Biophysical Society Thematic Meeting | Canterbury 2023

Towards a More Perfect Union: Multi-Scale Models of Muscle and Their Experimental Validation

Poster Abstracts

28-POS Board 28 HIGH THROUGHPUT ANALYSIS OF THE SUPER-RELAXED STATE OF MYOSIN IN HUMAN MYOCARDIUM Seetharamaiah Attili ; Thomas Kampourakis 1 ; Kenneth S Campbell 2 ; 1 Kings College London, Randall Centre for Cell and Molecular Biophysics, London, United Kingdom 2 University of Kentucky, Department of Physiology and Division of Cardiovascular Medicine, Lexington, KY, USA Heart muscle contractility is controlled by regulatory structural changes in the myosin-containing thick filaments in addition to the classical thin filament-based mechanisms of regulation, whereby ‘myosin motors’ or ‘myosin head domains’ transit between OFF (low ATPase activity and unable to bind to actin) and ON states (higher ATPase activity and high probability to bind actin). When a muscle fibre is not activated, myosin motors are ‘parked’ in a super-relaxed (SRX) or OFF state, a low ATP consuming configuration. The SRX was found to account for a significant proportion of myosin heads in cardiac thick filaments and its dysregulation is pathogenic in heart diseases such as Hypertrophic Cardiomyopathy (HCM). Modulation of the myosin SRX state has become a central theme for the development of targeted therapeutics for cardiomyopathies and heart failure. For instance, Mavacamten, an allosteric modulator that inhibits ATP turnover is known to be a first FDA-approved drug for the treatment of obstructive HCM. However, the development of novel small molecule effectors that directly target the SRX state of cardiac myosin is hampered by the lack of in-vitro screening assays that accurately reproduce its function. In the current study we have developed a high throughput screening method for the SRX state of cardiac myosin, which is based on mant-ATP pulse-chase methodology. Using this assay, we will test the impact of different small molecule effectors on myosin head confirmation in isolated human myocardium from both human donors, and ischemic and non-ischemic heart failure patients.

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