic effect on I SK , activating at low [Ca 2þ ] yet inhibiting I SK at high [Ca 2þ ]. We examined the effect of I SK rectification on APs in rat cardiomyocytes by simultaneously recording whole-cell apamin-sensitive currents and Ca 2þ transients during an AP waveform and developed a computer model of SK channels with rectification features. The typical profile of I SK during AP clamp included an initial peak (mean 1.6 pA/pF) followed by decay to the point that submembrane [Ca 2þ ] reached $10 mM. During the rest of the AP stimulus, I SK either plateaued or gradually increased as the cell repolarized and submembrane [Ca 2þ ] decreased further. We used a six-state gating model combined with intrinsic and Ca 2þ /Mg 2þ -dependent rectification to simulate I SK and investigated the relative contributions of each type of rectification to AP shape. This SK channel model replicates key features of I SK recording during AP clamp showing that intrinsic rectification limits I SK at high V m during the early and plateau phase of APs. Furthermore, the initial rise of Ca 2þ transients activates, but higher [Ca 2þ ] blocks SK channels, yielding a transient outward-like I SK trajectory. During the decay phase of Ca 2þ , the Ca 2þ -dependent block is released, causing I SK to rise again and contribute to repolarization. Therefore, I SK is an important repolarizing current, and the rectification characteristics of an SK channel determine its impact on early, plateau, and repolarization phases of APs.

show abstract

“…Building upon studies which show that heteromeric SK1:SK2 channels preferentially form during co-expression, it has previously been proposed that atrial myocytes display functional heteromeric SK2:SK3 channels ( 10 ). In support of this, it has been shown that SK2 and SK3 co-localize to within Z-lines in isolated atrial cardiomyocytes ( 10 , 32 ). The present study therefore aimed to investigate the ability of human SK2 (hSK2) and human SK3 (hSK3) subunits to form heteromeric channels.…”

mentioning

confidence: 64%

Preferential formation of human heteromeric SK2:SK3 channels limits homomeric SK channel assembly and function

Butler

Hancox

Marrion

2023

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Role of SK channel activation in determining the action potential configuration in freshly isolated human atrial myocytes from the SKArF study

Cited by 8 publications

References 33 publications

Patch-Clamp Recordings of Action Potentials From Human Atrial Myocytes: Optimization Through Dynamic Clamp

Patch-Clamp Recordings of Action Potentials From Human Atrial Myocytes: Optimization Through Dynamic Clamp

Impact of ISK Voltage and Ca2+/Mg2+-Dependent Rectification on Cardiac Repolarization

Preferential formation of human heteromeric SK2:SK3 channels limits homomeric SK channel assembly and function

Contact Info

Product

Resources

About