Receptor-modulated ion channels play a primary role in the neuroendocrine regulation of cardiac function. Thus, for example, cholinergic activation of cardiac muscarinic receptors may affect the initiation and propagation of the heart beat by opening potassium channels in the cardiac sarcolemma. The long-range objective of this project is to understand quantitatively and at the level of molecular detail, how these regulatory processes operate, with particular emphasis on the recently discovered role of guanine nucleotide binding proteins (G-proteins) in the receptor effector coupling process. Specifically, muscarinic activation of the inwardly rectifying potassium channel K+(m) will be studied in isolated cardiac atrial myocytes. Use of this well defined system should facilitate the attainment of the following three primary objectives. 1. Identification of the critical steps involved in the coupling process in vivo and its modeling in terms of clearly defined chemical kinetic processes. Whole-cell gigaseal recording will be used to follow the evolution of K+(m) 1. in response to manipulations activating receptor or G-protein in a manner appropriate for revealing the specific kinetic steps involved in receptor-channel coupling. The results will be used to construct a mathematical model to be tested and refined by comparing its predictions with experiment. 2. Identification of the type and moiety of G-protein(s) that activate K+(m) in vivo by characterizing the effects of intracellularly injected, highly purifiid G-protein components on the ionic currents of cardiac myocytes. The results will be carefully related to those seen at the single-channel level with excised patches in order to insure that these two different techniques yield consistent and physiologically relevant conclusions. 3. Efforts will be made to reconstitute the control of K(m) channels in lipid bilayer membranes by G-protein and receptor, with the ultimate goal of elucidating the structural requirements for a functional regulatory system. This project is likely to further our understanding of the neurohormonal regulation of normal and abnormal cardiac function. Moreover, since G-proteins have been found to couple receptors to effectors in virtually all cell types, the results are bound to be of more general significance with respect to the control of cell function by extracellular signals.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37HL037127-08
Application #
3486140
Study Section
Physiology Study Section (PHY)
Project Start
1989-09-30
Project End
1994-06-30
Budget Start
1992-07-01
Budget End
1993-06-30
Support Year
8
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of Virginia
Department
Type
Schools of Medicine
DUNS #
001910777
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
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Otero, A S; Doyle, M B; Hartsough, M T et al. (1999) Wild-type NM23-H1, but not its S120 mutants, suppresses desensitization of muscarinic potassium current. Biochim Biophys Acta 1449:157-68
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Otero, A S; Xu, L; Ni, Y et al. (1998) Receptor-independent activation of atrial muscarinic potassium channels in the absence of nucleotides. J Biol Chem 273:28868-72
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Otero, A S; Yi, X B; Gray, M C et al. (1995) Membrane depolarization prevents cell invasion by Bordetella pertussis adenylate cyclase toxin. J Biol Chem 270:9695-7
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Li, Y; Hanf, R; Otero, A S et al. (1994) Differential effects of pertussis toxin on the muscarinic regulation of Ca2+ and K+ currents in frog cardiac myocytes. J Gen Physiol 104:941-59
Otero, A de S; Sweitzer, N M (1993) Benzoquinoid tyrosine kinase inhibitors are potent blockers of cardiac muscarinic receptor function. Mol Pharmacol 44:595-604

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