During a cardiac ventricular action potential (AP), a small Ca flux across the transverse tubule (TT) membrane activates ryanodine receptor (RyR) channels on the sarcoplasmic reticululum (SR), a process called Ca-induced Ca release (CICR). During diastole, single RyRs can also spontaneously open (albeit infrequently). When one does, the SR Ca released may trigger a localized bout of inter-RyR CICR (a Ca spark). Abnormally frequent or large sparks can evoke propagating Ca waves. By driving surface electrogenic Na-Ca exchange, waves may generate delayed afterdepolarizations (DADs). DADs can be life-threatening arrhythmogenic events and are observed in both catecholaminergic polymorphic ventricular tachycardia (CPVT) and heart failure (HF). A RyR DAD control nexus is diastolic inter-RyR CICR initiation, which is driven by an individual spontaneous RyR opening. The decisive opening produces a local cytosolic Ca signal that either evokes inter-RyR CICR or not. Most diastolic openings do not. But, the likelihood that one will increases during HF and CPVT, elevating DAD propensity Carvedilol is a commonly used FDA-approved ?-blocker. We recently (2011) made a non-?-blocking carvedilol derivative (VK-II-86) that (like carvedilol) reduces RyR open time (OT) and consequently eliminated waves, DADs and CPVT in model mice (50). We removed ?-blocking because it dose-limited the drug?s RyR- targeted action. We have made/screened 100+ carvedilol derivatives and identified some new very promising agents that can dosed to provide an optimal RyR anti-DAD action, independent of ?-block need. Here, we will define the RyR DAD control nexus, determine how CPVT/HF distort operation of this nexus and identify RyR-targeted drugs that normalize the DAD-driving nexus output. We will test the hypothesis that distortion of the spatiotemporal cytosolic Ca signal created by an individual spontaneous diastolic RyR opening is a key pathogenically shared DAD control nexus that can be therapeutically normalized using novel RyR- targeted agents. This multi-PI proposal combines an almost unprecedented combination of single RyR recording, intracellular Ca imaging and muscle cell biology expertise to address our mechanism-to-therapeutic intervention hypothesis.
The specific aims are 1) Determine how CPVT and HF distorts the DAD control nexus and whether those distortions are nexus control factor-specific, disease-dependent and/or part of a continuum of RyR dysfunction and 2) Identify RyR-targeted anti-DAD drugs that normalize pathologically distorted single RyR cytosolic Ca signals and thus limit threat of life-threatening arrhythmias in HF and CPVT. This study will provides a strong mechanistic foundation for understanding DAD origination and its involvement in cardiac disease and thus represents a needed step toward rational design of better therapeutic interventions.

Public Health Relevance

Intracellular calcium signals drive a myriad of cellular phenomena. In the heart, calcium release from intracellular storage sites drives contraction. This calcium release usually does not occur in resting healthy hearts. Malfunction of calcium release control in resting hearts is pathogenic and may trigger arrhythmias and contribute to heart failure. This project defines how calcium release control is distorted by disease and identifies new agents that normalize those distortions. Consequently, this study may lead to the development of a new and promising class of anti-arrhythmic agents and have direct implications for the prevention and treatment of cardiac arrhythmias.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
Program Officer
Lathrop, David A
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Rush University Medical Center
Schools of Medicine
United States
Zip Code
Zsolnay, Vilmos; Fill, Michael; Gillespie, Dirk (2018) Sarcoplasmic Reticulum Ca2+ Release Uses a Cascading Network of Intra-SR and Channel Countercurrents. Biophys J 114:462-473
Yan, Jiajie; Thomson, Justin K; Zhao, Weiwei et al. (2018) Role of Stress Kinase JNK in Binge Alcohol-Evoked Atrial Arrhythmia. J Am Coll Cardiol 71:1459-1470
Yan, Jiajie; Zhao, Weiwei; Thomson, Justin K et al. (2018) Stress Signaling JNK2 Crosstalk With CaMKII Underlies Enhanced Atrial Arrhythmogenesis. Circ Res 122:821-835
Berti, Claudio; Zsolnay, Vilmos; Shannon, Thomas R et al. (2017) Sarcoplasmic reticulum Ca2+, Mg2+, K+, and Cl- concentrations adjust quickly as heart rate changes. J Mol Cell Cardiol 103:31-39
Uehara, Akira; Murayama, Takashi; Yasukochi, Midori et al. (2017) Extensive Ca2+ leak through K4750Q cardiac ryanodine receptors caused by cytosolic and luminal Ca2+ hypersensitivity. J Gen Physiol 149:199-218
Kanaporis, Giedrius; Blatter, Lothar A (2017) Membrane potential determines calcium alternans through modulation of SR Ca2+ load and L-type Ca2+ current. J Mol Cell Cardiol 105:49-58
S√łndergaard, Mads Toft; Liu, Yingjie; Larsen, Kamilla Taunsig et al. (2017) The Arrhythmogenic Calmodulin p.Phe142Leu Mutation Impairs C-domain Ca2+ Binding but Not Calmodulin-dependent Inhibition of the Cardiac Ryanodine Receptor. J Biol Chem 292:1385-1395
Kanaporis, Giedrius; Blatter, Lothar A (2017) Alternans in atria: Mechanisms and clinical relevance. Medicina (Kaunas) 53:139-149
Ramos-Franco, Josefina; Fill, Michael (2016) Approaching ryanodine receptor therapeutics from the calcin angle. J Gen Physiol 147:369-73
Zhang, Jingqun; Zhou, Qiang; Smith, Chris D et al. (2015) Non-?-blocking R-carvedilol enantiomer suppresses Ca2+ waves and stress-induced ventricular tachyarrhythmia without lowering heart rate or blood pressure. Biochem J 470:233-42

Showing the most recent 10 out of 44 publications