Actin-Binding Compounds, Discovered from Fret-Based High-Throughput Screening, Differentially Affect Skeletal and Cardiac Muscle

Abstract

We have used spectroscopic and functional assays to evaluate the effects of actin-binding compounds on striated muscle protein structure and function. Actin is present in every human cell, and its interaction with multiple myosin isoforms and multiple actin-binding proteins is essential for cellular viability. Our high-throughput time-resolved fluorescence resonance energy transfer (TR-FRET) assay previously detected several compounds that bind to actin and affected actomyosin structure and function (Guhathakurta, et al. 2018, J Biol Chem 293:12288). To determine the muscle specificity of these compounds, we tested their effects on intact skeletal and cardiac myofibrils, which represent a more physiologically relevant environment. We found that the concentration-dependent responses of several compounds were different for skeletal and cardiac myofibrils, suggesting that the mode of action is different for the two muscle types. These compounds also affected the transition of monomeric G-actin to filamentous F-actin of different actin isoforms (skeletal and cardiac) by different degrees; further confirming the specificity of these compounds for a specific muscle type. We conclude that these compounds differentially affect skeletal and cardiac muscles, and these results set the stage to screen large chemical libraries for discovery of novel actin-binding drugs with specific therapeutic potential for treating disorders of cardiac or skeletal muscle. This work was supported by NIH grants to DDT (R01AR032961, R37AG26160).