The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Denise Paulin - One of the best experts on this subject based on the ideXlab platform.
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Synemin-related skeletal and cardiac myopathies: an overview of pathogenic variants.
American journal of physiology. Cell physiology, 2020Co-Authors: Denise Paulin, Onnik Agbulut, Yeranuhi Hovhannisyan, Serdar Kasakyan, Zhigang XueAbstract:This review analyzes data concerning patients with cardiomyopathies or skeletal myopathies associated with a variation in the intermediate filament (IF) Synemin gene (SYNM), also referred to as desmuslin (DMN). Molecular studies demonstrate that Synemin copolymerizes with desmin and vimentin IF and interacts with vinculin, α-actinin, α-dystrobrevin, dystrophin, talin, and zyxin. It has been found that Synemin is an A-kinase-anchoring protein (AKAP) that anchors protein kinase A (PKA) and modulates the PKA-dependent phosphorylation of several cytoskeletal substrates such as desmin. Because several IF proteins, including desmin, have been implicated in human genetic disorders such as dominant or recessive congenital and adult-onset myopathy, Synemin becomes a significant candidate for cardiac and skeletal myopathies of unknown etiology. Because SYNM is a new candidate gene that displays numerous sequence polymorphisms, in this review, we summarize the genetic and clinical literature about SYNM mutations. Protein-changing variants (missense, frameshifts, nonsense) were further evaluated based on structural modifications and amino acid interactions. We present in silico modeling of helical salt-bridges between residues to evaluate the impact of the Synemin networks crucial to interactions with cytoskeletal proteins. Finally, a discussion is featured regarding certain variants that may contribute to the disease state.
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Synemin acts as a regulator of signalling molecules during skeletal muscle hypertrophy
Journal of Cell Science, 2014Co-Authors: A Parlakian, Denise Paulin, Dario Coletti, Sonia Alonso-martin, Christophe Hourde, Pierre Joanne, Jacqueline Gao-li, Jocelyne Blanc, Arnaud Ferry, Zhigang XueAbstract:Synemin, a type IV intermediate filament (IF) protein, forms a bridge between IFs and cellular membranes. As an A-kinase-anchoring protein, it also provides temporal and spatial targeting of protein kinase A (PKA). However, little is known about its functional roles in either process. To better understand its functions in muscle tissue, we generated Synemin-deficient (Synm(-/-)) mice. Synm(-/-) mice displayed normal development and fertility but showed a mild degeneration and regeneration phenotype in myofibres and defects in sarcolemma membranes. Following mechanical overload, Synm(-/-) mice muscles showed a higher hypertrophic capacity with increased maximal force and fatigue resistance compared with control mice. At the molecular level, increased remodelling capacity was accompanied by decreased myostatin (also known as GDF8) and atrogin (also known as FBXO32) expression, and increased follistatin expression. Furthermore, the activity of muscle-mass control molecules (the PKA RII alpha subunit, p70S6K and CREB1) was increased in mutant mice. Finally, analysis of muscle satellite cell behaviour suggested that the absence of Synemin could affect the balance between self-renewal and differentiation of these cells. Taken together, our results show that Synemin is necessary to maintain membrane integrity and regulates signalling molecules during muscle hypertrophy.
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Dynamic expression of Synemin isoforms in mouse embryonic stem cells and neural derivatives
BMC Cell Biology, 2011Co-Authors: Sheila C De Souza Martins, Denise Paulin, Onnik Agbulut, Nicolas Diguet, Jean-christophe Larcher, Bruna S Paulsen, Stevens K Rehen, Vivaldo Moura-neto, Zhigang XueAbstract:Background Intermediate filaments (IFs) are major components of the mammalian cytoskeleton and expressed in cell-type-specific patterns. Morphological changes during cell differentiation are linked to IF network remodeling. However, little is known concerning the presence and the role of IFs in embryonic stem (ES) cells and during their differentiation. Results We have examined the expression profile of Synemin isoforms in mouse pluripotent ES cells and during their neural differentiation induced by retinoic acid. Using RT-PCR, Western blotting and immunostaining, we show that Synemin M is present at both mRNA and protein levels in undifferentiated ES cells as early as pluripotency factor Oct-3/4 and IF keratin 8. Synemin H was produced only in neural precursors when neural differentiation started, concurrently with Synemin M, nestin and glial fibrillary acidic protein. However, both Synemin H and M were restricted to the progenitor line during the neural differentiation program. Our in vivo analysis also confirmed the expression of Synemins H/M in multipotent neural stem cells in the subventricular zone of the adult brain, a neurogenic germinal niche of the mice. Knocking down Synemin in ES cells by shRNA lentiviral particles transduction has no influence on expression of Oct4, Nanog and SOX2, but decreased keratin 8 expression. Conclusions Our study shows a developmental stage specific regulation of Synemin isoforms in ES cells and its neural derivatives. These findings represent the first evidence that Synemins could potentially be useful markers for distinguishing multipotent ES cells from undifferentiated neural stem cells and more committed progenitor cells.
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Dynamic expression of Synemin isoforms in mouse embryonic stem cells and neural derivatives.
BMC cell biology, 2011Co-Authors: Sheila C De Souza Martins, Denise Paulin, Onnik Agbulut, Nicolas Diguet, Jean-christophe Larcher, Bruna S Paulsen, Stevens K Rehen, Vivaldo Moura-neto, Zhigang XueAbstract:Intermediate filaments (IFs) are major components of the mammalian cytoskeleton and expressed in cell-type-specific patterns. Morphological changes during cell differentiation are linked to IF network remodeling. However, little is known concerning the presence and the role of IFs in embryonic stem (ES) cells and during their differentiation. We have examined the expression profile of Synemin isoforms in mouse pluripotent ES cells and during their neural differentiation induced by retinoic acid. Using RT-PCR, Western blotting and immunostaining, we show that Synemin M is present at both mRNA and protein levels in undifferentiated ES cells as early as pluripotency factor Oct-3/4 and IF keratin 8. Synemin H was produced only in neural precursors when neural differentiation started, concurrently with Synemin M, nestin and glial fibrillary acidic protein. However, both Synemin H and M were restricted to the progenitor line during the neural differentiation program. Our in vivo analysis also confirmed the expression of Synemins H/M in multipotent neural stem cells in the subventricular zone of the adult brain, a neurogenic germinal niche of the mice. Knocking down Synemin in ES cells by shRNA lentiviral particles transduction has no influence on expression of Oct4, Nanog and SOX2, but decreased keratin 8 expression. Our study shows a developmental stage specific regulation of Synemin isoforms in ES cells and its neural derivatives. These findings represent the first evidence that Synemins could potentially be useful markers for distinguishing multipotent ES cells from undifferentiated neural stem cells and more committed progenitor cells.
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Desmin mutations in the terminal consensus motif prevent Synemin-desmin heteropolymer filament assembly.
Experimental cell research, 2011Co-Authors: Oussama Chourbagi, Denise Paulin, Patrick Vicart, Francine Bruston, Marianna Carinci, Zhigang Xue, Onnik AgbulutAbstract:Disorganization of the desmin network is associated with cardiac and skeletal myopathies characterized by accumulation of desmin-containing aggregates in the cells. Multiple associations of intermediate filament proteins form a network to increase mechanical and functional stability. Synemin is a desmin-associated type VI intermediate filament protein. Neither its impact on desmin network nor how it integrates into desmin filament is yet elucidated. To gain more insight into the molecular basis of these processes, we coexpressed Synemin with different desmin mutants in ex vivo models. The screening of fourteen desmin mutants showed that Synemin with desmin mutants revealed two behaviors. Firstly, Synemin was co-localized in desmin aggregates and its coexpression decreased the number of cells containing aggregates. Secondly, Synemin was excluded from the aggregates, then Synemin had no effect on desmin network organization. Among fourteen desmin mutants, there were only three mutants, p.E401K, p.R406W and p.E413K, in which Synemin was not found in aggregates. This behavior was correlated to the abnormal salt-bridges of desmin-dimer as seen in silico constructs. Moreover, desmin constructs in silico and published results in literature have predicted that the salt-bridges absence in the desmin filament building prevent longitudinal annealing and/or radial compaction. These results suggest that the state of desmin-filament assembly is crucial for Synemin anchorage and consequently might involve mechanical and functional stability of the cytoskeletal network.
Omar Skalli - One of the best experts on this subject based on the ideXlab platform.
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The cytoskeleton meets the skeleton. Focus on "Deficiency of the intermediate filament Synemin reduces bone mass in vivo".
American journal of physiology. Cell physiology, 2016Co-Authors: Omar SkalliAbstract:in an accompanying article in the current issue of the American Journal of Physiology: Cell Physiology , Moorer and colleagues (6a) put the limelight on Synemin, which is one of the 70 intermediate filament (IF) proteins, by demonstrating that Synemin knockout mice exhibit a substantial reduction in
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Synemin: Molecular Features and the Use of Proximity Ligation Assay to Study Its Interactions.
Methods in enzymology, 2015Co-Authors: Madhumita Paul, Omar SkalliAbstract:Synemin has three splice variants (α, β, and L) with identical head and rod domains but with tail domains of varying size. α- and β-Synemin are larger than most intermediate filament proteins (1565 and 1253 amino acids, respectively) but L-Synemin is shorter (339 amino acids). Synemin isoforms do not self-assemble into filaments but can copolymerize with vimentin and desmin. Synemin is present in all muscle cell types, in a few neural cell types, and in various other nonepithelial cell types. Synemin expression is regulated, sometimes in an isoform-specific manner, during development of the nervous system, in brain and breast cancer cells and during injuries to the brain and liver. Mice-lacking Synemin develop a myopathic phenotype, possibly due to Synemin role in linking desmin filaments to costameres and sarcomeres. Synemin may play this role through its demonstrated binding to costameric and sarcolemmal proteins, such as α-actinin, vinculin, and members of the dystroglycan complex. In astrocytoma cells, Synemin regulates proliferation by interacting with PP2A to modulate Akt phosphorylation status. Methods to identify Synemin binding partners are central to understand the roles of this protein in diverse cell types. Here, we describe how to use proximal ligation assays (PLA) for this purpose. PLA complement biochemical methods such as immunoprecipitation by relying on the use of antibodies conjugated to oligonucleotide probes to visualize by fluorescence microscopy protein-protein interactions in cells and tissues.
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The FASEB Journal • Research Communication
2013Co-Authors: Yihang Pan, Runfeng Jing, Aaron Pitre, Briana Jill Williams, Omar SkalliAbstract:Intermediate filament protein Synemin contributes to the migratory properties of astrocytoma cells by influencing the dynamics of the actin cytoskeleto
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© 2010 Molecular Vision
2013Co-Authors: Gabriel Luna, Omar Skalli, Geoffrey P. Lewis, Christopher D. Banna, Steven K. FisherAbstract:Expression profiles of nestin and Synemin in reactive astrocytes and Müller cells following retinal injury: a comparison with glial fibrillar acidic protein and vimenti
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Synemin is expressed in reactive astrocytes and Rosenthal fibers in Alexander disease
APMIS : acta pathologica microbiologica et immunologica Scandinavica, 2013Co-Authors: Tulen Pekny, Omar Skalli, Ulrika Wilhelmsson, Maryam Faiz, Maurice A. Curtis, Radoslav Matej, Milos PeknyAbstract:Alexander disease (AxD) is a neurodegenerative disorder with prominent white matter degeneration and the presence of Rosenthal fibers containing aggregates of glial fibrillary acidic protein (GFAP), and small stress proteins HSP27 and αB-crystallin, and widespread reactive gliosis. AxD is caused by mutations in GFAP, the main astrocyte intermediate filament protein. We previously showed that intermediate filament protein Synemin is upregulated in reactive astrocytes after neurotrauma. Here, we examined immunohistochemically the presence of Synemin in reactive astrocytes and Rosenthal fibers in two patients with AxD. There was an abundance of GFAP-positive Rosenthal fibers and widespread reactive gliosis in the white matter and subpial regions. Many of the GFAP-positive reactive astrocytes were positive for Synemin, and Synemin was also present in Rosenthal fibers. We show that Synemin is expressed in reactive astrocytes in AxD, and is also present in Rosenthal fibers. The potential role of Synemin in AxD pathogenesis remains to be investigated.
Zhigang Xue - One of the best experts on this subject based on the ideXlab platform.
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Synemin-related skeletal and cardiac myopathies: an overview of pathogenic variants.
American journal of physiology. Cell physiology, 2020Co-Authors: Denise Paulin, Onnik Agbulut, Yeranuhi Hovhannisyan, Serdar Kasakyan, Zhigang XueAbstract:This review analyzes data concerning patients with cardiomyopathies or skeletal myopathies associated with a variation in the intermediate filament (IF) Synemin gene (SYNM), also referred to as desmuslin (DMN). Molecular studies demonstrate that Synemin copolymerizes with desmin and vimentin IF and interacts with vinculin, α-actinin, α-dystrobrevin, dystrophin, talin, and zyxin. It has been found that Synemin is an A-kinase-anchoring protein (AKAP) that anchors protein kinase A (PKA) and modulates the PKA-dependent phosphorylation of several cytoskeletal substrates such as desmin. Because several IF proteins, including desmin, have been implicated in human genetic disorders such as dominant or recessive congenital and adult-onset myopathy, Synemin becomes a significant candidate for cardiac and skeletal myopathies of unknown etiology. Because SYNM is a new candidate gene that displays numerous sequence polymorphisms, in this review, we summarize the genetic and clinical literature about SYNM mutations. Protein-changing variants (missense, frameshifts, nonsense) were further evaluated based on structural modifications and amino acid interactions. We present in silico modeling of helical salt-bridges between residues to evaluate the impact of the Synemin networks crucial to interactions with cytoskeletal proteins. Finally, a discussion is featured regarding certain variants that may contribute to the disease state.
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Synemin acts as a regulator of signalling molecules during skeletal muscle hypertrophy
Journal of Cell Science, 2014Co-Authors: A Parlakian, Denise Paulin, Dario Coletti, Sonia Alonso-martin, Christophe Hourde, Pierre Joanne, Jacqueline Gao-li, Jocelyne Blanc, Arnaud Ferry, Zhigang XueAbstract:Synemin, a type IV intermediate filament (IF) protein, forms a bridge between IFs and cellular membranes. As an A-kinase-anchoring protein, it also provides temporal and spatial targeting of protein kinase A (PKA). However, little is known about its functional roles in either process. To better understand its functions in muscle tissue, we generated Synemin-deficient (Synm(-/-)) mice. Synm(-/-) mice displayed normal development and fertility but showed a mild degeneration and regeneration phenotype in myofibres and defects in sarcolemma membranes. Following mechanical overload, Synm(-/-) mice muscles showed a higher hypertrophic capacity with increased maximal force and fatigue resistance compared with control mice. At the molecular level, increased remodelling capacity was accompanied by decreased myostatin (also known as GDF8) and atrogin (also known as FBXO32) expression, and increased follistatin expression. Furthermore, the activity of muscle-mass control molecules (the PKA RII alpha subunit, p70S6K and CREB1) was increased in mutant mice. Finally, analysis of muscle satellite cell behaviour suggested that the absence of Synemin could affect the balance between self-renewal and differentiation of these cells. Taken together, our results show that Synemin is necessary to maintain membrane integrity and regulates signalling molecules during muscle hypertrophy.
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Dynamic expression of Synemin isoforms in mouse embryonic stem cells and neural derivatives
BMC Cell Biology, 2011Co-Authors: Sheila C De Souza Martins, Denise Paulin, Onnik Agbulut, Nicolas Diguet, Jean-christophe Larcher, Bruna S Paulsen, Stevens K Rehen, Vivaldo Moura-neto, Zhigang XueAbstract:Background Intermediate filaments (IFs) are major components of the mammalian cytoskeleton and expressed in cell-type-specific patterns. Morphological changes during cell differentiation are linked to IF network remodeling. However, little is known concerning the presence and the role of IFs in embryonic stem (ES) cells and during their differentiation. Results We have examined the expression profile of Synemin isoforms in mouse pluripotent ES cells and during their neural differentiation induced by retinoic acid. Using RT-PCR, Western blotting and immunostaining, we show that Synemin M is present at both mRNA and protein levels in undifferentiated ES cells as early as pluripotency factor Oct-3/4 and IF keratin 8. Synemin H was produced only in neural precursors when neural differentiation started, concurrently with Synemin M, nestin and glial fibrillary acidic protein. However, both Synemin H and M were restricted to the progenitor line during the neural differentiation program. Our in vivo analysis also confirmed the expression of Synemins H/M in multipotent neural stem cells in the subventricular zone of the adult brain, a neurogenic germinal niche of the mice. Knocking down Synemin in ES cells by shRNA lentiviral particles transduction has no influence on expression of Oct4, Nanog and SOX2, but decreased keratin 8 expression. Conclusions Our study shows a developmental stage specific regulation of Synemin isoforms in ES cells and its neural derivatives. These findings represent the first evidence that Synemins could potentially be useful markers for distinguishing multipotent ES cells from undifferentiated neural stem cells and more committed progenitor cells.
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Dynamic expression of Synemin isoforms in mouse embryonic stem cells and neural derivatives.
BMC cell biology, 2011Co-Authors: Sheila C De Souza Martins, Denise Paulin, Onnik Agbulut, Nicolas Diguet, Jean-christophe Larcher, Bruna S Paulsen, Stevens K Rehen, Vivaldo Moura-neto, Zhigang XueAbstract:Intermediate filaments (IFs) are major components of the mammalian cytoskeleton and expressed in cell-type-specific patterns. Morphological changes during cell differentiation are linked to IF network remodeling. However, little is known concerning the presence and the role of IFs in embryonic stem (ES) cells and during their differentiation. We have examined the expression profile of Synemin isoforms in mouse pluripotent ES cells and during their neural differentiation induced by retinoic acid. Using RT-PCR, Western blotting and immunostaining, we show that Synemin M is present at both mRNA and protein levels in undifferentiated ES cells as early as pluripotency factor Oct-3/4 and IF keratin 8. Synemin H was produced only in neural precursors when neural differentiation started, concurrently with Synemin M, nestin and glial fibrillary acidic protein. However, both Synemin H and M were restricted to the progenitor line during the neural differentiation program. Our in vivo analysis also confirmed the expression of Synemins H/M in multipotent neural stem cells in the subventricular zone of the adult brain, a neurogenic germinal niche of the mice. Knocking down Synemin in ES cells by shRNA lentiviral particles transduction has no influence on expression of Oct4, Nanog and SOX2, but decreased keratin 8 expression. Our study shows a developmental stage specific regulation of Synemin isoforms in ES cells and its neural derivatives. These findings represent the first evidence that Synemins could potentially be useful markers for distinguishing multipotent ES cells from undifferentiated neural stem cells and more committed progenitor cells.
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Desmin mutations in the terminal consensus motif prevent Synemin-desmin heteropolymer filament assembly.
Experimental cell research, 2011Co-Authors: Oussama Chourbagi, Denise Paulin, Patrick Vicart, Francine Bruston, Marianna Carinci, Zhigang Xue, Onnik AgbulutAbstract:Disorganization of the desmin network is associated with cardiac and skeletal myopathies characterized by accumulation of desmin-containing aggregates in the cells. Multiple associations of intermediate filament proteins form a network to increase mechanical and functional stability. Synemin is a desmin-associated type VI intermediate filament protein. Neither its impact on desmin network nor how it integrates into desmin filament is yet elucidated. To gain more insight into the molecular basis of these processes, we coexpressed Synemin with different desmin mutants in ex vivo models. The screening of fourteen desmin mutants showed that Synemin with desmin mutants revealed two behaviors. Firstly, Synemin was co-localized in desmin aggregates and its coexpression decreased the number of cells containing aggregates. Secondly, Synemin was excluded from the aggregates, then Synemin had no effect on desmin network organization. Among fourteen desmin mutants, there were only three mutants, p.E401K, p.R406W and p.E413K, in which Synemin was not found in aggregates. This behavior was correlated to the abnormal salt-bridges of desmin-dimer as seen in silico constructs. Moreover, desmin constructs in silico and published results in literature have predicted that the salt-bridges absence in the desmin filament building prevent longitudinal annealing and/or radial compaction. These results suggest that the state of desmin-filament assembly is crucial for Synemin anchorage and consequently might involve mechanical and functional stability of the cytoskeletal network.
Richard M. Robson - One of the best experts on this subject based on the ideXlab platform.
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Synemin interacts with the LIM domain protein zyxin and is essential for cell adhesion and migration.
Experimental cell research, 2009Co-Authors: Ning Sun, Denise Paulin, Ted W. Huiatt, Richard M. RobsonAbstract:Synemin is a unique cytoplasmic intermediate filament protein for which there is limited understanding of its exact cellular functions. The single human Synemin gene encodes at least two splice variants named alpha-Synemin and beta-Synemin, with the larger alpha-Synemin containing an additional 312 amino acid insert within the C-terminal tail domain. We report herein that, by using the entire tail domain of the smaller beta-Synemin as the bait in a yeast two-hybrid screen of a human skeletal muscle cDNA library, the LIM domain protein zyxin was identified as an interaction partner for human Synemin. The Synemin binding site in human zyxin was subsequently mapped to the C-terminal three tandem LIM-domain repeats, whereas the binding site for zyxin within beta-Synemin is within the C-terminal 332 amino acid region (SNbetaTII) at the end of the long tail domain. Transient expression of SNbetaTII within mammalian cells markedly reduced zyxin protein level, blocked localization of zyxin at focal adhesion sites and resulted in decreased cell adhesion and increased motility. Knockdown of Synemin expression with siRNAs within mammalian cells resulted in significantly compromised cell adhesion and cell motility. Our results suggest that Synemin participates in focal adhesion dynamics and is essential for cell adhesion and migration.
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Identification of a repeated domain within mammalian α-Synemin that interacts directly with talin
Experimental cell research, 2008Co-Authors: Ning Sun, Denise Paulin, David R. Critchley, Richard M. RobsonAbstract:Abstract The type VI intermediate filament (IF) protein Synemin is a unique member of the IF protein superfamily. Synemin associates with the major type III IF protein desmin forming heteropolymeric intermediate filaments (IFs) within developed mammalian striated muscle cells. These IFs encircle and link all adjacent myofibrils together at their Z-lines, as well as link the Z-lines of the peripheral layer of cellular myofibrils to the costameres located periodically along and subjacent to the sarcolemma. Costameres are multi-protein assemblies enriched in the cytoskeletal proteins vinculin, α-actinin, and talin. We report herein a direct interaction of human α-Synemin with the cytoskeletal protein talin by protein–protein interaction assays. The 312 amino acid insert (SNTIII) present only within α-Synemin binds to the rod domain of talin in vitro and co-localizes with talin at focal adhesion sites within mammalian muscle cells. Confocal microscopy studies showed that Synemin co-localizes with talin within the costameres of human skeletal muscle cells. Analysis of the primary sequences of human α- and β-Synemins revealed that SNTIII is composed of seven tandem repeats, each containing a specific Ser/Thr-X-Arg-His/Gln (S/T-X-R-H/Q) motif. Our results suggest human α-Synemin plays an essential role in linking the heteropolymeric IFs to adherens-type junctions, such as the costameres within mammalian striated muscle cells, via its interaction with talin, thereby helping provide mechanical integration for the muscle cell cytoskeleton.
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Human α-Synemin interacts directly with vinculin and metavinculin
The Biochemical journal, 2008Co-Authors: Ning Sun, Denise Paulin, David R. Critchley, Richard M. RobsonAbstract:Synemin is a very large, unique member of the IF (intermediate filament) protein superfamily. Association of Synemin with the major IF proteins, desmin and/or vimentin, within muscle cells forms heteropolymeric IFs. We have previously identified interactions of avian Synemin with alpha-actinin and vinculin. Avian Synemin, however, is expressed as only one form, whereas human Synemin is expressed as two major splice variants, namely alpha- and beta-Synemins. The larger alpha-Synemin contains an additional 312-amino-acid insert (termed SNTIII) located near the end of the long C-terminal tail domain. Whether alpha- and beta-Synemins have different cellular functions is unclear. In the present study we show, by in vitro protein-protein interaction assays, that SNTIII interacts directly with both vinculin and metavinculin. Furthermore, SNTIII interacts with vinculin in vivo, and this association is promoted by PtdIns(4,5)P(2). SNTIII also specifically co-localizes with vinculin within focal adhesions when transiently expressed in mammalian cells. In contrast, other regions of Synemin show distinct localization patterns in comparison with those of SNTIII, without labelling focal adhesions. Our results indicate that alpha-Synemin, but not beta-Synemin, interacts with both vinculin and metavinculin, thereby linking the heteropolymeric IFs to adhesion-type junctions, such as the costameres located within human striated muscle cells.
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Interactions of intermediate filament protein Synemin with dystrophin and utrophin.
Biochemical and biophysical research communications, 2006Co-Authors: R. Bhosle, Daniel E. Michele, Kevin P. Campbell, Richard M. RobsonAbstract:Synemin is a unique, very large intermediate filament (IF) protein present in all types of muscle cells, which forms heteropolymeric intermediate filaments (IFs) with the major IF proteins desmin and/or vimentin. We show herein that tissue-purified avian Synemin directly interacts with both dystrophin and utrophin, and that specific expressed regions of both of the mammalian (human) Synemin isoforms (α-Synemin and β-Synemin) directly interact with specific expressed domains/regions of the dystrophin and utrophin molecules. Mammalian Synemin is also shown to colocalize with dystrophin within muscle cell cultures. These results indicate that Synemin is an important IF protein in muscle cells that helps fortify the linkage between the peripheral layer of cellular myofibrils and the costameric regions located along the sarcolemma and the sarcolemma region located within the neuromuscular and myotendinous junctions (NMJs and MTJs).
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Hepatic stellate cells express Synemin, a protein bridging intermediate filaments to focal adhesions
Gut, 2006Co-Authors: Naoki Uyama, Richard M. Robson, Z Xue, Liena Zhao, E. Van Rossen, Yoshiaki Hirako, Hendrik Reynaert, David H. Adams, Milos PeknyAbstract:Background and aims: In the liver, stellate cells play several important (patho)physiological roles. They express a broad but variable spectrum of intermediate filament (IF) proteins. The aim of this study was to investigate the expression and functions of the intermediate filament protein Synemin in hepatic stellate cells (HSCs). Methods: In isolated and cultured rat HSCs, Synemin expression was examined by quantitative reverse transcriptase polymerase chain reaction, western blotting, and immunocytochemistry. Protein–protein interaction between Synemin and possible binding partners was investigated by co-immunoprecipitation and confocal microscopy. Results: Expression of Synemin was significantly downregulated with increased culture time. In 1-day cultured HSCs, Synemin associated with other IF proteins (GFAP, desmin, and vimentin), and with the focal adhesion proteins vinculin and talin, but not with α-actinin or paxillin. Synemin IF and focal adhesion proteins co-localised in long slender processes, but not in the lamellipodia. In human and rat liver tissue, the presence of Synemin was investigated by immunohistochemistry. In normal rat and human livers, Synemin immunoreactivity was found in HSCs, smooth muscle cells of hepatic arterioles, and nerve bundles in portal tracts, but not in portal fibroblasts. In CCl 4 -intoxicated rat livers and in human cirrhotic livers, immunoreactivity for Synemin in the parenchymal tissue was decreased. Thus Synemin was expressed in quiescent HSCs but not in portal fibroblasts; and Synemin expression decreased with HSC activation in vivo during chronic liver damage and with HSC activation in culture. Conclusions: Synemin forms heteropolymeric filaments with type-III IF proteins and acts as a bridging protein between IFs and a specific type of focal adhesions.
Hiroshi Yorifuji - One of the best experts on this subject based on the ideXlab platform.
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plectin 1 links intermediate filaments to costameric sarcolemma through β Synemin α dystrobrevin and actin
Journal of Cell Science, 2008Co-Authors: Takao Hijikata, Ryoki Ishikawa, Michihiro Imamura, Keitaro Isokawa, Kazuhiro Kohama, Akio Nakamura, Katsutoshi Yuasa, Shinichi Takeda, Hiroshi YorifujiAbstract:In skeletal muscles, the sarcolemma is possibly stabilized and protected against contraction-imposed stress by intermediate filaments (IFs) tethered to costameric sarcolemma. Although there is emerging evidence that plectin links IFs to costameres through dystrophin-glycoprotein complexes (DGC), the molecular organization from plectin to costameres still remains unclear. Here, we show that plectin 1, a plectin isoform expressed in skeletal muscle, can interact with β-Synemin, actin and a DGC component, α-dystrobrevin, in vitro. Ultrastructurally, β-Synemin molecules appear to be incorporated into costameric dense plaques, where they seem to serve as actin-associated proteins rather than IF proteins. In fact, they can bind actin and α-dystrobrevin in vitro. Moreover, in vivo immunoprecipitation analyses demonstrated that β-Synemin- and plectin-immune complexes from lysates of muscle light microsomes contained α-dystrobrevin, dystrophin, nonmuscle actin, metavinculin, plectin and β-Synemin. These findings suggest a model in which plectin 1 interacts with DGC and integrin complexes directly, or indirectly through nonmuscle actin and β-Synemin within costameres. The DGC and integrin complexes would cooperate to stabilize and fortify the sarcolemma by linking the basement membrane to IFs through plectin 1, β-Synemin and actin. Besides, the two complexes, together with plectin and IFs, might have their own functions as platforms for distinct signal transduction.
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Plectin 1 links intermediate filaments to costameric sarcolemma through beta-Synemin, alpha-dystrobrevin and actin.
Journal of cell science, 2008Co-Authors: Takao Hijikata, Ryoki Ishikawa, Michihiro Imamura, Keitaro Isokawa, Kazuhiro Kohama, Akio Nakamura, Katsutoshi Yuasa, Shinichi Takeda, Hiroshi YorifujiAbstract:In skeletal muscles, the sarcolemma is possibly stabilized and protected against contraction-imposed stress by intermediate filaments (IFs) tethered to costameric sarcolemma. Although there is emerging evidence that plectin links IFs to costameres through dystrophin-glycoprotein complexes (DGC), the molecular organization from plectin to costameres still remains unclear. Here, we show that plectin 1, a plectin isoform expressed in skeletal muscle, can interact with beta-Synemin, actin and a DGC component, alpha-dystrobrevin, in vitro. Ultrastructurally, beta-Synemin molecules appear to be incorporated into costameric dense plaques, where they seem to serve as actin-associated proteins rather than IF proteins. In fact, they can bind actin and alpha-dystrobrevin in vitro. Moreover, in vivo immunoprecipitation analyses demonstrated that beta-Synemin- and plectin-immune complexes from lysates of muscle light microsomes contained alpha-dystrobrevin, dystrophin, nonmuscle actin, metavinculin, plectin and beta-Synemin. These findings suggest a model in which plectin 1 interacts with DGC and integrin complexes directly, or indirectly through nonmuscle actin and beta-Synemin within costameres. The DGC and integrin complexes would cooperate to stabilize and fortify the sarcolemma by linking the basement membrane to IFs through plectin 1, beta-Synemin and actin. Besides, the two complexes, together with plectin and IFs, might have their own functions as platforms for distinct signal transduction.
