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Bai J, Wei X. Identification of teleost tnnc1a enhancers for specific pan-cardiac transcription. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.26.582099. [PMID: 38464177 PMCID: PMC10925198 DOI: 10.1101/2024.02.26.582099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Troponin C regulates muscle contraction by forming the troponin complex with troponin I and troponin T. Different muscle types express different troponin C genes. The mechanisms of such differential transcription are not fully understood. The Zebrafish tnnc1a gene is restrictively expressed in cardiac muscles. We here identify the enhancers and promoters of the zebrafish and medaka tnnc1a genes, including intronic enhancers in zebrafish and medaka and an upstream enhancer in the medaka. The intronic and upstream enhancers are likely functionally redundant. The GFP transgenic reporter driven by these enhancers is expressed more strongly in the ventricle than in the atrium, recapitulating the expression pattern of the endogenous zebrafish tnnc1a gene. Our study identifies a new set of enhancers for cardiac-specific transgenic expression in zebrafish. These enhancers can serve as tools for future identification of transcription factor networks that drive cardiac-specific gene transcription.
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Rayani K, Hantz ER, Haji-Ghassemi O, Li AY, Spuches AM, Van Petegem F, Solaro RJ, Lindert S, Tibbits GF. The effect of Mg 2+ on Ca 2+ binding to cardiac troponin C in hypertrophic cardiomyopathy associated TNNC1 variants. FEBS J 2022; 289:7446-7465. [PMID: 35838319 PMCID: PMC9836626 DOI: 10.1111/febs.16578] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 05/14/2022] [Accepted: 07/13/2022] [Indexed: 01/14/2023]
Abstract
Cardiac troponin C (cTnC) is the critical Ca2+ -sensing component of the troponin complex. Binding of Ca2+ to cTnC triggers a cascade of conformational changes within the myofilament that culminate in force production. Hypertrophic cardiomyopathy (HCM)-associated TNNC1 variants generally induce a greater degree and duration of Ca2+ binding, which may underly the hypertrophic phenotype. Regulation of contraction has long been thought to occur exclusively through Ca2+ binding to site II of cTnC. However, work by several groups including ours suggest that Mg2+ , which is several orders of magnitude more abundant in the cell than Ca2+ , may compete for binding to the same cTnC regulatory site. We previously used isothermal titration calorimetry (ITC) to demonstrate that physiological concentrations of Mg2+ may decrease site II Ca2+ -binding in both N-terminal and full-length cTnC. Here, we explore the binding of Ca2+ and Mg2+ to cTnC harbouring a series of TNNC1 variants thought to be causal in HCM. ITC and thermodynamic integration (TI) simulations show that A8V, L29Q and A31S elevate the affinity for both Ca2+ and Mg2+ . Further, L48Q, Q50R and C84Y that are adjacent to the EF hand binding motif of site II have a more significant effect on affinity and the thermodynamics of the binding interaction. To the best of our knowledge, this work is the first to explore the role of Mg2+ in modifying the Ca2+ affinity of cTnC mutations linked to HCM. Our results indicate a physiologically significant role for cellular Mg2+ both at baseline and when elevated on modifying the Ca2+ binding properties of cTnC and the subsequent conformational changes which precede cardiac contraction.
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Affiliation(s)
- Kaveh Rayani
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
| | - Eric R Hantz
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - Omid Haji-Ghassemi
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - Alison Y Li
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
| | - Anne M Spuches
- Department of Chemistry, 300 Science and Technology, East Carolina University, Greenville, NC, USA
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - R John Solaro
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
- BC Children's Hospital Research Institute, Vancouver, Canada
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3
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Hassoun R, Budde H, Mügge A, Hamdani N. Cardiomyocyte Dysfunction in Inherited Cardiomyopathies. Int J Mol Sci 2021; 22:11154. [PMID: 34681814 PMCID: PMC8541428 DOI: 10.3390/ijms222011154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/10/2023] Open
Abstract
Inherited cardiomyopathies form a heterogenous group of disorders that affect the structure and function of the heart. Defects in the genes encoding sarcomeric proteins are associated with various perturbations that induce contractile dysfunction and promote disease development. In this review we aimed to outline the functional consequences of the major inherited cardiomyopathies in terms of myocardial contraction and kinetics, and to highlight the structural and functional alterations in some sarcomeric variants that have been demonstrated to be involved in the pathogenesis of the inherited cardiomyopathies. A particular focus was made on mutation-induced alterations in cardiomyocyte mechanics. Since no disease-specific treatments for familial cardiomyopathies exist, several novel agents have been developed to modulate sarcomere contractility. Understanding the molecular basis of the disease opens new avenues for the development of new therapies. Furthermore, the earlier the awareness of the genetic defect, the better the clinical prognostication would be for patients and the better the prevention of development of the disease.
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Affiliation(s)
- Roua Hassoun
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Heidi Budde
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Andreas Mügge
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nazha Hamdani
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
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Genchev GZ, Kobayashi M, Kobayashi T, Lu H. Molecular dynamics provides new insights into the mechanism of calcium signal transduction and interdomain interactions in cardiac troponin. FEBS Open Bio 2021; 11:1841-1853. [PMID: 33085832 PMCID: PMC8255835 DOI: 10.1002/2211-5463.13009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 10/05/2020] [Accepted: 10/17/2020] [Indexed: 12/16/2022] Open
Abstract
Understanding the regulation of cardiac muscle contraction at a molecular level is crucial for the development of therapeutics for heart conditions. Despite the availability of atomic structures of the protein components of cardiac muscle thin filaments, detailed insights into their dynamics and response to calcium are yet to be fully depicted. In this study, we used molecular dynamics simulations of the core domains of the cardiac muscle protein troponin to characterize the equilibrium dynamics of its calcium-bound and calcium-free forms, with a focus on elements of cardiac muscle contraction activation and deactivation, that is, calcium binding to the cardiac troponin Ca2+ -binding subunit (TnC) and the release of the switch region of the troponin inhibitory subunit (TnI) from TnC. The process of calcium binding to the TnC binding site is described as a three-step process commencing with calcium capture by the binding site residues, followed by cooperative residue interplay bringing the calcium ion to the binding site, and finally, calcium-water exchange. Furthermore, we uncovered a set of TnC-TnI interdomain interactions that are critical for TnC N-lobe hydrophobic pocket dynamics. Absence of these interactions allows the closure of the TnC N-lobe hydrophobic pocket while the TnI switch region remains expelled, whereas if the interactions are maintained, the hydrophobic pocket remains open. Modification of these interactions may fine-tune the ability of the TnC N-lobe hydrophobic pocket to close or remain open, modulate cardiac contractility and present potential therapy-relevant targets.
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Affiliation(s)
- Georgi Z Genchev
- Center for Biomedical Informatics, Shanghai Children's Hospital, Shanghai, China.,SJTU-Yale Joint Center for Biostatistics, Shanghai Jiao Tong University, Shanghai, China.,Bulgarian Institute for Genomics and Precision Medicine, Sofia, Bulgaria.,Bioinformatics Program, Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Minae Kobayashi
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
| | - Tomoyoshi Kobayashi
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
| | - Hui Lu
- Center for Biomedical Informatics, Shanghai Children's Hospital, Shanghai, China.,SJTU-Yale Joint Center for Biostatistics, Shanghai Jiao Tong University, Shanghai, China.,Department of Bioinformatics and Biostatistics, Shanghai Jiao Tong University, Shanghai, China
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5
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Chen Y, Liu W, Ma J, Wang Y, Huang H. Comprehensive physiological and transcriptomic analysis revealing the responses of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) to the replacement of fish meal with soy protein concentrate. FISH PHYSIOLOGY AND BIOCHEMISTRY 2020; 46:2037-2053. [PMID: 32767005 DOI: 10.1007/s10695-020-00851-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
Plant proteins are suitable and alternative to fish meals (FMs), with less cost compared with that of all other types of fish feeds. In recent years, soy protein concentrate (SPC) has emerged as a cost-effective alternative to FM; however, little is known regarding the effects of dietary SPC on general fish physiology and well-being. This study aimed to perform comprehensive physiological and transcriptomic analysis for testing the applicability of SPC as fish feeds in hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) [SPC replaced 0% (CK), 30% (SPC30), and 75% (SPC75) of FM protein]. Generally, SPC30 promoted fish survival and had less effects on the phenotype, while SPC75 reduced fish survival, promoted inflammation, and regulated multiple physiological responses. Thousands of differentially expressed genes (DEGs) by SPC were identified in the intestine, liver, and muscle, which were enriched in biological regulation, cellular process, metabolic process, single-organism process, cell, cell part, membrane, binding, and catalytic activity based on RNA-seq. Notably, some DEGs involved in amino acid and lipid metabolism in the digestive system highlighted the modulatory effect of SPC on these metabolic processes, consistent with the physiological responses including enzyme activities. The enriched aspects of these predominant DEGs might be directly related to the different effects of SPC30 and SPC75 on fish growth, digestibility, and underlying enzyme activities and histology. In conclusion, the comprehensive physiological and transcriptomic comparative analysis of CK, SPC30, and SPC75 was also effective in testing the applicability of SPC as fish feeds and in designing a proper diet with the best impact on the growth performance and health of fish in hybrid grouper.
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Affiliation(s)
- Yan Chen
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, Hainan province, People's Republic of China
- College of Fisheries and Life Science, Hainan Tropical Ocean University, Sanya, 572022, Hainan Province, People's Republic of China
| | - Wenkan Liu
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, Hainan province, People's Republic of China
- College of Fisheries and Life Science, Hainan Tropical Ocean University, Sanya, 572022, Hainan Province, People's Republic of China
| | - Jun Ma
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, Hainan province, People's Republic of China.
- College of Fisheries and Life Science, Hainan Tropical Ocean University, Sanya, 572022, Hainan Province, People's Republic of China.
| | - Yaorong Wang
- Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, Guangdong Province, People's Republic of China
| | - Hai Huang
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, Hainan province, People's Republic of China
- College of Fisheries and Life Science, Hainan Tropical Ocean University, Sanya, 572022, Hainan Province, People's Republic of China
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Validation of Real-time PCR Reference Genes of Muscle Metabolism in Harvested Spiny-Cheek Crayfish ( Faxonius limosus) Exposed to Seasonal Variation. Animals (Basel) 2020; 10:ani10071140. [PMID: 32640616 PMCID: PMC7401605 DOI: 10.3390/ani10071140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/03/2020] [Accepted: 07/04/2020] [Indexed: 01/23/2023] Open
Abstract
Real-time quantitative reverse transcription PCR (RT-qPCR) is a sensitive and broadly used technique of assessing gene activity. To obtain a reliable result, stably expressed reference genes are essential for normalization of transcripts in various samples. To our knowledge, this is the first systematic analysis of reference genes for normalization of RT-qPCR data in spiny-cheek crayfish (Faxonius limosus). In this study, expression of five candidate reference genes (actb, β-actin; gapdh, glyceraldehyde-3-phosphate dehydrogenase; eif, eukaryotic translation initiation factor 5a; ef-1α, elongation factor-1α; and tub, α-tubulin) in muscle samples from male and female F. limosus in spring and autumn was analyzed. Additionally, the most stable reference genes were used for accurate normalization of five target genes, i.e., tnnc, troponin c; ak, arginine kinase; fr, ferritin; ccbp-23, crustacean calcium-binding protein 23; and actinsk8, skeletal muscle actin 8. Results obtained using the geNorm and NormFinder algorithms showed high consistency, and differences in the activity of the selected actb with eif genes were successfully identified. The spring and autumn activities of the target genes (except ak) in the muscle tissue of males and females differed significantly, showing that both sexes are immensely involved in an array of breeding behaviors in spring, and females intensively recover in the autumn season. Characterization of first reference genes in spiny-cheek crayfish will facilitate more accurate and reliable expression studies in this key species.
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Abstract
Ca2+ binding proteins (CBP) are of key importance for calcium to play its role as a pivotal second messenger. CBP bind Ca2+ in specific domains, contributing to the regulation of its concentration at the cytosol and intracellular stores. They also participate in numerous cellular functions by acting as Ca2+ transporters across cell membranes or as Ca2+-modulated sensors, i.e. decoding Ca2+ signals. Since CBP are integral to normal physiological processes, possible roles for them in a variety of diseases has attracted growing interest in recent years. In addition, research on CBP has been reinforced with advances in the structural characterization of new CBP family members. In this chapter we have updated a previous review on CBP, covering in more depth potential participation in physiopathological processes and candidacy for pharmacological targets in many diseases. We review intracellular CBP that contain the structural EF-hand domain: parvalbumin, calmodulin, S100 proteins, calcineurin and neuronal Ca2+ sensor proteins (NCS). We also address intracellular CBP lacking the EF-hand domain: annexins, CBP within intracellular Ca2+ stores (paying special attention to calreticulin and calsequestrin), proteins that contain a C2 domain (such as protein kinase C (PKC) or synaptotagmin) and other proteins of interest, such as regucalcin or proprotein convertase subtisilin kexins (PCSK). Finally, we summarise the latest findings on extracellular CBP, classified according to their Ca2+ binding structures: (i) EF-hand domains; (ii) EGF-like domains; (iii) ɣ-carboxyl glutamic acid (GLA)-rich domains; (iv) cadherin domains; (v) Ca2+-dependent (C)-type lectin-like domains; (vi) Ca2+-binding pockets of family C G-protein-coupled receptors.
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Invertebrate troponin: Insights into the evolution and regulation of striated muscle contraction. Arch Biochem Biophys 2019; 666:40-45. [PMID: 30928296 DOI: 10.1016/j.abb.2019.03.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/13/2019] [Accepted: 03/25/2019] [Indexed: 12/15/2022]
Abstract
The troponin complex plays a central role in regulating the contraction and relaxation of striated muscles. Among the three protein subunits of troponin, the calcium receptor subunit, TnC, belongs to the calmodulin family of calcium signaling proteins whereas the inhibitory subunit, TnI, and tropomyosin-binding/thin filament-anchoring subunit, TnT, are striated muscle-specific regulatory proteins. TnI and TnT emerged early in bilateral symmetric invertebrate animals and have co-evolved during the 500-700 million years of muscle evolution. To understand the divergence as well as conservation of the structures of TnI and TnT in invertebrate and vertebrate organisms adds novel insights into the structure-function relationship of troponin and the muscle type isoforms of TnI and TnT. Based on the significant growth of genomic database of multiple species in the past decade, this focused review studied the primary structure features of invertebrate troponin subunits in comparisons with the vertebrate counterparts. The evolutionary data demonstrate valuable information for a better understanding of the thin filament regulation of striated muscle contractility in health and diseases.
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Potluri PR, Cordina NM, Kachooei E, Brown LJ. Characterization of the L29Q Hypertrophic Cardiomyopathy Mutation in Cardiac Troponin C by Paramagnetic Relaxation Enhancement Nuclear Magnetic Resonance. Biochemistry 2019; 58:908-917. [PMID: 30620548 DOI: 10.1021/acs.biochem.8b01140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The key events in regulating muscle contraction involve the troponin (Tn) heterotrimeric protein complex in which the binding to and release of Ca2+ from the highly conserved troponin C (TnC) subunit trigger a series of structural changes within Tn, and the other thin filament proteins, to result in contraction. In the heart, the control of contraction and relaxation events can be altered by many single-point mutations that may result in cardiomyopathy and sometimes sudden cardiac death. Here we have examined the structural effects of one hypertrophic cardiomyopathy mutation, L29Q, on Ca2+-induced structural transitions within whole TnC. This mutation is of particular interest as several physiological and structural studies have indicated that the response of TnC to Ca2+ binding is altered in the presence of the L29Q mutation, but the structural nature of these changes continues to be debated. In addition, little is known about the effect of this mutation in the Ca2+ free state. Here we have used paramagnetic relaxation enhancement nuclear magnetic resonance (PRE-NMR) to assess the structural effects arising from the L29Q mutation. PRE-NMR distances obtained from a nitroxide spin-label at Cys84 showed that the L29Q mutation perturbs the structure of the TnC N-domain in the presence and absence of Ca2+, with a more "open" TnC N-domain observed in the apo form. In addition, binding of Ca2+ to the TnC-L29Q construct triggers a change in the orientation between the two domains of TnC. Together, these structural perturbations, revealed by PRE-NMR, provide insight into the pathogenesis of this mutation.
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Affiliation(s)
- Phani R Potluri
- Department of Molecular Sciences , Macquarie University , Sydney , NSW 2109 , Australia
| | - Nicole M Cordina
- Department of Molecular Sciences , Macquarie University , Sydney , NSW 2109 , Australia
| | - Ehsan Kachooei
- Department of Molecular Sciences , Macquarie University , Sydney , NSW 2109 , Australia
| | - Louise J Brown
- Department of Molecular Sciences , Macquarie University , Sydney , NSW 2109 , Australia
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Marques MA, Parvatiyar MS, Yang W, de Oliveira GAP, Pinto JR. The missing links within troponin. Arch Biochem Biophys 2018; 663:95-100. [PMID: 30584890 DOI: 10.1016/j.abb.2018.12.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/18/2018] [Accepted: 12/21/2018] [Indexed: 01/02/2023]
Abstract
The cardiac contraction-relaxation cycle is controlled by a sophisticated set of machinery. Of particular interest, is the revelation that allosteric networks transmit effects of binding at one site to influence troponin complex dynamics and structural-mediated signaling in often distal, functional sites in the myofilament. Our recent observations provide compelling evidence that allostery can explain the function of large-scale macromolecular events. Here we elaborate on our recent findings of interdomain communication within troponin C, using cutting-edge structural biology approaches, and highlight the importance of unveiling the unknown, distant communication networks within this system to obtain more comprehensive knowledge of how allostery impacts cardiac physiology and disease.
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Affiliation(s)
- Mayra A Marques
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Michelle S Parvatiyar
- Department of Nutrition, Food and Exercise Sciences, Florida State University, 107 Chieftan Way, Tallahassee, FL, 32306-1493, USA
| | - Wei Yang
- Department of Chemistry and Biochemistry and Institute of Molecular Biophysics, Florida State University, Kasha Laboratory Building, 91 Chieftan Way, Tallahassee, FL, 32306-4380, USA
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, 22908-0733, USA.
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, 1115 West Call Street, Tallahassee, FL, 32306-4300, USA.
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Stevens CM, Rayani K, Singh G, Lotfalisalmasi B, Tieleman DP, Tibbits GF. Changes in the dynamics of the cardiac troponin C molecule explain the effects of Ca 2+-sensitizing mutations. J Biol Chem 2017; 292:11915-11926. [PMID: 28533433 DOI: 10.1074/jbc.m116.770776] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/07/2017] [Indexed: 12/31/2022] Open
Abstract
Cardiac troponin C (cTnC) is the regulatory protein that initiates cardiac contraction in response to Ca2+ TnC binding Ca2+ initiates a cascade of protein-protein interactions that begins with the opening of the N-terminal domain of cTnC, followed by cTnC binding the troponin I switch peptide (TnISW). We have evaluated, through isothermal titration calorimetry and molecular-dynamics simulation, the effect of several clinically relevant mutations (A8V, L29Q, A31S, L48Q, Q50R, and C84Y) on the Ca2+ affinity, structural dynamics, and calculated interaction strengths between cTnC and each of Ca2+ and TnISW Surprisingly the Ca2+ affinity measured by isothermal titration calorimetry was only significantly affected by half of these mutations including L48Q, which had a 10-fold higher affinity than WT, and the Q50R and C84Y mutants, each of which had affinities 3-fold higher than wild type. This suggests that Ca2+ affinity of the N-terminal domain of cTnC in isolation is insufficient to explain the pathogenicity of these mutations. Molecular-dynamics simulation was used to evaluate the effects of these mutations on Ca2+ binding, structural dynamics, and TnI interaction independently. Many of the mutations had a pronounced effect on the balance between the open and closed conformations of the TnC molecule, which provides an indirect mechanism for their pathogenic properties. Our data demonstrate that the structural dynamics of the cTnC molecule are key in determining myofilament Ca2+ sensitivity. Our data further suggest that modulation of the structural dynamics is the underlying molecular mechanism for many disease mutations that are far from the regulatory Ca2+-binding site of cTnC.
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Affiliation(s)
- Charles M Stevens
- Cardiovascular Sciences, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia V5Z 4H4, Canada; Departments of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Kaveh Rayani
- Departments of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Gurpreet Singh
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Bairam Lotfalisalmasi
- Departments of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Glen F Tibbits
- Cardiovascular Sciences, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia V5Z 4H4, Canada; Departments of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada; Departments of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
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12
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Crossley DA, Burggren WW, Reiber CL, Altimiras J, Rodnick KJ. Mass Transport: Circulatory System with Emphasis on Nonendothermic Species. Compr Physiol 2016; 7:17-66. [PMID: 28134997 DOI: 10.1002/cphy.c150010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mass transport can be generally defined as movement of material matter. The circulatory system then is a biological example given its role in the movement in transporting gases, nutrients, wastes, and chemical signals. Comparative physiology has a long history of providing new insights and advancing our understanding of circulatory mass transport across a wide array of circulatory systems. Here we focus on circulatory function of nonmodel species. Invertebrates possess diverse convection systems; that at the most complex generate pressures and perform at a level comparable to vertebrates. Many invertebrates actively modulate cardiovascular function using neuronal, neurohormonal, and skeletal muscle activity. In vertebrates, our understanding of cardiac morphology, cardiomyocyte function, and contractile protein regulation by Ca2+ highlights a high degree of conservation, but differences between species exist and are coupled to variable environments and body temperatures. Key regulators of vertebrate cardiac function and systemic blood pressure include the autonomic nervous system, hormones, and ventricular filling. Further chemical factors regulating cardiovascular function include adenosine, natriuretic peptides, arginine vasotocin, endothelin 1, bradykinin, histamine, nitric oxide, and hydrogen sulfide, to name but a few. Diverse vascular morphologies and the regulation of blood flow in the coronary and cerebral circulations are also apparent in nonmammalian species. Dynamic adjustments of cardiovascular function are associated with exercise on land, flying at high altitude, prolonged dives by marine mammals, and unique morphology, such as the giraffe. Future studies should address limits of gas exchange and convective transport, the evolution of high arterial pressure across diverse taxa, and the importance of the cardiovascular system adaptations to extreme environments. © 2017 American Physiological Society. Compr Physiol 7:17-66, 2017.
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Affiliation(s)
- Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Warren W Burggren
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Carl L Reiber
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Jordi Altimiras
- AVIAN Behavioral Genomics and Physiology, IFM Biology, Linköping University, Linköping, Sweden
| | - Kenneth J Rodnick
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho, USA
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Marques MDA, de Oliveira GAP. Cardiac Troponin and Tropomyosin: Structural and Cellular Perspectives to Unveil the Hypertrophic Cardiomyopathy Phenotype. Front Physiol 2016; 7:429. [PMID: 27721798 PMCID: PMC5033975 DOI: 10.3389/fphys.2016.00429] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/09/2016] [Indexed: 12/12/2022] Open
Abstract
Inherited myopathies affect both skeletal and cardiac muscle and are commonly associated with genetic dysfunctions, leading to the production of anomalous proteins. In cardiomyopathies, mutations frequently occur in sarcomeric genes, but the cause-effect scenario between genetic alterations and pathological processes remains elusive. Hypertrophic cardiomyopathy (HCM) was the first cardiac disease associated with a genetic background. Since the discovery of the first mutation in the β-myosin heavy chain, more than 1400 new mutations in 11 sarcomeric genes have been reported, awarding HCM the title of the “disease of the sarcomere.” The most common macroscopic phenotypes are left ventricle and interventricular septal thickening, but because the clinical profile of this disease is quite heterogeneous, these phenotypes are not suitable for an accurate diagnosis. The development of genomic approaches for clinical investigation allows for diagnostic progress and understanding at the molecular level. Meanwhile, the lack of accurate in vivo models to better comprehend the cellular events triggered by this pathology has become a challenge. Notwithstanding, the imbalance of Ca2+ concentrations, altered signaling pathways, induction of apoptotic factors, and heart remodeling leading to abnormal anatomy have already been reported. Of note, a misbalance of signaling biomolecules, such as kinases and tumor suppressors (e.g., Akt and p53), seems to participate in apoptotic and fibrotic events. In HCM, structural and cellular information about defective sarcomeric proteins and their altered interactome is emerging but still represents a bottleneck for developing new concepts in basic research and for future therapeutic interventions. This review focuses on the structural and cellular alterations triggered by HCM-causing mutations in troponin and tropomyosin proteins and how structural biology can aid in the discovery of new platforms for therapeutics. We highlight the importance of a better understanding of allosteric communications within these thin-filament proteins to decipher the HCM pathological state.
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Affiliation(s)
- Mayra de A Marques
- Programa de Biologia Estrutural, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
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Sears EJ, Gillis TE. A functional comparison of cardiac troponin C from representatives of three vertebrate taxa: Linking phylogeny and protein function. Comp Biochem Physiol B Biochem Mol Biol 2016; 202:8-15. [PMID: 27453566 DOI: 10.1016/j.cbpb.2016.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 07/18/2016] [Accepted: 07/19/2016] [Indexed: 11/25/2022]
Abstract
The Ca2+ affinity of cardiac troponin C (cTnC) from rainbow trout is significantly greater than that of cTnC from mammalian species. This high affinity is thought to enable cardiac function in trout at low physiological temperatures and is due to residues Asn2, Ile28, Gln29, and Asp30 (Gillis et al., 2005, Physiol Genomics, 22, 1-7). Interestingly, the cTnC of the African clawed frog Xenopus laevis (frog cTnC) contains Gln29 and Asp30 but the residues at positions 2 and 28 are those found in all mammalian cTnC isoforms (Asp2 and Val28). The purpose of this study was to determine the Ca2+ affinity of frog cTnC, and to determine how these three protein orthologs influence the function of complete troponin complexes. Measurements of Ca2+ affinity and the rate of Ca2+ dissociation from the cTnC isoforms and cTn complexes were made by monitoring the fluorescence of anilinonapthalenesulfote iodoacetamide (IAANS) engineered into the cTnC isoforms to report changes in protein conformation. The results demonstrate that the Ca2+ affinity of frog cTnC is greater than that of trout cTnC and human cTnC. We also found that replacing human cTnC with frog cTnC in a mammalian cTn complex increased the Ca2+ affinity of the complex by 5-fold, which is also greater than complexes containing trout cTnC. Together these results suggest that frog cTnC has the potential to increase the Ca2+ sensitivity of force generation by the mammalian heart.
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Affiliation(s)
- Elizabeth J Sears
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada; Cardiovasclar Research Center, University of Guelph, Canada
| | - Todd E Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada; Cardiovasclar Research Center, University of Guelph, Canada.
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15
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Genge CE, Stevens CM, Davidson WS, Singh G, Peter Tieleman D, Tibbits GF. Functional Divergence in Teleost Cardiac Troponin Paralogs Guides Variation in the Interaction of TnI Switch Region with TnC. Genome Biol Evol 2016; 8:994-1011. [PMID: 26979795 PMCID: PMC4860682 DOI: 10.1093/gbe/evw044] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Gene duplication results in extra copies of genes that must coevolve with their interacting partners in multimeric protein complexes. The cardiac troponin (Tn) complex, containing TnC, TnI, and TnT, forms a distinct functional unit critical for the regulation of cardiac muscle contraction. In teleost fish, the function of the Tn complex is modified by the consequences of differential expression of paralogs in response to environmental thermal challenges. In this article, we focus on the interaction between TnI and TnC, coded for by genes that have independent evolutionary origins, but the co-operation of their protein products has necessitated coevolution. In this study, we characterize functional divergence of TnC and TnI paralogs, specifically the interrelated roles of regulatory subfunctionalization and structural subfunctionalization. We determined that differential paralog transcript expression in response to temperature acclimation results in three combinations of TnC and TnI in the zebrafish heart: TnC1a/TnI1.1, TnC1b/TnI1.1, and TnC1a/TnI1.5. Phylogenetic analysis of these highly conserved proteins identified functionally divergent residues in TnI and TnC. The structural and functional effect of these Tn combinations was modeled with molecular dynamics simulation to link divergent sites to changes in interaction strength. Functional divergence in TnI and TnC were not limited to the residues involved with TnC/TnI switch interaction, which emphasizes the complex nature of Tn function. Patterns in domain-specific divergent selection and interaction energies suggest that substitutions in the TnI switch region are crucial to modifying TnI/TnC function to maintain cardiac contraction with temperature changes. This integrative approach introduces Tn as a model of functional divergence that guides the coevolution of interacting proteins.
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Affiliation(s)
- Christine E Genge
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Charles M Stevens
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada Cardiovascular Sciences, Child and Family Research Institute, Vancouver, British Columbia, Canada
| | - William S Davidson
- Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Gurpreet Singh
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Alberta, Canada
| | - D Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Alberta, Canada
| | - Glen F Tibbits
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada Cardiovascular Sciences, Child and Family Research Institute, Vancouver, British Columbia, Canada Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
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16
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Genge CE, Lin E, Lee L, Sheng X, Rayani K, Gunawan M, Stevens CM, Li AY, Talab SS, Claydon TW, Hove-Madsen L, Tibbits GF. The Zebrafish Heart as a Model of Mammalian Cardiac Function. Rev Physiol Biochem Pharmacol 2016; 171:99-136. [PMID: 27538987 DOI: 10.1007/112_2016_5] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Zebrafish (Danio rerio) are widely used as vertebrate model in developmental genetics and functional genomics as well as in cardiac structure-function studies. The zebrafish heart has been increasingly used as a model of human cardiac function, in part, due to the similarities in heart rate and action potential duration and morphology with respect to humans. The teleostian zebrafish is in many ways a compelling model of human cardiac function due to the clarity afforded by its ease of genetic manipulation, the wealth of developmental biological information, and inherent suitability to a variety of experimental techniques. However, in addition to the numerous advantages of the zebrafish system are also caveats related to gene duplication (resulting in paralogs not present in human or other mammals) and fundamental differences in how zebrafish hearts function. In this review, we discuss the use of zebrafish as a cardiac function model through the use of techniques such as echocardiography, optical mapping, electrocardiography, molecular investigations of excitation-contraction coupling, and their physiological implications relative to that of the human heart. While some of these techniques (e.g., echocardiography) are particularly challenging in the zebrafish because of diminutive size of the heart (~1.5 mm in diameter) critical information can be derived from these approaches and are discussed in detail in this article.
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Affiliation(s)
- Christine E Genge
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Eric Lin
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Ling Lee
- BC Children's Hospital Research Institute, Vancouver, BC, Canada, V5Z 4H4
| | - XiaoYe Sheng
- BC Children's Hospital Research Institute, Vancouver, BC, Canada, V5Z 4H4
| | - Kaveh Rayani
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Marvin Gunawan
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Charles M Stevens
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6.,BC Children's Hospital Research Institute, Vancouver, BC, Canada, V5Z 4H4
| | - Alison Yueh Li
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Sanam Shafaat Talab
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Thomas W Claydon
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Leif Hove-Madsen
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6.,Cardiovascular Research Centre CSIC-ICCC, Hospital de Sant Pau, Barcelona, Spain
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6. .,BC Children's Hospital Research Institute, Vancouver, BC, Canada, V5Z 4H4.
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17
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Li MX, Hwang PM. Structure and function of cardiac troponin C (TNNC1): Implications for heart failure, cardiomyopathies, and troponin modulating drugs. Gene 2015; 571:153-66. [PMID: 26232335 DOI: 10.1016/j.gene.2015.07.074] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/24/2015] [Accepted: 07/21/2015] [Indexed: 10/23/2022]
Abstract
In striated muscle, the protein troponin complex turns contraction on and off in a calcium-dependent manner. The calcium-sensing component of the complex is troponin C, which is expressed from the TNNC1 gene in both cardiac muscle and slow-twitch skeletal muscle (identical transcript in both tissues) and the TNNC2 gene in fast-twitch skeletal muscle. Cardiac troponin C (cTnC) is made up of two globular EF-hand domains connected by a flexible linker. The structural C-domain (cCTnC) contains two high affinity calcium-binding sites that are always occupied by Ca(2+) or Mg(2+) under physiologic conditions, stabilizing an open conformation that remains anchored to the rest of the troponin complex. In contrast, the regulatory N-domain (cNTnC) contains a single low affinity site that is largely unoccupied at resting calcium concentrations. During muscle activation, calcium binding to cNTnC favors an open conformation that binds to the switch region of troponin I, removing adjacent inhibitory regions of troponin I from actin and allowing muscle contraction to proceed. Regulation of the calcium binding affinity of cNTnC is physiologically important, because it directly impacts the calcium sensitivity of muscle contraction. Calcium sensitivity can be modified by drugs that stabilize the open form of cNTnC, post-translational modifications like phosphorylation of troponin I, or downstream thin filament protein interactions that impact the availability of the troponin I switch region. Recently, mutations in cTnC have been associated with hypertrophic or dilated cardiomyopathy. A detailed understanding of how calcium sensitivity is regulated through the troponin complex is necessary for explaining how mutations perturb its function to promote cardiomyopathy and how post-translational modifications in the thin filament affect heart function and heart failure. Troponin modulating drugs are being developed for the treatment of cardiomyopathies and heart failure.
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Affiliation(s)
- Monica X Li
- Department of Medicine, University of Alberta, Edmonton, AB T6G 2G3, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Peter M Hwang
- Department of Medicine, University of Alberta, Edmonton, AB T6G 2G3, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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18
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He L, Pei Y, Jiang Y, Li Y, Liao L, Zhu Z, Wang Y. Global gene expression patterns of grass carp following compensatory growth. BMC Genomics 2015; 16:184. [PMID: 25887225 PMCID: PMC4374334 DOI: 10.1186/s12864-015-1427-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 03/02/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Compensatory growth is accelerated compared with normal growth and occurs when growth-limiting conditions are overcome. Most animals, especially fish, are capable of compensatory growth, but the mechanisms remain unclear. Further investigation of the mechanism of compensatory growth in fish is needed to improve feeding efficiency, reduce cost, and explore growth-related genes. RESULTS In the study, grass carp, an important farmed fish in China, were subjected to a compensatory growth experiment followed by transcriptome analysis by RNA-sequencing. Samples of fish from starved and re-feeding conditions were compared with the control. Under starved conditions, 4061 and 1988 differentially expressed genes (DEGs) were detected in muscle and liver tissue when compared the experimental group with control group, respectively. After re-feeding, 349 and 247 DEGs were identified in muscle and liver when the two groups were compared. Moreover, when samples from experimental group in starved and re-feeding conditions were compared, 4903 and 2444 DEGs were found in muscle and liver. Most of these DEGs were involved in metabolic processes, or encoded enzymes or proteins with catalytic activity or binding functions, or involved in metabolic and biosynthetic pathways. A number of the more significant DEGs were subjected to further analysis. Under fasting conditions, many up-regulated genes were associated with protein ubiquitination or degradation, whereas many down-regulated genes were involved in the metabolism of glucose and fatty acids. Under re-feeding conditions, genes participating in muscle synthesis and fatty acid metabolism were up-regulated significantly, and genes related to protein ubiquitination or degradation were down-regulated. Moreover, Several DEGs were random selected for confirmation by real-time quantitative PCR. CONCLUSIONS Global gene expression patterns of grass carp during compensatory growth were determined. To our knowledge, this is a first reported for a teleost fish. The results will enhance our understanding of the mechanism of compensatory growth in teleost fish.
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Affiliation(s)
- Libo He
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
| | - Yongyan Pei
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yao Jiang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yongming Li
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
| | - Lanjie Liao
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
| | - Zuoyan Zhu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
| | - Yaping Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
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19
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Tøndel K, Land S, Niederer SA, Smith NP. Quantifying inter-species differences in contractile function through biophysical modelling. J Physiol 2015; 593:1083-111. [PMID: 25480801 DOI: 10.1113/jphysiol.2014.279232] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 11/28/2014] [Indexed: 11/08/2022] Open
Abstract
Animal models and measurements are frequently used to guide and evaluate clinical interventions. In this context, knowledge of inter-species differences in physiology is crucial for understanding the limitations and relevance of animal experimental assays for informing clinical applications. Extensive effort has been put into studying the structure and function of cardiac contractile proteins and how differences in these translate into the functional properties of muscles. However, integrating this knowledge into a quantitative description, formalising and highlighting inter-species differences both in the kinetics and in the regulation of physiological mechanisms, remains challenging. In this study we propose and apply a novel approach for the quantification of inter-species differences between mouse, rat and human. Assuming conservation of the fundamental physiological mechanisms underpinning contraction, biophysically based computational models are fitted to simulate experimentally recorded phenotypes from multiple species. The phenotypic differences between species are then succinctly quantified as differences in the biophysical model parameter values. This provides the potential of quantitatively establishing the human relevance of both animal-based experimental and computational models for application in a clinical context. Our results indicate that the parameters related to the sensitivity and cooperativity of calcium binding to troponin C and the activation and relaxation rates of tropomyosin/crossbridge binding kinetics differ most significantly between mouse, rat and human, while for example the reference tension, as expected, shows only minor differences between the species. Hence, while confirming expected inter-species differences in calcium sensitivity due to large differences in the observed calcium transients, our results also indicate more unexpected differences in the cooperativity mechanism. Specifically, the decrease in the unbinding rate of calcium to troponin C with increasing active tension was much lower for mouse than for rat and human. Our results also predicted crossbridge binding to be slowest in human and fastest in mouse.
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Affiliation(s)
- Kristin Tøndel
- Department of Biomedical Engineering, King's College London, St. Thomas' Hospital, Westminster Bridge Road, London, SE1 7EH, UK; Simula Research Laboratory, Martin Linges v. 17/25, Rolfsbukta 4B, Fornebu, 1364, Norway
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20
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Li AY, Stevens CM, Liang B, Rayani K, Little S, Davis J, Tibbits GF. Familial hypertrophic cardiomyopathy related cardiac troponin C L29Q mutation alters length-dependent activation and functional effects of phosphomimetic troponin I*. PLoS One 2013; 8:e79363. [PMID: 24260207 PMCID: PMC3832503 DOI: 10.1371/journal.pone.0079363] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 09/27/2013] [Indexed: 11/18/2022] Open
Abstract
The Ca(2+) binding properties of the FHC-associated cardiac troponin C (cTnC) mutation L29Q were examined in isolated cTnC, troponin complexes, reconstituted thin filament preparations, and skinned cardiomyocytes. While higher Ca(2+) binding affinity was apparent for the L29Q mutant in isolated cTnC, this phenomenon was not observed in the cTn complex. At the level of the thin filament in the presence of phosphomimetic TnI, L29Q cTnC further reduced the Ca(2+) affinity by 27% in the steady-state measurement and increased the Ca(2+) dissociation rate by 20% in the kinetic studies. Molecular dynamics simulations suggest that L29Q destabilizes the conformation of cNTnC in the presence of phosphomimetic cTnI and potentially modulates the Ca(2+) sensitivity due to the changes of the opening/closing equilibrium of cNTnC. In the skinned cardiomyocyte preparation, L29Q cTnC increased Ca(2+) sensitivity in a highly sarcomere length (SL)-dependent manner. The well-established reduction of Ca(2+) sensitivity by phosphomimetic cTnI was diminished by 68% in the presence of the mutation and it also depressed the SL-dependent increase in myofilament Ca(2+) sensitivity. This might result from its modified interaction with cTnI which altered the feedback effects of cross-bridges on the L29Q cTnC-cTnI-Tm complex. This study demonstrates that the L29Q mutation alters the contractility and the functional effects of the phosphomimetic cTnI in both thin filament and single skinned cardiomyocytes and importantly that this effect is highly sarcomere length dependent.
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Affiliation(s)
- Alison Y. Li
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Charles M. Stevens
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
- Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Bo Liang
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Kaveh Rayani
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sean Little
- Physiology and Cell Biology, The Ohio State University, Columbia, Ohio, United States of America
| | - Jonathan Davis
- Physiology and Cell Biology, The Ohio State University, Columbia, Ohio, United States of America
| | - Glen F. Tibbits
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
- Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Cardiovascular Sciences, Child and Family Research Institute, Vancouver, British Columbia, Canada
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21
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Genge CE, Davidson WS, Tibbits GF. Adult teleost heart expresses two distinct troponin C paralogs: cardiac TnC and a novel and teleost-specific ssTnC in a chamber- and temperature-dependent manner. Physiol Genomics 2013; 45:866-75. [PMID: 23881286 PMCID: PMC5471341 DOI: 10.1152/physiolgenomics.00074.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
The teleost-specific whole genome duplication created multiple copies of genes allowing for subfunctionalization of isoforms. In this study, we show that the teleost cardiac Ca2+-binding troponin C (TnC) is the product of two distinct genes: cardiac TnC (cTnC, TnnC1a) and a fish-specific slow skeletal TnC (ssTnC, TnnC1b). The ssTnC gene is novel to teleosts as mammals have a single gene commonly referred as cTnC but which is also expressed in slow skeletal muscle. In teleosts, the data strongly indicate that these are two TnC genes are different paralogs. Because we determined that ssTnC exists across many teleosts but not in basal ray-finned fish (e.g., bichir), we propose that these paralogs are the result of an ancestral tandem gene duplication persisting only in teleosts. Quantification of mRNA levels was used to demonstrate distinct expression localization patterns of the paralogs within the chambers of the heart. In the adult zebrafish acclimated at 28°C, ssTnC mRNA levels are twofold greater than cTnC mRNA levels in the atrium, whereas cTnC mRNA was almost exclusively expressed in the ventricle. Meanwhile, rainbow trout acclimated at 5°C showed cTnC mRNA levels in both chambers significantly greater than ssTnC. Distinct responses to temperature acclimation were also quantified in both adult zebrafish and rainbow trout, with mRNA in both chambers shifting to express higher levels of cTnC in 18°C acclimated zebrafish and 5°C acclimated trout. Possible subfunctionalization of TnC isoforms may provide insight into how teleosts achieve physiological versatility in chamber-specific contractile properties.
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Affiliation(s)
- Christine E Genge
- Molecular Cardiac Physiology Group, Simon Fraser University, Burnaby, Canada
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22
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Zhang XL, Tibbits GF, Paetzel M. The structure of cardiac troponin C regulatory domain with bound Cd2+ reveals a closed conformation and unique ion coordination. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:722-34. [PMID: 23633581 DOI: 10.1107/s0907444913001182] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 01/11/2013] [Indexed: 12/22/2022]
Abstract
The amino-terminal domain of cardiac troponin C (cNTnC) is an essential Ca(2+) sensor found in cardiomyocytes. It undergoes a conformational change upon Ca(2+) binding and transduces the signal to the rest of the troponin complex to initiate cardiac muscle contraction. Two classical EF-hand motifs (EF1 and EF2) are present in cNTnC. Under physiological conditions, only EF2 binds Ca(2+); EF1 is a vestigial site that has lost its function in binding Ca(2+) owing to amino-acid sequence changes during evolution. Proteins with EF-hand motifs are capable of binding divalent cations other than calcium. Here, the crystal structure of wild-type (WT) human cNTnC in complex with Cd(2+) is presented. The structure of Cd(2+)-bound cNTnC with the disease-related mutation L29Q, as well as a structure with the residue differences D2N, V28I, L29Q and G30D (NIQD), which have been shown to have functional importance in Ca(2+) sensing at lower temperatures in ectothermic species, have also been determined. The structures resemble the overall conformation of NMR structures of Ca(2+)-bound cNTnC, but differ significantly from a previous crystal structure of Cd(2+)-bound cNTnC in complex with deoxycholic acid. The subtle structural changes observed in the region near the mutations may play a role in the increased Ca(2+) affinity. The 1.4 Å resolution WT cNTnC structure, which is the highest resolution structure yet obtained for cardiac troponin C, reveals a Cd(2+) ion coordinated in the canonical pentagonal bipyramidal geometry in EF2 despite three residues in the loop being disordered. A Cd(2+) ion found in the vestigial ion-binding site of EF1 is coordinated in a noncanonical `distorted' octahedral geometry. A comparison of the ion coordination observed within EF-hand-containing proteins for which structures have been solved in the presence of Cd(2+) is presented. A refolded WT cNTnC structure is also presented.
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Affiliation(s)
- Xiaolu Linda Zhang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
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23
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Zimmer DB, Eubanks JO, Ramakrishnan D, Criscitiello MF. Evolution of the S100 family of calcium sensor proteins. Cell Calcium 2012; 53:170-9. [PMID: 23246155 DOI: 10.1016/j.ceca.2012.11.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 11/01/2012] [Accepted: 11/03/2012] [Indexed: 12/01/2022]
Abstract
The S100s are a large group of Ca(2+) sensors found exclusively in vertebrates. Transcriptomic and genomic data from the major radiations of mammals were used to derive the evolution of the mammalian S100s genes. In human and mouse, S100s and S100 fused-type proteins are in a separate clade from other Ca(2+) sensor proteins, indicating that an ancient bifurcation between these two gene lineages has occurred. Furthermore, the five genomic loci containing S100 genes have remained largely intact during the past 165 million years since the shared ancestor of egg-laying and placental mammals. Nonetheless, interesting births and deaths of S100 genes have occurred during mammalian evolution. The S100A7 loci exhibited the most plasticity and phylogenetic analyses clarified relationships between the S100A7 proteins encoded in the various mammalian genomes. Phylogenetic analyses also identified four conserved subgroups of S100s that predate the rise of warm-blooded vertebrates: A2/A3/A4/A5/A6, A1/A10/A11/B/P/Z, A13/A14/A16, and A7s/A8/A9/A12/G. The similarity between genomic location and phylogenetic clades suggest that these subfamilies arose by a series of tandem gene duplication events. Examination of annotated S100s in lower vertebrates suggests that the ancestral S100 was a member of the A1/A10/A11/B/P/Z subgroup and arose near the emergence of vertebrates approximately 500 million years ago.
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Affiliation(s)
- Danna B Zimmer
- Center for Biomolecular Therapeutics and Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 20102, USA.
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Whittington AC, Nienow TE, Whittington CL, Fort TJ, Grove TJ. Functional and structural characterization of a eurytolerant calsequestrin from the intertidal teleost Fundulus heteroclitus. PLoS One 2012; 7:e50801. [PMID: 23226387 PMCID: PMC3511267 DOI: 10.1371/journal.pone.0050801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 10/25/2012] [Indexed: 02/07/2023] Open
Abstract
Calsequestrins (CSQ) are high capacity, medium affinity, calcium-binding proteins present in the sarcoplasmic reticulum (SR) of cardiac and skeletal muscles. CSQ sequesters Ca2+ during muscle relaxation and increases the Ca2+-storage capacity of the SR. Mammalian CSQ has been well studied as a model of human disease, but little is known about the environmental adaptation of CSQ isoforms from poikilothermic organisms. The mummichog, Fundulus heteroclitus, is an intertidal fish that experiences significant daily and seasonal environmental fluctuations and is an interesting study system for investigations of adaptation at the protein level. We determined the full-length coding sequence of a CSQ isoform from skeletal muscle of F. heteroclitus (FCSQ) and characterized the function and structure of this CSQ. The dissociation constant (Kd) of FCSQ is relatively insensitive to changes in temperature and pH, thus indicating that FCSQ is a eurytolerant protein. We identified and characterized a highly conserved salt bridge network in FCSQ that stabilizes the formation of front-to-front dimers, a process critical to CSQ function. The functional profile of FCSQ correlates with the natural history of F. heteroclitus suggesting that the eurytolerant function of FCSQ may be adaptive.
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Affiliation(s)
- A. Carl Whittington
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States of America
| | - Tatyana E. Nienow
- Department of Biology, Valdosta State University, Valdosta, Georgia, United States of America
| | - Christi L. Whittington
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Timothy J. Fort
- Department of Biology, Valdosta State University, Valdosta, Georgia, United States of America
| | - Theresa J. Grove
- Department of Biology, Valdosta State University, Valdosta, Georgia, United States of America
- * E-mail:
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Umasuthan N, Elvitigala DAS, Saranya Revathy K, Lee Y, Whang I, Park MA, Lee J. Identification and in silico analysis of a novel troponin C like gene from Ruditapes philippinarum (Bivalvia: Veneridae) and its transcriptional response for calcium challenge. Gene 2012; 519:194-201. [PMID: 23137632 DOI: 10.1016/j.gene.2012.10.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 09/21/2012] [Accepted: 10/21/2012] [Indexed: 10/27/2022]
Abstract
Troponin C (TnC) is one of the subunits composing the troponin complex, which is primarily expressed in muscle tissue and plays a major role in regulating contractility. We have identified a novel TnC-like gene (RpTnC) from the Ruditapes philippinarum Manila clam. Sequence analysis indicated that RpTnC has a 450bp coding sequence, encoding a 150 amino acid protein with a molecular mass of 17.4 kDa. The RpTnC protein consisted of four EF-hand motifs (I-IV), each with a Ca2+-binding site. In silico comparative analysis of protein sequence showed that only site IV, demonstrating a conserved stretch (DxDxSx6E), is functionally active for Ca2+-coordination. Moreover, RpTnC was homologically (61.3% identity) and phylogenetically closest to Japanese flying squid TnC. The mRNA expression analysis using quantitative real-time PCR revealed a differential basal-expression of RpTnC transcripts in six different clam tissues, with higher levels in adductor muscle and mantle. Intramuscular administration of CaCl2 caused a prominent upregulation of RpTnC transcripts in adductor muscle (~5 fold). Collectively, our findings suggest that the TnC homolog of Manila clam identified in this study may be involved in important role(s) in clam physiology, mainly in its muscle tissues, and its transcription could be significantly influenced by increased Ca2+ levels.
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Affiliation(s)
- Navaneethaiyer Umasuthan
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Special Self-Governing Province 690-756, Republic of Korea
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Cardiomyopathy-Related Mutations in Cardiac Troponin C, L29Q and G159D, Have Divergent Effects on Rat Cardiac Myofiber Contractile Dynamics. Biochem Res Int 2012; 2012:824068. [PMID: 23008774 PMCID: PMC3447348 DOI: 10.1155/2012/824068] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 07/06/2012] [Accepted: 08/08/2012] [Indexed: 11/17/2022] Open
Abstract
Previous studies of cardiomyopathy-related mutations in cardiac troponin C (cTnC)-L29Q and G159D-have shown diverse findings. The link between such mutant effects and their divergent impact on cardiac phenotypes has remained elusive due to lack of studies on contractile dynamics. We hypothesized that a cTnC mutant-induced change in the thin filament will affect global myofilament mechanodynamics because of the interactions of thin filament kinetics with both Ca(2+) binding and crossbridge (XB) cycling kinetics. We measured pCa-tension relationship and contractile dynamics in detergent-skinned rat cardiac papillary muscle fibers reconstituted with the recombinant wild-type rat cTnC (cTnC(WT)), cTnC(L29Q), and cTnC(G159D) mutants. cTnC(L29Q) fibers demonstrated a significant decrease in Ca(2+) sensitivity, but cTnC(G159D) fibers did not. Both mutants had no effect on Ca(2+)-activated maximal tension. The rate of XB recruitment dynamics increased in cTnC(L29Q) (26%) and cTnC(G159D) (25%) fibers. The rate of XB distortion dynamics increased in cTnC(G159D) fibers (15%). Thus, the cTnC(L29Q) mutant modulates the equilibrium between the non-cycling and cycling pool of XB by affecting the on/off kinetics of the regulatory units (Tropomyosin-Troponin); whereas, the cTnC(G159D) mutant increases XB cycling rate. Different effects on contractile dynamics may offer clue regarding how cTnC(L29Q) and cTnC(G159D) cause divergent effects on cardiac phenotypes.
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Li AY, Lee J, Borek D, Otwinowski Z, Tibbits GF, Paetzel M. Crystal structure of cardiac troponin C regulatory domain in complex with cadmium and deoxycholic acid reveals novel conformation. J Mol Biol 2011; 413:699-711. [PMID: 21920370 PMCID: PMC4068330 DOI: 10.1016/j.jmb.2011.08.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 08/23/2011] [Accepted: 08/24/2011] [Indexed: 01/07/2023]
Abstract
The amino-terminal regulatory domain of cardiac troponin C (cNTnC) plays an important role as the calcium sensor for the troponin complex. Calcium binding to cNTnC results in conformational changes that trigger a cascade of events that lead to cardiac muscle contraction. The cardiac N-terminal domain of TnC consists of two EF-hand calcium binding motifs, one of which is dysfunctional in binding calcium. Nevertheless, the defunct EF-hand still maintains a role in cNTnC function. For its structural analysis by X-ray crystallography, human cNTnC with the wild-type primary sequence was crystallized under a novel crystallization condition. The crystal structure was solved by the single-wavelength anomalous dispersion method and refined to 2.2 Å resolution. The structure displays several novel features. Firstly, both EF-hand motifs coordinate cadmium ions derived from the crystallization milieu. Secondly, the ion coordination in the defunct EF-hand motif accompanies unusual changes in the protein conformation. Thirdly, deoxycholic acid, also derived from the crystallization milieu, is bound in the central hydrophobic cavity. This is reminiscent of the interactions observed for cardiac calcium sensitizer drugs that bind to the same core region and maintain the "open" conformational state of calcium-bound cNTnC. The cadmium ion coordination in the defunct EF-hand indicates that this vestigial calcium binding site retains the structural and functional elements that allow it to coordinate a cadmium ion. However, it is a result of, or concomitant with, large and unusual structural changes in cNTnC.
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Affiliation(s)
- Alison Yueh Li
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Department of Biomedical Physiology and Kinesiology, Molecular Cardiac Physiology Group, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
| | - Jaeyong Lee
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
| | - Dominika Borek
- Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Zbyszek Otwinowski
- Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Glen F. Tibbits
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Department of Biomedical Physiology and Kinesiology, Molecular Cardiac Physiology Group, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Cardiovascular Sciences, Child and Family Research Institute, 950 West 28 Ave, Vancouver, BC, Canada V5Z 4H4
| | - Mark Paetzel
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Department of Biomedical Physiology and Kinesiology, Molecular Cardiac Physiology Group, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Address correspondence to: Dr. Mark Paetzel, Simon Fraser University, Department of Molecular Biology and Biochemistry, South Science Building, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6, Tel.: 778-782-4230, Fax.: 778-782-5583,
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Huang RYC, Rempel DL, Gross ML. HD exchange and PLIMSTEX determine the affinities and order of binding of Ca2+ with troponin C. Biochemistry 2011; 50:5426-35. [PMID: 21574565 PMCID: PMC3115450 DOI: 10.1021/bi200377c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Troponin C (TnC), present in all striated muscle, is the Ca(2+)-activated trigger that initiates myocyte contraction. The binding of Ca(2+) to TnC initiates a cascade of conformational changes involving the constituent proteins of the thin filament. The functional properties of TnC and its ability to bind Ca(2+) have significant regulatory influence on the contractile reaction of muscle. Changes in TnC may also correlate with cardiac and various other muscle-related diseases. We report here the implementation of the PLIMSTEX strategy (protein ligand interaction by mass spectrometry, titration, and H/D exchange) to elucidate the binding affinity of TnC with Ca(2+) and, more importantly, to determine the order of Ca(2+) binding of the four EF hands of the protein. The four equilibrium constants, K(1) = (5 ± 5) × 10(7) M(-1), K(2) = (1.8 ± 0.8) × 10(7) M(-1), K(3) = (4.2 ± 0.9) × 10(6) M(-1), and K(4) = (1.6 ± 0.6) × 10(6) M(-1), agree well with determinations by other methods and serve to increase our confidence in the PLIMSTEX approach. We determined the order of binding to the four EF hands to be III, IV, II, and I by extracting from the H/DX results the deuterium patterns for each EF hand for each state of the protein (apo through fully Ca(2+) bound). This approach, demonstrated for the first time, may be general for determining binding orders of metal ions and other ligands to proteins.
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Affiliation(s)
- Richard Y-C. Huang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Don L. Rempel
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
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Zhang G, Chu W, Hu S, Meng T, Pan L, Zhou R, Liu Z, Zhang J. Identification and analysis of muscle-related protein isoforms expressed in the white muscle of the mandarin fish (Siniperca chuatsi). MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2011; 13:151-162. [PMID: 20354749 DOI: 10.1007/s10126-010-9275-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2009] [Accepted: 01/19/2010] [Indexed: 05/29/2023]
Abstract
To identify muscle-related protein isoforms expressed in the white muscle of the mandarin fish Siniperca chuatsi, we analyzed 5,063 high-quality expressed sequence tags (ESTs) from white muscle cDNA library and predicted the integrity of the clusters annotated to these genes and the physiochemical properties of the putative polypeptides with full length. Up to about 33% of total ESTs were annotated to muscle-related proteins: myosin, actin, tropomyosin/troponin complex, parvalbumin, and Sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCa). Thirty-two isoforms were identified and more than one isoform existed in each of these proteins. Among these isoforms, 14 putative polypeptides were with full length. In addition, about 2% of total ESTs were significantly homologous to "glue" molecules such as alpha-actinins, myosin-binding proteins, myomesin, tropomodulin, cofilin, profilin, twinfilins, coronin-1, and nebulin, which were required for the integrity and maintenance of the muscle sarcomere. The results demonstrated that multiple isoforms of major muscle-related proteins were expressed in S. chuatsi white muscle. The analysis on these isoforms and other proteins sequences will greatly aid our systematic understanding of the high flexibility of mandarin fish white muscle at molecular level and expand the utility of fish systems as models for the muscle genetic control and function.
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Affiliation(s)
- Guoqiang Zhang
- Key Laboratory of Genome Information and Sciences, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China
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31
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Cloning and tissue expression of eleven troponin-C isoforms in the American lobster, Homarus americanus. Comp Biochem Physiol B Biochem Mol Biol 2010; 157:88-101. [DOI: 10.1016/j.cbpb.2010.05.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 05/14/2010] [Accepted: 05/17/2010] [Indexed: 11/19/2022]
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Shaffer JF, Gillis TE. Evolution of the regulatory control of vertebrate striated muscle: the roles of troponin I and myosin binding protein-C. Physiol Genomics 2010; 42:406-19. [PMID: 20484158 DOI: 10.1152/physiolgenomics.00055.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Troponin I (TnI) and myosin binding protein-C (MyBP-C) are key regulatory proteins of contractile function in vertebrate muscle. TnI modulates the Ca2+ activation signal, while MyBP-C regulates cross-bridge cycling kinetics. In vertebrates, each protein is distributed as tissue-specific paralogs in fast skeletal (fs), slow skeletal (ss), and cardiac (c) muscles. The purpose of this study is to characterize how TnI and MyBP-C have changed during the evolution of vertebrate striated muscle and how tissue-specific paralogs have adapted to different physiological conditions. To accomplish this we have completed phylogenetic analyses using the amino acid sequences of all known TnI and MyBP-C isoforms. This includes 99 TnI sequences (fs, ss, and c) from 51 different species and 62 MyBP-C sequences from 26 species, with representatives from each vertebrate group. Results indicate that the role of protein kinase A (PKA) and protein kinase C (PKC) in regulating contractile function has changed during the evolution of vertebrate striated muscle. This is reflected in an increased number of phosphorylatable sites in cTnI and cMyBP-C in endothermic vertebrates and the loss of two PKC sites in fsTnI in a common ancestor of mammals, birds, and reptiles. In addition, we find that His132, Val134, and Asn141 in human ssTnI, previously identified as enabling contractile function during cellular acidosis, are present in all vertebrate cTnI isoforms except those from monotremes, marsupials, and eutherian mammals. This suggests that the replacement of these residues with alternative residues coincides with the evolution of endothermy in the mammalian lineage.
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Affiliation(s)
- Justin F. Shaffer
- Department of Bioengineering, University of Washington, Seattle, Washington; and
| | - Todd E. Gillis
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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Palpant NJ, Houang EM, Delport W, Hastings KEM, Onufriev AV, Sham YY, Metzger JM. Pathogenic peptide deviations support a model of adaptive evolution of chordate cardiac performance by troponin mutations. Physiol Genomics 2010; 42:287-99. [PMID: 20423961 DOI: 10.1152/physiolgenomics.00033.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In cardiac muscle, the troponin (cTn) complex is a key regulator of myofilament calcium sensitivity because it serves as a molecular switch required for translating myocyte calcium fluxes into sarcomeric contraction and relaxation. Studies of several species suggest that ectotherm chordates have myofilaments with heightened calcium responsiveness. However, genetic polymorphisms in cTn that cause increased myofilament sensitivity to activating calcium in mammals result in cardiac disease including arrhythmias, diastolic dysfunction, and increased susceptibility to sudden cardiac death. We hypothesized that specific residue modifications in the regulatory arm of troponin I (TnI) were critical in mediating the observed decrease in myofilament calcium sensitivity within the mammalian taxa. We performed large-scale phylogenetic analysis, atomic resolution molecular dynamics simulations and modeling, and computational alanine scanning. This study provides evidence that a His to Ala substitution within mammalian cardiac TnI (cTnI) reduced the thermodynamic potential at the interface between cTnI and cardiac TnC (cTnC) in the calcium-saturated state by disrupting a strong intermolecular electrostatic interaction. This key residue modification reduced myofilament calcium sensitivity by making cTnI molecularly untethered from cTnC. To meet the requirements for refined mammalian adult cardiac performance, we propose that compensatory evolutionary pressures favored mutations that enhanced the relaxation properties of cTn by decreasing its sensitivity to activating calcium.
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Affiliation(s)
- Nathan J Palpant
- Department of Integrative Biology and Physiology, University of Minnesota Academic Health Center, 321 Church Street SE, Minneapolis, MN 55455, USA
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Messina G, Biressi S, Monteverde S, Magli A, Cassano M, Perani L, Roncaglia E, Tagliafico E, Starnes L, Campbell CE, Grossi M, Goldhamer DJ, Gronostajski RM, Cossu G. Nfix regulates fetal-specific transcription in developing skeletal muscle. Cell 2010; 140:554-66. [PMID: 20178747 DOI: 10.1016/j.cell.2010.01.027] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 11/04/2009] [Accepted: 01/14/2010] [Indexed: 12/29/2022]
Abstract
Skeletal myogenesis, like hematopoiesis, occurs in successive developmental stages that involve different cell populations and expression of different genes. We show here that the transcription factor nuclear factor one X (Nfix), whose expression is activated by Pax7 in fetal muscle, in turn activates the transcription of fetal specific genes such as MCK and beta-enolase while repressing embryonic genes such as slow myosin. In the case of the MCK promoter, Nfix forms a complex with PKC theta that binds, phosphorylates, and activates MEF2A. Premature expression of Nfix activates fetal and suppresses embryonic genes in embryonic muscle, whereas muscle-specific ablation of Nfix prevents fetal and maintains embryonic gene expression in the fetus. Therefore, Nfix acts as a transcriptional switch from embryonic to fetal myogenesis.
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35
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Curran-Everett D. Explorations in statistics: the bootstrap. ADVANCES IN PHYSIOLOGY EDUCATION 2009; 33:286-292. [PMID: 19948676 DOI: 10.1152/advan.00062.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fourth installment of Explorations in Statistics explores the bootstrap. The bootstrap gives us an empirical approach to estimate the theoretical variability among possible values of a sample statistic such as the sample mean. The appeal of the bootstrap is that we can use it to make an inference about some experimental result when the statistical theory is uncertain or even unknown. We can also use the bootstrap to assess how well the statistical theory holds: that is, whether an inference we make from a hypothesis test or confidence interval is justified.
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Affiliation(s)
- Douglas Curran-Everett
- Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, Colorado 80206, USA.
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36
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The cardiac troponin C mutation Leu29Gln found in a patient with hypertrophic cardiomyopathy does not alter contractile parameters in skinned murine myocardium. Basic Res Cardiol 2009; 104:751-60. [PMID: 19506933 PMCID: PMC2758205 DOI: 10.1007/s00395-009-0038-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 04/22/2009] [Accepted: 05/13/2009] [Indexed: 11/12/2022]
Abstract
The present study investigates the effects of the first mutation of troponin C (hcTnCL29Q) found in a patient with hypertrophic cardiomyopathy (HCM) on force–pCa relations and the interplay with phosphorylation of sarcomeric PKA substrates. In triton-skinned murine cardiac fibers, the endogenous mcTnC was extracted and the fibers were subsequently reconstituted with recombinant wild-type and mutant hcTnC. Force–pCa relations of preparations containing hcTnCL29Q or hcTnCWT were similar. Incubation of fibers reconstituted with the recombinant proteins with phosphatase to dephosphorylate sarcomeric PKA substrates induced an increase in Ca2+ sensitivity, slightly more pronounced (0.04 pCa units) in hcTnCL29Q-containing fibers. Incubation of the dephosphorylated fibers with PKA induced significant rightward shifts of force–pCa relations of similar magnitude with both, hcTnCL29Q and hcTnCWT. No significant effects of hcTnCL29Q on the velocity of unloaded shortening were observed. In conclusion, no major differences in contractile parameters of preparations containing hcTnCL29Q compared to hcTnCWT were observed. Therefore, it appears unlikely that hcTnCL29Q induces the development of HCM by affecting the regulation of Ca2+-activated force and interference with PKA-mediated modulation of the Ca2+ sensitivity of contraction.
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37
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Larkin DM, Pape G, Donthu R, Auvil L, Welge M, Lewin HA. Breakpoint regions and homologous synteny blocks in chromosomes have different evolutionary histories. Genome Res 2009; 19:770-7. [PMID: 19342477 DOI: 10.1101/gr.086546.108] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The persistence of large blocks of homologous synteny and a high frequency of breakpoint reuse are distinctive features of mammalian chromosomes that are not well understood in evolutionary terms. To gain a better understanding of the evolutionary forces that affect genome architecture, synteny relationships among 10 amniotes (human, chimp, macaque, rat, mouse, pig, cattle, dog, opossum, and chicken) were compared at <1 human-Mbp resolution. Homologous synteny blocks (HSBs; N = 2233) and chromosome evolutionary breakpoint regions (EBRs; N = 1064) were identified from pairwise comparisons of all genomes. Analysis of the size distribution of HSBs shared in all 10 species' chromosomes (msHSBs) identified three (>20 Mbp) that are larger than expected by chance. Gene network analysis of msHSBs >3 human-Mbp and EBRs <1 Mbp demonstrated that msHSBs are significantly enriched for genes involved in development of the central nervous and other organ systems, whereas EBRs are enriched for genes associated with adaptive functions. In addition, we found EBRs are significantly enriched for structural variations (segmental duplications, copy number variants, and indels), retrotransposed and zinc finger genes, and single nucleotide polymorphisms. These results demonstrate that chromosome breakage in evolution is nonrandom and that HSBs and EBRs are evolving in distinctly different ways. We suggest that natural selection acts on the genome to maintain combinations of genes and their regulatory elements that are essential to fundamental processes of amniote development and biological organization. Furthermore, EBRs may be used extensively to generate new genetic variation and novel combinations of genes and regulatory elements that contribute to adaptive phenotypes.
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Affiliation(s)
- Denis M Larkin
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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38
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Zhu J, Sun Y, Zhao FQ, Yu J, Craig R, Hu S. Analysis of tarantula skeletal muscle protein sequences and identification of transcriptional isoforms. BMC Genomics 2009; 10:117. [PMID: 19298669 PMCID: PMC2674065 DOI: 10.1186/1471-2164-10-117] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 03/19/2009] [Indexed: 12/03/2022] Open
Abstract
Background Tarantula has been used as a model system for studying skeletal muscle structure and function, yet data on the genes expressed in tarantula muscle are lacking. Results We constructed a cDNA library from Aphonopelma sp. (Tarantula) skeletal muscle and got 2507 high-quality 5'ESTs (expressed sequence tags) from randomly picked clones. EST analysis showed 305 unigenes, among which 81 had more than 2 ESTs. Twenty abundant unigenes had matches to skeletal muscle-related genes including actin, myosin, tropomyosin, troponin-I, T and C, paramyosin, muscle LIM protein, muscle protein 20, a-actinin and tandem Ig/Fn motifs (found in giant sarcomere-related proteins). Matches to myosin light chain kinase and calponin were also identified. These results support the existence of both actin-linked and myosin-linked regulation in tarantula skeletal muscle. We have predicted full-length as well as partial cDNA sequences both experimentally and computationally for myosin heavy and light chains, actin, tropomyosin, and troponin-I, T and C, and have deduced the putative peptides. A preliminary analysis of the structural and functional properties was also carried out. Sequence similarities suggested multiple isoforms of most myofibrillar proteins, supporting the generality of multiple isoforms known from previous muscle sequence studies. This may be related to a mix of muscle fiber types. Conclusion The present study serves as a basis for defining the transcriptome of tarantula skeletal muscle, for future in vitro expression of tarantula proteins, and for interpreting structural and functional observations in this model species.
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Affiliation(s)
- Jingui Zhu
- Key laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, PR China.
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Loria V, Leo M, Biasillo G, Dato I, Biasucci LM. Biomarkers in Acute Coronary Syndrome. Biomark Insights 2008; 3:453-468. [PMID: 19578525 PMCID: PMC2688349 DOI: 10.4137/bmi.s588] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND: Evaluation of patients who present to the hospital with acute undifferentiated chest pain or other symptoms and signs suggestive of Acute Coronary Syndrome (ACS) is often a clinical challenge. The initial assessment, requiring a focused history (including risk factors analysis), a physical examination, an electrocardiogram (EKG) and serum cardiac marker determination, is time-consuming and troublesome. Recent investigations have indicated that increases in biomarkers of necrosis, inflammation, ischemia and myocardial stretch may provide earlier assessment of overall patient risk, help in identifying the adequate diagnostic and therapeutic management for each patient and allow for prevention of substantial numbers of new events. APPROACH AND CONTENT: The purpose of this review is to provide an overview of the characteristics of several biomarkers that may have potential clinical utility to identify ACS patients. Patho-physiology, analytical and clinical characteristics have been evaluated for each marker, underlying the properties for potential routine clinical use. SUMMARY: The biomarkers discussed in this review are promising and might lead to improved diagnosis and risk stratification of patients with ACS, however their clinical application requires further studies. It is important to define their clinical role as diagnostic markers, their predictive value and the specificity, standardization and detection limits of the assays.
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Affiliation(s)
- Valentina Loria
- Institute of Cardiology Catholic University 8 Largo Gemelli 00168 Rome, Italy
| | - Milena Leo
- Institute of Cardiology Catholic University 8 Largo Gemelli 00168 Rome, Italy
| | - Gina Biasillo
- Institute of Cardiology Catholic University 8 Largo Gemelli 00168 Rome, Italy
| | - Ilaria Dato
- Institute of Cardiology Catholic University 8 Largo Gemelli 00168 Rome, Italy
| | - Luigi M. Biasucci
- Institute of Cardiology Catholic University 8 Largo Gemelli 00168 Rome, Italy
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Reece KL, Moss RL. Intramolecular interactions in the N-domain of cardiac troponin C are important determinants of calcium sensitivity of force development. Biochemistry 2008; 47:5139-46. [PMID: 18410130 DOI: 10.1021/bi800164c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Myocardial contraction is initiated when Ca2+ binds to site II of cardiac troponin C. This 12-residue EF-hand loop (NH2-DEDGSGTVDFDE-COOH) contains six residues (bold) that coordinate Ca2+ binding and six residues that do not appear to influence Ca2+ binding directly. We have introduced six single-cysteine substitutions (italics) within site II of cTnC to investigate whether these residues are essential for Ca2+ binding affinity in isolation and Ca2+ sensitivity of force development in single muscle fibers. Ca2+ binding properties of mutant proteins were examined in solution and after substitution into rat skinned soleus fibers. Except for the serine mutation, cysteine substitution had no effect on Ca2+ binding on cTnC in solution. However, as part of the myofilament, the threonine mutation reduced Ca2+ sensitivity while the phenylalanine mutation increased Ca2+ sensitivity. Analysis of the available crystal and NMR structures reveals specific structural mechanisms for these effects.
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Affiliation(s)
- Karen L Reece
- Department of Physiology, UniVersity of Wisconsin School of Medicine and Public Health, 123 Service Memorial Institute, 1300 University Avenue, Madison, Wisconsin 53706, USA
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