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Barry ME, Rynkiewicz MJ, Pavadai E, Viana A, Lehman W, Moore JR. Glutamate 139 of tropomyosin is critical for cardiac thin filament blocked-state stabilization. J Mol Cell Cardiol 2024; 188:30-37. [PMID: 38266978 DOI: 10.1016/j.yjmcc.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 12/14/2023] [Accepted: 01/20/2024] [Indexed: 01/26/2024]
Abstract
The cardiac thin filament proteins troponin and tropomyosin control actomyosin formation and thus cardiac contractility. Calcium binding to troponin changes tropomyosin position along the thin filament, allowing myosin head binding to actin required for heart muscle contraction. The thin filament regulatory proteins are hot spots for genetic mutations causing heart muscle dysfunction. While much of the thin filament structure has been characterized, critical regions of troponin and tropomyosin involved in triggering conformational changes remain unresolved. A poorly resolved region, helix-4 (H4) of troponin I, is thought to stabilize tropomyosin in a position on actin that blocks actomyosin interactions at low calcium concentrations during muscle relaxation. We have proposed that contact between glutamate 139 on tropomyosin and positively charged residues on H4 leads to blocking-state stabilization. In this study, we attempted to disrupt these interactions by replacing E139 with lysine (E139K) to define the importance of this residue in thin filament regulation. Comparison of mutant and wild-type tropomyosin was carried out using in-vitro motility assays, actin co-sedimentation, and molecular dynamics simulations to determine perturbations in troponin-tropomyosin function caused by the tropomyosin mutation. Motility assays revealed that mutant thin filaments moved at higher velocity at low calcium with increased calcium sensitivity demonstrating that tropomyosin residue 139 is vital for proper tropomyosin-mediated inhibition during relaxation. Similarly, molecular dynamic simulations revealed a mutation-induced decrease in interaction energy between tropomyosin-E139K and troponin I (R170 and K174). These results suggest that salt-bridge stabilization of tropomyosin position by troponin IH4 is essential to prevent actomyosin interactions during cardiac muscle relaxation.
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Affiliation(s)
- Meaghan E Barry
- Department of Biological Sciences, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, United States of America
| | - Michael J Rynkiewicz
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian and Avedisan School of Medicine, 700 Albany Street, W-408E, Boston, MA 02118, United States of America
| | - Elumalai Pavadai
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian and Avedisan School of Medicine, 700 Albany Street, W-408E, Boston, MA 02118, United States of America
| | - Alex Viana
- Department of Biological Sciences, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, United States of America
| | - William Lehman
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian and Avedisan School of Medicine, 700 Albany Street, W-408E, Boston, MA 02118, United States of America
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, United States of America.
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2
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Fu Y, Wu T, Yu H, Xu J, Zhang JZ, Fu DY, Ye H. The Transcription of Flight Energy Metabolism Enzymes Declined with Aging While Enzyme Activity Increased in the Long-Distance Migratory Moth, Spodoptera frugiperda. INSECTS 2022; 13:936. [PMID: 36292884 PMCID: PMC9604208 DOI: 10.3390/insects13100936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/08/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Of all the things that can fly, the flight mechanisms of insects are possibly the least understood. By using RNAseq, we studied the aging-associated gene expression changes in the thorax of Spodoptera frugiperda females. Three possible flight energy metabolism pathways were constructed based on 32 key metabolic enzymes found in S. frugiperda. Differential expression analysis revealed up to 2000 DEGs within old females versus young ones. Expression and GO and KEGG enrichment analyses indicated that most genes and pathways related to energy metabolism and other biological processes, such as transport, redox, longevity and signaling pathway, were downregulated with aging. However, activity assay showed that the activities of all the five tested key enzymes increased with age. The age-associated transcriptional decrease and activity increase in these enzymes suggest that these enzymes are stable. S. frugiperda is a long-distance migrator, and a high activity of enzymes may be important to guarantee a high flight capacity. The activity ratio of GAPDH/HOAD ranged from 0.594 to 0.412, suggesting that lipid is the main fuel of this species, particularly in old individuals. Moreover, the expression of enzymes in the proline oxidation pathway increased with age, suggesting that this energy metabolic pathway also is important for this species or linked to some aging-specific processes. In addition, the expression of immunity- and repair-related genes also increased with age. This study established the overall transcriptome framework of the flight muscle and aging-associated expression change trajectories in an insect for the first time.
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Affiliation(s)
- Yan Fu
- Yunnan Academy of Biodiversity, School of Biodiversity Conservation, Southwest Forestry University, Kunming 650224, China
| | - Ting Wu
- Yunnan Academy of Biodiversity, School of Biodiversity Conservation, Southwest Forestry University, Kunming 650224, China
| | - Hong Yu
- Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China
| | - Jin Xu
- Yunnan Academy of Biodiversity, School of Biodiversity Conservation, Southwest Forestry University, Kunming 650224, China
- Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China
| | - Jun-Zhong Zhang
- Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China
| | - Da-Ying Fu
- Yunnan Academy of Biodiversity, School of Biodiversity Conservation, Southwest Forestry University, Kunming 650224, China
| | - Hui Ye
- School of Ecology and Environment, Yunnan University, Kunming 650091, China
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3
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Liang HF, Li XD. Locusta migratoria flight muscle troponin partially activates thin filament in a calcium-dependent manner. INSECT MOLECULAR BIOLOGY 2022; 31:346-355. [PMID: 35084070 DOI: 10.1111/imb.12763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/16/2021] [Accepted: 01/17/2022] [Indexed: 06/14/2023]
Abstract
The troponin (Tn) complex, the sensor for Ca2+ to regulate contraction of striated muscle, is composed of three subunits, that is, TnT, TnI and TnC. Different isoforms of TnI and TnC are expressed in the thorax dorsal longitudinal muscle (flight muscle) and the hind leg extensor tibiae muscle (jump muscle) of the migratory locust, Locusta migratoria. The major Tn complexes in the flight muscle and the jump muscle are Tn-171 (TnT1/TnI7/TnC1) and Tn-153 (TnT1/TnI5/TnC3), respectively. Here, we prepared a number of recombinant Tn complexes and the reconstituted thin filaments, and investigated their regulation on thin filament. Although both Tn-171 and Tn-153 regulate thin filament in a Ca2+ -dependent manner, the extent of Ca2+ activation mediated by Tn-171 was significantly lower than that by Tn-153. We demonstrated that TnC1 and TnC3, rather than TnI5 and TnI7, are responsible for the different levels of the thin filament activation. Mutagenesis of TnC1 and TnC3 shows that the low level of TnC1-mediated thin filament activation can be attributed to the noncanonical residue Leu60 in the EF-hand-II of TnC1. We therefore propose that, in addition to Ca2+ , other regulatory mechanism(s) is required for the full activation of locust flight muscle.
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Affiliation(s)
- Hui-Fang Liang
- State Key Laboratory of Integrated Management of Insect Pests and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiang-Dong Li
- State Key Laboratory of Integrated Management of Insect Pests and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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4
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Carman PJ, Barrie KR, Dominguez R. Novel human cell expression method reveals the role and prevalence of posttranslational modification in nonmuscle tropomyosins. J Biol Chem 2021; 297:101154. [PMID: 34478714 PMCID: PMC8463859 DOI: 10.1016/j.jbc.2021.101154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/25/2021] [Accepted: 08/30/2021] [Indexed: 11/29/2022] Open
Abstract
Biochemical studies require large quantities of proteins, which are typically obtained using bacterial overexpression. However, the folding machinery in bacteria is inadequate for expressing many mammalian proteins, which additionally undergo posttranslational modifications (PTMs) that bacteria, yeast, or insect cells cannot perform. Many proteins also require native N- and C-termini and cannot tolerate extra tag amino acids for proper function. Tropomyosin (Tpm), a coiled coil protein that decorates most actin filaments in cells, requires both native N- and C-termini and PTMs, specifically N-terminal acetylation (Nt-acetylation), to polymerize along actin filaments. Here, we describe a new method that combines native protein expression in human cells with an intein-based purification tag that can be precisely removed after purification. Using this method, we expressed several nonmuscle Tpm isoforms (Tpm1.6, Tpm1.7, Tpm2.1, Tpm3.1, Tpm3.2, and Tpm4.2) and the muscle isoform Tpm1.1. Proteomics analysis revealed that human-cell-expressed Tpms present various PTMs, including Nt-acetylation, Ser/Thr phosphorylation, Tyr phosphorylation, and Lys acetylation. Depending on the Tpm isoform (humans express up to 40 Tpm isoforms), Nt-acetylation occurs on either the initiator methionine or on the second residue after removal of the initiator methionine. Human-cell-expressed Tpms bind F-actin differently than their Escherichia coli-expressed counterparts, with or without N-terminal extensions intended to mimic Nt-acetylation, and they can form heterodimers in cells and in vitro. The expression method described here reveals previously unknown features of nonmuscle Tpms and can be used in future structural and biochemical studies with Tpms and other proteins, as shown here for α-synuclein.
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Affiliation(s)
- Peter J Carman
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kyle R Barrie
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Roberto Dominguez
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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5
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Smith QM, Inchingolo AV, Mihailescu MD, Dai H, Kad NM. Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments. eLife 2021; 10:69184. [PMID: 34569933 PMCID: PMC8476120 DOI: 10.7554/elife.69184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 09/11/2021] [Indexed: 11/13/2022] Open
Abstract
Regulated thin filaments (RTFs) tightly control striated muscle contraction through calcium binding to troponin, which enables tropomyosin to expose myosin-binding sites on actin. Myosin binding holds tropomyosin in an open position, exposing more myosin-binding sites on actin, leading to cooperative activation. At lower calcium levels, troponin and tropomyosin turn off the thin filament; however, this is antagonised by the high local concentration of myosin, questioning how the thin filament relaxes. To provide molecular details of deactivation, we used single-molecule imaging of green fluorescent protein (GFP)-tagged myosin-S1 (S1-GFP) to follow the activation of RTF tightropes. In sub-maximal activation conditions, RTFs are not fully active, enabling direct observation of deactivation in real time. We observed that myosin binding occurs in a stochastic step-wise fashion; however, an unexpectedly large probability of multiple contemporaneous detachments is observed. This suggests that deactivation of the thin filament is a coordinated active process.
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Affiliation(s)
- Quentin M Smith
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | | | | | - Hongsheng Dai
- Department of Mathematical Sciences, University of Essex, Colchester, United Kingdom
| | - Neil M Kad
- School of Biosciences, University of Kent, Canterbury, United Kingdom
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6
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Racca AW, Rynkiewicz MJ, LaFave N, Ghosh A, Lehman W, Moore JR. M8R tropomyosin mutation disrupts actin binding and filament regulation: The beginning affects the middle and end. J Biol Chem 2020; 295:17128-17137. [PMID: 33020181 PMCID: PMC7863880 DOI: 10.1074/jbc.ra120.014713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 09/28/2020] [Indexed: 11/06/2022] Open
Abstract
Dilated cardiomyopathy (DCM) is associated with mutations in cardiomyocyte sarcomeric proteins, including α-tropomyosin. In conjunction with troponin, tropomyosin shifts to regulate actomyosin interactions. Tropomyosin molecules overlap via tropomyosin-tropomyosin head-to-tail associations, forming a continuous strand along the thin filament. These associations are critical for propagation of tropomyosin's reconfiguration along the thin filament and key for the cooperative switching between heart muscle contraction and relaxation. Here, we tested perturbations in tropomyosin structure, biochemistry, and function caused by the DCM-linked mutation, M8R, which is located at the overlap junction. Localized and nonlocalized structural effects of the mutation were found in tropomyosin that ultimately perturb its thin filament regulatory function. Comparison of mutant and WT α-tropomyosin was carried out using in vitro motility assays, CD, actin co-sedimentation, and molecular dynamics simulations. Regulated thin filament velocity measurements showed that the presence of M8R tropomyosin decreased calcium sensitivity and thin filament cooperativity. The co-sedimentation of actin and tropomyosin showed weakening of actin-mutant tropomyosin binding. The binding of troponin T's N terminus to the actin-mutant tropomyosin complex was also weakened. CD and molecular dynamics indicate that the M8R mutation disrupts the four-helix bundle at the head-to-tail junction, leading to weaker tropomyosin-tropomyosin binding and weaker tropomyosin-actin binding. Molecular dynamics revealed that altered end-to-end bond formation has effects extending toward the central region of the tropomyosin molecule, which alter the azimuthal position of tropomyosin, likely disrupting the mutant thin filament response to calcium. These results demonstrate that mutation-induced alterations in tropomyosin-thin filament interactions underlie the altered regulatory phenotype and ultimately the pathogenesis of DCM.
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Affiliation(s)
- Alice Ward Racca
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts, USA
| | - Michael J Rynkiewicz
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Nicholas LaFave
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts, USA
| | - Anita Ghosh
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - William Lehman
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts, USA.
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7
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Schmidt W, Madan A, Foster DB, Cammarato A. Lysine acetylation of F-actin decreases tropomyosin-based inhibition of actomyosin activity. J Biol Chem 2020; 295:15527-15539. [PMID: 32873710 DOI: 10.1074/jbc.ra120.015277] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/18/2020] [Indexed: 12/17/2022] Open
Abstract
Recent proteomics studies of vertebrate striated muscle have identified lysine acetylation at several sites on actin. Acetylation is a reversible post-translational modification that neutralizes lysine's positive charge. Positively charged residues on actin, particularly Lys326 and Lys328, are predicted to form critical electrostatic interactions with tropomyosin (Tpm) that promote its binding to filamentous (F)-actin and bias Tpm to an azimuthal location where it impedes myosin attachment. The troponin (Tn) complex also influences Tpm's position along F-actin as a function of Ca2+ to regulate exposure of myosin-binding sites and, thus, myosin cross-bridge recruitment and force production. Interestingly, Lys326 and Lys328 are among the documented acetylated residues. Using an acetic anhydride-based labeling approach, we showed that excessive, nonspecific actin acetylation did not disrupt characteristic F-actin-Tpm binding. However, it significantly reduced Tpm-mediated inhibition of myosin attachment, as reflected by increased F-actin-Tpm motility that persisted in the presence of Tn and submaximal Ca2+ Furthermore, decreasing the extent of chemical acetylation, to presumptively target highly reactive Lys326 and Lys328, also resulted in less inhibited F-actin-Tpm, implying that modifying only these residues influences Tpm's location and, potentially, thin filament regulation. To unequivocally determine the residue-specific consequences of acetylation on Tn-Tpm-based regulation of actomyosin activity, we assessed the effects of K326Q and K328Q acetyl (Ac)-mimetic actin on Ca2+-dependent, in vitro motility parameters of reconstituted thin filaments (RTFs). Incorporation of K328Q actin significantly enhanced Ca2+ sensitivity of RTF activation relative to control. Together, our findings suggest that actin acetylation, especially Lys328, modulates muscle contraction via disrupting inhibitory Tpm positioning.
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Affiliation(s)
- William Schmidt
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Aditi Madan
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - D Brian Foster
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Anthony Cammarato
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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8
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Madan A, Viswanathan MC, Woulfe KC, Schmidt W, Sidor A, Liu T, Nguyen TH, Trinh B, Wilson C, Madathil S, Vogler G, O'Rourke B, Biesiadecki BJ, Tobacman LS, Cammarato A. TNNT2 mutations in the tropomyosin binding region of TNT1 disrupt its role in contractile inhibition and stimulate cardiac dysfunction. Proc Natl Acad Sci U S A 2020; 117:18822-18831. [PMID: 32690703 PMCID: PMC7414051 DOI: 10.1073/pnas.2001692117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Muscle contraction is regulated by the movement of end-to-end-linked troponin-tropomyosin complexes over the thin filament surface, which uncovers or blocks myosin binding sites along F-actin. The N-terminal half of troponin T (TnT), TNT1, independently promotes tropomyosin-based, steric inhibition of acto-myosin associations, in vitro. Recent structural models additionally suggest TNT1 may restrain the uniform, regulatory translocation of tropomyosin. Therefore, TnT potentially contributes to striated muscle relaxation; however, the in vivo functional relevance and molecular basis of this noncanonical role remain unclear. Impaired relaxation is a hallmark of hypertrophic and restrictive cardiomyopathies (HCM and RCM). Investigating the effects of cardiomyopathy-causing mutations could help clarify TNT1's enigmatic inhibitory property. We tested the hypothesis that coupling of TNT1 with tropomyosin's end-to-end overlap region helps anchor tropomyosin to an inhibitory position on F-actin, where it deters myosin binding at rest, and that, correspondingly, cross-bridge cycling is defectively suppressed under diastolic/low Ca2+ conditions in the presence of HCM/RCM lesions. The impact of TNT1 mutations on Drosophila cardiac performance, rat myofibrillar and cardiomyocyte properties, and human TNT1's propensity to inhibit myosin-driven, F-actin-tropomyosin motility were evaluated. Our data collectively demonstrate that removing conserved, charged residues in TNT1's tropomyosin-binding domain impairs TnT's contribution to inhibitory tropomyosin positioning and relaxation. Thus, TNT1 may modulate acto-myosin activity by optimizing F-actin-tropomyosin interfacial contacts and by binding to actin, which restrict tropomyosin's movement to activating configurations. HCM/RCM mutations, therefore, highlight TNT1's essential role in contractile regulation by diminishing its tropomyosin-anchoring effects, potentially serving as the initial trigger of pathology in our animal models and humans.
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Affiliation(s)
- Aditi Madan
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Meera C Viswanathan
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Kathleen C Woulfe
- Department of Medicine, Division of Cardiology, University of Colorado Denver, Aurora, CO 80045
| | - William Schmidt
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Agnes Sidor
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Ting Liu
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Tran H Nguyen
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Bosco Trinh
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Cortney Wilson
- Department of Medicine, Division of Cardiology, University of Colorado Denver, Aurora, CO 80045
| | - Sineej Madathil
- Department of Medicine, University of Illinois College of Medicine, Chicago, IL 60612
| | - Georg Vogler
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Brian O'Rourke
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205
| | - Brandon J Biesiadecki
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210
- The Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
| | - Larry S Tobacman
- Department of Medicine, University of Illinois College of Medicine, Chicago, IL 60612
| | - Anthony Cammarato
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205;
- Department of Physiology, Johns Hopkins University, Baltimore, MD 21205
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9
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Viswanathan MC, Schmidt W, Franz P, Rynkiewicz MJ, Newhard CS, Madan A, Lehman W, Swank DM, Preller M, Cammarato A. A role for actin flexibility in thin filament-mediated contractile regulation and myopathy. Nat Commun 2020; 11:2417. [PMID: 32415060 PMCID: PMC7229152 DOI: 10.1038/s41467-020-15922-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 03/30/2020] [Indexed: 12/20/2022] Open
Abstract
Striated muscle contraction is regulated by the translocation of troponin-tropomyosin strands over the thin filament surface. Relaxation relies partly on highly-favorable, conformation-dependent electrostatic contacts between actin and tropomyosin, which position tropomyosin such that it impedes actomyosin associations. Impaired relaxation and hypercontractile properties are hallmarks of various muscle disorders. The α-cardiac actin M305L hypertrophic cardiomyopathy-causing mutation lies near residues that help confine tropomyosin to an inhibitory position along thin filaments. Here, we investigate M305L actin in vivo, in vitro, and in silico to resolve emergent pathological properties and disease mechanisms. Our data suggest the mutation reduces actin flexibility and distorts the actin-tropomyosin electrostatic energy landscape that, in muscle, result in aberrant contractile inhibition and excessive force. Thus, actin flexibility may be required to establish and maintain interfacial contacts with tropomyosin as well as facilitate its movement over distinct actin surface features and is, therefore, likely necessary for proper regulation of contraction. The α-cardiac actin M305L hypertrophic cardiomyopathy-causing mutation is located near residues that help confine tropomyosin to an inhibitory position along thin filaments. Here the authors assessed M305L actin in vivo, in vitro, and in silico to characterize emergent pathological properties and define the mechanistic basis of disease.
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Affiliation(s)
- Meera C Viswanathan
- Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD, 21205, USA
| | - William Schmidt
- Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD, 21205, USA
| | - Peter Franz
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Michael J Rynkiewicz
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street St, Boston, MA, 02118, USA
| | - Christopher S Newhard
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180-3590, USA
| | - Aditi Madan
- Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD, 21205, USA
| | - William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street St, Boston, MA, 02118, USA
| | - Douglas M Swank
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180-3590, USA
| | - Matthias Preller
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
| | - Anthony Cammarato
- Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD, 21205, USA. .,Department of Physiology, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD, 21205, USA.
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10
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Sundar S, Rynkiewicz MJ, Ghosh A, Lehman W, Moore JR. Cardiomyopathy Mutation Alters End-to-End Junction of Tropomyosin and Reduces Calcium Sensitivity. Biophys J 2019; 118:303-312. [PMID: 31882250 DOI: 10.1016/j.bpj.2019.11.3396] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 10/30/2019] [Accepted: 11/18/2019] [Indexed: 12/24/2022] Open
Abstract
Muscle contraction is governed by tropomyosin (Tpm) shifting azimuthally between three states on F-actin (B-, C-, and M-states) in response to calcium binding to troponin and actomyosin cross-bridge formation. The Tpm coiled coil polymerizes head to tail along the long-pitch helix of F-actin to form continuous superhelical cables that wrap around the actin filaments. The end-to-end bonds formed between the N- and C-terminus of adjacent Tpm molecules define Tpm continuity and play a critical role in the ability of Tpm to cooperatively bind to actin, thus facilitating Tpm conformational switching to cooperatively propagate along F-actin. We expect that a missense mutation in this critical overlap region associated with dilated cardiomyopathy, A277V, will alter Tpm binding and thin filament activation by altering the overlap structure. Here, we used cosedimentation assays and in vitro motility assays to determine how the mutation alters Tpm binding to actin and its ability to regulate actomyosin interactions. Analytical viscometry coupled with molecular dynamics simulations showed that the A277V mutation results in enhanced Tpm end-to-end bond strength and a reduced curvature of the Tpm overlap domain. The mutant Tpm exhibited enhanced actin-Tpm binding affinity, consistent with overlap stabilization. The observed A277V-induced decrease in cooperative activation observed with regulated thin filament motility indicates that increased overlap stabilization is not correlated with Tpm-Tpm overlap binding strength or mechanical rigidity as is often assumed. Instead, A277V-induced structural changes result in local and delocalized increases in Tpm flexibility and prominent coiled-coil twisting in pseudorepeat 4. An A277V-induced decrease in Ca2+ sensitivity, consistent with a mutation-induced bolstering of the B-state Tpm-actin electrostatic contacts and an increased Tpm troponin T1 binding affinity, was also observed.
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Affiliation(s)
- SaiLavanyaa Sundar
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts
| | - Michael J Rynkiewicz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
| | - Anita Ghosh
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
| | - William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts.
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11
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Aboelkassem Y, McCabe KJ, Huber GA, Regnier M, McCammon JA, McCulloch AD. A Stochastic Multiscale Model of Cardiac Thin Filament Activation Using Brownian-Langevin Dynamics. Biophys J 2019; 117:2255-2272. [PMID: 31547973 DOI: 10.1016/j.bpj.2019.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 11/16/2022] Open
Abstract
We use Brownian-Langevin dynamics principles to derive a coarse-graining multiscale myofilament model that can describe the thin-filament activation process during contraction. The model links atomistic molecular simulations of protein-protein interactions in the thin-filament regulatory unit to sarcomere-level activation dynamics. We first calculate the molecular interaction energy between tropomyosin and actin surface using Brownian dynamics simulations. This energy profile is then generalized to account for the observed tropomyosin transitions between its regulatory stable states. The generalized energy landscape then served as a basis for developing a filament-scale model using Langevin dynamics. This integrated analysis, spanning molecular to thin-filament scales, is capable of tracking the events of the tropomyosin conformational changes as it moves over the actin surface. The tropomyosin coil with flexible overlap regions between adjacent tropomyosins is represented in the model as a system of coupled stochastic ordinary differential equations. The proposed multiscale approach provides a more detailed molecular connection between tropomyosin dynamics, the trompomyosin-actin interaction-energy landscape, and the generated force by the sarcomere.
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Affiliation(s)
- Yasser Aboelkassem
- Department of Bioengineering, University of California San Diego, La Jolla, California.
| | - Kimberly J McCabe
- Department of Bioengineering, University of California San Diego, La Jolla, California
| | - Gary A Huber
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, California
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12
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Schmidt W, Cammarato A. The actin 'A-triad's' role in contractile regulation in health and disease. J Physiol 2019; 598:2897-2908. [PMID: 30770548 DOI: 10.1113/jp276741] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 01/30/2019] [Indexed: 12/15/2022] Open
Abstract
Striated muscle contraction is regulated by Ca2+ -dependent modulation of myosin cross-bridge binding to F-actin by the thin filament troponin (Tn)-tropomyosin (Tm) complex. In the absence of Ca2+ , Tn binds to actin and constrains Tm to an azimuthal location where it sterically occludes myosin binding sites along the thin filament surface. This limits force production and promotes muscle relaxation. In addition to Tn-actin interactions, inhibitory Tm positioning requires associations between other thin filament constituents. For example, the actin 'A-triad', composed of residues K326, K328 and R147, forms numerous, highly favourable electrostatic contacts with Tm that are critical for establishing its inhibitory azimuthal binding position. Here, we review recent findings, including the identification and interrogation of modifications within and proximal to the A-triad that are associated with disease and/or altered muscle behaviour, which highlight the surface feature's role in F-actin-Tm interactions and contractile regulation.
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Affiliation(s)
- William Schmidt
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA.,Department of Physiology, Johns Hopkins University School of Medicine, 733 N Broadway, 21205, Baltimore, MD, USA
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13
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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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14
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Papadaki M, Holewinski RJ, Previs SB, Martin TG, Stachowski MJ, Li A, Blair CA, Moravec CS, Van Eyk JE, Campbell KS, Warshaw DM, Kirk JA. Diabetes with heart failure increases methylglyoxal modifications in the sarcomere, which inhibit function. JCI Insight 2018; 3:121264. [PMID: 30333300 DOI: 10.1172/jci.insight.121264] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 09/04/2018] [Indexed: 12/27/2022] Open
Abstract
Patients with diabetes are at significantly higher risk of developing heart failure. Increases in advanced glycation end products are a proposed pathophysiological link, but their impact and mechanism remain incompletely understood. Methylglyoxal (MG) is a glycolysis byproduct, elevated in diabetes, and modifies arginine and lysine residues. We show that left ventricular myofilament from patients with diabetes and heart failure (dbHF) exhibited increased MG modifications compared with nonfailing controls (NF) or heart failure patients without diabetes. In skinned NF human and mouse cardiomyocytes, acute MG treatment depressed both calcium sensitivity and maximal calcium-activated force in a dose-dependent manner. Importantly, dbHF myocytes were resistant to myofilament functional changes from MG treatment, indicating that myofilaments from dbHF patients already had depressed function arising from MG modifications. In human dbHF and MG-treated mice, mass spectrometry identified increased MG modifications on actin and myosin. Cosedimentation and in vitro motility assays indicate that MG modifications on actin and myosin independently depress calcium sensitivity, and mechanistically, the functional consequence requires actin/myosin interaction with thin-filament regulatory proteins. MG modification of the myofilament may represent a critical mechanism by which diabetes induces heart failure, as well as a therapeutic target to avoid the development of or ameliorate heart failure in these patients.
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Affiliation(s)
- Maria Papadaki
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | | | - Samantha Beck Previs
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Thomas G Martin
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | - Marisa J Stachowski
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | - Amy Li
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Cheavar A Blair
- University of Kentucky, Department of Physiology, Lexington, Kentucky, USA
| | - Christine S Moravec
- The Cleveland Clinic, Department of Molecular Cardiology, Cleveland, Ohio, USA
| | - Jennifer E Van Eyk
- Cedars-Sinai Medical Center, Heart Institute, Los Angeles, California, USA
| | - Kenneth S Campbell
- University of Kentucky, Department of Physiology, Lexington, Kentucky, USA
| | - David M Warshaw
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Jonathan A Kirk
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
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15
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The Molecular Mechanisms of Mutations in Actin and Myosin that Cause Inherited Myopathy. Int J Mol Sci 2018; 19:ijms19072020. [PMID: 29997361 PMCID: PMC6073311 DOI: 10.3390/ijms19072020] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 07/06/2018] [Accepted: 07/08/2018] [Indexed: 12/23/2022] Open
Abstract
The discovery that mutations in myosin and actin genes, together with mutations in the other components of the muscle sarcomere, are responsible for a range of inherited muscle diseases (myopathies) has revolutionized the study of muscle, converting it from a subject of basic science to a relevant subject for clinical study and has been responsible for a great increase of interest in muscle studies. Myopathies are linked to mutations in five of the myosin heavy chain genes, three of the myosin light chain genes, and three of the actin genes. This review aims to determine to what extent we can explain disease phenotype from the mutant genotype. To optimise our chances of finding the right mechanism we must study a myopathy where there are a large number of different mutations that cause a common phenotype and so are likely to have a common mechanism: a corollary to this criterion is that if any mutation causes the disease phenotype but does not correspond to the proposed mechanism, then the whole mechanism is suspect. Using these criteria, we consider two cases where plausible genotype-phenotype mechanisms have been proposed: the actin “A-triad” and the myosin “mesa/IHD” models.
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16
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Barnes DE, Watabe E, Ono K, Kwak E, Kuroyanagi H, Ono S. Tropomyosin isoforms differentially affect muscle contractility in the head and body regions of the nematode Caenorhabditis elegans. Mol Biol Cell 2018; 29:1075-1088. [PMID: 29496965 PMCID: PMC5921574 DOI: 10.1091/mbc.e17-03-0152] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 02/21/2018] [Accepted: 02/23/2018] [Indexed: 11/11/2022] Open
Abstract
Tropomyosin, one of the major actin filament-binding proteins, regulates actin-myosin interaction and actin-filament stability. Multicellular organisms express a number of tropomyosin isoforms, but understanding of isoform-specific tropomyosin functions is incomplete. The nematode Caenorhabditis elegans has a single tropomyosin gene, lev-11, which has been reported to express four isoforms by using two separate promoters and alternative splicing. Here, we report a fifth tropomyosin isoform, LEV-11O, which is produced by alternative splicing that includes a newly identified seventh exon, exon 7a. By visualizing specific splicing events in vivo, we find that exon 7a is predominantly selected in a subset of the body wall muscles in the head, while exon 7b, which is the alternative to exon 7a, is utilized in the rest of the body. Point mutations in exon 7a and exon 7b cause resistance to levamisole--induced muscle contraction specifically in the head and the main body, respectively. Overexpression of LEV-11O, but not LEV-11A, in the main body results in weak levamisole resistance. These results demonstrate that specific tropomyosin isoforms are expressed in the head and body regions of the muscles and contribute differentially to the regulation of muscle contractility.
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Affiliation(s)
- Dawn E. Barnes
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Eichi Watabe
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Kanako Ono
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Euiyoung Kwak
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Hidehito Kuroyanagi
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Shoichiro Ono
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
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17
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Farman GP, Rynkiewicz MJ, Orzechowski M, Lehman W, Moore JR. HCM and DCM cardiomyopathy-linked α-tropomyosin mutations influence off-state stability and crossbridge interaction on thin filaments. Arch Biochem Biophys 2018; 647:84-92. [PMID: 29626422 DOI: 10.1016/j.abb.2018.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/02/2018] [Accepted: 04/03/2018] [Indexed: 12/19/2022]
Abstract
Calcium regulation of cardiac muscle contraction is controlled by the thin-filament proteins troponin and tropomyosin bound to actin. In the absence of calcium, troponin-tropomyosin inhibits myosin-interactions on actin and induces muscle relaxation, whereas the addition of calcium relieves the inhibitory constraint to initiate contraction. Many mutations in thin filament proteins linked to cardiomyopathy appear to disrupt this regulatory switching. Here, we tested perturbations caused by mutant tropomyosins (E40K, DCM; and E62Q, HCM) on intra-filament interactions affecting acto-myosin interactions including those induced further by myosin association. Comparison of wild-type and mutant human α-tropomyosin (Tpm1.1) behavior was carried out using in vitro motility assays and molecular dynamics simulations. Our results show that E62Q tropomyosin destabilizes thin filament off-state function by increasing calcium-sensitivity, but without apparent affect on global tropomyosin structure by modifying coiled-coil rigidity. In contrast, the E40K mutant tropomyosin appears to stabilize the off-state, demonstrates increased tropomyosin flexibility, while also decreasing calcium-sensitivity. In addition, the E40K mutation reduces thin filament velocity at low myosin concentration while the E62Q mutant tropomyosin increases velocity. Corresponding molecular dynamics simulations indicate specific residue interactions that are likely to redefine underlying molecular regulatory mechanisms, which we propose explain the altered contractility evoked by the disease-causing mutations.
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Affiliation(s)
- Gerrie P Farman
- Department of Biological Sciences, University of Massachusetts-Lowell, One University Avenue, Lowell, MA 01854, USA; Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Michael J Rynkiewicz
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Marek Orzechowski
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - William Lehman
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, One University Avenue, Lowell, MA 01854, USA.
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