Abstract
Short QT syndrome is a heritable arrhythmia disorder linked to sudden cardiac death. We recently identified that individuals with alternating hemiplegia of childhood (AHC), a rare neurodevelopmental disorder, can exhibit shortened corrected QT intervals and elevated risk for ventricular fibrillation. This is especially true for patients with AHC heterozygous for the recurrent ATP1A3-D801N variant, though the underlying cardiac mechanism remains unclear. We hypothesized that the D801N missense impairs Na+/K+-ATPase function, causing Ca2+ overload, shortened action potential duration (APD), and arrhythmias. Using in silico modeling and patient-derived induced pluripotent stem cell cardiomyocytes (iPSC-CMsD801N), we observed shorter APD, elevated intracellular and sarcoplasmic reticulum Ca2+ levels, and delayed afterdepolarizations (DADs) compared with WT. Additionally, increased Ca²+ influx via the Na+/Ca2+ exchanger (NCX1) during depolarization was observed in iPSC-CMsD801N. Simulations and in vitro experiments suggest that reduced ATPase function accelerated inactivation of L-type Ca2+ channels. Pharmacologic inhibition of NCX1 with ORM-10103 normalized APD and reduced DADs. These findings support a Ca2+-mediated mechanism for arrhythmogenesis in ATP1A3-D801N carriers and identify NCX1 as a potential therapeutic target.
Authors
Minu-Tshyeto K. Bidzimou, Padmapriya Muralidharan, Zhushan Zhang, Danyal Raza, Daniel Needs, Bo Sun, Robin M. Perelli, Mary E. Moya-Mendez, P.K. Rakesh Manivannan, Arsen S. Hunanyan, Abbigail Helfer, Christine Q. Simmons, Alfred L. George Jr., Donald M. Bers, Nenad Bursac, Mohamad A. Mikati, Andrew P. Landstrom
Figure 4
iPSC-CMD801N have greater NCX1 Ca2+ influx at positive membrane potential.
