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bioRxiv · 10.1101/067066

Mutations in the catalytic domain of human β-cardiac myosin that cause early onset hypertrophic cardiomyopathy significantly increase the fundamental parameters that determine ensemble force and velocity

Arjun S Adhikari·Kristina B Kooiker·Chao Liu·Saswata S Sarkar·Daniel Bernstein·James A Spudich·Kathleen M Ruppel
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Abstract

Hypertrophic cardiomyopathy (HCM) is a heritable cardiovascular disorder that affects 1 in 500 people. In infants it can be particularly severe and it is the leading cause of sudden cardiac death in pediatric populations. A high percentage of HCM is attributed to mutations in {beta}-cardiac myosin, the motor protein that powers ventricular contraction. This study reports how two mutations that cause early-onset HCM, D239N and H251N, affect the mechanical output of human {beta}-cardiac myosin at the molecular level. We observe extremely large increases (25% - 95%) in the actin gliding velocity, single molecule intrinsic force, and ATPase activity of the two mutant myosin motors compared to wild type myosin. In contrast to previous studies of HCM-causing mutations in human {beta}-cardiac myosin, these mutations were striking in that they caused changes in biomechanical parameters that were both greater in magnitude and more uniformly consistent with a hyper-contractile phenotype. In addition, S1-S2 binding studies revealed a significant decrease in affinity of the H251N motor for S2, suggesting that this mutation may further increase hyper-contractility by releasing active motors from a sequestered state. This report shows, for the first time, a clear and significant gain in function for all tested molecular biomechanical parameters due to HCM mutations in human {beta}-cardiac myosin.

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Arjun S Adhikari, Kristina B Kooiker, Chao Liu, Saswata S Sarkar, Daniel Bernstein, James A Spudich, Kathleen M Ruppel. 2016-08-02. Mutations in the catalytic domain of human β-cardiac myosin that cause early onset hypertrophic cardiomyopathy significantly increase the fundamental parameters that determine ensemble force and velocity. https://doi.org/10.1101/067066

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