Differential contribution of HCN1 and HCN4 to the synchronisation of sinoatrial pacemaker cells

Hennis, K.; Piantoni, C.; Orabona, M.; Pham, L.; Schaenzler, M.; Auerbach, N.; Hoerzing, M.; Wu, Y.; Roetzer, R.; Kohlrautz, A.; Feldmann, C.; Pisfil, M. G.; Kruck, D.; Rilling, J.; Averbeck, B.; Nikolaev, V. O.; Biel, M.; Leibold, C.; Fenske, S.; Wahl-Schott, C.

doi:10.64898/2025.12.16.694405

Home/Archive/bioRxiv

bioRxiv · 10.64898/2025.12.16.694405

Differential contribution of HCN1 and HCN4 to the synchronisation of sinoatrial pacemaker cells

View original source ↗Export metadata ↓

Abstract

The hearts ability to beat with high precision, with a regular and steady rhythm relies on the synchronised activity of pacemaker cells in the sinoatrial node (SAN), which communicate with one another through gap junctions. This process ensures that electrical impulses are organised and reach a critical mass to ignite the electrical activity of the surrounding atrial tissue and trigger the regular heartbeat. HypothesisWe hypothesise that hyperpolarisation-activated, cyclic nucleotide-gated (HCN) channels play a pivotal role in maintaining this synchronisation process. This idea aligns with the well-established role of HCN channels in stabilising the membrane potential in the voltage range of the slow diastolic depolarisation, counteracting voltage fluctuations and effectively filtering out variations in the beating rate from neighbouring cells. AimWe focus on two specific HCN channel subtypes--HCN1 and HCN4--and their contributions to the rapid synchronisation of pacemaker cells, a phenomenon known as phasic entrainment. Using two HCN channel-mutant mouse models, we dissect the distinct roles of HCN1 and HCN4 in this process. MethodsWe employed patch-clamp electrophysiology to determine phase response curves (PRCs) to predict the ability of single cells to interact in the SAN. Using computer simulations, the behaviour of the SAN at the network level was determined. ResultsWe found that HCN1, but not HCN4, is essential for the fast synchronisation of pacemaker cells in the SAN and propose a mechanism by which HCN1 channels regulate this process. ConclusionThese findings highlight HCN1 as a critical component for ensuring the precise and rapid coordination needed for synchronisation of the SAN, for a regular and consistent heartbeat. Translational perspectiveOur work provides essential insights into the cellular and molecular mechanisms governing SAN function and lays the groundwork for several clinically relevant applications. Understanding how If blockers may affect heart rate and rhythm stability is crucial for assessing potential side effects of current and future subtype-specific HCN channel inhibitors. Moreover, our findings could support new diagnostic strategies for detecting patients at risk of SAN dysfunction. Ultimately, these findings pave the way for innovative therapeutic approaches, including targeted channel modulation and future cell or gene therapies to restore pacemaker stability.

Explore related subjects

physiology Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Hennis, K., Piantoni, C., Orabona, M., Pham, L., Schaenzler, M., Auerbach, N., Hoerzing, M., Wu, Y., Roetzer, R., Kohlrautz, A., Feldmann, C., Pisfil, M. G., Kruck, D., Rilling, J., Averbeck, B., Nikolaev, V. O., Biel, M., Leibold, C., Fenske, S., Wahl-Schott, C.. 2025-12-18. Differential contribution of HCN1 and HCN4 to the synchronisation of sinoatrial pacemaker cells. https://doi.org/10.64898/2025.12.16.694405

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Thoracoabdominal pressure transmission during prone and supine cardiopulmonary resuscitation in fresh-frozen human cadavers

Background: Prone cardiopulmonary resuscitation (CPR) may be necessary when turning a prone patient supine would delay chest compressions. Although prone compressions can generate arterial pressures comparable with or greater than supine CPR, the pathway of pressure transmission is uncertain. We examined synchronized intrathoracic, intra-abdominal, and central arterial pressures in both supine and prone positions. Methods: Two thawed fresh-frozen adult cadavers underwent three, 2-minute mechanical CPR trials per position in a counterbalanced crossover sequence. Solid-state catheters recorded pleural, peritoneal, and central arterial pressures simultaneously. Trial-level outcomes included peak pressure, mean pressure, pressure-time area, and the mean peritoneal-to-pleural pressure gradient. Exploratory fixed-effects models included position, cadaver, and their interaction. Results: Prone CPR increased peak intrathoracic pressure by 7.04 mmHg, peak intra-abdominal pressure by 21.69 mmHg, and peak arterial pressure by 15.40 mmHg. Mean intra-abdominal and arterial pressures increased by 16.22 and 9.90 mmHg, respectively. The mean peritoneal-to-pleural gradient reversed direction from -8.46 mmHg supine to 4.85 mmHg prone. Intrathoracic pressure-time area increased 3.4-fold, from 1.62 to 5.46 mmHg{middle dot}s, and arterial pressure-time area increased 2.2-fold, from 2.96 to 6.42 mmHg{middle dot}s. Conclusions: Compared to supine, prone mechanical CPR generated higher arterial pressures and reversed the pressure relationship across the thoracoabdominal boundary in both cadavers. Higher abdominal pressure coincided with a larger intrathoracic pressure-time area, a pattern compatible with reduced caudal pressure dissipation.

physiology↗

bioRxiv2026

Hypothalamic Farnesoid X Receptor deficiency alters energy balance by modulating hepatic glucose production and adipose tissue metabolism through central insulin signaling.

Objectives: The bile acid nuclear receptor Farnesoid X Receptor (FXR, NR1H4) is a major regulator of metabolism and energy homeostasis in peripheral organs. It modulates bile acid, glucose, and lipid metabolism, as well as fat mass and body weight. However, FXR is also expressed in the brain, particularly in the hypothalamus, a key center for the regulation of energy homeostasis. Although one study has demonstrated a role for brain FXR activation in energy balance, its specific hypothalamic role is still unknown. Here, we examined the role of FXR in the mediobasal hypothalamus in the regulation of energy balance. Methods: We used a genetic approach combined with metabolic phenotyping to determine the effect of FXR invalidation in the mediobasal hypothalamus on metabolic parameters involved in the central regulation of energy homeostasis. Results: Our results demonstrate that hypothalamic FXR deficiency induces a positive energy balance, resulting in a reduction in energy expenditure due to alterations in glucose metabolism accompanied by structural changes in white adipose tissues. Conclusion: This study uncovers a previously unrecognized role for hypothalamic FXR in the central homeostatic control of energy balance, providing new insights into its contribution to peripheral glucose metabolism and adipose tissue structural remodeling.

physiology↗

bioRxiv2026

Rad and Phospholamban are Key Drivers of the Ventricular Adrenergic Response and Stress-Induced Arrhythmia

The adrenergic response is a fundamental mechanism that regulates heart rate (chronotropy), cardiac contractility (inotropy) and relaxation (lusitropy). Adrenergic stress is also a recognized trigger of arrhythmia in disease. Yet, our understanding of the underlying molecular basis remains incomplete. Protein kinase A (PKA) and the calcium/calmodulin-dependent kinase II (CaMKII) phosphorylate multiple targets proposed to participate in the adrenergic response, including the GTP-binding protein Rad, phospholamban (PLB) and ryanodine receptor 2 (RyR2). Here we demonstrate that phosphorylation of both Rad and PLB is necessary for inotropy and lusitropy. We show that changes in cardiac contractility and relaxation are primarily dependent on intracellular calcium handling. Finally, we report that Rad and PLB control stress-induced arrhythmogenesis, despite the phosphorylation of other pro-arrhythmic targets. We have identified the essential molecular components of the adrenergic response, resolving a long-standing debate in cardiac excitation-contraction coupling and refining current models of sympathetic regulation in health and disease.

physiology↗