In adult cardiac muscle, depolarization activates a small Ca2+ influx that triggers intracellular Ca2+release (i.e., Ca2+-induced Ca2+ release, CICR) resulting in contraction. This intracellular Ca2+ release is mediated by ryanodine receptor (RyR) channels in the sarcoplasmic reticulum (SR). In neonate cardiac muscle, the RyR-mediated CICR process is absent. The Ca2+ that triggers contractile activation does not come from intracellular Ca2+stores. Instead, it comes via Ca2+ influx through voltage-dependent Ca2+ channels in the surface membrane. In both contexts (adult and neonate), there are large cytosolic Ca2+ fluctuations associated with excitation-contraction coupling (E-C coupling).All mammalian cells (including cardiac cells) contain inositol trisphosphate receptor (InsP3R) channels. The InsP3R and RyR are homologous intracellular Ca2+ release channels. There is substantial evidence that InsP3R-mediated Ca2+ signaling is important in both the development and pathophysiology of cardiac muscle. In normal adult cells, the InsP3 signaling cascade plays a role in alpha-adrenergic ionotropic actions, contractile activation, and perhaps even in the regulation of transcription.Here, we focus on defining the underlying tenets of InsP3R-medated Ca2+ signaling in neonate myocytes. Neonate ventricular muscle presents a special case because it has minimal RyR-mediated intracellular Ca2+ release and therefore represents a less complicated environment in which to study of InsP3R-mediated signals. Our long range goals (past this proposal) are (1) to establish the physiological roles of InsP3R-medated Ca2+ in heart (in neonate, health and disease), and, (2) define the mechanisms that allow high fidelity InsP3R-medated Ca2+ signaling to be maintained in the """"""""Ca2+ noise"""""""" of E-C coupling. Such physiological applications require understanding the underlying mechanisms. In this proposal, we begin by focusing on the mechanisms governing the elemental properties of InsP3R-medated Ca2+ signaling in the neonate heart. To address this goal a combination of scanning confocal imaging, single channel recording, stochastic channel gating theory and Ca2+ diffusion modeling are directed at the following two specific aims.
Specific Aim #1 is to test the hypothesis that single InsP3R channel function (permeation/gating) is impacted by the complex salt environment found in cells (neonate ventricular myocytes).
Specific Aim #2 is to test the hypothesis that InsP3R-mediated Ca2+ signaling in neonate ventricular myocytes is mediated by highly organized spatial and temporal recruitment/summation of elemental stereotypical Ca2+-release events. The goal is to provide insights into the mechanisms that govern local InsP3R-mediated Ca2+ signaling in neonate ventricular myocytes.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL071741-02
Application #
6784134
Study Section
Special Emphasis Panel (ZRG1-MDCN-4 (01))
Program Officer
Pearson, Gail D
Project Start
2003-08-01
Project End
2007-05-31
Budget Start
2004-06-01
Budget End
2005-05-31
Support Year
2
Fiscal Year
2004
Total Cost
$296,000
Indirect Cost
Name
Loyola University Chicago
Department
Physiology
Type
Schools of Medicine
DUNS #
791277940
City
Maywood
State
IL
Country
United States
Zip Code
60153
Escobar, Ariel L; Perez, Claudia G; Reyes, Mariano E et al. (2012) Role of inositol 1,4,5-trisphosphate in the regulation of ventricular Ca(2+) signaling in intact mouse heart. J Mol Cell Cardiol 53:768-79
Porta, Maura; Zima, Aleksey V; Nani, Alma et al. (2011) Single ryanodine receptor channel basis of caffeine's action on Ca2+ sparks. Biophys J 100:931-8
Ramos-Franco, Josefina; Gomez, Ana M; Nani, Alma et al. (2010) Ryanodol action on calcium sparks in ventricular myocytes. Pflugers Arch 460:767-76
Qin, Jia; Valle, Giorgia; Nani, Alma et al. (2009) Ryanodine receptor luminal Ca2+ regulation: swapping calsequestrin and channel isoforms. Biophys J 97:1961-70
Porta, Maura; Diaz-Sylvester, Paula L; Nani, Alma et al. (2008) Ryanoids and imperatoxin affect the modulation of cardiac ryanodine receptors by dihydropyridine receptor Peptide A. Biochim Biophys Acta 1778:2469-79
Snopko, Rose M; Aromolaran, Ademuyiwa S; Karko, Kimberly L et al. (2007) Cell culture modifies Ca2+ signaling during excitation-contraction coupling in neonate cardiac myocytes. Cell Calcium 41:13-25
Valverde, Carlos A; Mundina-Weilenmann, Cecilia; Reyes, Mariano et al. (2006) Phospholamban phosphorylation sites enhance the recovery of intracellular Ca2+ after perfusion arrest in isolated, perfused mouse heart. Cardiovasc Res 70:335-45