1
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Marston S. Recent studies of the molecular mechanism of lusitropy due to phosphorylation of cardiac troponin I by protein kinase A. J Muscle Res Cell Motil 2023; 44:201-208. [PMID: 36131171 PMCID: PMC10541847 DOI: 10.1007/s10974-022-09630-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/28/2022] [Indexed: 10/14/2022]
Abstract
Ca2+ acts on troponin and tropomyosin to switch the thin filament on and off, however in cardiac muscle a more graded form of regulation is essential to tailor cardiac output to the body's needs. This is achieved by the action of adrenaline on β1 receptors of heart muscle cells leading to enhanced contractility, faster heart rate and faster relaxation (lusitropy) via activation of the cyclic AMP-dependent protein kinase, PKA. PKA phosphorylates serines 22 and 23 in the N-terminal peptide of cardiac troponin I. As a consequence the rate of Ca2+release from troponin is increased. This is the key determinant of lusitropy. The molecular mechanism of this process has remained unknown long after the mechanism of the troponin Ca2+ switch itself was defined. Investigation of this subtle process at the atomic level poses a challenge, since the change in Ca2+-sensitivity is only about twofold and key parts of the troponin modulation and regulation system are disordered and cannot be fully resolved by conventional structural approaches. We will review recent studies using molecular dynamics simulations together with functional, cryo-em and NMR techniques that have started to give us a precise picture of how phosphorylation of troponin I modulates the dynamics of troponin to produce the lusitropic effect.
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2
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Deranek AE, Baldo AP, Lynn ML, Schwartz SD, Tardiff JC. Structure and Dynamics of the Flexible Cardiac Troponin T Linker Domain in a Fully Reconstituted Thin Filament. Biochemistry 2022; 61:1229-1242. [PMID: 35696530 DOI: 10.1021/acs.biochem.2c00091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural analysis of large protein complexes has been greatly enhanced through the application of electron microscopy techniques. One such multiprotein complex, the cardiac thin filament (cTF), has cyclic interactions with thick filament proteins to drive contraction of the heart that has recently been the subject of such studies. As important as these studies are, they provide limited or no information on highly flexible regions that in isolation would be characterized as inherently disordered. One such region is the extended cardiac troponin T (cTnT) linker between the regions of cTnT which have been labeled TNT1 and TNT2. It comprises a hinge region (residues 158-166) and a highly flexible region (residues 167-203). Critically, this region modulates the troponin/tropomyosin complex's position across the actin filament. Thus, the cTnT linker structure and dynamics are central to the regulation of the function of cardiac muscles, but up to now, it was ill-understood. To establish the cTnT linker structure, we coupled an atomistic computational cTF model with time-resolved fluorescence resonance energy transfer measurements in both ±Ca2+ conditions utilizing fully reconstituted cTFs. We mapped the cTnT linker's positioning across the actin filament, and by coupling the experimental results to computation, we found mean structures and ranges of motion of this part of the complex. With this new insight, we can now address cTnT linker structural dynamics in both myofilament activation and disease.
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Affiliation(s)
- Andrea E Deranek
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85721, United States
| | - Anthony P Baldo
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Melissa L Lynn
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85721, United States
| | - Steven D Schwartz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85721, United States
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3
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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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4
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Johnston JR, Landim-Vieira M, Marques MA, de Oliveira GAP, Gonzalez-Martinez D, Moraes AH, He H, Iqbal A, Wilnai Y, Birk E, Zucker N, Silva JL, Chase PB, Pinto JR. The intrinsically disordered C terminus of troponin T binds to troponin C to modulate myocardial force generation. J Biol Chem 2019; 294:20054-20069. [PMID: 31748410 PMCID: PMC6937556 DOI: 10.1074/jbc.ra119.011177] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 11/13/2019] [Indexed: 12/15/2022] Open
Abstract
Aberrant regulation of myocardial force production represents an early biomechanical defect associated with sarcomeric cardiomyopathies, but the molecular mechanisms remain poorly defined. Here, we evaluated the pathogenicity of a previously unreported sarcomeric gene variant identified in a pediatric patient with sporadic dilated cardiomyopathy, and we determined a molecular mechanism. Trio whole-exome sequencing revealed a de novo missense variant in TNNC1 that encodes a p.I4M substitution in the N-terminal helix of cardiac troponin C (cTnC). Reconstitution of this human cTnC variant into permeabilized porcine cardiac muscle preparations significantly decreases the magnitude and rate of isometric force generation at physiological Ca2+-activation levels. Computational modeling suggests that this inhibitory effect can be explained by a decrease in the rates of cross-bridge attachment and detachment. For the first time, we show that cardiac troponin T (cTnT), in part through its intrinsically disordered C terminus, directly binds to WT cTnC, and we find that this cardiomyopathic variant displays tighter binding to cTnT. Steady-state fluorescence and NMR spectroscopy studies suggest that this variant propagates perturbations in cTnC structural dynamics to distal regions of the molecule. We propose that the intrinsically disordered C terminus of cTnT directly interacts with the regulatory N-domain of cTnC to allosterically modulate Ca2+ activation of force, perhaps by controlling the troponin I switching mechanism of striated muscle contraction. Alterations in cTnC-cTnT binding may compromise contractile performance and trigger pathological remodeling of the myocardium.
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Affiliation(s)
- Jamie R Johnston
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Mayra A Marques
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - David Gonzalez-Martinez
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
| | - Adolfo H Moraes
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| | - Huan He
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306
| | - Anwar Iqbal
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Yael Wilnai
- Department of Pediatrics, Dana-Dwek ChildrenγÇÖs Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel 6423906
| | - Einat Birk
- Department of Cardiology, Schneider ChildrenγÇÖs Medical Center, Tel Aviv University, Petah Tikva, Israel 4920235
| | - Nili Zucker
- Department of Cardiology, Schneider ChildrenγÇÖs Medical Center, Tel Aviv University, Petah Tikva, Israel 4920235
| | - Jerson L Silva
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - P Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306
| | - Jose Renato Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306
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5
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Abstract
AbstractThe dynamics of proteins in solution includes a variety of processes, such as backbone and side-chain fluctuations, interdomain motions, as well as global rotational and translational (i.e. center of mass) diffusion. Since protein dynamics is related to protein function and essential transport processes, a detailed mechanistic understanding and monitoring of protein dynamics in solution is highly desirable. The hierarchical character of protein dynamics requires experimental tools addressing a broad range of time- and length scales. We discuss how different techniques contribute to a comprehensive picture of protein dynamics, and focus in particular on results from neutron spectroscopy. We outline the underlying principles and review available instrumentation as well as related analysis frameworks.
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6
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Johnson D, Angus CW, Chalovich JM. Stepwise C-Terminal Truncation of Cardiac Troponin T Alters Function at Low and Saturating Ca 2. Biophys J 2018; 115:702-712. [PMID: 30057009 DOI: 10.1016/j.bpj.2018.06.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 06/19/2018] [Accepted: 06/29/2018] [Indexed: 11/16/2022] Open
Abstract
Activation of striated muscle contraction occurs in response to Ca2+ binding to troponin C. The resulting reorganization of troponin repositions tropomyosin on actin and permits activation of myosin-catalyzed ATP hydrolysis. It now appears that the C-terminal 14 amino acids of cardiac troponin T (TnT) control the level of activity at both low and high Ca2+. We made a series of C-terminal truncation mutants of human cardiac troponin T, isoform 2, to determine if the same residues of TnT are involved in the low and high Ca2+ effects. We measured the effect of these mutations on the normalized ATPase activity at saturating Ca2+. Changes in acrylodan tropomyosin fluorescence and the degree of Ca2+ stimulation of the rate of binding of rigor myosin subfragment 1 to pyrene-labeled actin-tropomyosin-troponin were measured at low Ca2+. These measurements define the distribution of actin-tropomyosin-troponin among the three regulatory states. Residues SKTR and GRWK of TnT were required for the functioning of TnT at both low and high Ca2+. Thus, the effects on forming the inactive B-state and in retarding formation of the active M-state require the same regions of TnT. We also observed that the rate of binding of rigor subfragment 1 to pyrene-labeled regulated actin at saturating Ca2+ was higher for the truncation mutants than for wild-type TnT. This violated an assumption necessary for determining the B-state population by this kinetic method.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - C William Angus
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Joseph M Chalovich
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina.
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7
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Bohlooli Ghashghaee N, Li KL, Solaro RJ, Dong WJ. Role of the C-terminus mobile domain of cardiac troponin I in the regulation of thin filament activation in skinned papillary muscle strips. Arch Biochem Biophys 2018; 648:27-35. [PMID: 29704484 DOI: 10.1016/j.abb.2018.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 04/18/2018] [Accepted: 04/21/2018] [Indexed: 11/19/2022]
Abstract
The C-terminus mobile domain of cTnI (cTnI-MD) is a highly conserved region which stabilizes the actin-cTnI interaction during the diastole. Upon Ca2+-binding to cTnC, cTnI-MD participates in a regulatory switching that involves cTnI to switch from interacting with actin toward interacting with the Ca2+-regulatory domain of cTnC. Despite many studies targeting the cTnI-MD, the role of this region in the length-dependent activation of cardiac contractility is yet to be determined. The present study investigated the functional consequences of losing the entire cTnI-MD in cTnI(1-167) truncation mutant, as it was exchanged for endogenous cTnI in skinned rat papillary muscle fibers. The influence of cTnI-MD truncation on the extent of the N-domain of cTnC hydrophobic cleft opening and the steady-state force as a function of sarcomere length (SL), cross-bridge state, and [Ca2+] was assessed using the simultaneous in situ time-resolved FRET and force measurements at short (1.8 μm) and long (2.2 μm) SLs. Our results show the significant role of cTnI-MD in the length dependent thin filament activation and the coupling between thin and thick filament regulations affected by SL. Our results also suggest that cTnI-MD transmits the effects of SL change to the core of troponin complex.
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Affiliation(s)
- Nazanin Bohlooli Ghashghaee
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - King-Lun Li
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Wen-Ji Dong
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA; The Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA.
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8
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Matsuo T, Tominaga T, Kono F, Shibata K, Fujiwara S. Modulation of the picosecond dynamics of troponin by the cardiomyopathy-causing mutation K247R of troponin T observed by quasielastic neutron scattering. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1781-1789. [PMID: 28923663 DOI: 10.1016/j.bbapap.2017.09.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/18/2017] [Accepted: 09/14/2017] [Indexed: 11/16/2022]
Abstract
Troponin (Tn), consisting of three subunits (TnC, TnI, and TnT), regulates cardiac muscle contraction in a Ca2+-dependent manner. Various point mutations of human cardiac Tn are known to cause familial hypertrophic cardiomyopathy due to aberration of the regulatory function. In this study, we investigated the effects of one of these mutations, K247R of TnT, on the picosecond dynamics of the Tn core domain (Tn-CD), consisting of TnC, TnI and TnT2 (183-288 residues of TnT), by carrying out the quasielastic neutron scattering measurements on the reconstituted Tn-CD containing either the wild-type TnT2 (wtTn-CD) or the mutant TnT2 (K247R-Tn-CD) in the absence and presence of Ca2+. It was found that Ca2+-binding to the wtTn-CD decreases the residence time of atomic motions in the Tn-CD with slight changes in amplitudes, suggesting that the regulatory function mainly requires modulation of frequency of atomic motions. On the other hand, the K247R-Tn-CD shows different dynamic behavior from that of the wtTn-CD both in the absence and presence of Ca2+. In particular, the K247R-Tn-CD exhibits a larger amplitude than the wtTn-CD in the presence of Ca2+, suggesting that the mutant can explore larger conformational space than the wild-type. This increased flexibility should be relevant to the functional aberration of this mutant.
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Affiliation(s)
- Tatsuhito Matsuo
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Tokai, Ibaraki 319-1106, Japan
| | - Taiki Tominaga
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan
| | - Fumiaki Kono
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Tokai, Ibaraki 319-1106, Japan
| | - Kaoru Shibata
- Neutron Science Section, J-PARC Center, Tokai, Ibaraki 319-1195, Japan
| | - Satoru Fujiwara
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Tokai, Ibaraki 319-1106, Japan.
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9
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Na I, Kong MJ, Straight S, Pinto JR, Uversky VN. Troponins, intrinsic disorder, and cardiomyopathy. Biol Chem 2017; 397:731-51. [PMID: 27074551 DOI: 10.1515/hsz-2015-0303] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 04/05/2016] [Indexed: 11/15/2022]
Abstract
Cardiac troponin is a dynamic complex of troponin C, troponin I, and troponin T (TnC, TnI, and TnT, respectively) found in the myocyte thin filament where it plays an essential role in cardiac muscle contraction. Mutations in troponin subunits are found in inherited cardiomyopathies, such as hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). The highly dynamic nature of human cardiac troponin and presence of numerous flexible linkers in its subunits suggest that understanding of structural and functional properties of this important complex can benefit from the consideration of the protein intrinsic disorder phenomenon. We show here that mutations causing decrease in the disorder score in TnI and TnT are significantly more abundant in HCM and DCM than mutations leading to the increase in the disorder score. Identification and annotation of intrinsically disordered regions in each of the troponin subunits conducted in this study can help in better understanding of the roles of intrinsic disorder in regulation of interactomes and posttranslational modifications of these proteins. These observations suggest that disease-causing mutations leading to a decrease in the local flexibility of troponins can trigger a whole plethora of functional changes in the heart.
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10
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Veltri T, de Oliveira GAP, Bienkiewicz EA, Palhano FL, Marques MDA, Moraes AH, Silva JL, Sorenson MM, Pinto JR. Amide hydrogens reveal a temperature-dependent structural transition that enhances site-II Ca 2+-binding affinity in a C-domain mutant of cardiac troponin C. Sci Rep 2017; 7:691. [PMID: 28386062 PMCID: PMC5429600 DOI: 10.1038/s41598-017-00777-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 03/14/2017] [Indexed: 01/07/2023] Open
Abstract
The hypertrophic cardiomyopathy-associated mutant D145E, in cardiac troponin C (cTnC) C-domain, causes generalised instability at multiple sites in the isolated protein. As a result, structure and function of the mutant are more susceptible to higher temperatures. Above 25 °C there are large, progressive increases in N-domain Ca2+-binding affinity for D145E but only small changes for the wild-type protein. NMR-derived backbone amide temperature coefficients for many residues show a sharp transition above 30–40 °C, indicating a temperature-dependent conformational change that is most prominent around the mutated EF-hand IV, as well as throughout the C-domain. Smaller, isolated changes occur in the N-domain. Cardiac skinned fibres reconstituted with D145E are more sensitive to Ca2+ than fibres reconstituted with wild-type, and this defect is amplified near body-temperature. We speculate that the D145E mutation destabilises the native conformation of EF-hand IV, leading to a transient unfolding and dissociation of helix H that becomes more prominent at higher temperatures. This creates exposed hydrophobic surfaces that may be capable of binding unnaturally to a variety of targets, possibly including the N-domain of cTnC when it is in its open Ca2+-saturated state. This would constitute a potential route for propagating signals from one end of TnC to the other.
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Affiliation(s)
- Tiago Veltri
- Department of Biomedical Sciences, Florida State University College of Medicine, 1115 West Call Street, Tallahassee, FL, 32306-4300, USA.,Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas F° 373, Cidade Universitária, Rio de Janeiro, 21941-902, RJ, Brazil
| | - Guilherme A P de Oliveira
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ewa A Bienkiewicz
- Department of Biomedical Sciences, Florida State University College of Medicine, 1115 West Call Street, Tallahassee, FL, 32306-4300, USA
| | - Fernando L Palhano
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas F° 373, Cidade Universitária, Rio de Janeiro, 21941-902, RJ, Brazil
| | - Mayra de A Marques
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Adolfo H Moraes
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Brazil
| | - Jerson L Silva
- Programa de Biologia Estrutural, Instituto de Bioquímica Médica, Instituto Nacional de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Martha M Sorenson
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas F° 373, Cidade Universitária, Rio de Janeiro, 21941-902, RJ, Brazil
| | - 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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11
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Siddiqui JK, Tikunova SB, Walton SD, Liu B, Meyer M, de Tombe PP, Neilson N, Kekenes-Huskey PM, Salhi HE, Janssen PML, Biesiadecki BJ, Davis JP. Myofilament Calcium Sensitivity: Consequences of the Effective Concentration of Troponin I. Front Physiol 2016; 7:632. [PMID: 28066265 PMCID: PMC5175494 DOI: 10.3389/fphys.2016.00632] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 12/05/2016] [Indexed: 12/04/2022] Open
Abstract
Control of calcium binding to and dissociation from cardiac troponin C (TnC) is essential to healthy cardiac muscle contraction/relaxation. There are numerous aberrant post-translational modifications and mutations within a plethora of contractile, and even non-contractile, proteins that appear to imbalance this delicate relationship. The direction and extent of the resulting change in calcium sensitivity is thought to drive the heart toward one type of disease or another. There are a number of molecular mechanisms that may be responsible for the altered calcium binding properties of TnC, potentially the most significant being the ability of the regulatory domain of TnC to bind the switch peptide region of TnI. Considering TnI is essentially tethered to TnC and cannot diffuse away in the absence of calcium, we suggest that the apparent calcium binding properties of TnC are highly dependent upon an “effective concentration” of TnI available to bind TnC. Based on our previous work, TnI peptide binding studies and the calcium binding properties of chimeric TnC-TnI fusion constructs, and building upon the concept of effective concentration, we have developed a mathematical model that can simulate the steady-state and kinetic calcium binding properties of a wide assortment of disease-related and post-translational protein modifications in the isolated troponin complex and reconstituted thin filament. We predict that several TnI and TnT modifications do not alter any of the intrinsic calcium or TnI binding constants of TnC, but rather alter the ability of TnC to “find” TnI in the presence of calcium. These studies demonstrate the apparent consequences of the effective TnI concentration in modulating the calcium binding properties of TnC.
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Affiliation(s)
- Jalal K Siddiqui
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Svetlana B Tikunova
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Shane D Walton
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Bin Liu
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Meredith Meyer
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Pieter P de Tombe
- Cell and Molecular Physiology, Loyola University Chicago Maywood, IL, USA
| | - Nathan Neilson
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | | | - Hussam E Salhi
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Paul M L Janssen
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Brandon J Biesiadecki
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| | - Jonathan P Davis
- Department of Physiology and Cell Biology and the Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
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Barnes DE, Hwang H, Ono K, Lu H, Ono S. Molecular evolution of troponin I and a role of its N-terminal extension in nematode locomotion. Cytoskeleton (Hoboken) 2016; 73:117-30. [PMID: 26849746 DOI: 10.1002/cm.21281] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 01/22/2016] [Accepted: 01/27/2016] [Indexed: 01/29/2023]
Abstract
The troponin complex, composed of troponin T (TnT), troponin I (TnI), and troponin C (TnC), is the major calcium-dependent regulator of muscle contraction, which is present widely in both vertebrates and invertebrates. Little is known about evolutionary aspects of troponin in the animal kingdom. Using a combination of data mining and functional analysis of TnI, we report evidence that an N-terminal extension of TnI is present in most of bilaterian animals as a functionally important domain. Troponin components have been reported in species in most of representative bilaterian phyla. Comparison of TnI sequences shows that the core domains are conserved in all examined TnIs, and that N- and C-terminal extensions are variable among isoforms and species. In particular, N-terminal extensions are present in all protostome TnIs and chordate cardiac TnIs but lost in a subset of chordate TnIs including vertebrate skeletal-muscle isoforms. Transgenic rescue experiments in Caenorhabditis elegans striated muscle show that the N-terminal extension of TnI (UNC-27) is required for coordinated worm locomotion but not in sarcomere assembly and single muscle-contractility kinetics. These results suggest that N-terminal extensions of TnIs are retained from a TnI ancestor as a functional domain.
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Affiliation(s)
- Dawn E Barnes
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia
| | - Hyundoo Hwang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia.,School of Engineering and Sciences, Technológico de Monterrey, Monterrey, Nuevo León, Mexico
| | - Kanako Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia
| | - Hang Lu
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia.,Interdisciplinary Program of Bioengineering, Georgia Institute of Technology, Atlanta, Georgia.,The Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Shoichiro Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia
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Premchandar A, Mücke N, Poznański J, Wedig T, Kaus-Drobek M, Herrmann H, Dadlez M. Structural Dynamics of the Vimentin Coiled-coil Contact Regions Involved in Filament Assembly as Revealed by Hydrogen-Deuterium Exchange. J Biol Chem 2016; 291:24931-24950. [PMID: 27694444 PMCID: PMC5122765 DOI: 10.1074/jbc.m116.748145] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/26/2016] [Indexed: 01/07/2023] Open
Abstract
Intermediate filaments (IF) are major constituents of the cytoskeleton of metazoan cells. They are not only responsible for the mechanical properties but also for various physiological activities in different cells and tissues. The building blocks of IFs are extended coiled-coil-forming proteins exhibiting a characteristic central α-helical domain ("rod"). The fundamental principles of the filament assembly mechanism and the network formation have been widely elucidated for the cytoplasmic IF protein vimentin. Also, a comprehensive structural model for the tetrameric complex of vimentin has been obtained by X-ray crystallography in combination with various biochemical and biophysical techniques. To extend these static data and to investigate the dynamic properties of the full-length proteins in solution during the various assembly steps, we analyzed the patterns of hydrogen-deuterium exchange in vimentin and in four variants carrying point mutations in the IF consensus motifs present at either end of the α-helical rod that cause an assembly arrest at the unit-length filament (ULF) stage. The results yielded unique insights into the structural properties of subdomains within the full-length vimentin, in particular in regions of contact in α-helical and linker segments that stabilize different oligomeric forms such as tetramers, ULFs, and mature filaments. Moreover, hydrogen-deuterium exchange analysis of the point-mutated variants directly demonstrated the active role of the IF consensus motifs in the oligomerization mechanism of tetramers during ULF formation. Ultimately, using molecular dynamics simulation procedures, we provide a structural model for the subdomain-mediated tetramer/tetramer interaction via "cross-coiling" as the first step of the assembly process.
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Affiliation(s)
- Aiswarya Premchandar
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02-106 Warsaw, Poland
| | | | - Jarosław Poznański
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02-106 Warsaw, Poland
| | | | - Magdalena Kaus-Drobek
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02-106 Warsaw, Poland
| | - Harald Herrmann
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany, and
- the Institute of Neuropathology, University Hospital Erlangen, D-91054 Erlangen, Germany
| | - Michał Dadlez
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02-106 Warsaw, Poland,
- the Institute of Genetics and Biotechnology, Biology Department, University of Warsaw, Miecznikowa 3, 02-106 Warsaw, Poland
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14
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Papadaki M, Marston SB. The Importance of Intrinsically Disordered Segments of Cardiac Troponin in Modulating Function by Phosphorylation and Disease-Causing Mutations. Front Physiol 2016; 7:508. [PMID: 27853436 PMCID: PMC5089987 DOI: 10.3389/fphys.2016.00508] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/17/2016] [Indexed: 11/18/2022] Open
Abstract
Troponin plays a central role in regulation of muscle contraction. It is the Ca2+ switch of striated muscles including the heart and in the cardiac muscle it is physiologically modulated by PKA-dependent phosphorylation at Ser22 and 23. Many cardiomyopathy-related mutations affect Ca2+ regulation and/or disrupt the relationship between Ca2+ binding and phosphorylation. Unlike the mechanism of heart activation, the modulation of Ca2+-sensitivity by phosphorylation of the cardiac specific N-terminal segment of TnI (1–30) is structurally subtle and has proven hard to investigate. The crystal structure of cardiac troponin describes only the relatively stable core of the molecule and the crucial mobile parts of the molecule are missing including TnI C-terminal region, TnI (1–30), TnI (134–149) (“inhibitory” peptide) and the C-terminal 28 amino acids of TnT that are intrinsically disordered. Recent studies have been performed to answer this matter by building structural models of cardiac troponin in phosphorylated and dephosphorylated states based on peptide NMR studies. Now these have been updated by more recent concepts derived from molecular dynamic simulations treating troponin as a dynamic structure. The emerging model confirms the stable core structure of troponin and the mobile structure of the intrinsically disordered segments. We will discuss how we can describe these segments in terms of dynamic transitions between a small number of states, with the probability distributions being altered by phosphorylation and by HCM or DCM-related mutations that can explain how Ca2+-sensitivity is modulated by phosphorylation and the effects of mutations.
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Affiliation(s)
- Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University of Chicago Maywood, IL, USA
| | - Steven B Marston
- Myocardial Function, National Heart and Lung Institute, Imperial College London London, UK
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15
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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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Matsuo T, Takeda S, Oda T, Fujiwara S. Structures of the troponin core domain containing the cardiomyopathy-causing mutants studied by small-angle X-ray scattering. Biophys Physicobiol 2015; 12:145-58. [PMID: 27493864 PMCID: PMC4736830 DOI: 10.2142/biophysico.12.0_145] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 12/01/2015] [Indexed: 12/01/2022] Open
Abstract
Troponin (Tn), consisting of three subunits, TnC, TnI, and TnT, is a protein in the thin filaments in muscle, and, together with another thin-filament protein tropomyosin (Tm), plays a major role in regulation of muscle contraction. Various mutations of Tn cause familial hypertrophic cardiomyopathy. These mutations are directly related to aberrations in this regulatory mechanism. Here we focus on the mutations E244D and K247R of TnT, which reside in the middle of the pathway of the Ca(2+)-binding signal from TnC to Tm. These mutations induce an increase in the maximum tension of cardiac muscle without changes in Ca(2+)-sensitivity. As a first step toward elucidating the molecular mechanism underlying this functional aberration, we carried out small-angle X-ray scattering experiments on the Tn core domain containing the wild type subunits and those containing the mutant TnT in the absence and presence of Ca(2+). Changes in the overall shape induced by the mutations were detected for the first time by the changes in the radius of gyration and the maximum dimension between the wild type and the mutants. Analysis of the scattering curves by model calculations shows that TnC adopts a dumbbell structure regardless of the mutations, and that the mutations change the distributions of the conformational ensembles so that the flexible N- and C-terminal regions of TnT become close to the center of the whole moelcule. This suggests, since these regions are related to the Tn-Tm interactions, that alteration of the Tn-Tm interactions induced by the mutations causes the functional aberration.
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Affiliation(s)
- Tatsuhito Matsuo
- Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
| | - Soichi Takeda
- National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan
| | - Toshiro Oda
- RIKEN SPring-8 center, RIKEN Harima Institute, Sayo, Hyogo 679-5148, Japan
| | - Satoru Fujiwara
- Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
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