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Patel JR, Park KJ, Bradshaw AS, Phan T, Fitzsimons DP. Cooperative mechanisms underlie differences in myocardial contractile dynamics between large and small mammals. J Gen Physiol 2023; 155:e202213315. [PMID: 37725091 PMCID: PMC10509357 DOI: 10.1085/jgp.202213315] [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: 12/14/2022] [Revised: 06/08/2023] [Accepted: 08/29/2023] [Indexed: 09/21/2023] Open
Abstract
Ca2+ binding to troponin C (TnC) and myosin cross-bridge binding to actin act in a synergistic cooperative manner to modulate myocardial contraction and relaxation. The responsiveness of the myocardial thin filament to the activating effects of Ca2+ and myosin cross-bridge binding has been well-characterized in small mammals (e.g., mice). Given the nearly 10-fold difference in resting heart rates and twitch kinetics between small and large mammals, it is unlikely that the cooperative mechanisms underlying thin filament activation are identical in these two species. To test this idea, we measured the Ca2+ dependencies of steady-state force and the rate constant of force redevelopment (ktr) in murine and porcine permeabilized ventricular myocardium. While murine myocardium exhibited a steep activation-dependence of ktr, the activation-dependent profile of ktr was significantly reduced in porcine ventricular myocardium. Further insight was attained by examining force-pCa and ktr-pCa relationships. In the murine myocardium, the pCa50 for ktr was right-shifted compared with the pCa50 for force, meaning that increases in steady-state force occurred well before increases in the rate of force redevelopment were observed. In the porcine myocardium, we observed a tighter coupling of the force-pCa and ktr-pCa relationships, as evidenced by near-maximal rates of force redevelopment at low levels of Ca2+ activation. These results demonstrate that the molecular mechanisms underlying the cooperative activation of force are a dynamic property of the mammalian heart, involving, at least in part, the species- and tissue-specific expression of cardiac myosin heavy chain isoforms.
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Affiliation(s)
- Jitandrakumar R. Patel
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Kayla J.V. Park
- Department of Animal, Veterinary, and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID, USA
| | - Aidan S. Bradshaw
- Department of Animal, Veterinary, and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID, USA
| | - Tuan Phan
- Institute for Modeling Collaboration and Innovation, University of Idaho, Moscow, ID, USA
| | - Daniel P. Fitzsimons
- Department of Animal, Veterinary, and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID, USA
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Matyushenko AM, Nefedova VV, Kochurova AM, Kopylova GV, Koubassova NA, Shestak AG, Yampolskaya DS, Shchepkin DV, Kleymenov SY, Ryabkova NS, Katrukha IA, Bershitsky SY, Zaklyazminskaya EV, Tsaturyan AK, Levitsky DI. Novel Mutation Glu98Lys in Cardiac Tropomyosin Alters Its Structure and Impairs Myocardial Relaxation. Int J Mol Sci 2023; 24:12359. [PMID: 37569730 PMCID: PMC10419091 DOI: 10.3390/ijms241512359] [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: 07/01/2023] [Revised: 07/25/2023] [Accepted: 07/30/2023] [Indexed: 08/13/2023] Open
Abstract
We characterized a novel genetic variant c.292G > A (p.E98K) in the TPM1 gene encoding cardiac tropomyosin 1.1 isoform (Tpm1.1), found in a proband with a phenotype of complex cardiomyopathy with conduction dysfunction and slow progressive neuromuscular involvement. To understand the molecular mechanism by which this mutation impairs cardiac function, we produced recombinant Tpm1.1 carrying an E98K substitution and studied how this substitution affects the structure of the Tpm1.1 molecule and its functional properties. The results showed that the E98K substitution in the N-terminal part of the Tpm molecule significantly destabilizes the C-terminal part of Tpm, thus indicating a long-distance destabilizing effect of the substitution on the Tpm coiled-coil structure. The E98K substitution did not noticeably affect Tpm's affinity for F-actin but significantly impaired Tpm's regulatory properties. It increased the Ca2+ sensitivity of the sliding velocity of regulated thin filaments over cardiac myosin in an in vitro motility assay and caused an incomplete block of the thin filament sliding at low Ca2+ concentrations. The incomplete motility block in the absence of Ca2+ can be explained by the loosening of the Tpm interaction with troponin I (TnI), thus increasing Tpm mobility on the surface of an actin filament that partially unlocks the myosin binding sites. This hypothesis is supported by the molecular dynamics (MD) simulation that showed that the E98 Tpm residue is involved in hydrogen bonding with the C-terminal part of TnI. Thus, the results allowed us to explain the mechanism by which the E98K Tpm mutation impairs sarcomeric function and myocardial relaxation.
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Affiliation(s)
- Alexander M. Matyushenko
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow 119071, Russia; (A.M.M.); (V.V.N.); (D.S.Y.); (S.Y.K.)
| | - Victoria V. Nefedova
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow 119071, Russia; (A.M.M.); (V.V.N.); (D.S.Y.); (S.Y.K.)
| | - Anastasia M. Kochurova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg 620049, Russia; (A.M.K.); (G.V.K.); (D.V.S.); (S.Y.B.)
| | - Galina V. Kopylova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg 620049, Russia; (A.M.K.); (G.V.K.); (D.V.S.); (S.Y.B.)
| | - Natalia A. Koubassova
- Institute of Mechanics, Moscow State University, Moscow 119192, Russia; (N.A.K.); (A.K.T.)
| | - Anna G. Shestak
- Petrovsky National Research Centre of Surgery, Moscow 119991, Russia; (A.G.S.); (E.V.Z.)
| | - Daria S. Yampolskaya
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow 119071, Russia; (A.M.M.); (V.V.N.); (D.S.Y.); (S.Y.K.)
| | - Daniil V. Shchepkin
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg 620049, Russia; (A.M.K.); (G.V.K.); (D.V.S.); (S.Y.B.)
| | - Sergey Y. Kleymenov
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow 119071, Russia; (A.M.M.); (V.V.N.); (D.S.Y.); (S.Y.K.)
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Natalia S. Ryabkova
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia; (N.S.R.); (I.A.K.)
- HyTest Ltd., 20520 Turku, Finland
| | - Ivan A. Katrukha
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia; (N.S.R.); (I.A.K.)
- HyTest Ltd., 20520 Turku, Finland
| | - Sergey Y. Bershitsky
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg 620049, Russia; (A.M.K.); (G.V.K.); (D.V.S.); (S.Y.B.)
| | - Elena V. Zaklyazminskaya
- Petrovsky National Research Centre of Surgery, Moscow 119991, Russia; (A.G.S.); (E.V.Z.)
- N.P. Bochkov Research Centre for Medical Genetics, Moscow 20520, Russia
| | - Andrey K. Tsaturyan
- Institute of Mechanics, Moscow State University, Moscow 119192, Russia; (N.A.K.); (A.K.T.)
| | - Dmitrii I. Levitsky
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow 119071, Russia; (A.M.M.); (V.V.N.); (D.S.Y.); (S.Y.K.)
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3
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De Novo Asp219Val Mutation in Cardiac Tropomyosin Associated with Hypertrophic Cardiomyopathy. Int J Mol Sci 2022; 24:ijms24010018. [PMID: 36613463 PMCID: PMC9820293 DOI: 10.3390/ijms24010018] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/13/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM), caused by mutations in thin filament proteins, manifests as moderate cardiac hypertrophy and is associated with sudden cardiac death (SCD). We identified a new de novo variant, c.656A>T (p.D219V), in the TPM1 gene encoding cardiac tropomyosin 1.1 (Tpm) in a young SCD victim with post-mortem-diagnosed HCM. We produced recombinant D219V Tpm1.1 and studied its structural and functional properties using various biochemical and biophysical methods. The D219V mutation did not affect the Tpm affinity for F-actin but increased the thermal stability of the Tpm molecule and Tpm-F-actin complex. The D219V mutation significantly increased the Ca2+ sensitivity of the sliding velocity of thin filaments over cardiac myosin in an in vitro motility assay and impaired the inhibition of the filament sliding at low Ca2+ concentration. The molecular dynamics (MD) simulation provided insight into a possible molecular mechanism of the effect of the mutation that is most likely a cause of the weakening of the Tpm interaction with actin in the "closed" state and so makes it an easier transition to the “open” state. The changes in the Ca2+ regulation of the actin-myosin interaction characteristic of genetic HCM suggest that the mutation is likely pathogenic.
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Chalovich JM, Zhu L, Johnson D. Hypertrophic Cardiomyopathy Mutations of Troponin Reveal Details of Striated Muscle Regulation. Front Physiol 2022; 13:902079. [PMID: 35694406 PMCID: PMC9178916 DOI: 10.3389/fphys.2022.902079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/05/2022] [Indexed: 11/13/2022] Open
Abstract
Striated muscle contraction is inhibited by the actin associated proteins tropomyosin, troponin T, troponin I and troponin C. Binding of Ca2+ to troponin C relieves this inhibition by changing contacts among the regulatory components and ultimately repositioning tropomyosin on the actin filament creating a state that is permissive for contraction. Several lines of evidence suggest that there are three possible positions of tropomyosin on actin commonly called Blocked, Closed/Calcium and Open or Myosin states. These states are thought to correlate with different functional states of the contractile system: inactive-Ca2+-free, inactive-Ca2+-bound and active. The inactive-Ca2+-free state is highly occupied at low free Ca2+ levels. However, saturating Ca2+ produces a mixture of inactive and active states making study of the individual states difficult. Disease causing mutations of troponin, as well as phosphomimetic mutations change the stabilities of the states of the regulatory complex thus providing tools for studying individual states. Mutants of troponin are available to stabilize each of three structural states. Particular attention is given to the hypertrophic cardiomyopathy causing mutation, Δ14 of TnT, that is missing the last 14 C-terminal residues of cardiac troponin T. Removal of the basic residues in this region eliminates the inactive-Ca2+-free state. The major state occupied with Δ14 TnT at inactivating Ca2+ levels resembles the inactive-Ca2+-bound state in function and in displacement of TnI from actin-tropomyosin. Addition of Ca2+, with Δ14TnT, shifts the equilibrium between the inactive-Ca2+-bound and the active state to favor that latter state. These mutants suggest a unique role for the C-terminal region of Troponin T as a brake to limit Ca2+ activation.
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Parikh J, Rumbell T, Butova X, Myachina T, Acero JC, Khamzin S, Solovyova O, Kozloski J, Khokhlova A, Gurev V. Generative adversarial networks for construction of virtual populations of mechanistic models: simulations to study Omecamtiv Mecarbil action. J Pharmacokinet Pharmacodyn 2021; 49:51-64. [PMID: 34716531 PMCID: PMC8837558 DOI: 10.1007/s10928-021-09787-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 09/23/2021] [Indexed: 11/30/2022]
Abstract
Biophysical models are increasingly used to gain mechanistic insights by fitting and reproducing experimental and clinical data. The inherent variability in the recorded datasets, however, presents a key challenge. In this study, we present a novel approach, which integrates mechanistic modeling and machine learning to analyze in vitro cardiac mechanics data and solve the inverse problem of model parameter inference. We designed a novel generative adversarial network (GAN) and employed it to construct virtual populations of cardiac ventricular myocyte models in order to study the action of Omecamtiv Mecarbil (OM), a positive cardiac inotrope. Populations of models were calibrated from mechanically unloaded myocyte shortening recordings obtained in experiments on rat myocytes in the presence and absence of OM. The GAN was able to infer model parameters while incorporating prior information about which model parameters OM targets. The generated populations of models reproduced variations in myocyte contraction recorded during in vitro experiments and provided improved understanding of OM’s mechanism of action. Inverse mapping of the experimental data using our approach suggests a novel action of OM, whereby it modifies interactions between myosin and tropomyosin proteins. To validate our approach, the inferred model parameters were used to replicate other in vitro experimental protocols, such as skinned preparations demonstrating an increase in calcium sensitivity and a decrease in the Hill coefficient of the force–calcium (F–Ca) curve under OM action. Our approach thereby facilitated the identification of the mechanistic underpinnings of experimental observations and the exploration of different hypotheses regarding variability in this complex biological system.
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Affiliation(s)
| | | | - Xenia Butova
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Tatiana Myachina
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Jorge Corral Acero
- Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Oxford, UK
| | - Svyatoslav Khamzin
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | - Olga Solovyova
- Ural Federal University, Yekaterinburg, Russia.,Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
| | | | - Anastasia Khokhlova
- Ural Federal University, Yekaterinburg, Russia.,Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences (UB RAS), Yekaterinburg, Russia
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6
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Johnson D, Landim-Vieira M, Solı S C, Zhu L, Robinson JM, Pinto JR, Chalovich JM. Eliminating the First Inactive State and Stabilizing the Active State of the Cardiac Regulatory System Alters Behavior in Solution and in Ordered Systems. Biochemistry 2020; 59:3487-3497. [PMID: 32840354 DOI: 10.1021/acs.biochem.0c00430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcium binding to troponin C (TnC) is insufficient for full activation of myosin ATPase activity by actin-tropomyosin-troponin. Previous attempts to investigate full activation utilized ATP-free myosin or chemically modified myosin to stabilize the active state of regulated actin. We utilized the Δ14-TnT and the A8V-TnC mutants to stabilize the activated state at saturating Ca2+ and to eliminate one of the inactive states at low Ca2+. The observed effects differed in solution studies and in the more ordered in vitro motility assay and in skinned cardiac muscle preparations. At saturating Ca2+, full activation with Δ14-TnT·A8V-TnC decreased the apparent KM for actin-activated ATPase activity compared to bare actin filaments. Rates of in vitro motility increased at both high and low Ca2+ with Δ14-TnT; the maximum shortening speed at high Ca2+ increased 1.8-fold. Cardiac muscle preparations exhibited increased Ca2+ sensitivity and large increases in resting force with either Δ14-TnT or Δ14-TnT·A8V-TnC. We also observed a significant increase in the maximal rate of tension redevelopment. The results of full activation with Ca2+ and Δ14-TnT·A8V-TnC confirmed and extended several earlier observations using other means of reaching full activation. Furthermore, at low Ca2+, elimination of the first inactive state led to partial activation. This work also confirms, in three distinct experimental systems, that troponin is able to stabilize the active state of actin-tropomyosin-troponin without the need for high-affinity myosin binding. The results are relevant to the reason for two inactive states and for the role of force producing myosin in regulation.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
| | - Maicon Landim-Vieira
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States
| | - Christopher Solı S
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
| | - Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
| | - John M Robinson
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
| | - Jose R Pinto
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States
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7
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McCabe KJ, Aboelkassem Y, Teitgen AE, Huber GA, McCammon JA, Regnier M, McCulloch AD. Predicting the effects of dATP on cardiac contraction using multiscale modeling of the sarcomere. Arch Biochem Biophys 2020; 695:108582. [PMID: 32956632 DOI: 10.1016/j.abb.2020.108582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/30/2020] [Accepted: 09/04/2020] [Indexed: 11/26/2022]
Abstract
2'-deoxy-ATP (dATP) is a naturally occurring small molecule that has shown promise as a therapeutic because it significantly increases cardiac myocyte force development even at low dATP/ATP ratios. To investigate mechanisms by which dATP alters myosin crossbridge dynamics, we used Brownian dynamics simulations to calculate association rates between actin and ADP- or dADP-bound myosin. These rates were then directly incorporated in a mechanistic Monte Carlo Markov Chain model of cooperative sarcomere contraction. A unique combination of increased powerstroke and detachment rates was required to match experimental steady-state and kinetic data for dATP force production in rat cardiac myocytes when the myosin attachment rate in the model was constrained by the results of a Brownian dynamics simulation. Nearest-neighbor cooperativity was seen to contribute to, but not fully explain, the steep relationship between dATP/ATP ratio and steady-state force-development observed at lower dATP concentrations. Dynamic twitch simulations performed using measured calcium transients as inputs showed that the effects of dATP on the crossbridge alone were not sufficient to explain experimentally observed enhancement of relaxation kinetics by dATP treatment. Hence, dATP may also affect calcium handling even at low concentrations. By enabling the effects of dATP on sarcomere mechanics to be predicted, this multi-scale modeling framework may elucidate the molecular mechanisms by which dATP can have therapeutic effects on cardiac contractile dysfunction.
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Affiliation(s)
- Kimberly J McCabe
- Simula Research Laboratory, Department of Computational Physiology, PO Box 134, 1325, Lysaker, Norway.
| | - Yasser Aboelkassem
- San Diego State University, Department of Mechanical Engineering, 5500 Campanile Drive San Diego, CA, 92182, USA
| | - Abigail E Teitgen
- University of California San Diego, Department of Bioengineering, 9500 Gilman Drive MC 0412 La Jolla, CA, 92093, USA
| | - Gary A Huber
- University of California San Diego, Department of Chemistry & Biochemistry, 9500 Gilman Drive, MC 0303 La Jolla, CA, 92093, USA
| | - J Andrew McCammon
- University of California San Diego, Department of Chemistry & Biochemistry, 9500 Gilman Drive, MC 0303 La Jolla, CA, 92093, USA
| | - Michael Regnier
- University of Washington, Department of Bioengineering, Box 355061 Seattle, WA, 98195, USA
| | - Andrew D McCulloch
- University of California San Diego, Department of Bioengineering, 9500 Gilman Drive MC 0412 La Jolla, CA, 92093, USA
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Matyushenko AM, Nefedova VV, Shchepkin DV, Kopylova GV, Berg VY, Pivovarova AV, Kleymenov SY, Bershitsky SY, Levitsky DI. Mechanisms of disturbance of the contractile function of slow skeletal muscles induced by myopathic mutations in the tropomyosin TPM3 gene. FASEB J 2020; 34:13507-13520. [PMID: 32797717 DOI: 10.1096/fj.202001318r] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/17/2020] [Accepted: 07/24/2020] [Indexed: 12/20/2022]
Abstract
Several congenital myopathies of slow skeletal muscles are associated with mutations in the tropomyosin (Tpm) TPM3 gene. Tropomyosin is an actin-binding protein that plays a crucial role in the regulation of muscle contraction. Two Tpm isoforms, γ (Tpm3.12) and β (Tpm2.2) are expressed in human slow skeletal muscles forming γγ-homodimers and γβ-heterodimers of Tpm molecules. We applied various methods to investigate how myopathy-causing mutations M9R, E151A, and K169E in the Tpm γ-chain modify the structure-functional properties of Tpm dimers, and how this affects the muscle functioning. The results show that the features of γγ-Tpm and γβ-Tpm with substitutions in the Tpm γ-chain vary significantly. The characteristics of the γγ-Tpm depend on whether these mutations located in only one or both γ-chains. The mechanism of the development of nemaline myopathy associated with the M9R mutation was revealed. At the molecular level, a cause-and-effect relationship has been established for the development of myopathy by the K169E mutation. Also, we described the structure-functional properties of the Tpm dimers with the E151A mutation, which explain muscle weakness linked to this substitution. The results demonstrate a diversity of the molecular mechanisms of myopathy pathogenesis induced by studied Tpm mutations.
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Affiliation(s)
- Alexander M Matyushenko
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Victoria V Nefedova
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Valentina Y Berg
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Anastasia V Pivovarova
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Sergey Y Kleymenov
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia.,Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Dmitrii I Levitsky
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
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9
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Dompe C, Kranc W, Jopek K, Kowalska K, Ciesiółka S, Chermuła B, Bryja A, Jankowski M, Perek J, Józkowiak M, Moncrieff L, Hutchings G, Janowicz K, Pawelczyk L, Bruska M, Petitte J, Mozdziak P, Kulus M, Piotrowska-Kempisty H, Spaczyński RZ, Nowicki M, Kempisty B. Muscle Cell Morphogenesis, Structure, Development and Differentiation Processes Are Significantly Regulated during Human Ovarian Granulosa Cells In Vitro Cultivation. J Clin Med 2020; 9:jcm9062006. [PMID: 32604796 PMCID: PMC7355984 DOI: 10.3390/jcm9062006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/20/2020] [Accepted: 06/22/2020] [Indexed: 01/03/2023] Open
Abstract
Granulosa cells (GCs) have many functions and are fundamental for both folliculogenesis and oogenesis, releasing hormones and communicating directly with the oocyte. Long-term in vitro cultures of GCs show significant stem-like characteristics. In the current study, RNA of human ovarian granulosa cells was collected at 1, 7, 15 and 30 days of long-term in vitro culture. Understanding the process of differentiation of GCs towards different cell lineages, as well as the molecular pathways underlying these mechanisms, is fundamental to revealing other possible stemness markers of this type of cell. Identifying new markers of GC plasticity may help to understand the aetiology and recurrence of a wide variety of diseases and health conditions and reveal possible clinical applications of the ovarian tissue cells, affecting not only the reproductive ability but also sex hormone production. Granulosa cells were the subject of this study, as they are readily available as remnant material leftover after in vitro fertilisation procedures and exhibit significant stem-like characteristics in culture. The change in gene expression was investigated through a range of molecular and bioinformatic analyses. Expression microarrays were used, allowing the identification of groups of genes typical of specific cellular pathways. This candidate gene study focused on ontological groups associated with muscle cell morphogenesis, structure, development and differentiation, namely, “muscle cell development”, “muscle cell differentiation”, “muscle contraction”, “muscle organ development”, “muscle organ morphogenesis”, “muscle structure development”, “muscle system process” and “muscle tissue development”. The results showed that the 10 most upregulated genes were keratin 19, oxytocin receptor, connective tissue growth factor, nexilin, myosin light chain kinase, cysteine and glycine-rich protein 3, caveolin 1, actin, activating transcription factor 3 and tropomyosin, while the 10 most downregulated consisted of epiregulin, prostaglandin-endoperoxide synthase 2, transforming growth factor, interleukin, collagen, 5-hydroxytryptmine, interleukin 4, phosphodiesterase, wingless-type MMTV integration site family and SRY-box 9. Moreover, ultrastructural observations showing heterogeneity of granulosa cell population are presented in the study. At least two morphologically different subpopulations were identified: large, light coloured and small, darker cells. The expression of genes belonging to the mentioned ontological groups suggest the potential ability of GCs to differentiate and proliferate toward muscle lineage, showing possible application in muscle regeneration and the treatment of different diseases.
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Affiliation(s)
- Claudia Dompe
- The School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZD, UK; (C.D.); (L.M.); (G.H.); (K.J.)
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Wiesława Kranc
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Karol Jopek
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Katarzyna Kowalska
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Sylwia Ciesiółka
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Błażej Chermuła
- Division of Infertility and Reproductive Endocrinology, Department of Gynecology, Obstetrics and Gynecological Oncology, Poznan University of Medical Sciences, 33 Polna St., 60-535 Poznan, Poland; (B.C.); (L.P.); (R.Z.S.)
| | - Artur Bryja
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Maurycy Jankowski
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Joanna Perek
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Małgorzata Józkowiak
- Department of Toxicology, Poznan University of Medical Sciences, 30 Dojazd St., 60-631 Poznan, Poland; (M.J.); (H.P.-K.)
| | - Lisa Moncrieff
- The School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZD, UK; (C.D.); (L.M.); (G.H.); (K.J.)
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Greg Hutchings
- The School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZD, UK; (C.D.); (L.M.); (G.H.); (K.J.)
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Krzysztof Janowicz
- The School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZD, UK; (C.D.); (L.M.); (G.H.); (K.J.)
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - Leszek Pawelczyk
- Division of Infertility and Reproductive Endocrinology, Department of Gynecology, Obstetrics and Gynecological Oncology, Poznan University of Medical Sciences, 33 Polna St., 60-535 Poznan, Poland; (B.C.); (L.P.); (R.Z.S.)
| | - Małgorzata Bruska
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
| | - James Petitte
- Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC 27695, USA;
| | - Paul Mozdziak
- Physiology Graduate Program, North Carolina State University, Raleigh, NC 27695, USA;
| | - Magdalena Kulus
- Department of Veterinary Surgery, Institute of Veterinary Medicine, Nicolaus Copernicus University in Torun, 1 Lwowska St., 87-100 Toruń, Poland;
| | - Hanna Piotrowska-Kempisty
- Department of Toxicology, Poznan University of Medical Sciences, 30 Dojazd St., 60-631 Poznan, Poland; (M.J.); (H.P.-K.)
| | - Robert Z. Spaczyński
- Division of Infertility and Reproductive Endocrinology, Department of Gynecology, Obstetrics and Gynecological Oncology, Poznan University of Medical Sciences, 33 Polna St., 60-535 Poznan, Poland; (B.C.); (L.P.); (R.Z.S.)
| | - Michał Nowicki
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
| | - Bartosz Kempisty
- Department of Histology and Embryology, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (K.J.); (K.K.); (S.C.); (M.N.)
- Department of Anatomy, Poznan University of Medical Sciences, 6 Święcickiego St., 60-781 Poznan, Poland; (W.K.); (A.B.); (M.J.); (J.P.); (M.B.)
- Department of Veterinary Surgery, Institute of Veterinary Medicine, Nicolaus Copernicus University in Torun, 1 Lwowska St., 87-100 Toruń, Poland;
- Department of Obstetrics and Gynecology, University Hospital and Masaryk University, 20 Jihlavská St., 62500 Brno, Czech Republic
- Correspondence: ; Tel.: +48-61-854-6567; Fax: +48-61-854-6568
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10
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Matyushenko AM, Levitsky DI. Molecular Mechanisms of Pathologies of Skeletal and Cardiac Muscles Caused by Point Mutations in the Tropomyosin Genes. BIOCHEMISTRY (MOSCOW) 2020; 85:S20-S33. [PMID: 32087052 DOI: 10.1134/s0006297920140023] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The review is devoted to tropomyosin (Tpm) - actin-binding protein, which plays a crucial role in the regulation of contraction of skeletal and cardiac muscles. Special attention is paid to myopathies and cardiomyopathies - severe hereditary diseases of skeletal and cardiac muscles associated with point mutations in Tpm genes. The current views on the molecular mechanisms of these diseases and the effects of such mutations on the Tpm structure and functions are considered in detail. Besides, some part of the review is devoted to analysis of the properties of Tpm homodimers and heterodimers with myopathic substitutions of amino acid residues in only one of the two chains of the Tpm dimeric molecule.
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Affiliation(s)
- A M Matyushenko
- Bach Institute of Biochemistry, Federal Research Center on Fundamentals of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
| | - D I Levitsky
- Bach Institute of Biochemistry, Federal Research Center on Fundamentals of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia. .,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
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11
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Lehrer SS. The molecular basis for diminished muscle function in acidosis: a proposal. J Muscle Res Cell Motil 2020; 41:259-263. [PMID: 32048111 DOI: 10.1007/s10974-020-09576-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 01/24/2020] [Accepted: 02/05/2020] [Indexed: 11/25/2022]
Abstract
A testable molecular proposal for the effects of acidosis on skeletal and cardiac muscle is presented. It is based on fluorescence studies published in 1974, which provided evidence for carboxylates in an EF-hand Ca2+ binding site having an abnormal pKa. This results in an H+-bound Blocked substate in the 3-state model of muscle regulation whose contribution inhibits myosin binding in the pH 7 to 6 range. A schematic cartoon illustrates the substate within the 3-state model.
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12
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Geeves MA, Lehrer SS, Lehman W. The mechanism of thin filament regulation: Models in conflict? J Gen Physiol 2019; 151:1265-1271. [PMID: 31570503 PMCID: PMC6829557 DOI: 10.1085/jgp.201912446] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 09/05/2019] [Indexed: 01/29/2023] Open
Abstract
Evidence on two- and three-state models of the calcium regulation models of muscle contractions remain in favor of three-state models. In a recent JGP article, Heeley et al. (2019. J. Gen. Physiol. https://doi.org/10.1085/jgp.201812198) reopened the debate about two- versus three-state models of thin filament regulation. The authors review their work, which measures the rate constant of Pi release from myosin.ADP.Pi activated by actin or thin filaments under a variety of conditions. They conclude that their data can be described by a two-state model and raise doubts about the generally accepted three-state model as originally formulated by McKillop and Geeves (1993. Biophys. J.https://doi.org/10.1016/S0006-3495(93)81110-X). However, in the following article, we follow Plato’s dictum that “twice and thrice over, as they say, good it is to repeat and review what is good.” We have therefore reviewed the evidence for the three- and two-state models and present our view that the evidence is overwhelmingly in favor of three structural states of the thin filament, which regulate access of myosin to its binding sites on actin and, hence, muscle contractility.
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Affiliation(s)
| | | | - William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA
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13
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Thin filament dysfunctions caused by mutations in tropomyosin Tpm3.12 and Tpm1.1. J Muscle Res Cell Motil 2019; 41:39-53. [PMID: 31270709 PMCID: PMC7109180 DOI: 10.1007/s10974-019-09532-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 06/26/2019] [Indexed: 12/14/2022]
Abstract
Tropomyosin is the major regulator of the thin filament. In striated muscle its function is to bind troponin complex and control the access of myosin heads to actin in a Ca2+-dependent manner. It also participates in the maintenance of thin filament length by regulation of tropomodulin and leiomodin, the pointed end-binding proteins. Because the size of the overlap between actin and myosin filaments affects the number of myosin heads which interact with actin, the filament length is one of the determinants of force development. Numerous point mutations in genes encoding tropomyosin lead to single amino acid substitutions along the entire length of the coiled coil that are associated with various types of cardiomyopathy and skeletal muscle disease. Specific regions of tropomyosin interact with different binding partners; therefore, the mutations affect diverse tropomyosin functions. In this review, results of studies on mutations in the genes TPM1 and TPM3, encoding Tpm1.1 and Tpm3.12, are described. The paper is particularly focused on mutation-dependent alterations in the mechanisms of actin-myosin interactions and dynamics of the thin filament at the pointed end.
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14
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Lehman W, Rynkiewicz MJ, Moore JR. A new twist on tropomyosin binding to actin filaments: perspectives on thin filament function, assembly and biomechanics. J Muscle Res Cell Motil 2019; 41:23-38. [PMID: 30771202 DOI: 10.1007/s10974-019-09501-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 02/07/2019] [Indexed: 02/07/2023]
Abstract
Tropomyosin, best known for its role in the steric regulation of muscle contraction, polymerizes head-to-tail to form cables localized along the length of both muscle and non-muscle actin-based thin filaments. In skeletal and cardiac muscles, tropomyosin, under the control of troponin and myosin, moves in a cooperative manner between blocked, closed and open positions on filaments, thereby masking and exposing actin-binding sites necessary for myosin crossbridge head interactions. While the coiled-coil signature of tropomyosin appears to be simple, closer inspection reveals surprising structural complexity required to perform its role in steric regulation. For example, component α-helices of coiled coils are typically zippered together along a continuous core hydrophobic stripe. Tropomyosin, however, contains a number of anomalous, functionally controversial, core amino acid residues. We argue that the atypical residues at this interface, including clusters of alanines and a charged aspartate, are required for preshaping tropomyosin to readily fit to the surface of the actin filament, but do so without compromising tropomyosin rigidity once the filament is assembled. Indeed, persistence length measurements of tropomyosin are characteristic of a semi-rigid cable, in this case conducive to cooperative movement on thin filaments. In addition, we also maintain that tropomyosin displays largely unrecognized and residue-specific torsional variance, which is involved in optimizing contacts between actin and tropomyosin on the assembled thin filament. Corresponding twist-induced stiffness may also enhance cooperative translocation of tropomyosin across actin filaments. We conclude that anomalous core residues of tropomyosin facilitate thin filament regulatory behavior in a multifaceted way.
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Affiliation(s)
- William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA.
| | - Michael J Rynkiewicz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, MA, USA
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15
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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: 47] [Impact Index Per Article: 9.4] [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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16
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Li KL, Methawasin M, Tanner BCW, Granzier HL, Solaro RJ, Dong WJ. Sarcomere length-dependent effects on Ca 2+-troponin regulation in myocardium expressing compliant titin. J Gen Physiol 2018; 151:30-41. [PMID: 30523116 PMCID: PMC6314383 DOI: 10.1085/jgp.201812218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 11/01/2018] [Indexed: 11/20/2022] Open
Abstract
Increases in sarcomere length cause enhanced force generation in cardiomyocytes by an unknown mechanism. Li et al. reveal that titin-based passive tension contributes to length-dependent activation of myofilaments and that tightly bound myosin–actin cross-bridges are associated with this effect. Cardiac performance is tightly regulated at the cardiomyocyte level by sarcomere length, such that increases in sarcomere length lead to sharply enhanced force generation at the same Ca2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how length-dependent Ca2+-induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca2+-induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and sarcomere length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca2+-troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of sarcomere length–dependent enhancement of troponin regulation with both Ca2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted sarcomere length–dependent effects. These results suggest that titin-based passive tension contributes to sarcomere length–dependent Ca2+-troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca2+-troponin regulation of the myocardium.
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Affiliation(s)
- King-Lun Li
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Bertrand C W Tanner
- Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Wen-Ji Dong
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA .,Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
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17
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Matyushenko AM, Koubassova NA, Shchepkin DV, Kopylova GV, Nabiev SR, Nikitina LV, Bershitsky SY, Levitsky DI, Tsaturyan AK. The effects of cardiomyopathy-associated mutations in the head-to-tail overlap junction of α-tropomyosin on its properties and interaction with actin. Int J Biol Macromol 2018; 125:1266-1274. [PMID: 30240712 DOI: 10.1016/j.ijbiomac.2018.09.105] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 09/15/2018] [Accepted: 09/17/2018] [Indexed: 10/28/2022]
Abstract
Tropomyosin (Tpm) plays a crucial role in the regulation of muscle contraction by controlling actin-myosin interaction. Tpm coiled-coil molecules bind each other via overlap junctions of their N- and C-termini and form a semi-rigid strand that binds the helical surface of an actin filament. The high bending stiffness of the strand is essential for high cooperativity of muscle regulation. Point mutations M8R and K15N in the N-terminal part of the junction and the A277V one in the C-terminal part are associated with dilated cardiomyopathy, while the M281T and I284V mutations are related to hypertrophic cardiomyopathy. To reveal molecular mechanism(s) underlying these pathologies, we studied the properties of recombinant Tpm carrying these mutations using several experimental approaches and molecular dynamic simulation of the junction. The M8R and K15N mutations weakened the interaction between the N- and C-termini of Tpm in the overlap junction and reduced the Tpm affinity for actin. These changes possibly led to a reduction in the regulation cooperativity. The C-terminal mutations caused only small and controversial changes in properties of Tpm and its complex with actin. Their involvement in disease phenotype is possibly caused by interaction with other sarcomere proteins.
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Affiliation(s)
- Alexander M Matyushenko
- Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, 33 Leninsky prosp., Moscow 119071, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Natalia A Koubassova
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia; Institute of Mechanics, Moscow State University, 1 Mitchurinsky prosp., Moscow 119192, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Salavat R Nabiev
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Larisa V Nikitina
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, 91 Pervomayskaya ul., Yekaterinburg 620049, Russia
| | - Dmitrii I Levitsky
- Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, 33 Leninsky prosp., Moscow 119071, Russia; Belozersky Institute of Physico-Chemical Biology, Moscow State University, 1 Leninskiye Gory bld. 40, Moscow 119234, Russia
| | - Andrey K Tsaturyan
- Institute of Mechanics, Moscow State University, 1 Mitchurinsky prosp., Moscow 119192, Russia.
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18
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The Relaxation Properties of Myofibrils Are Compromised by Amino Acids that Stabilize α-Tropomyosin. Biophys J 2017; 112:376-387. [PMID: 28122223 DOI: 10.1016/j.bpj.2016.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 12/06/2016] [Accepted: 12/08/2016] [Indexed: 12/20/2022] Open
Abstract
We investigated the functional impact of α-tropomyosin (Tm) substituted with one (D137L) or two (D137L/G126R) stabilizing amino acid substitutions on the mechanical behavior of rabbit psoas skeletal myofibrils by replacing endogenous Tm and troponin (Tn) with recombinant Tm mutants and purified skeletal Tn. Force recordings from myofibrils (15°C) at saturating [Ca2+] showed that Tm-stabilizing substitutions did not significantly affect the maximal isometric tension and the rates of force activation (kACT) and redevelopment (kTR). However, a clear effect was observed on force relaxation: myofibrils with D137L/G126R or D137L Tm showed prolonged durations of the slow phase of relaxation and decreased rates of the fast phase. Both Tm-stabilizing substitutions strongly decreased the slack sarcomere length (SL) at submaximal activating [Ca2+] and increased the steepness of the SL-passive tension relation. These effects were reversed by addition of 10 mM 2,3-butanedione 2-monoxime. Myofibrils also showed an apparent increase in Ca2+ sensitivity. Measurements of myofibrillar ATPase activity in the absence of Ca2+ showed a significant increase in the presence of these Tms, indicating that single and double stabilizing substitutions compromise the full inhibition of contraction in the relaxed state. These data can be understood with the three-state (blocked-closed-open) theory of muscle regulation, according to which the mutations increase the contribution of the active open state in the absence of Ca2+ (M-). Force measurements on myofibrils substituted with C-terminal truncated TnI showed similar compromised relaxation effects, indicating the importance of TnI-Tm interactions in maintaining the blocked state. It appears that reducing the flexibility of native Tm coiled-coil structure decreases the optimum interactions of the central part of Tm with the C-terminal region of TnI. This results in a shift away from the blocked state, allowing myosin binding and activity in the absence of Ca2+. This work provides a basis for understanding the effects of disease-producing mutations in muscle proteins.
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19
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Matyushenko AM, Shchepkin DV, Kopylova GV, Popruga KE, Artemova NV, Pivovarova AV, Bershitsky SY, Levitsky DI. Structural and Functional Effects of Cardiomyopathy-Causing Mutations in the Troponin T-Binding Region of Cardiac Tropomyosin. Biochemistry 2016; 56:250-259. [PMID: 27983818 DOI: 10.1021/acs.biochem.6b00994] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a severe heart disease caused by missense mutations in genes encoding sarcomeric proteins of cardiac muscle. Many of these mutations are identified in the gene encoding the cardiac isoform of tropomyosin (Tpm), an α-helical coiled-coil actin-binding protein that plays a key role in Ca2+-regulated contraction of cardiac muscle. We employed various methods to characterize structural and functional features of recombinant human Tpm species carrying HCM mutations that lie either within the troponin T-binding region in the C-terminal part of Tpm (E180G, E180V, and L185R) or near this region (I172T). The results of our structural studies show that all these mutations affect, although differently, the thermal stability of the C-terminal part of the Tpm molecule: mutations E180G and I172T destabilize this part of the molecule, whereas mutation E180V strongly stabilizes it. Moreover, various HCM-causing mutations have different and even opposite effects on the stability of the Tpm-actin complexes. Studies of reconstituted thin filaments in the in vitro motility assay have shown that those HCM-associated mutations that lie within the troponin T-binding region of Tpm similarly increase the Ca2+ sensitivity of the sliding velocity of the filaments and impair their relaxation properties, causing a marked increase in the sliding velocity in the absence of Ca2+, while mutation I172T decreases the Ca2+ sensitivity and has no influence on the sliding velocity under relaxing conditions. Finally, our data demonstrate that various HCM mutations can differently affect the structural and functional properties of Tpm and cause HCM by different molecular mechanisms.
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Affiliation(s)
- Alexander M Matyushenko
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,Department of Biochemistry, School of Biology, Moscow State University , Lenin Hills 1, bld 12, Moscow 119234, Russian Federation
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Katerina E Popruga
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,Department of Biochemistry, School of Biology, Moscow State University , Lenin Hills 1, bld 12, Moscow 119234, Russian Federation
| | - Natalya V Artemova
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation
| | - Anastasia V Pivovarova
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences , Pervomayskaya Street 106, Yekaterinburg 620049, Russian Federation
| | - Dmitrii I Levitsky
- A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences , Leninsky Prospect 33, Moscow 119071, Russian Federation.,A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University , Lenin Hills 1, bld 40, Moscow 119234, Russian Federation
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20
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Aboelkassem Y, Bonilla JA, McCabe KJ, Campbell SG. Contributions of Ca2+-Independent Thin Filament Activation to Cardiac Muscle Function. Biophys J 2016; 109:2101-12. [PMID: 26588569 DOI: 10.1016/j.bpj.2015.09.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 09/03/2015] [Accepted: 09/11/2015] [Indexed: 12/29/2022] Open
Abstract
Although Ca2+ is the principal regulator of contraction in striated muscle, in vitro evidence suggests that some actin-myosin interaction is still possible even in its absence. Whether this Ca2+-independent activation (CIA) occurs under physiological conditions remains unclear, as does its potential impact on the function of intact cardiac muscle. The purpose of this study was to investigate CIA using computational analysis. We added a structurally motivated representation of this phenomenon to an existing myofilament model, which allowed predictions of CIA-dependent muscle behavior. We found that a certain amount of CIA was essential for the model to reproduce reported effects of nonfunctional troponin C on myofilament force generation. Consequently, those data enabled estimation of ΔGCIA, the energy barrier for activating a thin filament regulatory unit in the absence of Ca2+. Using this estimate of ΔGCIA as a point of reference (∼7 kJ mol(-1)), we examined its impact on various aspects of muscle function through additional simulations. CIA decreased the Hill coefficient of steady-state force while increasing myofilament Ca2+ sensitivity. At the same time, CIA had minimal effect on the rate of force redevelopment after slack/restretch. Simulations of twitch tension show that the presence of CIA increases peak tension while profoundly delaying relaxation. We tested the model's ability to represent perturbations to the Ca2+ regulatory mechanism by analyzing twitch records measured in transgenic mice expressing a cardiac troponin I mutation (R145G). The effects of the mutation on twitch dynamics were fully reproduced by a single parameter change, namely lowering ΔGCIA by 2.3 kJ mol(-1) relative to its wild-type value. Our analyses suggest that CIA is present in cardiac muscle under normal conditions and that its modulation by gene mutations or other factors can alter both systolic and diastolic function.
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Affiliation(s)
- Yasser Aboelkassem
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut
| | - Jordan A Bonilla
- Department of Computing and Mathematical Sciences, California Institute of Technology, Pasadena, California
| | - Kimberly J McCabe
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut
| | - Stuart G Campbell
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut.
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21
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Order-Disorder Transitions in the Cardiac Troponin Complex. J Mol Biol 2016; 428:2965-77. [PMID: 27395017 DOI: 10.1016/j.jmb.2016.06.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/21/2016] [Accepted: 06/29/2016] [Indexed: 12/26/2022]
Abstract
The troponin complex is a molecular switch that ties shifting intracellular calcium concentration to association and dissociation of actin and myosin, effectively allowing excitation-contraction coupling in striated muscle. Although there is a long history of muscle biophysics and structural biology, many of the mechanistic details that enable troponin's function remain incompletely understood. This review summarizes the current structural understanding of the troponin complex on the muscle thin filament, focusing on conformational changes in flexible regions of the troponin I subunit. In particular, we focus on order-disorder transitions in the C-terminal domain of troponin I, which have important implications in cardiac disease and could also have potential as a model system for the study of coupled binding and folding.
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22
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Moore JR, Campbell SG, Lehman W. Structural determinants of muscle thin filament cooperativity. Arch Biochem Biophys 2016; 594:8-17. [PMID: 26891592 DOI: 10.1016/j.abb.2016.02.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 11/16/2022]
Abstract
End-to-end connections between adjacent tropomyosin molecules along the muscle thin filament allow long-range conformational rearrangement of the multicomponent filament structure. This process is influenced by Ca(2+) and the troponin regulatory complexes, as well as by myosin crossbridge heads that bind to and activate the filament. Access of myosin crossbridges onto actin is gated by tropomyosin, and in the case of striated muscle filaments, troponin acts as a gatekeeper. The resulting tropomyosin-troponin-myosin on-off switching mechanism that controls muscle contractility is a complex cooperative and dynamic system with highly nonlinear behavior. Here, we review key information that leads us to view tropomyosin as central to the communication pathway that coordinates the multifaceted effectors that modulate and tune striated muscle contraction. We posit that an understanding of this communication pathway provides a framework for more in-depth mechanistic characterization of myopathy-associated mutational perturbations currently under investigation by many research groups.
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Affiliation(s)
- Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts Lowell, One University Avenue, Lowell, MA 018154, USA
| | - Stuart G Campbell
- Department of Biomedical Engineering, Yale University, 55 Prospect Street, New Haven, CT 06511, USA
| | - William Lehman
- Department of Physiology & Biophysics, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA.
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23
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Mun JY, Kensler RW, Harris SP, Craig R. The cMyBP-C HCM variant L348P enhances thin filament activation through an increased shift in tropomyosin position. J Mol Cell Cardiol 2015; 91:141-7. [PMID: 26718724 DOI: 10.1016/j.yjmcc.2015.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 12/08/2015] [Accepted: 12/18/2015] [Indexed: 10/22/2022]
Abstract
Mutations in cardiac myosin binding protein C (cMyBP-C), a thick filament protein that modulates contraction of the heart, are a leading cause of hypertrophic cardiomyopathy (HCM). Electron microscopy and 3D reconstruction of thin filaments decorated with cMyBP-C N-terminal fragments suggest that one mechanism of this modulation involves the interaction of cMyBP-C's N-terminal domains with thin filaments to enhance their Ca(2+)-sensitivity by displacement of tropomyosin from its blocked (low Ca(2+)) to its closed (high Ca(2+)) position. The extent of this tropomyosin shift is reduced when cMyBP-C N-terminal domains are phosphorylated. In the current study, we have examined L348P, a sequence variant of cMyBP-C first identified in a screen of patients with HCM. In L348P, leucine 348 is replaced by proline in cMyBP-C's regulatory M-domain, resulting in an increase in cMyBP-C's ability to enhance thin filament Ca(2+)-sensitization. Our goal here was to determine the structural basis for this enhancement by carrying out 3D reconstruction of thin filaments decorated with L348P-mutant cMyBP-C. When thin filaments were decorated with wild type N-terminal domains at low Ca(2+), tropomyosin moved from the blocked to the closed position, as found previously. In contrast, the L348P mutant caused a significantly larger tropomyosin shift, to approximately the open position, consistent with its enhancement of Ca(2+)-sensitization. Phosphorylated wild type fragments showed a smaller shift than unphosphorylated fragments, whereas the shift induced by the L348P mutant was not affected by phosphorylation. We conclude that the L348P mutation causes a gain of function by enhancing tropomyosin displacement on the thin filament in a phosphorylation-independent way.
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Affiliation(s)
- Ji Young Mun
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Robert W Kensler
- Department of Anatomy and Neurobiology, University of Puerto Rico School of Medicine, San Juan, PR 00936, USA
| | - Samantha P Harris
- Department of Cellular and Molecular Medicine, University of Arizona College of Medicine, Tucson, AZ 85724, USA
| | - Roger Craig
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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24
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Wilder T, Ryba DM, Wieczorek DF, Wolska BM, Solaro RJ. N-acetylcysteine reverses diastolic dysfunction and hypertrophy in familial hypertrophic cardiomyopathy. Am J Physiol Heart Circ Physiol 2015; 309:H1720-30. [PMID: 26432840 DOI: 10.1152/ajpheart.00339.2015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/25/2015] [Indexed: 12/15/2022]
Abstract
S-glutathionylation of cardiac myosin-binding protein C (cMyBP-C) induces Ca(2+) sensitization and a slowing of cross-bridge kinetics as a result of increased oxidative signaling. Although there is evidence for a role of oxidative stress in disorders associated with hypertrophic cardiomyopathy (HCM), this mechanism is not well understood. We investigated whether oxidative myofilament modifications may be in part responsible for diastolic dysfunction in HCM. We administered N-acetylcysteine (NAC) for 30 days to 1-mo-old wild-type mice and to transgenic mice expressing a mutant tropomyosin (Tm-E180G) and nontransgenic littermates. Tm-E180G hearts demonstrate a phenotype similar to human HCM. After NAC administration, the morphology and diastolic function of Tm-E180G mice was not significantly different from controls, indicating that NAC had reversed baseline diastolic dysfunction and hypertrophy in our model. NAC administration also increased sarco(endo)plasmic reticulum Ca(2+) ATPase protein expression, reduced extracellular signal-related kinase 1/2 phosphorylation, and normalized phosphorylation of phospholamban, as assessed by Western blot. Detergent-extracted fiber bundles from NAC-administered Tm-E180G mice showed nearly nontransgenic (NTG) myofilament Ca(2+) sensitivity. Additionally, we found that NAC increased tension cost and rate of cross-bridge reattachment. Tm-E180G myofilaments were found to have a significant increase in S-glutathionylation of cMyBP-C, which was returned to NTG levels upon NAC administration. Taken together, our results indicate that oxidative myofilament modifications are an important mediator in diastolic function, and by relieving this modification we were able to reverse established diastolic dysfunction and hypertrophy in HCM.
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Affiliation(s)
- Tanganyika Wilder
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois; Department of Biology, College of Science and Technology, Florida A & M University, Tallahassee, Florida
| | - David M Ryba
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - David F Wieczorek
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Beata M Wolska
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois; Department of Medicine, Section of Cardiology, University of Illinois at Chicago, Chicago, Illinois; and
| | - R John Solaro
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois;
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25
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Geeves MA, Lehrer SS. Cross-talk, cross-bridges, and calcium activation of cardiac contraction. Biophys J 2015; 107:543-545. [PMID: 25099792 DOI: 10.1016/j.bpj.2014.06.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 06/09/2014] [Indexed: 11/27/2022] Open
Affiliation(s)
- Michael A Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom.
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26
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Gunning PW, Hardeman EC, Lappalainen P, Mulvihill DP. Tropomyosin - master regulator of actin filament function in the cytoskeleton. J Cell Sci 2015; 128:2965-74. [PMID: 26240174 DOI: 10.1242/jcs.172502] [Citation(s) in RCA: 169] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Tropomyosin (Tpm) isoforms are the master regulators of the functions of individual actin filaments in fungi and metazoans. Tpms are coiled-coil parallel dimers that form a head-to-tail polymer along the length of actin filaments. Yeast only has two Tpm isoforms, whereas mammals have over 40. Each cytoskeletal actin filament contains a homopolymer of Tpm homodimers, resulting in a filament of uniform Tpm composition along its length. Evidence for this 'master regulator' role is based on four core sets of observation. First, spatially and functionally distinct actin filaments contain different Tpm isoforms, and recent data suggest that members of the formin family of actin filament nucleators can specify which Tpm isoform is added to the growing actin filament. Second, Tpms regulate whole-organism physiology in terms of morphogenesis, cell proliferation, vesicle trafficking, biomechanics, glucose metabolism and organ size in an isoform-specific manner. Third, Tpms achieve these functional outputs by regulating the interaction of actin filaments with myosin motors and actin-binding proteins in an isoform-specific manner. Last, the assembly of complex structures, such as stress fibers and podosomes involves the collaboration of multiple types of actin filament specified by their Tpm composition. This allows the cell to specify actin filament function in time and space by simply specifying their Tpm isoform composition.
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Affiliation(s)
- Peter W Gunning
- School of Medical Sciences, UNSW Australia, Sydney 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Australia, Sydney 2052, Australia
| | - Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, Helsinki, 00014, Finland
| | - Daniel P Mulvihill
- School of Biosciences, Stacey Building, University of Kent, Canterbury, Kent CT2 7NJ, UK
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27
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Moss RL, Fitzsimons DP, Ralphe JC. Cardiac MyBP-C regulates the rate and force of contraction in mammalian myocardium. Circ Res 2015; 116:183-92. [PMID: 25552695 DOI: 10.1161/circresaha.116.300561] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiac myosin-binding protein-C (cMyBP-C) is a thick filament-associated protein that seems to contribute to the regulation of cardiac contraction through interactions with either myosin or actin or both. Several studies over the past several years have suggested that the interactions of cardiac myosin-binding protein-C with its binding partners vary with its phosphorylation state, binding predominantly to myosin when dephosphorylated and to actin when it is phosphorylated by protein kinase A or other kinases. Here, we summarize evidence suggesting that phosphorylation of cardiac myosin binding protein-C is a key regulator of the kinetics and amplitude of cardiac contraction during β-adrenergic stimulation and increased stimulus frequency. We propose a model for these effects via a phosphorylation-dependent regulation of the kinetics and extent of cooperative recruitment of cross bridges to the thin filament: phosphorylation of cardiac myosin binding protein-C accelerates cross bridge binding to actin, thereby accelerating recruitment and increasing the amplitude of the cardiac twitch. In contrast, enhanced lusitropy as a result of phosphorylation seems to be caused by a direct effect of phosphorylation to accelerate cross-bridge detachment rate. Depression or elimination of one or both of these processes in a disease, such as end-stage heart failure, seems to contribute to the systolic and diastolic dysfunction that characterizes the disease.
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Affiliation(s)
- Richard L Moss
- From the Department of Cell and Regenerative Biology (R.L.M., D.P.F.) and Department of Pediatrics (J.C.R.), University of Wisconsin School of Medicine and Public Health, Madison.
| | - Daniel P Fitzsimons
- From the Department of Cell and Regenerative Biology (R.L.M., D.P.F.) and Department of Pediatrics (J.C.R.), University of Wisconsin School of Medicine and Public Health, Madison
| | - J Carter Ralphe
- From the Department of Cell and Regenerative Biology (R.L.M., D.P.F.) and Department of Pediatrics (J.C.R.), University of Wisconsin School of Medicine and Public Health, Madison
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28
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Khor KH, Campbell FE, Owen H, Shiels IA, Mills PC. Myocardial collagen deposition and inflammatory cell infiltration in cats with pre-clinical hypertrophic cardiomyopathy. Vet J 2014; 203:161-8. [PMID: 25573453 DOI: 10.1016/j.tvjl.2014.11.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 11/25/2014] [Accepted: 11/27/2014] [Indexed: 11/17/2022]
Abstract
The histological features of feline hypertrophic cardiomyopathy (HCM) have been well documented, but there are no reports describing the histological features in mild pre-clinical disease, since cats are rarely screened for the disease in the early stages before clinical signs are apparent. Histological changes at the early stage of the disease in pre-clinical cats could contribute to an improved understanding of disease aetiology or progression. The aim of this study was to evaluate the histological features of HCM in the left ventricular (LV) myocardium of cats diagnosed with pre-clinical HCM. Clinically healthy cats with normal (n = 11) and pre-clinical HCM (n = 6) were identified on the basis of echocardiography; LV free wall dimensions (LVFWd) and/or interventricular septal wall (IVSd) dimensions during diastole of 6-7 mm were defined as HCM, while equivalent dimensions <5.5 mm were defined as normal. LV myocardial sections were assessed and collagen content and inflammatory cell infiltrates were quantified objectively. Multifocal areas of inflammatory cell infiltration, predominantly lymphocytes, were observed frequently in the left myocardium of cats with pre-clinical HCM. Tissue from cats with pre-clinical HCM also had a higher number of neutrophils and a greater collagen content than the myocardium of normal cats. The myocardium variably demonstrated other features characteristic of HCM, including arteriolar mural hypertrophy and interstitial fibrosis and, to a lesser extent, myocardial fibre disarray and cardiomyocyte hypertrophy. These results suggest that an inflammatory process could contribute to increased collagen content and the myocardial fibrosis known to be associated with HCM.
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Affiliation(s)
- K H Khor
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia; Faculty of Veterinary Medicine, University Putra Malaysia, Serdang, Selangor, Malaysia
| | - F E Campbell
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - H Owen
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - I A Shiels
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - P C Mills
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
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29
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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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