The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
J G Seidman - One of the best experts on this subject based on the ideXlab platform.
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deciphering the super relaxed state of human β cardiac myosin and the mode of action of mavacamten from myosin molecules to muscle fibers
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Robert L Anderson, Saswata S Sarkar, Darshan V Trivedi, Marcus Henze, Henry Gong, Christopher S Rogers, Fiona Wong, Makenna M Morck, Joshua M Gorham, J G SeidmanAbstract:Mutations in β-cardiac myosin, the predominant motor protein for human Heart Contraction, can alter power output and cause cardiomyopathy. However, measurements of the intrinsic force, velocity, and ATPase activity of myosin have not provided a consistent mechanism to link mutations to muscle pathology. An alternative model posits that mutations in myosin affect the stability of a sequestered, super relaxed state (SRX) of the protein with very slow ATP hydrolysis and thereby change the number of myosin heads accessible to actin. Here we show that purified human β-cardiac myosin exists partly in an SRX and may in part correspond to a folded-back conformation of myosin heads observed in muscle fibers around the thick filament backbone. Mutations that cause hypertrophic cardiomyopathy destabilize this state, while the small molecule mavacamten promotes it. These findings provide a biochemical and structural link between the genetics and physiology of cardiomyopathy with implications for therapeutic strategies.
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mavacamten stabilizes a folded back sequestered super relaxed state of β cardiac myosin
bioRxiv, 2018Co-Authors: Robert L Anderson, Saswata S Sarkar, Darshan V Trivedi, Marcus Henze, Henry Gong, Christopher S Rogers, Fiona Wong, Makenna M Morck, J G Seidman, Kathleen M RuppelAbstract:Mutations in β-cardiac myosin, the predominant motor protein for human Heart Contraction, can alter power output and cause cardiomyopathy. Previous studies suggest that myosin function can be regulated by entering a super-relaxed state (SRX) with very slow ATP hydrolysis, but the structural determinants of this state are uncertain. Using a combination of biochemical approaches with electron microscopy and X-ray fiber diffraction, we show that the SRX corresponds to a folded-back state of myosin with increased ordering of heads around the thick filament backbone. The small molecule mavacamten induces this conformation, while mutations causing HCM destabilize it. These findings provide a structural basis for an important mode of regulation of cardiac myosin with implications for the pathogenesis of cardiomyopathy and potential therapeutic development.
Michael Bressan - One of the best experts on this subject based on the ideXlab platform.
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adherens junction engagement regulates functional patterning of the cardiac pacemaker cell lineage
Developmental Cell, 2021Co-Authors: Kandace Thomas, Trevor Henley, Simone Rossi, Joseph M Costello, William J Polacheck, Boyce E Griffith, Michael BressanAbstract:Cardiac pacemaker cells (CPCs) rhythmically initiate the electrical impulses that drive Heart Contraction. CPCs display the highest rate of spontaneous depolarization in the Heart despite being subjected to inhibitory electrochemical conditions that should theoretically suppress their activity. While several models have been proposed to explain this apparent paradox, the actual molecular mechanisms that allow CPCs to overcome electrogenic barriers to their function remain poorly understood. Here, we have traced CPC development at single-cell resolution and uncovered a series of cytoarchitectural patterning events that are critical for proper pacemaking. Specifically, our data reveal that CPCs dynamically modulate adherens junction (AJ) engagement to control characteristics including surface area, volume, and gap junctional coupling. This allows CPCs to adopt a structural configuration that supports their overall excitability. Thus, our data have identified a direct role for local cellular mechanics in patterning critical morphological features that are necessary for CPC electrical activity.
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adherens junction engagement regulates functional patterning of the cardiac pacemaker cell lineage
Social Science Research Network, 2020Co-Authors: Kandace Thomas, Trevor Henley, Simone Rossi, Joseph M Costello, William J Polacheck, Boyce E Griffith, Michael BressanAbstract:Cardiac Pacemaker Cells (CPCs) rhythmically initiate the electrical impulses that drive Heart Contraction. CPCs display the highest rate of spontaneous depolarization in the Heart despite being subjected to inhibitory electrochemical conditions that should theoretically suppress their activity. While several models have been proposed to explain this apparent paradox, the actual molecular mechanisms that allow CPCs to overcome electronic barriers to their function remain largely unexplored. Here we have traced CPC development at single cell resolution and uncovered a series of cytoarchitectural patterning events that are critical for proper pacemaking. Specifically, our data reveal that CPCs dynamically modulate adherens junction (AJ) engagement to control characteristics including surface area, volume, and gap junctional coupling. This allows CPCs to adopt a structural configuration that supports their overall excitability. Thus, our data have identified a previously unrecognized role for local cellular mechanics in patterning critical morphological features that are necessary for CPC electrical activity.
Takashi Mikawa - One of the best experts on this subject based on the ideXlab platform.
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skeletal muscle specific myosin binding protein h is expressed in purkinje fibers of the cardiac conduction system
Circulation Research, 1997Co-Authors: Tatiana N Alyonycheva, Leona Cohengould, Christiana Siewert, Donald A Fischman, Takashi MikawaAbstract:Abstract Heart Contraction is coordinated by conduction of electrical excitation through specialized tissues of the cardiac conduction system. By retroviral single-cell tagging and lineage analyses in the embryonic chicken Heart, we have recently demonstrated that a subset of cardiac muscle cells terminally differentiates as cells of the peripheral conduction system (Purkinje fibers) and that this occurs invariably in perivascular regions of developing coronary arteries. Cis regulatory elements that function in transcriptional regulation of cells in the conducting system have been distinguished from those in contractile cardiac muscle cells; eg, 5′ regulatory sequences of the desmin gene act as enhancer elements in skeletal muscle and in the conduction system but not in cardiac muscle. We hypothesize that Purkinje fiber differentiation involves a switch of the gene expression program from that characteristic of cardiac muscle to one typical of skeletal muscle. To test this hypothesis, we examined the expression of myosin binding protein-H (MyBP-H) in Purkinje fibers of chicken Hearts. This unique myosin binding protein is present in skeletal but not cardiac myocytes. A site-directed polyclonal antibody (AB105) was generated against MyBP-H. Immunohistological analysis of the myocardium mapped the AB105 antigen predominantly to A bands of myofibrils within Purkinje fibers. Western blot analysis of whole extracts from the ventricular wall of adult chicken Hearts revealed that the AB105 epitope was restricted to a single protein of ≈86 kD, the same size as MyBP-H in skeletal muscle. Biochemical properties of the Purkinje fiber 86-kD protein and RNase protection analyses of its mRNA indicate that Purkinje fiber 86-kD protein is indistinguishable from skeletal muscle MyBP-H. The results provide evidence that skeletal muscle MyBP-H is expressed in a subset of cardiac muscle cells that differentiate into Purkinje fibers of the Heart.
Robert L Anderson - One of the best experts on this subject based on the ideXlab platform.
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deciphering the super relaxed state of human β cardiac myosin and the mode of action of mavacamten from myosin molecules to muscle fibers
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Robert L Anderson, Saswata S Sarkar, Darshan V Trivedi, Marcus Henze, Henry Gong, Christopher S Rogers, Fiona Wong, Makenna M Morck, Joshua M Gorham, J G SeidmanAbstract:Mutations in β-cardiac myosin, the predominant motor protein for human Heart Contraction, can alter power output and cause cardiomyopathy. However, measurements of the intrinsic force, velocity, and ATPase activity of myosin have not provided a consistent mechanism to link mutations to muscle pathology. An alternative model posits that mutations in myosin affect the stability of a sequestered, super relaxed state (SRX) of the protein with very slow ATP hydrolysis and thereby change the number of myosin heads accessible to actin. Here we show that purified human β-cardiac myosin exists partly in an SRX and may in part correspond to a folded-back conformation of myosin heads observed in muscle fibers around the thick filament backbone. Mutations that cause hypertrophic cardiomyopathy destabilize this state, while the small molecule mavacamten promotes it. These findings provide a biochemical and structural link between the genetics and physiology of cardiomyopathy with implications for therapeutic strategies.
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mavacamten stabilizes a folded back sequestered super relaxed state of β cardiac myosin
bioRxiv, 2018Co-Authors: Robert L Anderson, Saswata S Sarkar, Darshan V Trivedi, Marcus Henze, Henry Gong, Christopher S Rogers, Fiona Wong, Makenna M Morck, J G Seidman, Kathleen M RuppelAbstract:Mutations in β-cardiac myosin, the predominant motor protein for human Heart Contraction, can alter power output and cause cardiomyopathy. Previous studies suggest that myosin function can be regulated by entering a super-relaxed state (SRX) with very slow ATP hydrolysis, but the structural determinants of this state are uncertain. Using a combination of biochemical approaches with electron microscopy and X-ray fiber diffraction, we show that the SRX corresponds to a folded-back state of myosin with increased ordering of heads around the thick filament backbone. The small molecule mavacamten induces this conformation, while mutations causing HCM destabilize it. These findings provide a structural basis for an important mode of regulation of cardiac myosin with implications for the pathogenesis of cardiomyopathy and potential therapeutic development.
B D Sykes - One of the best experts on this subject based on the ideXlab platform.
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structure and dynamics of the c domain of human cardiac troponin c in complex with the inhibitory region of human cardiac troponin i
Journal of Biological Chemistry, 2003Co-Authors: Darrin A Lindhout, B D SykesAbstract:Cardiac troponin C is the Ca2+-dependent switch for Heart muscle Contraction. Troponin C is associated with various other proteins including troponin I and troponin T. The interaction between the subunits within the troponin complex is of critical importance in understanding contractility. Following a Ca2+ signal to begin Contraction, the inhibitory region of troponin I comprising residues Thr128-Arg147 relocates from its binding surface on actin to troponin C, triggering movement of troponin-tropomyosin within the thin filament and thereby freeing actin-binding site(s) for interactions with the myosin ATPase of the thick filament to generate the power stroke. The structure of calcium-saturated cardiac troponin C (C-domain) in complex with the inhibitory region of troponin I was determined using multinuclear and multidimensional nuclear magnetic resonance spectroscopy. The structure of this complex reveals that the inhibitory region adopts a helical conformation spanning residues Leu134-Lys139, with a novel orientation between the E- and H-helices of troponin C, which is largely stabilized by electrostatic interactions. By using isotope labeling, we have studied the dynamics of the protein and peptide in the binary complex. The structure of this inhibited complex provides a framework for understanding into interactions within the troponin complex upon Heart Contraction.
