The capacity of the ventricles to perform work (i.e., power) is essential for moving blood throughout the circulatory system. Ventricular/myocyte power is determined ultimately by three myofibrillar properties;(i) the amount of force developed, (ii) the rate of force development, and (iii) the rate that myocardium shortens against loads. However, the sub-cellular processes that determine these properties are incompletely understood. The overall purpose of this study is to determine the sub-cellular factors that regulate myocyte power generating capacity. The specific objectives of the proposed studies are designed to determine (1) if PKA-mediated phosphorylation of cardiac troponin I (cTnI) is both necessary and sufficient to dictate sarcomere length dependence of force generation in cardiac myocytes, (2) how titin, MyBP-C, and myosin cross-bridges interact to modulate sarcomere length dependence of power output, and (3) to determine the time-course of changes in sarcomere length dependence of force, rates of force development, loaded shortening, and power output during the progression of heart failure. A rodent model of heart failure will be used to test the hypothesis that myocytes in compensated hearts exhibit greater sarcomere length dependence of force and power output due to a combination of greater expression of the larger N2BA titin isoform and greater PKA- induced myofibrillar protein phosphorylation, but with progression to ventricular failure sarcomere length dependence of force and power is markedly reduced due to reduced PKA- mediated phosphorylation of titin, MyBP-C, and cTnI. These studies are highly significant in their potential to determine the basis for the control of power-generating capacity in healthy myocytes and how these processes are altered with the progression of heart failure.

Public Health Relevance

The goal of this project is to understand the factors that control the power generating capacity of individual cardiac myocytes. The control of myocyte power output dictates the pumping capacity of healthy hearts and dysregulation of these control factors contributes to pathological heart conditions, which afflict nearly 6 million citizens of th United States and is the most common cause of hospitalization of US citizens over 65 years of age.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-CVRS-B (02))
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Adhikari, Bishow B
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University of Missouri-Columbia
Schools of Medicine
United States
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Hanft, Laurin M; Greaser, Marion L; McDonald, Kerry S (2014) Titin-mediated control of cardiac myofibrillar function. Arch Biochem Biophys 552-553:83-91
Domeier, Timothy L; Roberts, Cale J; Gibson, Anne K et al. (2014) Dantrolene suppresses spontaneous Ca2+ release without altering excitation-contraction coupling in cardiomyocytes of aged mice. Am J Physiol Heart Circ Physiol 307:H818-29
Hanft, Laurin M; Biesiadecki, Brandon J; McDonald, Kerry S (2013) Length dependence of striated muscle force generation is controlled by phosphorylation of cTnI at serines 23/24. J Physiol 591:4535-47
Marshall, Kurt D; Muller, Brittany N; Krenz, Maike et al. (2013) Heart failure with preserved ejection fraction: chronic low-intensity interval exercise training preserves myocardial O2 balance and diastolic function. J Appl Physiol (1985) 114:131-47
Hanft, Laurin M; McDonald, Kerry S (2010) Length dependence of force generation exhibit similarities between rat cardiac myocytes and skeletal muscle fibres. J Physiol 588:2891-903
Hanft, Laurin M; McDonald, Kerry S (2009) Sarcomere length dependence of power output is increased after PKA treatment in rat cardiac myocytes. Am J Physiol Heart Circ Physiol 296:H1524-31
Hanft, Laurin M; Korte, Fredrick S; McDonald, Kerry S (2008) Cardiac function and modulation of sarcomeric function by length. Cardiovasc Res 77:627-36
Korte, F Steven; McDonald, Kerry S (2007) Sarcomere length dependence of rat skinned cardiac myocyte mechanical properties: dependence on myosin heavy chain. J Physiol 581:725-39
Hinken, Aaron C; Korte, F Steven; McDonald, Kerry S (2006) Porcine cardiac myocyte power output is increased after chronic exercise training. J Appl Physiol 101:40-6
Hinken, Aaron C; McDonald, Kerry S (2006) Beta-myosin heavy chain myocytes are more resistant to changes in power output induced by ischemic conditions. Am J Physiol Heart Circ Physiol 290:H869-77

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