Defects in ankyrin-based membrane protein targeting pathways underlie atrial fibrillation

Background-: Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting >2 million patients in the United States alone. Despite decades of research, surprisingly little is known regarding the molecular pathways underlying the pathogenesis of AF. ANK2 encodes ankyrin-B, a multifunctional adapter molecule implicated in membrane targeting of ion channels, transporters, and signaling molecules in excitable cells. Methods and Results-: In the present study, we report early-onset AF in patients harboring loss-of-function mutations in ANK2. In mice, we show that ankyrin-B deficiency results in atrial electrophysiological dysfunction and increased susceptibility to AF. Moreover, ankyrin-B^+/- atrial myocytes display shortened action potentials, consistent with human AF. Ankyrin-B is expressed in atrial myocytes, and we demonstrate its requirement for the membrane targeting and function of a subgroup of voltage-gated Ca²⁺ channels (Ca _v1.3) responsible for low voltage-activated L-type Ca²⁺ current. Ankyrin-B is associated directly with Ca_v1.3, and this interaction is regulated by a short, highly conserved motif specific to Ca _v1.3. Moreover, loss of ankyrin-B in atrial myocytes results in decreased Ca_v1.3 expression, membrane localization, and function sufficient to produce shortened atrial action potentials and arrhythmias. Finally, we demonstrate reduced ankyrin-B expression in atrial samples of patients with documented AF, further supporting an association between ankyrin-B and AF. Conclusions-: These findings support that reduced ankyrin-B expression or mutations in ANK2 are associated with AF. Additionally, our data demonstrate a novel pathway for ankyrin-B-dependent regulation of Ca_v1.3 channel membrane targeting and regulation in atrial myocytes.