Abstract 18987: Domain Specific Interaction of Kir2.2 and Cav3: Implications for Atrial Fibrillation
Introduction: In human ventricle Kir2.1 comprises the major component of IK1, but the Kir2.2 isoform dominates in the atria. Thus Kir2.2 regulation may have specific impact in atrial arrhythmias such as atrial fibrillation. Caveolin-3 (Cav3) forms caveolar rafts and plays a key role in assembling macromolecular signaling complexes for cardiac ion channels. Cav3 is implicated in ion channel misplacement in heart failure leading to atrial fibrillation. In our previous report, Kir2.1 and Cav3 associate and LQT9 Cav3 mutations decreased IK1 density by ~60% when co-expressed in heterologous expression systems.
Hypothesis: Kir2.2 is also part of the Cav3 macromolecular signaling complex and that LQT9 causing Cav3 mutation can affect the function of Kir2.2 channels.
Methods: Co-immunoprecipitation(Co-IP), cellular electrophysiology, and On-Cell Western (OCW) blotting techniques were used.
Results: Kir2.2 and Cav3 Co-IP. To investigate, which domain of Cav3 associates with Kir2.2, we separated the N-terminal (NT), Scaffolding (Scaf), Membrane (Mem) and C-terminal (CT) domains of Cav3 and transfected them into HEK cells with Kir2.2. Both the Scaf and Mem domains, but not the NT or CT domains of Cav3 Co-IP with Kir2.2 (Fig. 1). F97C is a Membrane domain mutation of Cav3, causing LQT9. HEK293 cells were co-transfected with Kir2.2 and Cav3-WT or Cav3-F97C constructs. With Cav3-F97C but not Cav3-WT, we found a 50% decrease in peak inward current density at -100 mV and about 75% decrease in peak outward current density at -40 mV. By OCW, we found a ~60% decrease in cell surface expression of Kir2.2 in the presence of Cav3-F97C but not Cav3-WT.
Conclusions: Our experiments suggest that two domains of Cav3 associates with Kir2.2 and Cav3-F97C mutation reduces the current density and cell surface expression of Kir2 channels compared to Cav3-WT. Chamber specificity of Kir2.2 suggests unique vulnerability of this channel for atrial arrhythmias in heart failure or LQT9.
Author Disclosures: R. Vaidyanathan: None. H. Van Ert: None. S. Esch: None. J. Warden: None. S. Abozeid: None. R.C. Balijepalli: None. L.L. Eckhardt: None.
- © 2016 by American Heart Association, Inc.