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Broadway-Stringer S, Jiang H, Wadmore K, Hooper C, Douglas G, Steeples V, Azad AJ, Singer E, Reyat JS, Galatik F, Ehler E, Bennett P, Kalisch-Smith JI, Sparrow DB, Davies B, Djinovic-Carugo K, Gautel M, Watkins H, Gehmlich K. Insights into the Role of a Cardiomyopathy-Causing Genetic Variant in ACTN2. Cells 2023; 12:721. [PMID: 36899856 PMCID: PMC10001372 DOI: 10.3390/cells12050721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/13/2023] [Accepted: 02/21/2023] [Indexed: 03/12/2023] Open
Abstract
Pathogenic variants in ACTN2, coding for alpha-actinin 2, are known to be rare causes of Hypertrophic Cardiomyopathy. However, little is known about the underlying disease mechanisms. Adult heterozygous mice carrying the Actn2 p.Met228Thr variant were phenotyped by echocardiography. For homozygous mice, viable E15.5 embryonic hearts were analysed by High Resolution Episcopic Microscopy and wholemount staining, complemented by unbiased proteomics, qPCR and Western blotting. Heterozygous Actn2 p.Met228Thr mice have no overt phenotype. Only mature males show molecular parameters indicative of cardiomyopathy. By contrast, the variant is embryonically lethal in the homozygous setting and E15.5 hearts show multiple morphological abnormalities. Molecular analyses, including unbiased proteomics, identified quantitative abnormalities in sarcomeric parameters, cell-cycle defects and mitochondrial dysfunction. The mutant alpha-actinin protein is found to be destabilised, associated with increased activity of the ubiquitin-proteasomal system. This missense variant in alpha-actinin renders the protein less stable. In response, the ubiquitin-proteasomal system is activated; a mechanism that has been implicated in cardiomyopathies previously. In parallel, a lack of functional alpha-actinin is thought to cause energetic defects through mitochondrial dysfunction. This seems, together with cell-cycle defects, the likely cause of the death of the embryos. The defects also have wide-ranging morphological consequences.
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Affiliation(s)
| | - He Jiang
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
| | - Kirsty Wadmore
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Charlotte Hooper
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
| | - Gillian Douglas
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
| | - Violetta Steeples
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
| | - Amar J. Azad
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Evie Singer
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Jasmeet S. Reyat
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Frantisek Galatik
- Department of Physiology, Faculty of Science, Charles University, 12800 Prague, Czech Republic
| | - Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London SE1 9RT, UK
- School of Cardiovascular and Metabolic Medicine and Sciences, British Heart Foundation Centre of Research Excellence, King’s College London, London SE1 9RT, UK
| | - Pauline Bennett
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London SE1 9RT, UK
| | | | - Duncan B. Sparrow
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Benjamin Davies
- Transgenic Core, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Kristina Djinovic-Carugo
- European Molecular Biology Laboratory, 38000 Grenoble, France
- Department of Structural and Computational Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Mathias Gautel
- School of Basic and Medical Biosciences, British Heart Foundation Centre of Research Excellence, King’s College London, London SE1 9RT, UK
| | - Hugh Watkins
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
| | - Katja Gehmlich
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK
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Noureddine M, Gehmlich K. Structural and signaling proteins in the Z-disk and their role in cardiomyopathies. Front Physiol 2023; 14:1143858. [PMID: 36935760 PMCID: PMC10017460 DOI: 10.3389/fphys.2023.1143858] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The sarcomere is the smallest functional unit of muscle contraction. It is delineated by a protein-rich structure known as the Z-disk, alternating with M-bands. The Z-disk anchors the actin-rich thin filaments and plays a crucial role in maintaining the mechanical stability of the cardiac muscle. A multitude of proteins interact with each other at the Z-disk and they regulate the mechanical properties of the thin filaments. Over the past 2 decades, the role of the Z-disk in cardiac muscle contraction has been assessed widely, however, the impact of genetic variants in Z-disk proteins has still not been fully elucidated. This review discusses the various Z-disk proteins (alpha-actinin, filamin C, titin, muscle LIM protein, telethonin, myopalladin, nebulette, and nexilin) and Z-disk-associated proteins (desmin, and obscurin) and their role in cardiac structural stability and intracellular signaling. This review further explores how genetic variants of Z-disk proteins are linked to inherited cardiac conditions termed cardiomyopathies.
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Affiliation(s)
- Maya Noureddine
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Maya Noureddine, ; Katja Gehmlich,
| | - Katja Gehmlich
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
- *Correspondence: Maya Noureddine, ; Katja Gehmlich,
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Chronopoulos A, Thorpe SD, Cortes E, Lachowski D, Rice AJ, Mykuliak VV, Róg T, Lee DA, Hytönen VP, Del Río Hernández AE. Syndecan-4 tunes cell mechanics by activating the kindlin-integrin-RhoA pathway. Nat Mater 2020; 19:669-678. [PMID: 31907416 PMCID: PMC7260055 DOI: 10.1038/s41563-019-0567-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 11/19/2019] [Indexed: 05/24/2023]
Abstract
Extensive research over the past decades has identified integrins to be the primary transmembrane receptors that enable cells to respond to external mechanical cues. We reveal here a mechanism whereby syndecan-4 tunes cell mechanics in response to localized tension via a coordinated mechanochemical signalling response that involves activation of two other receptors: epidermal growth factor receptor and β1 integrin. Tension on syndecan-4 induces cell-wide activation of the kindlin-2/β1 integrin/RhoA axis in a PI3K-dependent manner. Furthermore, syndecan-4-mediated tension at the cell-extracellular matrix interface is required for yes-associated protein activation. Extracellular tension on syndecan-4 triggers a conformational change in the cytoplasmic domain, the variable region of which is indispensable for the mechanical adaptation to force, facilitating the assembly of a syndecan-4/α-actinin/F-actin molecular scaffold at the bead adhesion. This mechanotransduction pathway for syndecan-4 should have immediate implications for the broader field of mechanobiology.
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Affiliation(s)
- Antonios Chronopoulos
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - Stephen D Thorpe
- Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK.
| | - Ernesto Cortes
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - Dariusz Lachowski
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - Alistair J Rice
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - Vasyl V Mykuliak
- Faculty of Medicine and Health Technology and BioMediTech, Tampere University, Tampere, Finland
- Fimlab Laboratories, Tampere, Finland
| | - Tomasz Róg
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - David A Lee
- Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK
| | - Vesa P Hytönen
- Faculty of Medicine and Health Technology and BioMediTech, Tampere University, Tampere, Finland.
- Fimlab Laboratories, Tampere, Finland.
| | - Armando E Del Río Hernández
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK.
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O'Sullivan LR, Ajaykumar AP, Dembicka KM, Murphy A, Grennan EP, Young PW. Investigation of calmodulin-like and rod domain mutations suggests common molecular mechanism for α-actinin-1-linked congenital macrothrombocytopenia. FEBS Lett 2019; 594:161-174. [PMID: 31365757 DOI: 10.1002/1873-3468.13562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/22/2019] [Accepted: 07/29/2019] [Indexed: 11/11/2022]
Abstract
Actinin-1 mutations cause dominantly inherited congenital macrothrombocytopenia (CMTP), with mutations in the actin-binding domain increasing actinin's affinity for F-actin. In this study, we examined nine CMTP-causing mutations in the calmodulin-like and rod domains of actinin-1. These mutations increase, to varying degrees, actinin's ability to bundle actin filaments in vitro. Mutations within the calmodulin-like domain decrease its thermal stability slightly but do not dramatically affect calcium binding, with mutant proteins retaining calcium-dependent regulation of filament bundling in vitro. The G764S and E769K mutations increase cytoskeletal association of actinin in cells, and all mutant proteins colocalize with F-actin in cultured HeLa cells. Thus, CMTP-causing actinin-1 mutations outside the actin-binding domain also increase actin association, suggesting a common molecular mechanism underlying actinin-1 related CMTP.
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Affiliation(s)
- Leanne Rose O'Sullivan
- School of Biochemistry and Cell Biology, Western Gateway Building, University College Cork, Cork, Ireland
| | | | - Kornelia Maria Dembicka
- School of Biochemistry and Cell Biology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Aidan Murphy
- School of Biochemistry and Cell Biology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Eamonn Paul Grennan
- School of Biochemistry and Cell Biology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Paul William Young
- School of Biochemistry and Cell Biology, Western Gateway Building, University College Cork, Cork, Ireland
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Jahan F, Madhavan S, Rolova T, Viazmina L, Grönholm M, Gahmberg CG. Phosphorylation of the α-chain in the integrin LFA-1 enables β2-chain phosphorylation and α-actinin binding required for cell adhesion. J Biol Chem 2018; 293:12318-12330. [PMID: 29903913 DOI: 10.1074/jbc.ra118.004318] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 06/11/2018] [Indexed: 11/06/2022] Open
Abstract
The integrin leukocyte function-associated antigen-1 (LFA-1) plays a pivotal role in leukocyte adhesion and migration, but the mechanism(s) by which this integrin is regulated has remained incompletely understood. LFA-1 integrin activity requires phosphorylation of its β2-chain and interactions of its cytoplasmic tail with various cellular proteins. The α-chain is constitutively phosphorylated and necessary for cellular adhesion, but how the α-chain regulates adhesion has remained enigmatic. We now show that substitution of the α-chain phosphorylation site (S1140A) in T cells inhibits the phosphorylation of the functionally important Thr-758 in the β2-chain, binding of α-actinin and 14-3-3 protein, and expression of an integrin-activating epitope after treatment with the stromal cell-derived factor-1α. The presence of this substitution resulted in a loss of cell adhesion and directional cell migration. Moreover, LFA-1 activation through the T-cell receptor in cells expressing the S1140A LFA-1 variant resulted in less Thr-758 phosphorylation, α-actinin and talin binding, and cell adhesion. The finding that the LFA-1 α-chain regulates adhesion through the β-chain via specific phosphorylation at Ser-1140 in the α-chain has not been previously reported and emphasizes that both chains are involved in the regulation of LFA-1 integrin activity.
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Affiliation(s)
- Farhana Jahan
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Sudarrshan Madhavan
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Taisia Rolova
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Larisa Viazmina
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Mikaela Grönholm
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Carl G Gahmberg
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
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Murphy ACH, Lindsay AJ, McCaffrey MW, Djinović-Carugo K, Young PW. Congenital macrothrombocytopenia-linked mutations in the actin-binding domain of α-actinin-1 enhance F-actin association. FEBS Lett 2016; 590:685-95. [PMID: 26879394 DOI: 10.1002/1873-3468.12101] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/09/2016] [Accepted: 02/11/2016] [Indexed: 01/21/2023]
Abstract
Mutations in the actin cross-linking protein actinin-1 were recently linked to dominantly inherited congenital macrothrombocytopenia. Here, we report that several disease-associated mutations that are located within the actinin-1 actin-binding domain cause increased binding of actinin-1 to actin filaments and enhance filament bundling in vitro. These actinin-1 mutants are also more stably associated with the cytoskeleton in cultured cells, as assessed by biochemical fractionation and fluorescence recovery after photobleaching experiments. For two mutations the disruption of contacts between the calponin homology domains within the actinin actin-binding domain may explain increased filament binding--providing mechanistic and structural insights into the basis of actinin-1 dysfunction in congenital macrothrombocytopenia.
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Affiliation(s)
- Anita C H Murphy
- School of Biochemistry and Cell Biology, University College Cork, Ireland
| | - Andrew J Lindsay
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Ireland
| | - Mary W McCaffrey
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Ireland
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Austria.,Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia
| | - Paul W Young
- School of Biochemistry and Cell Biology, University College Cork, Ireland
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Wang J, Fan Y, Dube DK, Sanger JM, Sanger JW. Jasplakinolide reduces actin and tropomyosin dynamics during myofibrillogenesis. Cytoskeleton (Hoboken) 2014; 71:513-29. [PMID: 25145272 DOI: 10.1002/cm.21189] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Accepted: 08/12/2014] [Indexed: 12/20/2022]
Abstract
The premyofibril model proposes a three-stage process for the de novo assembly of myofibrils in cardiac and skeletal muscles: premyofibrils to nascent myofibrils to mature myofibrils. FRAP experiments and jasplakinolide, a drug that stabilizes F-actin, permitted us to determine how decreasing the dynamics of actin filaments affected the dynamics of tropomyosin, troponin-T, troponin-C, and two Z-Band proteins (alpha-actinin, FATZ) in premyofibrils versus mature myofibrils. Jasplakinolide reduced markedly the dynamics of actin in premyofibrils and in mature myofibrils in skeletal muscles. Two isoforms of tropomyosin-1 (TPM1α, TPM1κ) are more dynamic in premyofibrils than in mature myofibrils in control skeletal muscles. Jasplakinolide reduced the exchange rates of tropomyosins in premyofibrils but not in mature myofibrils. The reduced tropomyosin recoveries did not match the YFP-actin recoveries in premyofibrils in jasplakinolide. There were no significant differences in the effects of jasplakinolide on the dynamics of troponins in the thin filaments or of two Z-band proteins in premyofibrils or skeletal mature myofibrils. Cardiac control mature myofibrils lack nebulin, and small decreases in actin (∼5%) and two tropomyosin isoforms (∼10-15%) dynamics are detected in premyofibril to mature myofibril transformations compared with skeletal muscle. In contrast to skeletal muscle, jasplakinolide lowered the dynamics of actin and tropomyosin isoforms in the cardiac mature myofibrils. These results suggest that the dynamics of tropomyosins in control muscle cells are related to actin exchange. These results also suggest a stabilizing role for nebulin, an actin and tropomyosin-binding protein, present in mature myofibrils but not in premyofibrils of skeletal muscles.
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Affiliation(s)
- Jushuo Wang
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
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Greenberg MJ, Moore JR. The molecular basis of frictional loads in the in vitro motility assay with applications to the study of the loaded mechanochemistry of molecular motors. Cytoskeleton (Hoboken) 2010; 67:273-85. [PMID: 20191566 PMCID: PMC2861725 DOI: 10.1002/cm.20441] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Accepted: 02/05/2010] [Indexed: 11/05/2022]
Abstract
Molecular motors convert chemical energy into mechanical movement, generating forces necessary to accomplish an array of cellular functions. Since molecular motors generate force, they typically work under loaded conditions where the motor mechanochemistry is altered by the presence of a load. Several biophysical techniques have been developed to study the loaded behavior and force generating capabilities of molecular motors yet most of these techniques require specialized equipment. The frictional loading assay is a modification to the in vitro motility assay that can be performed on a standard epifluorescence microscope, permitting the high-throughput measurement of the loaded mechanochemistry of molecular motors. Here, we describe a model for the molecular basis of the frictional loading assay by modeling the load as a series of either elastic or viscoelastic elements. The model, which calculates the frictional loads imposed by different binding proteins, permits the measurement of isotonic kinetics, force-velocity relationships, and power curves in the motility assay. We show computationally and experimentally that the frictional load imposed by alpha-actinin, the most widely employed actin binding protein in frictional loading experiments, behaves as a viscoelastic rather than purely elastic load. As a test of the model, we examined the frictional loading behavior of rabbit skeletal muscle myosin under normal and fatigue-like conditions using alpha-actinin as a load. We found that, consistent with fiber studies, fatigue-like conditions cause reductions in myosin isometric force, unloaded sliding velocity, maximal power output, and shift the load at which peak power output occurs.
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Affiliation(s)
- Michael J. Greenberg
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Jeffrey R. Moore
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA
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