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bioRxiv · 10.1101/2023.07.13.548909

Kinetics and Mapping of Ca-driven Calmodulin conformations on Skeletal and Cardiac Muscle Ryanodine Receptors

Rebbeck, R. T.·Svensson, B.·Zhang, J.·Thomas, D. D.·Bers, D. M.·Cornea, R. L.
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Abstract

Calmodulin (CaM) transduces [Ca2+] information regulating the rhythmic Ca2+ cycling between the sarcoplasmic reticulum and cytoplasm during relaxation and contraction in cardiac and skeletal muscle. However, the structural dynamics by which CaM modulates the SR Ca2+ release channel (ryanodine receptor, RyR) at physiologically relevant [Ca2+] is unknown. Using fluorescence lifetime detection of FRET between RyR-bound FKBP and CaM, we resolved different structural states of CaM and Ca-driven shifts in the conformation of CaM bound to RyR. We found that CaM becomes more compact in contracting high-Ca2+ vs. relaxing low-Ca2+. Skeletal and cardiac RyR isoforms show different CaM-RyR conformations, and binding and structural kinetics reflect functional roles. Furthermore, our FRET methods provide insight representative of physiological CaM-RyR structure, in synergy and comparison with cryo-EM models, which result from more disrupted samples. This technology will drive future studies focusing on pathologic CaM-RyR interactions, and on RyR dynamics with other important modulators.

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Rebbeck, R. T., Svensson, B., Zhang, J., Thomas, D. D., Bers, D. M., Cornea, R. L.. 2023-07-13. Kinetics and Mapping of Ca-driven Calmodulin conformations on Skeletal and Cardiac Muscle Ryanodine Receptors. https://doi.org/10.1101/2023.07.13.548909

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