This proposal focuses on the mechanisms and electrophysiological consequences of the molecular interactions between the inward rectifier potassium channel protein Kir2.1 and the ?ubunit of the major cardiac sodium channel NaV1.5. Our preliminary results strongly suggest that NaV1.5 and Kir2.1 modulate each other's surface expression and function through their respective PDZ binding domains within a macromolecular complex to control cardiac excitability. Such a dynamic reciprocity is post-translational, involving, at least in part, mutual regulation of trafficking and targeting of both channel proteins at common membrane compartments, as well as internalization. We focus on inheritable mutations that are known to disrupt trafficking of NaV1.5 (Brugada Syndrome, BS) or Kir2.1 (Andersen-Tawil Syndrome, ATS). We surmise that a mutation that disrupts the expression of one channel protein type (e.g., NaV1.5) will also affect the other type (e.g., Kir2.1 by disturbing the common macromolecular complex through which they interact, thus contributing to both the electrophysiological phenotype and arrhythmogenic potential. We will test the following three major hypotheses: 1) NaV1.5 and Kir2.1 protein channels undergo PDZ-domain mediated interactions with common partners in a macromolecular complex that controls their membrane stability; 2) macromolecular complex formation affects anterograde and/or retrograde trafficking of Kir2.1 and NaV1.5; and 3) human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CMs) expressing either ATS or BS mutations that affect protein trafficking will show reduced excitability reflecting altered expression of both channel proteins, which should contribute strongly to the inherited arrhythmia phenotype. We propose to combine proteomics (e.g., protein purification, yeast two-hybrid assay and interaction domain mapping) and genetic (e.g., mutagenesis and silencing) tools, confocal microscopy, live cell imaging, fluorescence recovery after photobleaching, patch clamping, optical mapping, gene transfer and silencing in heterologous systems, and in single, highly mature ventricular-like hiPSC-CMs and hiPSC-CM monolayers. We will also conduct computer simulations to enable the virtual dissection and interpretation of the electrophysiological and arrhythmogenic changes resulting from NaV1.5-Kir2.1 interactions and their mutants in a macromolecular complex.

Public Health Relevance

The work proposed has strong implications for understanding the regulation of cardiac ion channels in health, as well as in heart failure and acquired and inheritable ion channel diseases. Posttranslational modifications and protein-protein interactions in macromolecular complexes may play critical roles in ion channel dysfunction and life-threatening arrhythmias, and may great potential to improved medical care.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
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Krull, Holly
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University of Michigan Ann Arbor
Internal Medicine/Medicine
Schools of Medicine
Ann Arbor
United States
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Ponce-Balbuena, Daniela; Guerrero-Serna, Guadalupe; Valdivia, Carmen R et al. (2018) Cardiac Kir2.1 and NaV1.5 Channels Traffic Together to the Sarcolemma to Control Excitability. Circ Res 122:1501-1516
Takemoto, Yoshio; Slough, Diana P; Meinke, Gretchen et al. (2018) Structural basis for the antiarrhythmic blockade of a potassium channel with a small molecule. FASEB J 32:1778-1793
Pérez-Hernández, Marta; Matamoros, Marcos; Alfayate, Silvia et al. (2018) Brugada syndrome trafficking-defective Nav1.5 channels can trap cardiac Kir2.1/2.2 channels. JCI Insight 3:
Calvo, David; Filgueiras-Rama, David; Jalife, José (2018) Mechanisms and Drug Development in Atrial Fibrillation. Pharmacol Rev 70:505-525
Goldstein, Daniel R; Jalife, José (2017) Synergistic Research Between the Center of Arrhythmia Research and the Michigan Biology of Cardiovascular Aging at the University of Michigan. Circ Res 121:1221-1223
Filgueiras-Rama, David; Bogun, Frank; Pérez-Castellano, Nicasio et al. (2017) Selection of the Best of 2016 in Catheter Ablation. Rev Esp Cardiol (Engl Ed) 70:302-303
Kaur, Kuljeet; Jalife, José (2017) Is TGF-?1 (Transforming Growth Factor-?1) an Enabler of Myofibroblast-Cardiomyocyte Cross Talk? Circ Arrhythm Electrophysiol 10:e005289
Caballero, Ricardo; Utrilla, Raquel G; Amorós, Irene et al. (2017) Tbx20 controls the expression of the KCNH2 gene and of hERG channels. Proc Natl Acad Sci U S A 114:E416-E425
Takemoto, Yoshio; Ramirez, Rafael J; Kaur, Kuljeet et al. (2017) Eplerenone Reduces Atrial Fibrillation Burden Without Preventing Atrial Electrical Remodeling. J Am Coll Cardiol 70:2893-2905
Calvo, David; Filgueiras-Rama, David; Jalife, José (2017) Propagation of Sinus Waves in the Atrial Architecture: When Laminar Electrical Fluxes Turn Turbulent. Circ Arrhythm Electrophysiol 10:

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