Voltage-gated K+ (Kv) currents are differentially distributed across the left ventricular wall. Kv4 currents are larger in left ventricular epicardial (EPI) cells than in endocardial (ENDO) cells. This non-uniform distribution of Kv4 channel function is essential for normal myocardial repolarization. We recently reported that variations in [Ca2+]i are transduced into changes in Kv4 expression through the activation of the Ca2+-sensitive phosphatase calcineurin and the transcription factor NFATc3. This led to our discovery that differential [Ca2+]i/calcineurin/NFATc3 signaling across the left ventricular free wall underlies transmural variations in Kv4 expression. However, the mechanisms underlying regional differences in [Ca2+]j, calcineurin, and NFATc3 signaling are poorly understood. The work proposed in this application employs a series of novel techniques and approaches developed by our group to address these important issues. Our preliminary data suggest that the proposed experiments are not only feasible but will provide new fundamental information regarding Kv channel regulation in the heart. The proposed work addresses three specific hypotheses. First, we will test the hypothesis that regional variations in [Ca2+]j underlie heterogeneous calcineurin activity in the ventricle. Second, we will test the hypothesis that local and global [Ca2+]i signals modulate NFAT translocation and gene expression in ventricular myocytes. We will then use these data to determine how variations in [Ca2+]j signals between ENDO and EPI cells lead to regional differences in NFAT activity. Finally, we will test the hypothesis that calcineurin/NFATc3 signaling is essential for maintaining Kv current heterogeneity in the ventricle. Taken together, this work will provide the first integrated view of calcium signaling, excitability, and contractility in the heart and significantly enhance our understanding of the basic mechanisms, which regulate Kv channel function in health and disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL085686-04
Application #
7787476
Study Section
Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
Program Officer
Wang, Lan-Hsiang
Project Start
2007-04-20
Project End
2012-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
4
Fiscal Year
2010
Total Cost
$390,000
Indirect Cost
Name
University of Washington
Department
Physiology
Type
Schools of Medicine
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
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Gentil, Benoit J; O'Ferrall, Erin; Chalk, Colin et al. (2017) A New Mutation in FIG4 Causes a Severe Form of CMT4J Involving TRPV4 in the Pathogenic Cascade. J Neuropathol Exp Neurol 76:789-799
Nieves-Cintrón, Madeline; Hirenallur-Shanthappa, Dinesh; Nygren, Patrick J et al. (2016) AKAP150 participates in calcineurin/NFAT activation during the down-regulation of voltage-gated K(+) currents in ventricular myocytes following myocardial infarction. Cell Signal 28:733-40
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Drum, Benjamin M L; Santana, Luis F (2015) The long and winding road home: how junctin and triadin find their way to the junctional SR. J Mol Cell Cardiol 81:15-7
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Drum, Benjamin M L; Dixon, Rose E; Yuan, Can et al. (2014) Cellular mechanisms of ventricular arrhythmias in a mouse model of Timothy syndrome (long QT syndrome 8). J Mol Cell Cardiol 66:63-71

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