TY - JOUR
T1 - HCN4 current during human sinoatrial node-like action potentials
AU - Hoekstra, Maaike
AU - van Ginneken, Antoni C. G.
AU - Wilders, Ronald
AU - Verkerk, Arie O.
N1 - Funding Information: We thank Marie-Jos? T.H. Goumans (Department of Cell and Chemical Biology, Leiden UMC, Leiden, The Netherlands) for providing the CMPCs, Geert J.J. Boink (Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, The Netherlands) for providing the lentiviral HCN4-GFP and GFP vectors, and Berend de Jonge (Department of Medical Biology, Amsterdam UMC, University of Amsterdam, The Netherlands) for technical assistance. Publisher Copyright: © 2021 The Authors
PY - 2021/11
Y1 - 2021/11
N2 - Background: Despite the many studies carried out over the past 40 years, the contribution of the HCN4 encoded hyperpolarization-activated ‘funny’ current (If) to pacemaker activity in the mammalian sinoatrial node (SAN), and the human SAN in particular, is still controversial and not fully established. Objective: To study the contribution of If to diastolic depolarization of human SAN cells and its dependence on heart rate, cAMP levels, and atrial load. Methods: HCN4 channels were expressed in human cardiac myocyte progenitor cells (CMPCs) and HCN4 currents assessed using perforated patch-clamp in traditional voltage clamp mode and during action potential clamp with human SAN-like action potential waveforms with 500–1500 ms cycle length, in absence or presence of forskolin to mimic β-adrenergic stimulation and a −15 mV command potential offset to mimic atrial load. Results: Forskolin significantly increased the fully-activated HCN4 current density at −140 mV by 14% and shifted the steady-state activation curve by +7.4 mV without affecting its slope. In addition, forskolin significantly accelerated current activation but slowed deactivation. The HCN4 current did not completely deactivate before the subsequent diastolic depolarization during action potential clamp. The amplitude of HCN4 current increased with increasing cycle length, was significantly larger in the presence of forskolin at all cycle lengths, and was significantly increased upon the negative offset to the command potential. Conclusions: If is active during a human SAN action potential waveform and its amplitude is modulated by heart rate, β-adrenergic stimulation, and diastolic voltage range, such that If is under delicate control.
AB - Background: Despite the many studies carried out over the past 40 years, the contribution of the HCN4 encoded hyperpolarization-activated ‘funny’ current (If) to pacemaker activity in the mammalian sinoatrial node (SAN), and the human SAN in particular, is still controversial and not fully established. Objective: To study the contribution of If to diastolic depolarization of human SAN cells and its dependence on heart rate, cAMP levels, and atrial load. Methods: HCN4 channels were expressed in human cardiac myocyte progenitor cells (CMPCs) and HCN4 currents assessed using perforated patch-clamp in traditional voltage clamp mode and during action potential clamp with human SAN-like action potential waveforms with 500–1500 ms cycle length, in absence or presence of forskolin to mimic β-adrenergic stimulation and a −15 mV command potential offset to mimic atrial load. Results: Forskolin significantly increased the fully-activated HCN4 current density at −140 mV by 14% and shifted the steady-state activation curve by +7.4 mV without affecting its slope. In addition, forskolin significantly accelerated current activation but slowed deactivation. The HCN4 current did not completely deactivate before the subsequent diastolic depolarization during action potential clamp. The amplitude of HCN4 current increased with increasing cycle length, was significantly larger in the presence of forskolin at all cycle lengths, and was significantly increased upon the negative offset to the command potential. Conclusions: If is active during a human SAN action potential waveform and its amplitude is modulated by heart rate, β-adrenergic stimulation, and diastolic voltage range, such that If is under delicate control.
KW - Action potential clamp
KW - Heart rate
KW - Human
KW - Hyperpolarization-activated current
KW - Sinoatrial node
KW - β-adrenergic stimulation
UR - http://www.scopus.com/inward/record.url?scp=85108558444&partnerID=8YFLogxK
U2 - https://doi.org/10.1016/j.pbiomolbio.2021.05.006
DO - https://doi.org/10.1016/j.pbiomolbio.2021.05.006
M3 - Article
C2 - 34153331
SN - 0079-6107
VL - 166
SP - 105
EP - 118
JO - Progress in biophysics and molecular biology
JF - Progress in biophysics and molecular biology
ER -