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Zhu L, Landim-Vieira M, Garcia MR, Pinto JR, Chalovich JM. Negative Charges Introduced Near the IT Helix of Cardiac Troponin T Stabilize the Active State of Actin Filaments. Biochemistry 2023; 62:2137-2146. [PMID: 37379571 PMCID: PMC10576618 DOI: 10.1021/acs.biochem.3c00279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
The disordered and basic C-terminal 14 residues of human troponin T (TnT) are essential for full inhibition of actomyosin ATPase activity at low Ca2+ levels and for limiting activation at saturating Ca2+. In previous studies, stepwise truncation of the C-terminal region of TnT increased activity in proportion to the number of positive charges eliminated. To define key basic residues more closely, we generated phosphomimetic-like mutants of TnT. Phosphomimetic mutants were chosen because of reports that phosphorylation of TnT, including sites within the C terminal region, depressed activity, contrary to our expectations. Four constructs were made where one or more Ser and Thr residues were replaced with Asp residues. The S275D and T277D mutants, near the IT helix and adjacent to basic residues, produced the greatest activation of ATPase rates in solution; the effects of the S275D mutant were recapitulated in muscle fiber preparations with enhanced myofilament Ca2+ sensitivity. Actin filaments containing S275D TnT were also shown to be incapable of populating the inactive state at low Ca2+ levels. Actin filaments containing both S275D/T284D were not statistically different from those containing only S275D in both solution and cardiac muscle preparation studies. Finally, actin filaments containing T284D TnT, closer to the C-terminus and not adjacent to a basic residue, had the smallest effect on activity. Thus, the effects of negative charge placement in the C-terminal region of TnT were greatest near the IT helix and adjacent to a basic residue.
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Affiliation(s)
- Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, United States
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Michelle Rodriguez Garcia
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32304, United States
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, United States
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2
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A comprehensive guide to genetic variants and post-translational modifications of cardiac troponin C. J Muscle Res Cell Motil 2020; 42:323-342. [PMID: 33179204 DOI: 10.1007/s10974-020-09592-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 10/24/2020] [Indexed: 02/07/2023]
Abstract
Familial cardiomyopathy is an inherited disease that affects the structure and function of heart muscle and has an extreme range of phenotypes. Among the millions of affected individuals, patients with hypertrophic (HCM), dilated (DCM), or left ventricular non-compaction (LVNC) cardiomyopathy can experience morphologic changes of the heart which lead to sudden death in the most detrimental cases. TNNC1, the gene that codes for cardiac troponin C (cTnC), is a sarcomere gene associated with cardiomyopathies in which probands exhibit young age of presentation and high death, transplant or ventricular fibrillation events relative to TNNT2 and TNNI3 probands. Using GnomAD, ClinVar, UniProt and PhosphoSitePlus databases and published literature, an extensive list to date of identified genetic variants in TNNC1 and post-translational modifications (PTMs) in cTnC was compiled. Additionally, a recent cryo-EM structure of the cardiac thin filament regulatory unit was used to localize each functionally studied amino acid variant and each PTM (acetylation, glycation, s-nitrosylation, phosphorylation) in the structure of cTnC. TNNC1 has a large number of variants (> 100) relative to other genes of the same transcript size. Surprisingly, the mapped variant amino acids and PTMs are distributed throughout the cTnC structure. While many cardiomyopathy-associated variants are localized in α-helical regions of cTnC, this was not statistically significant χ2 (p = 0.72). Exploring the variants in TNNC1 and PTMs of cTnC in the contexts of cardiomyopathy association, physiological modulation and potential non-canonical roles provides insights into the normal function of cTnC along with the many facets of TNNC1 as a cardiomyopathic gene.
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3
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van der Velden J, Stienen GJM. Cardiac Disorders and Pathophysiology of Sarcomeric Proteins. Physiol Rev 2019; 99:381-426. [PMID: 30379622 DOI: 10.1152/physrev.00040.2017] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.
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Affiliation(s)
- Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Ger J M Stienen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
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Ly T, Pappas CT, Johnson D, Schlecht W, Colpan M, Galkin VE, Gregorio CC, Dong WJ, Kostyukova AS. Effects of cardiomyopathy-linked mutations K15N and R21H in tropomyosin on thin-filament regulation and pointed-end dynamics. Mol Biol Cell 2018; 30:268-281. [PMID: 30462572 PMCID: PMC6589558 DOI: 10.1091/mbc.e18-06-0406] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Missense mutations K15N and R21H in striated muscle tropomyosin are linked to dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), respectively. Tropomyosin, together with the troponin complex, regulates muscle contraction and, along with tropomodulin and leiomodin, controls the uniform thin-filament lengths crucial for normal sarcomere structure and function. We used Förster resonance energy transfer to study effects of the tropomyosin mutations on the structure and kinetics of the cardiac troponin core domain associated with the Ca2+-dependent regulation of cardiac thin filaments. We found that the K15N mutation desensitizes thin filaments to Ca2+ and slows the kinetics of structural changes in troponin induced by Ca2+ dissociation from troponin, while the R21H mutation has almost no effect on these parameters. Expression of the K15N mutant in cardiomyocytes decreases leiomodin’s thin-filament pointed-end assembly but does not affect tropomodulin’s assembly at the pointed end. Our in vitro assays show that the R21H mutation causes a twofold decrease in tropomyosin’s affinity for F-actin and affects leiomodin’s function. We suggest that the K15N mutation causes DCM by altering Ca2+-dependent thin-filament regulation and that one of the possible HCM-causing mechanisms by the R21H mutation is through alteration of leiomodin’s function.
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Affiliation(s)
- Thu Ly
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164
| | - Christopher T Pappas
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721
| | - Dylan Johnson
- Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, NC 27834
| | - William Schlecht
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164.,Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164
| | - Mert Colpan
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721
| | - Vitold E Galkin
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721
| | - Wen-Ji Dong
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164.,Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164
| | - Alla S Kostyukova
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164
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5
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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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Schlecht W, Dong WJ. Dynamic Equilibrium of Cardiac Troponin C's Hydrophobic Cleft and Its Modulation by Ca 2+ Sensitizers and a Ca 2+ Sensitivity Blunting Phosphomimic, cTnT(T204E). Bioconjug Chem 2017; 28:2581-2590. [PMID: 28876897 DOI: 10.1021/acs.bioconjchem.7b00418] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several studies have suggested that conformational dynamics are important in the regulation of thin filament activation in cardiac troponin C (cTnC); however, little direct evidence has been offered to support these claims. In this study, a dye homodimerization approach is developed and implemented that allows the determination of the dynamic equilibrium between open and closed conformations in cTnC's hydrophobic cleft. Modulation of this equilibrium by Ca2+, cardiac troponin I (cTnI), cardiac troponin T (cTnT), Ca2+-sensitizers, and a Ca2+-desensitizing phosphomimic of cTnT (cTnT(T204E) is characterized. Isolated cTnC contained a small open conformation population in the absence of Ca2+ that increased significantly upon the addition of saturating levels of Ca2+. This suggests that the Ca2+-induced activation of thin filament arises from an increase in the probability of hydrophobic cleft opening. The inclusion of cTnI increased the population of open cTnC, and the inclusion of cTnT had the opposite effect. Samples containing Ca2+-desensitizing cTnT(T204E) showed a slight but insignificant decrease in open conformation probability compared to samples with cardiac troponin T, wild type [cTnT(wt)], while Ca2+ sensitizer treated samples generally increased open conformation probability. These findings show that an equilibrium between the open and closed conformations of cTnC's hydrophobic cleft play a significant role in tuning the Ca2+ sensitivity of the heart.
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Affiliation(s)
- William Schlecht
- The Voiland School of Chemical Engineering and Bioengineering and ‡The Department of Integrated Neuroscience and Physiology, Washington State University , Pullman, Washington 99164, United States
| | - Wen-Ji Dong
- The Voiland School of Chemical Engineering and Bioengineering and ‡The Department of Integrated Neuroscience and Physiology, Washington State University , Pullman, Washington 99164, United States
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McConnell M, Tal Grinspan L, Williams MR, Lynn ML, Schwartz BA, Fass OZ, Schwartz SD, Tardiff JC. Clinically Divergent Mutation Effects on the Structure and Function of the Human Cardiac Tropomyosin Overlap. Biochemistry 2017; 56:3403-3413. [PMID: 28603979 DOI: 10.1021/acs.biochem.7b00266] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The progression of genetically inherited cardiomyopathies from an altered protein structure to clinical presentation of disease is not well understood. One of the main roadblocks to mechanistic insight remains a lack of high-resolution structural information about multiprotein complexes within the cardiac sarcomere. One example is the tropomyosin (Tm) overlap region of the thin filament that is crucial for the function of the cardiac sarcomere. To address this central question, we devised coupled experimental and computational modalities to characterize the baseline function and structure of the Tm overlap, as well as the effects of mutations causing divergent patterns of ventricular remodeling on both structure and function. Because the Tm overlap contributes to the cooperativity of myofilament activation, we hypothesized that mutations that enhance the interactions between overlap proteins result in more cooperativity, and conversely, those that weaken interaction between these elements lower cooperativity. Our results suggest that the Tm overlap region is affected differentially by dilated cardiomyopathy-associated Tm D230N and hypertrophic cardiomyopathy-associated human cardiac troponin T (cTnT) R92L. The Tm D230N mutation compacts the Tm overlap region, increasing the cooperativity of the Tm filament, contributing to a dilated cardiomyopathy phenotype. The cTnT R92L mutation causes weakened interactions closer to the N-terminal end of the overlap, resulting in decreased cooperativity. These studies demonstrate that mutations with differential phenotypes exert opposite effects on the Tm-Tn overlap, and that these effects can be directly correlated to a molecular level understanding of the structure and dynamics of the component proteins.
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Affiliation(s)
- Mark McConnell
- Department of Biomedical Engineering, University of Arizona , Tucson, Arizona 85721, United States
| | - Lauren Tal Grinspan
- Department of Medicine, Columbia University Medical Center , New York, New York 10032, United States
| | - Michael R Williams
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Melissa L Lynn
- Department of Physiological Sciences, University of Arizona , Tucson, Arizona 85724, United States
| | - Benjamin A Schwartz
- Graduate Interdisciplinary Program in Neuroscience, University of Arizona , Tucson, Arizona 85721, United States
| | - Ofer Z Fass
- Department of Physiological Sciences, University of Arizona , Tucson, Arizona 85724, 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.,Department of Physiological Sciences, University of Arizona , Tucson, Arizona 85724, United States.,Department of Medicine, University of Arizona , Tucson, Arizona 85724, United States
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8
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Michael JJ, Gollapudi SK, Chandra M. Interplay between the effects of a Protein Kinase C phosphomimic (T204E) and a dilated cardiomyopathy mutation (K211Δ or R206W) in rat cardiac troponin T blunts the magnitude of muscle length-mediated crossbridge recruitment against the β-myosin heavy chain background. J Muscle Res Cell Motil 2016; 37:83-93. [PMID: 27411801 DOI: 10.1007/s10974-016-9448-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 07/05/2016] [Indexed: 11/26/2022]
Abstract
Failing hearts of dilated cardiomyopathy (DCM)-patients reveal systolic dysfunction and upregulation of several Protein Kinase C (PKC) isoforms. Recently, we demonstrated that the functional effects of T204E, a PKC phosphomimic of cardiac troponin T (TnT), were differently modulated by α- and β-myosin heavy chain (MHC) isoforms. Therefore, we hypothesized that the interplay between the effects of T204E and a DCM-linked mutation (K211Δ or R206W) in TnT would modulate contractile parameters linked-to systolic function in an MHC-dependent manner. To test our hypothesis, five TnT variants (wildtype, K211Δ, K211Δ + T204E, R206W, and R206W + T204E) were generated and individually reconstituted into demembranated cardiac muscle fibers from normal (α-MHC) and propylthiouracil-treated (β-MHC) rats. Steady-state and mechano-dynamic measurements were performed on reconstituted fibers. Myofilament Ca(2+) sensitivity (pCa50) was decreased by both K211Δ and R206W to a greater extent in α-MHC fibers (~0.15 pCa units) than in β-MHC fibers (~0.06 pCa units). However, T204E exacerbated the attenuating influence of both mutants on pCa50 only in β-MHC fibers. Moreover, the magnitude of muscle length (ML)-mediated crossbridge (XB) recruitment was decreased by K211Δ + T204E (~47 %), R206W (~34 %), and R206W + T204E (~36 %) only in β-MHC fibers. In relevance to human hearts, which predominantly express β-MHC, our data suggest that the interplay between the effects of DCM mutations, PKC phosphomimic in TnT, and β-MHC lead to systolic dysfunction by attenuating pCa50 and the magnitude of ML-mediated XB recruitment.
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Affiliation(s)
- John Jeshurun Michael
- Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA
| | - Sampath K Gollapudi
- Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA.
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Michael JJ, Chandra M. Interplay Between the Effects of Dilated Cardiomyopathy Mutation (R206L) and the Protein Kinase C Phosphomimic (T204E) of Rat Cardiac Troponin T Are Differently Modulated by α- and β-Myosin Heavy Chain Isoforms. J Am Heart Assoc 2016; 5:e002777. [PMID: 27001966 PMCID: PMC4943253 DOI: 10.1161/jaha.115.002777] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background We hypothesized that the functional effects of R206L—a rat analog of the dilated cardiomyopathy (DCM) mutation R205L in human cardiac troponin T (TnT)—were differently modulated by myosin heavy chain (MHC) isoforms and T204E, a protein kinase C (PKC) phosphomimic of TnT. Our hypothesis was based on two observations: (1) α‐ and β‐MHC differentially influence the functional effects of TnT; and (2) PKC isoforms capable of phosphorylating TnT are upregulated in failing human hearts. Methods and Results We generated 4 recombinant TnT variants: wild type; R206L; T204E; and R206L+T204E. Functional effects of the TnT variants were tested in cardiac muscle fibers (minimum 14 per group) from normal (α‐MHC) and propylthiouracil‐treated rats (β‐MHC) using steady‐state and dynamic contractile measurements. Notably, in α‐MHC fibers, Ca2+‐activated maximal tension was attenuated by R206L (≈32%), T204E (≈63%), and R206L+T204E (≈64%). In β‐MHC fibers, maximal tension was unaffected by R206L, but was attenuated by T204E (≈33%) and R206L+T204E (≈40%). Thus, β‐MHC differentially counteracted the attenuating effects of the TnT variants on tension. However, in β‐MHC fibers, R206L+T204E attenuated tension to a greater extent when compared to T204E alone. In β‐MHC fibers, R206L+T204E attenuated the magnitude of the length‐mediated recruitment of new cross‐bridges (≈28%), suggesting that the Frank‐Starling mechanism was impaired. Conclusions Our findings are the first (to our knowledge) to demonstrate that the functional effects of a DCM‐linked TnT mutation are not only modulated by MHC isoforms, but also by the pathology‐associated post‐translational modifications of TnT.
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Affiliation(s)
- John Jeshurun Michael
- Department of Integrative Physiology and Neuroscience Washington State University, Pullman, WA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience Washington State University, Pullman, WA
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Schlecht W, Li KL, Hu D, Dong W. Fluorescence Based Characterization of Calcium Sensitizer Action on the Troponin Complex. Chem Biol Drug Des 2015; 87:171-81. [PMID: 26375298 DOI: 10.1111/cbdd.12651] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/15/2015] [Accepted: 08/05/2015] [Indexed: 11/29/2022]
Abstract
Calcium sensitizers enhance the transduction of the Ca(2+) signal into force within the heart and have found use in treating heart failure. However the mechanisms of action for most Ca(2+) sensitizers remain unclear. To address this issue an efficient fluorescence based approach to Ca(2+) sensitizer screening was developed which monitors cardiac troponin C's (cTnC's) hydrophobic cleft. This approach was tested on four common Ca(2+) -sensitizers, EMD 57033, levosimendan, bepridil and pimobendan with the aim of elucidating the mechanisms of action for each as well as proving the efficacy of the new screening method. Ca(2+) -titration experiments were employed to determine the effect on Ca(2+) sensitivity and cooperativity of cTnC opening, while stopped flow experiments were used to investigate the impact on cTnC relaxation kinetics. Bepridil was shown to increase the sensitivity of cTnC for Ca(2+) under all reconstitution conditions, sensitization by the other drugs was context dependent. Levosimendan and pimobendan reduced the rate of cTnC closing consistent with a stabilization of cTnC's open conformation while bepridil increased the rate of relaxation. Experiments were also run on samples containing cTnT(T204E), a known Ca(2+) -desensitizing phosphorylation mimic. Levosimendan, bepridil, and pimobendan were found to elevate the Ca(2+) -sensitivity of cTnT(T204E) containing samples in this context.
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Affiliation(s)
- William Schlecht
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, PO Box 646515, Washington State University, Pullman, WA 99164-6515, USA
| | - King-Lun Li
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, PO Box 646515, Washington State University, Pullman, WA 99164-6515, USA
| | - Dehong Hu
- The Environmental and Molecular Science Laboratory, Pacific Northwest National Laboratory, 3335 Innovation Boulevard Richland, WA 99354, USA
| | - Wenji Dong
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, PO Box 646515, Washington State University, Pullman, WA 99164-6515, USA
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Stienen GJM. Pathomechanisms in heart failure: the contractile connection. J Muscle Res Cell Motil 2014; 36:47-60. [PMID: 25376563 DOI: 10.1007/s10974-014-9395-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Accepted: 10/20/2014] [Indexed: 01/07/2023]
Abstract
Heart failure is a multi-factorial progressive disease in which eventually the contractile performance of the heart is insufficient to meet the demands of the body, even at rest. A distinction can be made on the basis of the cause of the disease in genetic and acquired heart failure and at the functional level between systolic and diastolic heart failure. Here the basic determinants of contractile function of myocardial cells will be reviewed and an attempt will be made to elucidate their role in the development of heart failure. The following topics are addressed: the tension generating capacity, passive tension, the rate of tension development, the rate of ATP utilisation, calcium sensitivity of tension development, phosphorylation of contractile proteins, length dependent activation and stretch activation. The reduction in contractile performance during systole can be attributed predominantly to a loss of cardiomyocytes (necrosis), myocyte disarray and a decrease in myofibrillar density all resulting in a reduction in the tension generating capacity and likely also to a mismatch between energy supply and demand of the myocardium. This leads to a decline in the ejection fraction of the heart. Diastolic dysfunction can be attributed to fibrosis and an increase in titin stiffness which result in an increase in stiffness of the ventricular wall and hampers the filling of the heart with blood during diastole. A large number of post translation modifications of regulatory sarcomeric proteins influence myocardial function by altering calcium sensitivity of tension development. It is still unclear whether in concert these influences are adaptive or maladaptive during the disease process.
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Affiliation(s)
- G J M Stienen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands,
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