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Aboonabi A, McCauley MD. Myofilament dysfunction in diastolic heart failure. Heart Fail Rev 2024; 29:79-93. [PMID: 37837495 PMCID: PMC10904515 DOI: 10.1007/s10741-023-10352-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/18/2023] [Indexed: 10/16/2023]
Abstract
Diastolic heart failure (DHF), in which impaired ventricular filling leads to typical heart failure symptoms, represents over 50% of all heart failure cases and is linked with risk factors, including metabolic syndrome, hypertension, diabetes, and aging. A substantial proportion of patients with this disorder maintain normal left ventricular systolic function, as assessed by ejection fraction. Despite the high prevalence of DHF, no effective therapeutic agents are available to treat this condition, partially because the molecular mechanisms of diastolic dysfunction remain poorly understood. As such, by focusing on the underlying molecular and cellular processes contributing to DHF can yield new insights that can represent an exciting new avenue and propose a novel therapeutic approach for DHF treatment. This review discusses new developments from basic and clinical/translational research to highlight current knowledge gaps, help define molecular determinants of diastolic dysfunction, and clarify new targets for treatment.
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Affiliation(s)
- Anahita Aboonabi
- Division of Cardiology, Department of Medicine, College of Medicine, University of Illinois at Chicago, 840 S. Wood St., 920S (MC 715), Chicago, IL, 60612, USA.
- Jesse Brown VA Medical Center, Chicago, IL, USA.
| | - Mark D McCauley
- Division of Cardiology, Department of Medicine, College of Medicine, University of Illinois at Chicago, 840 S. Wood St., 920S (MC 715), Chicago, IL, 60612, USA.
- Jesse Brown VA Medical Center, Chicago, IL, USA.
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
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2
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Marston S. Recent studies of the molecular mechanism of lusitropy due to phosphorylation of cardiac troponin I by protein kinase A. J Muscle Res Cell Motil 2023; 44:201-208. [PMID: 36131171 PMCID: PMC10541847 DOI: 10.1007/s10974-022-09630-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/28/2022] [Indexed: 10/14/2022]
Abstract
Ca2+ acts on troponin and tropomyosin to switch the thin filament on and off, however in cardiac muscle a more graded form of regulation is essential to tailor cardiac output to the body's needs. This is achieved by the action of adrenaline on β1 receptors of heart muscle cells leading to enhanced contractility, faster heart rate and faster relaxation (lusitropy) via activation of the cyclic AMP-dependent protein kinase, PKA. PKA phosphorylates serines 22 and 23 in the N-terminal peptide of cardiac troponin I. As a consequence the rate of Ca2+release from troponin is increased. This is the key determinant of lusitropy. The molecular mechanism of this process has remained unknown long after the mechanism of the troponin Ca2+ switch itself was defined. Investigation of this subtle process at the atomic level poses a challenge, since the change in Ca2+-sensitivity is only about twofold and key parts of the troponin modulation and regulation system are disordered and cannot be fully resolved by conventional structural approaches. We will review recent studies using molecular dynamics simulations together with functional, cryo-em and NMR techniques that have started to give us a precise picture of how phosphorylation of troponin I modulates the dynamics of troponin to produce the lusitropic effect.
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3
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Marston S, Pinto JR. Suppression of lusitropy as a disease mechanism in cardiomyopathies. Front Cardiovasc Med 2023; 9:1080965. [PMID: 36698941 PMCID: PMC9870330 DOI: 10.3389/fcvm.2022.1080965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/19/2022] [Indexed: 01/11/2023] Open
Abstract
In cardiac muscle the action of adrenaline on β1 receptors of heart muscle cells is essential to adjust cardiac output to the body's needs. Adrenergic activation leads to enhanced contractility (inotropy), faster heart rate (chronotropy) and faster relaxation (lusitropy), mainly through activation of protein kinase A (PKA). Efficient enhancement of heart output under stress requires all of these responses to work together. Lusitropy is essential for shortening the heartbeat when heart rate increases. It therefore follows that, if the lusitropic response is not present, heart function under stress will be compromised. Current literature suggests that lusitropy is primarily achieved due to PKA phosphorylation of troponin I (TnI) and phospholamban (PLB). It has been well documented that PKA-induced phosphorylation of TnI releases Ca2+ from troponin C faster and increases the rate of cardiac muscle relaxation, while phosphorylation of PLB increases SERCA activity, speeding up Ca2+ removal from the cytoplasm. In this review we consider the current scientific evidences for the connection between suppression of lusitropy and cardiac dysfunction in the context of mutations in phospholamban and thin filament proteins that are associated with cardiomyopathies. We will discuss what advances have been made into understanding the physiological mechanism of lusitropy due to TnI and PLB phosphorylation and its suppression by mutations and we will evaluate the evidence whether lack of lusitropy is sufficient to cause cardiomyopathy, and under what circumstances, and consider the range of pathologies associated with loss of lusitropy. Finally, we will discuss whether suppressed lusitropy due to mutations in thin filament proteins can be therapeutically restored.
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Affiliation(s)
- Steven Marston
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, United States
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Keyt LK, Duran JM, Bui QM, Chen C, Miyamoto MI, Silva Enciso J, Tardiff JC, Adler ED. Thin filament cardiomyopathies: A review of genetics, disease mechanisms, and emerging therapeutics. Front Cardiovasc Med 2022; 9:972301. [PMID: 36158814 PMCID: PMC9489950 DOI: 10.3389/fcvm.2022.972301] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 07/28/2022] [Indexed: 11/17/2022] Open
Abstract
All muscle contraction occurs due to the cyclical interaction between sarcomeric thin and thick filament proteins within the myocyte. The thin filament consists of the proteins actin, tropomyosin, Troponin C, Troponin I, and Troponin T. Mutations in these proteins can result in various forms of cardiomyopathy, including hypertrophic, restrictive, and dilated phenotypes and account for as many as 30% of all cases of inherited cardiomyopathy. There is significant evidence that thin filament mutations contribute to dysregulation of Ca2+ within the sarcomere and may have a distinct pathomechanism of disease from cardiomyopathy associated with thick filament mutations. A number of distinct clinical findings appear to be correlated with thin-filament mutations: greater degrees of restrictive cardiomyopathy and relatively less left ventricular (LV) hypertrophy and LV outflow tract obstruction than that seen with thick filament mutations, increased morbidity associated with heart failure, increased arrhythmia burden and potentially higher mortality. Most therapies that improve outcomes in heart failure blunt the neurohormonal pathways involved in cardiac remodeling, while most therapies for hypertrophic cardiomyopathy involve use of negative inotropes to reduce LV hypertrophy or septal reduction therapies to reduce LV outflow tract obstruction. None of these therapies directly address the underlying sarcomeric dysfunction associated with thin-filament mutations. With mounting evidence that thin filament cardiomyopathies occur through a distinct mechanism, there is need for therapies targeting the unique, underlying mechanisms tailored for each patient depending on a given mutation.
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Affiliation(s)
- Lucas K. Keyt
- Department of Internal Medicine, University of California, San Diego, San Diego, CA, United States
| | - Jason M. Duran
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Quan M. Bui
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Chao Chen
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | | | - Jorge Silva Enciso
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Jil C. Tardiff
- Department of Medicine and Biomedical Engineering, University of Arizona, Tucson, AZ, United States
| | - Eric D. Adler
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
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5
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Bhagwan JR, Mosqueira D, Chairez-Cantu K, Mannhardt I, Bodbin SE, Bakar M, Smith JGW, Denning C. Isogenic models of hypertrophic cardiomyopathy unveil differential phenotypes and mechanism-driven therapeutics. J Mol Cell Cardiol 2020; 145:43-53. [PMID: 32531470 PMCID: PMC7487780 DOI: 10.1016/j.yjmcc.2020.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/18/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is a prevalent and complex cardiovascular condition. Despite being strongly associated with genetic alterations, wide variation of disease penetrance, expressivity and hallmarks of progression complicate treatment. We aimed to characterize different human isogenic cellular models of HCM bearing patient-relevant mutations to clarify genetic causation and disease mechanisms, hence facilitating the development of effective therapeutics. METHODS We directly compared the p.β-MHC-R453C and p.ACTC1-E99K HCM-associated mutations in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and their healthy isogenic counterparts, generated using CRISPR/Cas9 genome editing technology. By harnessing several state-of-the-art HCM phenotyping techniques, these mutations were investigated to identify similarities and differences in disease progression and hypertrophic signaling pathways, towards establishing potential targets for pharmacological treatment. CRISPR/Cas9 knock-in of the genetically-encoded calcium indicator R-GECO1.0 to the AAVS1 locus into these disease models resulted in calcium reporter lines. RESULTS Confocal line scan analysis identified calcium transient arrhythmias and intracellular calcium overload in both models. The use of optogenetics and 2D/3D contractility assays revealed opposing phenotypes in the two mutations. Gene expression analysis highlighted upregulation of CALM1, CASQ2 and CAMK2D, and downregulation of IRF8 in p.β-MHC-R453C mutants, whereas the opposite changes were detected in p.ACTC1-E99K mutants. Contrasting profiles of nuclear translocation of NFATc1 and MEF2 between the two HCM models suggest differential hypertrophic signaling pathway activation. Calcium transient abnormalities were rescued with combination of dantrolene and ranolazine, whilst mavacamten reduced the hyper-contractile phenotype of p.ACTC1-E99K hiPSC-CMs. CONCLUSIONS Our data show that hypercontractility and molecular signaling within HCM are not uniform between different gene mutations, suggesting that a 'one-size fits all' treatment underestimates the complexity of the disease. Understanding where the similarities (arrhythmogenesis, bioenergetics) and differences (contractility, molecular profile) lie will allow development of therapeutics that are directed towards common mechanisms or tailored to each disease variant, hence providing effective patient-specific therapy.
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Affiliation(s)
- Jamie R Bhagwan
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Diogo Mosqueira
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Karolina Chairez-Cantu
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Ingra Mannhardt
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, and DZHK (German Center for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Sara E Bodbin
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Mine Bakar
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - James G W Smith
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK; Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia,NR4 7UQ, UK
| | - Chris Denning
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
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6
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Parker F, Baboolal TG, Peckham M. Actin Mutations and Their Role in Disease. Int J Mol Sci 2020; 21:ijms21093371. [PMID: 32397632 PMCID: PMC7247010 DOI: 10.3390/ijms21093371] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 12/15/2022] Open
Abstract
Actin is a widely expressed protein found in almost all eukaryotic cells. In humans, there are six different genes, which encode specific actin isoforms. Disease-causing mutations have been described for each of these, most of which are missense. Analysis of the position of the resulting mutated residues in the protein reveals mutational hotspots. Many of these occur in regions important for actin polymerization. We briefly discuss the challenges in characterizing the effects of these actin mutations, with a focus on cardiac actin mutations.
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Copeland O, Messer A, Jabbour A, Poggesi C, Prasad S, Marston S. Pressure Overload Is Associated With Low Levels of Troponin I and Myosin Binding Protein C Phosphorylation in the Hearts of Patients With Aortic Stenosis. Front Physiol 2020; 11:241. [PMID: 32265736 PMCID: PMC7096377 DOI: 10.3389/fphys.2020.00241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/02/2020] [Indexed: 12/21/2022] Open
Abstract
In previous studies of septal heart muscle from HCM patients with hypertrophic obstructive cardiomyopathy (HOCM, LVOT gradient 50-120 mmHg) we found that the level of phosphorylation of troponin I (TnI) and myosin binding protein C (MyBP-C) was extremely low yet samples from hearts with HCM or DCM mutations that did not have pressure overload were similar to donor heart controls. We therefore investigated heart muscle samples taken from patients undergoing valve replacement for aortic stenosis, since they have pressure overload that is unrelated to inherited cardiomyopathy. Thirteen muscle samples from septum and from free wall were analyzed (LVOT gradients 30-100 mmHg) The levels of TnI and MyBP-C phosphorylation were determined in muscle myofibrils by separating phosphospecies using phosphate affinity SDS-PAGE and detecting with TnI and MyBP-C specific antibodies. TnI was predominantly monophosphorylated and total phosphorylation was 0.85 ± 0.03 molsPi/mol TnI. This phosphorylation level was significantly different (p < 0.0001) from both donor heart TnI (1.6 ± 0.06 molsPi/mol TnI) and HOCM heart TnI (0.19 ± 0.04 molsPi/mol TnI). MyBP-C is phosphorylated at up to four sites. In donor heart the 4P and 3P species predominate but in the pressure overload samples the 4P species was much reduced and 3P and 1P species predominated. Total phosphorylation was 2.0 ± 0.2 molsPi/mol MyBP-C (n = 8) compared with 3.4 ± 0.07 (n = 21) in donor heart and 1.1 ± 0.1 (n = 10) in HOCM heart. We conclude that pressure overload may be associated with substantial dephosphorylation of troponin I and MyBP-C.
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Affiliation(s)
| | | | - Andrew Jabbour
- Royal Brompton Hospital, and Imperial College London, London, United Kingdom
| | | | - Sanjay Prasad
- Royal Brompton Hospital, and Imperial College London, London, United Kingdom
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8
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Teng GZ, Shaikh Z, Liu H, Dawson JF. M-class hypertrophic cardiomyopathy cardiac actin mutations increase calcium sensitivity of regulated thin filaments. Biochem Biophys Res Commun 2019; 519:148-152. [PMID: 31481237 DOI: 10.1016/j.bbrc.2019.08.151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 08/27/2019] [Indexed: 12/22/2022]
Abstract
Hypertrophic cardiomyopathy is a commonly occurring cardiovascular disease resulting primarily from changes in proteins participating in muscle contraction in the heart, including the cardiac actin protein. Changes in cardiac actin located exclusively in the myosin binding site are called M-class variants and include the H88Y, R95C, and E99K substitutions and F90Δ deletion. The prevailing hypothesis for these mutations is that hypertrophic cardiomyopathy is the result of increased calcium sensitivity of contraction in the myocardium. To test this hypothesis, we studied the activity of myosin at varying calcium concentrations in the presence of regulated thin filaments containing M-class cardiac actin variants. We found that all M-class cardiac actin variants exhibit increased calcium sensitivity, with the R95C variant also displaying significant decreases in maximal myosin activity. This work represents the first characterization of all M-class variant proteins and suggests that drugs targeting contraction specifically to treat hypertrophic cardiomyopathy must consider the impact on both calcium sensitivity and maximal myosin activity on overall heart health.
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Affiliation(s)
- Grace Zi Teng
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Zeeshan Shaikh
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Haidun Liu
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - John F Dawson
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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9
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Mosqueira D, Smith JGW, Bhagwan JR, Denning C. Modeling Hypertrophic Cardiomyopathy: Mechanistic Insights and Pharmacological Intervention. Trends Mol Med 2019; 25:775-790. [PMID: 31324451 DOI: 10.1016/j.molmed.2019.06.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/12/2019] [Accepted: 06/18/2019] [Indexed: 02/06/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is a prevalent and complex cardiovascular disease where cardiac dysfunction often associates with mutations in sarcomeric genes. Various models based on tissue explants, isolated cardiomyocytes, skinned myofibrils, and purified actin/myosin preparations have uncovered disease hallmarks, enabling the development of putative therapeutics, with some reaching clinical trials. Newly developed human pluripotent stem cell (hPSC)-based models could be complementary by overcoming some of the inconsistencies of earlier systems, whilst challenging and/or clarifying previous findings. In this article we compare recent progress in unveiling multiple HCM mechanisms in different models, highlighting similarities and discrepancies. We explore how insight is facilitating the design of new HCM therapeutics, including those that regulate metabolism, contraction and heart rhythm, providing a future perspective for treatment of HCM.
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Affiliation(s)
- Diogo Mosqueira
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
| | - James G W Smith
- Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7UQ, UK
| | - Jamie R Bhagwan
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Chris Denning
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
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10
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Kagemoto T, Oyama K, Yamane M, Tsukamoto S, Kobirumaki-Shimozawa F, Li A, Dos Remedios C, Fukuda N, Ishiwata S. Sarcomeric Auto-Oscillations in Single Myofibrils From the Heart of Patients With Dilated Cardiomyopathy. Circ Heart Fail 2019; 11:e004333. [PMID: 29980594 DOI: 10.1161/circheartfailure.117.004333] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 05/31/2018] [Indexed: 01/30/2023]
Abstract
BACKGROUND Left ventricular wall motion is depressed in patients with dilated cardiomyopathy (DCM). However, whether or not the depressed left ventricular wall motion is caused by impairment of sarcomere dynamics remains to be fully clarified. METHODS AND RESULTS We analyzed the mechanical properties of single sarcomere dynamics during sarcomeric auto-oscillations (calcium spontaneous oscillatory contractions [Ca-SPOC]) that occurred at partial activation under the isometric condition in myofibrils from donor hearts and from patients with severe DCM (New York Heart Association classification III-IV). Ca-SPOC reproducibly occurred in the presence of 1 μmol/L free Ca2+ in both nonfailing and DCM myofibrils, and sarcomeres exhibited a saw-tooth waveform along single myofibrils composed of quick lengthening and slow shortening. The period of Ca-SPOC was longer in DCM myofibrils than in nonfailing myofibrils, in association with prolonged shortening time. Lengthening time was similar in both groups. Then, we performed Tn (troponin) exchange in myofibrils with a DCM-causing homozygous mutation (K36Q) in cTnI (cardiac TnI). On exchange with the Tn complex from healthy porcine ventricles, period, shortening time, and shortening velocity in cTnI-K36Q myofibrils became similar to those in Tn-reconstituted nonfailing myofibrils. Protein kinase A abbreviated period in both Tn-reconstituted nonfailing and cTnI-K36Q myofibrils, demonstrating acceleration of cross-bridge kinetics. CONCLUSIONS Sarcomere dynamics was found to be depressed under loaded conditions in DCM myofibrils because of impairment of thick-thin filament sliding. Thus, microscopic analysis of Ca-SPOC in human cardiac myofibrils is beneficial to systematically unveil the kinetic properties of single sarcomeres in various types of heart disease.
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Affiliation(s)
- Tatsuya Kagemoto
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.)
| | - Kotaro Oyama
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Mitsunori Yamane
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.)
| | - Seiichi Tsukamoto
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Fuyu Kobirumaki-Shimozawa
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.)
| | - Amy Li
- School of Medical Sciences, Bosch Institute, The University of Sydney, Australia (A.L., C.D.R.)
| | - Cristobal Dos Remedios
- School of Medical Sciences, Bosch Institute, The University of Sydney, Australia (A.L., C.D.R.)
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan (K.O., S.T., F.K.-S., N.F.).
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan (T.K., M.Y., S.I.).
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11
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Fiedler LR, Chapman K, Xie M, Maifoshie E, Jenkins M, Golforoush PA, Bellahcene M, Noseda M, Faust D, Jarvis A, Newton G, Paiva MA, Harada M, Stuckey DJ, Song W, Habib J, Narasimhan P, Aqil R, Sanmugalingam D, Yan R, Pavanello L, Sano M, Wang SC, Sampson RD, Kanayaganam S, Taffet GE, Michael LH, Entman ML, Tan TH, Harding SE, Low CMR, Tralau-Stewart C, Perrior T, Schneider MD. MAP4K4 Inhibition Promotes Survival of Human Stem Cell-Derived Cardiomyocytes and Reduces Infarct Size In Vivo. Cell Stem Cell 2019; 24:579-591.e12. [PMID: 30853557 PMCID: PMC6458995 DOI: 10.1016/j.stem.2019.01.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/24/2018] [Accepted: 01/30/2019] [Indexed: 12/17/2022]
Abstract
Heart disease is a paramount cause of global death and disability. Although cardiomyocyte death plays a causal role and its suppression would be logical, no clinical counter-measures target the responsible intracellular pathways. Therapeutic progress has been hampered by lack of preclinical human validation. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is activated in failing human hearts and relevant rodent models. Using human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) and MAP4K4 gene silencing, we demonstrate that death induced by oxidative stress requires MAP4K4. Consequently, we devised a small-molecule inhibitor, DMX-5804, that rescues cell survival, mitochondrial function, and calcium cycling in hiPSC-CMs. As proof of principle that drug discovery in hiPSC-CMs may predict efficacy in vivo, DMX-5804 reduces ischemia-reperfusion injury in mice by more than 50%. We implicate MAP4K4 as a well-posed target toward suppressing human cardiac cell death and highlight the utility of hiPSC-CMs in drug discovery to enhance cardiomyocyte survival.
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Affiliation(s)
- Lorna R Fiedler
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Kathryn Chapman
- Drug Discovery Centre, Department of Medicine, Imperial College London, London SW7 2AZ, UK; Department of Surgery and Cancer, Imperial College London, London W12 0NN, UK; Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Min Xie
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Evie Maifoshie
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Micaela Jenkins
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Pelin Arabacilar Golforoush
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Mohamed Bellahcene
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Michela Noseda
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Dörte Faust
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Ashley Jarvis
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Gary Newton
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Marta Abreu Paiva
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Mutsuo Harada
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Daniel J Stuckey
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Weihua Song
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Josef Habib
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Priyanka Narasimhan
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Rehan Aqil
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Devika Sanmugalingam
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Robert Yan
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Lorenzo Pavanello
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Motoaki Sano
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sam C Wang
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Robert D Sampson
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Sunthar Kanayaganam
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - George E Taffet
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lloyd H Michael
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Mark L Entman
- Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Tse-Hua Tan
- Immunology Research Center, National Health Research Institutes, Zhunan 35053, Taiwan; Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sian E Harding
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Caroline M R Low
- Drug Discovery Centre, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | | | - Trevor Perrior
- Domainex, Chesterford Research Park, Little Chesterford, Saffron Walden, Essex CB10 1XL, UK
| | - Michael D Schneider
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London W12 0NN, UK; Michael E. DeBakey Heart Center, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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12
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Hayashi Y, Ono K, Ono S. Mutations in Caenorhabditis elegans actin, which are equivalent to human cardiomyopathy mutations, cause abnormal actin aggregation in nematode striated muscle. F1000Res 2019; 8:279. [PMID: 30984387 PMCID: PMC6446495 DOI: 10.12688/f1000research.18476.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/08/2019] [Indexed: 01/19/2023] Open
Abstract
Actin is a central component of muscle contractile apparatuses, and a number of actin mutations cause diseases in skeletal, cardiac, and smooth muscles. However, many pathogenic actin mutations have not been characterized at cell biological and physiological levels. In this study, we tested whether the nematode Caenorhabditis elegans could be used to characterize properties of actin mutants in muscle cells in vivo. Two representative actin mutations, E99K and P164A, which cause hypertrophic cardiomyopathy in humans, are introduced in a muscle-specific C. elegans actin ACT-4 as E100K and P165A, respectively. When green fluorescent protein-tagged wild-type ACT-4 (GFP-ACT-4), is transgenically expressed in muscle at low levels as compared with endogenous actin, it is incorporated into sarcomeres without disturbing normal structures. GFP-ACT-4 variants with E100K and P165A are incorporated into sarcomeres, but also accumulated in abnormal aggregates, which have not been reported for equivalent actin mutations in previous studies. Muscle contractility, as determined by worm motility, is not apparently affected by expression of ACT-4 mutants. Our results suggest that C. elegans muscle is a useful model system to characterize abnormalities caused by actin mutations.
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Affiliation(s)
- Yuriko Hayashi
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
| | - Kanako Ono
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
| | - Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
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13
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Smith JGW, Owen T, Bhagwan JR, Mosqueira D, Scott E, Mannhardt I, Patel A, Barriales-Villa R, Monserrat L, Hansen A, Eschenhagen T, Harding SE, Marston S, Denning C. Isogenic Pairs of hiPSC-CMs with Hypertrophic Cardiomyopathy/LVNC-Associated ACTC1 E99K Mutation Unveil Differential Functional Deficits. Stem Cell Reports 2018; 11:1226-1243. [PMID: 30392975 PMCID: PMC6235010 DOI: 10.1016/j.stemcr.2018.10.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 10/04/2018] [Accepted: 10/05/2018] [Indexed: 12/14/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a primary disorder of contractility in heart muscle. To gain mechanistic insight and guide pharmacological rescue, this study models HCM using isogenic pairs of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the E99K-ACTC1 cardiac actin mutation. In both 3D engineered heart tissues and 2D monolayers, arrhythmogenesis was evident in all E99K-ACTC1 hiPSC-CMs. Aberrant phenotypes were most common in hiPSC-CMs produced from the heterozygote father. Unexpectedly, pathological phenotypes were less evident in E99K-expressing hiPSC-CMs from the two sons. Mechanistic insight from Ca2+ handling expression studies prompted pharmacological rescue experiments, wherein dual dantroline/ranolazine treatment was most effective. Our data are consistent with E99K mutant protein being a central cause of HCM but the three-way interaction between the primary genetic lesion, background (epi)genetics, and donor patient age may influence the pathogenic phenotype. This illustrates the value of isogenic hiPSC-CMs in genotype-phenotype correlations.
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Affiliation(s)
- James G W Smith
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK; Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7UQ, UK.
| | - Thomas Owen
- National Heart and Lung Institute, Imperial College, London W12 0NN, UK
| | - Jamie R Bhagwan
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Diogo Mosqueira
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Elizabeth Scott
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Ingra Mannhardt
- Institute of Experimental Pharmacology and Toxicology, University Medical Centre, Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Asha Patel
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK; Department of Gene Therapy, National Heart and Lung Institute, Imperial College London SW3 6LR, UK
| | - Roberto Barriales-Villa
- Inherited Cardiovascular Diseases Unit, Cardiology Service, Complexo Hospitalario Universitario A Coruña, Servizo Galego de Saúde (SERGAS), Universidade da Coruña, A Coruña, Spain; Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Lorenzo Monserrat
- Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain; Health in Code S.L., Cardiology Department, A Coruña, Spain
| | - Arne Hansen
- Institute of Experimental Pharmacology and Toxicology, University Medical Centre, Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Thomas Eschenhagen
- Institute of Experimental Pharmacology and Toxicology, University Medical Centre, Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Sian E Harding
- National Heart and Lung Institute, Imperial College, London W12 0NN, UK
| | - Steve Marston
- National Heart and Lung Institute, Imperial College, London W12 0NN, UK
| | - Chris Denning
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
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14
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Vikhorev PG, Vikhoreva NN. Cardiomyopathies and Related Changes in Contractility of Human Heart Muscle. Int J Mol Sci 2018; 19:ijms19082234. [PMID: 30065175 PMCID: PMC6121228 DOI: 10.3390/ijms19082234] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 07/22/2018] [Accepted: 07/27/2018] [Indexed: 02/07/2023] Open
Abstract
About half of hypertrophic and dilated cardiomyopathies cases have been recognized as genetic diseases with mutations in sarcomeric proteins. The sarcomeric proteins are involved in cardiomyocyte contractility and its regulation, and play a structural role. Mutations in non-sarcomeric proteins may induce changes in cell signaling pathways that modify contractile response of heart muscle. These facts strongly suggest that contractile dysfunction plays a central role in initiation and progression of cardiomyopathies. In fact, abnormalities in contractile mechanics of myofibrils have been discovered. However, it has not been revealed how these mutations increase risk for cardiomyopathy and cause the disease. Much research has been done and still much is being done to understand how the mechanism works. Here, we review the facts of cardiac myofilament contractility in patients with cardiomyopathy and heart failure.
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Affiliation(s)
- Petr G Vikhorev
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK.
| | - Natalia N Vikhoreva
- Heart Science Centre, Magdi Yacoub Institute, Harefield Hospital, London UB9 6JH, UK.
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15
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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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16
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Despond EA, Dawson JF. Classifying Cardiac Actin Mutations Associated With Hypertrophic Cardiomyopathy. Front Physiol 2018; 9:405. [PMID: 29719515 PMCID: PMC5913282 DOI: 10.3389/fphys.2018.00405] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 04/04/2018] [Indexed: 11/13/2022] Open
Abstract
Mutations in the cardiac actin gene (ACTC1) are associated with the development of hypertrophic cardiomyopathy (HCM). To date, 12 different ACTC1 mutations have been discovered in patients with HCM. Given the high degree of sequence conservation of actin proteins and the range of protein–protein interactions actin participates in, mutations in cardiac actin leading to HCM are particularly interesting. Here, we suggest the classification of ACTC1 mutations based on the location of the resulting amino acid change in actin into three main groups: (1) those affecting only the binding site of the myosin molecular motor, termed M-class mutations, (2) those affecting only the binding site of the tropomyosin (Tm) regulatory protein, designated T-class mutations, and (3) those affecting both the myosin- and Tm-binding sites, called MT-class mutations. To understand the precise pathogenesis of cardiac actin mutations and develop treatments specific to the molecular cause of disease, we need to integrate rapidly growing structural information with studies of regulated actomyosin systems.
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Affiliation(s)
- Evan A Despond
- Department of Molecular and Cellular Biology, Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, Canada
| | - John F Dawson
- Department of Molecular and Cellular Biology, Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, Canada
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17
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Sheehan A, Messer AE, Papadaki M, Choudhry A, Kren V, Biedermann D, Blagg B, Khandelwal A, Marston SB. Molecular Defects in Cardiac Myofilament Ca 2+-Regulation Due to Cardiomyopathy-Linked Mutations Can Be Reversed by Small Molecules Binding to Troponin. Front Physiol 2018; 9:243. [PMID: 29636697 PMCID: PMC5881522 DOI: 10.3389/fphys.2018.00243] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 03/06/2018] [Indexed: 12/28/2022] Open
Abstract
The inherited cardiomyopathies, hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are relatively common, potentially life-threatening and currently untreatable. Mutations are often in the contractile proteins of cardiac muscle and cause abnormal Ca2+ regulation via troponin. HCM is usually linked to higher myofilament Ca2+-sensitivity whilst in both HCM and DCM mutant tissue there is often an uncoupling of the relationship between troponin I (TnI) phosphorylation by PKA and modulation of myofilament Ca2+-sensitivity, essential for normal responses to adrenaline. The adrenergic response is blunted, and this may predispose the heart to failure under stress. At present there are no compounds or interventions that can prevent or treat sarcomere cardiomyopathies. There is a need for novel therapies that act at a more fundamental level to affect the disease process. We demonstrated that epigallocatechin-3 gallate (EGCG) was found to be capable of restoring the coupled relationship between Ca2+-sensitivity and TnI phosphorylation in mutant thin filaments to normal in vitro, independent of the mutation (15 mutations tested). We have labeled this property "re-coupling." The action of EGCG in vitro to reverse the abnormality caused by myopathic mutations would appear to be an ideal pharmaceutical profile for treatment of inherited HCM and DCM but EGCG is known to be promiscuous in vivo and is thus unsuitable as a therapeutic drug. We therefore investigated whether other structurally related compounds can re-couple myofilaments without these off-target effects. We used the quantitative in vitro motility assay to screen 40 compounds, related to C-terminal Hsp90 inhibitors, and found 23 that can re-couple mutant myofilaments. There is no correlation between re-couplers and Hsp90 inhibitors. The Ca2+-sensitivity shift due to TnI phosphorylation was restored to 2.2 ± 0.01-fold (n = 19) compared to 2.0 ± 0.24-fold (n = 7) in wild-type thin filaments. Many of these compounds were either pure re-couplers or pure desensitizers, indicating these properties are independent; moreover, re-coupling ability could be lost with small changes of compound structure, indicating the possibility of specificity. Small molecules that can re-couple may have therapeutic potential. HIGHLIGHTS - Inherited cardiomyopathies are common diseases that are currently untreatable at a fundamental level and therefore finding a small molecule treatment is highly desirable.- We have identified a molecular level dysfunction common to nearly all mutations: uncoupling of the relationship between troponin I phosphorylation and modulation of myofilament Ca2+-sensitivity, essential for normal responses to adrenaline.- We have identified a new class of drugs that are capable of both reducing Ca2+-sensitivity and/or recouping the relationship between troponin I phosphorylation and Ca2+-sensitivity.- The re-coupling phenomenon can be explained on the basis of a single mechanism that is testable.- Measurements with a wide range of small molecules of varying structures can indicate the critical molecular features required for recoupling and allows the prediction of other potential re-couplers.
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Affiliation(s)
- Alice Sheehan
- NHLI, Imperial College London, London, United Kingdom
| | | | | | | | - Vladimír Kren
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - David Biedermann
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Brian Blagg
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, United States
| | - Anuj Khandelwal
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, United States
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18
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Wang L, Bai F, Zhang Q, Song W, Messer A, Kawai M. Development of apical hypertrophic cardiomyopathy with age in a transgenic mouse model carrying the cardiac actin E99K mutation. J Muscle Res Cell Motil 2018; 38:421-435. [PMID: 29582353 DOI: 10.1007/s10974-018-9492-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/12/2018] [Indexed: 10/17/2022]
Abstract
In both humans and mice, the Glu-99-Lys (E99K) mutation in the cardiac actin gene (ACTC) results in little understood apical hypertrophic cardiomyopathy (AHCM). To determine how cross-bridge kinetics change with AHCM development, we applied sinusoidal length perturbations to skinned papillary muscle fibres from 2- and 5-month old E99K transgenic (Tg) and non-transgenic (NTg) mice, and studied tension and its transients. These age groups were chosen because our preliminary studies indicated that AHCM develops with age. Fibres from 5-month old E99K mice showed significant decreases in tension, stiffness, the rate of the medium-speed exponential process and its magnitude compared to non-transgenic control. The nucleotide association constants increased with age, and they were significantly larger in E99K compared to NTg. However, there were no large differences in the rates of the cross-bridge detachment step, the rates of the force generation step, or the phosphate association constant. Our result on force/cross-bridge demonstrates that the decreased active tension of E99K fibres was caused by a decreased amount of force generated per each cross-bridge. The effects were generally less or insignificant at 2 months. A pCa-tension study showed increased Ca2+-sensitivity (pCa50) with age in both the E99K and NTg sample groups, and pCa50 was significantly larger (but only for 0.05-0.06 pCa units) in E99K than in NTg groups. A significant decrease in cooperativity (nH) was observed only in 5-month old E99K mice. We conclude that the AHCM-causing ACTC E99K mutation is associated with progressive alterations in biomechanical parameters, with changes smaller at 2 months but larger at 5 months, correlating with the development of AHCM.
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Affiliation(s)
- Li Wang
- School of Nursing, Medical College, Soochow University, Suzhou, 215006, Jiangsu, China.,Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Fan Bai
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Qing Zhang
- School of Nursing, Medical College, Soochow University, Suzhou, 215006, Jiangsu, China
| | - Weihua Song
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Andrew Messer
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA, 52242, USA.
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19
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Kondrashov A, Duc Hoang M, Smith JGW, Bhagwan JR, Duncan G, Mosqueira D, Munoz MB, Vo NTN, Denning C. Simplified Footprint-Free Cas9/CRISPR Editing of Cardiac-Associated Genes in Human Pluripotent Stem Cells. Stem Cells Dev 2018; 27:391-404. [PMID: 29402189 PMCID: PMC5882176 DOI: 10.1089/scd.2017.0268] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Modeling disease with human pluripotent stem cells (hPSCs) is hindered because the impact on cell phenotype from genetic variability between individuals can be greater than from the pathogenic mutation. While “footprint-free” Cas9/CRISPR editing solves this issue, existing approaches are inefficient or lengthy. In this study, a simplified PiggyBac strategy shortened hPSC editing by 2 weeks and required one round of clonal expansion and genotyping rather than two, with similar efficiencies to the longer conventional process. Success was shown across four cardiac-associated loci (ADRB2, GRK5, RYR2, and ACTC1) by genomic cleavage and editing efficiencies of 8%–93% and 8%–67%, respectively, including mono- and/or biallelic events. Pluripotency was retained, as was differentiation into high-purity cardiomyocytes (CMs; 88%–99%). Using the GRK5 isogenic lines as an exemplar, chronic stimulation with the β-adrenoceptor agonist, isoprenaline, reduced beat rate in hPSC-CMs expressing GRK5-Q41 but not GRK5-L41; this was reversed by the β-blocker, propranolol. This shortened, footprint-free approach will be useful for mechanistic studies.
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Affiliation(s)
- Alexander Kondrashov
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Minh Duc Hoang
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - James G W Smith
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Jamie R Bhagwan
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Gary Duncan
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Diogo Mosqueira
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Maria Barbadillo Munoz
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Nguyen T N Vo
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
| | - Chris Denning
- Department of Stem Cell Biology, Centre of Biomolecular Sciences, University of Nottingham , Nottingham, United Kingdom
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20
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Rowlands CT, Owen T, Lawal S, Cao S, Pandey SS, Yang HY, Song W, Wilkinson R, Alvarez-Laviada A, Gehmlich K, Marston SB, MacLeod KT. Age- and strain-related aberrant Ca 2+ release is associated with sudden cardiac death in the ACTC E99K mouse model of hypertrophic cardiomyopathy. Am J Physiol Heart Circ Physiol 2017; 313:H1213-H1226. [PMID: 28887330 DOI: 10.1152/ajpheart.00244.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patients with hypertrophic cardiomyopathy, particularly young adults, can die from arrhythmia, but the mechanism underlying abnormal rhythm formation remains unknown. C57Bl6 × CBA/Ca mice carrying a cardiac actin ( ACTC) E99K (Glu99Lys) mutation reproduce many aspects of human hypertrophic cardiomyopathy, including increased myofilament Ca2+ sensitivity and sudden death in a proportion (up to 40%) of young (28-40 day old) animals. We studied the hearts of transgenic (TG; ACTC E99K) mice and their non-TG (NTG) littermates when they were in their vulnerable period (28-40 days old) and when they were adult (8-12 wk old). Ventricular myocytes were isolated from the hearts of TG and NTG mice at these two time points. We also examined the hearts of mice that died suddenly (SCD). SCD animals had approximately four times more collagen compared with age-matched NTG mice, yet myocyte cell size was normal. Young TG mice had double the collagen content of NTG mice. Contraction and Ca2+ transients were greater in cells from young TG mice compared with their NTG littermates but not in cells from adult mice (TG or NTG). Cells from young TG mice had a greater propensity for Ca2+ waves than NTG littermates, and, despite similar sarcoplasmic reticulum Ca2+ content, a proportion of these cells had larger Ca2+ spark mass. We found that the probability of SCD in young TG mice was increased when the mutation was expressed in animals with a CBA/Ca2+ background and almost eliminated in mice bred on a C57Bl6 background. The latter TG mice had normal cellular Ca2+ homeostasis. NEW & NOTEWORTHY Mice with the actin Glu99Lys hypertrophic cardiomyopathy mutation ( ACTC E99K) are prone to sudden cardiac death around 40 days, associated with increased Ca2+ transients, spark mass, and fibrosis. However, adult survivors have normal Ca2+ transients and spark density accompanied by hypertrophy. Penetrance of the sudden cardiac death phenotype depends on the genetic background of the mouse. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/calcium-regulation-in-e99k-mouse-heart/ .
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Affiliation(s)
- Christina T Rowlands
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Thomas Owen
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Saheed Lawal
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Shuangyi Cao
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Samata S Pandey
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Hsiang-Yu Yang
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Weihua Song
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Ross Wilkinson
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Anita Alvarez-Laviada
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Katja Gehmlich
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Steven B Marston
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Kenneth T MacLeod
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
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21
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Wang L, Kazmierczak K, Yuan CC, Yadav S, Kawai M, Szczesna-Cordary D. Cardiac contractility, motor function, and cross-bridge kinetics in N47K-RLC mutant mice. FEBS J 2017; 284:1897-1913. [PMID: 28467684 DOI: 10.1111/febs.14096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/17/2017] [Accepted: 04/27/2017] [Indexed: 12/28/2022]
Abstract
We have investigated the physiology and mechanical profiles of skinned papillary muscle fibers from transgenic mice expressing the N47K mutation in the myosin regulatory light chain (RLC), shown to cause hypertrophic cardiomyopathy in humans. The results were compared with wild-type (WT) mice, both expressing the human ventricular RLC. Rate constants of a cross-bridge (XB) cycle were deduced from tension transients induced by sinusoidal length changes during maximal Ca2+ activation, and were studied as a function of MgATP, MgADP, and Pi concentrations. N47K mutant showed slower XB cycles but higher actin-activated ATPase activity compared with WT. Consequently, N47K exhibited larger tension than WT. K0 (ADP association constant) and K4 (equilibrium constant of force generation) were larger in N47K, and K1 (ATP association constant) was slightly larger in N47K vs. WT, demonstrating stronger nucleotide binding and force generation abilities of the mutant, but no changes in rigor acto-myosin binding were observed. Tension per XB was similar among groups, but N47K exhibited more XB distribution in the attached state. Larger values of tension and higher ATPase in N47K suggested that more cross-bridges participated in tension production in the mutant myocardium compared with WT. In vivo analysis of heart function, performed in ~ 12.5-month-old mice by echocardiography and invasive hemodynamics, demonstrated a significant decrease in dP/dtmax -end-diastolic volume relationship, indicating a depression of ventricular contractility in N47K mice. Our findings suggest that the N47K mutation exerts its action through direct alterations of myosin motor function that ultimately result in pathological hypertrophic remodeling in N47K hearts.
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Affiliation(s)
- Li Wang
- Departments of Anatomy and Cell Biology and Internal Medicine, University of Iowa, IA, USA
| | - Katarzyna Kazmierczak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, FL, USA
| | - Chen-Ching Yuan
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, FL, USA
| | - Sunil Yadav
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, FL, USA
| | - Masataka Kawai
- Departments of Anatomy and Cell Biology and Internal Medicine, University of Iowa, IA, USA
| | - Danuta Szczesna-Cordary
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, FL, USA
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22
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Jackson TR, Kim HY, Balakrishnan UL, Stuckenholz C, Davidson LA. Spatiotemporally Controlled Mechanical Cues Drive Progenitor Mesenchymal-to-Epithelial Transition Enabling Proper Heart Formation and Function. Curr Biol 2017; 27:1326-1335. [PMID: 28434863 DOI: 10.1016/j.cub.2017.03.065] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 02/14/2017] [Accepted: 03/27/2017] [Indexed: 10/19/2022]
Abstract
During early cardiogenesis, bilateral fields of mesenchymal heart progenitor cells (HPCs) move from the anterior lateral plate mesoderm to the ventral midline, undergoing a mesenchymal-to-epithelial transition (MET) en route to forming a single epithelial sheet. Through tracking of tissue-level deformations in the heart-forming region (HFR) as well as movement trajectories and traction generation of individual HPCs, we find that the onset of MET correlates with a peak in mechanical stress within the HFR and changes in HPC migratory behaviors. Small-molecule inhibitors targeting actomyosin contractility reveal a temporally specific requirement of bulk tissue compliance to regulate heart development and MET. Targeting mutant constructs to modulate contractility and compliance in the underlying endoderm, we find that MET in HPCs can be accelerated in response to microenvironmental stiffening and can be inhibited by softening. To test whether MET in HPCs was responsive to purely physical mechanical cues, we mimicked a high-stress state by injecting an inert oil droplet to generate high strain in the HFR, demonstrating that exogenously applied stress was sufficient to drive MET. MET-induced defects in anatomy result in defined functional lesions in the larval heart, implicating mechanical signaling and MET in the etiology of congenital heart defects. From this integrated analysis of HPC polarity and mechanics, we propose that normal heart development requires bilateral HPCs to undergo a critical behavioral and phenotypic transition on their way to the ventral midline, and that this transition is driven in response to the changing mechanical properties of their endoderm substrate.
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Affiliation(s)
- Timothy R Jackson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Hye Young Kim
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Uma L Balakrishnan
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Carsten Stuckenholz
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Developmental Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA; Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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23
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Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis. J Muscle Res Cell Motil 2016; 37:203-214. [PMID: 27942960 DOI: 10.1007/s10974-016-9456-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 09/27/2016] [Indexed: 10/20/2022]
Abstract
In mammalian ventricles, two myosin heavy chain (MHC) isoforms have been identified. Small animals express α-MHC, whereas large animals express β-MHC, which contribute to a large difference in the heart rate. Sprague-Dawley rats possessing ~99% α-MHC were treated with propylthiouracil to result in 100% β-MHC. Papillary muscles were skinned, dissected into small fibers, and used for experiments. To understand the functional difference between α-MHC and β-MHC, skinned-fibers were activated under the intracellular ionic conditions: 5 mM MgATP, 1 mM Mg2+, 8 mM Pi, 200 mM ionic strength, pH 7.00 at 25 °C. Small amplitude sinusoidal length oscillations were applied in the frequency range 0.13-100 Hz (corresponding time domain: 1.6-1200 ms), and effects of Ca2+, Pi, and ATP were studied. The results show that Ca2+ sensitivity was slightly less (10-15%) in β-MHC than α-MHC containing fibers. Sinusoidal analysis at pCa 4.66 (full Ca2+ activation) demonstrated that, the apparent rate constants were 2-4× faster in α-MHC containing fibers. The ATP study demonstrated that, in β-MHC containing fibers, K 1 (ATP association constant) was greater (1.7×), k 2 and k -2 (cross-bridge detachment and its reversal rate constants) were smaller (×0.6). The Pi study demonstrated that, in β-MHC containing fibers, k 4 (rate constant of the force-generation step) and k -4 were smaller (0.75× and 0.25×, respectively), resulting in greater K 4 (3×). There were no differences in active tension, rigor stiffness, or K 2 (equilibrium constant of the cross-bridge detachment step). Our study further demonstrated that there were no differences in parameters between fibers obtained from left and right ventricles, but with an exception in K 5 (Pi association constant).
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24
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Månsson A. Actomyosin based contraction: one mechanokinetic model from single molecules to muscle? J Muscle Res Cell Motil 2016; 37:181-194. [PMID: 27864648 PMCID: PMC5383694 DOI: 10.1007/s10974-016-9458-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 11/09/2016] [Indexed: 12/26/2022]
Abstract
Bridging the gaps between experimental systems on different hierarchical scales is needed to overcome remaining challenges in the understanding of muscle contraction. Here, a mathematical model with well-characterized structural and biochemical actomyosin states is developed to that end. We hypothesize that this model accounts for generation of force and motion from single motor molecules to the large ensembles of muscle. In partial support of this idea, a wide range of contractile phenomena are reproduced without the need to invoke cooperative interactions or ad hoc states/transitions. However, remaining limitations exist, associated with ambiguities in available data for model definition e.g.: (1) the affinity of weakly bound cross-bridges, (2) the characteristics of the cross-bridge elasticity and (3) the exact mechanistic relationship between the force-generating transition and phosphate release in the actomyosin ATPase. Further, the simulated number of attached myosin heads in the in vitro motility assay differs several-fold from duty ratios, (fraction of strongly attached ATPase cycle times) derived in standard analysis. After addressing the mentioned issues the model should be useful in fundamental studies, for engineering of myosin motors as well as for studies of muscle disease and drug development.
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Affiliation(s)
- Alf Månsson
- Department of Chemistry and Biomedical Sciences, Faculty of Health and Life Sciences, Linnaeus University, 39182, Kalmar, Sweden.
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25
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Marston SB. Why Is there a Limit to the Changes in Myofilament Ca 2+-Sensitivity Associated with Myopathy Causing Mutations? Front Physiol 2016; 7:415. [PMID: 27725803 PMCID: PMC5035734 DOI: 10.3389/fphys.2016.00415] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/05/2016] [Indexed: 12/15/2022] Open
Abstract
Mutations in striated muscle contractile proteins have been found to be the cause of a number of inherited muscle diseases; in most cases the mechanism proposed for causing the disease is derangement of the thin filament-based Ca2+-regulatory system of the muscle. When considering the results of experiments reported over the last 15 years, one feature has been frequently noted, but rarely discussed: the magnitude of changes in myofilament Ca2+-sensitivity due to myopathy-causing mutations in skeletal or heart muscle seems to be always in the range 1.5-3x EC50. Such consistency suggests it may be related to a fundamental property of muscle regulation; in this article we will investigate whether this observation is true and consider why this should be so. A literature search found 71 independent measurements of HCM mutation-induced change of EC50 ranging from 1.15 to 3.8-fold with a mean of 1.87 ± 0.07 (sem). We also found 11 independent measurements of increased Ca2+-sensitivity due to mutations in skeletal muscle proteins ranging from 1.19 to 2.7-fold with a mean of 2.00 ± 0.16. Investigation of dilated cardiomyopathy-related mutations found 42 independent determinations with a range of EC50 wt/mutant from 0.3 to 2.3. In addition we found 14 measurements of Ca2+-sensitivity changes due skeletal muscle myopathy mutations ranging from 0.39 to 0.63. Thus, our extensive literature search, although not necessarily complete, found that, indeed, the changes in myofilament Ca2+-sensitivity due to disease-causing mutations have a bimodal distribution and that the overall changes in Ca2+-sensitivity are quite small and do not extend beyond a three-fold increase or decrease in Ca2+-sensitivity. We discuss two mechanism that are not necessarily mutually exclusive. Firstly, it could be that the limit is set by the capabilities of the excitation-contraction machinery that supplies activating Ca2+ and that striated muscle cannot work in a way compatible with life outside these limits; or it may be due to a fundamental property of the troponin system and the permitted conformational transitions compatible with efficient regulation.
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Affiliation(s)
- Steven B Marston
- National Heart & Lung Institute, Imperial College London London, UK
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26
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Bang ML. Animal Models of Congenital Cardiomyopathies Associated With Mutations in Z-Line Proteins. J Cell Physiol 2016; 232:38-52. [PMID: 27171814 DOI: 10.1002/jcp.25424] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 05/10/2016] [Indexed: 01/15/2023]
Abstract
The cardiac Z-line at the boundary between sarcomeres is a multiprotein complex connecting the contractile apparatus with the cytoskeleton and the extracellular matrix. The Z-line is important for efficient force generation and transmission as well as the maintenance of structural stability and integrity. Furthermore, it is a nodal point for intracellular signaling, in particular mechanosensing and mechanotransduction. Mutations in various genes encoding Z-line proteins have been associated with different cardiomyopathies, including dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, restrictive cardiomyopathy, and left ventricular noncompaction, and mutations even within the same gene can cause widely different pathologies. Animal models have contributed to a great advancement in the understanding of the physiological function of Z-line proteins and the pathways leading from mutations in Z-line proteins to cardiomyopathy, although genotype-phenotype prediction remains a great challenge. This review presents an overview of the currently available animal models for Z-line and Z-line associated proteins involved in human cardiomyopathies with special emphasis on knock-in and transgenic mouse models recapitulating the clinical phenotypes of human cardiomyopathy patients carrying mutations in Z-line proteins. Pros and cons of mouse models will be discussed and a future outlook will be given. J. Cell. Physiol. 232: 38-52, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Marie-Louise Bang
- Institute of Genetic and Biomedical Research, UOS Milan, National Research Council and Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
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27
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Messer AE, Bayliss CR, El-Mezgueldi M, Redwood CS, Ward DG, Leung MC, Papadaki M, Dos Remedios C, Marston SB. Mutations in troponin T associated with Hypertrophic Cardiomyopathy increase Ca(2+)-sensitivity and suppress the modulation of Ca(2+)-sensitivity by troponin I phosphorylation. Arch Biochem Biophys 2016; 601:113-20. [PMID: 27036851 PMCID: PMC4909753 DOI: 10.1016/j.abb.2016.03.027] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 03/16/2016] [Accepted: 03/26/2016] [Indexed: 11/24/2022]
Abstract
We investigated the effect of 7 Hypertrophic Cardiomyopathy (HCM)-causing mutations in troponin T (TnT) on troponin function in thin filaments reconstituted with actin and human cardiac tropomyosin. We used the quantitative in vitro motility assay to study Ca2+-regulation of unloaded movement and its modulation by troponin I phosphorylation. Troponin from a patient with the K280N TnT mutation showed no difference in Ca2+-sensitivity when compared with donor heart troponin and the Ca2+-sensitivity was also independent of the troponin I phosphorylation level (uncoupled). The recombinant K280N TnT mutation increased Ca2+-sensitivity 1.7-fold and was also uncoupled. The R92Q TnT mutation in troponin from transgenic mouse increased Ca2+-sensitivity and was also completely uncoupled. Five TnT mutations (Δ14, Δ28 + 7, ΔE160, S179F and K273E) studied in recombinant troponin increased Ca2+-sensitivity and were all fully uncoupled. Thus, for HCM-causing mutations in TnT, Ca2+-sensitisation together with uncoupling in vitro is the usual response and both factors may contribute to the HCM phenotype. We also found that Epigallocatechin-3-gallate (EGCG) can restore coupling to all uncoupled HCM-causing TnT mutations. In fact the combination of Ca2+-desensitisation and re-coupling due to EGCG completely reverses both the abnormalities found in troponin with a TnT HCM mutation suggesting it may have therapeutic potential. 7 HCM-causing mutations in cardiac TnT were studied using in vitro motility assay. All the mutations increased myofilament Ca2+-sensitivity (range 1.5–2.7 fold). All mutations suppressed the modulation of Ca2+-sensitivity by TnI phosphorylation. Epigallocatechin-3-gallate (EGCG) restored this modulation to all mutations. This suggests a therapeutic potential for EGCG in the treatment of HCM.
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28
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Vikhorev PG, Song W, Wilkinson R, Copeland O, Messer AE, Ferenczi MA, Marston SB. The dilated cardiomyopathy-causing mutation ACTC E361G in cardiac muscle myofibrils specifically abolishes modulation of Ca(2+) regulation by phosphorylation of troponin I. Biophys J 2015; 107:2369-80. [PMID: 25418306 PMCID: PMC4241448 DOI: 10.1016/j.bpj.2014.10.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 09/25/2014] [Accepted: 10/16/2014] [Indexed: 01/30/2023] Open
Abstract
Phosphorylation of troponin I by protein kinase A (PKA) reduces Ca2+ sensitivity and increases the rate of Ca2+ release from troponin C and the rate of relaxation in cardiac muscle. In vitro experiments indicate that mutations that cause dilated cardiomyopathy (DCM) uncouple this modulation, but this has not been demonstrated in an intact contractile system. Using a Ca2+-jump protocol, we measured the effect of the DCM-causing mutation ACTC E361G on the equilibrium and kinetic parameters of Ca2+ regulation of contractility in single transgenic mouse heart myofibrils. We used propranolol treatment of mice to reduce the level of troponin I and myosin binding protein C (MyBP-C) phosphorylation in their hearts before isolating the myofibrils. In nontransgenic mouse myofibrils, the Ca2+ sensitivity of force was increased, the fast relaxation phase rate constant, kREL, was reduced, and the length of the slow linear phase, tLIN, was increased when the troponin I phosphorylation level was reduced from 1.02 to 0.3 molPi/TnI (EC50 P/unP = 1.8 ± 0.2, p < 0.001). Native myofibrils from ACTC E361G transgenic mice had a 2.4-fold higher Ca2+ sensitivity than nontransgenic mouse myofibrils. Strikingly, the Ca2+ sensitivity and relaxation parameters of ACTC E361G myofibrils did not depend on the troponin I phosphorylation level (EC50 P/unP = 0.88 ± 0.17, p = 0.39). Nevertheless, modulation of the Ca2+ sensitivity of ACTC E361G myofibrils by sarcomere length or EMD57033 was indistinguishable from that of nontransgenic myofibrils. Overall, EC50 measured in different conditions varied over a 7-fold range. The time course of relaxation, as defined by tLIN and kREL, was correlated with EC50 but varied by just 2.7- and 3.3-fold, respectively. Our results confirm that troponin I phosphorylation specifically alters the Ca2+ sensitivity of isometric tension and the time course of relaxation in cardiac muscle myofibrils. Moreover, the DCM-causing mutation ACTC E361G blunts this phosphorylation-dependent response without affecting other parameters of contraction, including length-dependent activation and the response to EMD57033.
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Affiliation(s)
- Petr G Vikhorev
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Weihua Song
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Ross Wilkinson
- National Heart and Lung Institute, Imperial College London, London, UK
| | - O'Neal Copeland
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Andrew E Messer
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Michael A Ferenczi
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Steven B Marston
- National Heart and Lung Institute, Imperial College London, London, UK.
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29
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Papadaki M, Vikhorev PG, Marston SB, Messer AE. Uncoupling of myofilament Ca2+ sensitivity from troponin I phosphorylation by mutations can be reversed by epigallocatechin-3-gallate. Cardiovasc Res 2015; 108:99-110. [PMID: 26109583 DOI: 10.1093/cvr/cvv181] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 06/11/2015] [Indexed: 02/02/2023] Open
Abstract
AIMS Heart muscle contraction is regulated via the β-adrenergic response that leads to phosphorylation of Troponin I (TnI) at Ser22/23, which changes the Ca(2+) sensitivity of the cardiac myofilament. Mutations in thin filament proteins that cause dilated cardiomyopathy (DCM) and some mutations that cause hypertrophic cardiomyopathy (HCM) abolish the relationship between TnI phosphorylation and Ca(2+) sensitivity (uncoupling). Small molecule Ca(2+) sensitizers and Ca(2+) desensitizers that act upon troponin alter the Ca(2+) sensitivity of the thin filament, but their relationship with TnI phosphorylation has never been studied before. METHODS AND RESULTS Quantitative in vitro motility assay showed that 30 µM EMD57033 and 100 µM Bepridil increase Ca(2+) sensitivity of phosphorylated cardiac thin filaments by 3.1- and 2.8-fold, respectively. Additionally they uncoupled Ca(2+) sensitivity from TnI phosphorylation, mimicking the effect of HCM mutations. Epigallocatechin-3-gallate (EGCG) decreased Ca(2+) sensitivity of phosphorylated and unphosphorylated wild-type thin filaments equally (by 2.15 ± 0.45- and 2.80 ± 0.48-fold, respectively), retaining the coupling. Moreover, EGCG also reduced Ca(2+) sensitivity of phosphorylated but not unphosphorylated thin filaments containing DCM and HCM-causing mutations; thus, the dependence of Ca(2+) sensitivity upon TnI phosphorylation of uncoupled mutant thin filaments was restored in every case. In single mouse heart myofibrils, EGCG reduced Ca(2+) sensitivity of force and kACT and also preserved coupling. Myofibrils from the ACTC E361G (DCM) mouse were uncoupled; EGCG reduced Ca(2+) sensitivity more for phosphorylated than for unphosphorylated myofibrils, thus restoring coupling. CONCLUSION We conclude that it is possible to both mimic and reverse the pathological defects in troponin caused by cardiomyopathy mutations pharmacologically. Re-coupling by EGCG may be of potential therapeutic significance for treating cardiomyopathies.
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Affiliation(s)
- Maria Papadaki
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Petr G Vikhorev
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Steven B Marston
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
| | - Andrew E Messer
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK
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30
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Dahari M, Dawson JF. Do cardiac actin mutations lead to altered actomyosin interactions? Biochem Cell Biol 2015; 93:330-4. [PMID: 26194323 DOI: 10.1139/bcb-2014-0156] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is currently hypothesized that increased heart muscle contractility leads to hypertrophic cardiomyopathy (HCM), and reduced contractility leads to dilated cardiomyopathy (DCM). To determine if changes in the core interaction between actin and myosin occur due to mutations in the cardiac actin gene (ACTC), we measured the interactions between myosin and 8 ACTC mutant proteins found in patients with HCM or DCM. R312H showed a decreased actin-activated myosin S1 ATPase rate (13.1 ± 0.63 μmol/L/min) compared to WT (15.3 ± 1.6 μmol/L/min), whereas the rate with E99K was significantly higher (20.1 ± 1.5 μmol/L/min). In vitro motility assays with varying ATP concentrations showed that the KM for E99K remains unchanged with a significantly decreased Vmax (1.90 ± 0.37 μm/sec) compared to WT (3.33 ± 0.46 μm/sec). Based on a 5 nm myosin step size, we calculated a duty ratio of approximately 0.04 for WT and the majority of mutant actins; however, the duty ratio for E99K was twice as high. Based on our analysis of 8 ACTC mutants, we infer that mutations in ACTC lead to disease through various molecular mechanisms. While changes in actomyosin interactions with the E99K mutation might cause increased ATP usage and tension leading to HCM, measurable changes in the basic interaction between actin and myosin do not appear to be involved in the mechanisms of disease development for the other ACTC mutants tested.
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Affiliation(s)
- Marissa Dahari
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.,Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - John F Dawson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.,Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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Bai F, Caster HM, Dawson JF, Kawai M. The immediate effect of HCM causing actin mutants E99K and A230V on actin-Tm-myosin interaction in thin-filament reconstituted myocardium. J Mol Cell Cardiol 2014; 79:123-32. [PMID: 25451174 DOI: 10.1016/j.yjmcc.2014.10.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 10/23/2014] [Accepted: 10/26/2014] [Indexed: 10/24/2022]
Abstract
Human cardiac actin mutants E99K and A230V were expressed with baculovirus/insect cells and used to reconstitute the thin-filament of bovine cardiac (BVC) muscle fibers, together with tropomyosin (Tm) and troponin (Tn) purified from bovine ventricles. Effects of [Ca(2+)], [ATP], and [phosphate] on tension and its transients were studied at 25°C. In the absence of Tm/Tn, both mutants significantly decreased the tension of actin filament reconstituted fibers (WT: 0.75±0.06 T0, E99K: 0.58±0.04 T0, A230V: 0.58±0.03 T0), where T0 is active tension of native fibers (T0=26.9±1.1kPa, N=41), indicating diminished actin-myosin interactions. However, in the presence of Tm and Tn, WT, E99K, and A230V recovered tension (0.85±0.06 T0, 0.89±0.06 T0, and 0.85±0.05 T0, respectively), demonstrating the compensatory effect of Tm/Tn. Ca(2+) sensitivity (pCa50) increased (5.59±0.02, 5.80±0.03, 5.77±0.03, respectively) and cooperativity (nH) decreased (2.6±0.3, 1.87±0.21, 1.60±0.11, respectively). The kinetic constants of the cross-bridge cycle were deduced using sinusoidal analysis. E99K did not show any significant changes in any of the kinetic constants compared to those of WT. A230V caused a decrease in K1 (ATP association constant), k2 and k-2 (rate constants of the cross-bridge detachment step). The cross-bridge distribution was similar among WT, E99K, and A230V. In conclusion, our experiments demonstrate that the first step of HCM pathogenesis with E99K is increased pCa50 and decreased nH, which result in larger tension during partial activation to cause a diastolic problem. The effect on nH is more severe with A230V. In addition, A230V has a problem of decreased cross-bridge kinetics, which affects the normal functions of the cross-bridge cycle and may contribute to the first step of the HCM pathogenesis.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, and Internal Medicine, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - Hannah M Caster
- Department of Anatomy and Cell Biology, and Internal Medicine, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - John F Dawson
- Department of Molecular and Cellular Biology, University of Guelph, College of Biological Science, Guelph, Ontario N1G 2W1, Canada.
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, and Internal Medicine, The University of Iowa, Iowa City, IA 52242-1109, USA.
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32
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Wang L, Ji X, Barefield D, Sadayappan S, Kawai M. Phosphorylation of cMyBP-C affects contractile mechanisms in a site-specific manner. Biophys J 2014; 106:1112-22. [PMID: 24606935 DOI: 10.1016/j.bpj.2014.01.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 01/18/2014] [Accepted: 01/23/2014] [Indexed: 01/05/2023] Open
Abstract
Cardiac myosin binding protein-C (cMyBP-C) is a cardiac-specific, thick-filament regulatory protein that is differentially phosphorylated at Ser(273), Ser(282), and Ser(302) by various kinases and modulates contraction. In this study, phosphorylation-site-specific effects of cMyBP-C on myocardial contractility and cross-bridge kinetics were studied by sinusoidal analysis in papillary and trabecular muscle fibers isolated from t/t (cMyBP-C-null) mice and in their counterparts in which cMyBP-C contains the ADA (Ala(273)-Asp(282)-Ala(302)), DAD (Asp(273)-Ala(282)-Asp(302)), and SAS (Ser(273)-Ala(282)-Ser(302)) mutations; the results were compared to those from mice expressing the wild-type (WT) transgene on the t/t background. Under standard activating conditions, DAD fibers showed significant decreases in tension (~50%), stiffness, the fast apparent rate constant 2πc, and its magnitude C, as well as its magnitude H, but an increase in the medium rate constant 2πb, with respect to WT. The t/t fibers showed a smaller drop in stiffness and a significant decrease in 2πc that can be explained by isoform shift of myosin heavy chain. In the pCa-tension study using the 8 mM phosphate (Pi) solution, there was hardly any difference in Ca(2+) sensitivity (pCa50) and cooperativity (nH) between the mutant and WT samples. However, in the solutions without Pi, DAD showed increased nH and slightly decreased pCa50. We infer from these observations that the nonphosphorylatable residue 282 combined with phosphomimetic residues Asp(273) and/or Asp(302) (in DAD) is detrimental to cardiomyocytes by lowering isometric tension and altering cross-bridge kinetics with decreased 2πc and increased 2πb. In contrast, a single change of residue 282 to nonphosphorylatable Ala (SAS), or to phosphomimetic Asps together with the changes of residues 273 and 302 to nonphosphorylatable Ala (ADA) causes minute changes in fiber mechanics.
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Affiliation(s)
- Li Wang
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa; School of Nursing, Soochow University, Suzhou, Jiangsu, China
| | - Xiang Ji
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois
| | - David Barefield
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois
| | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois
| | - Masakata Kawai
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
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33
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Messer AE, Marston SB. Investigating the role of uncoupling of troponin I phosphorylation from changes in myofibrillar Ca(2+)-sensitivity in the pathogenesis of cardiomyopathy. Front Physiol 2014; 5:315. [PMID: 25202278 PMCID: PMC4142463 DOI: 10.3389/fphys.2014.00315] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 08/02/2014] [Indexed: 12/12/2022] Open
Abstract
Contraction in the mammalian heart is controlled by the intracellular Ca(2+) concentration as it is in all striated muscle, but the heart has an additional signaling system that comes into play to increase heart rate and cardiac output during exercise or stress. β-adrenergic stimulation of heart muscle cells leads to release of cyclic-AMP and the activation of protein kinase A which phosphorylates key proteins in the sarcolemma, sarcoplasmic reticulum and contractile apparatus. Troponin I (TnI) and Myosin Binding Protein C (MyBP-C) are the prime targets in the myofilaments. TnI phosphorylation lowers myofibrillar Ca(2+)-sensitivity and increases the speed of Ca(2+)-dissociation and relaxation (lusitropic effect). Recent studies have shown that this relationship between Ca(2+)-sensitivity and TnI phosphorylation may be unstable. In familial cardiomyopathies, both dilated and hypertrophic (DCM and HCM), a mutation in one of the proteins of the thin filament often results in the loss of the relationship (uncoupling) and blunting of the lusitropic response. For familial dilated cardiomyopathy in thin filament proteins it has been proposed that this uncoupling is causative of the phenotype. Uncoupling has also been found in human heart tissue from patients with hypertrophic obstructive cardiomyopathy as a secondary effect. Recently, it has been found that Ca(2+)-sensitizing drugs can promote uncoupling, whilst one Ca(2+)-desensitizing drug Epigallocatechin 3-Gallate (EGCG) can reverse uncoupling. We will discuss recent findings about the role of uncoupling in the development of cardiomyopathies and the molecular mechanism of the process.
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Affiliation(s)
- Andrew E. Messer
- National Heart & Lung Institute, Imperial College LondonLondon, UK
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Bai F, Caster HM, Rubenstein PA, Dawson JF, Kawai M. Using baculovirus/insect cell expressed recombinant actin to study the molecular pathogenesis of HCM caused by actin mutation A331P. J Mol Cell Cardiol 2014; 74:64-75. [PMID: 24793351 DOI: 10.1016/j.yjmcc.2014.04.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 04/21/2014] [Accepted: 04/22/2014] [Indexed: 01/07/2023]
Abstract
Recombinant WT human cardiac actin (WT actin) was expressed using the baculovirus/insect cell expression system, purified, and used to reconstitute the thin-filament of bovine cardiac muscle fibers, together with bovine cardiac tropomyosin (Tm) and troponin (Tn). Effects of [Ca(2+)], [ATP], [phosphate] and [ADP] on tension and tension transients were studied at 25°C by using sinusoidal analysis, and the results were compared with those of native fibers and fibers reconstituted with purified bovine cardiac actin (BVC actin). In actin filament reconstituted fibers (without Tm/Tn), those reconstituted with WT actin showed exactly the same active tension as those reconstituted with purified BVC actin (WT: 0.75±0.06 T0, N=11; BVC: 0.73±0.07 T0, N=12, where T0 is the tension of original fibers before extraction). After Tm/Tn reconstitution, fibers reconstituted with WT actin generated 0.85±0.06 T0 (N=11) compared to 0.98±0.04 T0 (N=12) recovered by those reconstituted with BVC actin. In the presence of Tm/Tn, WT actin reconstituted fibers showed exactly the same Ca(2+) sensitivity as those of the native fibers and BVC actin reconstituted fibers (pCa50: native fibers: 5.69±0.01, N=10; WT: 5.69±0.02, N=11; BVC: 5.68±0.02, N=12). Sinusoidal analysis showed that the cross-bridge kinetics were the same among native fibers, BVC actin reconstituted fibers and WT actin reconstituted fibers, followed by reconstitution of Tm/Tn. These results demonstrate that baculovirus/insect cell expressed actin has no significant differences from tissue purified actin and can be used for thin-filament reconstitution assays. One hypertrophic cardiomyopathy (HCM) causing actin mutant A331P actin was also expressed and studied similarly, and the results were compared to those of the WT actin. In the reconstituted fibers, A331P significantly decreased the tension both in the absence of Tm/Tn (0.55±0.03 T0, N=13) and in their presence (0.65±0.02 T0, N=13) compared to those of the WT (0.75±0.06 T0 and 0.85±0.06 T0, respectively, N=11). A331P also showed decreased pCa50 (5.57±0.03, N=13) compared to that of WT (5.69±0.02, N=11). The cross-bridge kinetics and its distribution were similar between WT and A331P actin reconstituted fibers, indicating that force/cross-bridge was decreased by A331P. In conclusion, A331P causes a weakened cross-bridge force, which leads to a decreased active tension, reduces left-ventricular ejection fraction, and eventually results in the HCM phenotype.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - Hannah M Caster
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - Peter A Rubenstein
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242-1109, USA.
| | - John F Dawson
- Department of Molecular & Cellular Biology, University of Guelph, College of Biological Science, Guelph, Ontario N1G 2 W1, Canada.
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242-1109, USA; Department of Internal Medicine, The University of Iowa, Iowa City, IA 52242-1109, USA.
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Fiedler LR, Maifoshie E, Schneider MD. Mouse models of heart failure: cell signaling and cell survival. Curr Top Dev Biol 2014; 109:171-247. [PMID: 24947238 DOI: 10.1016/b978-0-12-397920-9.00002-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Heart failure is one of the paramount global causes of morbidity and mortality. Despite this pandemic need, the available clinical counter-measures have not altered substantially in recent decades, most notably in the context of pharmacological interventions. Cell death plays a causal role in heart failure, and its inhibition poses a promising approach that has not been thoroughly explored. In previous approaches to target discovery, clinical failures have reflected a deficiency in mechanistic understanding, and in some instances, failure to systematically translate laboratory findings toward the clinic. Here, we review diverse mouse models of heart failure, with an emphasis on those that identify potential targets for pharmacological inhibition of cell death, and on how their translation into effective therapies might be improved in the future.
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Affiliation(s)
- Lorna R Fiedler
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London, UK.
| | - Evie Maifoshie
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London, UK
| | - Michael D Schneider
- British Heart Foundation Centre of Research Excellence, National Heart and Lung Institute, Imperial College London, London, UK.
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Li A, Estigoy C, Raftery M, Cameron D, Odeberg J, Pontén F, Lal S, Dos Remedios CG. Heart research advances using database search engines, Human Protein Atlas and the Sydney Heart Bank. Heart Lung Circ 2013; 22:819-26. [PMID: 23856366 DOI: 10.1016/j.hlc.2013.06.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 06/07/2013] [Accepted: 06/11/2013] [Indexed: 10/26/2022]
Abstract
This Methodological Review is intended as a guide for research students who may have just discovered a human "novel" cardiac protein, but it may also help hard-pressed reviewers of journal submissions on a "novel" protein reported in an animal model of human heart failure. Whether you are an expert or not, you may know little or nothing about this particular protein of interest. In this review we provide a strategic guide on how to proceed. We ask: How do you discover what has been published (even in an abstract or research report) about this protein? Everyone knows how to undertake literature searches using PubMed and Medline but these are usually encyclopaedic, often producing long lists of papers, most of which are either irrelevant or only vaguely relevant to your query. Relatively few will be aware of more advanced search engines such as Google Scholar and even fewer will know about Quertle. Next, we provide a strategy for discovering if your "novel" protein is expressed in the normal, healthy human heart, and if it is, we show you how to investigate its subcellular location. This can usually be achieved by visiting the website "Human Protein Atlas" without doing a single experiment. Finally, we provide a pathway to discovering if your protein of interest changes its expression level with heart failure/disease or with ageing.
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Affiliation(s)
- Amy Li
- Discipline of Anatomy & Histology, Bosch Institute, University of Sydney, Sydney 2006, Australia.
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Li Y, Zhang L, Jean-Charles PY, Nan C, Chen G, Tian J, Jin JP, Gelb IJ, Huang X. Dose-dependent diastolic dysfunction and early death in a mouse model with cardiac troponin mutations. J Mol Cell Cardiol 2013; 62:227-36. [PMID: 23810866 DOI: 10.1016/j.yjmcc.2013.06.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 05/24/2013] [Accepted: 06/13/2013] [Indexed: 11/28/2022]
Abstract
Our aim was to explore the dose-dependent diastolic dysfunction and the mechanisms of heart failure and early death in transgenic (TG) mice modeling human restrictive cardiomyopathy (RCM). The first RCM mouse model (cTnI(193His) mice) carrying cardiac troponin I (cTnI) R193H mutation (mouse cTnI R193H equals to human cTnI R192H) was generated several years ago in our laboratory. The RCM mice manifested a phenotype similar to that observed in RCM patients carrying the same cTnI mutation, i.e. enlarged atria and restricted ventricles. However, the causes of heart failure and early death observed in RCM mice remain unclear. In this study, we have produced RCM TG mice (cTnI(193His)-L, cTnI(193His)-M and cTnI(193His)-H) that express various levels of mutant cTnI in the heart. Histological examination and echocardiography were performed on these mice to monitor the time course of the disease development and heart failure. Our data demonstrate that cTnI mutation-caused diastolic dysfunction is dose-dependent. The key mechanism is myofibril hypersensitivity to Ca(2+) resulting in an impaired relaxation in the mutant cardiac myocytes. Prolonged relaxation time and delay of Ca(2+) decay observed in the mutant cardiac myocytes are correlated with the level of the mutant protein in the heart. Markedly enlarged atria due to the elevated end-diastolic pressure and myocardial ischemia are observed in the heart of the transgenic mice. In the mice with the highest level of the mutant protein, restricted ventricles and systolic dysfunction occur followed immediately by heart failure and early death. Diastolic dysfunction caused by R193H troponin I mutation is specific, showing a dose-dependent pattern. These mouse models are useful tools for the study of diastolic dysfunction. Impaired diastole can cause myocardial ischemia and fibrosis formation, resulting in the development of systolic dysfunction and heart failure with early death in the RCM mice with a high level of the mutant protein in the heart.
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Affiliation(s)
- Yuejin Li
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA
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Tropomyosin isoform expression and phosphorylation in the human heart in health and disease. J Muscle Res Cell Motil 2013; 34:189-97. [PMID: 23712688 DOI: 10.1007/s10974-013-9347-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/09/2013] [Indexed: 01/08/2023]
Abstract
We determined the isoforms of tropomyosin expressed and the level of tropomyosin phosphorylation in donor, end-stage failing and hypertrophic obstructive cardiomyopathy samples of human heart muscle. Western blots and isoform-specific antibodies showed that α-tropomyosin was the only significant isoform expressed and that tropomyosin was 25-30% phosphorylated at serine 283. Mass spectrometry confirmed directly that α-tropomyosin made up over 95% of tropomyosin but also indicated the presence of up to 4% κ-tropomyosin and much smaller amounts of β-, γ- and smooth β-tropomyosin and about 26% phosphorylation. Neither the isoform distribution nor the level of phosphorylation changed significantly in the pathological heart muscle samples.
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Song W, Vikhorev PG, Kashyap MN, Rowlands C, Ferenczi MA, Woledge RC, MacLeod K, Marston S, Curtin NA. Mechanical and energetic properties of papillary muscle from ACTC E99K transgenic mouse models of hypertrophic cardiomyopathy. Am J Physiol Heart Circ Physiol 2013; 304:H1513-24. [PMID: 23604709 DOI: 10.1152/ajpheart.00951.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We compared the contractile performance of papillary muscle from a mouse model of hypertrophic cardiomyopathy [α-cardiac actin (ACTC) E99K mutation] with nontransgenic (non-TG) littermates. In isometric twitches, ACTC E99K papillary muscle produced three to four times greater force than non-TG muscle under the same conditions independent of stimulation frequency and temperature, whereas maximum isometric force in myofibrils from these muscles was not significantly different. ACTC E99K muscle relaxed slower than non-TG muscle in both papillary muscle (1.4×) and myofibrils (1.7×), whereas the rate of force development after stimulation was the same as non-TG muscle for both electrical stimulation in intact muscle and after a Ca²⁺ jump in myofibrils. The EC₅₀ for Ca²⁺ activation of force in myofibrils was 0.39 ± 0.33 μmol/l in ACTC E99K myofibrils and 0.80 ± 0.11 μmol/l in non-TG myofibrils. There were no significant differences in the amplitude and time course of the Ca²⁺ transient in myocytes from ACTC E99K and non-TG mice. We conclude that hypercontractility is caused by higher myofibrillar Ca²⁺ sensitivity in ACTC E99K muscles. Measurement of the energy (work + heat) released in actively cycling heart muscle showed that for both genotypes, the amount of energy turnover increased with work done but with decreasing efficiency as energy turnover increased. Thus, ACTC E99K mouse heart muscle produced on average 3.3-fold more work than non-TG muscle, and the cost in terms of energy turnover was disproportionately higher than in non-TG muscles. Efficiency for ACTC E99K muscle was in the range of 11-16% and for non-TG muscle was 15-18%.
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Affiliation(s)
- Weihua Song
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
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Memo M, Leung MC, Ward DG, dos Remedios C, Morimoto S, Zhang L, Ravenscroft G, McNamara E, Nowak KJ, Marston SB, Messer AE. Familial dilated cardiomyopathy mutations uncouple troponin I phosphorylation from changes in myofibrillar Ca²⁺ sensitivity. Cardiovasc Res 2013; 99:65-73. [PMID: 23539503 DOI: 10.1093/cvr/cvt071] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS The pure form of familial dilated cardiomyopathy (DCM) is mainly caused by mutations in genes encoding sarcomeric proteins. Previous measurements using recombinant proteins suggested that DCM mutations in thin filament proteins decreased myofibrillar Ca(2+) sensitivity, but exceptions were reported. We re-investigated the molecular mechanism of familial DCM using native proteins. METHODS AND RESULTS We used the quantitative in vitro motility assay and native troponin and tropomyosin to study DCM mutations in troponin I, troponin T, and α-tropomyosin. Four mutations reduced myofilament Ca(2+) sensitivity, but one mutation (TPM1 E54K) did not alter Ca(2+) sensitivity and another (TPM1 D230N) increased Ca(2+) sensitivity. In thin filaments from normal human and mouse heart, protein kinase A (PKA) phosphorylation of troponin I caused a two- to three-fold decrease in myofibrillar Ca(2+) sensitivity. However, Ca(2+) sensitivity did not change with the level of troponin I phosphorylation in any of the DCM-mutant containing thin filaments (E40K, E54K, and D230N in α-tropomyosin; R141W and ΔK210 in cardiac troponin T; K36Q in cardiac troponin I; G159D in cardiac troponin C, and E361G in cardiac α-actin). This 'uncoupling' was observed with native mutant protein from human and mouse heart and with recombinant mutant protein expressed in baculovirus/Sf9 systems. Uncoupling was independent of the fraction of mutated protein present above 0.55. CONCLUSION We conclude that DCM-causing mutations in thin filament proteins abolish the relationship between myofilament Ca(2+) sensitivity and troponin I phosphorylation by PKA. We propose that this blunts the response to β-adrenergic stimulation and could be the cause of DCM in the long term.
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Affiliation(s)
- Massimiliano Memo
- Myocardial Function, NHLI, Imperial College London, London, W12 0NN, UK
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Bayliss CR, Jacques AM, Leung MC, Ward DG, Redwood CS, Gallon CE, Copeland O, McKenna WJ, Dos Remedios C, Marston SB, Messer AE. Myofibrillar Ca(2+) sensitivity is uncoupled from troponin I phosphorylation in hypertrophic obstructive cardiomyopathy due to abnormal troponin T. Cardiovasc Res 2012; 97:500-8. [PMID: 23097574 DOI: 10.1093/cvr/cvs322] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS We studied the relationship between myofilament Ca(2+) sensitivity and troponin I (TnI) phosphorylation by protein kinase A at serines 22/23 in human heart troponin isolated from donor hearts and from myectomy samples from patients with hypertrophic obstructive cardiomyopathy (HOCM). METHODS AND RESULTS We used a quantitative in vitro motility assay. With donor heart troponin, Ca(2+) sensitivity is two- to three-fold higher when TnI is unphosphorylated. In the myectomy samples from patients with HOCM, the mean level of TnI phosphorylation was low: 0.38 ± 0.19 mol Pi/mol TnI compared with 1.60 ± 0.19 mol Pi/mol TnI in donor hearts, but no difference in myofilament Ca(2+) sensitivity was observed. Thus, troponin regulation of thin filament Ca(2+) sensitivity is abnormal in HOCM hearts. HOCM troponin (0.29 mol Pi/mol TnI) was treated with protein kinase A to increase the level of phosphorylation to 1.56 mol Pi/mol TnI. No difference in EC(50) was found in thin filaments containing high and low TnI phosphorylation levels. This indicates that Ca(2+) sensitivity is uncoupled from TnI phosphorylation in HOCM heart troponin. Coupling could be restored by replacing endogenous troponin T (TnT) with the recombinant TnT T3 isoform. No difference in Ca(2+) sensitivity was observed if TnI was exchanged into HOCM heart troponin or if TnT was exchanged into the highly phosphorylated donor heart troponin. Comparison of donor and HOCM heart troponin by mass spectrometry and with adduct-specific antibodies did not show any differences in TnT isoform expression, phosphorylation or any post-translational modifications. CONCLUSION An abnormality in TnT is responsible for uncoupling myofibrillar Ca(2+) sensitivity from TnI phosphorylation in the septum of HOCM patients.
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Affiliation(s)
- Christopher R Bayliss
- Myocardial Function, NHLI, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
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Müller M, Mazur AJ, Behrmann E, Diensthuber RP, Radke MB, Qu Z, Littwitz C, Raunser S, Schoenenberger CA, Manstein DJ, Mannherz HG. Functional characterization of the human α-cardiac actin mutations Y166C and M305L involved in hypertrophic cardiomyopathy. Cell Mol Life Sci 2012; 69:3457-79. [PMID: 22643837 PMCID: PMC11115188 DOI: 10.1007/s00018-012-1030-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/22/2012] [Accepted: 05/07/2012] [Indexed: 11/25/2022]
Abstract
Inherited cardiomyopathies are caused by point mutations in sarcomeric gene products, including α-cardiac muscle actin (ACTC1). We examined the biochemical and cell biological properties of the α-cardiac actin mutations Y166C and M305L identified in hypertrophic cardiomyopathy (HCM). Untagged wild-type (WT) cardiac actin, and the Y166C and M305L mutants were expressed by the baculovirus/Sf9-cell system and affinity purified by immobilized gelsolin G4-6. Their correct folding was verified by a number of assays. The mutant actins also displayed a disturbed intrinsic ATPase activity and an altered polymerization behavior in the presence of tropomyosin, gelsolin, and Arp2/3 complex. Both mutants stimulated the cardiac β-myosin ATPase to only 50 % of WT cardiac F-actin. Copolymers of WT and increasing amounts of the mutant actins led to a reduced stimulation of the myosin ATPase. Transfection of established cell lines revealed incorporation of EGFP- and hemagglutinin (HA)-tagged WT and both mutant actins into cytoplasmic stress fibers. Adenoviral vectors of HA-tagged WT and Y166C actin were successfully used to infect adult and neonatal rat cardiomyocytes (NRCs). The expressed HA-tagged actins were incorporated into the minus-ends of NRC thin filaments, demonstrating the ability to form hybrid thin filaments with endogenous actin. In NRCs, the Y166C mutant led after 72 h to a shortening of the sarcomere length when compared to NRCs infected with WT actin. Thus our data demonstrate that a mutant actin can be integrated into cardiomyocyte thin filaments and by its reduced mode of myosin interaction might be the basis for the initiation of HCM.
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Affiliation(s)
- Mirco Müller
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Antonina Joanna Mazur
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Present Address: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, 51-148 Wroclaw, Poland
| | - Elmar Behrmann
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Ralph P. Diensthuber
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Michael B. Radke
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Zheng Qu
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Christoph Littwitz
- Department of Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, USA
| | - Stefan Raunser
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Cora-Ann Schoenenberger
- Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, 4046 Basel, Switzerland
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
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Constantinesco A, Choquet P, Goetz C, Monassier L. PET, SPECT, CT, and MRI in Mouse Cardiac Phenotyping: An Overview. ACTA ACUST UNITED AC 2012; 2:129-44. [DOI: 10.1002/9780470942390.mo110225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- André Constantinesco
- Laboratoire d'Imagerie Préclinique, Service de Biophysique et Médecine Nucléaire, Hôpitaux Universitaires de Strasbourg; Strasbourg France
| | - Philippe Choquet
- Laboratoire d'Imagerie Préclinique, Service de Biophysique et Médecine Nucléaire, Hôpitaux Universitaires de Strasbourg; Strasbourg France
| | - Christian Goetz
- Laboratoire d'Imagerie Préclinique, Service de Biophysique et Médecine Nucléaire, Hôpitaux Universitaires de Strasbourg; Strasbourg France
| | - Laurent Monassier
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, Université de Strasbourg; Strasbourg France
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Subdomain location of mutations in cardiac actin correlate with type of functional change. PLoS One 2012; 7:e36821. [PMID: 22590617 PMCID: PMC3348139 DOI: 10.1371/journal.pone.0036821] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 04/15/2012] [Indexed: 11/19/2022] Open
Abstract
Determining the molecular mechanisms that lead to the development of heart failure will help us gain better insight into the most costly health problem in the Western world. To understand the roles that the actin protein plays in the development of heart failure, we have taken a systematic approach toward characterizing human cardiac actin mutants that have been associated with either hypertrophic or dilated cardiomyopathy. Seven known cardiac actin mutants were expressed in a baculovirus system, and their intrinsic properties were studied. In general, the changes to the properties of the actin proteins themselves were subtle. The R312H variant exhibited reduced stability, with a Tm of 53.6°C compared to 56.8°C for WT actin, accompanied with increased polymerization critical concentration and Pi release rate, and a marked increase in nucleotide release rates. Substitution of methionine for leucine at amino acid 305 showed no impact on the stability, nucleotide release rates, or DNase-I inhibition ability of the actin monomer; however, during polymerization, a 2-fold increase in Pi release was observed. Increases to both the Tm and DNase-I inhibition activity suggested interactions between E99K actin molecules under monomer-promoting conditions. Y166C actin had a higher critical concentration resulting in a lower Pi release rate due to reduced filament-forming potential. The locations of mutations on the ACTC protein correlated with the molecular effects; in general, mutations in subdomain 3 affected the stability of the ACTC protein or affect the polymerization of actin filaments, while mutations in subdomains 1 and 4 more likely affect protein-protein interactions.
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Dwyer J, Iskratsch T, Ehler E. Actin in striated muscle: recent insights into assembly and maintenance. Biophys Rev 2011; 4:17-25. [PMID: 28510000 DOI: 10.1007/s12551-011-0062-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/17/2011] [Indexed: 01/28/2023] Open
Abstract
Striated muscle cells are characterised by a para-crystalline arrangement of their contractile proteins actin and myosin in sarcomeres, the basic unit of the myofibrils. A multitude of proteins is required to build and maintain the structure of this regular arrangement as well as to ensure regulation of contraction and to respond to alterations in demand. This review focuses on the actin filaments (also called thin filaments) of the sarcomere and will discuss how they are assembled during myofibrillogenesis and in hypertrophy and how their integrity is maintained in the working myocardium.
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Affiliation(s)
- Joseph Dwyer
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Thomas Iskratsch
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.,Biological Sciences, Columbia University, 713 Fairchild Center, New York, NY, 10027, USA
| | - Elisabeth Ehler
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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Marston S, Copeland O, Gehmlich K, Schlossarek S, Carrier L, Carrrier L. How do MYBPC3 mutations cause hypertrophic cardiomyopathy? J Muscle Res Cell Motil 2011; 33:75-80. [PMID: 22057632 DOI: 10.1007/s10974-011-9268-3] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 10/08/2011] [Indexed: 11/28/2022]
Abstract
It is well established that MYBPC3 mutations are the most common cause of hypertrophic cardiomyopathy, accounting for about half of identified mutations. However, when compared with mutations in other myofibrillar proteins that cause hypertrophic cardiomyopathy, MYBPC3 mutations seem to be the odd one out. The most striking characteristic of HCM mutations in MYBPC3 is that many are within introns and are predicted to cause aberrant splicing leading to a frameshift and a premature chain termination, yet the truncated peptides have never been identified in human heart tissue carrying these mutations. Instead of expression of a poison peptide we consistently observe haploinsufficiency of MyBP-C in MYBPC3 mutant human heart muscle. In this review we investigate the mechanism for MyBP-C haploinsufficiency and consider how this haploinsufficiency could cause hypertrophic cardiomyopathy.
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