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?-Cardiac myosin hypertrophic cardiomyopathy mutations release sequestered heads and increase enzymatic activity.

ABSTRACT: Hypertrophic cardiomyopathy (HCM) affects 1 in 500 people and leads to hyper-contractility of the heart. Nearly 40 percent of HCM-causing mutations are found in human ?-cardiac myosin. Previous studies looking at the effect of HCM mutations on the force, velocity and ATPase activity of the catalytic domain of human ?-cardiac myosin have not shown clear trends leading to hypercontractility at the molecular scale. Here we present functional data showing that four separate HCM mutations located at the myosin head-tail (R249Q, H251N) and head-head (D382Y, R719W) interfaces of a folded-back sequestered state referred to as the interacting heads motif (IHM) lead to a significant increase in the number of heads functionally accessible for interaction with actin. These results provide evidence that HCM mutations can modulate myosin activity by disrupting intramolecular interactions within the proposed sequestered state, which could lead to hypercontractility at the molecular level.

SUBMITTER: Adhikari AS

PROVIDER: S-EPMC6582153 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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β-Cardiac myosin hypertrophic cardiomyopathy mutations release sequestered heads and increase enzymatic activity.

Adhikari Arjun S AS Trivedi Darshan V DV Sarkar Saswata S SS Song Dan D Kooiker Kristina B KB Bernstein Daniel D Spudich James A JA Ruppel Kathleen M KM

Nature communications 20190618 1

Hypertrophic cardiomyopathy (HCM) affects 1 in 500 people and leads to hyper-contractility of the heart. Nearly 40 percent of HCM-causing mutations are found in human β-cardiac myosin. Previous studies looking at the effect of HCM mutations on the force, velocity and ATPase activity of the catalytic domain of human β-cardiac myosin have not shown clear trends leading to hypercontractility at the molecular scale. Here we present functional data showing that four separate HCM mutations located at ...[more]

PMID: 31213605

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Project description:AIMS:A 25-base pair deletion in the cardiac myosin binding protein-C (cMyBP-C) gene (MYBPC3), proposed to skip exon 33, modifies the C10 domain (cMyBP-C?C10mut) and is associated with hypertrophic cardiomyopathy (HCM) and heart failure, affecting approximately 100 million South Asians. However, the molecular mechanisms underlying the pathogenicity of cMyBP-C?C10mutin vivo are unknown. We hypothesized that expression of cMyBP-C?C10mut exerts a poison polypeptide effect leading to improper assembly of cardiac sarcomeres and the development of HCM. METHODS AND RESULTS:To determine whether expression of cMyBP-C?C10mut is sufficient to cause HCM and contractile dysfunction in vivo, we generated transgenic (TG) mice having cardiac-specific protein expression of cMyBP-C?C10mut at approximately half the level of endogenous cMyBP-C. At 12?weeks of age, significant hypertrophy was observed in TG mice expressing cMyBP-C?C10mut (heart weight/body weight ratio: 4.43?±?0.11?mg/g non-transgenic (NTG) vs. 5.34?±?0.25?mg/g cMyBP-C?C10mut, P?<?0.05). Furthermore, haematoxylin and eosin, Masson's trichrome staining, as well as second-harmonic generation imaging revealed the presence of significant fibrosis and a greater relative nuclear area in cMyBP-C?C10mut hearts compared with NTG controls. M-mode echocardiography analysis revealed hypercontractile hearts (EF: 53.4%±2.9% NTG vs. 66.4% ± 4.7% cMyBP-C?C10mut; P?<?0.05) and early diastolic dysfunction (E/E': 28.7?±?3.7 NTG vs. 46.3?±?8.4 cMyBP-C?C10mut; P?<?0.05), indicating the presence of an HCM phenotype. To assess whether these changes manifested at the myofilament level, contractile function of single skinned cardiomyocytes was measured. Preserved maximum force generation and increased Ca2+-sensitivity of force generation were observed in cardiomyocytes from cMyBP-C?C10mut mice compared with NTG controls (EC50: 3.6?±?0.02?µM NTG vs. 2.90?±?0.01?µM cMyBP-C?C10mut; P?<?0.0001). CONCLUSION:Expression of cMyBP-C protein with a modified C10 domain is sufficient to cause contractile dysfunction and HCM in vivo.

Dataset Information

?-Cardiac myosin hypertrophic cardiomyopathy mutations release sequestered heads and increase enzymatic activity.

Publications

β-Cardiac myosin hypertrophic cardiomyopathy mutations release sequestered heads and increase enzymatic activity.

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