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Calcium Handling in Inherited Cardiac Diseases: A Focus on Catecholaminergic Polymorphic Ventricular Tachycardia and Hypertrophic Cardiomyopathy. Int J Mol Sci 2023; 24:ijms24043365. [PMID: 36834774 PMCID: PMC9963263 DOI: 10.3390/ijms24043365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/02/2023] [Accepted: 02/04/2023] [Indexed: 02/10/2023] Open
Abstract
Calcium (Ca2+) is the major mediator of cardiac contractile function. It plays a key role in regulating excitation-contraction coupling and modulating the systolic and diastolic phases. Defective handling of intracellular Ca2+ can cause different types of cardiac dysfunction. Thus, the remodeling of Ca2+ handling has been proposed to be a part of the pathological mechanism leading to electrical and structural heart diseases. Indeed, to ensure appropriate electrical cardiac conduction and contraction, Ca2+ levels are regulated by several Ca2+-related proteins. This review focuses on the genetic etiology of cardiac diseases related to calcium mishandling. We will approach the subject by focalizing on two clinical entities: catecholaminergic polymorphic ventricular tachycardia (CPVT) as a cardiac channelopathy and hypertrophic cardiomyopathy (HCM) as a primary cardiomyopathy. Further, this review will illustrate the fact that despite the genetic and allelic heterogeneity of cardiac defects, calcium-handling perturbations are the common pathophysiological mechanism. The newly identified calcium-related genes and the genetic overlap between the associated heart diseases are also discussed in this review.
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Al-Shafai KN, Al-Hashemi M, Manickam C, Musa R, Selvaraj S, Syed N, Vempalli F, Ali M, Yacoub M, Estivill X. Genetic evaluation of cardiomyopathies in Qatar identifies enrichment of pathogenic sarcomere gene variants and possible founder disease mutations in the Arabs. Mol Genet Genomic Med 2021; 9:e1709. [PMID: 34137518 PMCID: PMC8372065 DOI: 10.1002/mgg3.1709] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 09/03/2020] [Accepted: 05/04/2021] [Indexed: 01/20/2023] Open
Abstract
Background Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are serious inherited heart diseases with various causative mutations identified. The full spectrum of causative mutations remains to be discovered, especially in understudied populations. Methods Here, we established the DOHA Registry and Biobank for cardiomyopathies in Qatar, followed by sequencing of 174 genes on 51 HCM and 53 DCM patients, and 31 relatives. Results In HCM, the analysis of 25 HCM‐associated genes showed that 20% of HCM cases had putative pathogenic variants for cardiomyopathy, mainly in sarcomere genes. Additional 49% of HCM cases had variants of uncertain significance, while 31% of HCM cases had likely benign variant(s) or had no variants identified within the analyzed HCM genes. In DCM, 56 putative DCM genes were analyzed. Eight percent of DCM cases had putative pathogenic variants for DCM, in the TTN gene while 70% of cases had variants of uncertain significance, in the analyzed DCM genes, that will need further pathogenicity assessment. Moreover, 22% of DCM cases remain unexplained, by having likely benign variant(s) or having no variants detected in any of the analyzed DCM genes. Conclusion We identified or replicated at least four recurrent variants among cardiomyopathy patients, which could be founder disease mutations in the Arabic population, including a frameshift variant (c.1371_1381dupTATCCAGTTAT) of unknown significance in the FKTN gene which seems to cause DCM in homozygosity, and HCM in heterozygosity. In vivo and/or in vitro functional validation need to be pursued in order to assess the pathogenicity of the identified variants.
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Affiliation(s)
- Kholoud N Al-Shafai
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar.,Sidra Research Department, Sidra Medicine, Doha, Qatar
| | | | | | - Rania Musa
- The Heart Hospital, Hamad Medical Corporation, Doha, Qatar
| | | | - Najeeb Syed
- Sidra Research Department, Sidra Medicine, Doha, Qatar
| | | | - Muneera Ali
- The Heart Hospital, Hamad Medical Corporation, Doha, Qatar
| | - Magdi Yacoub
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Xavier Estivill
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar.,Sidra Research Department, Sidra Medicine, Doha, Qatar.,Quantitative Genomics Laboratories (qGenomics, Barcelona, Spain
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Abstract
Paediatric cardiomyopathy is a progressive and often lethal disorder and the most common cause of heart failure in children. Despite their severe outcomes, their genetic etiology is still poorly characterised. The current study aimed at uncovering the genetic background of idiopathic primary hypertrophic cardiomyopathy in a cohort of Egyptian children using targeted next-generation sequencing. The study included 24 patients (15 males and 9 females) presented to the cardiomyopathy clinic of Cairo University Children's Hospital with a median age of 2.75 (0.5-14) years. Consanguinity was positive in 62.5% of patients. A family history of hypertrophic cardiomyopathy was present in 20.8% of patients. Ten rare variants were detected in eight patients; two pathogenic variants (8.3%) in MBPC3 and MYH7, and eight variants of uncertain significance in MYBPC3, TTN, VCL, MYL2, CSRP3, and RBM20.Here, we report on the first national study in Egypt that analysed sarcomeric and non-sarcomeric variants in a cohort of idiopathic paediatric hypertrophic cardiomyopathy patients using next-generation sequencing. The current pilot study suggests that paediatric hypertrophic cardiomyopathy in Egypt might have a particular genetic background, especially with the high burden of consanguinity. Including the genetic testing in the routine diagnostic service is important for a better understanding of the pathophysiology of the disease, proper patient management, and at-risk detection. Genome-wide tests (whole exome/genome sequencing) might be better than the targeted sequencing approach to test primary hypertrophic cardiomyopathy patients in addition to its ability for the identification of novel genetic causes.
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Gonzalez-Martinez D, Johnston JR, Landim-Vieira M, Ma W, Antipova O, Awan O, Irving TC, Bryant Chase P, Pinto JR. Structural and functional impact of troponin C-mediated Ca 2+ sensitization on myofilament lattice spacing and cross-bridge mechanics in mouse cardiac muscle. J Mol Cell Cardiol 2018; 123:26-37. [PMID: 30138628 DOI: 10.1016/j.yjmcc.2018.08.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/26/2018] [Accepted: 08/05/2018] [Indexed: 12/25/2022]
Abstract
Acto-myosin cross-bridge kinetics are important for beat-to-beat regulation of cardiac contractility; however, physiological and pathophysiological mechanisms for regulation of contractile kinetics are incompletely understood. Here we explored whether thin filament-mediated Ca2+ sensitization influences cross-bridge kinetics in permeabilized, osmotically compressed cardiac muscle preparations. We used a murine model of hypertrophic cardiomyopathy (HCM) harboring a cardiac troponin C (cTnC) Ca2+-sensitizing mutation, Ala8Val in the regulatory N-domain. We also treated wild-type murine muscle with bepridil, a cTnC-targeting Ca2+ sensitizer. Our findings suggest that both methods of increasing myofilament Ca2+ sensitivity increase cross-bridge cycling rate measured by the rate of tension redevelopment (kTR); force per cross-bridge was also enhanced as measured by sinusoidal stiffness and I1,1/I1,0 ratio from X-ray diffraction. Computational modeling suggests that Ca2+ sensitization through this cTnC mutation or bepridil accelerates kTR primarily by promoting faster cross-bridge detachment. To elucidate if myofilament structural rearrangements are associated with changes in kTR, we used small angle X-ray diffraction to simultaneously measure myofilament lattice spacing and isometric force during steady-state Ca2+ activations. Within in vivo lattice dimensions, lattice spacing and steady-state isometric force increased significantly at submaximal activation. We conclude that the cTnC N-domain controls force by modulating both the number and rate of cycling cross-bridges, and that the both methods of Ca2+ sensitization may act through stabilization of cTnC's D-helix. Furthermore, we propose that the transient expansion of the myofilament lattice during Ca2+ activation may be an additional factor that could increase the rate of cross-bridge cycling in cardiac muscle. These findings may have implications for the pathophysiology of HCM.
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Affiliation(s)
- David Gonzalez-Martinez
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Jamie R Johnston
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Weikang Ma
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Olga Antipova
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA; X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, USA
| | - Omar Awan
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Thomas C Irving
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - J Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.
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Kawai M, Johnston JR, Karam T, Wang L, Singh RK, Pinto JR. Myosin Rod Hypophosphorylation and CB Kinetics in Papillary Muscles from a TnC-A8V KI Mouse Model. Biophys J 2017; 112:1726-1736. [PMID: 28445763 DOI: 10.1016/j.bpj.2017.02.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 02/17/2017] [Accepted: 02/22/2017] [Indexed: 12/11/2022] Open
Abstract
The cardiac troponin C (TnC)-A8V mutation is associated with hypertrophic and restrictive cardiomyopathy (HCM and RCM) in human and mice. The residue affected lies in the N-helix, a region known to affect Ca2+-binding affinity to the N-terminal domain. Here we report on the functional effects of this mutation in skinned papillary muscle fibers from homozygous knock-in TnC-A8V mice. Muscle fibers from left ventricle were activated at 25°C under the ionic conditions of working cardiomyocytes. The pCa-tension relationship showed a 3× increase in Ca2+-sensitivity and a decrease (0.8×) in cooperativity (nH) in mutant fibers. The elementary steps of the cross-bridge (CB) cycle were investigated by sinusoidal analysis. The ATP study revealed that there is no significant change in the affinity of ATP (K1) for the myosin head. In TnC-A8V mutant fibers, the CB detachment rate (k2) and its equilibrium constant (K2) increased (1.5×). The phosphate study revealed that rate constant of the force-generation step (k4) decreased (0.5×), reversal step (k-4) increased (2×), and the phosphate-release step (1/K5) increased (2×). Pro-Q Diamond staining of the skinned fibers samples revealed no significant changes in total phosphorylation of multiple sarcomeric proteins. Further investigation using liquid chromatography-tandem mass spectrometry revealed hypophosphorylation of the rod domain of myosin heavy chain in TnC-A8V mutant fibers compared to wild-type. Immunoblotting confirmed the results observed in the mass spectrometry analysis. The results suggest perturbed CB kinetics-possibly caused by changes in the α-myosin heavy chain phosphorylation profile-as a novel mechanism, to our knowledge, by which a mutation in TnC can have rippling effects in the myofilament and contribute to the pathogenesis of HCM/RCM.
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Affiliation(s)
- Masataka Kawai
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, Iowa.
| | - Jamie R Johnston
- Department of Biomedical Sciences, College of Medicine, The Florida State University, Tallahassee, Florida
| | - Tarek Karam
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, Iowa
| | - Li Wang
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, Iowa; School of Nursing, Soochow University, Suzhou, Jiangsu, China
| | - Rakesh K Singh
- Translational Science Laboratory, College of Medicine, The Florida State University, Tallahassee, Florida
| | - Jose R Pinto
- Department of Biomedical Sciences, College of Medicine, The Florida State University, Tallahassee, Florida
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Veltri T, Landim-Vieira M, Parvatiyar MS, Gonzalez-Martinez D, Dieseldorff Jones KM, Michell CA, Dweck D, Landstrom AP, Chase PB, Pinto JR. Hypertrophic Cardiomyopathy Cardiac Troponin C Mutations Differentially Affect Slow Skeletal and Cardiac Muscle Regulation. Front Physiol 2017; 8:221. [PMID: 28473771 PMCID: PMC5397416 DOI: 10.3389/fphys.2017.00221] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/27/2017] [Indexed: 12/22/2022] Open
Abstract
Mutations in TNNC1-the gene encoding cardiac troponin C (cTnC)-that have been associated with hypertrophic cardiomyopathy (HCM) and cardiac dysfunction may also affect Ca2+-regulation and function of slow skeletal muscle since the same gene is expressed in both cardiac and slow skeletal muscle. Therefore, we reconstituted rabbit soleus fibers and bovine masseter myofibrils with mutant cTnCs (A8V, C84Y, E134D, and D145E) associated with HCM to investigate their effects on contractile force and ATPase rates, respectively. Previously, we showed that these HCM cTnC mutants, except for E134D, increased the Ca2+ sensitivity of force development in cardiac preparations. In the current study, an increase in Ca2+ sensitivity of isometric force was only observed for the C84Y mutant when reconstituted in soleus fibers. Incorporation of cTnC C84Y in bovine masseter myofibrils reduced the ATPase activity at saturating [Ca2+], whereas, incorporation of cTnC D145E increased the ATPase activity at inhibiting and saturating [Ca2+]. We also tested whether reconstitution of cardiac fibers with troponin complexes containing the cTnC mutants and slow skeletal troponin I (ssTnI) could emulate the slow skeletal functional phenotype. Reconstitution of cardiac fibers with troponin complexes containing ssTnI attenuated the Ca2+ sensitization of isometric force when cTnC A8V and D145E were present; however, it was enhanced for C84Y. In summary, although the A8V and D145E mutants are present in both muscle types, their functional phenotype is more prominent in cardiac muscle than in slow skeletal muscle, which has implications for the protein-protein interactions within the troponin complex. The C84Y mutant warrants further investigation since it drastically alters the properties of both muscle types and may account for the earlier clinical onset in the proband.
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Affiliation(s)
- Tiago Veltri
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Michelle S. Parvatiyar
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of MedicineMiami, FL, USA
| | - David Gonzalez-Martinez
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | | | - Clara A. Michell
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - David Dweck
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
| | - Andrew P. Landstrom
- Section of Pediatric Cardiology, Department of Pediatrics, Baylor College of MedicineHouston, TX, USA
| | - P. Bryant Chase
- Department of Biological Science, Florida State UniversityTallahassee, FL, USA
| | - Jose R. Pinto
- Department of Biomedical Sciences, Florida State University College of MedicineTallahassee, FL, USA
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Dossat AM, Sanchez-Gonzalez MA, Koutnik AP, Leitner S, Ruiz EL, Griffin B, Rosenberg JT, Grant SC, Fincham FD, Pinto JR, Kabbaj M. Pathogenesis of depression- and anxiety-like behavior in an animal model of hypertrophic cardiomyopathy. FASEB J 2017; 31:2492-2506. [PMID: 28235781 DOI: 10.1096/fj.201600955rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 02/07/2017] [Indexed: 01/04/2023]
Abstract
Cardiovascular dysfunction is highly comorbid with mood disorders, such as anxiety and depression. However, the mechanisms linking cardiovascular dysfunction with the core behavioral features of mood disorder remain poorly understood. In this study, we used mice bearing a knock-in sarcomeric mutation, which is exhibited in human hypertrophic cardiomyopathy (HCM), to investigate the influence of HCM over the development of anxiety and depression. We employed behavioral, MRI, and biochemical techniques in young (3-4 mo) and aged adult (7-8 mo) female mice to examine the effects of HCM on the development of anxiety- and depression-like behaviors. We focused on females because in both humans and rodents, they experience a 2-fold increase in mood disorder prevalence vs. males. Our results showed that young and aged HCM mice displayed echocardiographic characteristics of the heart disease condition, yet only aged HCM females displayed anxiety- and depression-like behaviors. Electrocardiographic parameters of sympathetic nervous system activation were increased in aged HCM females vs. controls and correlated with mood disorder-related symptoms. In addition, when compared with controls, aged HCM females exhibited adrenal gland hypertrophy, reduced volume in mood-related brain regions, and reduced hippocampal signaling proteins, such as brain-derived neurotrophic factor and its downstream targets vs. controls. In conclusion, prolonged systemic HCM stress can lead to development of mood disorders, possibly through inducing structural and functional brain changes, and thus, mood disorders in patients with heart disease should not be considered solely a psychologic or situational condition.-Dossat, A. M., Sanchez-Gonzalez, M. A., Koutnik, A. P., Leitner, S., Ruiz, E. L., Griffin, B., Rosenberg, J. T., Grant, S. C., Fincham, F. D., Pinto, J. R. Kabbaj, M. Pathogenesis of depression- and anxiety-like behavior in an animal model of hypertrophic cardiomyopathy.
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Affiliation(s)
- Amanda M Dossat
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
| | - Marcos A Sanchez-Gonzalez
- Division of Clinical and Translational Research, Larkin Community Hospital, South Miami, Florida, USA
| | - Andrew P Koutnik
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
| | - Stefano Leitner
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
| | - Edda L Ruiz
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
| | - Brittany Griffin
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA
| | - Jens T Rosenberg
- The National High Magnetic Field Laboratory, Center for Interdisciplinary Magnetic Resonance, Florida State University, Tallahassee, Florida, USA; and
| | - Samuel C Grant
- The National High Magnetic Field Laboratory, Center for Interdisciplinary Magnetic Resonance, Florida State University, Tallahassee, Florida, USA; and
| | - Francis D Fincham
- Family Institute, Florida State University, Tallahassee, Florida, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA;
| | - Mohamed Kabbaj
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, USA;
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Jaafar N, Gómez J, Kammoun I, Zairi I, Amara WB, Kachboura S, Kraiem S, Hammami M, Iglesias S, Alonso B, Coto E. Spectrum of Mutations in Hypertrophic Cardiomyopathy Genes Among Tunisian Patients. Genet Test Mol Biomarkers 2016; 20:674-679. [PMID: 27574918 DOI: 10.1089/gtmb.2016.0187] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is a common cardiac genetic disorder associated with heart failure and sudden death. Mutations in the cardiac sarcomere genes are found in approximately half of HCM patients and are more common among cases with a family history of the disease. Data about the mutational spectrum of the sarcomeric genes in HCM patients from Northern Africa are limited. The population of Tunisia is particularly interesting due to its Berber genetic background. As founder mutations have been reported in other disorders. METHODS We performed semiconductor chip (Ion Torrent PGM) next generation sequencing of the nine main sarcomeric genes (MYH7, MYBPC3, TNNT2, TNNI3, ACTC1, TNNC1, MYL2, MYL3, TPM1) as well as the recently identified as an HCM gene, FLNC, in 45 Tunisian HCM patients. RESULTS We found sarcomere gene polymorphisms in 12 patients (27%), with MYBPC3 and MYH7 representing 83% (10/12) of the mutations. One patient was homozygous for a new MYL3 mutation and two were double MYBPC3 + MYH7 mutation carriers. Screening of the FLNC gene identified three new mutations, which points to FLNC mutations as an important cause of HCM among Tunisians. CONCLUSION The mutational background of HCM in Tunisia is heterogeneous. Unlike other Mendelian disorders, there were no highly prevalent mutations that could explain most of the cases. Our study also suggested that FLNC mutations may play a role on the risk for HCM among Tunisians.
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Affiliation(s)
- Nawel Jaafar
- 1 Biochemistry Laboratory LR12ES05 "Nutrition-Functional Food & Vascular Health," USCR Mass Spectrometry, Faculty of Medicine, University of Monastir , Monastir, Tunisia
| | - Juan Gómez
- 2 Unidad de Referencia de Cardiopatías Familiares-HUCA, Genética Molecular y Cardiología, Hospital Universitario Central Asturias , Oviedo, Spain
| | - Ikram Kammoun
- 3 Department of Cardiology, Abderrahmen Mami Hospital , Tunis, Tunisia
| | - Ihsen Zairi
- 4 Department of Cardiology, Habib Thameur Hospital , Tunis, Tunisia
| | - Wael Ben Amara
- 3 Department of Cardiology, Abderrahmen Mami Hospital , Tunis, Tunisia
| | - Salem Kachboura
- 3 Department of Cardiology, Abderrahmen Mami Hospital , Tunis, Tunisia
| | - Sondes Kraiem
- 4 Department of Cardiology, Habib Thameur Hospital , Tunis, Tunisia
| | - Mohamed Hammami
- 1 Biochemistry Laboratory LR12ES05 "Nutrition-Functional Food & Vascular Health," USCR Mass Spectrometry, Faculty of Medicine, University of Monastir , Monastir, Tunisia
| | - Sara Iglesias
- 2 Unidad de Referencia de Cardiopatías Familiares-HUCA, Genética Molecular y Cardiología, Hospital Universitario Central Asturias , Oviedo, Spain
| | - Belén Alonso
- 2 Unidad de Referencia de Cardiopatías Familiares-HUCA, Genética Molecular y Cardiología, Hospital Universitario Central Asturias , Oviedo, Spain
| | - Eliecer Coto
- 2 Unidad de Referencia de Cardiopatías Familiares-HUCA, Genética Molecular y Cardiología, Hospital Universitario Central Asturias , Oviedo, Spain .,5 Departamento de Medicina, Universidad de Oviedo , Oviedo, Spain
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Zot HG, Hasbun JE, Michell CA, Landim-Vieira M, Pinto JR. Enhanced troponin I binding explains the functional changes produced by the hypertrophic cardiomyopathy mutation A8V of cardiac troponin C. Arch Biochem Biophys 2016; 601:97-104. [PMID: 26976709 DOI: 10.1016/j.abb.2016.03.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 02/09/2016] [Accepted: 03/08/2016] [Indexed: 01/17/2023]
Abstract
Higher affinity for TnI explains how troponin C (TnC) carrying a causative hypertrophic cardiomyopathy mutation, TnC(A8V), sensitizes muscle cells to Ca(2+). Muscle fibers reconstituted with TnC(A8V) require ∼2.3-fold less [Ca(2+)] to achieve 50% maximum-tension compared to fibers reconstituted with wild-type TnC (TnC(WT)). Binding measurements rule out a significant change in N-terminus Ca(2+)-affinity of isolated TnC(A8V), and TnC(A8V) binds the switch-peptide of troponin-I (TnI(sp)) ∼1.6-fold more strongly than TnC(WT); thus we model the TnC-TnI(sp) interaction as competing with the TnI-actin interaction. Tension data are well-fit by a model constrained to conditions in which the affinity of TnC(A8V) for TnI(sp) is 1.5-1.7-fold higher than that of TnC(WT) at all [Ca(2+)]. Mean ATPase rates of reconstituted cardiac myofibrils is greater for TnC(A8V) than TnC(WT) at all [Ca(2+)], with statistically significant differences in the means at higher [Ca(2+)]. To probe TnC-TnI interaction in low Ca(2+), displacement of bis-ANS from TnI was monitored as a function of TnC. Whereas Ca(2+)-TnC(WT) displaces significantly more bis-ANS than Mg(2+)-TnC(WT), Ca(2+)-TnC(A8V) displaces probe equivalently to Mg(2+)-TnC(A8V) and Ca(2+)-TnC(WT), consistent with stronger Ca(2+)-independent TnC(A8V)-TnI(sp). A Matlab program for computing theoretical activation is reported. Our work suggests that contractility is constantly above normal in hearts made hypertrophic by TnC(A8V).
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Affiliation(s)
- Henry G Zot
- Department of Biology, University of West Georgia, Carrollton, GA 30118, USA.
| | - Javier E Hasbun
- Department of Physics, University of West Georgia, Carrollton, GA 30118, USA
| | - Clara A Michell
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.
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