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Chakraborti A, Tardiff JC, Schwartz SD. Myosin-Catalyzed ATP Hydrolysis in the Presence of Disease-Causing Mutations: Mavacamten as a Way to Repair Mechanism. J Phys Chem B 2024; 128:4716-4727. [PMID: 38708944 PMCID: PMC11103257 DOI: 10.1021/acs.jpcb.4c01601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Hypertrophic cardiomyopathy is one of the most common forms of genetic cardiomyopathy. Mavacamten is a first-in-class myosin modulator that was identified via activity screening on the wild type, and it is FDA-approved for the treatment of obstructive hypertrophic cardiomyopathy (HCM). The drug selectively binds to the cardiac β-myosin, inhibiting myosin function to decrease cardiac contractility. Though the drug is thought to affect multiple steps of the myosin cross-bridge cycle, its detailed mechanism of action is still under investigation. Individual steps in the overall cross-bridge cycle must be queried to elucidate the full mechanism of action. In this study, we utilize the rare-event method of transition path sampling to generate reactive trajectories to gain insights into the action of the drug on the dynamics and rate of the ATP hydrolysis step for human cardiac β-myosin. We study three known HCM causative myosin mutations: R453C, P710R, and R712L to observe the effect of the drug on the alterations caused by these mutations in the chemical step. Since the crystal structure of the drug-bound myosin was not available at the time of this work, we created a model of the drug-bound system utilizing a molecular docking approach. We find a significant effect of the drug in one case, where the actual mechanism of the reaction is altered from the wild type by mutation. The drug restores both the rate of hydrolysis to the wildtype level and the mechanism of the reaction. This is a way to check the effect of the drug on untested mutations.
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Affiliation(s)
- Ananya Chakraborti
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85724, United States
| | - Steven D Schwartz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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Krysov VA, Wilson RH, Ten NS, Youlton N, De Jong HN, Sutton S, Huang Y, Reuter CM, Grove ME, Wheeler MT, Ashley EA, Parikh VN. Regional Variation in Cardiovascular Genes Enables a Tractable Genome Editing Strategy. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2024; 17:e004370. [PMID: 38506054 PMCID: PMC11020015 DOI: 10.1161/circgen.123.004370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 03/10/2024] [Indexed: 03/21/2024]
Abstract
BACKGROUND To realize the potential of genome engineering therapeutics, tractable strategies must be identified that balance personalized therapy with the need for off-the-shelf availability. We hypothesized that regional clustering of pathogenic variants can inform the design of rational prime editing therapeutics to treat the majority of genetic cardiovascular diseases with a limited number of reagents. METHODS We collated 2435 high-confidence pathogenic/likely pathogenic (P/LP) variants in 82 cardiovascular disease genes from ClinVar. We assessed the regional density of these variants by defining a regional clustering index. We then combined a highly active base editor with prime editing to demonstrate the feasibility of a P/LP hotspot-directed genome engineering therapeutic strategy in vitro. RESULTS P/LP variants in cardiovascular disease genes display higher regional density than rare variants found in the general population. P/LP missense variants displayed higher average regional density than P/LP truncating variants. Following hypermutagenesis at a pathogenic hotspot, mean prime editing efficiency across introduced variants was 57±27%. CONCLUSIONS Designing therapeutics that target pathogenic hotspots will not only address known missense P/LP variants but also novel P/LP variants identified in these hotspots as well. Moreover, the clustering of P/LP missense rather than truncating variants in these hotspots suggests that prime editing technology is particularly valuable for dominant negative disease. Although prime editing technology in relation to cardiac health continues to improve, this study presents an approach to targeting the most impactful regions of the genome for inherited cardiovascular disease.
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Affiliation(s)
- Vikki A. Krysov
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- University of California, Davis School of Medicine, Sacramento, CA (V.A.K.)
| | - Rachel H. Wilson
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
| | - Nicholas S. Ten
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
| | - Nathan Youlton
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
| | - Hannah N. De Jong
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA (H.N.D.J., E.A.A.)
- Maze Therapeutics, Inc., San Francisco, CA (H.N.D.J.)
| | - Shirley Sutton
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
| | - Yong Huang
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
| | - Chloe M. Reuter
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- Color Health, Burlingame, CA (C.M.R., M.E.G.)
| | | | - Matthew T. Wheeler
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- Stanford Center for Inherited Cardiovascular Disease, Stanford Medicine, CA (M.T.W., E.A.A., V.N.P.)
| | - Euan A. Ashley
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA (H.N.D.J., E.A.A.)
- Stanford Center for Inherited Cardiovascular Disease, Stanford Medicine, CA (M.T.W., E.A.A., V.N.P.)
| | - Victoria N. Parikh
- Division of Cardiovascular Medicine (V.A.K., R.H.W., N.S.T., N.Y., H.N.D.J., S.S., Y.H., C.M.R., M.T.W., E.A.A., V.N.P.)
- Stanford Center for Inherited Cardiovascular Disease, Stanford Medicine, CA (M.T.W., E.A.A., V.N.P.)
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3
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Kawana M, Spudich JA, Ruppel KM. Hypertrophic cardiomyopathy: Mutations to mechanisms to therapies. Front Physiol 2022; 13:975076. [PMID: 36225299 PMCID: PMC9548533 DOI: 10.3389/fphys.2022.975076] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 08/22/2022] [Indexed: 01/10/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) affects more than 1 in 500 people in the general population with an extensive burden of morbidity in the form of arrhythmia, heart failure, and sudden death. More than 25 years since the discovery of the genetic underpinnings of HCM, the field has unveiled significant insights into the primary effects of these genetic mutations, especially for the myosin heavy chain gene, which is one of the most commonly mutated genes. Our group has studied the molecular effects of HCM mutations on human β-cardiac myosin heavy chain using state-of-the-art biochemical and biophysical tools for the past 10 years, combining insights from clinical genetics and structural analyses of cardiac myosin. The overarching hypothesis is that HCM-causing mutations in sarcomere proteins cause hypercontractility at the sarcomere level, and we have shown that an increase in the number of myosin molecules available for interaction with actin is a primary driver. Recently, two pharmaceutical companies have developed small molecule inhibitors of human cardiac myosin to counteract the molecular consequences of HCM pathogenesis. One of these inhibitors (mavacamten) has recently been approved by the FDA after completing a successful phase III trial in HCM patients, and the other (aficamten) is currently being evaluated in a phase III trial. Myosin inhibitors will be the first class of medication used to treat HCM that has both robust clinical trial evidence of efficacy and that targets the fundamental mechanism of HCM pathogenesis. The success of myosin inhibitors in HCM opens the door to finding other new drugs that target the sarcomere directly, as we learn more about the genetics and fundamental mechanisms of this disease.
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Affiliation(s)
- Masataka Kawana
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States,Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, United States
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States,*Correspondence: Kathleen M. Ruppel,
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Radnai L, Surman M, Hafenbreidel M, Young EJ, Stremel RF, Lin L, Bdiri B, Pasetto P, Jin X, Geedy M, Partridge JR, Patel A, Conlon M, Sellers JR, Cameron MD, Rumbaugh G, Griffin PR, Kamenecka TM, Miller CA. Discovery of Selective Inhibitors for In Vitro and In Vivo Interrogation of Skeletal Myosin II. ACS Chem Biol 2021; 16:2164-2173. [PMID: 34558887 DOI: 10.1021/acschembio.1c00067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Myosin IIs, actin-based motors that utilize the chemical energy of adenosine 5'-triphosphate (ATP) to generate force, have potential as therapeutic targets. Their heavy chains differentiate the family into muscle (skeletal [SkMII], cardiac, smooth) and nonmuscle myosin IIs. Despite the therapeutic potential for muscle disorders, SkMII-specific inhibitors have not been reported and characterized. Here, we present the discovery, synthesis, and characterization of "skeletostatins," novel derivatives of the pan-myosin II inhibitor blebbistatin, with selectivity 40- to 170-fold for SkMII over all other myosin II family members. In addition, the skeletostatins bear improved potency, solubility, and photostability, without cytotoxicity. Based on its optimal in vitro profile, MT-134's in vivo tolerability, efficacy, and pharmacokinetics were determined. MT-134 was well-tolerated in mice, impaired motor performance, and had excellent exposure in muscles. Skeletostatins are useful probes for basic research and a strong starting point for drug development.
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Affiliation(s)
- Laszlo Radnai
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Matthew Surman
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Madalyn Hafenbreidel
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Erica J. Young
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Rebecca F. Stremel
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Li Lin
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Bilel Bdiri
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Paolo Pasetto
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Xiaomin Jin
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Mackenzie Geedy
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Joni-Rae Partridge
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Aagam Patel
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - Michael Conlon
- Albany Molecular Research Inc., 26 Corporate Circle, Albany, New York 12212, United States
| | - James R. Sellers
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, 50 South Drive, B50/3529, Bethesda, Maryland 20892-8015, United States
| | - Michael D. Cameron
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Gavin Rumbaugh
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Patrick R. Griffin
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Theodore M. Kamenecka
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Courtney A. Miller
- Department of Molecular Medicine, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States
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5
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Fatkin D, Calkins H, Elliott P, James CA, Peters S, Kovacic JC. Contemporary and Future Approaches to Precision Medicine in Inherited Cardiomyopathies: JACC Focus Seminar 3/5. J Am Coll Cardiol 2021; 77:2551-2572. [PMID: 34016267 DOI: 10.1016/j.jacc.2020.12.072] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/10/2020] [Accepted: 12/18/2020] [Indexed: 01/02/2023]
Abstract
Inherited cardiomyopathies are commonly occurring myocardial disorders that are associated with substantial morbidity and mortality. Clinical management strategies have focused on treatment of heart failure and arrhythmic complications in symptomatic patients according to standardized guidelines. Clinicians are now being urged to implement precision medicine, but what does this involve? Advances in understanding of the genetic underpinnings of inherited cardiomyopathies have brought new possibilities for interventions that are tailored to genes, specific variants, or downstream mechanisms. However, the phenotypic variability that can occur with any given pathogenic variant suggests that factors other than single driver gene mutations are often involved. This is propelling a new imperative to elucidate the nuanced ways in which individual combinations of genetic variation, comorbidities, and lifestyle may influence cardiomyopathy phenotypes. Here, Part 3 of a 5-part precision medicine Focus Seminar series reviews the current status and future opportunities for precision medicine in the inherited cardiomyopathies.
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Affiliation(s)
- Diane Fatkin
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Kensington, New South Wales, Australia; Cardiology Department, St. Vincent's Hospital, Darlinghurst, New South Wales, Australia.
| | - Hugh Calkins
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Perry Elliott
- Institute of Cardiovascular Sciences, University College London, London, United Kingdom; Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom
| | - Cynthia A James
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Stacey Peters
- Departments of Cardiology and Genomic Medicine, Royal Melbourne Hospital, Melbourne, Victoria, Australia; Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
| | - Jason C Kovacic
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Kensington, New South Wales, Australia; Cardiology Department, St. Vincent's Hospital, Darlinghurst, New South Wales, Australia; The Zena and Michael A. Wiener Cardiovascular Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
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6
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Li Y, Yi J, Liu W, Liu Y, Liu J. Gaining insight into cellular cardiac physiology using single particle tracking. J Mol Cell Cardiol 2020; 148:63-77. [PMID: 32871158 DOI: 10.1016/j.yjmcc.2020.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 11/29/2022]
Abstract
Single particle tracking (SPT) is a robust technique to monitor single-molecule behaviors in living cells directly. By this approach, we can uncover the potential biological significance of particle dynamics by statistically characterizing individual molecular behaviors. SPT provides valuable information at the single-molecule level, that could be obscured by simple averaging that is inherent to conventional ensemble measurements. Here, we give a brief introduction to SPT including the commonly used optical implementations, fluorescence labeling strategies, and data analysis methods. We then focus on how SPT has been harnessed to decipher myocardial function. In this context, SPT has provided novel insight into the lateral diffusion of signal receptors and ion channels, the dynamic organization of cardiac nanodomains, subunit composition and stoichiometry of cardiac ion channels, myosin movement along actin filaments, the kinetic features of transcription factors involved in cardiac remodeling, and the intercellular communication by nanotubes. Finally, we speculate on the prospects and challenges of applying SPT to future questions regarding cellular cardiac physiology using SPT.
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Affiliation(s)
- Ying Li
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, 518060, China.
| | - Jing Yi
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, 518060, China.
| | - Wenjuan Liu
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, 518060, China.
| | - Yun Liu
- The Seventh Affiliated Hospital, Sun Yat-sen University, Guangdong Province, China.
| | - Jie Liu
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, 518060, China.
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7
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Muir WW, Hamlin RL. Myocardial Contractility: Historical and Contemporary Considerations. Front Physiol 2020; 11:222. [PMID: 32296340 PMCID: PMC7137917 DOI: 10.3389/fphys.2020.00222] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/26/2020] [Indexed: 12/17/2022] Open
Abstract
The term myocardial contractility is thought to have originated more than 125 years ago and has remained and enigma ever since. Although the term is frequently used in textbooks, editorials and contemporary manuscripts its definition remains illusive often being conflated with cardiac performance or inotropy. The absence of a universally accepted definition has led to confusion, disagreement and misconceptions among physiologists, cardiologists and safety pharmacologists regarding its definition particularly in light of new discoveries regarding the load dependent kinetics of cardiac contraction and their translation to cardiac force-velocity and ventricular pressure-volume measurements. Importantly, the Starling interpretation of force development is length-dependent while contractility is length independent. Most historical definitions employ an operational approach and define cardiac contractility in terms of the hearts mechanical properties independent of loading conditions. Literally defined the term contract infers that something has become smaller, shrunk or shortened. The addition of the suffix “ility” implies the quality of this process. The discovery and clinical investigation of small molecules that bind to sarcomeric proteins independently altering force or velocity requires that a modern definition of the term myocardial contractility be developed if the term is to persist. This review reconsiders the historical and contemporary interpretations of the terms cardiac performance and inotropy and recommends a modern definition of myocardial contractility as the preload, afterload and length-independent intrinsic kinetically controlled, chemo-mechanical processes responsible for the development of force and velocity.
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Affiliation(s)
- William W Muir
- College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, United States
| | - Robert L Hamlin
- College of Veterinary Medicine, The Ohio State University, Columbus, OH, United States
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8
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Yotti R, Seidman CE, Seidman JG. Advances in the Genetic Basis and Pathogenesis of Sarcomere Cardiomyopathies. Annu Rev Genomics Hum Genet 2019; 20:129-153. [PMID: 30978303 DOI: 10.1146/annurev-genom-083118-015306] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are common heart muscle disorders that are caused by pathogenic variants in sarcomere protein genes. HCM is characterized by unexplained cardiac hypertrophy (increased chamber wall thickness) that is accompanied by enhanced cardiac contractility and impaired relaxation. DCM is defined as increased ventricular chamber volume with contractile impairment. In this review, we discuss recent analyses that provide new insights into the molecular mechanisms that cause these conditions. HCM studies have uncovered the critical importance of conformational changes that occur during relaxation and enable energy conservation, which are frequently disturbed by HCM mutations. DCM studies have demonstrated the considerable prevalence of truncating variants in titin and have discerned that these variants reduce contractile function by impairing sarcomerogenesis. These new pathophysiologic mechanisms open exciting opportunities to identify new pharmacological targets and develop future cardioprotective strategies.
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Affiliation(s)
- Raquel Yotti
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; .,Centro de Investigación Biomédica en Red en Enfermedades Cardiovasculares (CIBERCV), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Christine E Seidman
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; , .,Cardiovascular Division and Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Jonathan G Seidman
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; ,
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Overexpression and purification of human myosins from transiently and stably transfected suspension adapted HEK293SF-3F6 cells. Anal Biochem 2018; 558:19-27. [PMID: 30075102 DOI: 10.1016/j.ab.2018.07.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 07/30/2018] [Accepted: 07/30/2018] [Indexed: 12/11/2022]
Abstract
The myosin family of motor proteins is an attractive target of therapeutic small-molecule protein inhibitors and modulators. Milligrams of protein quantities are required to conduct proper biophysical and biochemical studies to understand myosin functions. Myosin protein expression and purification represent a critical starting point towards this goal. Established utilization of Dictyostelium discoideum, Drosophila melanogaster, insect and mouse cells for myosin expression and purification is limited, cost, labor and time inefficient particularly for (full-length) human myosins. Here we are presenting detailed protocols for production of several difficult-to-purify recombinant human myosins in efficient quantities up to 1 mg of protein per liter of cell culture. This is the first time that myosins have been purified in large scales from suspension adapted transiently and stably expressing human cells. The method is also useful for expressing other human proteins in quantities sufficient to perform extensive biochemical and biophysical characterization.
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10
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The Molecular Mechanisms of Mutations in Actin and Myosin that Cause Inherited Myopathy. Int J Mol Sci 2018; 19:ijms19072020. [PMID: 29997361 PMCID: PMC6073311 DOI: 10.3390/ijms19072020] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 07/06/2018] [Accepted: 07/08/2018] [Indexed: 12/23/2022] Open
Abstract
The discovery that mutations in myosin and actin genes, together with mutations in the other components of the muscle sarcomere, are responsible for a range of inherited muscle diseases (myopathies) has revolutionized the study of muscle, converting it from a subject of basic science to a relevant subject for clinical study and has been responsible for a great increase of interest in muscle studies. Myopathies are linked to mutations in five of the myosin heavy chain genes, three of the myosin light chain genes, and three of the actin genes. This review aims to determine to what extent we can explain disease phenotype from the mutant genotype. To optimise our chances of finding the right mechanism we must study a myopathy where there are a large number of different mutations that cause a common phenotype and so are likely to have a common mechanism: a corollary to this criterion is that if any mutation causes the disease phenotype but does not correspond to the proposed mechanism, then the whole mechanism is suspect. Using these criteria, we consider two cases where plausible genotype-phenotype mechanisms have been proposed: the actin “A-triad” and the myosin “mesa/IHD” models.
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11
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Kelly MA, Caleshu C, Morales A, Buchan J, Wolf Z, Harrison SM, Cook S, Dillon MW, Garcia J, Haverfield E, Jongbloed JDH, Macaya D, Manrai A, Orland K, Richard G, Spoonamore K, Thomas M, Thomson K, Vincent LM, Walsh R, Watkins H, Whiffin N, Ingles J, van Tintelen JP, Semsarian C, Ware JS, Hershberger R, Funke B. Adaptation and validation of the ACMG/AMP variant classification framework for MYH7-associated inherited cardiomyopathies: recommendations by ClinGen's Inherited Cardiomyopathy Expert Panel. Genet Med 2018; 20:351-359. [PMID: 29300372 PMCID: PMC5876064 DOI: 10.1038/gim.2017.218] [Citation(s) in RCA: 238] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 10/24/2017] [Indexed: 01/20/2023] Open
Abstract
Purpose Integrating genomic sequencing in clinical care requires standardization of variant interpretation practices. The Clinical Genome Resource has established expert panels to adapt the American College of Medical Genetics and Genomics/Association for Molecular Pathology classification framework for specific genes and diseases. The Cardiomyopathy Expert Panel selected MYH7, a key contributor to inherited cardiomyopathies, as a pilot gene to develop a broadly applicable approach. Methods Expert revisions were tested with 60 variants using a structured double review by pairs of clinical and diagnostic laboratory experts. Final consensus rules were established via iterative discussions. Results Adjustments represented disease-/gene-informed specifications (12) or strength adjustments of existing rules (5). Nine rules were deemed not applicable. Key specifications included quantitative frameworks for minor allele frequency thresholds, the use of segregation data, and a semiquantitative approach to counting multiple independent variant occurrences where fully controlled case-control studies are lacking. Initial inter-expert classification concordance was 93%. Internal data from participating diagnostic laboratories changed the classification of 20% of the variants (n = 12), highlighting the critical importance of data sharing. Conclusion These adapted rules provide increased specificity for use in MYH7-associated disorders in combination with expert review and clinical judgment and serve as a stepping stone for genes and disorders with similar genetic and clinical characteristics.
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Affiliation(s)
- Melissa A Kelly
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA
| | - Colleen Caleshu
- Stanford Center for Inherited Cardiovascular Disease, Stanford University, Stanford, California, USA
| | - Ana Morales
- Division of Human Genetics, Department of Internal Medicine, Ohio State University, Columbus, Ohio, USA
| | - Jillian Buchan
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA
| | - Zena Wolf
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA
| | - Steven M Harrison
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA
| | - Stuart Cook
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Mitchell W Dillon
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA
| | - John Garcia
- Invitae Inc., San Francisco, California, USA
| | | | - Jan D H Jongbloed
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | | | - Arjun Manrai
- Harvard School of Public Health, Boston, Massachusetts, USA
| | - Kate Orland
- Clinical Science Center, University of Wisconsin, Madison, Wisconsin, USA
| | | | - Katherine Spoonamore
- Krannert Institute of Cardiology, Indiana University, Indianapolis, Indiana, USA
| | - Matthew Thomas
- Division of Genetics, Department of Pediatrics, University of Virginia, Charlottesville, Virginia, USA
| | - Kate Thomson
- Oxford Medical Genetics Laboratory, Oxford University Hospitals NHS Foundation Trust, The Churchill Hospital, Oxford, UK.,Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | | | - Roddy Walsh
- National Heart and Lung Institute, Imperial College London, London, UK.,Royal Brompton & Harefield Hospitals NHS Trust, London, UK
| | - Hugh Watkins
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Nicola Whiffin
- National Heart and Lung Institute, Imperial College London, London, UK.,Royal Brompton & Harefield Hospitals NHS Trust, London, UK
| | - Jodie Ingles
- Agnes Ginges Centre for Molecular Cardiology, Centenary Institute and University of Sydney, Sydney, Australia
| | - J Peter van Tintelen
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Christopher Semsarian
- Agnes Ginges Centre for Molecular Cardiology, Centenary Institute and University of Sydney, Sydney, Australia
| | - James S Ware
- National Heart and Lung Institute, Imperial College London, London, UK.,Royal Brompton & Harefield Hospitals NHS Trust, London, UK
| | - Ray Hershberger
- Division of Human Genetics, Department of Internal Medicine, Ohio State University, Columbus, Ohio, USA
| | - Birgit Funke
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Boston, Massachusetts, USA.,Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
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12
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Trivedi DV, Adhikari AS, Sarkar SS, Ruppel KM, Spudich JA. Hypertrophic cardiomyopathy and the myosin mesa: viewing an old disease in a new light. Biophys Rev 2017; 10:27-48. [PMID: 28717924 PMCID: PMC5803174 DOI: 10.1007/s12551-017-0274-6] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 06/12/2017] [Indexed: 12/15/2022] Open
Abstract
The sarcomere is an exquisitely designed apparatus that is capable of generating force, which in the case of the heart results in the pumping of blood throughout the body. At the molecular level, an ATP-dependent interaction of myosin with actin drives the contraction and force generation of the sarcomere. Over the past six decades, work on muscle has yielded tremendous insights into the workings of the sarcomeric system. We now stand on the cusp where the acquired knowledge of how the sarcomere contracts and how that contraction is regulated can be extended to an understanding of the molecular mechanisms of sarcomeric diseases, such as hypertrophic cardiomyopathy (HCM). In this review we present a picture that combines current knowledge of the myosin mesa, the sequestered state of myosin heads on the thick filament, known as the interacting-heads motif (IHM), their possible interaction with myosin binding protein C (MyBP-C) and how these interactions can be abrogated leading to hyper-contractility, a key clinical manifestation of HCM. We discuss the structural and functional basis of the IHM state of the myosin heads and identify HCM-causing mutations that can directly impact the equilibrium between the 'on state' of the myosin heads (the open state) and the IHM 'off state'. We also hypothesize a role of MyBP-C in helping to maintain myosin heads in the IHM state on the thick filament, allowing release in a graded manner upon adrenergic stimulation. By viewing clinical hyper-contractility as the result of the destabilization of the IHM state, our aim is to view an old disease in a new light.
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Affiliation(s)
- Darshan V Trivedi
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Arjun S Adhikari
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Saswata S Sarkar
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA. .,Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA, 94305, USA.
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
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13
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Childers MC, Daggett V. Insights from molecular dynamics simulations for computational protein design. MOLECULAR SYSTEMS DESIGN & ENGINEERING 2017; 2:9-33. [PMID: 28239489 PMCID: PMC5321087 DOI: 10.1039/c6me00083e] [Citation(s) in RCA: 127] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A grand challenge in the field of structural biology is to design and engineer proteins that exhibit targeted functions. Although much success on this front has been achieved, design success rates remain low, an ever-present reminder of our limited understanding of the relationship between amino acid sequences and the structures they adopt. In addition to experimental techniques and rational design strategies, computational methods have been employed to aid in the design and engineering of proteins. Molecular dynamics (MD) is one such method that simulates the motions of proteins according to classical dynamics. Here, we review how insights into protein dynamics derived from MD simulations have influenced the design of proteins. One of the greatest strengths of MD is its capacity to reveal information beyond what is available in the static structures deposited in the Protein Data Bank. In this regard simulations can be used to directly guide protein design by providing atomistic details of the dynamic molecular interactions contributing to protein stability and function. MD simulations can also be used as a virtual screening tool to rank, select, identify, and assess potential designs. MD is uniquely poised to inform protein design efforts where the application requires realistic models of protein dynamics and atomic level descriptions of the relationship between dynamics and function. Here, we review cases where MD simulations was used to modulate protein stability and protein function by providing information regarding the conformation(s), conformational transitions, interactions, and dynamics that govern stability and function. In addition, we discuss cases where conformations from protein folding/unfolding simulations have been exploited for protein design, yielding novel outcomes that could not be obtained from static structures.
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Affiliation(s)
| | - Valerie Daggett
- Corresponding author: , Phone: 1.206.685.7420, Fax: 1.206.685.3300
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14
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Tang W, Blair CA, Walton SD, Málnási-Csizmadia A, Campbell KS, Yengo CM. Modulating Beta-Cardiac Myosin Function at the Molecular and Tissue Levels. Front Physiol 2017; 7:659. [PMID: 28119616 PMCID: PMC5220080 DOI: 10.3389/fphys.2016.00659] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 12/15/2016] [Indexed: 01/10/2023] Open
Abstract
Inherited cardiomyopathies are a common form of heart disease that are caused by mutations in sarcomeric proteins with beta cardiac myosin (MYH7) being one of the most frequently affected genes. Since the discovery of the first cardiomyopathy associated mutation in beta-cardiac myosin, a major goal has been to correlate the in vitro myosin motor properties with the contractile performance of cardiac muscle. There has been substantial progress in developing assays to measure the force and velocity properties of purified cardiac muscle myosin but it is still challenging to correlate results from molecular and tissue-level experiments. Mutations that cause hypertrophic cardiomyopathy are more common than mutations that lead to dilated cardiomyopathy and are also often associated with increased isometric force and hyper-contractility. Therefore, the development of drugs designed to decrease isometric force by reducing the duty ratio (the proportion of time myosin spends bound to actin during its ATPase cycle) has been proposed for the treatment of hypertrophic cardiomyopathy. Para-Nitroblebbistatin is a small molecule drug proposed to decrease the duty ratio of class II myosins. We examined the impact of this drug on human beta cardiac myosin using purified myosin motor assays and studies of permeabilized muscle fiber mechanics. We find that with purified human beta-cardiac myosin para-Nitroblebbistatin slows actin-activated ATPase and in vitro motility without altering the ADP release rate constant. In permeabilized human myocardium, para-Nitroblebbistatin reduces isometric force, power, and calcium sensitivity while not changing shortening velocity or the rate of force development (ktr). Therefore, designing a drug that reduces the myosin duty ratio by inhibiting strong attachment to actin while not changing detachment can cause a reduction in force without changing shortening velocity or relaxation.
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Affiliation(s)
- Wanjian Tang
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine Hershey, PA, USA
| | - Cheavar A Blair
- Department of Physiology, University of Kentucky Lexington, KY, USA
| | - Shane D Walton
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine Hershey, PA, USA
| | | | - Kenneth S Campbell
- Department of Physiology, University of KentuckyLexington, KY, USA; Division of Cardiovascular Medicine, University of KentuckyLexington, KY, USA
| | - Christopher M Yengo
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine Hershey, PA, USA
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15
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Spudich JA, Aksel T, Bartholomew SR, Nag S, Kawana M, Yu EC, Sarkar SS, Sung J, Sommese RF, Sutton S, Cho C, Adhikari AS, Taylor R, Liu C, Trivedi D, Ruppel KM. Effects of hypertrophic and dilated cardiomyopathy mutations on power output by human β-cardiac myosin. ACTA ACUST UNITED AC 2016; 219:161-7. [PMID: 26792326 DOI: 10.1242/jeb.125930] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hypertrophic cardiomyopathy is the most frequently occurring inherited cardiovascular disease, with a prevalence of more than one in 500 individuals worldwide. Genetically acquired dilated cardiomyopathy is a related disease that is less prevalent. Both are caused by mutations in the genes encoding the fundamental force-generating protein machinery of the cardiac muscle sarcomere, including human β-cardiac myosin, the motor protein that powers ventricular contraction. Despite numerous studies, most performed with non-human or non-cardiac myosin, there is no clear consensus about the mechanism of action of these mutations on the function of human β-cardiac myosin. We are using a recombinantly expressed human β-cardiac myosin motor domain along with conventional and new methodologies to characterize the forces and velocities of the mutant myosins compared with wild type. Our studies are extending beyond myosin interactions with pure actin filaments to include the interaction of myosin with regulated actin filaments containing tropomyosin and troponin, the roles of regulatory light chain phosphorylation on the functions of the system, and the possible roles of myosin binding protein-C and titin, important regulatory components of both cardiac and skeletal muscles.
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Affiliation(s)
- James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Tural Aksel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sadie R Bartholomew
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Suman Nag
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Masataka Kawana
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Elizabeth Choe Yu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Saswata S Sarkar
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jongmin Sung
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ruth F Sommese
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Shirley Sutton
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Carol Cho
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Arjun S Adhikari
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Rebecca Taylor
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Chao Liu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Darshan Trivedi
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA 94305, USA
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16
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Cao H, Kang BJ, Lee CA, Shung KK, Hsiai TK. Electrical and Mechanical Strategies to Enable Cardiac Repair and Regeneration. IEEE Rev Biomed Eng 2015; 8:114-24. [PMID: 25974948 DOI: 10.1109/rbme.2015.2431681] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inadequate replacement of lost ventricular myocardium from myocardial infarction leads to heart failure. Investigating the regenerative capacity of mammalian hearts represents an emerging direction for tissue engineering and cell-based therapy. Recent advances in stem cells hold promise to restore cardiac functions. However, embryonic or induced pluripotent stem cell-derived cardiomyocytes lack functional phenotypes of the native myocardium, and transplanted tissues are not fully integrated for synchronized electrical and mechanical coupling with the host. In this context, this review highlights the mechanical and electrical strategies to promote cardiomyocyte maturation and integration, and to assess the functional phenotypes of regenerating myocardium. Simultaneous microelectrocardiogram and high-frequency ultrasound techniques will also be introduced to assess electrical and mechanical coupling for small animal models of heart regeneration.
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17
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Aksel T, Choe Yu E, Sutton S, Ruppel KM, Spudich JA. Ensemble force changes that result from human cardiac myosin mutations and a small-molecule effector. Cell Rep 2015; 11:910-920. [PMID: 25937279 PMCID: PMC4431957 DOI: 10.1016/j.celrep.2015.04.006] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/19/2015] [Accepted: 04/01/2015] [Indexed: 11/24/2022] Open
Abstract
Cardiomyopathies due to mutations in human β-cardiac myosin are a significant cause of heart failure, sudden death, and arrhythmia. To understand the underlying molecular basis of changes in the contractile system's force production due to such mutations and search for potential drugs that restore force generation, an in vitro assay is necessary to evaluate cardiac myosin's ensemble force using purified proteins. Here, we characterize the ensemble force of human α- and β-cardiac myosin isoforms and those of β-cardiac myosins carrying left ventricular non-compaction (M531R) and dilated cardiomyopathy (S532P) mutations using a utrophin-based loaded in vitro motility assay and new filament-tracking software. Our results show that human α- and β-cardiac myosin, as well as the mutants, show opposite mechanical and enzymatic phenotypes with respect to each other. We also show that omecamtiv mecarbil, a previously discovered cardiac-specific myosin activator, increases β-cardiac myosin force generation.
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Affiliation(s)
- Tural Aksel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Elizabeth Choe Yu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA; Cancer Biology Program, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Shirley Sutton
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
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18
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Gaber EM, Jayaprakash P, Qureshi MA, Parekh K, Oz M, Adrian TE, Howarth FC. Effects of a sucrose-enriched diet on the pattern of gene expression, contraction and Ca(2+) transport in Goto-Kakizaki type 2 diabetic rat heart. Exp Physiol 2014; 99:881-93. [PMID: 24681897 DOI: 10.1113/expphysiol.2013.077594] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
There has been a spectacular rise in the global prevalence of type 2 diabetes mellitus (T2DM), and cardiovascular disease is the major cause of morbidity and mortality in diabetic patients. A variety of diastolic and systolic dysfunctions have been demonstrated in type 2 diabetic heart. The consumption of sugar-sweetened beverages has been linked to rising rates of obesity, which in turn is a risk factor for development of T2DM. In this study, the effects of a sucrose-enriched diet on the pattern of gene expression, contraction and Ca(2+) transport in the Goto-Kakizaki T2DM rat heart were investigated. Genes encoding cardiac muscle proteins (Myh7, Mybpc3, Myl1, Myl3 and Mylpf), intercellular proteins (Gja4), cell membrane transport (Atp1b1), calcium channels (Cacna1c, Cacna1g and Cacnb1) and potassium channels (Kcnj11) were upregulated and genes encoding potassium channels (Kcnb1) were downregulated in GK compared with control rats. Genes encoding cardiac muscle proteins (Myh6, Mybpc3 and Tnn2), intercellular proteins (Gja1 and Gja4), intracellular Ca(2+) transport (Atp2a1 and Ryr2), cell membrane transport (Atp1a2 and Atp1b1) and potassium channel proteins (Kcnj2 and Kcnj8) were upregulated and genes encoding cardiac muscle proteins (Myh7) were downregulated in control rats fed sucrose compared with control rats. Genes encoding cardiac muscle proteins (Myh7) and potassium channel proteins (Kcnj11) were downregulated in control and GK rats fed sucrose compared with control and GK rats, respectively. The amplitude of shortening was reduced in myocytes from the control-sucrose group compared with control rats and in the GK-sucrose group compared with GK rats. The amplitude of the Ca(2+) transient was increased in myocytes from control-sucrose compared with control rats and decreased in GK-sucrose compared with GK rats. Subtle alterations in the pattern of expression of genes encoding a variety of cardiac muscle proteins are associated with changes in shortening and intracellular Ca(2+) transport in ventricular myocytes from GK T2DM and control rats fed a sucrose-enriched diet.
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Affiliation(s)
- E M Gaber
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - P Jayaprakash
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - M A Qureshi
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - K Parekh
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - M Oz
- Department of Pharmacology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - T E Adrian
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - F C Howarth
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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19
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Sommese RF, Nag S, Sutton S, Miller SM, Spudich JA, Ruppel KM. Effects of troponin T cardiomyopathy mutations on the calcium sensitivity of the regulated thin filament and the actomyosin cross-bridge kinetics of human β-cardiac myosin. PLoS One 2013; 8:e83403. [PMID: 24367593 PMCID: PMC3867432 DOI: 10.1371/journal.pone.0083403] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/13/2013] [Indexed: 11/20/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) lead to significant cardiovascular morbidity and mortality worldwide. Mutations in the genes encoding the sarcomere, the force-generating unit in the cardiomyocyte, cause familial forms of both HCM and DCM. This study examines two HCM-causing (I79N, E163K) and two DCM-causing (R141W, R173W) mutations in the troponin T subunit of the troponin complex using human β-cardiac myosin. Unlike earlier reports using various myosin constructs, we found that none of these mutations affect the maximal sliding velocities or maximal Ca2+-activated ADP release rates involving the thin filament human β-cardiac myosin complex. Changes in Ca2+ sensitivity using the human myosin isoform do, however, mimic changes seen previously with non-human myosin isoforms. Transient kinetic measurements show that these mutations alter the kinetics of Ca2+ induced conformational changes in the regulatory thin filament proteins. These changes in calcium sensitivity are independent of active, cycling human β-cardiac myosin.
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Affiliation(s)
- Ruth F. Sommese
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, United States of America
| | - Suman Nag
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, United States of America
| | - Shirley Sutton
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, United States of America
| | - Susan M. Miller
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail: (KR); (JS)
| | - Kathleen M. Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail: (KR); (JS)
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20
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Taylor RE, Kim K, Sun N, Park SJ, Sim JY, Fajardo G, Bernstein D, Wu JC, Pruitt BL. Sacrificial layer technique for axial force post assay of immature cardiomyocytes. Biomed Microdevices 2013; 15:171-81. [PMID: 23007494 PMCID: PMC3545035 DOI: 10.1007/s10544-012-9710-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Immature primary and stem cell-derived cardiomyocytes provide useful models for fundamental studies of heart development and cardiac disease, and offer potential for patient specific drug testing and differentiation protocols aimed at cardiac grafts. To assess their potential for augmenting heart function, and to gain insight into cardiac growth and disease, tissue engineers must quantify the contractile forces of these single cells. Currently, axial contractile forces of isolated adult heart cells can only be measured by two-point methods such as carbon fiber techniques, which cannot be applied to neonatal and stem cell-derived heart cells because they are more difficult to handle and lack a persistent shape. Here we present a novel axial technique for measuring the contractile forces of isolated immature cardiomyocytes. We overcome cell manipulation and patterning challenges by using a thermoresponsive sacrificial support layer in conjunction with arrays of widely separated elastomeric microposts. Our approach has the potential to be high-throughput, is functionally analogous to current gold-standard axial force assays for adult heart cells, and prescribes elongated cell shapes without protein patterning. Finally, we calibrate these force posts with piezoresistive cantilevers to dramatically reduce measurement error typical for soft polymer-based force assays. We report quantitative measurements of peak contractile forces up to 146 nN with post stiffness standard error (26 nN) far better than that based on geometry and stiffness estimates alone. The addition of sacrificial layers to future 2D and 3D cell culture platforms will enable improved cell placement and the complex suspension of cells across 3D constructs.
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Affiliation(s)
- Rebecca E Taylor
- Department of Mechanical Engineering and Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305, USA
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21
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Lakdawala NK, Thune JJ, Colan SD, Cirino AL, Farrohi F, Rivero J, McDonough B, Sparks E, Orav EJ, Seidman JG, Seidman CE, Ho CY. Subtle abnormalities in contractile function are an early manifestation of sarcomere mutations in dilated cardiomyopathy. ACTA ACUST UNITED AC 2012; 5:503-10. [PMID: 22949430 DOI: 10.1161/circgenetics.112.962761] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Sarcomere mutations cause both dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM); however, the steps leading from mutation to disease are not well described. By studying mutation carriers before a clinical diagnosis develops, we characterize the early manifestations of sarcomere mutations in DCM and investigate how these manifestations differ from sarcomere mutations associated with HCM. METHODS AND RESULTS Sixty-two genotyped individuals in families with sarcomeric DCM underwent clinical evaluation including strain echocardiography. The group included 12 subclinical DCM mutation carriers with normal cardiac dimensions and left ventricular ejection fraction (LVEF ≥55%), 21 overt DCM subjects, and 29 related mutation (-) normal controls. Results were compared with a previously characterized cohort of 60 subclinical HCM subjects (sarcomere mutation carriers without left ventricular hypertrophy). Systolic myocardial tissue velocity, longitudinal, circumferential, and radial strain, and longitudinal and radial strain rate were reduced by 10%-23% in subclinical DCM mutation carriers compared with controls (P<0.001 for all comparisons), after adjusting for age and family relations. No significant differences in diastolic parameters were identified comparing the subclinical and control cohorts. The opposite pattern of contractile abnormalities with reduced diastolic but preserved systolic function was seen in subclinical HCM. CONCLUSIONS Subtle abnormalities in systolic function are present in subclinical DCM mutation carriers, despite normal left ventricular size and ejection fraction. In contrast, impaired relaxation and preserved systolic function appear to be the predominant early manifestations of sarcomere mutations that lead to HCM. These findings support the theory that the mutation's intrinsic impact on sarcomere function influences whether a dilated or hypertrophic phenotype develops.
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Affiliation(s)
- Neal K Lakdawala
- Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA
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22
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Chuan P, Sivaramakrishnan S, Ashley EA, Spudich JA. Cell-intrinsic functional effects of the α-cardiac myosin Arg-403-Gln mutation in familial hypertrophic cardiomyopathy. Biophys J 2012; 102:2782-90. [PMID: 22735528 DOI: 10.1016/j.bpj.2012.04.049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 04/02/2012] [Accepted: 04/13/2012] [Indexed: 01/27/2023] Open
Abstract
Human familial hypertrophic cardiomyopathy is the most common Mendelian cardiovascular disease worldwide. Among the most severe presentations of the disease are those in families heterozygous for the mutation R403Q in β-cardiac myosin. Mice heterozygous for this mutation in the α-cardiac myosin isoform display typical familial hypertrophic cardiomyopathy pathology. Here, we study cardiomyocytes from heterozygous 403/+ mice. The effects of the R403Q mutation on force-generating capabilities and dynamics of cardiomyocytes were investigated using a dual carbon nanofiber technique to measure single-cell parameters. We demonstrate the Frank-Starling effect at the single cardiomyocyte level by showing that cell stretch causes an increase in amplitude of contraction. Mutant 403/+ cardiomyocytes exhibit higher end-diastolic and end-systolic stiffness than +/+ cardiomyocytes, whereas active force generation capabilities remain unchanged. Additionally, 403/+ cardiomyocytes show slowed relaxation dynamics. These phenotypes are consistent with increased end-diastolic and end-systolic chamber elastance, as well as diastolic dysfunction seen at the level of the whole heart. Our results show that these functional effects of the R403Q mutation are cell-intrinsic, a property that may be a general phenomenon in familial hypertrophic cardiomyopathy.
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Affiliation(s)
- Peiying Chuan
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA
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23
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Moscoso I, Rodriguez-Barbosa JI, Barallobre-Barreiro J, Anon P, Domenech N. Immortalization of bone marrow-derived porcine mesenchymal stem cells and their differentiation into cells expressing cardiac phenotypic markers. J Tissue Eng Regen Med 2011; 6:655-65. [PMID: 22162515 DOI: 10.1002/term.469] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 03/31/2011] [Accepted: 07/05/2011] [Indexed: 11/07/2022]
Abstract
Mesenchymal stem cells (MSCs) may be among the first stem cell types to be utilized in the clinic for cell therapy, because of their ease of isolation and extensive differentiation potential. Using a porcine model, we have established several cell lines from MSCs to facilitate in vitro and in vivo studies of their potential use for cellular therapy. Bone marrow-derived primary MSCs were immortalized using the pRNS-1 plasmid. We obtained four stable immortalized cell lines that exhibited higher proliferative capacities than the parental cells. All four cell lines displayed a common phenotype similar to that of primary mesenchymal cells, characterized by constitutively high expressions of CD90, CD29, CD44, SLA I and CD46, while CD172a, CD106 and CD56 were less expressed. Remarkably, treatment with 5-azacytidine-stimulated porcine MSCs lines to differentiate into cells that were positive for cardiac phenotypic markers, such as α-actin, connexin-43, sarcomeric actin, serca-2 and, to a lesser extent, desmin and troponin-T. These porcine MSC lines will be valuable biological tools for developing strategies for ex vivo expansion and differentiation of MSCs into a specific lineage.
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Affiliation(s)
- Isabel Moscoso
- Unidad de Investigación, INIBIC-Complejo Universitario Universitario A Coruña, Spain
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How do mutations in contractile proteins cause the primary familial cardiomyopathies? J Cardiovasc Transl Res 2011; 4:245-55. [PMID: 21424860 DOI: 10.1007/s12265-011-9266-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 02/17/2011] [Indexed: 01/11/2023]
Abstract
In this article, the available evidence about the functional effects of the contractile protein mutations that cause hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) is assessed. The molecular mechanism of the contractile apparatus of cardiac muscle and its regulation by Ca(2+) and PKA phosphorylation have been extensively studied. Therefore, when a number of point mutations in the contractile protein genes were found to cause the well-defined phenotypes of HCM and DCM, it was expected that the diseases could be explained at the molecular level. However, the search for a distinctive molecular phenotype did not yield rapid results. Now that a substantial number of mutations that cause HCM or DCM have been investigated in physiologically relevant systems and with a range of experimental techniques, a pattern is emerging. In the case of HCM, the hypothesis that the major effect of mutations is to increase myofibrillar Ca(2+)-sensitivity seems to be well established, but the mechanisms by which an increase in myofibrillar Ca(2+)-sensitivity induces hypertrophy remain obscure. In contrast, DCM mutations are not correlated with a specific effect on Ca(2+)-sensitivity. It has recently been proposed that DCM mutations uncouple troponin I phosphorylation from Ca(2+)-sensitivity changes, albeit based on only a few mutations so far. A plausible link between uncoupling and DCM has been proposed via blunting of the response to α-adrenergic stimulation.
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Abstract
This review provides an historical and personal perspective on the discovery of genetic causes for hypertrophic cardiomyopathy (HCM). Extraordinary insights by physicians who initially detailed remarkable and varied manifestations of the disorder, collaboration among multidisciplinary teams with skills in clinical diagnostics and molecular genetics, and hard work by scores of trainees solved the etiologic riddle of HCM and unexpectedly demonstrated mutations in sarcomere protein genes as the cause of disease. In addition to celebrating 20 years of genetic research in HCM, this article serves as an introductory overview to a thematic review series that will present contemporary advances in the field of hypertrophic heart disease. Through the continued application of advances in genetic methodologies, combined with biochemical and biophysical analyses of the consequences of human mutations, fundamental knowledge about HCM and sarcomere biology has emerged. Expanding research to elucidate the mechanisms by which subtle genetic variation in contractile proteins remodel the human heart remains an exciting opportunity, one with considerable promise to provide new strategies to limit or even prevent HCM pathogenesis.
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Affiliation(s)
- Christine E Seidman
- Cardiovascular Division, Department of Genetics, Brigham & Women's Hospital, Boston, MA 02115, USA.
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