1
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Saul T, Bui QM, Argiro A, Keyt L, Olivotto I, Adler E. Natural history and clinical outcomes of patients with hypertrophic cardiomyopathy from thin filament mutations. ESC Heart Fail 2024. [PMID: 38773858 DOI: 10.1002/ehf2.14848] [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: 11/10/2023] [Revised: 03/12/2024] [Accepted: 04/24/2024] [Indexed: 05/24/2024] Open
Abstract
Hypertrophic cardiomyopathy (HCM) due to thick filament variants is more common; however, HCM due to thin filament variants (HCM-Thin) may be associated with a more malignant phenotype with an increased risk of sudden cardiac death. The aim of this study was to review all the published cases of HCM-Thin to better understand the natural history and clinical outcomes of this disease. A literature review of HCM-Thin identified 21 studies with a total of 177 patients that were suitable for analysis. There were three outcomes of interest, which included a heart failure composite, a ventricular arrhythmia composite and a heart failure and arrhythmia composite outcome. Kaplan-Meier (KM) survival analyses for freedom from each of the abovementioned composite outcomes were completed for the entire cohort and stratified by age of onset and sarcomeric variant. The heart failure composite occurred in 24 (13.6%) patients, the ventricular arrhythmia composite occurred in 30 patients (16.9%) and the combined heart failure and arrhythmia composite occurred in 50 patients (28.2%). In regard to left ventricular ejection fraction (LVEF), the majority of patients were preserved (LVEF > 50%) compared with mildly reduced (LVEF 41%-50%) and reduced (LVEF ≤ 40%) (respectively 26.6% vs. 0.6% vs. 3.4%). The median maximal left ventricular wall thickness (LVWT) was 19.0 mm [interquartile range (IQR) 5.3]. Only 10.7% of the cohort had evidence of left ventricular outflow tract (LVOT) obstruction. Those with paediatric-onset HCM had earlier onset and were at higher risk for each endpoint than their adult counterparts. When stratified by genetic variant, patients with TNNI3 and TPM1 were at a higher risk of the heart failure composite endpoint and the combined heart failure and arrhythmia composite endpoint in comparison with those with the other genetic variants. HCM-Thin is associated with significant morbidity and mortality, with a high arrhythmia burden despite low rates of cardiac obstruction and mild hypertrophy. The paediatric onset of disease and certain sarcomeric variants appear to be associated with a worse prognosis than their adult-onset and other sarcomeric variant counterparts. HCM-Thin seems to have a distinct phenotype, which may require a different management approach.
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Affiliation(s)
- Tatiana Saul
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, San Diego, California, USA
| | - Quan M Bui
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, San Diego, California, USA
| | - Alessia Argiro
- Cardiomyopathy Unit, Careggi University Hospital, Florence, Italy
| | - Lucas Keyt
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, San Diego, California, USA
| | - Iacopo Olivotto
- Cardiomyopathy Unit, Careggi University Hospital, Florence, Italy
| | - Eric Adler
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, San Diego, California, USA
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2
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Thottakara T, Padmanabhan A, Tanriverdi T, Thambidurai T, Diaz-RG JA, Amonkar SR, Olgin JE, Long CS, Roselle Abraham M. Single-nucleus RNA/ATAC-seq in early-stage HCM models predicts SWI/SNF-activation in mutant-myocytes, and allele-specific differences in fibroblasts. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.24.589078. [PMID: 38903075 PMCID: PMC11188105 DOI: 10.1101/2024.04.24.589078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Hypertrophic cardiomyopathy (HCM) is associated with phenotypic variability. To gain insights into transcriptional regulation of cardiac phenotype, single-nucleus linked RNA-/ATAC-seq was performed in 5-week-old control mouse-hearts (WT) and two HCM-models (R92W-TnT, R403Q-MyHC) that exhibit differences in heart size/function and fibrosis; mutant data was compared to WT. Analysis of 23,304 nuclei from mutant hearts, and 17,669 nuclei from WT, revealed similar dysregulation of gene expression, activation of AP-1 TFs (FOS, JUN) and the SWI/SNF complex in both mutant ventricular-myocytes. In contrast, marked differences were observed between mutants, for gene expression/TF enrichment, in fibroblasts, macrophages, endothelial cells. Cellchat predicted activation of pro-hypertrophic IGF-signaling in both mutant ventricular-myocytes, and profibrotic TGFβ-signaling only in mutant-TnT fibroblasts. In summary, our bioinformatics analyses suggest that activation of IGF-signaling, AP-1 TFs and the SWI/SNF chromatin remodeler complex promotes myocyte hypertrophy in early-stage HCM. Selective activation of TGFβ-signaling in mutant-TnT fibroblasts contributes to genotype-specific differences in cardiac fibrosis.
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Affiliation(s)
- Tilo Thottakara
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
- Department of Cardiology, University Heart and Vascular Center Hamburg, Germany
| | - Arun Padmanabhan
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
- Gladstone Institutes, San Francisco, CA, USA
| | - Talha Tanriverdi
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - Tharika Thambidurai
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - Jose A. Diaz-RG
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - Sanika R. Amonkar
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - Jeffrey E. Olgin
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - Carlin S. Long
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
| | - M. Roselle Abraham
- Department of Medicine, University of California San Francisco, Division of Cardiology, San Francisco
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3
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Koshy L, Ganapathi S, Jeemon P, Madhuma M, Vysakh Y, Lakshmikanth L, Harikrishnan S. Sarcomeric gene variants among Indians with hypertrophic cardiomyopathy: A scoping review. Indian J Med Res 2023; 158:119-135. [PMID: 37787257 PMCID: PMC10645028 DOI: 10.4103/ijmr.ijmr_3567_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Indexed: 10/04/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease that frequently causes sudden cardiac death (SCD) among young adults. Several pathogenic mutations in genes encoding the cardiac sarcomere have been identified as diagnostic factors for HCM and proposed as prognostic markers for SCD. The objective of this review was to determine the scope of available literature on the variants encoding sarcomere proteins associated with SCD reported among Indian patients with HCM. The eligibility criteria for the scoping review included full text articles that reported the results of genetic screening for sarcomeric gene mutations in HCM patients of Indian south Asian ancestry. We systematically reviewed studies from the databases of Medline, Scopus, Web of Science core collection and Google Scholar. The electronic search strategy included a combination of generic terms related to genetics, disease and population. The protocol of the study was registered with Open Science Framework (https://osf.io/53gde/). A total of 19 articles were identified that reported pathogenic or likely pathogenic (P/LP) variants within MYH7, MYBPC3, TNNT2, TNNI3 and TPM1 genes, that included 16 singletons, one de novo and one digenic mutation (MYH7/ TPM1) associated with SCD among Indian patients. Evidence from functional studies and familial segregation implied a plausible mechanistic role of these P/LP variants in HCM pathology. This scoping review has compiled all the P/LP variants reported to-date among Indian patients and summarized their association with SCD. Single homozygous, de novo and digenic mutations were observed to be associated with severe phenotypes compared to single heterozygous mutations. The abstracted genetic information was updated with reference sequence ID (rsIDs) and compiled into freely accessible HCMvar database, available at https://hcmvar.heartfailure.org.in/. This can be used as a population specific genetic database for reference by clinicians and researchers involved in the identification of diagnostic and prognostic markers for HCM.
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Affiliation(s)
- Linda Koshy
- Centre for Advance Research & Excellence in Heart Failure, Thiruvananthapuram, Kerala, India
| | - Sanjay Ganapathi
- Department of Cardiology, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram, Kerala, India
| | - Panniyammakal Jeemon
- Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram, Kerala, India
| | - M. Madhuma
- Centre for Advance Research & Excellence in Heart Failure, Thiruvananthapuram, Kerala, India
| | - Y. Vysakh
- Centre for Advance Research & Excellence in Heart Failure, Thiruvananthapuram, Kerala, India
| | - L.R. Lakshmikanth
- Centre for Advance Research & Excellence in Heart Failure, Thiruvananthapuram, Kerala, India
| | - Sivadasanpillai Harikrishnan
- Department of Cardiology, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram, Kerala, India
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Lynn ML, Jimenez J, Castillo RL, Klass MM, Vasquez C, Baldo A, Gibson C, Murphy AM, Tardiff JC. The HCM - Linked Mutation Arg92Leu in TNNT2 Allosterically Alters the cTnC - cTnI Interface and Disrupts the PKA-mediated Regulation of Myofilament Relaxation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.18.549569. [PMID: 37503299 PMCID: PMC10370115 DOI: 10.1101/2023.07.18.549569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Background Impaired left ventricular relaxation, high filling pressures, and dysregulation of Ca 2+ homeostasis are common findings contributing to diastolic dysfunction in hypertrophic cardiomyopathy (HCM). Studies have shown that impaired relaxation is an early observation in the sarcomere-gene-positive preclinical HCM cohort which suggests potential involvement of myofilament regulators of relaxation. Yet, a molecular level understanding of mechanism(s) at the level of the myofilament is lacking. We hypothesized that mutation-specific, allosterically mediated, changes to the cardiac troponin C-cardiac troponin I (cTnC-cTnI) interface can account for the development of early-onset diastolic dysfunction via decreased PKA accessibility to cTnI. Methods HCM mutations R92L-cTnT (Arg92Leu) and Δ160E-cTnT (Glu160 deletion) were studied in vivo , in vitro, and in silico via 2D echocardiography, western blotting, ex vivo hemodynamics, stopped-flow kinetics, time resolved fluorescence resonance energy transfer (TR-FRET), and molecular dynamics simulations. Results The HCM-causative mutations R92L-cTnT and Δ160E-cTnT result in different time-of-onset of diastolic dysfunction. R92L-cTnT demonstrated early-onset diastolic dysfunction accompanied by a localized decrease in phosphorylation of cTnI. Constitutive phosphorylation of cTnI (cTnI-D 23 D 24 ) was sufficient to recover diastolic function to Non-Tg levels only for R92L-cTnT. Mutation-specific changes in Ca 2+ dissociation rates associated with R92L-cTnT reconstituted with cTnI-D 23 D 24 led us to investigate potential involvement of structural changes in the cTnC-cTnI interface as an explanation for these observations. We probed the interface via TR-FRET revealing a repositioning of the N-terminus of cTnI, closer to cTnC, and concomitant decreases in distance distributions at sites flanking the PKA consensus sequence. Implementing TR-FRET distances as constraints into our atomistic model identified additional electrostatic interactions at the consensus sequence. Conclusion These data indicate that the early diastolic dysfunction observed in a subset of HCM is likely attributable to structural changes at the cTnC-cTnI interface that impair accessibility of PKA thereby blunting β-adrenergic responsiveness and identifying a potential molecular target for therapeutic intervention.
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5
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Pasqua T, Tropea T, Granieri MC, De Bartolo A, Spena A, Moccia F, Rocca C, Angelone T. Novel molecular insights and potential approaches for targeting hypertrophic cardiomyopathy: Focus on coronary modulators. Vascul Pharmacol 2022; 145:107003. [DOI: 10.1016/j.vph.2022.107003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 05/04/2022] [Accepted: 05/30/2022] [Indexed: 11/26/2022]
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6
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Huang Y, Lu H, Ren X, Li F, Bu W, Liu W, Dailey WP, Saeki H, Gabrielson K, Abraham R, Eckenhoff R, Gao WD. Fropofol prevents disease progression in mice with hypertrophic cardiomyopathy. Cardiovasc Res 2021; 116:1175-1185. [PMID: 31424496 DOI: 10.1093/cvr/cvz218] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 06/12/2019] [Accepted: 08/15/2019] [Indexed: 01/12/2023] Open
Abstract
AIMS Increased myofilament contractility is recognized as a crucial factor in the pathogenesis of hypertrophic cardiomyopathy (HCM). Direct myofilament desensitization might be beneficial in preventing HCM disease progression. Here, we tested whether the small molecule fropofol prevents HCM phenotype expression and disease progression by directly depressing myofilament force development. METHODS AND RESULTS Force, intracellular Ca2+, and steady-state activation were determined in isolated trabecular muscles from wild-type (WT) and transgenic HCM mice with heterozygous human α-myosin heavy chain R403Q mutation (αMHC 403/+). αMHC 403/+ HCM mice were treated continuously with fropofol by intraperitoneal infusion for 12 weeks. Heart tissue was analysed with histology and real-time PCR of prohypertrophic and profibrotic genes. Fropofol decreased force in a concentration-dependent manner without significantly altering [Ca2+]i in isolated muscles from both WT and αMHC 403/+ HCM mouse hearts. Fropofol also depressed maximal Ca2+-activated force and increased the [Ca2+]i required for 50% activation during steady-state activation. In whole-animal studies, chronic intra-abdominal administration of fropofol prevented hypertrophy development and diastolic dysfunction. Chronic fropofol treatment also led to attenuation of prohypertrophic and profibrotic gene expression, reductions in cell size, and decreases in tissue fibrosis. CONCLUSIONS Direct inhibition of myofilament contraction by fropofol prevents HCM disease phenotypic expression and progression, suggesting that increased myofilament contractile force is the primary trigger for hypertrophy development and HCM disease progression.
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Affiliation(s)
- Yiyuan Huang
- Department of Cardiology, 2nd Xiangya Hospital Central South University, 139 Renmin Middle Road, Changsha, Hunan 410011, China
| | - Haisong Lu
- Department of Anesthesiology, Peking Union Hospital, Peking Union Medical College and Chinese Academy of Medical Science, 1 Shuaifuyuan, Wangfujin, Dongcheng District, Beijing 100730, China
| | - Xianfeng Ren
- Department of Anesthesiology, China-Japan Friendship Hospital, 2 Yinghuanyuan East Street, Chaoying District, Beijing 100029, China
| | - Fazhao Li
- Department of General Surgery, 2nd Xiangya Hospital, 139 Renmin Middle Road, Central South University, Changsha, Hunan 410011, China
| | - Weiming Bu
- Department of Anesthesiology, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, PA 19104, USA
| | - Wenjie Liu
- Department of Anesthesiology, South China University School of Medicine, 69 Chuanshan Road, Shigu District, Hengyang, Hunan 421001, China
| | - William P Dailey
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, 231 S. 34 Street, Philadelphia, PA 19104, USA
| | - Harumi Saeki
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 N. Broadway, MRB 807, Baltimore, MD 21205, USA
| | - Kathleen Gabrielson
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 N. Broadway, MRB 807, Baltimore, MD 21205, USA
| | - Roselle Abraham
- Division of Cardiology, Department of Medicine, University of California San Francisco, 555 Mission Bay Blvd South, Smith Cardiovascular Research Building, 452K, San Francisco, CA 94158, USA
| | - Roderic Eckenhoff
- Department of Anesthesiology, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, PA 19104, USA
| | - Wei Dong Gao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, 1800 Orleans Street, Zayed Tower 6208, Baltimore, MD 21287, USA
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7
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Wijnker PJM, van der Velden J. Mutation-specific pathology and treatment of hypertrophic cardiomyopathy in patients, mouse models and human engineered heart tissue. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165774. [PMID: 32217077 DOI: 10.1016/j.bbadis.2020.165774] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 03/16/2020] [Accepted: 03/17/2020] [Indexed: 01/04/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy and is characterized by asymmetric left ventricular hypertrophy and diastolic dysfunction, and a frequent cause of sudden cardiac death at young age. Pharmacological treatment to prevent or reverse HCM is lacking. This may be partly explained by the variety of underlying disease causes. Over 1500 mutations have been associated with HCM, of which the majority reside in genes encoding sarcomere proteins, the cardiac contractile building blocks. Several mutation-mediated disease mechanisms have been identified, with proof for gene- and mutation-specific cellular perturbations. In line with mutation-specific changes in cellular pathology, the response to treatment may depend on the underlying sarcomere gene mutation. In this review, we will discuss evidence for mutation-specific pathology and treatment responses in HCM patients, mouse models and engineered heart tissue. The pros and cons of these experimental models for studying mutation-specific HCM pathology and therapies will be outlined.
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Affiliation(s)
- Paul J M Wijnker
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, De Boelelaan 1117, Amsterdam, the Netherlands.
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, De Boelelaan 1117, Amsterdam, the Netherlands; Netherlands Heart Institute, Utrecht, the Netherlands.
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8
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Tardiff JC. The Role of Calcium/Calmodulin-Dependent Protein Kinase II Activation in Hypertrophic Cardiomyopathy. Circulation 2019; 134:1749-1751. [PMID: 27895024 DOI: 10.1161/circulationaha.116.025455] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Jil C Tardiff
- From Departments of Internal Medicine and Cellular and Molecular Medicine, University of Arizona, Tucson.
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9
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Lehman SJ, Tal-Grinspan L, Lynn ML, Strom J, Benitez GE, Anderson ME, Tardiff JC. Chronic Calmodulin-Kinase II Activation Drives Disease Progression in Mutation-Specific Hypertrophic Cardiomyopathy. Circulation 2019; 139:1517-1529. [PMID: 30586744 PMCID: PMC6461395 DOI: 10.1161/circulationaha.118.034549] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND Although the genetic causes of hypertrophic cardiomyopathy (HCM) are widely recognized, considerable lag in the development of targeted therapeutics has limited interventions to symptom palliation. This is in part attributable to an incomplete understanding of how point mutations trigger pathogenic remodeling. As a further complication, similar mutations within sarcomeric genes can result in differential disease severity, highlighting the need to understand the mechanism of progression at the molecular level. One pathway commonly linked to HCM progression is calcium homeostasis dysregulation, though how specific mutations disrupt calcium homeostasis remains unclear. METHODS To evaluate the effects of early intervention in calcium homeostasis, we used 2 mouse models of sarcomeric HCM (cardiac troponin T R92L and R92W) with differential myocellular calcium dysregulation and disease presentation. Two modes of intervention were tested: inhibition of the autoactivated calcium-dependent kinase (calmodulin kinase II [CaMKII]) via the AC3I peptide and diltiazem, an L-type calcium channel antagonist. Two-dimensional echocardiography was used to determine cardiac function and left ventricular remodeling, and atrial remodeling was monitored via atrial mass. Sarcoplasmic reticulum Ca2+ATPase activity was measured as an index of myocellular calcium handling and coupled to its regulation via the phosphorylation status of phospholamban. RESULTS We measured an increase in phosphorylation of CaMKII in R92W animals by 6 months of age, indicating increased autonomous activity of the kinase in these animals. Inhibition of CaMKII led to recovery of diastolic function and partially blunted atrial remodeling in R92W mice. This improved function was coupled to increased sarcoplasmic reticulum Ca2+ATPase activity in the R92W animals despite reduction of CaMKII activation, likely indicating improvement in myocellular calcium handling. In contrast, inhibition of CaMKII in R92L animals led to worsened myocellular calcium handling, remodeling, and function. Diltiazem-HCl arrested diastolic dysfunction progression in R92W animals only, with no improvement in cardiac remodeling in either genotype. CONCLUSIONS We propose a highly specific, mutation-dependent role of activated CaMKII in HCM progression and a precise therapeutic target for clinical management of HCM in selected cohorts. Moreover, the mutation-specific response elicited with diltiazem highlights the necessity to understand mutation-dependent progression at a molecular level to precisely intervene in disease progression.
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Affiliation(s)
- Sarah J. Lehman
- Department of Physiological Sciences, University of Arizona, Tucson, Arizona 85724, USA
| | - Lauren Tal-Grinspan
- Department of Medicine, Columbia University Medical Center, New York, New York 10032, USA
| | - Melissa L. Lynn
- Department of Medicine, University of Arizona, Tucson, Arizona, 85724, USA
| | - Joshua Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona 85724, USA
| | - Grace E. Benitez
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, 85724, USA
| | - Mark E. Anderson
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland 21287, USA
| | - Jil C. Tardiff
- Department of Medicine, University of Arizona, Tucson, Arizona, 85724, USA
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10
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Coppini R, Ferrantini C, Cerbai E. Novel pharmacological approaches for paediatric hypertrophic cardiomyopathy. PROGRESS IN PEDIATRIC CARDIOLOGY 2018. [DOI: 10.1016/j.ppedcard.2018.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
Hypertrophic cardiomyopathy (HCM) is most commonly transmitted as an autosomal dominant trait, caused by mutations in genes encoding cardiac sarcomere proteins1–3. Other inheritable causes of the disease include mutations in genes coding for proteins important in calcium handling or that form part of the cytoskeleton4–6. At present, the primary clinical role of genetic testing in HCM is to facilitate familial screening to allow the identification of individuals at risk of developing the disease7,8. It is also used to diagnose genocopies, such as lysosomal9–11 and glycogen storage disease which have different treatment strategies, rates of disease progression and prognosis12–14. The role of genetic testing in predicting prognosis is limited at present, but emerging data suggest that knowledge of the genetic basis of disease will assume an important role in disease stratification15–17 and offer potential targets for disease-modifying therapy in the near future18.
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Affiliation(s)
- Mohammed Akhtar
- Bart's Heart Centre, St Bartholomew's Hospital, London & University College London
| | - Perry Elliott
- Bart's Heart Centre, St Bartholomew's Hospital, London & University College London
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12
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Abstract
This article focuses on three "bins" that comprise sets of biophysical derangements elicited by cardiomyopathy-associated mutations in the myofilament. Current therapies focus on symptom palliation and do not address the disease at its core. We and others have proposed that a more nuanced classification could lead to direct interventions based on early dysregulation changing the trajectory of disease progression in the preclinical cohort. Continued research is necessary to address the complexity of cardiomyopathic progression and develop efficacious therapeutics.
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Affiliation(s)
- Melissa L Lynn
- Department of Medicine, University of Arizona, Room 317, 1656 East Mabel Street, Tucson, AZ 85724, USA
| | - Sarah J Lehman
- Department of Physiological Sciences, University of Arizona, Room 317, 1656 East Mabel Street, Tucson, AZ 85724, USA
| | - Jil C Tardiff
- Department of Medicine, University of Arizona, Room 312, 1656 East Mabel Street, Tucson, AZ 85724, USA.
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13
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Vakrou S, Fukunaga R, Foster DB, Sorensen L, Liu Y, Guan Y, Woldemichael K, Pineda-Reyes R, Liu T, Tardiff JC, Leinwand LA, Tocchetti CG, Abraham TP, O'Rourke B, Aon MA, Abraham MR. Allele-specific differences in transcriptome, miRNome, and mitochondrial function in two hypertrophic cardiomyopathy mouse models. JCI Insight 2018; 3:94493. [PMID: 29563334 DOI: 10.1172/jci.insight.94493] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 02/14/2018] [Indexed: 01/06/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) stems from mutations in sarcomeric proteins that elicit distinct biophysical sequelae, which in turn may yield radically different intracellular signaling and molecular pathologic profiles. These signaling events remain largely unaddressed by clinical trials that have selected patients based on clinical HCM diagnosis, irrespective of genotype. In this study, we determined how two mouse models of HCM differ, with respect to cellular/mitochondrial function and molecular biosignatures, at an early stage of disease. We show that hearts from young R92W-TnT and R403Q-αMyHC mutation-bearing mice differ in their transcriptome, miRNome, intracellular redox environment, mitochondrial antioxidant defense mechanisms, and susceptibility to mitochondrial permeability transition pore opening. Pathway analysis of mRNA-sequencing data and microRNA profiles indicate that R92W-TnT mutants exhibit a biosignature consistent with activation of profibrotic TGF-β signaling. Our results suggest that the oxidative environment and mitochondrial impairment in young R92W-TnT mice promote activation of TGF-β signaling that foreshadows a pernicious phenotype in young individuals. Of the two mutations, R92W-TnT is more likely to benefit from anti-TGF-β signaling effects conferred by angiotensin receptor blockers and may be responsive to mitochondrial antioxidant strategies in the early stage of disease. Molecular and functional profiling may therefore serve as aids to guide precision therapy for HCM.
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Affiliation(s)
- Styliani Vakrou
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Ryuya Fukunaga
- Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - D Brian Foster
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Lars Sorensen
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Yamin Liu
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA.,Division of Cardiology, UCSF, San Francisco, California, USA
| | - Yufan Guan
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA
| | - Kirubel Woldemichael
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA
| | - Roberto Pineda-Reyes
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA
| | - Ting Liu
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Jill C Tardiff
- Department of Internal Medicine and Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, USA
| | - Leslie A Leinwand
- Department of Molecular, Cellular, and Developmental Biology and the BioFrontiers Institute, University of Colorado, Boulder, Colorado, USA
| | - Carlo G Tocchetti
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Theodore P Abraham
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.,Division of Cardiology, UCSF, San Francisco, California, USA
| | - Brian O'Rourke
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Miguel A Aon
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - M Roselle Abraham
- Hypertrophic Cardiomyopathy Center of Excellence, Johns Hopkins University, Baltimore, Maryland, USA.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.,Division of Cardiology, UCSF, San Francisco, California, USA
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14
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Ren X, Schmidt W, Huang Y, Lu H, Liu W, Bu W, Eckenhoff R, Cammarato A, Gao WD. Fropofol decreases force development in cardiac muscle. FASEB J 2018. [PMID: 29522375 DOI: 10.1096/fj.201701442r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Supranormal contractile properties are frequently associated with cardiac diseases. Anesthetic agents, including propofol, can depress myocardial contraction. We tested the hypothesis that fropofol, a propofol derivative, reduces force development in cardiac muscles via inhibition of cross-bridge cycling and may therefore have therapeutic potential. Force and intracellular Ca2+ concentration ([Ca2+]i) transients of rat trabecular muscles were determined. Myofilament ATPase, actin-activated myosin ATPase, and velocity of actin filaments propelled by myosin were also measured. Fropofol dose dependently decreased force without altering [Ca2+]i in normal and pressure-induced hypertrophied-hypercontractile muscles. Similarly, fropofol depressed maximum Ca2+-activated force ( Fmax) and increased the [Ca2+]i required for 50% of Fmax (Ca50) at steady state without affecting the Hill coefficient in both intact and skinned cardiac fibers. The drug also depressed cardiac myofibrillar and actin-activated myosin ATPase activity. In vitro actin sliding velocity was significantly reduced when fropofol was introduced during rigor binding of cross-bridges. The data suggest that the depressing effects of fropofol on cardiac contractility are likely to be related to direct targeting of actomyosin interactions. From a clinical standpoint, these findings are particularly significant, given that fropofol is a nonanesthetic small molecule that decreases myocardial contractility specifically and thus may be useful in the treatment of hypercontractile cardiac disorders.-Ren, X., Schmidt, W., Huang, Y., Lu, H., Liu, W., Bu, W., Eckenhoff, R., Cammarato, A., Gao, W. D. Fropofol decreases force development in cardiac muscle.
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Affiliation(s)
- Xianfeng Ren
- Department of Anesthesiology, China-Japan Friendship Hospital, Beijing, China
| | - William Schmidt
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Yiyuan Huang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Haisong Lu
- Department of Anesthesiology, Fuwai Hospital, Beijing, China
| | - Wenjie Liu
- Department of Anesthesiology, South China University School of Medicine, China
| | - Weiming Bu
- Department of Anesthesiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Roderic Eckenhoff
- Department of Anesthesiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Wei Dong Gao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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15
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Ueda Y, Stern JA. A One Health Approach to Hypertrophic Cardiomyopathy. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2017; 90:433-448. [PMID: 28955182 PMCID: PMC5612186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease in humans and results in significant morbidity and mortality. Research over the past 25 years has contributed enormous insight into this inherited disease particularly in the areas of genetics, molecular mechanisms, and pathophysiology. Our understanding continues to be limited by the heterogeneity of clinical presentations with various genetic mutations associated with HCM. Transgenic mouse models have been utilized especially studying the genotypic and phenotypic interactions. However, mice possess intrinsic cardiac and hemodynamic differences compared to humans and have limitations preventing their direct translation. Other animal models of HCM have been studied or generated in part to overcome these limitations. HCM in cats shows strikingly similar molecular, histopathological, and genetic similarities to human HCM, and offers an important translational opportunity for the study of this disease. Recently, inherited left ventricular hypertrophy in rhesus macaques was identified and collaborative investigations have been conducted to begin to develop a non-human primate HCM model. These naturally-occurring large-animal models may aid in advancing our understanding of HCM and developing novel therapeutic approaches to this disease. This review will highlight the features of HCM in humans and the relevant available and developing animal models of this condition.
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Affiliation(s)
- Yu Ueda
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA
| | - Joshua A. Stern
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA,California National Primate Research Center, University of California-Davis, Davis, CA,To whom all correspondence should be addressed: Joshua A. Stern, One Shields Avenue, Davis, CA, 95616, Tel: 530-752-2475, .
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16
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Coppini R, Mazzoni L, Ferrantini C, Gentile F, Pioner JM, Laurino A, Santini L, Bargelli V, Rotellini M, Bartolucci G, Crocini C, Sacconi L, Tesi C, Belardinelli L, Tardiff J, Mugelli A, Olivotto I, Cerbai E, Poggesi C. Ranolazine Prevents Phenotype Development in a Mouse Model of Hypertrophic Cardiomyopathy. Circ Heart Fail 2017; 10:CIRCHEARTFAILURE.116.003565. [PMID: 28255011 DOI: 10.1161/circheartfailure.116.003565] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 01/30/2017] [Indexed: 01/04/2023]
Abstract
BACKGROUND Current therapies are ineffective in preventing the development of cardiac phenotype in young carriers of mutations associated with hypertrophic cardiomyopathy (HCM). Ranolazine, a late Na+ current blocker, reduced the electromechanical dysfunction of human HCM myocardium in vitro. METHODS AND RESULTS To test whether long-term treatment prevents cardiomyopathy in vivo, transgenic mice harboring the R92Q troponin-T mutation and wild-type littermates received an oral lifelong treatment with ranolazine and were compared with age-matched vehicle-treated animals. In 12-months-old male R92Q mice, ranolazine at therapeutic plasma concentrations prevented the development of HCM-related cardiac phenotype, including thickening of the interventricular septum, left ventricular volume reduction, left ventricular hypercontractility, diastolic dysfunction, left-atrial enlargement and left ventricular fibrosis, as evaluated in vivo using echocardiography and magnetic resonance. Left ventricular cardiomyocytes from vehicle-treated R92Q mice showed marked excitation-contraction coupling abnormalities, including increased diastolic [Ca2+] and Ca2+ waves, whereas cells from treated mutants were undistinguishable from those from wild-type mice. Intact trabeculae from vehicle-treated mutants displayed inotropic insufficiency, increased diastolic tension, and premature contractions; ranolazine treatment counteracted the development of myocardial mechanical abnormalities. In mutant myocytes, ranolazine inhibited the enhanced late Na+ current and reduced intracellular [Na+] and diastolic [Ca2+], ultimately preventing the pathological increase of calmodulin kinase activity in treated mice. CONCLUSIONS Owing to the sustained reduction of intracellular Ca2+ and calmodulin kinase activity, ranolazine prevented the development of morphological and functional cardiac phenotype in mice carrying a clinically relevant HCM-related mutation. Pharmacological inhibitors of late Na+ current are promising candidates for an early preventive therapy in young phenotype-negative subjects carrying high-risk HCM-related mutations.
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Affiliation(s)
- Raffaele Coppini
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.).
| | - Luca Mazzoni
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Cecilia Ferrantini
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Francesca Gentile
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Josè Manuel Pioner
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Annunziatina Laurino
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Lorenzo Santini
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Valentina Bargelli
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Matteo Rotellini
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Gianluca Bartolucci
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Claudia Crocini
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Leonardo Sacconi
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Chiara Tesi
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Luiz Belardinelli
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Jil Tardiff
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Alessandro Mugelli
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Iacopo Olivotto
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Elisabetta Cerbai
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
| | - Corrado Poggesi
- From the Department NeuroFarBa (R.C., L.M., T.L., L. Santini, V.B., G.B., A.M., E.C.) and Department of Experimental and Clinical Medicine (C.F., F.G., J.M.P., C.T., C.P.), University of Florence, Italy; European Laboratory for Non-linear Spectroscopy (LENS), University of Florence & National Institute of Optics (INO-CNR), Sesto Fiorentino, Italy (C.C., L. Sacconi); Gilead Sciences Inc., Foster City, CA (L.B.); Department of Cellular and Molecular Medicine University of Arizona at Tucson, USA (J.T.); and Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy (M.R., I.O.)
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17
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Lynn ML, Tal Grinspan L, Holeman TA, Jimenez J, Strom J, Tardiff JC. The structural basis of alpha-tropomyosin linked (Asp230Asn) familial dilated cardiomyopathy. J Mol Cell Cardiol 2017; 108:127-137. [PMID: 28600229 DOI: 10.1016/j.yjmcc.2017.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 05/31/2017] [Accepted: 06/02/2017] [Indexed: 01/05/2023]
Abstract
Recently, linkage analysis of two large unrelated multigenerational families identified a novel dilated cardiomyopathy (DCM)-linked mutation in the gene coding for alpha-tropomyosin (TPM1) resulting in the substitution of an aspartic acid for an asparagine (at residue 230). To determine how a single amino acid mutation in α-tropomyosin (Tm) can lead to a highly penetrant DCM we generated a novel transgenic mouse model carrying the D230N mutation. The resultant mouse model strongly phenocopied the early onset of cardiomyopathic remodeling observed in patients as significant systolic dysfunction was observed by 2months of age. To determine the precise cellular mechanism(s) leading to the observed cardiac pathology we examined the effect of the mutation on Ca2+ handling in isolated myocytes and myofilament activation in vitro. D230N-Tm filaments exhibited a reduced Ca2+ sensitivity of sliding velocity. This decrease in sensitivity was coupled to increase in the peak amplitude of Ca2+ transients. While significant, and consistent with other DCMs, these measurements are comprised of complex inputs and did not provide sufficient experimental resolution. We then assessed the primary structural effects of D230N-Tm. Measurements of the thermal unfolding of D230N-Tm vs WT-Tm revealed an increase in stability primarily affecting the C-terminus of the Tm coiled-coil. We conclude that the D230N-Tm mutation induces a decrease in flexibility of the C-terminus via propagation through the helical structure of the protein, thus decreasing the flexibility of the Tm overlap and impairing its ability to regulate contraction. Understanding this unique structural mechanism could provide novel targets for eventual therapeutic interventions in patients with Tm-linked cardiomyopathies.
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Affiliation(s)
- M L Lynn
- Department of Physiological Sciences, University of Arizona, Tucson, AZ 85724, United States
| | - L Tal Grinspan
- Department of Medicine, Columbia University, New York, NY 10032, United States
| | - T A Holeman
- Department of Physiological Sciences, University of Arizona, Tucson, AZ 85724, United States; Department of Chemistry, University of Arizona, Tucson, AZ 85721, United States
| | - J Jimenez
- Department of Medicine, Washington University in Saint Louis, St. Louis, MO 63130, United States
| | - J Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, United States
| | - J C Tardiff
- Department of Physiological Sciences, University of Arizona, Tucson, AZ 85724, United States; Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, United States; Department of Medicine, University of Arizona, Tucson, AZ 85724, United States.
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18
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Karam CN, Warren CM, Henze M, Banke NH, Lewandowski ED, Solaro RJ. Peroxisome proliferator-activated receptor-α expression induces alterations in cardiac myofilaments in a pressure-overload model of hypertrophy. Am J Physiol Heart Circ Physiol 2017; 312:H681-H690. [PMID: 28130336 DOI: 10.1152/ajpheart.00469.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 01/04/2017] [Accepted: 01/17/2017] [Indexed: 01/22/2023]
Abstract
Although alterations in fatty acid (FA) metabolism have been shown to have a negative impact on contractility of the hypertrophied heart, the targets of action remain elusive. In this study we compared the function of skinned fiber bundles from transgenic (Tg) mice that overexpress a relatively low level of the peroxisome proliferator-activated receptor α (PPARα), and nontransgenic (NTg) littermates. The mice (NTg-T and Tg-T) were stressed by transverse aortic constriction (TAC) and compared with shams (NTg-S and Tg-S). There was an approximate 4-fold increase in PPARα expression in Tg-S compared with NTg-S, but Tg-T hearts showed the same PPARα expression as NTg-T. Expression of PPARα did not alter the hypertrophic response to TAC but did reduce ejection fraction (EF) in Tg-T hearts compared with other groups. The rate of actomyosin ATP hydrolysis was significantly higher in Tg-S skinned fiber bundles compared with all other groups. Tg-T hearts showed an increase in phosphorylation of specific sites on cardiac myosin binding protein-C (cMyBP-C) and β-myosin heavy chain isoform. These results advance our understanding of potential signaling to the myofilaments induced by altered FA metabolism under normal and pathological states. We demonstrate that chronic and transient PPARα activation during pathological stress alters myofilament response to Ca2+ through a mechanism that is possibly mediated by MyBP-C phosphorylation and myosin heavy chain isoforms.NEW & NOTEWORTHY Data presented here demonstrate novel signaling to sarcomeric proteins by chronic alterations in fatty acid metabolism induced by PPARα. The mechanism involves modifications of key myofilament regulatory proteins modifying cross-bridge dynamics with differential effects in controls and hearts stressed by pressure overload.
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Affiliation(s)
- Chehade N Karam
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Chad M Warren
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Marcus Henze
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Natasha H Banke
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - E Douglas Lewandowski
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and.,Sanford Burnham Presbyterian Medical Discovery Institute, Orlando, Florida
| | - R John Solaro
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
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19
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Helms AS, Alvarado FJ, Yob J, Tang VT, Pagani F, Russell MW, Valdivia HH, Day SM. Genotype-Dependent and -Independent Calcium Signaling Dysregulation in Human Hypertrophic Cardiomyopathy. Circulation 2016; 134:1738-1748. [PMID: 27688314 PMCID: PMC5127749 DOI: 10.1161/circulationaha.115.020086] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 08/05/2016] [Indexed: 02/05/2023]
Abstract
BACKGROUND Aberrant calcium signaling may contribute to arrhythmias and adverse remodeling in hypertrophic cardiomyopathy (HCM). Mutations in sarcomere genes may distinctly alter calcium handling pathways. METHODS We analyzed gene expression, protein levels, and functional assays for calcium regulatory pathways in human HCM surgical samples with (n=25) and without (n=10) sarcomere mutations compared with control hearts (n=8). RESULTS Gene expression and protein levels for calsequestrin, L-type calcium channel, sodium-calcium exchanger, phospholamban, calcineurin, and calcium/calmodulin-dependent protein kinase type II (CaMKII) were similar in HCM samples compared with controls. CaMKII protein abundance was increased only in sarcomere-mutation HCM (P<0.001). The CaMKII target pT17-phospholamban was 5.5-fold increased only in sarcomere-mutation HCM (P=0.01), as was autophosphorylated CaMKII (P<0.01), suggestive of constitutive activation. Calcineurin (PPP3CB) mRNA was not increased, nor was RCAN1 mRNA level, indicating a lack of calcineurin activation. Furthermore, myocyte enhancer factor 2 and nuclear factor of activated T cell transcription factor activity was not increased in HCM, suggesting that calcineurin pathway activation is not an upstream cause of increased CAMKII protein abundance or activation. SERCA2A mRNA transcript levels were reduced in HCM regardless of genotype, as was sarcoplasmic endoplasmic reticular calcium ATPase 2/phospholamban protein ratio (45% reduced; P=0.03). 45Ca sarcoplasmic endoplasmic reticular calcium ATPaseuptake assay showed reduced uptake velocity in HCM regardless of genotype (P=0.01). The cardiac ryanodine receptor was not altered in transcript, protein, or phosphorylated (pS2808, pS2814) protein abundance, and [3H]ryanodine binding was not different in HCM, consistent with no major modification of the ryanodine receptor. CONCLUSIONS Human HCM demonstrates calcium mishandling through both genotype-specific and common pathways. Posttranslational activation of the CaMKII pathway is specific to sarcomere mutation-positive HCM, whereas sarcoplasmic endoplasmic reticular calcium ATPase 2 abundance and sarcoplasmic reticulum Ca uptake are depressed in both sarcomere mutation-positive and -negative HCM.
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Affiliation(s)
- Adam S Helms
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor.
| | - Francisco J Alvarado
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Jaime Yob
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Vi T Tang
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Francis Pagani
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Mark W Russell
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Héctor H Valdivia
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
| | - Sharlene M Day
- From Departments of Internal Medicine (A.S.H., J.Y., V.T.T., H.H.V., S.M.D.), Molecular and Integrative Physiology (F.J.A., H.H.V., S.M.D.), Cardiac Surgery (F.P.), and Pediatrics (M.W.R.), University of Michigan, Ann Arbor
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20
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Cheng Y, Regnier M. Cardiac troponin structure-function and the influence of hypertrophic cardiomyopathy associated mutations on modulation of contractility. Arch Biochem Biophys 2016; 601:11-21. [PMID: 26851561 PMCID: PMC4899195 DOI: 10.1016/j.abb.2016.02.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 01/30/2016] [Accepted: 02/02/2016] [Indexed: 11/29/2022]
Abstract
Cardiac troponin (cTn) acts as a pivotal regulator of muscle contraction and relaxation and is composed of three distinct subunits (cTnC: a highly conserved Ca(2+) binding subunit, cTnI: an actomyosin ATPase inhibitory subunit, and cTnT: a tropomyosin binding subunit). In this mini-review, we briefly summarize the structure-function relationship of cTn and its subunits, its modulation by PKA-mediated phosphorylation of cTnI, and what is known about how these properties are altered by hypertrophic cardiomyopathy (HCM) associated mutations of cTnI. This includes recent work using computational modeling approaches to understand the atomic-based structural level basis of disease-associated mutations. We propose a viewpoint that it is alteration of cTnC-cTnI interaction (rather than the Ca(2+) binding properties of cTn) per se that disrupt the ability of PKA-mediated phosphorylation at cTnI Ser-23/24 to alter contraction and relaxation in at least some HCM-associated mutations. The combination of state of the art biophysical approaches can provide new insight on the structure-function mechanisms of contractile dysfunction resulting cTnI mutations and exciting new avenues for the diagnosis, prevention, and even treatment of heart diseases.
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Affiliation(s)
- Yuanhua Cheng
- University of Washington, Department of Bioengineering, Seattle, WA, USA
| | - Michael Regnier
- University of Washington, Department of Bioengineering, Seattle, WA, USA.
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21
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Lang SE, Stevenson TK, Xu D, O'Connell R, Westfall MV. Functionally conservative substitutions at cardiac troponin I S43/45. Arch Biochem Biophys 2016; 601:42-7. [PMID: 26869200 PMCID: PMC4899172 DOI: 10.1016/j.abb.2016.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/13/2016] [Accepted: 02/01/2016] [Indexed: 12/22/2022]
Abstract
A phospho-null Ala substitution at protein kinase C (PKC)-targeted cardiac troponin I (cTnI) S43/45 reduces myocyte and cardiac contractile function. The goal of the current study was to test whether cTnIS43/45N is an alternative, functionally conservative substitution in cardiac myocytes. Partial and more extensive endogenous cTnI replacement was similar at 2 and 4 days after gene transfer, respectively, for epitope-tagged cTnI and cTnIS43/45N. This replacement did not significantly change thin filament stoichiometry. In functional studies, there were no significant changes in the amplitude and/or rates of contractile shortening and re-lengthening after this partial (2 days) and extensive (4 days) replacement with cTnIS43/45N. The cTnIS43/45N substitution also was not associated with adaptive changes in the myocyte Ca(2+) transient or in phosphorylation of the protein kinase A and C-targeted cTnIS23/24 site. These results provide evidence that cTnIS43/45N is a functionally conservative substitution, and may be appropriate for use as a phospho-null in rodent models designed for studies on PKC modulation of cardiac performance.
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Affiliation(s)
- Sarah E Lang
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Tamara K Stevenson
- Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dongyang Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ryan O'Connell
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Margaret V Westfall
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
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22
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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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23
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Gilda JE, Lai X, Witzmann FA, Gomes AV. Delineation of Molecular Pathways Involved in Cardiomyopathies Caused by Troponin T Mutations. Mol Cell Proteomics 2016; 15:1962-81. [PMID: 27022107 DOI: 10.1074/mcp.m115.057380] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Indexed: 11/06/2022] Open
Abstract
Familial hypertrophic cardiomyopathy (FHC) is associated with mild to severe cardiac problems and is the leading cause of sudden death in young people and athletes. Although the genetic basis for FHC is well-established, the molecular mechanisms that ultimately lead to cardiac dysfunction are not well understood. To obtain important insights into the molecular mechanism(s) involved in FHC, hearts from two FHC troponin T models (Ile79Asn [I79N] and Arg278Cys [R278C]) were investigated using label-free proteomics and metabolomics. Mutations in troponin T are the third most common cause of FHC, and the I79N mutation is associated with a high risk of sudden cardiac death. Most FHC-causing mutations, including I79N, increase the Ca(2+) sensitivity of the myofilament; however, the R278C mutation does not alter Ca(2+) sensitivity and is associated with a better prognosis than most FHC mutations. Out of more than 1200 identified proteins, 53 and 76 proteins were differentially expressed in I79N and R278C hearts, respectively, when compared with wild-type hearts. Interestingly, more than 400 proteins were differentially expressed when the I79N and R278C hearts were directly compared. The three major pathways affected in I79N hearts relative to R278C and wild-type hearts were the ubiquitin-proteasome system, antioxidant systems, and energy production pathways. Further investigation of the proteasome system using Western blotting and activity assays showed that proteasome dysfunction occurs in I79N hearts. Metabolomic results corroborate the proteomic data and suggest the glycolytic, citric acid, and electron transport chain pathways are important pathways that are altered in I79N hearts relative to R278C or wild-type hearts. Our findings suggest that impaired energy production and protein degradation dysfunction are important mechanisms in FHCs associated with poor prognosis and that cardiac hypertrophy is not likely needed for a switch from fatty acid to glucose metabolism.
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Affiliation(s)
| | - Xianyin Lai
- ¶Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Frank A Witzmann
- ¶Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Aldrin V Gomes
- From the ‡Department of Neurobiology, Physiology, and Behavior, §Department of Physiology and Membrane Biology, University of California, Davis, California 95616;
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24
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Abstract
Calcium binding and dissociation within the cardiac thin filament (CTF) is a fundamental regulator of normal contraction and relaxation. Although the disruption of this complex, allosterically mediated process has long been implicated in human disease, the precise atomic-level mechanisms remain opaque, greatly hampering the development of novel targeted therapies. To address this question, we used a fully atomistic CTF model to test both Ca(2+) binding strength and the energy required to remove Ca(2+) from the N-lobe binding site in WT and mutant troponin complexes that have been linked to genetic cardiomyopathies. This computational approach is combined with measurements of in vitro Ca(2+) dissociation rates in fully reconstituted WT and cardiac troponin T R92L and R92W thin filaments. These human disease mutations represent known substitutions at the same residue, reside at a significant distance from the calcium binding site in cardiac troponin C, and do not affect either the binding pocket affinity or EF-hand structure of the binding domain. Both have been shown to have significantly different effects on cardiac function in vivo. We now show that these mutations independently alter the interaction between the Ca(2+) ion and cardiac troponin I subunit. This interaction is a previously unidentified mechanism, in which mutations in one protein of a complex indirectly affect a third via structural and dynamic changes in a second to yield a pathogenic change in thin filament function that results in mutation-specific disease states. We can now provide atom-level insight that is potentially highly actionable in drug design.
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25
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Thompson BR, Metzger JM. Cell biology of sarcomeric protein engineering: disease modeling and therapeutic potential. Anat Rec (Hoboken) 2015; 297:1663-9. [PMID: 25125179 DOI: 10.1002/ar.22966] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 11/09/2022]
Abstract
The cardiac sarcomere is the functional unit for myocyte contraction. Ordered arrays of sarcomeric proteins, held in stoichiometric balance with each other, respond to calcium to coordinate contraction and relaxation of the heart. Altered sarcomeric structure-function underlies the primary basis of disease in multiple acquired and inherited heart disease states. Hypertrophic and restrictive cardiomyopathies are caused by inherited mutations in sarcomeric genes and result in altered contractility. Ischemia-mediated acidosis directly alters sarcomere function resulting in decreased contractility. In this review, we highlight the use of acute genetic engineering of adult cardiac myocytes through stoichiometric replacement of sarcomeric proteins in these disease states with particular focus on cardiac troponin I. Stoichiometric replacement of disease causing mutations has been instrumental in defining the molecular mechanisms of hypertrophic and restrictive cardiomyopathy in a cellular context. In addition, taking advantage of stoichiometric replacement through gene therapy is discussed, highlighting the ischemia-resistant histidine-button, A164H cTnI. Stoichiometric replacement of sarcomeric proteins offers a potential gene therapy avenue to replace mutant proteins, alter sarcomeric responses to pathophysiologic insults, or neutralize altered sarcomeric function in disease.
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Affiliation(s)
- Brian R Thompson
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota
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26
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Ho CY, Lakdawala NK, Cirino AL, Lipshultz SE, Sparks E, Abbasi SA, Kwong RY, Antman EM, Semsarian C, González A, López B, Diez J, Orav EJ, Colan SD, Seidman CE. Diltiazem treatment for pre-clinical hypertrophic cardiomyopathy sarcomere mutation carriers: a pilot randomized trial to modify disease expression. JACC. HEART FAILURE 2015; 3:180-8. [PMID: 25543971 PMCID: PMC4323670 DOI: 10.1016/j.jchf.2014.08.003] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Revised: 08/18/2014] [Accepted: 08/22/2014] [Indexed: 01/14/2023]
Abstract
OBJECTIVES The study sought to assess the safety, feasibility, and effect of diltiazem as disease-modifying therapy for at-risk hypertrophic cardiomyopathy (HCM) mutation carriers. BACKGROUND HCM is caused by sarcomere mutations and characterized by left ventricular hypertrophy (LVH) with increased risk of heart failure and sudden death. HCM typically cannot be diagnosed early in life, although subtle phenotypes are present. Animal studies indicate that intracellular calcium handling is altered before LVH develops. Furthermore, early treatment with diltiazem appeared to attenuate disease emergence. METHODS In a pilot, double-blind trial, we randomly assigned 38 sarcomere mutation carriers without LVH (mean 15.8 years of age) to therapy with diltiazem 360 mg/day (or 5 mg/kg/day) or placebo. Treatment duration ranged from 12 to 42 months (median 25 months). Study procedures included electrocardiography, echocardiography, cardiac magnetic resonance imaging, and serum biomarker measurement. RESULTS Diltiazem was not associated with serious adverse events. Heart rate and blood pressure did not differ significantly between groups. However, mean left ventricular (LV) end-diastolic diameter improved toward normal in the diltiazem group but decreased further in controls (change in z-scores, +0.6 vs. -0.5; p < 0.001). Mean LV thickness-to-dimension ratio was stable in the diltiazem group but increased in controls (-0.02 vs. +0.15; p = 0.04). Among MYBPC3 mutation carriers, LV wall thickness and mass, diastolic filling, and cardiac troponin I levels improved in those taking diltiazem compared with controls. Four participants developed overt HCM, 2 in each treatment group. CONCLUSIONS Pre-clinical administration of diltiazem is safe and may improve early LV remodeling in HCM. This novel strategy merits further exploration. (Treatment of Preclinical Hypertrophic Cardiomyopathy With Diltiazem; NCT00319982).
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Affiliation(s)
- Carolyn Y Ho
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
| | - Neal K Lakdawala
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts
| | - Allison L Cirino
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts
| | - Steven E Lipshultz
- Department of Pediatrics, Wayne State University School of Medicine, and Department of Cardiology, Children's Hospital of Michigan, Detroit, Michigan
| | - Elizabeth Sparks
- Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland
| | - Siddique A Abbasi
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts
| | - Raymond Y Kwong
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts
| | - Elliott M Antman
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts
| | - Christopher Semsarian
- Agnes Ginges Centre for Molecular Cardiology, Centenary Institute; Sydney Medical School, University of Sydney and Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Arantxa González
- Program of Cardiovascular Diseases, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain
| | - Begoña López
- Program of Cardiovascular Diseases, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain
| | - Javier Diez
- Program of Cardiovascular Diseases, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain; Department of Cardiology and Cardiac Surgery, University of Navarra Clinic, Pamplona, Spain
| | - E John Orav
- Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
| | | | - Christine E Seidman
- Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts; Howard Hughes Medical Institute, New York, New York
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27
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Ablorh NAD, Thomas DD. Phospholamban phosphorylation, mutation, and structural dynamics: a biophysical approach to understanding and treating cardiomyopathy. Biophys Rev 2015; 7:63-76. [PMID: 28509982 DOI: 10.1007/s12551-014-0157-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 11/26/2014] [Indexed: 01/16/2023] Open
Abstract
We review the recent development of novel biochemical and spectroscopic methods to determine the site-specific phosphorylation, expression, mutation, and structural dynamics of phospholamban (PLB), in relation to its function (inhibition of the cardiac calcium pump, SERCA2a), with specific focus on cardiac physiology, pathology, and therapy. In the cardiomyocyte, SERCA2a actively transports Ca2+ into the sarcoplasmic reticulum (SR) during relaxation (diastole) to create the concentration gradient that drives the passive efflux of Ca2+ required for cardiac contraction (systole). Unphosphorylated PLB (U-PLB) inhibits SERCA2a, but phosphorylation at S16 and/or T17 (producing P-PLB) changes the structure of PLB to relieve SERCA2a inhibition. Because insufficient SERCA2a activity is a hallmark of heart failure, SERCA2a activation, by gene therapy (Andino et al. 2008; Fish et al. 2013; Hoshijima et al. 2002; Jessup et al. 2011) or drug therapy (Ferrandi et al. 2013; Huang 2013; Khan et al. 2009; Rocchetti et al. 2008; Zhang et al. 2012), is a widely sought goal for treatment of heart failure. This review describes rational approaches to this goal. Novel biophysical assays, using site-directed labeling and high-resolution spectroscopy, have been developed to resolve the structural states of SERCA2a-PLB complexes in vitro and in living cells. Novel biochemical assays, using synthetic standards and multidimensional immunofluorescence, have been developed to quantitate PLB expression and phosphorylation states in cells and human tissues. The biochemical and biophysical properties of U-PLB, P-PLB, and mutant PLB will ultimately resolve the mechanisms of loss of inhibition and gain of inhibition to guide therapeutic development. These assays will be powerful tools for investigating human tissue samples from the Sydney Heart Bank, for the purpose of analyzing and diagnosing specific disorders.
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Affiliation(s)
- Naa-Adjeley D Ablorh
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.
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28
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Nonaka M, Morimoto S. Experimental models of inherited cardiomyopathy and its therapeutics. World J Cardiol 2014; 6:1245-1251. [PMID: 25548614 PMCID: PMC4278159 DOI: 10.4330/wjc.v6.i12.1245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/08/2014] [Accepted: 10/16/2014] [Indexed: 02/06/2023] Open
Abstract
Cardiomyopathy is a disease of myocardium categorized into three major forms, hypertrophic (HCM), dilated (DCM) and restrictive cardiomyopathy (RCM), which has recently been demonstrated to be a monogenic disease due to mutations in various proteins expressed in cardiomyocytes. Mutations in HCM and RCM typically increase the myofilament sensitivity to cytoplasmic Ca2+, leading to systolic hyperfunction and diastolic dysfunction. In contrast, mutations in DCM typically decrease the myofilament sensitivity to cytoplasmic Ca2+ and/or force generation/transmission, leading to systolic dysfunction. Creation of genetically-manipulated transgenic and knock-in animals expressing mutant proteins exogenously and endogenously, respectively, in their hearts provides valuable animal models to discover the molecular and cellular mechanisms for pathogenesis and promising therapeutic strategy in vivo. Recently, cardiomyocytes have been differentiated from patient’s induced pluripotent stem cells as a model of inherited cardiomyopathies in vitro. In this review, we provide overview of experimental models of cardiomyopathies with a focus on revealed molecular and cellular pathogenic mechanisms and potential therapeutics.
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29
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Marsiglia JDC, Pereira AC. Hypertrophic cardiomyopathy: how do mutations lead to disease? Arq Bras Cardiol 2014; 102:295-304. [PMID: 24714796 PMCID: PMC3987320 DOI: 10.5935/abc.20140022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/23/2013] [Indexed: 12/13/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common monogenic genetic cardiac
disease, with an estimated prevalence of 1:500 in the general population. Clinically,
HCM is characterized by hypertrophy of the left ventricle (LV) walls, especially the
septum, usually asymmetric, in the absence of any cardiac or systemic disease that
leads to a secondary hypertrophy. The clinical course of the disease has a large
inter- and intrafamilial heterogeneity, ranging from mild symptoms of heart failure
late in life to the onset of sudden cardiac death at a young age and is caused by a
mutation in one of the genes that encode a protein from the sarcomere, Z-disc or
intracellular calcium modulators. Although many genes and mutations are already known
to cause HCM, the molecular pathways that lead to the phenotype are still unclear.
This review focus on the molecular mechanisms of HCM, the pathways from mutation to
clinical phenotype and how the disease's genotype correlates with phenotype.
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Affiliation(s)
- Júlia Daher Carneiro Marsiglia
- Mailing Address: Júlia Daher Carneiro Marsiglia, Av. Dr. Enéas de
Carvalho Aguiar, 44, Cerqueira César. Postal Code 05403- 900, São Paulo, SP - Brazil.
E-mail: ;
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30
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Brenner B, Seebohm B, Tripathi S, Montag J, Kraft T. Familial hypertrophic cardiomyopathy: functional variance among individual cardiomyocytes as a trigger of FHC-phenotype development. Front Physiol 2014; 5:392. [PMID: 25346696 PMCID: PMC4193225 DOI: 10.3389/fphys.2014.00392] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/22/2014] [Indexed: 11/13/2022] Open
Abstract
Familial hypertrophic cardiomyopathy (FHC) is the most frequent inherited cardiac disease. It has been related to numerous mutations in many sarcomeric and even some non-sarcomeric proteins. So far, however, no common mechanism has been identified by which the many different mutations in different sarcomeric and non-sarcomeric proteins trigger development of the FHC phenotype. Here we show for different MYH7 mutations variance in force pCa-relations from normal to highly abnormal as a feature common to all mutations we studied, while direct functional effects of the different FHC-mutations, e.g., on force generation, ATPase or calcium sensitivity of the contractile system, can be quite different. The functional variation among individual M. soleus fibers of FHC-patients is accompanied by large variation in mutant vs. wildtype β-MyHC-mRNA. Preliminary results show a similar variation in mutant vs. wildtype β-MyHC-mRNA among individual cardiomyocytes. We discuss our previously proposed concept as to how different mutations in the β-MyHC and possibly other sarcomeric and non-sarcomeric proteins may initiate an FHC-phenotype by functional variation among individual cardiomyocytes that results in structural distortions within the myocardium, leading to cellular and myofibrillar disarray. In addition, distortions can activate stretch-sensitive signaling in cardiomyocytes and non-myocyte cells which is known to induce cardiac remodeling with interstitial fibrosis and hypertrophy. Such a mechanism will have major implications for therapeutic strategies to prevent FHC-development, e.g., by reducing functional imbalances among individual cardiomyocytes or by inhibition of their triggering of signaling paths initiating remodeling. Targeting increased or decreased contractile function would require selective targeting of mutant or wildtype protein to reduce functional imbalances.
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Affiliation(s)
- Bernhard Brenner
- Institute of Molecular and Cell Physiology, Hannover Medical School Hannover, Germany
| | - Benjamin Seebohm
- Institute of Molecular and Cell Physiology, Hannover Medical School Hannover, Germany
| | - Snigdha Tripathi
- Institute of Molecular and Cell Physiology, Hannover Medical School Hannover, Germany
| | - Judith Montag
- Institute of Molecular and Cell Physiology, Hannover Medical School Hannover, Germany
| | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School Hannover, Germany
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31
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Ablorh NAD, Dong X, James ZM, Xiong Q, Zhang J, Thomas DD, Karim CB. Synthetic phosphopeptides enable quantitation of the content and function of the four phosphorylation states of phospholamban in cardiac muscle. J Biol Chem 2014; 289:29397-405. [PMID: 25190804 DOI: 10.1074/jbc.m114.556621] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have studied the differential effects of phospholamban (PLB) phosphorylation states on the activity of the sarcoplasmic reticulum Ca-ATPase (SERCA). It has been shown that unphosphorylated PLB (U-PLB) inhibits SERCA and that phosphorylation of PLB at Ser-16 or Thr-17 relieves this inhibition in cardiac sarcoplasmic reticulum. However, the levels of the four phosphorylation states of PLB (U-PLB, P16-PLB, P17-PLB, and doubly phosphorylated 2P-PLB) have not been measured quantitatively in cardiac tissue, and their functional effects on SERCA have not been determined directly. We have solved both problems through the chemical synthesis of all four PLB species. We first used the synthetic PLB as standards for a quantitative immunoblot assay, to determine the concentrations of all four PLB phosphorylation states in pig cardiac tissue, with and without left ventricular hypertrophy (LVH) induced by aortic banding. In both LVH and sham hearts, all phosphorylation states were significantly populated, but LVH hearts showed a significant decrease in U-PLB, with a corresponding increase in the ratio of total phosphorylated PLB to U-PLB. To determine directly the functional effects of each PLB species, we co-reconstituted each of the synthetic peptides in phospholipid membranes with SERCA and measured calcium-dependent ATPase activity. SERCA inhibition was maximally relieved by P16-PLB (the most highly populated PLB state in cardiac tissue homogenates), followed by 2P-PLB, then P17-PLB. These results show that each PLB phosphorylation state uniquely alters Ca(2+) homeostasis, with important implications for cardiac health, disease, and therapy.
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Affiliation(s)
| | - Xiaoqiong Dong
- From the Departments of Biochemistry, Molecular Biology and Biophysics and
| | - Zachary M James
- From the Departments of Biochemistry, Molecular Biology and Biophysics and
| | - Qiang Xiong
- Medicine, University of Minnesota, Minneapolis, Minnesota 55455
| | - Jianyi Zhang
- Medicine, University of Minnesota, Minneapolis, Minnesota 55455
| | - David D Thomas
- From the Departments of Biochemistry, Molecular Biology and Biophysics and
| | - Christine B Karim
- From the Departments of Biochemistry, Molecular Biology and Biophysics and
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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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Vakrou S, Abraham MR. Hypertrophic cardiomyopathy: a heart in need of an energy bar? Front Physiol 2014; 5:309. [PMID: 25191275 PMCID: PMC4137386 DOI: 10.3389/fphys.2014.00309] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 07/30/2014] [Indexed: 01/08/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) has been recently recognized as the most common inherited cardiovascular disorder, affecting 1 in 500 adults worldwide. HCM is characterized by myocyte hypertrophy resulting in thickening of the ventricular wall, myocyte disarray, interstitial and/or replacement fibrosis, decreased ventricular cavity volume and diastolic dysfunction. HCM is also the most common cause of sudden death in the young. A large proportion of patients diagnosed with HCM have mutations in sarcomeric proteins. However, it is unclear how these mutations lead to the cardiac phenotype, which is variable even in patients carrying the same causal mutation. Abnormalities in calcium cycling, oxidative stress, mitochondrial dysfunction and energetic deficiency have been described constituting the basis of therapies in experimental models of HCM and HCM patients. This review focuses on evidence supporting the role of cellular metabolism and mitochondria in HCM.
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Affiliation(s)
- Styliani Vakrou
- Division of Cardiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| | - M Roselle Abraham
- Division of Cardiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
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Puglisi JL, Goldspink PH, Gomes AV, Utter MS, Bers DM, Solaro RJ. Influence of a constitutive increase in myofilament Ca(2+)-sensitivity on Ca(2+)-fluxes and contraction of mouse heart ventricular myocytes. Arch Biochem Biophys 2014; 552-553:50-9. [PMID: 24480308 PMCID: PMC4043955 DOI: 10.1016/j.abb.2014.01.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/02/2014] [Accepted: 01/18/2014] [Indexed: 11/25/2022]
Abstract
Chronic increases in myofilament Ca(2+)-sensitivity in the heart are known to alter gene expression potentially modifying Ca(2+)-homeostasis and inducing arrhythmias. We tested age-dependent effects of a chronic increase in myofilament Ca(2+)-sensitivity on induction of altered alter gene expression and activity of Ca(2+) transport systems in cardiac myocytes. Our approach was to determine the relative contributions of the major mechanisms responsible for restoring Ca(2+) to basal levels in field stimulated ventricular myocytes. Comparisons were made from ventricular myocytes isolated from non-transgenic (NTG) controls and transgenic mice expressing the fetal, slow skeletal troponin I (TG-ssTnI) in place of cardiac TnI (cTnI). Replacement of cTnI by ssTnI induces an increase in myofilament Ca(2+)-sensitivity. Comparisons included myocytes from relatively young (5-7months) and older mice (11-13months). Employing application of caffeine in normal Tyrode and in 0Na(+) 0Ca(2+) solution, we were able to dissect the contribution of the sarcoplasmic reticulum Ca(2+) pump (SR Ca(2+)-ATPase), the Na(+)/Ca(2+) exchanger (NCX), and "slow mechanisms" representing the activity of the sarcolemmal Ca(2+) pump and the mitochondrial Ca(2+) uniporter. The relative contribution of the SR Ca(2+)-ATPase to restoration of basal Ca(2+) levels in younger TG-ssTnI myocytes was lower than in NTG (81.12±2.8% vs 92.70±1.02%), but the same in the older myocytes. Younger and older NTG myocytes demonstrated similar contributions from the SR Ca(2+)-ATPase and NCX to restoration of basal Ca(2+). However, the slow mechanisms for Ca(2+) removal were increased in the older NTG (3.4±0.3%) vs the younger NTG myocytes (1.4±0.1%). Compared to NTG, younger TG-ssTnI myocytes demonstrated a significantly bigger contribution of the NCX (16±2.7% in TG vs 6.9±0.9% in NTG) and slow mechanisms (3.3±0.4% in TG vs 1.4±0.1% in NTG). In older TG-ssTnI myocytes the contributions were not significantly different from NTG (NCX: 4.9±0.6% in TG vs 5.5±0.7% in NTG; slow mechanisms: 2.5±0.3% in TG vs 3.4±0.3% in NTG). Our data indicate that constitutive increases in myofilament Ca(2+)-sensitivity alter the relative significance of the NCX transport system involved in Ca(2+)-homeostasis only in a younger group of mice. This modification may be of significance in early changes in altered gene expression and electrical stability hearts with increased myofilament Ca-sensitivity.
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Affiliation(s)
- Jose L Puglisi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, United States
| | - Paul H Goldspink
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Aldrin V Gomes
- Department of Neurobiology, Physiology, and Behavior, University of California Davis, Davis, CA 95616, United States
| | - Megan S Utter
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, Davis, CA 95616, United States
| | - R John Solaro
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States.
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Ku HC, Su MJ. DPP4 deficiency preserved cardiac function in abdominal aortic banding rats. PLoS One 2014; 9:e85634. [PMID: 24416433 PMCID: PMC3887072 DOI: 10.1371/journal.pone.0085634] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 12/06/2013] [Indexed: 01/21/2023] Open
Abstract
Dipeptidyl peptidase-4 (DPP4) enzyme inhibition has been reported to increase plasma glucagon-like peptide-1 (GLP-1) level for controlling postprandial glucose concentration. A prominent GLP-1 level in DPP4-deficient rats contributed to the resistance of endotoxemia and myocardial infarction. DPP4 deficiency also increased the capability against H₂O₂-induced stress in cardiomyocyte. However, long term effect of loss DPP4 activity on cardiac performance remained unclear. We used abdominal aortic banding (AAB) to induce pressure overload in wild-type and DPP4-deficient rats, and investigated the progression of heart failure. Cardiac histology and function were determined. Blood sample was collected for the plasma biochemical marker measurement. Heart weight to body weight ratio increased 1.2-fold after 6 weeks of AAB surgery. Cardiac function was compensated against pressure overload after 6 weeks of AAB surgery, but progressed to deterioration after 10 weeks of AAB surgery. AAB induced cardiac dysfunction was alleviated in DPP4-deficient rats. DPP4 activity increased significantly in wild-type rats after 10 weeks of AAB surgery, but remained unchanged in DPP4-deficient rats. In contrast, GLP-1 concentration was elevated by AAB after 6 weeks of surgery in DPP4-deficient rats, and remained high after 10 weeks of surgery. Ang II level markedly increased after 6 weeks of AAB surgery, but were less in DPP4-deficient rats. Massive collagen deposits in wild-type rat hearts appeared after 10 weeks of AAB surgery, which were alleviated in DPP4-deficient rats. Long term deficiency of DPP4 activity improved cardiac performance against pressure overload in rat, which may be attributed to a great quantity of GLP-1 accumulation during AAB.
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Affiliation(s)
- Hui-Chun Ku
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ming-Jai Su
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
- * E-mail:
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Viswanathan MC, Kaushik G, Engler AJ, Lehman W, Cammarato A. A Drosophila melanogaster model of diastolic dysfunction and cardiomyopathy based on impaired troponin-T function. Circ Res 2013; 114:e6-17. [PMID: 24221941 DOI: 10.1161/circresaha.114.302028] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE Regulation of striated muscle contraction is achieved by Ca2+ -dependent steric modulation of myosin cross-bridge cycling on actin by the thin filament troponin-tropomyosin complex. Alterations in the complex can induce contractile dysregulation and disease. For example, mutations between or near residues 112 to 136 of cardiac troponin-T, the crucial TnT1 (N-terminal domain of troponin-T)-tropomyosin-binding region, cause cardiomyopathy. The Drosophila upheld(101) Glu/Lys amino acid substitution lies C-terminally adjacent to this phylogenetically conserved sequence. OBJECTIVE Using a highly integrative approach, we sought to determine the molecular trigger of upheld(101) myofibrillar degeneration, to evaluate contractile performance in the mutant cardiomyocytes, and to examine the effects of the mutation on the entire Drosophila heart to elucidate regulatory roles for conserved TnT1 regions and provide possible mechanistic insight into cardiac dysfunction. METHODS AND RESULTS Live video imaging of Drosophila cardiac tubes revealed that the troponin-T mutation prolongs systole and restricts diastolic dimensions of the heart, because of increased numbers of actively cycling myosin cross-bridges. Elevated resting myocardial stiffness, consistent with upheld(101) diastolic dysfunction, was confirmed by an atomic force microscopy-based nanoindentation approach. Direct visualization of mutant thin filaments via electron microscopy and 3-dimensional reconstruction resolved destabilized tropomyosin positioning and aberrantly exposed myosin-binding sites under low Ca2+ conditions. CONCLUSIONS As a result of troponin-tropomyosin dysinhibition, upheld(101) hearts exhibited cardiac dysfunction and remodeling comparable to that observed during human restrictive cardiomyopathy. Thus, reversal of charged residues about the conserved tropomyosin-binding region of TnT1 may perturb critical intermolecular associations required for proper steric regulation, which likely elicits myopathy in our Drosophila model.
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Affiliation(s)
- Meera Cozhimuttam Viswanathan
- From the Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (M.C.V., A.C.); Department of Bioengineering, University of California, San Diego, La Jolla, CA (G.K., A.J.E.); and Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA (W.L.)
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McKee LA, Chen H, Regan JA, Behunin SM, Walker JW, Walker JS, Konhilas JP. Sexually dimorphic myofilament function and cardiac troponin I phosphospecies distribution in hypertrophic cardiomyopathy mice. Arch Biochem Biophys 2013; 535:39-48. [PMID: 23352598 PMCID: PMC3640654 DOI: 10.1016/j.abb.2012.12.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/12/2012] [Accepted: 12/14/2012] [Indexed: 11/16/2022]
Abstract
The pathological progression of hypertrophic cardiomyopathy (HCM) is sexually dimorphic such that male HCM mice develop phenotypic indicators of cardiac disease well before female HCM mice. Here, we hypothesized that alterations in myofilament function underlies, in part, this sex dimorphism in HCM disease development. Firstly, 10-12month female HCM (harboring a mutant [R403Q] myosin heavy chain) mice presented with proportionately larger hearts than male HCM mice. Next, we determined Ca(2+)-sensitive tension development in demembranated cardiac trabeculae excised from 10-12month female and male HCM mice. Whereas HCM did not impact Ca(2+)-sensitive tension development in male trabeculae, female HCM trabeculae were more sensitive to Ca(2+) than wild-type (WT) counterparts and both WT and HCM males. We hypothesized that the underlying cause of this sex difference in Ca(2+)-sensitive tension development was due to changes in Ca(2+) handling and sarcomeric proteins, including expression of SR Ca(2+) ATPase (2a) (SERCA2a), β-myosin heavy chain (β-MyHC) and post-translational modifications of myofilament proteins. Female HCM hearts showed an elevation of SERCA2a and β-MyHC protein whereas male HCM hearts showed a similar elevation of β-MyHC protein but a reduced level of cardiac troponin T (cTnT) phosphorylation. We also measured the distribution of cardiac troponin I (cTnI) phosphospecies using phosphate-affinity SDS-PAGE. The distribution of cTnI phosphospecies depended on sex and HCM. In conclusion, female and male HCM mice display sex dimorphic myofilament function that is accompanied by a sex- and HCM-dependent distribution of sarcomeric proteins and cTnI phosphospecies.
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Affiliation(s)
- Laurel A.K. McKee
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Hao Chen
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Jessica A. Regan
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Samantha M. Behunin
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Jeffery W. Walker
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - John S. Walker
- University of Colorado Denver, Department of Medicine/Cardiology, Aurora, CO 80045, USA
| | - John P. Konhilas
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
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Moore RK, Grinspan LT, Jimenez J, Guinto PJ, Ertz-Berger B, Tardiff JC. HCM-linked ∆160E cardiac troponin T mutation causes unique progressive structural and molecular ventricular remodeling in transgenic mice. J Mol Cell Cardiol 2013; 58:188-98. [PMID: 23434821 PMCID: PMC3819192 DOI: 10.1016/j.yjmcc.2013.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 01/11/2013] [Accepted: 02/02/2013] [Indexed: 01/27/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is a primary disease of the cardiac muscle, and one of the most common causes of sudden cardiac death (SCD) in young people. Many mutations in cardiac troponin T (cTnT) lead to a complex form of HCM with varying degrees of ventricular hypertrophy and ~65% of all cTnT mutations occur within or flanking the elongated N-terminal TNT1 domain. Biophysical studies have predicted that distal TNT1 mutations, including Δ160E, cause disease by a novel, yet unknown mechanism as compared to N-terminal mutations. To begin to address the specific effects of this commonly observed cTnT mutation we generated two independent transgenic mouse lines carrying variant doses of the mutant transgene. Hearts from the 30% and 70% cTnT Δ160E lines demonstrated a highly unique, dose-dependent disruption in cellular and sarcomeric architecture and a highly progressive pattern of ventricular remodeling. While adult ventricular myocytes isolated from Δ160E transgenic mice exhibited dosage-independent mechanical impairments, decreased sarcoplasmic reticulum calcium load and SERCA2a calcium uptake activity, the observed decreases in calcium transients were dosage-dependent. The latter findings were concordant with measures of calcium regulatory protein abundance and phosphorylation state. Finally, studies of whole heart physiology in the isovolumic mode demonstrated dose-dependent differences in the degree of cardiac dysfunction. We conclude that the observed clinical severity of the cTnT Δ160E mutation is caused by a combination of direct sarcomeric disruption coupled to a profound dysregulation of Ca(2+) homeostasis at the cellular level that results in a unique and highly progressive pattern of ventricular remodeling.
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Affiliation(s)
- Rachel K Moore
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Yeshiva University, 1300 Morris Park Avenue, Ullmann, Room 316, Bronx, NY 10461, USA
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Abstract
PURPOSE OF REVIEW Hypertrophic cardiomyopathy (HCM), the most common inherited cardiac disorder, exhibits remarkable genetic and clinical heterogeneity. This manuscript reviews recent discoveries of disease-causing genes and their clinical consequences, and provides an overview of research that aims to elucidate how HCM ensues from a single-nucleotide mutation. RECENT FINDINGS The spectrum of genes that are mutated in HCM has expanded. In combination with newly developed sequencing technologies, there are now robust strategies for gene-based diagnosis in HCM. Understanding the molecular pathophysiology of HCM has emerged from the study of genetically engineered animal models of disease, and new data indicate important roles for altered intracellular Ca²⁺ regulation and oxidative stress. Pharmacologic strategies to normalize these processes show promise in attenuating HCM in experimental models. SUMMARY The current repertoire of HCM genes allows effective gene-based diagnosis, information that enables accurate assessment of disease risk in family members, and provides some insight into clinical course. From mechanistic insights gleaned from fundamental investigations of experimental HCM models, novel therapeutic targets that may provide new benefits for HCM patients have surfaced.
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Lakdawala NK, Thune JJ, Colan SD, Cirino AL, Farrohi F, Rivero J, McDonough B, Sparks E, Orav EJ, Seidman JG, Seidman CE, Ho CY. Subtle abnormalities in contractile function are an early manifestation of sarcomere mutations in dilated cardiomyopathy. ACTA ACUST UNITED AC 2012; 5:503-10. [PMID: 22949430 DOI: 10.1161/circgenetics.112.962761] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Sarcomere mutations cause both dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM); however, the steps leading from mutation to disease are not well described. By studying mutation carriers before a clinical diagnosis develops, we characterize the early manifestations of sarcomere mutations in DCM and investigate how these manifestations differ from sarcomere mutations associated with HCM. METHODS AND RESULTS Sixty-two genotyped individuals in families with sarcomeric DCM underwent clinical evaluation including strain echocardiography. The group included 12 subclinical DCM mutation carriers with normal cardiac dimensions and left ventricular ejection fraction (LVEF ≥55%), 21 overt DCM subjects, and 29 related mutation (-) normal controls. Results were compared with a previously characterized cohort of 60 subclinical HCM subjects (sarcomere mutation carriers without left ventricular hypertrophy). Systolic myocardial tissue velocity, longitudinal, circumferential, and radial strain, and longitudinal and radial strain rate were reduced by 10%-23% in subclinical DCM mutation carriers compared with controls (P<0.001 for all comparisons), after adjusting for age and family relations. No significant differences in diastolic parameters were identified comparing the subclinical and control cohorts. The opposite pattern of contractile abnormalities with reduced diastolic but preserved systolic function was seen in subclinical HCM. CONCLUSIONS Subtle abnormalities in systolic function are present in subclinical DCM mutation carriers, despite normal left ventricular size and ejection fraction. In contrast, impaired relaxation and preserved systolic function appear to be the predominant early manifestations of sarcomere mutations that lead to HCM. These findings support the theory that the mutation's intrinsic impact on sarcomere function influences whether a dilated or hypertrophic phenotype develops.
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Affiliation(s)
- Neal K Lakdawala
- Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA
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He H, Hoyer K, Tao H, Rice R, Jimenez J, Tardiff JC, Ingwall JS. Myosin-driven rescue of contractile reserve and energetics in mouse hearts bearing familial hypertrophic cardiomyopathy-associated mutant troponin T is mutation-specific. J Physiol 2012; 590:5371-88. [PMID: 22907055 DOI: 10.1113/jphysiol.2012.234252] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The thin filament protein troponin T (TnT) is a regulator of sarcomere function. Whole heart energetics and contractile reserve are compromised in transgenic mice bearing missense mutations at R92 within the tropomyosin-binding domain of cTnT, despite being distal to the ATP hydrolysis domain of myosin. These mutations are associated with familial hypertrophic cardiomyopathy (FHC). Here we test the hypothesis that genetically replacing murine αα-MyHC with murine ββ-MyHC in hearts bearing the R92Q cTnT mutation, a particularly lethal FHC-associated mutation, leads to sufficiently large perturbations in sarcomere function to rescue whole heart energetics and decrease the cost of contraction. By comparing R92Q cTnT and R92L cTnT mutant hearts, we also test whether any rescue is mutation-specific. We defined the energetic state of the isolated perfused heart using (31)P-NMR spectroscopy while simultaneously measuring contractile performance at four work states. We found that the cost of increasing contraction in intact mouse hearts with R92Q cTnT depends on the type of myosin present in the thick filament. We also found that the salutary effect of this manoeuvre is mutation-specific, demonstrating the major regulatory role of cTnT on sarcomere function at the whole heart level.
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Affiliation(s)
- Huamei He
- NMR Laboratory for Physiological Chemistry, Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
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Sadayappan S, de Tombe PP. Cardiac myosin binding protein-C: redefining its structure and function. Biophys Rev 2012; 4:93-106. [PMID: 22707987 PMCID: PMC3374655 DOI: 10.1007/s12551-012-0067-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 01/13/2012] [Indexed: 01/10/2023] Open
Abstract
Mutations of cardiac myosin binding protein-C (cMyBP-C) are inherited by an estimated 60 million people worldwide, and the protein is the target of several kinases. Recent evidence further suggests that cMyBP-C mutations alter Ca(2+) transients, leading to electrophysiological dysfunction. Thus, while the importance of studying this cardiac sarcomere protein is clear, preliminary data in the literature have raised many questions. Therefore, in this article, we propose to review the structure and function of cMyBP-C with particular respect to the role(s) in cardiac contractility and whether its release into the circulatory system is a potential biomarker of myocardial infarction. We also discuss future directions and experimental designs that may lead to expanding the role(s) of cMyBP-C in the heart. In conclusion, we suggest that cMyBP-C is a regulatory protein that could offer a broad clinical utility in maintaining normal cardiac function.
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Affiliation(s)
- Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, 2160 South First Ave., Maywood, IL 60153 USA
| | - Pieter P. de Tombe
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, 2160 South First Ave., Maywood, IL 60153 USA
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Ablorh NA, Miller T, Nitu F, Gruber SJ, Karim C, Thomas DD. Accurate quantitation of phospholamban phosphorylation by immunoblot. Anal Biochem 2012; 425:68-75. [PMID: 22369895 DOI: 10.1016/j.ab.2012.01.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 01/24/2012] [Accepted: 01/26/2012] [Indexed: 01/16/2023]
Abstract
We have developed a quantitative immunoblot method to measure the mole fraction of phospholamban (PLB) phosphorylated at Ser16 (X(p)) in biological samples. In cardiomyocytes, PLB phosphorylation activates the sarcoplasmic reticulum calcium ATPase (SERCA), which reduces cytoplasmic Ca(2+) to relax the heart during diastole. Unphosphorylated PLB (uPLB) inhibits SERCA at low [Ca(2+)] but phosphorylated PLB (pPLB) is less inhibitory, so myocardial physiology and pathology depend critically on X(p). Current methods of X(p) determination by immunoblot provide moderate precision but poor accuracy. We have solved this problem using purified uPLB and pPLB standards produced by solid-phase peptide synthesis. In each assay, a pair of blots is performed with identical standards and unknowns using antibodies partially selective for uPLB and pPLB, respectively. When performed on mixtures of uPLB and pPLB, the assay measures both total PLB (tPLB) and X(p) with accuracy of 96% or better. We assayed pig cardiac sarcoplasmic reticulum (SR) and found that X(p) varied widely among four animals, from 0.08 to 0.38, but there was remarkably little variation in the ratios of X(p)/tPLB and uPLB/SERCA, suggesting that PLB phosphorylation is tuned to maintain homeostasis in SERCA regulation.
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Affiliation(s)
- Naa-Adjeley Ablorh
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, 55455, USA
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Ashrafian H, McKenna WJ, Watkins H. Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy. Circ Res 2011; 109:86-96. [PMID: 21700950 DOI: 10.1161/circresaha.111.242974] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.
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Affiliation(s)
- Houman Ashrafian
- Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom
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Abstract
Sixteen years ago, mutations in cardiac troponin (Tn)T and α-tropomyosin were linked to familial hypertrophic cardiomyopathy, thus transforming the disorder from a disease of the β-myosin heavy chain to a disease of the cardiac sarcomere. From the outset, studies suggested that mutations in the regulatory thin filament caused a complex, heterogeneous pattern of ventricular remodeling with wide variations in clinical expression. To date, the clinical heterogeneity is well matched by an extensive array of nearly 100 independent mutations in all components of the cardiac thin filament. Significant advances in our understanding of the biophysics of myofilament activation, coupled to the emerging evidence that thin filament linked cardiomyopathies are progressive, suggests that a renewed focus on the most proximal events in both the molecular and clinical pathogenesis of the disease will be necessary to achieve the central goal of using genotype information to manage affected patients. In this review, we examine the existing biophysical and clinical evidence in support of a more proximal definition of thin filament cardiomyopathies. In addition, new high-resolution, integrated approaches are presented to help define the way forward as the field works toward developing a more robust link between genotype and phenotype in this complex disorder.
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Affiliation(s)
- Jil C Tardiff
- Department of Physiology and Biophysics, Department of Internal Medicine, Division of Adult Cardiology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Rice R, Guinto P, Dowell-Martino C, He H, Hoyer K, Krenz M, Robbins J, Ingwall JS, Tardiff JC. Cardiac myosin heavy chain isoform exchange alters the phenotype of cTnT-related cardiomyopathies in mouse hearts. J Mol Cell Cardiol 2009; 48:979-88. [PMID: 20004663 DOI: 10.1016/j.yjmcc.2009.11.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Revised: 11/12/2009] [Accepted: 11/28/2009] [Indexed: 11/28/2022]
Abstract
Familial hypertrophic cardiomyopathy, FHC, is a clinically heterogeneous, autosomal-dominant disease of the cardiac sarcomere leading to extensive remodeling at both the whole heart and molecular levels. The remodeling patterns are mutation-specific, a finding that extends to the level of single amino acid substitutions at the same peptide residue. Here we utilize two well-characterized transgenic FHC mouse models carrying independent amino acid substitutions in the TM-binding region of cardiac troponin T (cTnT) at residue 92. R92Q and R92L cTnT domains have mutation-specific average peptide conformation and dynamics sufficient to alter thin filament flexibility and cross-bridge formation and R92 mutant myocytes demonstrate mutation-specific temporal molecular remodeling of Ca(2+) kinetics and impaired cardiac contractility and relaxation. To determine if a greater economy of contraction at the crossbridge level would rescue the mechanical defects caused by the R92 cTnT mutations, we replaced the endogenous murine alpha-myosin heavy chain (MyHC) with the beta-MyHC isoform. While beta-MyHC replacement rescued the systolic dysfunction in R92Q mice, it failed to rescue the defects in diastolic function common to FHC-associated R92 mutations. Surprisingly, a significant component of the whole heart and molecular contractile improvement in the R92Q mice was due to improvements in Ca(2+) homeostasis including SR uptake, [Ca2+](i) amplitude and phospholamban phosphorylation. Our data demonstrate that while genetically altering the myosin composition of the heart bearing a thin filament FHC mutation is sufficient to improve contractility, diastolic performance is refractory despite improved Ca(2+) kinetics. These data reveal a previously unrecognized role for MyHC isoforms with respect to Ca(2+) homeostasis in the setting of cardiomyopathic remodeling and demonstrate the overall dominance of the thin filament mutation in determining the degree of diastolic impairment at the myofilament level.
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Affiliation(s)
- Ron Rice
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Yeshiva University, 1300 Morris Park Avenue, Ullmann, Room 316, Bronx, NY 10461, USA
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