Coupling of the Na+/K+-ATPase to Ankyrin B controls Na+/Ca2+ exchanger activity in cardiomyocytes

Abstract

Aims Ankyrin B (AnkB) is an adaptor protein that assembles Na+/K+-ATPase (NKA) and Na+/Ca2+ exchanger (NCX) in the AnkB macromolecular complex. Loss-of-function mutations in AnkB cause the AnkB syndrome in humans, characterized by ventricular arrhythmias and sudden cardiac death. It is unclear to what extent NKA binding to AnkB allows regulation of local Na+ and Ca2+ domains and hence NCX activity. Methods and results To investigate the role of NKA binding to AnkB in cardiomyocytes, we synthesized a disruptor peptide (MAB peptide) and its AnkB binding ability was verified by pulldown experiments. As opposed to control, the correlation between NKA and NCX currents was abolished in adult rat ventricular myocytes dialyzed with MAB peptide, as well as in cardiomyocytes from AnkB+/− mice. Disruption of NKA from AnkB (with MAB peptide) increased NCX-sensed cytosolic Na+ concentration, reduced Ca2+ extrusion through NCX, and increased frequency of Ca2+ sparks and Ca2+ waves without concomitant increase in Ca2+ transient amplitude or SR Ca2+ load, suggesting an effect in local Ca2+ domains. Selective inhibition of the NKAα2 isoform abolished both the correlation between NKA and NCX currents and the increased rate of Ca2+ sparks and waves following NKA/AnkB disruption, suggesting that an AnkB/NKAα2/NCX domain controls Ca2+ fluxes in cardiomyocytes. Conclusion NKA binding to AnkB allows ion regulation in a local domain, and acute disruption of the NKA/AnkB interaction using disruptor peptides lead to increased rate of Ca2+ sparks and waves. The functional effects were mediated through the NKAα2 isoform. Disruption of the AnkB/NKA/NCX domain could be an important pathophysiological mechanism in the AnkB syndrome.

Mechanisms and Alterations of Cardiac Ion Channels Leading to Disease: Role of Ankyrin-B in Cardiac Function

“…erythrocytes [1], myelinated axons [10], striated muscle [11] ubiquitously expressed, cardiomyocytes (T-tubules, SR, plasma membrane) [12], neurons [8] ubiquitously expressed, neurons (AIS, and nodes of Ranvier) [13], cardiomyocytes (intercalated disc) [14] Examples of Binding Partners CD44 [15], NKA [16], Rh type A glycoprotein [17], obscurin [11] PP2A [12,13], NCX [12], NKA [18], Kir6.2 [12,13], Ca V 1.3 [19], βII-spectrin [20] Na V 1.6, βIV-spectrin, L1CAMs [1,21,22], plakophilin-2 [23] Na V 1.5 [14] Isoforms sAnk1.5, 1.6, 1.7, and 1.9 [11] AnkB-188 and AnkB-212 [24]. Giant AnkB (440-kD) Giant AnkG (480-kD) [25] Disease associated with variants hereditary spherocytosis [26] Ankyrin B syndrome: SCD, SND, AF, LQTS, VT, bradycardia, syncope [12], ARVC [27] Brugada syndrome [12], dilated cardiomyopathy [28], cognitive disabilities [29] SR = sarcoplasmic reticulum, AIS = axon initial segments, NKA = Na + /K + ATPase, PP2A = protein phosphatase 2A, NCX = Na + /Ca 2+ exchanger, Kir6.2 = inward rectifier potassium channel, Ca V 1.3 = voltage-gated calcium channel, L1CAMs = L1 family of neural cell adhesion molecules, SCD = sudden cardiac death, SND = sinus node disease, AF = atrial fibrillation, LQTS = long QT syndrome, VT = ventricular tachycardia, ARVC = arrhythmogenic right ventricular cardiomyopathy.…”

“…Canonical AnkB is an adaptor protein that acts as a pivotal regulator in the localization and organization of ion channels, structural proteins, signaling molecules, and adaptor proteins [40,41]. Deficiency in AnkB results in mislocalization and altered expression of multiple membrane and cytoskeletal proteins, including NCX [12], NKA [18], ATP-sensitive inward rectifier K + channel (Kir6.2) [13], voltage-gated calcium channel (Ca V 1.3) [19], and βII-spectrin [20], causing ion imbalance and dysregulation of cellular signaling [18].…”

Integrative Proteomic and Metabolomic Analysis Reveals Metabolic Phenotype in Mice With Cardiac-Specific Deletion of Natriuretic Peptide Receptor A

“…It is a key enzyme involved in energy metabolism, and it catalyzes the synthesis of ATP from substrates to provide cells with the energy required to perform various life activities (nerve conduction, muscle contraction, material transport, etc.) (42). Given the critical role of COX in regulating oxygen consumption and ATP production, we speculate that NPRA may play an important role in myocardial energy metabolism by regulating the role of cox and then affecting myocardial mitochondrial function.…”

Meta-analysis of Transcriptomic Data Reveals Pathophysiological Modules Involved with Atrial Fibrillation

“…In cardiomyocytes, ankirin-B appears to organize a complex involving the a 2 isoform of the Na + /K + pump (NKA) and the Na + /Ca 2+ exchanger (NCX) in a microenvironment in which NCX activity is regulated by NKA. In this context, the loss of function or low expression of ankirin-B disturbs the regulation and localization in the membrane of these exchangers, increasing the rates of Ca 2+ waves associated with SR leakage via ryanodine receptor (RyR) (Skogestad et al 2020), an important mechanism that causes DADs (Shiferaw, Aistrup, and Wasserstrom 2012). The increase in these rates is probably associated with hyperphosphorylation of RyRs by Ca 2+ / calmodulin-dependent protein kinase II (CaMKII), whose activity is increased due to the greater [Ca 2+ ] resulting from the altered location and functioning of NKA/NCX/ANK2 complex (Popescu et al 2016) in the gap between the plasma membrane and SR.…”