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Jean-claude Perriard - One of the best experts on this subject based on the ideXlab platform.
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Myomesin 3 a novel structural component of the m band in striated muscle
Journal of Molecular Biology, 2008Co-Authors: Roman Schoenauer, Stephan Lange, Alain Hirschy, Elisabeth Ehler, Jean-claude Perriard, Irina AgarkovaAbstract:The M-band is the cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. Apart from the myosin tails and the C-termini of titin, only two closely related structural proteins had been detected at the M-band so far, Myomesin and M-protein. However, electron microscopy studies revealed structural features that do not correlate with the expression of these two proteins, indicating the presence of unknown constituents in the M-band. Using comparative sequence analysis, we have identified a third member of this gene family, Myomesin 3, and characterised its biological properties. Myomesin 3 is predicted to consist of a unique head domain followed by a conserved sequence of either fibronectin- or immunoglobulin-like domains, similarly to Myomesin 3 and M-protein. While all three members of the Myomesin family are localised to the M-band of the sarcomere, each member shows its specific expression pattern. In contrast to Myomesin, which is ubiquitously expressed in all striated muscles, and M-protein, whose expression is restricted to adult heart and fast-twitch skeletal muscle, Myomesin 3 can be detected mainly in intermediate speed fibers of skeletal muscle. In analogy to Myomesin, Myomesin 3 targets to the M-band region of the sarcomere via its N-terminal part and forms homodimers via its C-terminal domain. However, despite the high degree of homology, no heterodimer between distinct members of the Myomesin gene family can be detected. We propose that each member of the Myomesin family is a component of one of the distinct ultrastructures, the M-lines, which modulate the mechanical properties of the M-bands in different muscle types.
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Molecular basis of the C-terminal tail-to-tail assembly of the sarcomeric filament protein Myomesin
The EMBO journal, 2007Co-Authors: Nikos Pinotsis, Stephan Lange, Dimitri I. Svergun, Jean-claude Perriard, Matthias WilmannsAbstract:Sarcomeric filament proteins display extraordinary properties in terms of protein length and mechanical elasticity, requiring specific anchoring and assembly mechanisms. To establish the molecular basis of terminal filament assembly, we have selected the sarcomeric M-band protein Myomesin as a prototypic filament model. The crystal structure of the Myomesin C-terminus, comprising a tandem array of two immunoglobulin (Ig) domains My12 and My13, reveals a dimeric end-to-end filament of 14.3 nm length. Although the two domains share the same fold, an unexpected rearrangement of one β-strand reveals how they are evolved into unrelated functions, terminal filament assembly (My13) and filament propagation (My12). The two domains are connected by a six-turn α-helix, of which two turns are void of any interactions with other protein parts. Thus, the overall structure of the assembled Myomesin C-terminus resembles a three-body beads-on-the-string model with potentially elastic properties. We predict that the found My12-helix-My13 domain topology may provide a structural template for the filament architecture of the entire C-terminal Ig domain array My9–My13 of Myomesin.
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The sarcomeric M-band during development and in disease.
Journal of muscle research and cell motility, 2006Co-Authors: Stephan Lange, Jean-claude Perriard, Irina Agarkova, Elisabeth EhlerAbstract:The C-terminus of connectin/titin at the M-band of the sarcomere interacts with several structural as well as potential signalling proteins. One of these is Myomesin, which can also bind to myosin and has been suggested to function as an integral structural linker of the thick filaments into the sarcomere. Recent evidence that Myomesin possesses the ability to form antiparallel dimers via its C-terminal domain has prompted us to propose a novel three-dimensional model for the sarcomeric M-band. A splice variant of Myomesin, termed EH-Myomesin, contains an additional segment that has disordered conformation and functions as an entropic spring. It is expressed in a subset of muscle types that are characterised by a broader operational range and are more resistant to damage caused by eccentric contraction. In addition, it is also re-expressed in dilated cardiomyopathy. DRAL/FHL-2 is another protein that interacts with the M-band portion of connectin/titin and which probably functions as an adaptor for the compartmentalisation of metabolic enzymes. Together these results suggest that the M-band is crucial for sarcomere function and maintenance and that its molecular composition can be adapted to divergent physiological needs in different muscle types, which may help to cope with pathological alterations.
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Study of the mechanical properties of Myomesin proteins using dynamic force spectroscopy.
Journal of molecular biology, 2005Co-Authors: Patricia Bertoncini, Roman Schoenauer, Jean-claude Perriard, Irina Agarkova, Martin Hegner, H.-j. GüntherodtAbstract:Myomesin is the most prominent structural component of the sarcomeric M-Band that is expressed in mammalian heart and skeletal muscles. Like titin, this protein is an intracellular member of the Ig-fibronectin superfamily, which has a flexible filamentous structure and which is largely composed of two types of domain that are similar to immunoglobulin (Ig)-like and fibronectin type III (FNIII) domains. Several Myomesin isoforms have been identified, and their expression patterns are highly regulated both spatially and temporally. Particularly, alternative splicing in the central part of the molecule gives rise to an isoform, EH (embryonic heart)-Myomesin, containing a serine and proline-rich insertion with no well-defined secondary structure, the EH segment. EH-Myomesin represents the major Myomesin isoform at embryonic stages of mammalian heart and is rapidly down-regulated around birth, but it is re-expressed in the heart of patients suffering from dilated cardio-myopathy. Here, in order to facilitate a better understanding of the physiological, and possibly pathological, functions of Myomesin proteins, we explore the mechanical stability, elasticity and force-driven structural changes of human Myomesin's sub-molecular segments using single-molecule force spectroscopy and protein engineering. We find that human Myomesin molecules are composed of modules (Ig and FNIII), that are designed to withstand force and we demonstrate that the human cardiac EH segment functions like an additional elastic stretch in the middle part of the EH-Myomesin and behaves like a random coil. Consequently Myomesin isoforms (proteins with or without the EH segment) have different elastic properties, the EH-Myomesin being the more compliant one. These findings imply that the compliance of the M-band increases with the amount of EH-Myomesin it contains. So, we provide the evidence that not only titin but also other sarcomeric proteins have complicated visco-elastic properties depending on the contractile parameters in different muscle types.
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Myomesin is a molecular spring with adaptable elasticity.
Journal of molecular biology, 2005Co-Authors: Roman Schoenauer, Jean-claude Perriard, Patricia Bertoncini, Martin Hegner, Gia Machaidze, Ueli Aebi, Irina AgarkovaAbstract:The M-band is a transverse structure in the center of the sarcomere, which is thought to stabilize the thick filament lattice. It was shown recently that the constitutive vertebrate M-band component Myomesin can form antiparallel dimers, which might cross-link the neighboring thick filaments. Myomesin consists mainly of immunoglobulin-like (Ig) and fibronectin type III (Fn) domains, while several muscle types express the EH-Myomesin splice isoform, generated by the inclusion of the unique EH-segment of about 100 amino acid residues (aa) in the center of the molecule. Here we use atomic force microscopy (AFM), transmission electron microscopy (TEM) and circular dichroism (CD) spectroscopy for the biophysical characterization of Myomesin. The AFM identifies the "mechanical fingerprints" of the modules constituting the Myomesin molecule. Stretching of homomeric polyproteins, constructed of Ig and Fn domains of human Myomesin, produces a typical saw-tooth pattern in the force-extension curve. The domains readily refold after relaxation. In contrast, stretching of a heterogeneous polyprotein, containing several repeats of the My6-EH fragment reveals a long initial plateau corresponding to the sum of EH-segment contour lengths, followed by several My6 unfolding peaks. According to this, the EH-segment is characterized as an entropic chain with a persistence length of about 0.3nm. In TEM pictures, the EH-domain appears as a gap in the molecule, indicating a random coil conformation similar to the PEVK region of titin. CD spectroscopy measurements support this result, demonstrating a mostly non-folded conformation for the EH-segment. We suggest that similarly to titin, Myomesin is a molecular spring, whose elasticity is modulated by alternative splicing. The Ig and Fn domains might function as reversible "shock absorbers" by sequential unfolding in the case of extremely high or long sustained stretching forces. These complex visco-elastic properties of Myomesin might be crucial for the stability of the sarcomere.
Dieter O. Fürst - One of the best experts on this subject based on the ideXlab platform.
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Dimerisation of Myomesin: implications for the structure of the sarcomeric M-band.
Journal of molecular biology, 2005Co-Authors: Stephan Lange, Jean-claude Perriard, Irina Agarkova, Daniel Auerbach, Dieter O. Fürst, Mirko Himmel, Katrin Hayess, Elisabeth EhlerAbstract:The sarcomeric M-band is thought to provide a link between the thick and the elastic filament systems. So far, relatively little is known about its structural components and their three-dimensional organisation. Myomesin seems to be an essential component of the M-band, since it is expressed in all types of vertebrate striated muscle fibres investigated and can be found in its mature localisation pattern as soon as the first myofibrils are assembled. Previous work has shown that the N-terminal and central part of Myomesin harbour binding sites for myosin, titin and muscle creatine kinase. Intrigued by the highly conserved domain layout of the C-terminal half, we screened for new interaction partners by yeast two-hybrid analysis. This revealed a strong interaction of Myomesin with itself. This finding was confirmed by several biochemical assays. Our data suggest that Myomesin can form antiparallel dimers via a binding site residing in its C-terminal domain 13. We suggest that, similar to alpha-actinin in the Z-disc, the Myomesin dimers cross-link the contractile filaments in the M-band. The new and the already previously identified Myomesin interaction sites are integrated into the first three-dimensional model of the sarcomeric M-band on a molecular basis.
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Muscle-type Creatine Kinase Interacts with Central Domains of the M-band Proteins Myomesin and M-protein
Journal of molecular biology, 2003Co-Authors: Thorsten Hornemann, Dieter O. Fürst, Mirko Himmel, Katrin Hayess, Stefan Kempa, Theo WallimannAbstract:Muscle-type creatine kinase (MM-CK) is a member of the CK isoenzyme family with key functions in cellular energetics. MM-CK interacts in an isoform-specific manner with the M-band of sarcomeric muscle, where it serves as an efficient intramyofibrillar ATP-regenerating system for the actin-activated myosin ATPase located nearby on both sides of the M-band. Four MM-CK-specific and highly conserved lysine residues are thought to be responsible for the interaction of MM-CK with the M-band. A yeast two-hybrid screen led to the identification of MM-CK as a binding partner of a central portion of Myomesin (My7-8). An interaction was observed with domains six to eight of the closely related M-protein but not with several other Ig-like domains, including an M-band domain, of titin. The observed interactions were corroborated and characterised in detail by surface plasmon resonance spectroscopy (BiaCore). In both cases, they were CK isoform-specific and the MM-CK-specific lysine residues (K8. K24, K104 and K115) are involved in this interaction. At pH 6.8, the dissociation constants for the Myomesin/MM-CK and the M-protein/MM-CK binding were in the range of 50-100 nM and around 1 microM, respectively. The binding showed pronounced pH-dependence and indicates a dynamic association/dissociation behaviour, which most likely depends on the energy state of the muscle. Our data propose a simple model for the regulation of this dynamic interaction.
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M band proteins Myomesin and skelemin are encoded by the same gene: analysis of its organization and expression.
Genomics, 1999Co-Authors: Frank Steiner, Klaus Weber, Dieter O. FürstAbstract:The complete exon-intron organization of the murine gene encoding sarcomeric Myomesin has been determined. The gene is composed of 38 exons and 37 introns, spanning approximately 105 kb of DNA. Intron positions and phases are essentially identical to those identified in M-protein. They are related to the modular structure of Myomesin, which is composed almost entirely of immunoglobulin and fibronectin type III domains. Nearly all repeats follow a two exon-one domain structure. The start and end of each domain are defined by introns in phase I, while internal introns are more divergent in position and very rarely use phase I. Genomic Southern blotting and reverse transcription-polymerase chain reaction revealed that differential splicing of a single exon gives rise to two polypeptides, described in the literature as Myomesin and skelemin, respectively. A single transcriptional start point was detected in both skeletal and cardiac muscle. Analysis of the presumptive promoter region revealed several potential regulatory elements. CAT expression assays using promoter deletion constructs identified three regions that seem to be important for the muscle-specific transcriptional activation of the Myomesin gene. These results provide the basis for a comparative analysis of the regulation of Myomesin and M-protein genes in vivo.
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Expression of sarcomeric proteins and assemblyof myofibrils in the putative myofibroblast cell line BHK-21/C13
Journal of Muscle Research & Cell Motility, 1998Co-Authors: Peter F.m. Van Der Ven, Dieter O. FürstAbstract:The expression and organization patterns of several myofibrillar proteins were analysed in the putative myofibroblast cell line BHK-21/C13. Although this cell line originates from renal tissue, the majority of the cells express titin. In these cells, titin is, under standard culture conditions, detected in myofibril-like structures (MLSs), where it alternates with non-muscle myosin (NMM). Expression of sarcomeric myosin heavy chain (sMyHC) is observed in a small minority of cells, while other sarcomeric proteins, such as nebulin, myosin binding protein C (MyBP-C), Myomesin and M-protein are not expressed at all. By changing the culture conditions in a way equal to conditions that induce differentiation of skeletal muscle cells, a process reminiscent of sarcomerogenesis in vitro is induced. Within one day after the switch to a low-nutrition medium, myofibrillar proteins can be detected in a subset of cells, and after two to five days, all myofibrillar proteins examined are organized in typical sarcomeric patterns. Frequently, cross-striations are visible with phase contrast optics. Transfection of these cells with truncated Myomesin fragments showed that a specific part of the Myomesin molecule, known to contain a titin-binding site, binds to MLSs, whereas other parts do not. These results demonstrate that this cell line could serve as a powerful model to study the assembly of myofibrils. At the same time, its transfectability offers an invaluable tool for in vivo studies concerning binding properties of sarcomeric proteins. © Kluwer Academic Publishers.
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Expression of sarcomeric proteins and assembly of myofibrils in the putative myofibroblast cell line BHK-21/C13.
Journal of muscle research and cell motility, 1998Co-Authors: Peter F.m. Van Der Ven, Dieter O. FürstAbstract:The expression and organization patterns of several myofibrillar proteins were analysed in the putative myofibroblast cell line BHK-21/C13. Although this cell line originates from renal tissue, the majority of the cells express titin. In these cells, titin is, under standard culture conditions, detected in myofibril-like structures (MLSs), where it alternates with non-muscle myosin (NMM). Expression of sarcomeric myosin heavy chain (sMyHC) is observed in a small minority of cells, while other sarcomeric proteins, such as nebulin, myosin binding protein C (MyBP-C), Myomesin and M-protein are not expressed at all. By changing the culture conditions in a way equal to conditions that induce differentiation of skeletal muscle cells, a process reminiscent of sarcomerogenesis in vitro is induced. Within one day after the switch to a low-nutrition medium, myofibrillar proteins can be detected in a subset of cells, and after two to five days, all myofibrillar proteins examined are organized in typical sarcomeric patterns. Frequently, cross-striations are visible with phase contrast optics. Transfection of these cells with truncated Myomesin fragments showed that a specific part of the Myomesin molecule, known to contain a titin-binding site, binds to MLSs, whereas other parts do not. These results demonstrate that this cell line could serve as a powerful model to study the assembly of myofibrils. At the same time, its transfectability offers an invaluable tool for in vivo studies concerning binding properties of sarcomeric proteins.
Irina Agarkova - One of the best experts on this subject based on the ideXlab platform.
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The M-Band: Not Just Inert Glue but Playing an Active Role in the Middle of the Sarcomere
Cardiac Cytoarchitecture, 2015Co-Authors: Irina Agarkova, Elisabeth EhlerAbstract:The M-band is the region in the middle of the sarcomere that holds the thick (myosin) filaments in place by linking them to the elastic filament system made up of titin. It was recently suggested to play an important role by averaging the lateral misbalances of thick filament forces in the activated sarcomere and to actively support titin to restore the lateral order in the sarcomere. Its marker constituent in vertebrates is Myomesin, but the rest of its molecular composition depends on the developmental stage and type of striated muscle and eventually results in a more rigid or a more elastic phenotype. The studies of Myomesin domain interactions suggest that thick filaments might be cross-linked in their central “bare” zone by antiparallel Myomesin dimers that bind myosin with their N-terminal domain and interact end to end with their C-terminal domains. In addition to its role in buffering active contractile force, the M-band is the origin of signalling processes that can go all the way to the nucleus to affect gene transcription. The mechanical deformations of the M-band filaments during muscle contraction allow the integration of smart molecular sensors to monitor the activity of the sarcomere and initiate physiological adaptations. While it is known that the composition of the M-band is altered in cardiomyopathy, only few mutations in M-band components were characterised so far that lead to hereditary cardiomyopathy, but results obtained from next-generation sequencing are bound to expand on this.
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ARTICLE IN PRESS doi:10.1016/j.jmb.2005.03.040 J. Mol. Biol. (xxxx) xx, 1–11 Study of the Mechanical Properties of Myomesin Proteins Using Dynamic Force Spectroscopy
2013Co-Authors: Patricia Bertoncini, Roman Schoenauer, Irina Agarkova, Martin Hegner, -c. J. Perriard, -j. H. GüntherodtAbstract:Myomesin is the most prominent structural component of the sarcomeric M-Band that is expressed in mammalian heart and skeletal muscles. Like titin, this protein is an intracellular member of the Ig-fibronectin superfamily, which has a flexible filamentous structure and which is largely composed of two types of domain that are similar to immunoglobulin (Ig)-like and fibronectin type III (FNIII) domains. Several Myomesin isoforms have been identified, and their expression patterns are highly regulated both spatially and temporally. Particularly, alternative splicing in the central part of the molecule gives rise to an isoform, EH (embryonic heart)-Myomesin, containing a serine and proline-rich insertion with no well-defined secondary structure, the EH segment. EH-Myomesin represents the major Myomesin isoform at embryonic stages of mammalian heart and is rapidly down-regulated around birth, but it is re-expressed in the heart of patients suffering from dilated cardio-myopathy. Here, in order to facilitate a better understanding of the physiological, and possibl
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ORIGINAL CONTRIBUTION
2013Co-Authors: Roman Schoenauer, Elisabeth Ehler, Maximilian Y. Emmert, Allison Felley, Benedikt Weber, Mohamed Nemir, Thierry Pedrazzini, Volkmar Falk, Simon P. Hoerstrup, Irina AgarkovaAbstract:EH-Myomesin splice isoform is a novel marker for dilated cardiomyopath
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Myomesin 3 a novel structural component of the m band in striated muscle
Journal of Molecular Biology, 2008Co-Authors: Roman Schoenauer, Stephan Lange, Alain Hirschy, Elisabeth Ehler, Jean-claude Perriard, Irina AgarkovaAbstract:The M-band is the cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. Apart from the myosin tails and the C-termini of titin, only two closely related structural proteins had been detected at the M-band so far, Myomesin and M-protein. However, electron microscopy studies revealed structural features that do not correlate with the expression of these two proteins, indicating the presence of unknown constituents in the M-band. Using comparative sequence analysis, we have identified a third member of this gene family, Myomesin 3, and characterised its biological properties. Myomesin 3 is predicted to consist of a unique head domain followed by a conserved sequence of either fibronectin- or immunoglobulin-like domains, similarly to Myomesin 3 and M-protein. While all three members of the Myomesin family are localised to the M-band of the sarcomere, each member shows its specific expression pattern. In contrast to Myomesin, which is ubiquitously expressed in all striated muscles, and M-protein, whose expression is restricted to adult heart and fast-twitch skeletal muscle, Myomesin 3 can be detected mainly in intermediate speed fibers of skeletal muscle. In analogy to Myomesin, Myomesin 3 targets to the M-band region of the sarcomere via its N-terminal part and forms homodimers via its C-terminal domain. However, despite the high degree of homology, no heterodimer between distinct members of the Myomesin gene family can be detected. We propose that each member of the Myomesin family is a component of one of the distinct ultrastructures, the M-lines, which modulate the mechanical properties of the M-bands in different muscle types.
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The sarcomeric M-band during development and in disease.
Journal of muscle research and cell motility, 2006Co-Authors: Stephan Lange, Jean-claude Perriard, Irina Agarkova, Elisabeth EhlerAbstract:The C-terminus of connectin/titin at the M-band of the sarcomere interacts with several structural as well as potential signalling proteins. One of these is Myomesin, which can also bind to myosin and has been suggested to function as an integral structural linker of the thick filaments into the sarcomere. Recent evidence that Myomesin possesses the ability to form antiparallel dimers via its C-terminal domain has prompted us to propose a novel three-dimensional model for the sarcomeric M-band. A splice variant of Myomesin, termed EH-Myomesin, contains an additional segment that has disordered conformation and functions as an entropic spring. It is expressed in a subset of muscle types that are characterised by a broader operational range and are more resistant to damage caused by eccentric contraction. In addition, it is also re-expressed in dilated cardiomyopathy. DRAL/FHL-2 is another protein that interacts with the M-band portion of connectin/titin and which probably functions as an adaptor for the compartmentalisation of metabolic enzymes. Together these results suggest that the M-band is crucial for sarcomere function and maintenance and that its molecular composition can be adapted to divergent physiological needs in different muscle types, which may help to cope with pathological alterations.
Elisabeth Ehler - One of the best experts on this subject based on the ideXlab platform.
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Myofilament Remodeling and Function Is More Impaired in Peripartum Cardiomyopathy Compared with Dilated Cardiomyopathy and Ischemic Heart Disease
The American journal of pathology, 2017Co-Authors: Ilse A. E. Bollen, Elisabeth Ehler, Karin Fleischanderl, Floor Bouwman, Lanette Kempers, Melanie Ricke-hoch, Denise Hilfiker-kleiner, Cristobal G. Dos Remedios, Martina Krüger, Aryan VinkAbstract:Peripartum cardiomyopathy (PPCM) and dilated cardiomyopathy (DCM) show similarities in clinical presentation. However, although DCM patients do not recover and slowly deteriorate further, PPCM patients show either a fast cardiac deterioration or complete recovery. The aim of this study was to assess if underlying cellular changes can explain the clinical similarities and differences in the two diseases. We, therefore, assessed sarcomeric protein expression, modification, titin isoform shift, and contractile behavior of cardiomyocytes in heart tissue of PPCM and DCM patients and compared these with nonfailing controls. Heart samples from ischemic heart disease (ISHD) patients served as heart failure control samples. Passive force was only increased in PPCM samples compared with controls, whereas PPCM, DCM, and ISHD samples all showed increased myofilament Ca 2+ sensitivity. Length-dependent activation was significantly impaired in PPCM compared with controls, no impairment was observed in ISHD samples, and DCM samples showed an intermediate response. Contractile impairments were caused by impaired protein kinase A (PKA)–mediated phosphorylation because exogenous PKA restored all parameters to control levels. Although DCM samples showed reexpression of EH-Myomesin, an isoform usually only expressed in the heart before birth, PPCM and ISHD did not. The lack of EH-Myomesin, combined with low PKA-mediated phosphorylation of myofilament proteins and increased compliant titin isoform, may explain the increase in passive force and blunted length-dependent activation of myofilaments in PPCM samples.
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The M-Band: Not Just Inert Glue but Playing an Active Role in the Middle of the Sarcomere
Cardiac Cytoarchitecture, 2015Co-Authors: Irina Agarkova, Elisabeth EhlerAbstract:The M-band is the region in the middle of the sarcomere that holds the thick (myosin) filaments in place by linking them to the elastic filament system made up of titin. It was recently suggested to play an important role by averaging the lateral misbalances of thick filament forces in the activated sarcomere and to actively support titin to restore the lateral order in the sarcomere. Its marker constituent in vertebrates is Myomesin, but the rest of its molecular composition depends on the developmental stage and type of striated muscle and eventually results in a more rigid or a more elastic phenotype. The studies of Myomesin domain interactions suggest that thick filaments might be cross-linked in their central “bare” zone by antiparallel Myomesin dimers that bind myosin with their N-terminal domain and interact end to end with their C-terminal domains. In addition to its role in buffering active contractile force, the M-band is the origin of signalling processes that can go all the way to the nucleus to affect gene transcription. The mechanical deformations of the M-band filaments during muscle contraction allow the integration of smart molecular sensors to monitor the activity of the sarcomere and initiate physiological adaptations. While it is known that the composition of the M-band is altered in cardiomyopathy, only few mutations in M-band components were characterised so far that lead to hereditary cardiomyopathy, but results obtained from next-generation sequencing are bound to expand on this.
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ORIGINAL CONTRIBUTION
2013Co-Authors: Roman Schoenauer, Elisabeth Ehler, Maximilian Y. Emmert, Allison Felley, Benedikt Weber, Mohamed Nemir, Thierry Pedrazzini, Volkmar Falk, Simon P. Hoerstrup, Irina AgarkovaAbstract:EH-Myomesin splice isoform is a novel marker for dilated cardiomyopath
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EH-Myomesin splice isoform is a novel marker for dilated cardiomyopathy
Basic Research in Cardiology, 2011Co-Authors: Roman Schoenauer, Elisabeth Ehler, Maximilian Y. Emmert, Allison Felley, Chad Brokopp, Benedikt Weber, Mohamed Nemir, Giuseppe G. Faggian, Thierry Pedrazzini, Volkmar FalkAbstract:The M-band is the prominent cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. To investigate M-band alterations in heart disease, we analyzed the expression of its main components, proteins of the Myomesin family, in mouse and human cardiomyopathy. Cardiac function was assessed by echocardiography and compared to the expression pattern of Myomesins evaluated with RT-PCR, Western blot, and immunofluorescent analysis. Disease progression in transgenic mouse models for dilated cardiomyopathy (DCM) was accompanied by specific M-band alterations. The dominant splice isoform in the embryonic heart, EH-Myomesin, was strongly up-regulated in the failing heart and correlated with a decrease in cardiac function ( R = −0.86). In addition, we have analyzed the expressions of Myomesins in human myocardial biopsies ( N = 40) obtained from DCM patients, DCM patients supported by a left ventricular assist device (LVAD), hypertrophic cardiomyopathy (HCM) patients and controls. Quantitative RT-PCR revealed that the EH-Myomesin isoform was up-regulated 41-fold ( P
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eh Myomesin splice isoform is a novel marker for dilated cardiomyopathy
Basic Research in Cardiology, 2011Co-Authors: Roman Schoenauer, Elisabeth Ehler, Maximilian Y. Emmert, Allison Felley, Chad Brokopp, Benedikt Weber, Mohamed Nemir, Giuseppe G. Faggian, Thierry Pedrazzini, Volkmar FalkAbstract:The M-band is the prominent cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. To investigate M-band alterations in heart disease, we analyzed the expression of its main components, proteins of the Myomesin family, in mouse and human cardiomyopathy. Cardiac function was assessed by echocardiography and compared to the expression pattern of Myomesins evaluated with RT-PCR, Western blot, and immunofluorescent analysis. Disease progression in transgenic mouse models for dilated cardiomyopathy (DCM) was accompanied by specific M-band alterations. The dominant splice isoform in the embryonic heart, EH-Myomesin, was strongly up-regulated in the failing heart and correlated with a decrease in cardiac function (R = −0.86). In addition, we have analyzed the expressions of Myomesins in human myocardial biopsies (N = 40) obtained from DCM patients, DCM patients supported by a left ventricular assist device (LVAD), hypertrophic cardiomyopathy (HCM) patients and controls. Quantitative RT-PCR revealed that the EH-Myomesin isoform was up-regulated 41-fold (P < 0.001) in the DCM patients compared to control patients. In DCM hearts supported by a LVAD and HCM hearts, the EH-Myomesin expression was comparable to controls. Immunofluorescent analyses indicate that EH-Myomesin was enhanced in a cell-specific manner, leading to a higher heterogeneity of the myocytes’ cytoskeleton through the myocardial wall. We suggest that the up-regulation of EH-Myomesin denotes an adaptive remodeling of the sarcomere cytoskeleton in the dilated heart and might serve as a marker for DCM in mouse and human myocardium.
Stephan Lange - One of the best experts on this subject based on the ideXlab platform.
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Obscurin determines the architecture of the longitudinal sarcoplasmic reticulum
Journal of Cell Science, 2009Co-Authors: Stephan Lange, Kunfu Ouyang, Li Cui, Hongqiang Cheng, Richard L Lieber, Gretchen A. Meyer, Ju ChenAbstract:The giant protein obscurin is thought to link the sarcomere with the sarcoplasmic reticulum (SR). The N-terminus of obscurin interacts with the M-band proteins titin and Myomesin, whereas the C-terminus mediates interactions with ankyrin proteins. Here, we investigate the importance of obscurin for SR architecture and organization. Lack of obscurin in cross-striated muscles leads to changes in longitudinal SR architecture and disruption of small ankyrin-1.5 (sAnk1.5) expression and localization. Changes in SR architecture in obscurin knockout mice are also associated with alterations in several SR or SR-associated proteins, such as ankyrin-2 and β-spectrin. Finally, obscurin knockout mice display centralized nuclei in skeletal muscles as a sign of mild myopathy, but have normal sarcomeric structure and preserved muscle function.
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Obscurin determines the architecture of the longitudinal sarcoplasmic reticulum.
Journal of cell science, 2009Co-Authors: Stephan Lange, Kunfu Ouyang, Gretchen Meyer, Li Cui, Hongqiang Cheng, Richard L Lieber, Ju ChenAbstract:The giant protein obscurin is thought to link the sarcomere with the sarcoplasmic reticulum (SR). The N-terminus of obscurin interacts with the M-band proteins titin and Myomesin, whereas the C-terminus mediates interactions with ankyrin proteins. Here, we investigate the importance of obscurin for SR architecture and organization. Lack of obscurin in cross-striated muscles leads to changes in longitudinal SR architecture and disruption of small ankyrin-1.5 (sAnk1.5) expression and localization. Changes in SR architecture in obscurin knockout mice are also associated with alterations in several SR or SR-associated proteins, such as ankyrin-2 and beta-spectrin. Finally, obscurin knockout mice display centralized nuclei in skeletal muscles as a sign of mild myopathy, but have normal sarcomeric structure and preserved muscle function.
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Interactions with titin and Myomesin target obscurin and obscurin-like 1 to the M-band: implications for hereditary myopathies.
Journal of cell science, 2008Co-Authors: Atsushi Fukuzawa, Stephan Lange, Mark R. Holt, Anna Vihola, Virginie Carmignac, Ana Ferreiro, Bjarne Udd, Mathias GautelAbstract:Obscurin, a giant modular muscle protein implicated in G-protein and protein-kinase signalling, can localize to both sarcomeric Z-disks and M-bands. Interaction of obscurin with the Z-disk is mediated by Z-disk titin. Here, we unravel the molecular basis for the unusual localization of obscurin, a Z-disk-associated protein, to the M-band, where its invertebrate analogue UNC-89 is also localized. The first three domains of the N-terminus of obscurin bind to the most C-terminal domain of M-band titin, as well as to the M-band protein Myomesin. Both proteins also interact with the N-terminal domains of obscurin-like 1 (Obsl1), a small homologue of obscurin. Downregulation of Myomesin by siRNA interference disrupts obscurin-M-band integration in neonatal cardiomyocytes, as does overexpression of the binding sites on either Myomesin, obscurin or Obsl1. Furthermore, all titin mutations that have been linked to limb-girdle muscular dystrophy 2J (LGMD2J) or Salih myopathy weaken or abrogate titin-obscurin and titin-Obsl1 binding, and lead to obscurin mislocalization, suggesting that interference with the interaction of these proteins might be of pathogenic relevance for human disease.
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Myomesin 3 a novel structural component of the m band in striated muscle
Journal of Molecular Biology, 2008Co-Authors: Roman Schoenauer, Stephan Lange, Alain Hirschy, Elisabeth Ehler, Jean-claude Perriard, Irina AgarkovaAbstract:The M-band is the cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. Apart from the myosin tails and the C-termini of titin, only two closely related structural proteins had been detected at the M-band so far, Myomesin and M-protein. However, electron microscopy studies revealed structural features that do not correlate with the expression of these two proteins, indicating the presence of unknown constituents in the M-band. Using comparative sequence analysis, we have identified a third member of this gene family, Myomesin 3, and characterised its biological properties. Myomesin 3 is predicted to consist of a unique head domain followed by a conserved sequence of either fibronectin- or immunoglobulin-like domains, similarly to Myomesin 3 and M-protein. While all three members of the Myomesin family are localised to the M-band of the sarcomere, each member shows its specific expression pattern. In contrast to Myomesin, which is ubiquitously expressed in all striated muscles, and M-protein, whose expression is restricted to adult heart and fast-twitch skeletal muscle, Myomesin 3 can be detected mainly in intermediate speed fibers of skeletal muscle. In analogy to Myomesin, Myomesin 3 targets to the M-band region of the sarcomere via its N-terminal part and forms homodimers via its C-terminal domain. However, despite the high degree of homology, no heterodimer between distinct members of the Myomesin gene family can be detected. We propose that each member of the Myomesin family is a component of one of the distinct ultrastructures, the M-lines, which modulate the mechanical properties of the M-bands in different muscle types.
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Molecular basis of the C-terminal tail-to-tail assembly of the sarcomeric filament protein Myomesin
The EMBO journal, 2007Co-Authors: Nikos Pinotsis, Stephan Lange, Dimitri I. Svergun, Jean-claude Perriard, Matthias WilmannsAbstract:Sarcomeric filament proteins display extraordinary properties in terms of protein length and mechanical elasticity, requiring specific anchoring and assembly mechanisms. To establish the molecular basis of terminal filament assembly, we have selected the sarcomeric M-band protein Myomesin as a prototypic filament model. The crystal structure of the Myomesin C-terminus, comprising a tandem array of two immunoglobulin (Ig) domains My12 and My13, reveals a dimeric end-to-end filament of 14.3 nm length. Although the two domains share the same fold, an unexpected rearrangement of one β-strand reveals how they are evolved into unrelated functions, terminal filament assembly (My13) and filament propagation (My12). The two domains are connected by a six-turn α-helix, of which two turns are void of any interactions with other protein parts. Thus, the overall structure of the assembled Myomesin C-terminus resembles a three-body beads-on-the-string model with potentially elastic properties. We predict that the found My12-helix-My13 domain topology may provide a structural template for the filament architecture of the entire C-terminal Ig domain array My9–My13 of Myomesin.
