RT Journal Article SR Electronic T1 Piezo1 and BKCa channels in human atrial fibroblasts: interplay and remodelling in atrial fibrillation JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.01.21.427388 DO 10.1101/2021.01.21.427388 A1 Dorothee Jakob A1 Alexander Klesen A1 Benoit Allegrini A1 Elisa Darkow A1 Diana Aria A1 Ramona Emig A1 Ana Simon Chica A1 Eva A. Rog-Zielinska A1 Tim Guth A1 Friedhelm Beyersdorf A1 Fabian A. Kari A1 Susanne Proksch A1 Stéphane N. Hatem A1 Matthias Karck A1 Stephan R Künzel A1 Hélène Guizouarn A1 Constanze Schmidt A1 Peter Kohl A1 Ursula Ravens A1 Rémi Peyronnet YR 2021 UL http://biorxiv.org/content/early/2021/01/21/2021.01.21.427388.abstract AB Aims Atrial Fibrillation (AF) is an arrhythmia of increasing prevalence in the aging population of developed countries. One of the important indicators of AF is sustained atrial dilatation, highlighting the importance of mechanical overload in the pathophysiology of AF. The mechanisms by which atrial cells, including fibroblasts, sense and react to changing mechanical forces, are not fully elucidated. Here, we characterise stretch-activated ion channels (SAC) in human atrial fibroblasts and changes in SAC-presence and -activity associated with AF.Methods and Results Using primary cultures of human atrial fibroblasts, isolated from patients in sinus rhythm or sustained AF, we combine electrophysiological, molecular and pharmacological tools to identify SAC. Two electrophysiological SAC-signatures were detected, indicative of cation-nonselective and potassium-selective channels. Using siRNA-mediated knockdown, we identified the nonselective SAC as Piezo1. Biophysical properties of the potassium-selective channel, its sensitivity to calcium, paxilline and iberiotoxin (blockers), and NS11021 (activator), indicated presence of calcium-dependent ‘big potassium channels’, BKCa. In cells from AF patients, Piezo1 activity and mRNA expression levels were higher than in cells from sinus rhythm patients, while BKCa activity (but not expression) was downregulated. Both Piezo1-knockdown and removal of extracellular calcium from the patch pipette resulted in a significant reduction of BKCa current during stretch. No co-immunoprecipitation of Piezo1 and BKCa was detected.Conclusions Human atrial fibroblasts contain at least two types of ion channels that are activated during stretch: Piezo1 and BKCa. While Piezo1 is directly stretch-activated, the increase in BKCa activity during mechanical stimulation appears to be mainly secondary to calcium influx via SAC such as Piezo1. During sustained AF, Piezo1 is increased, while BKCa activity is reduced, highlighting differential regulation of both channels. Our data support the presence and interplay of Piezo1 and BKCa in human atrial fibroblasts in the absence of physical interactions between the two channel proteins.Competing Interest StatementThe authors have declared no competing interest.