In excitable cells, a small Ca2+ influx through the surface membrane may activate intracellular Ca2+ release channels called ryanodine receptors (RyRs) on the endoplasmic or sarcoplasmic reticulum (SR). The resulting RyR-mediated Ca2+ release regulates many cellular processes like contraction, secretion, synaptic transmission, fertilization, nuclear pore regulation and transcription. Here, the case in point is cardiac muscle. In these cells, surface depolarization activates an L-type Ca2+ channel generating a small Ca2+ flux which activates type-2 ryanodine receptors (RyR2) on the sarcoplasmic reticulum (SR). Activation of multiple RyR2 channels at discrete sites on the SR generates localized Ca2+ release events called sparks. In cells, sparks are the elemental unit of RyR2-mediated Ca2+ release. Recruitment and summation of many sparks generates the global Ca2+ release phenomena that drive cardiac contractility. The local control mechanisms that govern the RyR2-mediated spark are poorly understood. One of these mechanisms is local RyR2 Ca2+ activation, often referred to as Ca2+-induced Ca2+ release (CICR). CICR is an intuitively a self-reinforcing process whose """"""""explosive"""""""" positive feedback (i.e., released Ca2+ should trigger further release) should ultimately empty the SR Ca2+ store. This does not happen in cells. Instead, CICR is precisely controlled indicating that some negative-feedback mechanism(s) must exist to counter the inherent positive feedback of CICR. Two cytosolic mechanisms, Ca2+-dependent inactivation and Ca2+-dependent adaptation, have been proposed to be the stabilizing negative feedback. It has also been proposed that the needed negative control may arise from RyR2 regulation by local [Ca2+] changes inside the SR. Delineating mechanisms that govern RyR2 local Ca2+ control is clearly essential to understanding the origin of the Ca2+ spark. This is our focus here and the following hypothesis will be tested. Single RyR2 channels are driven by multiple forms of cytosolic Ca2+ feedback (e.g., feed through, neighbor-induced & paired pulse facilitation). This is controlled/countered by a combination of lumenal negative control mechanisms (e.g., Ca2+-flux reduction, direct & indirect Ca2+ deactivation) to ultimately define the spatiotemporal nature of the Ca2+ spark.
The specific aims are:
Specific Aim #1 : Define the cytosolic local Ca2+ positive feedback that drives the function of single RyR2 Ca2+ release channels.
Specific Aim #2 : Define lumenal Ca2+ negative control mechanisms that govern operation of single RyR2 Ca2+ release channels and ultimately the spatiotemporal nature of the Ca2+ spark. ? ?

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL057832-12
Application #
7475211
Study Section
Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
Program Officer
Przywara, Dennis
Project Start
1997-05-01
Project End
2010-07-31
Budget Start
2008-08-01
Budget End
2009-07-31
Support Year
12
Fiscal Year
2008
Total Cost
$359,270
Indirect Cost
Name
Rush University Medical Center
Department
Physiology
Type
Schools of Medicine
DUNS #
068610245
City
Chicago
State
IL
Country
United States
Zip Code
60612
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
Søndergaard, 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