Hypertrophic cardiomyopathy-linked variants of cardiac myosin-binding protein C3 display altered molecular properties and actin interaction

Da'as, Sahar I., Fakhro, Khalid, Thanassoulas, Angelos, Krishnamoorthy, Navaneethakrishnan, Saleh, Alaaeldin, Calver, Brian L., Safieh-Garabedian, Bared, Toft, Egon, Nounesis, George, Lai, F. Anthony ORCID: https://orcid.org/0000-0003-2852-8547 and Nomikos, Michail 2018. Hypertrophic cardiomyopathy-linked variants of cardiac myosin-binding protein C3 display altered molecular properties and actin interaction. Biochemical Journal 475 (24) , pp. 3933-3948. 10.1042/BCJ20180685

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Abstract

The most common inherited cardiac disorder, hypertrophic cardiomyopathy (HCM), is characterized by thickening of heart muscle, for which genetic mutations in cardiac myosin-binding protein C3 (c-MYBPC3) gene, is the leading cause. Notably, patients with HCM display a heterogeneous clinical presentation, onset and prognosis. Thus, delineating the molecular mechanisms that explain how disparate c-MYBPC3 variants lead to HCM is essential for correlating the impact of specific genotypes on clinical severity. Herein, five c-MYBPC3 missense variants clinically associated with HCM were investigated; namely V1 (R177H), V2 (A216T), V3 (E258K), V4 (E441K) and double mutation V5 (V3 + V4), all located within the C1 and C2 domains of MyBP-C, a region known to interact with sarcomeric protein, actin. Injection of the variant complementary RNAs in zebrafish embryos was observed to recapitulate phenotypic aspects of HCM in patients. Interestingly, V3- and V5-cRNA injection produced the most severe zebrafish cardiac phenotype, exhibiting increased diastolic/systolic myocardial thickness and significantly reduced heart rate compared with control zebrafish. Molecular analysis of recombinant C0–C2 protein fragments revealed that c-MYBPC3 variants alter the C0–C2 domain secondary structure, thermodynamic stability and importantly, result in a reduced binding affinity to cardiac actin. V5 (double mutant), displayed the greatest protein instability with concomitant loss of actin-binding function. Our study provides specific mechanistic insight into how c-MYBPC3 pathogenic variants alter both functional and structural characteristics of C0–C2 domains leading to impaired actin interaction and reduced contractility, which may provide a basis for elucidating the disease mechanism in HCM patients with c-MYBPC3 mutations.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences
Publisher:	Portland Press
ISSN:	0264-6021
Last Modified:	26 Oct 2022 07:28
URI:	https://orca.cardiff.ac.uk/id/eprint/124945

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