RESUMEN
[Figure: see text].
Asunto(s)
Arritmias Cardíacas/metabolismo , AMP Cíclico/metabolismo , Microscopía Fluorescente , Imagen Molecular , Miocitos Cardíacos/metabolismo , Receptores Adrenérgicos beta 2/metabolismo , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Anciano , Animales , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatología , Técnicas Biosensibles , Señalización del Calcio , Modelos Animales de Enfermedad , Femenino , Transferencia Resonante de Energía de Fluorescencia , Factores de Intercambio de Guanina Nucleótido/genética , Factores de Intercambio de Guanina Nucleótido/metabolismo , Humanos , Preparación de Corazón Aislado , Masculino , Ratones Transgénicos , Persona de Mediana Edad , Hidrolasas Diéster Fosfóricas/metabolismo , Fosforilación , Canal Liberador de Calcio Receptor de Rianodina/genética , Factores de TiempoRESUMEN
The tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b/PEX5R) is an interaction partner and auxiliary subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are key for rhythm generation in the brain and in the heart. Since TRIP8b is expressed in central neurons but not in cardiomyocytes, the TRIP8b-HCN interaction has been studied intensely in the brain, but is deemed irrelevant in the cardiac conduction system. Still, to date, TRIP8b has not been studied in the intrinsic cardiac nervous system (ICNS), a neuronal network located within epicardial fat pads. In vitro electrophysiological studies revealed that TRIP8b-deficient mouse hearts exhibit increased atrial refractory and atrioventricular nodal refractory periods, compared to hearts of wild-type littermates. Meanwhile, heart rate, sino-nodal recovery time, and ventricular refractory period did not differ between genotypes. Trip8b mRNA was detected in the ICNS by quantitative polymerase chain reaction. RNAscope in situ hybridization confirmed Trip8b localization in neuronal somata and nerve fibers. Additionally, we found a very low amount of mRNAs in the sinus node and atrioventricular node, most likely attributable to the delicate fibers innervating the conduction system. In contrast, TRIP8b protein was not detectable. Our data suggest that TRIP8b in the ICNS may play a role in the modulation of atrial electrophysiology beyond HCN-mediated sino-nodal control of the heart.