Transcriptional regulation of the TASK-1 potassium channel by ETV1 -Implications for atrial excitability

Abstract

BackgroundAtrial fibrillation (AF), the most common sustained arrhythmia, is driven by electrical and structural remodelling, including altered ion channel expression. The atrial-specific potassium channel TASK-1 regulates action potential duration (APD) and is differentially expressed in AF and left ventricular dysfunction, but the mechanisms controlling its expression are not well understood. ObjectiveThis study examines whether the transcription factor ETV1 regulates TASK-1 and contributes to atrial electrical remodelling. MethodsAtrial tissue from patients with and without AF was analysed to assess the relationship between ETV1 and TASK-1 (KCNK3) expression. In HL-1 cardiomyocyte-like cells and native fibroblasts, ETV1 activity was reduced using pharmacological inhibition or siRNA-mediated knockdown. TASK-1 expression, TASK-1 current, and APD at 90% repolarization were measured. Pacing experiments tested activity-dependent TASK-1 regulation. Direct transcriptional regulation was evaluated using ChIP-qPCR and ChIP-seq to detect ETV1 binding at the KCNK3 promoter. ResultsETV1 and TASK-1 levels were positively correlated in human atrial tissue. In HL-1 cells and fibroblasts, ETV1 inhibition or knockdown decreased TASK-1 expression and current and selectively prolonged APD90. Pacing-induced upregulation of TASK-1 was prevented by ETV1 inhibition, indicating a protective effect against pro-arrhythmic remodelling. ChIP-qPCR and ChIP-seq confirmed direct ETV1 binding to the KCNK3 promoter. ConclusionETV1 directly regulates TASK-1 expression and contributes to atrial electrical remodelling, identifying ETV1 as a potential upstream therapeutic target in AF. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/711402v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@3e5b25org.highwire.dtl.DTLVardef@1d1f909org.highwire.dtl.DTLVardef@34cf37org.highwire.dtl.DTLVardef@1105539_HPS_FORMAT_FIGEXP M_FIG C_FIG Translational perspectiveAtrial fibrillation is sustained by maladaptive electrical remodelling that remains insufficiently addressed by current rhythm-control therapies. Direct inhibition of individual ion channels has shown efficacy but is limited by phenotype dependence and proarrhythmic risk. The present data identify ETV1 as an upstream transcriptional regulator of the atrial-specific potassium channel TASK-1. Modulation of ETV1 reduced TASK-1 expression, prolonged atrial repolarisation, and prevented tachycardia-induced electrical remodelling in vitro. Targeting ETV1 may therefore represent a disease-modifying strategy that intervenes earlier in the remodelling cascade than conventional antiarrhythmic drugs. This approach could enable phenotype-guided therapy in atrial cardiomyopathy, particularly in patients with preserved ventricular function, and warrants validation in translational large-animal and clinical studies.