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Yang Z, Marston SB, Gould IR. Modulation of Structure and Dynamics of Cardiac Troponin by Phosphorylation and Mutations Revealed by Molecular Dynamics Simulations. J Phys Chem B 2023; 127:8736-8748. [PMID: 37791815 PMCID: PMC10591477 DOI: 10.1021/acs.jpcb.3c02337] [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] [Received: 04/07/2023] [Revised: 09/08/2023] [Indexed: 10/05/2023]
Abstract
Adrenaline acts on β1 receptors in the heart muscle to enhance contractility, increase the heart rate, and increase the rate of relaxation (lusitropy) via activation of the cyclic AMP-dependent protein kinase, PKA. Phosphorylation of serines 22 and 23 in the N-terminal peptide of cardiac troponin I is responsible for lusitropy. Mutations associated with cardiomyopathy suppress the phosphorylation-dependent change. Key parts of troponin responsible for this modulatory system are disordered and cannot be resolved by conventional structural approaches. We performed all-atom molecular dynamics simulations (5 × 1.5 μs runs) of the troponin core (419 amino acids) in the presence of Ca2+ in the bisphosphorylated and unphosphorylated states for both wild-type troponin and the troponin C (cTnC) G159D mutant. PKA phosphorylation affects troponin dynamics. There is significant rigidification of the structure involving rearrangement of the cTnI(1-33)-cTnC interaction and changes in the distribution of the cTnC helix A/B angle, troponin I (cTnI) switch peptide (149-164) docking, and the angle between the regulatory head and ITC arm domains. The familial dilated cardiomyopathy cTnC G159D mutation whose Ca2+ sensitivity is not modulated by cTnI phosphorylation exhibits a structure inherently more rigid than the wild type, with phosphorylation reversing the direction of all metrics relative to the wild type.
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Affiliation(s)
- Zeyu Yang
- Department
of Chemistry, Molecular Sciences Research Hub, Imperial College London, Shepherd’s Bush, London W12 0BZ, U.K.
- Institute
of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, Shepherd’s Bush, London W12 0BZ, U.K.
| | - Steven B. Marston
- National
Heart & Lung Institute, Imperial College
London, London W12 0NN, U.K.
| | - Ian R. Gould
- Department
of Chemistry, Molecular Sciences Research Hub, Imperial College London, Shepherd’s Bush, London W12 0BZ, U.K.
- Institute
of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, Shepherd’s Bush, London W12 0BZ, U.K.
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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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Pavadai E, Rynkiewicz MJ, Yang Z, Gould IR, Marston SB, Lehman W. Modulation of cardiac thin filament structure by phosphorylated troponin-I analyzed by protein-protein docking and molecular dynamics simulation. Arch Biochem Biophys 2022; 725:109282. [PMID: 35577070 PMCID: PMC10680062 DOI: 10.1016/j.abb.2022.109282] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/14/2022] [Accepted: 05/04/2022] [Indexed: 12/16/2022]
Abstract
Tropomyosin, controlled by troponin-linked Ca2+-binding, regulates muscle contraction by a macromolecular scale steric-mechanism that governs myosin-crossbridge-actin interactions. At low-Ca2+, C-terminal domains of troponin-I (TnI) trap tropomyosin in a position on thin filaments that interferes with myosin-binding, thus causing muscle relaxation. Steric inhibition is reversed at high-Ca2+ when TnI releases from F-actin-tropomyosin as Ca2+ and the TnI switch-peptide bind to the N-lobe of troponin-C (TnC). The opposite end of cardiac TnI contains a phosphorylation-sensitive ∼30 residue-long N-terminal peptide that is absent in skeletal muscle, and likely modifies these interactions in hearts. Here, PKA-dependent phosphorylation of serine 23 and 24 modulates Ca2+ and possibly switch-peptide binding to TnC, causing faster relaxation during the cardiac-cycle (lusitropy). The cardiac-specific N-terminal TnI domain is not captured in crystal structures of troponin or in cryo-EM reconstructions of thin filaments; thus, its global impact on thin filament structure and function is uncertain. Here, we used protein-protein docking and molecular dynamics simulation-based protocols to build a troponin model that was guided by and hence consistent with the recent seminal Yamada structure of Ca2+-activated thin filaments. We find that when present on thin filaments, phosphorylated Ser23/24 along with adjacent polar TnI residues interact closely with both tropomyosin and the N-lobe of TnC during our simulations. These interactions would likely bias tropomyosin to an off-state positioning on actin. In situ, such enhanced relaxation kinetics would promote cardiac lusitropy.
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Affiliation(s)
- Elumalai Pavadai
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA, 02118, USA
| | - Michael J Rynkiewicz
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA, 02118, USA
| | - Zeyu Yang
- Department of Chemistry and Institute of Chemical Biology, Imperial College London, Shepard's Bush, London, W12 0BZ, UK
| | - Ian R Gould
- Department of Chemistry and Institute of Chemical Biology, Imperial College London, Shepard's Bush, London, W12 0BZ, UK
| | - Steven B Marston
- National Heart & Lung Institute, Imperial College London, Dovehouse Street, W12 0NN, UK
| | - William Lehman
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA, 02118, USA.
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Kachooei E, Cordina NM, Potluri PR, Guse JA, McCamey D, Brown LJ. Phosphorylation of Troponin I finely controls the positioning of Troponin for the optimal regulation of cardiac muscle contraction. J Mol Cell Cardiol 2020; 150:44-53. [PMID: 33080242 DOI: 10.1016/j.yjmcc.2020.10.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 09/22/2020] [Accepted: 10/14/2020] [Indexed: 12/01/2022]
Abstract
Troponin is the Ca2+ molecular switch that regulates striated muscle contraction. In the heart, troponin Ca2+ sensitivity is also modulated by the PKA-dependent phosphorylation of a unique 31-residue N-terminal extension region of the Troponin I subunit (NH2-TnI). However, the detailed mechanism for the propagation of the phosphorylation signal through Tn, which results in the enhancement of the myocardial relaxation rate, is difficult to examine within whole Tn. Several models exist for how phosphorylation modulates the troponin response in cardiac cells but these are mostly built from peptide-NMR studies and molecular dynamics simulations. Here we used a paramagnetic spin labeling approach to position and track the movement of the NH2-TnI region within whole Tn. Through paramagnetic relaxation enhancement (PRE)-NMR experiments, we show that the NH2-TnI region interacts with a broad surface area on the N-domain of the Troponin C subunit. This region includes the Ca2+ regulatory Site II and the TnI switch-binding site. Phosphorylation of the NH2-TnI both weakens and shifts this region to an adjacent site on TnC. Interspin EPR distances between NH2-TnI and TnC further reveal a phosphorylation induced re-orientation of the TnC N-domain under saturating Ca2+ conditions. We propose an allosteric model where phosphorylation triggered cooperative changes in both the interaction of the NH2-TnI region with TnC, and the re-orientation of the TnC interdomain orientation, together promote the release of the TnI switch-peptide. Enhancement of the myocardial relaxation rate then occurs. Knowledge of this unique role of phosphorylation in whole Tn is important for understanding pathological processes affecting the heart.
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Affiliation(s)
- Ehsan Kachooei
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Nicole M Cordina
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Phani R Potluri
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Joanna A Guse
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Dane McCamey
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Louise J Brown
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia.
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Bowman JD, Lindert S. Computational Studies of Cardiac and Skeletal Troponin. Front Mol Biosci 2019; 6:68. [PMID: 31448287 PMCID: PMC6696891 DOI: 10.3389/fmolb.2019.00068] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 07/25/2019] [Indexed: 12/16/2022] Open
Abstract
Troponin is a key regulatory protein in muscle contraction, consisting of three subunits troponin C (TnC), troponin I (TnI), and troponin T (TnT). Calcium association to TnC initiates contraction by causing a series of dynamic and conformational changes that allow the switch peptide of TnI to bind and subsequently cross bridges to form between the thin and thick filament of the sarcomere. Owing to its pivotal role in contraction regulation, troponin has been the focus of numerous computational studies over the last decade. These studies elegantly supplemented a large volume of experimental work and focused on the structure, dynamics and function of the whole troponin complex, individual subunits, and even on segments of the thin filament. Molecular dynamics, Brownian dynamics, and free energy simulations have been used to elucidate the conformational dynamics and underlying free energy landscape of troponin, calcium, and switch peptide binding, as well as the effect of disease mutations, small molecules and post-translational modifications such as phosphorylation. Frequently, simulations have been used to confirm or explain experimental observations. Computer-aided drug discovery tools have been employed to identify novel potential calcium sensitizing agents binding to the TnC-TnI interface. Finally, Markov modeling has contributed to simulating contraction within the sarcomere on the mesoscale. Here we are reviewing and classifying the existing computational work on troponin and its subunits, outline current gaps in simulations elucidating troponin's role in contraction and suggest potential future developments in the field.
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Affiliation(s)
- Jacob D Bowman
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, United States
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, United States
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Marston S, Zamora JE. Troponin structure and function: a view of recent progress. J Muscle Res Cell Motil 2019; 41:71-89. [PMID: 31030382 PMCID: PMC7109197 DOI: 10.1007/s10974-019-09513-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 04/12/2019] [Indexed: 12/15/2022]
Abstract
The molecular mechanism by which Ca2+ binding and phosphorylation regulate muscle contraction through Troponin is not yet fully understood. Revealing the differences between the relaxed and active structure of cTn, as well as the conformational changes that follow phosphorylation has remained a challenge for structural biologists over the years. Here we review the current understanding of how Ca2+, phosphorylation and disease-causing mutations affect the structure and dynamics of troponin to regulate the thin filament based on electron microscopy, X-ray diffraction, NMR and molecular dynamics methodologies.
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Affiliation(s)
- Steven Marston
- NHLI and Chemistry Departments, Imperial College London, W12 0NN, London, UK.
| | - Juan Eiros Zamora
- NHLI and Chemistry Departments, Imperial College London, W12 0NN, London, UK
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Bowman JD, Lindert S. Molecular Dynamics and Umbrella Sampling Simulations Elucidate Differences in Troponin C Isoform and Mutant Hydrophobic Patch Exposure. J Phys Chem B 2018; 122:7874-7883. [PMID: 30070845 DOI: 10.1021/acs.jpcb.8b05435] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Troponin C (TnC) facilitates muscle contraction through calcium-binding within its N-terminal region (NTnC). As previously observed using molecular dynamics (MD) simulations, this calcium-binding event leads to an increase in the dynamics of helices lining a hydrophobic patch on TnC. Simulation times of multiple microseconds were required to even see a partial opening of the hydrophobic patch, limiting the ability to thoroughly and quantitatively investigate these rare events. Here we describe the application of umbrella sampling to probe the TnC hydrophobic patch opening in a more targeted and quantitative fashion. Umbrella sampling was utilized to investigate the differences in the free energy of opening between cardiac (cTnC) and fast skeletal TnC (sTnC). We found that, in agreement with previous reports, holo (calcium-bound) sTnC had a lower free energy of opening compared with holo cTnC. Additionally, differences in the free energy of opening of hypertrophic (HCM) and dilated cardiomyopathy (DCM) cTnC systems were investigated. MD simulations and umbrella sampling revealed a lower free energy of opening for the HCM mutations A8V and A31S, as well as the calcium-sensitizing mutation L48Q. The DCM mutations, Y5H, Q50R, and E59D/D75Y, all exhibited a higher free energy of opening. An umbrella sampling simulation of cTnI-bound holo cTnC exhibited the lowest free energy in the open configuration, in agreement with experimental data. In conclusion, this study presents a novel and successful protocol for applying umbrella sampling simulations to quantitatively study the molecular basis of muscle contraction and proposes a mechanism by which HCM and DCM-associated mutations influence contraction.
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Affiliation(s)
- Jacob D Bowman
- Department of Chemistry and Biochemistry , Ohio State University , Columbus , Ohio 43210 , United States
| | - Steffen Lindert
- Department of Chemistry and Biochemistry , Ohio State University , Columbus , Ohio 43210 , United States
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Abstract
This article focuses on three "bins" that comprise sets of biophysical derangements elicited by cardiomyopathy-associated mutations in the myofilament. Current therapies focus on symptom palliation and do not address the disease at its core. We and others have proposed that a more nuanced classification could lead to direct interventions based on early dysregulation changing the trajectory of disease progression in the preclinical cohort. Continued research is necessary to address the complexity of cardiomyopathic progression and develop efficacious therapeutics.
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Affiliation(s)
- Melissa L Lynn
- Department of Medicine, University of Arizona, Room 317, 1656 East Mabel Street, Tucson, AZ 85724, USA
| | - Sarah J Lehman
- Department of Physiological Sciences, University of Arizona, Room 317, 1656 East Mabel Street, Tucson, AZ 85724, USA
| | - Jil C Tardiff
- Department of Medicine, University of Arizona, Room 312, 1656 East Mabel Street, Tucson, AZ 85724, USA.
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Sheehan A, Messer AE, Papadaki M, Choudhry A, Kren V, Biedermann D, Blagg B, Khandelwal A, Marston SB. Molecular Defects in Cardiac Myofilament Ca 2+-Regulation Due to Cardiomyopathy-Linked Mutations Can Be Reversed by Small Molecules Binding to Troponin. Front Physiol 2018; 9:243. [PMID: 29636697 PMCID: PMC5881522 DOI: 10.3389/fphys.2018.00243] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 03/06/2018] [Indexed: 12/28/2022] Open
Abstract
The inherited cardiomyopathies, hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are relatively common, potentially life-threatening and currently untreatable. Mutations are often in the contractile proteins of cardiac muscle and cause abnormal Ca2+ regulation via troponin. HCM is usually linked to higher myofilament Ca2+-sensitivity whilst in both HCM and DCM mutant tissue there is often an uncoupling of the relationship between troponin I (TnI) phosphorylation by PKA and modulation of myofilament Ca2+-sensitivity, essential for normal responses to adrenaline. The adrenergic response is blunted, and this may predispose the heart to failure under stress. At present there are no compounds or interventions that can prevent or treat sarcomere cardiomyopathies. There is a need for novel therapies that act at a more fundamental level to affect the disease process. We demonstrated that epigallocatechin-3 gallate (EGCG) was found to be capable of restoring the coupled relationship between Ca2+-sensitivity and TnI phosphorylation in mutant thin filaments to normal in vitro, independent of the mutation (15 mutations tested). We have labeled this property "re-coupling." The action of EGCG in vitro to reverse the abnormality caused by myopathic mutations would appear to be an ideal pharmaceutical profile for treatment of inherited HCM and DCM but EGCG is known to be promiscuous in vivo and is thus unsuitable as a therapeutic drug. We therefore investigated whether other structurally related compounds can re-couple myofilaments without these off-target effects. We used the quantitative in vitro motility assay to screen 40 compounds, related to C-terminal Hsp90 inhibitors, and found 23 that can re-couple mutant myofilaments. There is no correlation between re-couplers and Hsp90 inhibitors. The Ca2+-sensitivity shift due to TnI phosphorylation was restored to 2.2 ± 0.01-fold (n = 19) compared to 2.0 ± 0.24-fold (n = 7) in wild-type thin filaments. Many of these compounds were either pure re-couplers or pure desensitizers, indicating these properties are independent; moreover, re-coupling ability could be lost with small changes of compound structure, indicating the possibility of specificity. Small molecules that can re-couple may have therapeutic potential. HIGHLIGHTS - Inherited cardiomyopathies are common diseases that are currently untreatable at a fundamental level and therefore finding a small molecule treatment is highly desirable.- We have identified a molecular level dysfunction common to nearly all mutations: uncoupling of the relationship between troponin I phosphorylation and modulation of myofilament Ca2+-sensitivity, essential for normal responses to adrenaline.- We have identified a new class of drugs that are capable of both reducing Ca2+-sensitivity and/or recouping the relationship between troponin I phosphorylation and Ca2+-sensitivity.- The re-coupling phenomenon can be explained on the basis of a single mechanism that is testable.- Measurements with a wide range of small molecules of varying structures can indicate the critical molecular features required for recoupling and allows the prediction of other potential re-couplers.
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Affiliation(s)
- Alice Sheehan
- NHLI, Imperial College London, London, United Kingdom
| | | | | | | | - Vladimír Kren
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - David Biedermann
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Brian Blagg
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, United States
| | - Anuj Khandelwal
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, United States
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