ID: 77: FAST-SKELETAL MYOSIN BINDING PROTEIN-C REGULATES SKELETAL MUSCLE CALCIUM SENSITIVITY

2016 ◽  
Vol 64 (4) ◽  
pp. 917.1-917
Author(s):  
BL Lin ◽  
S Govindan ◽  
S Sadayappan ◽  
L Zhao ◽  
J Xu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Contraction ◽  
Skeletal Muscles ◽  
Protein C ◽  
Molecular Level ◽  
Binding Protein ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding

Mutations in myosin binding protein-C (MyBP-C) cause both cardiac and skeletal muscle diseases, such as hypertrophic cardiomyopathy and distal arthrogryposis. There are three isoforms of MyBP-C: slow-skeletal, fast-skeletal, and cardiac (ssMyBP-C, fsMyBP-C, and cMyBP-C, respectively). These isoforms reside within the sarcomere, the functional unit of muscle contraction at the molecular level. However, the function of the three major MyBP-C isoforms remains unclear. The present study is the first to focus on the least characterized isoform, fsMyBP-C, which is expressed in fast- and mixed-type skeletal muscles. To determine the necessity of fsMyBP-C for regulation of contraction in the sarcomere, we generated a conventional fast-skeletal MyBP-C knockout (FSKO) mouse model. We analyzed both structural changes and regulatory function of skeletal muscles from heterozygous (FSKO−/+) and homozygous (FSKO−/−), compared to wild-type (WT) mice. Neither heterozygous nor homozygous FSKO mice exhibited changes in morbidity or mortality relative to WT mice. Molecular analyses revealed a complete knockout of fsMyBP-C in the FSKO−/− skeletal muscles compared to FSKO−/+ and WT mice. Histopathological analyses of both Extensor digitorum longus (EDL) and soleus muscles revealed no obvious abnormalities, such as fibrosis or calcification, in either heterozygous or homozygous FSKO mice. Though fiber structure is preserved, we demonstrated that EDL muscles from FSKO−/− mice increases Ca2+-sensitivity of force development, suggesting that fsMyBP-C regulates contraction at the molecular level by decreasing Ca2+-sensitivity. While others have previously proposed the role of cMyBP-C is to increase Ca2+-sensitivity to normalize a Ca2+ gradient imbalance in the heart, we propose that the role of fsMyBP-C in skeletal muscles is to reduce Ca2+-sensitivity of the thin filaments in order to normalize the reversed Ca2+ gradient imbalance. Despite opposite effects on Ca2+-sensitivity, MyBP-C share the same functional role in both cardiac and skeletal muscles. Thus, in addition to elucidating the role of fast-skeletal MyBP-C and its regulation of skeletal muscle contraction, the present study provides insight into the cardiac isoform and its regulation of cardiac contraction.

Abstract 391: The Pathophysiological Role of MYBPHL in Dilated Cardiomyopathy

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
David Y Barefield ◽  
Megan J Puckelwartz ◽  
Lisa Dellefave-Castillo ◽  
Elizabeth M McNally
Keyword(s):  
Cardiac Function ◽  
Protein C ◽  
Stop Codon ◽  
Binding Protein ◽  
Premature Stop Codon ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Pathophysiological Role ◽  
Myosin Binding

Background: Cardiomyopathy is a leading cause of heart failure and is highly heritable. One common form of cardiomyopathy is dilated cardiomyopathy (DCM), which currently has over 70 identified genes that have been described as causative for the disease. Genetic testing for DCM employs gene panels and has a sensitivity of mutation detection less than 50%, indicating that additional genes contribute to DCM. Here, we employed whole genome sequencing (WGS) in a family with DCM and heart block who had previously undergone unrevealing genetic testing. We identified a premature stop codon in the MYBPHL gene, a gene that has not previously been linked to DCM as a likely cause of DCM in this family. Myosin binding protein H Like (MyBP-HL) is a muscle-expressed protein bearing structural similarity to myosin binding protein C (MyBP-C), which is commonly mutated gene in cardiomyopathies. Objective: Determine the physiological and pathophysiological role of Mybphl . Results: RNA-seq and qPCR from mouse hearts revealed that Mybphl is highly expressed in the right and left atria with lower expression in the ventricle and virtually no expression in skeletal muscle. As MyBP-HL shares a high homology with the myofilament proteins cardiac myosin binding protein-C and H, we investigated if MyBP-HL is also myofilament-associated. We determined that MyBP-HL protein is myofilament-associated in the atria although not clearly so in ventricle. To assess the requirement of MyBP-HL in cardiac function, we used a mouse model with an insertional disruption of the Mybphl gene. These mice have deficits in in vivo cardiac function, with reduced fractional shortening. In addition, ECG recordings from the Mybphl null mice show conduction system abnormalities affecting atrioventricular conduction. Conclusions: WGS identified a premature stop codon in MYBPHL in human DCM. A mouse model with a disrupted Mybphl gene showed similar pathophysiological features as the humans with reduced ventricular function and cardiac conduction system abnormalities. MyBP-HL is an important protein for normal cardiac function.

Myosin binding protein-C and hypertrophic cardiomyopathy: role of altered C10 domain

2019 ◽  
Vol 115 (14) ◽  
pp. 1943-1945 ◽  
Author(s):  
Mohammad Bakhtiar Hossain ◽  
Zaher Elbeck ◽  
Humam Siga ◽  
Ralph Knöll
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Protein C ◽  
Binding Protein ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding

scholarly journals On the Functional Assessment of Hypertrophic Cardiomyopathy-Causing Mutations in Human β-Cardiac Myosin and the Role of Myosin Binding Protein-C

2019 ◽  
Vol 116 (3) ◽  
pp. 466a-467a
Author(s):  
Darshan V. Trivedi ◽  
Saswata S. Sarkar ◽  
Arjun S. Adhikari ◽  
Makenna M. Morck ◽  
Kristina B. Kooiker ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Functional Assessment ◽  
Protein C ◽  
Binding Protein ◽  
Cardiac Myosin ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding

scholarly journals Impact of Hypertrophic Cardiomyopathy Mutations and the Role of Myosin Binding Protein-C on the Sequestered State of Myosin

2018 ◽  
Vol 114 (3) ◽  
pp. 317a
Author(s):  
Darshan V. Trivedi ◽  
Saswata S. Sarkar ◽  
Makenna M. Morck ◽  
Arjun A. Adhikari ◽  
Kathleen M. Ruppel ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Protein C ◽  
Binding Protein ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
Cardiomyopathy Mutations

scholarly journals Site-directed spectroscopy of cardiac myosin-binding protein C reveals effects of phosphorylation on protein structural dynamics

2016 ◽  
Vol 113 (12) ◽  
pp. 3233-3238 ◽  
Author(s):  
Brett A. Colson ◽  
Andrew R. Thompson ◽  
L. Michel Espinoza-Fonseca ◽  
David D. Thomas
Keyword(s):  
Protein C ◽  
Binding Protein ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Md Simulations ◽  
Cardiac Myosin ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding

We have used the site-directed spectroscopies of time-resolved fluorescence resonance energy transfer (TR-FRET) and double electron–electron resonance (DEER), combined with complementary molecular dynamics (MD) simulations, to resolve the structure and dynamics of cardiac myosin-binding protein C (cMyBP-C), focusing on the N-terminal region. The results have implications for the role of this protein in myocardial contraction, with particular relevance to β-adrenergic signaling, heart failure, and hypertrophic cardiomyopathy. N-terminal cMyBP-C domains C0–C2 (C0C2) contain binding regions for potential interactions with both thick and thin filaments. Phosphorylation by PKA in the MyBP-C motif regulates these binding interactions. Our spectroscopic assays detect distances between pairs of site-directed probes on cMyBP-C. We engineered intramolecular pairs of labeling sites within cMyBP-C to measure, with high resolution, the distance and disorder in the protein’s flexible regions using TR-FRET and DEER. Phosphorylation reduced the level of molecular disorder and the distribution of C0C2 intramolecular distances became more compact, with probes flanking either the motif between C1 and C2 or the Pro/Ala-rich linker (PAL) between C0 and C1. Further insight was obtained from microsecond MD simulations, which revealed a large structural change in the disordered motif region in which phosphorylation unmasks the surface of a series of residues on a stable α-helix within the motif with high potential as a protein–protein interaction site. These experimental and computational findings elucidate structural transitions in the flexible and dynamic portions of cMyBP-C, providing previously unidentified molecular insight into the modulatory role of this protein in cardiac muscle contractility.

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