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Gonchar AD, Koubassova NA, Kopylova GV, Kochurova AM, Nefedova VV, Yampolskaya DS, Shchepkin DV, Bershitsky SY, Tsaturyan AK, Matyushenko AM, Levitsky DI. Myopathy-causing mutation R91P in the TPM3 gene drastically impairs structural and functional properties of slow skeletal muscle tropomyosin γβ-heterodimer. Arch Biochem Biophys 2024; 752:109881. [PMID: 38185233 DOI: 10.1016/j.abb.2023.109881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 12/23/2023] [Accepted: 12/31/2023] [Indexed: 01/09/2024]
Abstract
Tropomyosin (Tpm) is a regulatory actin-binding protein involved in Ca2+ activation of contraction of striated muscle. In human slow skeletal muscles, two distinct Tpm isoforms, γ and β, are present. They interact to form three types of dimeric Tpm molecules: γγ-homodimers, γβ-heterodimers, or ββ-homodimers, and a majority of the molecules are present as γβ-Tpm heterodimers. Point mutation R91P within the TPM3 gene encoding γ-Tpm is linked to the condition known as congenital fiber-type disproportion (CFTD), which is characterized by severe muscle weakness. Here, we investigated the influence of the R91P mutation in the γ-chain on the properties of the γβ-Tpm heterodimer. We found that the R91P mutation impairs the functional properties of γβ-Tpm heterodimer more severely than those of earlier studied γγ-Tpm homodimer carrying this mutation in both γ-chains. Since a significant part of Tpm molecules in slow skeletal muscle is present as γβ-heterodimers, our results explain why this mutation leads to muscle weakness in CFTD.
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Affiliation(s)
- Anastasiia D Gonchar
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | | | - Galina V Kopylova
- Institute of Immunology and Physiology, The Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Anastasia M Kochurova
- Institute of Immunology and Physiology, The Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Victoria V Nefedova
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | - Daria S Yampolskaya
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, The Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, The Russian Academy of Sciences, Yekaterinburg, 620049, Russia
| | - Andrey K Tsaturyan
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Alexander M Matyushenko
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | - Dmitrii I Levitsky
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
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Robaszkiewicz K, Wróbel J, Moraczewska J. Troponin and a Myopathy-Linked Mutation in TPM3 Inhibit Cofilin-2-Induced Thin Filament Depolymerization. Int J Mol Sci 2023; 24:16457. [PMID: 38003645 PMCID: PMC10671271 DOI: 10.3390/ijms242216457] [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: 10/18/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
Uniform actin filament length is required for synchronized contraction of skeletal muscle. In myopathies linked to mutations in tropomyosin (Tpm) genes, irregular thin filaments are a common feature, which may result from defects in length maintenance mechanisms. The current work investigated the effects of the myopathy-causing p.R91C variant in Tpm3.12, a tropomyosin isoform expressed in slow-twitch muscle fibers, on the regulation of actin severing and depolymerization by cofilin-2. The affinity of cofilin-2 for F-actin was not significantly changed by either Tpm3.12 or Tpm3.12-R91C, though it increased two-fold in the presence of troponin (without Ca2+). Saturation of the filament with cofilin-2 removed both Tpm variants from the filament, although Tpm3.12-R91C was more resistant. In the presence of troponin (±Ca2+), Tpm remained on the filament, even at high cofilin-2 concentrations. Both Tpm3.12 variants inhibited filament severing and depolymerization by cofilin-2. However, the inhibition was more efficient in the presence of Tpm3.12-R91C, indicating that the pathogenic variant impaired cofilin-2-dependent actin filament turnover. Troponin (±Ca2+) further inhibited but did not completely stop cofilin-2-dependent actin severing and depolymerization.
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Affiliation(s)
| | | | - Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Biological Sciences, Kazimierz Wielki University in Bydgoszcz, 85-671 Bydgoszcz, Poland; (K.R.); (J.W.)
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Robaszkiewicz K, Siatkowska M, Wadman RI, Kamsteeg EJ, Chen Z, Merve A, Parton M, Bugiardini E, de Bie C, Moraczewska J. A Novel Variant in TPM3 Causing Muscle Weakness and Concomitant Hypercontractile Phenotype. Int J Mol Sci 2023; 24:16147. [PMID: 38003336 PMCID: PMC10671854 DOI: 10.3390/ijms242216147] [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: 10/12/2023] [Revised: 10/31/2023] [Accepted: 11/06/2023] [Indexed: 11/26/2023] Open
Abstract
A novel variant of unknown significance c.8A > G (p.Glu3Gly) in TPM3 was detected in two unrelated families. TPM3 encodes the transcript variant Tpm3.12 (NM_152263.4), the tropomyosin isoform specifically expressed in slow skeletal muscle fibers. The patients presented with slowly progressive muscle weakness associated with Achilles tendon contractures of early childhood onset. Histopathology revealed features consistent with a nemaline rod myopathy. Biochemical in vitro assays performed with reconstituted thin filaments revealed defects in the assembly of the thin filament and regulation of actin-myosin interactions. The substitution p.Glu3Gly increased polymerization of Tpm3.12, but did not significantly change its affinity to actin alone. Affinity of Tpm3.12 to actin in the presence of troponin ± Ca2+ was decreased by the mutation, which was due to reduced interactions with troponin. Altered molecular interactions affected Ca2+-dependent regulation of the thin filament interactions with myosin, resulting in increased Ca2+ sensitivity and decreased relaxation of the actin-activated myosin ATPase activity. The hypercontractile molecular phenotype probably explains the distal joint contractions observed in the patients, but additional research is needed to explain the relatively mild severity of the contractures. The slowly progressive muscle weakness is most likely caused by the lack of relaxation and prolonged contractions which cause muscle wasting. This work provides evidence for the pathogenicity of the TPM3 c.8A > G variant, which allows for its classification as (likely) pathogenic.
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Affiliation(s)
- Katarzyna Robaszkiewicz
- Department of Biochemistry and Cell Biology, Kazimierz Wielki University, 85-671 Bydgoszcz, Poland; (K.R.); (M.S.)
| | - Małgorzata Siatkowska
- Department of Biochemistry and Cell Biology, Kazimierz Wielki University, 85-671 Bydgoszcz, Poland; (K.R.); (M.S.)
| | - Renske I. Wadman
- Department of Neurology, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands;
| | - Erik-Jan Kamsteeg
- Department of Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands;
| | - Zhiyong Chen
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, The National Hospital for Neurology, London WC1N 3BG, UK; (Z.C.); (M.P.); (E.B.)
- Department of Neurology, National Neuroscience Institute, Singapore 308433, Singapore
| | - Ashirwad Merve
- Department of Neuropathology, UCL Queen Square Institute of Neurology, The National Hospital for Neurology, London WC1N 3BG, UK;
| | - Matthew Parton
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, The National Hospital for Neurology, London WC1N 3BG, UK; (Z.C.); (M.P.); (E.B.)
| | - Enrico Bugiardini
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, The National Hospital for Neurology, London WC1N 3BG, UK; (Z.C.); (M.P.); (E.B.)
| | - Charlotte de Bie
- Department of Genetics, University Medical Utrecht, 3584 CX Utrecht, The Netherlands;
| | - Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Kazimierz Wielki University, 85-671 Bydgoszcz, Poland; (K.R.); (M.S.)
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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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Keyt LK, Duran JM, Bui QM, Chen C, Miyamoto MI, Silva Enciso J, Tardiff JC, Adler ED. Thin filament cardiomyopathies: A review of genetics, disease mechanisms, and emerging therapeutics. Front Cardiovasc Med 2022; 9:972301. [PMID: 36158814 PMCID: PMC9489950 DOI: 10.3389/fcvm.2022.972301] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 07/28/2022] [Indexed: 11/17/2022] Open
Abstract
All muscle contraction occurs due to the cyclical interaction between sarcomeric thin and thick filament proteins within the myocyte. The thin filament consists of the proteins actin, tropomyosin, Troponin C, Troponin I, and Troponin T. Mutations in these proteins can result in various forms of cardiomyopathy, including hypertrophic, restrictive, and dilated phenotypes and account for as many as 30% of all cases of inherited cardiomyopathy. There is significant evidence that thin filament mutations contribute to dysregulation of Ca2+ within the sarcomere and may have a distinct pathomechanism of disease from cardiomyopathy associated with thick filament mutations. A number of distinct clinical findings appear to be correlated with thin-filament mutations: greater degrees of restrictive cardiomyopathy and relatively less left ventricular (LV) hypertrophy and LV outflow tract obstruction than that seen with thick filament mutations, increased morbidity associated with heart failure, increased arrhythmia burden and potentially higher mortality. Most therapies that improve outcomes in heart failure blunt the neurohormonal pathways involved in cardiac remodeling, while most therapies for hypertrophic cardiomyopathy involve use of negative inotropes to reduce LV hypertrophy or septal reduction therapies to reduce LV outflow tract obstruction. None of these therapies directly address the underlying sarcomeric dysfunction associated with thin-filament mutations. With mounting evidence that thin filament cardiomyopathies occur through a distinct mechanism, there is need for therapies targeting the unique, underlying mechanisms tailored for each patient depending on a given mutation.
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Affiliation(s)
- Lucas K. Keyt
- Department of Internal Medicine, University of California, San Diego, San Diego, CA, United States
| | - Jason M. Duran
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Quan M. Bui
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Chao Chen
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | | | - Jorge Silva Enciso
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Jil C. Tardiff
- Department of Medicine and Biomedical Engineering, University of Arizona, Tucson, AZ, United States
| | - Eric D. Adler
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
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McAdow J, Yang S, Ou T, Huang G, Dobbs MB, Gurnett CA, Greenberg MJ, Johnson AN. A pathogenic mechanism associated with myopathies and structural birth defects involves TPM2-directed myogenesis. JCI Insight 2022; 7:152466. [PMID: 35579956 PMCID: PMC9309062 DOI: 10.1172/jci.insight.152466] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 05/13/2022] [Indexed: 11/18/2022] Open
Abstract
Nemaline myopathy (NM) is the most common congenital myopathy, characterized by extreme weakness of the respiratory, limb, and facial muscles. Pathogenic variants in Tropomyosin 2 (TPM2), which encodes a skeletal muscle-specific actin binding protein essential for sarcomere function, cause a spectrum of musculoskeletal disorders that include NM as well as cap myopathy, congenital fiber type disproportion, and distal arthrogryposis (DA). The in vivo pathomechanisms underlying TPM2-related disorders are unknown, so we expressed a series of dominant, pathogenic TPM2 variants in Drosophila embryos and found 4 variants significantly affected muscle development and muscle function. Transient overexpression of the 4 variants also disrupted the morphogenesis of mouse myotubes in vitro and negatively affected zebrafish muscle development in vivo. We used transient overexpression assays in zebrafish to characterize 2 potentially novel TPM2 variants and 1 recurring variant that we identified in patients with DA (V129A, E139K, A155T, respectively) and found these variants caused musculoskeletal defects similar to those of known pathogenic variants. The consistency of musculoskeletal phenotypes in our assays correlated with the severity of clinical phenotypes observed in our patients with DA, suggesting disrupted myogenesis is a potentially novel pathomechanism of TPM2 disorders and that our myogenic assays can predict the clinical severity of TPM2 variants.
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Affiliation(s)
- Jennifer McAdow
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Shuo Yang
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Tiffany Ou
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Gary Huang
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Matthew B Dobbs
- Paley Orthopedic and Spine Institute, West Palm Beach, Florida, USA
| | - Christina A Gurnett
- Department of Neurology.,Department of Orthopedic Surgery.,Department of Pediatrics, and
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Aaron N Johnson
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
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Mutations Q93H and E97K in TPM2 Disrupt Ca-Dependent Regulation of Actin Filaments. Int J Mol Sci 2021; 22:ijms22084036. [PMID: 33919826 PMCID: PMC8070786 DOI: 10.3390/ijms22084036] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 12/12/2022] Open
Abstract
Tropomyosin is a two-chain coiled coil protein, which together with the troponin complex controls interactions of actin with myosin in a Ca2+-dependent manner. In fast skeletal muscle, the contractile actin filaments are regulated by tropomyosin isoforms Tpm1.1 and Tpm2.2, which form homo- and heterodimers. Mutations in the TPM2 gene encoding isoform Tpm2.2 are linked to distal arthrogryposis and congenital myopathy-skeletal muscle diseases characterized by hyper- and hypocontractile phenotypes, respectively. In this work, in vitro functional assays were used to elucidate the molecular mechanisms of mutations Q93H and E97K in TPM2. Both mutations tended to decrease actin affinity of homo-and heterodimers in the absence and presence of troponin and Ca2+, although the effect of Q93H was stronger. Changes in susceptibility of tropomyosin to trypsin digestion suggested that the mutations diversified dynamics of tropomyosin homo- and heterodimers on the filament. The presence of Q93H in homo- and heterodimers strongly decreased activation of the actomyosin ATPase and reduced sensitivity of the thin filament to [Ca2+]. In contrast, the presence of E97K caused hyperactivation of the ATPase and increased sensitivity to [Ca2+]. In conclusion, the hypo- and hypercontractile phenotypes associated with mutations Q93H and E97K in Tpm2.2 are caused by defects in Ca2+-dependent regulation of actin-myosin interactions.
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Regulation of Actin Filament Length by Muscle Isoforms of Tropomyosin and Cofilin. Int J Mol Sci 2020; 21:ijms21124285. [PMID: 32560136 PMCID: PMC7352323 DOI: 10.3390/ijms21124285] [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: 05/20/2020] [Revised: 06/11/2020] [Accepted: 06/13/2020] [Indexed: 12/17/2022] Open
Abstract
In striated muscle the extent of the overlap between actin and myosin filaments contributes to the development of force. In slow twitch muscle fibers actin filaments are longer than in fast twitch fibers, but the mechanism which determines this difference is not well understood. We hypothesized that tropomyosin isoforms Tpm1.1 and Tpm3.12, the actin regulatory proteins, which are specific respectively for fast and slow muscle fibers, differently stabilize actin filaments and regulate severing of the filaments by cofilin-2. Using in vitro assays, we showed that Tpm3.12 bound to F-actin with almost 2-fold higher apparent binding constant (Kapp) than Tpm1.1. Cofilin2 reduced Kapp of both tropomyosin isoforms. In the presence of Tpm1.1 and Tpm3.12 the filaments were longer than unregulated F-actin by 25% and 40%, respectively. None of the tropomyosins affected the affinity of cofilin-2 for F-actin, but according to the linear lattice model both isoforms increased cofilin-2 binding to an isolated site and reduced binding cooperativity. The filaments decorated with Tpm1.1 and Tpm3.12 were severed by cofilin-2 more often than unregulated filaments, but depolymerization of the severed filaments was inhibited. The stabilization of the filaments by Tpm3.12 was more efficient, which can be attributed to lower dynamics of Tpm3.12 binding to actin.
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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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10
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Moraczewska J, Robaszkiewicz K, Śliwinska M, Czajkowska M, Ly T, Kostyukova A, Wen H, Zheng W. Congenital myopathy-related mutations in tropomyosin disrupt regulatory function through altered actin affinity and tropomodulin binding. FEBS J 2019; 286:1877-1893. [PMID: 30768849 PMCID: PMC7202179 DOI: 10.1111/febs.14787] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 12/28/2018] [Accepted: 02/13/2019] [Indexed: 11/28/2022]
Abstract
Tropomyosin (Tpm) binds along actin filaments and regulates myosin binding to control muscle contraction. Tropomodulin binds to the pointed end of a filament and regulates actin dynamics, which maintains the length of a thin filament. To define the structural determinants of these Tpm functions, we examined the effects of two congenital myopathy mutations, A4V and R91C, in the Tpm gene, TPM3, which encodes the Tpm3.12 isoform, specific for slow-twitch muscle fibers. Mutation A4V is located in the tropomodulin-binding, N-terminal region of Tpm3.12. R91C is located in the actin-binding period 3 and directly interacts with actin. The A4V and R91C mutations resulted in a 2.5-fold reduced affinity of Tpm3.12 homodimers for F-actin in the absence and presence of troponin, and a two-fold decrease in actomyosin ATPase activation in the presence of Ca2+ . Actomyosin ATPase inhibition in the absence of Ca2+ was not affected. The Ca2+ sensitivity of ATPase activity was decreased by R91C, but not by A4V. In vitro, R91C altered the ability of tropomodulin 1 (Tmod1) to inhibit actin polymerization at the pointed end of the filaments, which correlated with the reduced affinity of Tpm3.12-R91C for Tmod1. Molecular dynamics simulations of Tpm3.12 in complex with F-actin suggested that both mutations reduce the affinity of Tpm3.12 for F-actin binding by perturbing the van der Waals energy, which may be attributable to two different molecular mechanisms-a reduced flexibility of Tpm3.12-R91C and an increased flexibility of Tpm3.12-A4V.
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Affiliation(s)
- Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Katarzyna Robaszkiewicz
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Małgorzata Śliwinska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Marta Czajkowska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Thu Ly
- Voiland School of Chemical Engineering and Bioengineering, University of Washington, Pullman, WA, USA
| | - Alla Kostyukova
- Voiland School of Chemical Engineering and Bioengineering, University of Washington, Pullman, WA, USA
| | - Han Wen
- Department of Physics, University at Buffalo, SUNY, NY, USA
| | - Wenjun Zheng
- Department of Physics, University at Buffalo, SUNY, NY, USA
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