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Abood A, Mesner LD, Jeffery ED, Murali M, Lehe M, Saquing J, Farber CR, Sheynkman GM. Long-read proteogenomics to connect disease-associated sQTLs to the protein isoform effectors of disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.17.531557. [PMID: 36993769 PMCID: PMC10055087 DOI: 10.1101/2023.03.17.531557] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
A major fraction of loci identified by genome-wide association studies (GWASs) lead to alterations in alternative splicing, but interpretation of how such alterations impact proteins is hindered by the technical limitations of short-read RNA-seq, which cannot directly link splicing events to full-length transcript or protein isoforms. Long-read RNA-seq represents a powerful tool to define and quantify transcript isoforms, and recently, infer protein isoform existence. Here we present a novel approach that integrates information from GWAS, splicing QTL (sQTL), and PacBio long-read RNA-seq in a disease-relevant model to infer the effects of sQTLs on the ultimate protein isoform products they encode. We demonstrate the utility of our approach using bone mineral density (BMD) GWAS data. We identified 1,863 sQTLs from the Genotype-Tissue Expression (GTEx) project in 732 protein-coding genes which colocalized with BMD associations (H 4 PP ≥ 0.75). We generated deep coverage PacBio long-read RNA-seq data (N=∼22 million full-length reads) on human osteoblasts, identifying 68,326 protein-coding isoforms, of which 17,375 (25%) were novel. By casting the colocalized sQTLs directly onto protein isoforms, we connected 809 sQTLs to 2,029 protein isoforms from 441 genes expressed in osteoblasts. Using these data, we created one of the first proteome-scale resources defining full-length isoforms impacted by colocalized sQTLs. Overall, we found that 74 sQTLs influenced isoforms likely impacted by nonsense mediated decay (NMD) and 190 that potentially resulted in the expression of new protein isoforms. Finally, we identified colocalizing sQTLs in TPM2 for splice junctions between two mutually exclusive exons, and two different transcript termination sites, making it impossible to interpret without long-read RNA-seq data. siRNA mediated knockdown in osteoblasts showed two TPM2 isoforms with opposing effects on mineralization. We expect our approach to be widely generalizable across diverse clinical traits and accelerate system-scale analyses of protein isoform activities modulated by GWAS loci.
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Karpicheva OE, Avrova SV, Bogdanov AL, Sirenko VV, Redwood CS, Borovikov YS. Molecular Mechanisms of Deregulation of Muscle Contractility Caused by the R168H Mutation in TPM3 and Its Attenuation by Therapeutic Agents. Int J Mol Sci 2023; 24:ijms24065829. [PMID: 36982903 PMCID: PMC10051413 DOI: 10.3390/ijms24065829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/13/2023] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
The substitution for Arg168His (R168H) in γ-tropomyosin (TPM3 gene, Tpm3.12 isoform) is associated with congenital muscle fiber type disproportion (CFTD) and muscle weakness. It is still unclear what molecular mechanisms underlie the muscle dysfunction seen in CFTD. The aim of this work was to study the effect of the R168H mutation in Tpm3.12 on the critical conformational changes that myosin, actin, troponin, and tropomyosin undergo during the ATPase cycle. We used polarized fluorescence microscopy and ghost muscle fibers containing regulated thin filaments and myosin heads (myosin subfragment-1) modified with the 1,5-IAEDANS fluorescent probe. Analysis of the data obtained revealed that a sequential interdependent conformational-functional rearrangement of tropomyosin, actin and myosin heads takes place when modeling the ATPase cycle in the presence of wild-type tropomyosin. A multistep shift of the tropomyosin strands from the outer to the inner domain of actin occurs during the transition from weak to strong binding of myosin to actin. Each tropomyosin position determines the corresponding balance between switched-on and switched-off actin monomers and between the strongly and weakly bound myosin heads. At low Ca2+, the R168H mutation was shown to switch some extra actin monomers on and increase the persistence length of tropomyosin, demonstrating the freezing of the R168HTpm strands close to the open position and disruption of the regulatory function of troponin. Instead of reducing the formation of strong bonds between myosin heads and F-actin, troponin activated it. However, at high Ca2+, troponin decreased the amount of strongly bound myosin heads instead of promoting their formation. Abnormally high sensitivity of thin filaments to Ca2+, inhibition of muscle fiber relaxation due to the appearance of the myosin heads strongly associated with F-actin, and distinct activation of the contractile system at submaximal concentrations of Ca2+ can lead to muscle inefficiency and weakness. Modulators of troponin (tirasemtiv and epigallocatechin-3-gallate) and myosin (omecamtiv mecarbil and 2,3-butanedione monoxime) have been shown to more or less attenuate the negative effects of the tropomyosin R168H mutant. Tirasemtiv and epigallocatechin-3-gallate may be used to prevent muscle dysfunction.
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Affiliation(s)
- Olga E Karpicheva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Stanislava V Avrova
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Andrey L Bogdanov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Vladimir V Sirenko
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Charles S Redwood
- Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Yurii S Borovikov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
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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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Molecular Mechanisms of the Deregulation of Muscle Contraction Induced by the R90P Mutation in Tpm3.12 and the Weakening of This Effect by BDM and W7. Int J Mol Sci 2021; 22:ijms22126318. [PMID: 34204776 PMCID: PMC8231546 DOI: 10.3390/ijms22126318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/01/2021] [Accepted: 06/10/2021] [Indexed: 11/17/2022] Open
Abstract
Point mutations in the genes encoding the skeletal muscle isoforms of tropomyosin can cause a range of muscle diseases. The amino acid substitution of Arg for Pro residue in the 90th position (R90P) in γ-tropomyosin (Tpm3.12) is associated with congenital fiber type disproportion and muscle weakness. The molecular mechanisms underlying muscle dysfunction in this disease remain unclear. Here, we observed that this mutation causes an abnormally high Ca2+-sensitivity of myofilaments in vitro and in muscle fibers. To determine the critical conformational changes that myosin, actin, and tropomyosin undergo during the ATPase cycle and the alterations in these changes caused by R90P replacement in Tpm3.12, we used polarized fluorimetry. It was shown that the R90P mutation inhibits the ability of tropomyosin to shift towards the outer domains of actin, which is accompanied by the almost complete depression of troponin’s ability to switch actin monomers off and to reduce the amount of the myosin heads weakly bound to F-actin at a low Ca2+. These changes in the behavior of tropomyosin and the troponin–tropomyosin complex, as well as in the balance of strongly and weakly bound myosin heads in the ATPase cycle may underlie the occurrence of both abnormally high Ca2+-sensitivity and muscle weakness. BDM, an inhibitor of myosin ATPase activity, and W7, a troponin C antagonist, restore the ability of tropomyosin for Ca2+-dependent movement and the ability of the troponin–tropomyosin complex to switch actin monomers off, demonstrating a weakening of the damaging effect of the R90P mutation on muscle contractility.
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Karpicheva OE. Hallmark Features of the Tropomyosin
Regulatory Function in Several Variants of Congenital Myopathy. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021030133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Looking for Targets to Restore the Contractile Function in Congenital Myopathy Caused by Gln 147Pro Tropomyosin. Int J Mol Sci 2020; 21:ijms21207590. [PMID: 33066566 PMCID: PMC7589864 DOI: 10.3390/ijms21207590] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/06/2020] [Accepted: 10/11/2020] [Indexed: 12/15/2022] Open
Abstract
We have used the technique of polarized microfluorimetry to obtain new insight into the pathogenesis of skeletal muscle disease caused by the Gln147Pro substitution in β-tropomyosin (Tpm2.2). The spatial rearrangements of actin, myosin and tropomyosin in the single muscle fiber containing reconstituted thin filaments were studied during simulation of several stages of ATP hydrolysis cycle. The angular orientation of the fluorescence probes bound to tropomyosin was found to be changed by the substitution and was characteristic for a shift of tropomyosin strands closer to the inner actin domains. It was observed both in the absence and in the presence of troponin, Ca2+ and myosin heads at all simulated stages of the ATPase cycle. The mutant showed higher flexibility. Moreover, the Gln147Pro substitution disrupted the myosin-induced displacement of tropomyosin over actin. The irregular positioning of the mutant tropomyosin caused premature activation of actin monomers and a tendency to increase the number of myosin cross-bridges in a state of strong binding with actin at low Ca2+.
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Molecular Mechanisms of Muscle Weakness Associated with E173A Mutation in Tpm3.12. Troponin Ca 2+ Sensitivity Inhibitor W7 Can Reduce the Damaging Effect of This Mutation. Int J Mol Sci 2020; 21:ijms21124421. [PMID: 32580284 PMCID: PMC7352912 DOI: 10.3390/ijms21124421] [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: 05/30/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 12/22/2022] Open
Abstract
Substitution of Ala for Glu residue in position 173 of γ-tropomyosin (Tpm3.12) is associated with muscle weakness. Here we observe that this mutation increases myofilament Ca2+-sensitivity and inhibits in vitro actin-activated ATPase activity of myosin subfragment-1 at high Ca2+. In order to determine the critical conformational changes in myosin, actin and tropomyosin caused by the mutation, we used the technique of polarized fluorimetry. It was found that this mutation changes the spatial arrangement of actin monomers and myosin heads, and the position of the mutant tropomyosin on the thin filaments in muscle fibres at various mimicked stages of the ATPase cycle. At low Ca2+ the E173A mutant tropomyosin shifts towards the inner domains of actin at all stages of the cycle, and this is accompanied by an increase in the number of switched-on actin monomers and myosin heads strongly bound to F-actin even at relaxation. Contrarily, at high Ca2+ the amount of the strongly bound myosin heads slightly decreases. These changes in the balance of the strongly bound myosin heads in the ATPase cycle may underlie the occurrence of muscle weakness. W7, an inhibitor of troponin Ca2+-sensitivity, restores the increase in the number of myosin heads strongly bound to F-actin at high Ca2+ and stops their strong binding at relaxation, suggesting the possibility of using Ca2+-desensitizers to reduce the damaging effect of the E173A mutation on muscle fibre contractility.
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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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Avrova SV, Karpicheva OE, Simonyan AO, Sirenko VV, Redwood CS, Borovikov YS. The molecular mechanisms of a high Ca 2+-sensitivity and muscle weakness associated with the Ala155Thr substitution in Tpm3.12. Biochem Biophys Res Commun 2019; 515:372-377. [PMID: 31155291 DOI: 10.1016/j.bbrc.2019.05.146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 05/23/2019] [Indexed: 12/24/2022]
Abstract
Substitution of Ala for Thr residue in 155th position in γ-tropomyosin (Tpm3.12) is associated with muscle weakness. To understand the mechanisms of this defect, we studied the Ca2+-sensitivity of thin filaments in solution and multistep changes in mobility and spatial arrangement of actin, Tpm, and myosin heads during the ATPase cycle in reconstituted muscle fibres, using the polarized fluorescence microscopy. It was shown that the Ala155Thr (A155T) mutation increased the Ca2+-sensitivity of the thin filaments in solution. In the absence of the myosin heads in the muscle fibres, the mutation did not alter the ability of troponin to switch the thin filaments on and off at high and low Ca2+, respectively. However, upon the binding of myosin heads to the thin filaments at low Ca2+, the mutant Tpm was found to be markedly closer to the open position, than the wild-type Tpm. In the presence of the mutant Tpm, switching on of actin monomers and formation of the strong-binding state of the myosin heads were observed at low Ca2+, which indicated a higher myofilament Ca2+-sensitivity. The mutation decreased the amount of myosin heads bound strongly to actin at high Ca2+ and increased the number of these heads at relaxation. It is suggested that direct binding of myosin to Tpm may be one оf the reasons for muscle weakness associated with the A155T mutation. The use of reagents that decrease the Ca2+-sensitivity of the troponin complex may not be adequate to restore muscle function in patients with the A155T mutation.
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Affiliation(s)
- Stanislava V Avrova
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg, 194064, Russia
| | - Olga E Karpicheva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg, 194064, Russia
| | - Armen O Simonyan
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg, 194064, Russia
| | - Vladimir V Sirenko
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg, 194064, Russia
| | - Charles S Redwood
- Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - Yurii S Borovikov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg, 194064, Russia.
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The Primary Causes of Muscle Dysfunction Associated with the Point Mutations in Tpm3.12; Conformational Analysis of Mutant Proteins as a Tool for Classification of Myopathies. Int J Mol Sci 2018; 19:ijms19123975. [PMID: 30544720 PMCID: PMC6321504 DOI: 10.3390/ijms19123975] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 11/29/2018] [Accepted: 12/07/2018] [Indexed: 12/28/2022] Open
Abstract
Point mutations in genes encoding isoforms of skeletal muscle tropomyosin may cause nemaline myopathy, cap myopathy (Cap), congenital fiber-type disproportion (CFTD), and distal arthrogryposis. The molecular mechanisms of muscle dysfunction in these diseases remain unclear. We studied the effect of the E173A, R90P, E150A, and A155T myopathy-causing substitutions in γ-tropomyosin (Tpm3.12) on the position of tropomyosin in thin filaments, and the conformational state of actin monomers and myosin heads at different stages of the ATPase cycle using polarized fluorescence microscopy. The E173A, R90P, and E150A mutations produced abnormally large displacement of tropomyosin to the inner domains of actin and an increase in the number of myosin heads in strong-binding state at low and high Ca2+, which is characteristic of CFTD. On the contrary, the A155T mutation caused a decrease in the amount of such heads at high Ca2+ which is typical for mutations associated with Cap. An increase in the number of the myosin heads in strong-binding state at low Ca2+ was observed for all mutations associated with high Ca2+-sensitivity. Comparison between the typical conformational changes in mutant proteins associated with different myopathies observed with α-, β-, and γ-tropomyosins demonstrated the possibility of using such changes as tests for identifying the diseases.
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Avrova SV, Karpicheva OE, Rysev NA, Simonyan AO, Sirenko VV, Redwood CS, Borovikov YS. The reason for the low Ca 2+-sensitivity of thin filaments associated with the Glu41Lys mutation in the TPM2 gene is "freezing" of tropomyosin near the outer domain of actin and inhibition of actin monomer switching off during the ATPase cycle. Biochem Biophys Res Commun 2018; 502:209-214. [PMID: 29792862 DOI: 10.1016/j.bbrc.2018.05.145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 05/20/2018] [Indexed: 11/16/2022]
Abstract
The E41K mutation in TPM2 gene encoding muscle regulatory protein beta-tropomyosin is associated with nemaline myopathy and cap disease. The mutation results in a reduced Ca2+-sensitivity of the thin filaments and in muscle weakness. To elucidate the structural basis of the reduced Ca2+-sensitivity of the thin filaments, we studied multistep changes in spatial arrangement of tropomyosin (Tpm), actin and myosin heads during the ATPase cycle in reconstituted fibers, using the polarized fluorescence microscopy. The E41K mutation inhibits troponin's ability to shift Tpm to the closed position at high Ca2+, thus restraining the transition of the thin filaments from the "off" to the "on" state. The mutation also inhibits the ability of S1 to shift Tpm to the open position, decreases the amount of the myosin heads bound strongly to actin at high Ca2+, but increases the number of such heads at low Ca2+. These changes may contribute to the low Ca2+-sensitivity and muscle weakness. As the mutation has no effect on troponin's ability to switch actin monomers on at high Ca2+ and inhibits their switching off at low Ca2+, the use of reagents that increase the Ca2+-sensitivity of the troponin complex may not be appropriate to restore muscle function in patients with this mutation.
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Affiliation(s)
- Stanislava V Avrova
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia
| | - Olga E Karpicheva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia
| | - Nikita A Rysev
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia
| | - Armen O Simonyan
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia; Saint Petersburg State University, 7/9 Universitetskaya emb, St. Petersburg, 199034, Russia
| | - Vladimir V Sirenko
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia
| | - Charles S Redwood
- Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - Yurii S Borovikov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg, 194064, Russia.
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