Excitation-contraction coupling in the heart confers a tight linkage between the L-type calcium channel and the intracellular environment so that Ca2+ ingress upon depolarization triggers contraction. We have been studying the complex architecture, regulation and receptor drug sites on the subunits that comprise the cardiac calcium channel. Considering the importance of this channel in maintaining normal cardiac function, it is not surprising that defects have been found in some types of human heart failure. This continuing project focuses on subunit functional interaction in vivo on the normal and falling heart. The latter is produced in the mouse by a specific increase of L-type calcium channel subunits in a transgenic mouse, which has provided us with a cardiomyopathy very close to the human type. Transgenic """"""""remodeling"""""""" of the heart is not only a convenient method of altering subunit stoichiometry in vivo, but provides a way to approach mechanisms of heart failure in a logical manner. The long-term objective is characterization of calcium channel regulation, in terms of the pore, subunit importance, and calcium antagonist receptor functions. The added feature in this renewal application is the transgenic and knockout approach, encompassing coordinated physiological, biochemical and microanatomical methodology. We hope to provide further molecular information on the normal L-type cardiac channel and its possible role in the diseased heart.
The specific aims are: 1) to over-express the human cardiac alpha1 subunit specifically and only in the myocytes of transgenic mice. Physiological function, genotype frequency, and expression levels of the transgene, as well as comprehensive cardiac pathological assessment, hopefully will yield important new information. 2) To eliminate the functional effects of the beta-subunit in mouse heart by generating a dominant negative expression system. The high affinity alpha1 interactive domain (AID) will be over- expressed in a cardiac-specific manner, and this will then act as a trap for beta subunits. Characterization is as in Aim 1. We hope to provide new information n the role of the beta-subunit in vivo. 3) To generate conditional knockout mice lacking the alpha2/delta subunit in the heart. Studying these mice, again on the molecular, cellular and whole organ level, should give us valuable information on the role of this subunit in vivo. 4) To continue studies on the pore-lining region of calcium channels. We suggest that these studies will give us specific information concerning some structural features of the pore that are involved in regulation of the channel.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Program Projects (P01)
Project #
2P01HL022619-21A1
Application #
6109530
Study Section
Project Start
1999-07-01
Project End
2000-06-30
Budget Start
1998-10-01
Budget End
1999-09-30
Support Year
21
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Cincinnati
Department
Type
DUNS #
City
Cincinnati
State
OH
Country
United States
Zip Code
45221
Jagatheesan, Ganapathy; Rajan, Sudarsan; Wieczorek, David F (2010) Investigations into tropomyosin function using mouse models. J Mol Cell Cardiol 48:893-8
Fuller-Bicer, Geraldine A; Varadi, Gyula; Koch, Sheryl E et al. (2009) Targeted disruption of the voltage-dependent calcium channel alpha2/delta-1-subunit. Am J Physiol Heart Circ Physiol 297:H117-24
Sadayappan, Sakthivel; Finley, Natosha; Howarth, Jack W et al. (2008) Role of the acidic N'region of cardiac troponin I in regulating myocardial function. FASEB J 22:1246-57
Pattison, James Scott; Waggoner, Jason R; James, Jeanne et al. (2008) Phospholamban overexpression in transgenic rabbits. Transgenic Res 17:157-70
Jagatheesan, Ganapathy; Rajan, Sudarsan; Petrashevskaya, Natalia et al. (2007) Rescue of tropomyosin-induced familial hypertrophic cardiomyopathy mice by transgenesis. Am J Physiol Heart Circ Physiol 293:H949-58
Scragg, Jason L; Fearon, Ian M; Boyle, John P et al. (2005) Alzheimer's amyloid peptides mediate hypoxic up-regulation of L-type Ca2+ channels. FASEB J 19:150-2
Rubio, Marta; Bodi, Ilona; Fuller-Bicer, Geraldine A et al. (2005) Sarcoplasmic reticulum adenosine triphosphatase overexpression in the L-type Ca2+ channel mouse results in cardiomyopathy and Ca2+ -induced arrhythmogenesis. J Cardiovasc Pharmacol Ther 10:235-49
Bodi, Ilona; Mikala, Gabor; Koch, Sheryl E et al. (2005) The L-type calcium channel in the heart: the beat goes on. J Clin Invest 115:3306-17
Petrashevskaya, Natalia N; Bodi, Ilona; Koch, Sheryl E et al. (2004) Effects of alpha1-adrenergic stimulation on normal and hypertrophied mouse hearts. Relation to caveolin-3 expression. Cardiovasc Res 63:561-72
Groner, Ferdi; Rubio, Marta; Schulte-Euler, Patrick et al. (2004) Single-channel gating and regulation of human L-type calcium channels in cardiomyocytes of transgenic mice. Biochem Biophys Res Commun 314:878-84

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