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Kalyva A, Parthenakis FI, Marketou ME, Kontaraki JE, Vardas PE. Biochemical characterisation of Troponin C mutations causing hypertrophic and dilated cardiomyopathies. J Muscle Res Cell Motil 2014; 35:161-78. [PMID: 24744096 DOI: 10.1007/s10974-014-9382-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/02/2014] [Indexed: 01/27/2023]
Abstract
Cardiac muscle contraction occurs through an interaction of the myosin head with the actin filaments, a process which is regulated by the troponin complex together with tropomyosin and is Ca(2+) dependent. Mutations in genes encoding sarcomeric proteins are a common cause of familial hypertrophic and dilated cardiomyopathies. The scope of this review is to gather information from studies regarding the in vitro characterisation of six HCM and six DCM mutations on the cardiac TnC gene and to suggest, if possible, how they may lead to dysfunction. Since TnC is the subunit responsible for Ca(2+) binding, mutations in the TnC could possibly have a strong impact on Ca(2+) binding affinities. Furthermore, the interactions of mutant TnCs with their binding partners could be altered. From the characterisation studies available to date, we can conclude that the HCM mutations on TnC increase significantly the Ca(2+) sensitivity of force development or of ATPase activity, producing large pCa shifts in comparison to WT TnC. In contrast, the DCM mutations on TnC have a tendency to decrease the Ca(2+) sensitivity of force development or of ATPase activity in comparison to WT TnC. Furthermore, the DCM mutants of TnC are not responsive to the TnI phosphorylation signal resulting in filaments that preserve their Ca(2+) sensitivity in contrast to WT filaments that experience a decrease in Ca(2+) sensitivity upon TnI phosphorylation.
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Affiliation(s)
- Athanasia Kalyva
- Molecular Cardiology Laboratory, Department of Cardiology, School of Medicine, University of Crete, Crete, Greece,
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2
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de Oliveira GAP, Rocha CB, Marques MDA, Cordeiro Y, Sorenson MM, Foguel D, Silva JL, Suarez MC. Insights into the Intramolecular Coupling between the N- and C-Domains of Troponin C Derived from High-Pressure, Fluorescence, Nuclear Magnetic Resonance, and Small-Angle X-ray Scattering Studies. Biochemistry 2012; 52:28-40. [DOI: 10.1021/bi301139d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- 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, 21941-902 Rio de Janeiro, Brazil
| | - Cristiane B. Rocha
- UNIRIO-Universidade Federal do Estado do Rio de Janeiro, CCBS-Centro de
Ciências Biológicas e da Saúde, Instituto Biomédico-IB,
Departamento de Bioquímica, Rua Frei Caneca 94-Centro, Rio
de Janeiro, 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, 21941-902 Rio de Janeiro, Brazil
| | - Yraima Cordeiro
- Faculdade
de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro,
Brazil
| | - Martha M. Sorenson
- 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, 21941-902 Rio de Janeiro, Brazil
| | - Débora Foguel
- 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, 21941-902 Rio de Janeiro, 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, 21941-902 Rio de Janeiro, Brazil
| | - Marisa C. Suarez
- 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, 21941-902 Rio de Janeiro, Brazil
- Programa de Biologia
Estrutural,
Instituto de Bioquímica Médica-Polo Xerém, Universidade Federal do Rio de Janeiro, Xerém,
Brazil
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Varughese JF, Chalovich JM, Li Y. Molecular dynamics studies on troponin (TnI-TnT-TnC) complexes: insight into the regulation of muscle contraction. J Biomol Struct Dyn 2010; 28:159-74. [PMID: 20645650 DOI: 10.1080/07391102.2010.10507350] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Mutations of any subunit of the troponin complex may lead to serious disorders. Rational approaches to managing these disorders require knowledge of the complex interactions among the three subunits that are required for proper function. Molecular dynamics (MD) simulations were performed for both skeletal (sTn) and cardiac (cTn) troponin. The interactions and correlated motions among the three components of the troponin complex were analyzed using both Molecular Mechanics-Generalized Born Surface Area (MMGBSA) and cross-correlation techniques. The TnTH2 helix was strongly positively correlated with the two long helices of TnI. The C domain of TnC was positively correlated with TnI and TnT. The N domain of TnC was negatively correlated with TnI and TnT in cTn, but not in sTn. The two C-domain calcium-binding sites of TnC were dynamically correlated. The two regulatory N-domain calcium-binding sites of TnC were dynamically correlated, even though the calcium-binding site I is dysfunctional. The strong interaction residue pairs and the strong dynamically correlated residues pairs among the three components of troponin complexes were identified. These correlated motions are consistent with the idea that there is a high degree of cooperativity among the components of the regulatory complex in response to Ca(2+) and other effectors. This approach may give insight into the mechanism by which mutations of troponin cause disease. It is interesting that some observed disease causing mutations fall within regions of troponin that are strongly correlated or interacted.
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Affiliation(s)
- Jayson F Varughese
- Department of Chemistry, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA
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Mutation of outer-shell residues modulates metal ion co-ordination strength in a metalloenzyme. Biochem J 2010; 429:313-21. [DOI: 10.1042/bj20100233] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metal ion co-ordination sites of many metalloproteins have been characterized by a variety of spectroscopic techniques and small-molecule model systems, revealing many important insights into the structural determinants of metal ion co-ordination. However, our understanding of this fundamentally and practically important phenomenon remains frustratingly simplistic; in many proteins it is essentially impossible to predict metal ion specificity and the effects of remote ‘outer-shell’ residues on metal ion co-ordination strength are also poorly defined. This is exemplified by our inability to explain why metalloenzymes with identical metal ion co-ordination spheres, such as the closely related orthologues of bacterial PTE (phosphotriesterase) from Agrobacterium radiobacter and Pseudomonas diminuta, display different metal ion specificity and co-ordination strength. In the present study, we present a series of PTE variants that all possess identical metal ion co-ordination spheres, yet display large differences in their metal ion co-ordination strength. Using measurement of the rates of metal ion dissociation from the active site alongside analysis of structural data obtained through X-ray crystallography, we show that ‘outer-shell’ residues provide essential support for the metal ion ligands, in effect buttressing them in their optimal orientation. Remote mutations appear to modulate metal ion interactions by increasing or decreasing the stabilizing effects of these networks. The present study therefore provides a description of how the greater protein fold can be modified to ‘tune’ the strength of metal ion co-ordination and metal ion specificity, as well as reinforcing the concept of proteins as ensembles of conformational states with unique structures and biochemical properties.
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Parvatiyar MS, Pinto JR, Liang J, Potter JD. Predicting cardiomyopathic phenotypes by altering Ca2+ affinity of cardiac troponin C. J Biol Chem 2010; 285:27785-97. [PMID: 20566645 DOI: 10.1074/jbc.m110.112326] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cardiac diseases associated with mutations in troponin subunits include hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and restrictive cardiomyopathy (RCM). Altered calcium handling in these diseases is evidenced by changes in the Ca(2+) sensitivity of contraction. Mutations in the Ca(2+) sensor, troponin C (TnC), were generated to increase/decrease the Ca(2+) sensitivity of cardiac skinned fibers to create the characteristic effects of DCM, HCM, and RCM. We also used a reconstituted assay to determine the mutation effects on ATPase activation and inhibition. One mutant (A23Q) was found with HCM-like properties (increased Ca(2+) sensitivity of force and normal levels of ATPase inhibition). Three mutants (S37G, V44Q, and L48Q) were identified with RCM-like properties (a large increase in Ca(2+) sensitivity, partial loss of ATPase inhibition, and increased basal force). Two mutations were identified (E40A and I61Q) with DCM properties (decreased Ca(2+) sensitivity, maximal force recovery, and activation of the ATPase at high [Ca(2+)]). Steady-state fluorescence was utilized to assess Ca(2+) affinity in isolated cardiac (c)TnCs containing F27W and did not necessarily mirror the fiber Ca(2+) sensitivity. Circular dichroism of mutant cTnCs revealed a trend where increased alpha-helical content correlated with increased Ca(2+) sensitivity in skinned fibers and vice versa. The main findings from this study were as follows: 1) cTnC mutants demonstrated distinct functional phenotypes reminiscent of bona fide HCM, RCM, and DCM mutations; 2) a region in cTnC associated with increased Ca(2+) sensitivity in skinned fibers was identified; and 3) the F27W reporter mutation affected Ca(2+) sensitivity, maximal force, and ATPase activation of some mutants.
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Affiliation(s)
- Michelle S Parvatiyar
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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6
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A novel mutant cardiac troponin C disrupts molecular motions critical for calcium binding affinity and cardiomyocyte contractility. Biophys J 2008; 94:3577-89. [PMID: 18212018 DOI: 10.1529/biophysj.107.112896] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Troponin C (TnC) belongs to the superfamily of EF-hand (helix-loop-helix) Ca(2+)-binding proteins and is an essential component of the regulatory thin filament complex. In a patient diagnosed with idiopathic dilated cardiomyopathy, we identified two novel missense mutations localized in the regulatory Ca(2+)-binding Site II of TnC, TnC((E59D,D75Y)). Expression of recombinant TnC((E59D,D75Y)) in isolated rat cardiomyocytes induced a marked decrease in contractility despite normal intracellular calcium homeostasis in intact cardiomyocytes and resulted in impaired myofilament calcium responsiveness in Triton-permeabilized cardiomyocytes. Expression of the individual mutants in cardiomyocytes showed that TnC(D75Y) was able to recapitulate the TnC((E59D,D75Y)) phenotype, whereas TnC(E59D) was functionally benign. Force-pCa relationships in TnC((E59D,D75Y)) reconstituted rabbit psoas fibers and fluorescence spectroscopy of TnC((E59D,D75Y)) labeled with 2-[(4'-iodoacetamide)-aniline]naphthalene-6-sulfonic acid showed a decrease in myofilament Ca(2+) sensitivity and Ca(2+) binding affinity, respectively. Furthermore, computational analysis of TnC showed the Ca(2+)-binding pocket as an active region of concerted motions, which are decreased markedly by mutation D75Y. We conclude that D75Y interferes with proper concerted motions within the regulatory Ca(2+)-binding pocket of TnC that hinders the relay of the thin filament calcium signal, thereby providing a primary stimulus for impaired cardiomyocyte contractility. This in turn may trigger pathways leading to aberrant ventricular remodeling and ultimately a dilated cardiomyopathy phenotype.
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Finley NL, Rosevear PR. Introduction of negative charge mimicking protein kinase C phosphorylation of cardiac troponin I. Effects on cardiac troponin C. J Biol Chem 2004; 279:54833-40. [PMID: 15485824 DOI: 10.1074/jbc.m408304200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase C phosphorylation of cardiac troponin, the Ca(2+)-sensing switch in muscle contraction, is capable of modulating the response of cardiac muscle to a Ca(2+) ion concentration. The N-domain of cardiac troponin I contains two protein kinase C phosphorylation sites. Although the physiological consequences of phosphorylation at Ser(43)/Ser(45) are known, the molecular mechanisms responsible for these functional changes have yet to be established. In this work, NMR was used to identify conformational and dynamic changes in cardiac troponin C upon binding a phosphomimetic troponin I, having Ser(43)/Ser(45) mutated to Asp. Chemical shift perturbation mapping indicated that residues in helix G were most affected. Smaller chemical shift changes were observed in residues located in the Ca(2+)/Mg(2+)-binding loops. Amide hydrogen/deuterium exchange rates in the C-lobe of troponin C were compared in complexes containing either the wild-type or phosphomimetic N-domain of troponin I. In the presence of a phosphomimetic domain, exchange rates in helix G increased, whereas a decrease in exchange rates for residues mapping to Ca(2+)/Mg(2+)-binding loops III and IV was observed. Increased exchange rates are consistent with destabilization of the Thr(129)-Asp(132) helix capping box previously characterized in helix G. The perturbation of helix G and metal binding loops III and IV suggests that phosphorylation alters metal ion affinity and inter-subunit interactions. Our studies support a novel mechanism for protein kinase C signal transduction, emphasizing the importance of C-lobe Ca(2+)/Mg(2+)-dependent troponin interactions.
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Affiliation(s)
- Natosha L Finley
- Department of Molecular Genetics, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267-0524, USA
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Davis JP, Rall JA, Reiser PJ, Smillie LB, Tikunova SB. Engineering competitive magnesium binding into the first EF-hand of skeletal troponin C. J Biol Chem 2002; 277:49716-26. [PMID: 12397067 DOI: 10.1074/jbc.m208488200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The goal of this study was to examine the mechanism of magnesium binding to the regulatory domain of skeletal troponin C (TnC). The fluorescence of Trp(29), immediately preceding the first calcium-binding loop in TnC(F29W), was unchanged by addition of magnesium, but increased upon calcium binding with an affinity of 3.3 microm. However, the calcium-dependent increase in TnC(F29W) fluorescence could be reversed by addition of magnesium, with a calculated competitive magnesium affinity of 2.2 mm. When a Z acid pair was introduced into the first EF-hand of TnC(F29W), the fluorescence of G34DTnC(F29W) increased upon addition of magnesium or calcium with affinities of 295 and 1.9 microm, respectively. Addition of 3 mm magnesium decreased the calcium sensitivity of TnC(F29W) and G34DTnC(F29W) approximately 2- and 6-fold, respectively. Exchange of G34DTnC(F29W) into skinned psoas muscle fibers decreased fiber calcium sensitivity approximately 1.7-fold compared with TnC(F29W) at 1 mm [magnesium](free) and approximately 3.2-fold at 3 mm [magnesium](free). Thus, incorporation of a Z acid pair into the first EF-hand allows it to bind magnesium with high affinity. Furthermore, the data suggests that the second EF-hand, but not the first, of TnC is responsible for the competitive magnesium binding to the regulatory domain.
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Affiliation(s)
- Jonathan P Davis
- Departments of Physiology and Cell Biology, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
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