Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation

Jordi Heijman; Xiaobo Zhou; Stefano Morotti; Cristina E. Molina; Issam H. Abu-Taha; Marcel Tekook; Thomas Jespersen; Yiqiao Zhang; Shokoufeh Dobrev; Hendrik Milting; Jan Gummert; Matthias Karck; Markus Kamler; Ali El-Armouche; Arnela Saljic; Eleonora Grandi; Stanley Nattel; Dobromir Dobrev

doi:10.1161/CIRCRESAHA.122.321858

Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation

Jordi Heijman, Xiaobo Zhou, Stefano Morotti, Cristina E. Molina, Issam H. Abu-Taha, Marcel Tekook, Thomas Jespersen, Yiqiao Zhang, Shokoufeh Dobrev^*, Hendrik Milting, Jan Gummert, Matthias Karck, Markus Kamler, Ali El-Armouche, Arnela Saljic, Eleonora Grandi, Stanley Nattel, Dobromir Dobrev^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Background:Small-conductance Ca2+-activated K+ (SK)-channel inhibitors have antiarrhythmic effects in animal models of atrial fibrillation (AF), presenting a potential novel antiarrhythmic option. However, the regulation of SK-channels in human atrial cardiomyocytes and its modification in patients with AF are poorly understood and were the object of this study. Methods:Apamin-sensitive SK-channel current (I-SK) and action potentials were recorded in human right-atrial cardiomyocytes from sinus rhythm control (Ctl) patients or patients with (long-standing persistent) chronic AF (cAF). Results:I-SK was significantly higher, and apamin caused larger action potential prolongation in cAF- versus Ctl-cardiomyocytes. Sensitivity analyses in an in silico human atrial cardiomyocyte model identified I-K1 and I-SK as major regulators of repolarization. Increased I-SK in cAF was not associated with increases in mRNA/protein levels of SK-channel subunits in either right- or left-atrial tissue homogenates or right-atrial cardiomyocytes, but the abundance of SK2 at the sarcolemma was larger in cAF versus Ctl in both tissue-slices and cardiomyocytes. Latrunculin-A and primaquine (anterograde and retrograde protein-trafficking inhibitors) eliminated the differences in SK2 membrane levels and I-SK between Ctl- and cAF-cardiomyocytes. In addition, the phosphatase-inhibitor okadaic acid reduced I-SK amplitude and abolished the difference between Ctl- and cAF-cardiomyocytes, indicating that reduced calmodulin-Thr80 phosphorylation due to increased protein phosphatase-2A levels in the SK-channel complex likely contribute to the greater I-SK in cAF-cardiomyocytes. Finally, rapid electrical activation (5 Hz, 10 minutes) of Ctl-cardiomyocytes promoted SK2 membrane-localization, increased I-SK and reduced action potential duration, effects greatly attenuated by apamin. Latrunculin-A or primaquine prevented the 5-Hz-induced I-SK-upregulation. Conclusions:I-SK is upregulated in patients with cAF due to enhanced channel function, mediated by phosphatase-2A-dependent calmodulin-Thr80 dephosphorylation and tachycardia-dependent enhanced trafficking and targeting of SK-channel subunits to the sarcolemma. The observed AF-associated increases in I-SK, which promote reentry-stabilizing action potential duration shortening, suggest an important role for SK-channels in AF auto-promotion and provide a rationale for pursuing the antiarrhythmic effects of SK-channel inhibition in humans.

Original language	English
Pages (from-to)	E116-E133
Number of pages	18
Journal	Circulation Research
Volume	132
Issue number	9
DOIs	https://doi.org/10.1161/CIRCRESAHA.122.321858
Publication status	Published - 28 Apr 2023

Keywords

actinin
apamin
atrial fibrillation
atrial remodeling
calmodulin
protein phosphatase-2A
protein transport
CA2+-ACTIVATED K+ CHANNELS
ACTIVATED POTASSIUM CHANNELS
SMALL-CONDUCTANCE
CA2+ LEAK
PROTEIN
EXPRESSION
MECHANISMS
ELECTROPHYSIOLOGY
REFRACTORINESS
ALPHA-ACTININ2

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10.1161/CIRCRESAHA.122.321858

Cite this

Heijman, J., Zhou, X., Morotti, S., Molina, C. E., Abu-Taha, I. H., Tekook, M., Jespersen, T., Zhang, Y., Dobrev, S., Milting, H., Gummert, J., Karck, M., Kamler, M., El-Armouche, A., Saljic, A., Grandi, E., Nattel, S., & Dobrev, D. (2023). Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation. Circulation Research, 132(9), E116-E133. https://doi.org/10.1161/CIRCRESAHA.122.321858

@article{e9f4218d01084422badd31d5105f9cda,

title = "Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation",

abstract = "Background:Small-conductance Ca2+-activated K+ (SK)-channel inhibitors have antiarrhythmic effects in animal models of atrial fibrillation (AF), presenting a potential novel antiarrhythmic option. However, the regulation of SK-channels in human atrial cardiomyocytes and its modification in patients with AF are poorly understood and were the object of this study. Methods:Apamin-sensitive SK-channel current (I-SK) and action potentials were recorded in human right-atrial cardiomyocytes from sinus rhythm control (Ctl) patients or patients with (long-standing persistent) chronic AF (cAF). Results:I-SK was significantly higher, and apamin caused larger action potential prolongation in cAF- versus Ctl-cardiomyocytes. Sensitivity analyses in an in silico human atrial cardiomyocyte model identified I-K1 and I-SK as major regulators of repolarization. Increased I-SK in cAF was not associated with increases in mRNA/protein levels of SK-channel subunits in either right- or left-atrial tissue homogenates or right-atrial cardiomyocytes, but the abundance of SK2 at the sarcolemma was larger in cAF versus Ctl in both tissue-slices and cardiomyocytes. Latrunculin-A and primaquine (anterograde and retrograde protein-trafficking inhibitors) eliminated the differences in SK2 membrane levels and I-SK between Ctl- and cAF-cardiomyocytes. In addition, the phosphatase-inhibitor okadaic acid reduced I-SK amplitude and abolished the difference between Ctl- and cAF-cardiomyocytes, indicating that reduced calmodulin-Thr80 phosphorylation due to increased protein phosphatase-2A levels in the SK-channel complex likely contribute to the greater I-SK in cAF-cardiomyocytes. Finally, rapid electrical activation (5 Hz, 10 minutes) of Ctl-cardiomyocytes promoted SK2 membrane-localization, increased I-SK and reduced action potential duration, effects greatly attenuated by apamin. Latrunculin-A or primaquine prevented the 5-Hz-induced I-SK-upregulation. Conclusions:I-SK is upregulated in patients with cAF due to enhanced channel function, mediated by phosphatase-2A-dependent calmodulin-Thr80 dephosphorylation and tachycardia-dependent enhanced trafficking and targeting of SK-channel subunits to the sarcolemma. The observed AF-associated increases in I-SK, which promote reentry-stabilizing action potential duration shortening, suggest an important role for SK-channels in AF auto-promotion and provide a rationale for pursuing the antiarrhythmic effects of SK-channel inhibition in humans.",

keywords = "actinin, apamin, atrial fibrillation, atrial remodeling, calmodulin, protein phosphatase-2A, protein transport, CA2+-ACTIVATED K+ CHANNELS, ACTIVATED POTASSIUM CHANNELS, SMALL-CONDUCTANCE, CA2+ LEAK, PROTEIN, EXPRESSION, MECHANISMS, ELECTROPHYSIOLOGY, REFRACTORINESS, ALPHA-ACTININ2",

author = "Jordi Heijman and Xiaobo Zhou and Stefano Morotti and Molina, {Cristina E.} and Abu-Taha, {Issam H.} and Marcel Tekook and Thomas Jespersen and Yiqiao Zhang and Shokoufeh Dobrev and Hendrik Milting and Jan Gummert and Matthias Karck and Markus Kamler and Ali El-Armouche and Arnela Saljic and Eleonora Grandi and Stanley Nattel and Dobromir Dobrev",

year = "2023",

month = apr,

day = "28",

doi = "10.1161/CIRCRESAHA.122.321858",

language = "English",

volume = "132",

pages = "E116--E133",

journal = "Circulation Research",

issn = "0009-7330",

publisher = "LIPPINCOTT WILLIAMS & WILKINS",

number = "9",

}

Heijman, J, Zhou, X, Morotti, S, Molina, CE, Abu-Taha, IH, Tekook, M, Jespersen, T, Zhang, Y, Dobrev, S, Milting, H, Gummert, J, Karck, M, Kamler, M, El-Armouche, A, Saljic, A, Grandi, E, Nattel, S & Dobrev, D 2023, 'Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation', Circulation Research, vol. 132, no. 9, pp. E116-E133. https://doi.org/10.1161/CIRCRESAHA.122.321858

TY - JOUR

T1 - Enhanced Ca2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation

AU - Heijman, Jordi

AU - Zhou, Xiaobo

AU - Morotti, Stefano

AU - Molina, Cristina E.

AU - Abu-Taha, Issam H.

AU - Tekook, Marcel

AU - Jespersen, Thomas

AU - Zhang, Yiqiao

AU - Dobrev, Shokoufeh

AU - Milting, Hendrik

AU - Gummert, Jan

AU - Karck, Matthias

AU - Kamler, Markus

AU - El-Armouche, Ali

AU - Saljic, Arnela

AU - Grandi, Eleonora

AU - Nattel, Stanley

AU - Dobrev, Dobromir

PY - 2023/4/28

Y1 - 2023/4/28

N2 - Background:Small-conductance Ca2+-activated K+ (SK)-channel inhibitors have antiarrhythmic effects in animal models of atrial fibrillation (AF), presenting a potential novel antiarrhythmic option. However, the regulation of SK-channels in human atrial cardiomyocytes and its modification in patients with AF are poorly understood and were the object of this study. Methods:Apamin-sensitive SK-channel current (I-SK) and action potentials were recorded in human right-atrial cardiomyocytes from sinus rhythm control (Ctl) patients or patients with (long-standing persistent) chronic AF (cAF). Results:I-SK was significantly higher, and apamin caused larger action potential prolongation in cAF- versus Ctl-cardiomyocytes. Sensitivity analyses in an in silico human atrial cardiomyocyte model identified I-K1 and I-SK as major regulators of repolarization. Increased I-SK in cAF was not associated with increases in mRNA/protein levels of SK-channel subunits in either right- or left-atrial tissue homogenates or right-atrial cardiomyocytes, but the abundance of SK2 at the sarcolemma was larger in cAF versus Ctl in both tissue-slices and cardiomyocytes. Latrunculin-A and primaquine (anterograde and retrograde protein-trafficking inhibitors) eliminated the differences in SK2 membrane levels and I-SK between Ctl- and cAF-cardiomyocytes. In addition, the phosphatase-inhibitor okadaic acid reduced I-SK amplitude and abolished the difference between Ctl- and cAF-cardiomyocytes, indicating that reduced calmodulin-Thr80 phosphorylation due to increased protein phosphatase-2A levels in the SK-channel complex likely contribute to the greater I-SK in cAF-cardiomyocytes. Finally, rapid electrical activation (5 Hz, 10 minutes) of Ctl-cardiomyocytes promoted SK2 membrane-localization, increased I-SK and reduced action potential duration, effects greatly attenuated by apamin. Latrunculin-A or primaquine prevented the 5-Hz-induced I-SK-upregulation. Conclusions:I-SK is upregulated in patients with cAF due to enhanced channel function, mediated by phosphatase-2A-dependent calmodulin-Thr80 dephosphorylation and tachycardia-dependent enhanced trafficking and targeting of SK-channel subunits to the sarcolemma. The observed AF-associated increases in I-SK, which promote reentry-stabilizing action potential duration shortening, suggest an important role for SK-channels in AF auto-promotion and provide a rationale for pursuing the antiarrhythmic effects of SK-channel inhibition in humans.

AB - Background:Small-conductance Ca2+-activated K+ (SK)-channel inhibitors have antiarrhythmic effects in animal models of atrial fibrillation (AF), presenting a potential novel antiarrhythmic option. However, the regulation of SK-channels in human atrial cardiomyocytes and its modification in patients with AF are poorly understood and were the object of this study. Methods:Apamin-sensitive SK-channel current (I-SK) and action potentials were recorded in human right-atrial cardiomyocytes from sinus rhythm control (Ctl) patients or patients with (long-standing persistent) chronic AF (cAF). Results:I-SK was significantly higher, and apamin caused larger action potential prolongation in cAF- versus Ctl-cardiomyocytes. Sensitivity analyses in an in silico human atrial cardiomyocyte model identified I-K1 and I-SK as major regulators of repolarization. Increased I-SK in cAF was not associated with increases in mRNA/protein levels of SK-channel subunits in either right- or left-atrial tissue homogenates or right-atrial cardiomyocytes, but the abundance of SK2 at the sarcolemma was larger in cAF versus Ctl in both tissue-slices and cardiomyocytes. Latrunculin-A and primaquine (anterograde and retrograde protein-trafficking inhibitors) eliminated the differences in SK2 membrane levels and I-SK between Ctl- and cAF-cardiomyocytes. In addition, the phosphatase-inhibitor okadaic acid reduced I-SK amplitude and abolished the difference between Ctl- and cAF-cardiomyocytes, indicating that reduced calmodulin-Thr80 phosphorylation due to increased protein phosphatase-2A levels in the SK-channel complex likely contribute to the greater I-SK in cAF-cardiomyocytes. Finally, rapid electrical activation (5 Hz, 10 minutes) of Ctl-cardiomyocytes promoted SK2 membrane-localization, increased I-SK and reduced action potential duration, effects greatly attenuated by apamin. Latrunculin-A or primaquine prevented the 5-Hz-induced I-SK-upregulation. Conclusions:I-SK is upregulated in patients with cAF due to enhanced channel function, mediated by phosphatase-2A-dependent calmodulin-Thr80 dephosphorylation and tachycardia-dependent enhanced trafficking and targeting of SK-channel subunits to the sarcolemma. The observed AF-associated increases in I-SK, which promote reentry-stabilizing action potential duration shortening, suggest an important role for SK-channels in AF auto-promotion and provide a rationale for pursuing the antiarrhythmic effects of SK-channel inhibition in humans.

KW - actinin

KW - apamin

KW - atrial fibrillation

KW - atrial remodeling

KW - calmodulin

KW - protein phosphatase-2A

KW - protein transport

KW - CA2+-ACTIVATED K+ CHANNELS

KW - ACTIVATED POTASSIUM CHANNELS

KW - SMALL-CONDUCTANCE

KW - CA2+ LEAK

KW - PROTEIN

KW - EXPRESSION

KW - MECHANISMS

KW - ELECTROPHYSIOLOGY

KW - REFRACTORINESS

KW - ALPHA-ACTININ2

U2 - 10.1161/CIRCRESAHA.122.321858

DO - 10.1161/CIRCRESAHA.122.321858

M3 - Article

C2 - 36927079

SN - 0009-7330

VL - 132

SP - E116-E133

JO - Circulation Research

JF - Circulation Research

IS - 9

ER -