-
Journal of Muscle Research and Cell... Apr 2015In an article in this edition of the Journal of Muscle Research and Cell Motility, Geeves, Hitchcock-DiGregori and Gunning present a nomenclature founded on the gene and...
In an article in this edition of the Journal of Muscle Research and Cell Motility, Geeves, Hitchcock-DiGregori and Gunning present a nomenclature founded on the gene and exon structure of tropomyosin that is both clear and unambiguous. Moreover, the authors have ensured that the new names are linked with their sequences in the NCBI database, thus eliminating the uncertainty of linking a protein isoform with its sequence. This nomenclature system has been planned with the support of all the major labs that work with tropomyosin. We recommend that all researchers take note of this scheme and use it.
Topics: Animals; Humans; Tropomyosin
PubMed: 25361644
DOI: 10.1007/s10974-014-9393-x -
The Journal of Biological Chemistry Apr 2014Tropomodulins (Tmods) are F-actin pointed end capping proteins that interact with tropomyosins (TMs) and cap TM-coated filaments with higher affinity than TM-free...
Tropomodulins (Tmods) are F-actin pointed end capping proteins that interact with tropomyosins (TMs) and cap TM-coated filaments with higher affinity than TM-free filaments. Here, we tested whether differences in recognition of TM or actin isoforms by Tmod1 and Tmod3 contribute to the distinct cellular functions of these Tmods. We found that Tmod3 bound ~5-fold more weakly than Tmod1 to α/βTM, TM5b, and TM5NM1. However, surprisingly, Tmod3 was as effective as Tmod1 at capping pointed ends of skeletal muscle α-actin (αsk-actin) filaments coated with α/βTM, TM5b, or TM5NM1. Tmod3 only capped TM-coated αsk-actin filaments more weakly than Tmod1 in the presence of recombinant αTM2, which is unacetylated at its NH2 terminus, binds F-actin weakly, and has a disabled Tmod-binding site. Moreover, both Tmod1 and Tmod3 were similarly effective at capping pointed ends of platelet β/cytoplasmic γ (γcyto)-actin filaments coated with TM5NM1. In the absence of TMs, both Tmod1 and Tmod3 had similarly weak abilities to nucleate β/γcyto-actin filament assembly, but only Tmod3 could sequester cytoplasmic β- and γcyto-actin (but not αsk-actin) monomers and prevent polymerization under physiological conditions. Thus, differences in TM binding by Tmod1 and Tmod3 do not appear to regulate the abilities of these Tmods to cap TM-αsk-actin or TM-β/γcyto-actin pointed ends and, thus, are unlikely to determine selective co-assembly of Tmod, TM, and actin isoforms in different cell types and cytoskeletal structures. The ability of Tmod3 to sequester β- and γcyto-actin (but not αsk-actin) monomers in the absence of TMs suggests a novel function for Tmod3 in regulating actin remodeling or turnover in cells.
Topics: Actins; Animals; Cytoskeleton; Muscle, Skeletal; Protein Binding; Protein Isoforms; Rabbits; Sarcomeres; Spectrometry, Fluorescence; Tropomodulin; Tropomyosin
PubMed: 24644292
DOI: 10.1074/jbc.M114.555128 -
Journal of Muscle Research and Cell... Aug 2013Our thesis is that thin filament function can only be fully understood and muscle regulation then elucidated if atomic structures of the thin filament are available to... (Review)
Review
Our thesis is that thin filament function can only be fully understood and muscle regulation then elucidated if atomic structures of the thin filament are available to reveal the positions of tropomyosin on actin in all physiological states. After all, it is tropomyosin influenced by troponin that regulates myosin-crossbridge cycling on actin and therefore controls contraction in all muscles. In addition, we maintain that a complete appreciation of thin filament activation also requires that the mechanical properties of tropomyosin itself are recognized and then related to the effect of myosin-association on actin. Taking the Gestalt-binding of tropomyosin into account, coupled with our electron microscopy structures and computational chemistry, we propose a comprehensive mechanism for tropomyosin regulatory movement over the actin filament surface that explains the cooperative muscle activation process. In fact, well-known point mutations of critical amino acids on the actin-tropomyosin binding interface disrupt Gestalt-binding and are associated with a number of inherited myopathies. Moreover, dysregulation of tropomyosin may also be a factor that interferes with the gatekeeping operation of non-muscle tropomyosin in the controlling interactions of a wide variety of cellular actin-binding proteins. The clinical relevance of Gestalt-binding is discussed in articles by the Marston and the Gunning groups in this special journal issue devoted to the impact of tropomyosin on biological systems.
Topics: Actin Cytoskeleton; Actins; Humans; Microfilament Proteins; Muscles; Tropomyosin; Troponin
PubMed: 23666668
DOI: 10.1007/s10974-013-9342-0 -
Physiological consequences of tropomyosin mutations associated with cardiac and skeletal myopathies.Journal of Molecular Medicine (Berlin,... 2000Mutations have been identified in alpha-tropomyosin (Tm), a key regulatory protein in striated muscle cells, that are associated with a human cardiac myopathy,... (Review)
Review
Mutations have been identified in alpha-tropomyosin (Tm), a key regulatory protein in striated muscle cells, that are associated with a human cardiac myopathy, hypertrophic cardiomyopathy (FHC) and a human skeletal myopathy, nemaline myopathy (NM). In this review, we highlight experiments aimed at identifying the underlying mechanisms by which mutations in alpha-Tm cause inherited diseases of cardiac and skeletal muscle. Gene transfer of normal and mutant alpha-Tm to isolated adult cardiac myocytes was used to study the primary effects of mutant alpha-Tm proteins on the structure and contractile function of fully differentiated striated muscle cells. Both FHC and NM mutant alpha-Tm proteins incorporated normally into the adult muscle sarcomere, similar to normal Tm but exerted differential "dominant-negative" effects on the contractile function of the muscle cell. FHC mutant alpha-Tm proteins produced hypersensitivity of Ca2+-activated force production with a hierarchy that was related to the clinical severity of each mutation. Conversely, the NM mutant alpha-Tm produced a hyposensitivity of Ca2+-activated force production that may underlie, at least in part, the muscle weakness observed in NM. Taken together, the results suggest that the differential changes in the ability of the mutant Tm proteins to regulate muscle contraction in response to changing Ca2+ concentrations underlie the differential clinical presentation of the cardiac and skeletal muscle myopathies associated with mutations in alpha-Tm.
Topics: Amino Acid Sequence; Animals; Cardiomyopathy, Hypertrophic; Humans; Mice; Molecular Sequence Data; Mutation; Myocardial Contraction; Myopathies, Nemaline; Tropomyosin
PubMed: 11199327
DOI: 10.1007/s001090000161 -
International Journal of Molecular... Nov 2020Tropomyosin (Tpm) is one of the major actin-binding proteins that play a crucial role in the regulation of muscle contraction. The flexibility of the Tpm molecule is...
Tropomyosin (Tpm) is one of the major actin-binding proteins that play a crucial role in the regulation of muscle contraction. The flexibility of the Tpm molecule is believed to be vital for its functioning, although its role and significance are under discussion. We choose two sites of the Tpm molecule that presumably have high flexibility and stabilized them with the A134L or E218L substitutions. Applying differential scanning calorimetry (DSC), molecular dynamics (MD), co-sedimentation, trypsin digestion, and in vitro motility assay, we characterized the properties of Tpm molecules with these substitutions. The A134L mutation prevented proteolysis of Tpm molecule by trypsin, and both substitutions increased the thermal stability of Tpm and its bending stiffness estimated from MD simulation. None of these mutations affected the primary binding of Tpm to F-actin; still, both of them increased the thermal stability of the actin-Tpm complex and maximal sliding velocity of regulated thin filaments in vitro at a saturating Ca concentration. However, the mutations differently affected the Ca sensitivity of the sliding velocity and pulling force produced by myosin heads. The data suggest that both regions of instability are essential for correct regulation and fine-tuning of Ca-dependent interaction of myosin heads with F-actin.
Topics: Actin Cytoskeleton; Actins; Amino Acid Substitution; Animals; Calcium; Calorimetry, Differential Scanning; Humans; Molecular Dynamics Simulation; Mutation, Missense; Myosins; Protein Conformation; Protein Stability; Temperature; Tropomyosin; Trypsin
PubMed: 33218166
DOI: 10.3390/ijms21228720 -
Cell Adhesion & Migration 2011Cell migration and invasion requires the precise temporal and spatial orchestration of a variety of biological processes. Filaments of polymerized actin are critical... (Review)
Review
Cell migration and invasion requires the precise temporal and spatial orchestration of a variety of biological processes. Filaments of polymerized actin are critical players in these diverse processes, including the regulation of cell anchorage points (both cell-cell and cell-extracellular matrix), the uptake and delivery of molecules via endocytic pathways and the generation of force for both membrane protrusion and retraction. How the actin filaments are specialized for each of these discrete functions is yet to be comprehensively elucidated. The cytoskeletal tropomyosins are a family of actin associating proteins that form head-to-tail polymers which lay in the major groove of polymerized actin filaments. In the present review we summarize the emerging isoform-specific functions of tropomyosins in cell migration and invasion and discuss their potential roles in the specialization of actin filaments for the diverse cellular processes that together regulate cell migration and invasion.
Topics: Actin Cytoskeleton; Actin Depolymerizing Factors; Actins; Animals; Cell Movement; Cytoskeleton; Dimerization; Gene Expression; Humans; Myosins; Protein Isoforms; Saccharomyces cerevisiae; Tropomyosin; Vertebrates
PubMed: 21173575
DOI: 10.4161/cam.5.2.14438 -
Parasites & Vectors Oct 2016Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide. It infests the hens during the night where...
BACKGROUND
Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide. It infests the hens during the night where it causes irritation leading to restlessness, pecking and in extreme cases anaemia and increased cannibalism. Due to an increase in the occurrence of acaricide-resistant D. gallinae populations, new control strategies are required and vaccination may offer a sustainable alternative to acaricides. In this study, recombinant forms of D. gallinae tropomyosin (Der g 10) and paramyosin (Der g 11) were produced, characterised and tested as vaccine candidate molecules.
METHODS
The D. gallinae paramyosin (Der g 11) coding sequence was characterised and recombinant versions of Der g 11 and D. gallinae tropomyosin (Der g 10) were produced. Hens were immunised with the recombinant proteins and the resulting antibodies were fed to D. gallinae and mite mortality evaluated. Sections of mites were probed with anti- Der g 11 and Der g 10 antibodies to identify the tissue distribution of these protein in D. gallinae.
RESULTS
The entire coding sequence of Der g 11 was 2,622 bp encoding 874 amino acid residues. Immunohistochemical staining of mite sections revealed that Der g 10 and Der g 11 were located throughout D. gallinae tissues. In phylogenetic analyses of these proteins both clustered with orthologues from tick species rather than with orthologues from astigmatid mites. Antibodies raised in hens against recombinant forms of these proteins significantly increased D. gallinae mortality, by 19 % for Der g 10 (P < 0.001) and by 23 % for Der g 11 (P = 0.009) when fed to the mites using an in vitro feeding device.
CONCLUSIONS
This study has shown that Der g 10 and Der g 11 were located ubiquitously throughout D. gallinae and that antibodies raised against recombinant versions of these proteins can be used to significantly increase D. gallinae mortality in an in vitro feeding assay. When comparing archived data for all recombinant and native proteins assessed as vaccines using this in vitro feeding assay, Der g 10 and Der g 11 ranked highly and performed better than some of the pools of native proteins.
Topics: Animals; Antibodies; Chickens; Female; Mite Infestations; Poultry Diseases; Recombinant Proteins; Tropomyosin; Vaccines
PubMed: 27733192
DOI: 10.1186/s13071-016-1831-8 -
Molecular Biology of the Cell Jul 2015Most eukaryotic cells express multiple isoforms of the actin-binding protein tropomyosin that help construct a variety of cytoskeletal networks. Only one nonmuscle...
Most eukaryotic cells express multiple isoforms of the actin-binding protein tropomyosin that help construct a variety of cytoskeletal networks. Only one nonmuscle tropomyosin (Tm1A) has previously been described in Drosophila, but developmental defects caused by insertion of P-elements near tropomyosin genes imply the existence of additional, nonmuscle isoforms. Using biochemical and molecular genetic approaches, we identified three tropomyosins expressed in Drosophila S2 cells: Tm1A, Tm1J, and Tm2A. The Tm1A isoform localizes to the cell cortex, lamellar actin networks, and the cleavage furrow of dividing cells--always together with myosin-II. Isoforms Tm1J and Tm2A colocalize around the Golgi apparatus with the formin-family protein Diaphanous, and loss of either isoform perturbs cell cycle progression. During mitosis, Tm1J localizes to the mitotic spindle, where it promotes chromosome segregation. Using chimeras, we identified the determinants of tropomyosin localization near the C-terminus. This work 1) identifies and characterizes previously unknown nonmuscle tropomyosins in Drosophila, 2) reveals a function for tropomyosin in the mitotic spindle, and 3) uncovers sequence elements that specify isoform-specific localizations and functions of tropomyosin.
Topics: Animals; Cell Culture Techniques; Drosophila; Drosophila Proteins; Golgi Apparatus; Microfilament Proteins; Myosin Type II; Protein Isoforms; Spindle Apparatus; Tropomyosin
PubMed: 25971803
DOI: 10.1091/mbc.E14-12-1619 -
The Journal of Biological Chemistry Aug 2002Tropomyosin has been shown to cause annealing of gelsolin-capped actin filaments. Here we show that tropomyosin is highly efficient in transforming even the smallest...
Tropomyosin has been shown to cause annealing of gelsolin-capped actin filaments. Here we show that tropomyosin is highly efficient in transforming even the smallest gelsolin-actin complexes into long actin filaments. At low concentrations of tropomyosin, the effect of tropomyosin depends on the length of the actin oligomer, and the cooperative nature of the process is a direct indication that tropomyosin induces a conformational change in the gelsolin-actin complexes, altering the structure at the actin (+) end such that capping by gelsolin is abolished. At increased concentrations of tropomyosin, heterodimers, trimers, and tetramers are converted to actin filaments. In addition, evidence is presented demonstrating that gelsolin, once removed from the (+) end of the actin, can reassociate with the newly formed tropomyosin-decorated actin filaments. Interestingly, the binding of gelsolin to the tropomyosin-actin filament complexes saturates at 2 gelsolin molecules per 14 actin and 2 tropomyosins, i.e. two gelsolins per tropomyosin-regulatory unit along the filament. These observations support the view that both tropomyosin and gelsolin are likely to have important functions in addition to those proposed earlier.
Topics: Actin Cytoskeleton; Actins; Animals; Cattle; Chromatography, Gel; Dimerization; Dose-Response Relationship, Drug; Gelsolin; Kinetics; Microscopy, Electron; Microscopy, Fluorescence; Models, Chemical; Protein Binding; Protein Conformation; Time Factors; Tropomyosin
PubMed: 12048198
DOI: 10.1074/jbc.M203360200 -
International Journal of Molecular... Jun 2020In striated muscle the extent of the overlap between actin and myosin filaments contributes to the development of force. In slow twitch muscle fibers actin filaments are...
In striated muscle the extent of the overlap between actin and myosin filaments contributes to the development of force. In slow twitch muscle fibers actin filaments are longer than in fast twitch fibers, but the mechanism which determines this difference is not well understood. We hypothesized that tropomyosin isoforms Tpm1.1 and Tpm3.12, the actin regulatory proteins, which are specific respectively for fast and slow muscle fibers, differently stabilize actin filaments and regulate severing of the filaments by cofilin-2. Using in vitro assays, we showed that Tpm3.12 bound to F-actin with almost 2-fold higher apparent binding constant (K) than Tpm1.1. Cofilin2 reduced K of both tropomyosin isoforms. In the presence of Tpm1.1 and Tpm3.12 the filaments were longer than unregulated F-actin by 25% and 40%, respectively. None of the tropomyosins affected the affinity of cofilin-2 for F-actin, but according to the linear lattice model both isoforms increased cofilin-2 binding to an isolated site and reduced binding cooperativity. The filaments decorated with Tpm1.1 and Tpm3.12 were severed by cofilin-2 more often than unregulated filaments, but depolymerization of the severed filaments was inhibited. The stabilization of the filaments by Tpm3.12 was more efficient, which can be attributed to lower dynamics of Tpm3.12 binding to actin.
Topics: Actin Cytoskeleton; Animals; Binding Sites; Cofilin 2; Muscle, Striated; Polymerization; Protein Binding; Protein Isoforms; Rabbits; Tropomyosin
PubMed: 32560136
DOI: 10.3390/ijms21124285