Hypertrophic cardiomyopathy (HCM) is the most-common inherited form of heart disease, characterized by thickening of the left ventricular wall, contractile dysfunction, and potentially fatal arrhythmias. There is extensive evidence that defects in excitation-contraction coupling (ECC) contribute to the pathogenesis of both cardiomyopathy and arrhythmias. Specialized membrane junctions known as 'junctional membrane complexes'(JMC) are important subcellular structures in L-type Ca channels (LTCC) on the plasmalemma communicate with ryanodine receptors (RyR2) on the sarcoplasmic reticulum (SR) to initiate contraction. Little is known about the proteins that govern proper subcellular targeting of Ca channels within JMCs, but junctophilin-2 (JPH2) has been identified as a key candidate. In humans, missense mutations in JPH2 cause HCM, although the molecular mechanisms remain unresolved. We have recently demonstrated that JPH2 also binds to and modulates RyR2 channels in the JMC, but the exact protein domains involved in these interactions are still unknown. Moreover, reduced expression of JPH2 has been reported in patients with HCM and animal models of heart failure, but it is unclear whether loss of JPH2 is directly linked to impaired contractility and/or arrhythmias in failing hearts. We have generated several mouse models with HCM-linked JPH2 mutations or with increased/decreased JPH2 expression levels in the heart. The long-term goal of this project is to define the molecular mechanisms by which JPH2 and associated molecules regulate JMC integrity and EC coupling in normal hearts, and how aberrant JPH2 function causes HCM, heart failure, and arrhythmias. Our overall hypothesis is that in normal hearts JPH2 is required for JMC integrity and the regulation of Ca channels therein, whereas loss of JPH2 function due to downregulation or mutation causes cardiomyopathy, heart failure and arrhythmias. To test this hypothesis, we propose to:
In Aim 1, determine the role of JPH2 in organizing key Ca handling proteins within the JMC. - In Aim 2, unravel the mechanisms by which genetic JPH2 variants cause HCM. - In Aim 3, determine if JPH2 downregulation is the cause of loss of TTs/JMCs in heart failure.

Public Health Relevance

The proposed work will study how junctophilin-2 (JPH2) regulates the formation of calcium release units and the fundamental process of excitation-contraction coupling in the heart. Moreover, we will study how JPH2 deficiency or inherited mutations in JPH2 cause cardiomyopathy and life-threatening cardiac arrhythmias.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
3R01HL117641-01A1S1
Application #
8901684
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Boineau, Robin
Project Start
2014-04-01
Project End
2018-03-31
Budget Start
2014-09-15
Budget End
2015-03-31
Support Year
1
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Baylor College of Medicine
Department
Physiology
Type
Schools of Medicine
DUNS #
City
Houston
State
TX
Country
United States
Zip Code
77030
Lezcano, N; Mariángelo, J I E; Vittone, L et al. (2018) Early effects of Epac depend on the fine-tuning of the sarcoplasmic reticulum Ca2+ handling in cardiomyocytes. J Mol Cell Cardiol 114:1-9
Yao, Chunxia; Veleva, Tina; Scott Jr, Larry et al. (2018) Enhanced Cardiomyocyte NLRP3 Inflammasome Signaling Promotes Atrial Fibrillation. Circulation 138:2227-2242
Ni, Li; Scott Jr, Larry; Campbell, Hannah M et al. (2018) Atrial-Specific Gene Delivery Using an Adeno-Associated Viral Vector. Circ Res :
Auguste, Gaelle; Gurha, Priyatansh; Lombardi, Raffaella et al. (2018) Suppression of Activated FOXO Transcription Factors in the Heart Prolongs Survival in a Mouse Model of Laminopathies. Circ Res 122:678-692
Dobrev, Dobromir; Wehrens, Xander H T (2018) Mouse Models of Cardiac Arrhythmias. Circ Res 123:332-334
Wang, Qiongling; Quick, Ann P; Cao, Shuyi et al. (2018) Oxidized CaMKII (Ca2+/Calmodulin-Dependent Protein Kinase II) Is Essential for Ventricular Arrhythmia in a Mouse Model of Duchenne Muscular Dystrophy. Circ Arrhythm Electrophysiol 11:e005682
Wehrens, Xander H T (2018) Unraveling the Mechanisms by Which Calpain Inhibition Prevents Heart Failure Development. JACC Basic Transl Sci 3:518-520
Chiang, David Y; Alsina, Katherina M; Corradini, Eleonora et al. (2018) Rearrangement of the Protein Phosphatase 1 Interactome During Heart Failure Progression. Circulation 138:1569-1581
Klipp, Robert C; Li, Na; Wang, Qiongling et al. (2018) EL20, a potent antiarrhythmic compound, selectively inhibits calmodulin-deficient ryanodine receptor type 2. Heart Rhythm 15:578-586
Pan, Xiaolu; Philippen, Leonne; Lahiri, Satadru K et al. (2018) In Vivo Ryr2 Editing Corrects Catecholaminergic Polymorphic Ventricular Tachycardia. Circ Res 123:953-963

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