Biology subjects

Ponce-Balbuena, D.

Publications and source records attributed to Ponce-Balbuena, D..

4 recordsLinked to original sources

bioRxiv2026

RyR2-Mediated Ca2+ Leak Drives Progressive Arrhythmogenic Cardiomyopathy

Background Abnormal sarcoplasmic reticulum (SR) Ca2+ release through ryanodine receptor 2 (RyR2) is a well-established mechanism of ventricular arrhythmias. Whether persistent RyR2 dysfunction can also initiate the structural remodeling characteristic of arrhythmogenic cardiomyopathy (ACM) remains unknown. We tested the hypothesis that chronic RyR2-mediated Ca2+ leak is sufficient to couple electrical instability to progressive cardiomyopathy. Methods We generated a rabbit carrying the severe gain-of-function RyR2-V2475F mutation and characterized disease progression using longitudinal cardiac phenotyping, continuous electrocardiographic monitoring, cellular electrophysiology and Ca2+ imaging, histopathology, biochemical analyses, and single-nucleus RNA sequencing (snRNA-seq). Therapeutic potential was evaluated by continuous treatment with the selective RyR2 inhibitor ent-verticilide for two months. Results RyR2-V2475F rabbits developed spontaneous ventricular tachyarrhythmias, sudden cardiac death, and progressive right ventricular (RV)-dominant fibrofatty cardiomyopathy recapitulating major features of human ACM. Malignant ventricular arrhythmias preceded overt structural remodeling and were associated at the cellular level with early spontaneous Ca2+ release and early afterdepolarizations. Early disease was characterized by remodeling of excitation-contraction coupling with preserved SR Ca2+ load and contractile function despite RyR2 dysfunction; upon disease progression, these compensatory changes were accompanied by SR Ca2+ depletion, impaired RV contractility and reduced left ventricular filling. Single-nucleus transcriptomics identified early fibroblast expansion and predicted cardiomyocyte-centered paracrine signaling before advanced fibrofatty infiltration. Cardiomyocytes also exhibited an altered lipid-metabolic transcriptome and intracellular lipid accumulation, accompanied by enhanced mitochondrial Ca2+ uptake. Selective RyR2 inhibition markedly reduced ventricular tachycardia burden and preserved RV contraction and LV filling during disease progression. Conclusions Severe RyR2 gain-of-function can lead to both malignant ventricular arrhythmias and progressive arrhythmogenic cardiomyopathy in a large-animal model, establishing persistent intracellular Ca2+ dysregulation as a mechanistic link between electrical and structural heart disease. The ability of selective RyR2 inhibition to suppress arrhythmias and preserve cardiac function identifies RyR2 as a potentially actionable therapeutic target in arrhythmogenic cardiomyopathy.

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↗

bioRxiv2024

Paradoxical SERCA dysregulation contributes to atrial fibrillation in a model of diet-induced obesity

Obesity is a major risk factor for atrial fibrillation (AF) the most common serious cardiac arrhythmia, but the molecular mechanisms underlying diet-induced AF remain unclear. In this study, we subjected mice to a chronic high-fat diet and acute sympathetic activation ( two-hit model) to study the mechanisms by which diet-induced obesity promotes AF. Surface electrocardiography revealed that diet-induced obesity and sympathetic activation synergize during intracardiac tachypacing to induce AF. At the cellular level, diet-induced obesity and acute adrenergic stimulation facilitate the formation of delayed afterdepolarizations in atrial myocytes, implicating altered Ca2+ dynamics as the underlying cause of AF. We found that diet-induced obesity does not alter the expression of major Ca2+-handling proteins in atria, including the sarcoplasmic reticulum Ca2+-ATPase (SERCA), a major component of beat-to-beat Ca2+ cycling in the heart. Paradoxically, obesity reduces phospholamban phosphorylation, suggesting decreased SERCA activity, yet atrial myocytes from obese mice showed a significantly increased Ca2+ transient amplitude and SERCA-mediated Ca2+ uptake. Adrenergic stimulation further increases the Ca2+ transient amplitude but does not affect Ca2+ reuptake in atrial myocytes from obese mice. Transcriptomics analysis showed that a high-fat diet prompts upregulation of neuronatin, a protein that has been implicated in obesity and is known to stimulate SERCA activity. We propose a mechanism in which obesity primes SERCA for paradoxical activation, and adrenergic stimulation facilitates AF conversion through a Ca2+-induced Ca2+ release gain in atrial myocytes. Overall, this study links obesity, altered Ca2+ signaling, and AF, and targeting this mechanism may prove effective for treating obesity-induced AF.

physiology↗

bioRxiv2022

SNTA1 GeneRescues Ion Channel Function in Cardiomyocytes Derived from Induced Pluripotent Stem Cells Reprogrammed from Muscular Dystrophy Patients with Arrhythmias

Patients with cardiomyopathy of Duchenne Muscular Dystrophy (DMD) are at risk of developing life-threatening arrhythmias, but the mechanisms are unknown. We aimed to determine the role of cardiac ion channels controlling cardiac excitability in the mechanisms of arrhythmias in DMD patients. To test whether cardiac dystrophin mutations lead to defective NaV1.5-Kir2.1 channelosomes and arrhythmias, we generated iPSC-CMs from two hemizygous DMD males, a heterozygous female, and two unrelated controls. Two Patients had abnormal ECGs with frequent runs of ventricular tachycardia. iPSC-CMs from all DMD patients showed abnormal action potential profiles, slowed conduction velocities, and reduced sodium (INa) and inward rectifier potassium (IK1) currents. Membrane NaV1.5 and Kir2.1 protein levels were reduced in hemizygous DMD iPSC-CMs but not in heterozygous iPSC-CMs. Remarkably, transfecting just one component of the dystrophin protein complex (1-syntrophin) in hemizygous iPSC-CMs restored channelosome function, INa and IK1 densities and action potential profile. We provide the first demonstration that iPSC-CMs reprogrammed from skin fibroblasts of DMD patients with cardiomyopathy have a dysfunction of the NaV1.5-Kir2.1 channelosome, with consequent reduction of cardiac excitability and conduction. Altogether, iPSC-CMs from patients with DMD cardiomyopathy have a NaV1.5-Kir2.1 channelosome dysfunction, which can be rescued by the scaffolding protein 1-syntrophin to restore excitability.

cell biology↗