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Journal of Muscle Research and Cell... Mar 2020The interactions of cytoskeletal actin filaments with myosin family motors are essential for the integrity and function of eukaryotic cells. They support a wide range of... (Review)
Review
The interactions of cytoskeletal actin filaments with myosin family motors are essential for the integrity and function of eukaryotic cells. They support a wide range of force-dependent functions. These include mechano-transduction, directed transcellular transport processes, barrier functions, cytokinesis, and cell migration. Despite the indispensable role of tropomyosins in the generation and maintenance of discrete actomyosin-based structures, the contribution of individual cytoskeletal tropomyosin isoforms to the structural and functional diversification of the actin cytoskeleton remains a work in progress. Here, we review processes that contribute to the dynamic sorting and targeted distribution of tropomyosin isoforms in the formation of discrete actomyosin-based structures in animal cells and their effects on actin-based motility and contractility.
Topics: Actins; Humans; Tropomyosin
PubMed: 31054005
DOI: 10.1007/s10974-019-09514-0 -
Sub-cellular Biochemistry 2017Tropomyosin is the archetypal-coiled coil, yet studies of its structure and function have proven it to be a dynamic regulator of actin filament function in muscle and... (Review)
Review
Tropomyosin is the archetypal-coiled coil, yet studies of its structure and function have proven it to be a dynamic regulator of actin filament function in muscle and non-muscle cells. Here we review aspects of its structure that deviate from canonical leucine zipper coiled coils that allow tropomyosin to bind to actin, regulate myosin, and interact directly and indirectly with actin-binding proteins. Four genes encode tropomyosins in vertebrates, with additional diversity that results from alternate promoters and alternatively spliced exons. At the same time that periodic motifs for binding actin and regulating myosin are conserved, isoform-specific domains allow for specific interaction with myosins and actin filament regulatory proteins, including troponin. Tropomyosin can be viewed as a universal regulator of the actin cytoskeleton that specifies actin filaments for cellular and intracellular functions.
Topics: Amino Acid Sequence; Animals; Humans; Protein Conformation; Tropomyosin
PubMed: 28101865
DOI: 10.1007/978-3-319-49674-0_9 -
Allergy and Asthma Proceedings Sep 2021Panallergens are proteins that take part in key processes of organisms and, therefore, are ubiquitously distributed with highly conserved sequences and structures. One... (Review)
Review
Panallergens are proteins that take part in key processes of organisms and, therefore, are ubiquitously distributed with highly conserved sequences and structures. One class of these panallergens is composed of the tropomyosins. The highly heat-stable tropomyosins comprise the major allergens in crustaceans and mollusks, which make them important food allergens in exposed populations. Tropomyosins are responsible for a widespread immunoglobulin E cross-reactivity among allergens from different sources. Allergic tropomyosins are expressed in many species, including parasites and insects. This panallergen class is divided, according to it capacity of induced allergic symptoms, into allergenic or nonallergenic tropomyosin. Although vertebrate tropomyosins share ∼55% of sequence homology with invertebrate tropomyosins, it has been thought that the invertebrate tropomyosins would not have allergic properties. Nevertheless, in recent years, this opinion has been changed. In particular, tropomyosin has been recognized as a major allergen in many insects. A high grade of homology has been shown among tropomyosins from different species, such as crustaceans and insects, which supports the hypothesis of cross-reactivity among tropomyosins from divergent species. Moreover, the emerging habit of consuming edible insects has drawn the attention of allergists to invertebrate tropomyosin protein due to its potential allergenic risk. Nevertheless, evidence about tropomyosin involvement in clinical allergic response is still scarce and deserves more investigation. This review intended to report allergic reactions associated with different tropomyosins when considering house dust mites, parasites, seafood, and insects, and to summarize our current knowledge about its cross-reactivity because this could help physicians to accurately diagnose patients with food allergy.
Topics: Allergens; Amino Acid Sequence; Cross Reactions; Food Hypersensitivity; Humans; Immunoglobulin E; Tropomyosin
PubMed: 34474717
DOI: 10.2500/aap.2021.42.210057 -
International Archives of Allergy and... Aug 1999Among food allergens, crustaceans, such as shrimp, crab, crawfish and lobster, are a frequent cause of adverse food reactions in allergic individuals. The major allergen... (Review)
Review
Among food allergens, crustaceans, such as shrimp, crab, crawfish and lobster, are a frequent cause of adverse food reactions in allergic individuals. The major allergen has been identified as the muscle protein tropomyosin. This molecule belongs to a family of highly conserved proteins with multiple isoforms found in both muscle and nonmuscle cells of all species of vertebrates and invertebrates. Its native structure consists of two parallel alpha-helical tropomyosin molecules that are wound around each other forming a coiled-coil dimer. Allergenic tropomyosins are found in invertebrates such as crustaceans (shrimp, lobster, crab, crawfish), arachnids (house dust mites), insects (cockroaches), and mollusks (e.g. squid), whereas vertebrate tropomyosins are nonallergenic. Studies of cross-reactivities among crustaceans and the high degree of sequence identity among them suggest that tropomyosin is probably the common major allergen in crustaceans. Furthermore, immunological relationships between crustaceans, cockroaches and housedust mites have been established and may suggest tropomyosin as an important cross-sensitizing pan allergen.
Topics: Allergens; Amino Acid Sequence; Animals; Cross Reactions; Food Hypersensitivity; Humans; Invertebrates; Models, Molecular; Molecular Sequence Data; Tropomyosin
PubMed: 10474029
DOI: 10.1159/000024201 -
International Review of Cytology 1997Vertebrate nonmuscle cells, such as human and rat fibroblasts, express multiple isoforms of tropomyosin, which are generated from four different genes and a combination... (Review)
Review
Vertebrate nonmuscle cells, such as human and rat fibroblasts, express multiple isoforms of tropomyosin, which are generated from four different genes and a combination of alternative promoter activities and alternative splicing. The amino acid variability among these isoforms is primarily restricted to three alternatively spliced exon regions; an amino-terminal region, an internal exon, and a carboxyl-terminal exon. Recent evidence reveals that these variable exon regions encode amino acid sequences that may dictate isoform-specific functions. The differential expression of tropomyosin isoforms found in cell transformation and cell differentiation, as well as the differential localization of tropomyosin isoforms in some types of culture cells and developing neurons suggest a differential isoform function in vivo. Tropomyosin in striated muscle works together with the troponin complex to regulate muscle contraction in a Ca(2+)-dependent fashion. Both in vitro and in vivo evidence suggest that multiple isoforms of tropomyosin in nonmuscle cells may be required for regulating actin filament stability, intracellular granule movement, cell shape determination, and cytokinesis. Tropomyosin-binding proteins such as caldesmon, tropomodulin, and other unidentified proteins may be required for some of these functions. Strong evidence for the distinct functions carried out by different tropomyosin isoforms has been generated from genetic analysis of yeast and Drosophila tropomyosin mutants.
Topics: Animals; Fibroblasts; Humans; Isoenzymes; Tropomyosin
PubMed: 9002235
DOI: 10.1016/s0074-7696(08)61619-8 -
Physiological Reviews Jan 2008Tropomyosins are rodlike coiled coil dimers that form continuous polymers along the major groove of most actin filaments. In striated muscle, tropomyosin regulates the... (Review)
Review
Tropomyosins are rodlike coiled coil dimers that form continuous polymers along the major groove of most actin filaments. In striated muscle, tropomyosin regulates the actin-myosin interaction and, hence, contraction of muscle. Tropomyosin also contributes to most, if not all, functions of the actin cytoskeleton, and its role is essential for the viability of a wide range of organisms. The ability of tropomyosin to contribute to the many functions of the actin cytoskeleton is related to the temporal and spatial regulation of expression of tropomyosin isoforms. Qualitative and quantitative changes in tropomyosin isoform expression accompany morphogenesis in a range of cell types. The isoforms are segregated to different intracellular pools of actin filaments and confer different properties to these filaments. Mutations in tropomyosins are directly involved in cardiac and skeletal muscle diseases. Alterations in tropomyosin expression directly contribute to the growth and spread of cancer. The functional specificity of tropomyosins is related to the collaborative interactions of the isoforms with different actin binding proteins such as cofilin, gelsolin, Arp 2/3, myosin, caldesmon, and tropomodulin. It is proposed that local changes in signaling activity may be sufficient to drive the assembly of isoform-specific complexes at different intracellular sites.
Topics: Actin Cytoskeleton; Actins; Animals; Cytoskeleton; Gene Expression Regulation; Humans; Protein Isoforms; Signal Transduction; Tropomyosin
PubMed: 18195081
DOI: 10.1152/physrev.00001.2007 -
Advances in Experimental Medicine and... 2008Tropomyosins were discovered as regulators of actomyosin contractility in muscle cells, making yeasts and other fungi seem unlikely to harbor such proteins. Fungal cells... (Review)
Review
Tropomyosins were discovered as regulators of actomyosin contractility in muscle cells, making yeasts and other fungi seem unlikely to harbor such proteins. Fungal cells are encased in a rigid cell wall and do not engage in the same sorts of contractile shape changes of animal cells. However, discovery of actin and myosin in yeast raised the possibility for a role for tropomyosin in regulating their interaction. Through a biochemical search, fungal tropomyosins were identified with strong similarities to their animal counterparts in terms ofprotein structure and physical properties. Two particular fungi, the buddingyeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe, have provided powerful genetic systems for studying tropomyosins in nonmetazoans. In these yeasts, tropomyosins associate with subsets ofactin filamentous structures. Mutational studies oftropomyosin genes and biochemical assays of purified proteins point to roles for these proteins as factors that stabilize actin filaments, promote actin-based structures of particular architecture and help maintain distinct biochemical identities among different filament populations. Tropomyosin-enriched filaments are the cytoskeletal structures that promote the major cell shape changes of these organisms: polarized growth and cell division.
Topics: Actins; Amino Acid Sequence; Biochemistry; Cell Division; Fungal Proteins; Gene Expression Regulation, Fungal; Models, Biological; Molecular Conformation; Molecular Sequence Data; Phylogeny; Saccharomyces cerevisiae; Schizosaccharomyces; Sequence Homology, Amino Acid; Species Specificity; Tropomyosin
PubMed: 19209822
DOI: 10.1007/978-0-387-85766-4_14 -
Comprehensive Reviews in Food Science... Jan 2022Tropomyosin (TM) is a major allergen in crustaceans, which often causes allergy and is fatal to some consumers. Currently, the most effective treatment is to avoid... (Review)
Review
Tropomyosin (TM) is a major allergen in crustaceans, which often causes allergy and is fatal to some consumers. Currently, the most effective treatment is to avoid ingesting TM, although most adverse events occur in accidental ingestion. In this review, the molecular characterization, epitopes, cross-reactivity, and pathogenesis of TM are introduced and elucidated. Modification of TM by traditional processing methods such as heat treatment and enzymatic hydrolysis, and innovative processing technologies including high-pressure treatment, cold plasma (CP), ultrasound, pulsed electric field (PEF), pulsed ultraviolet, microwave and irradiation are discussed in detail. Particularly, enzymolysis, PEF, and CP technologies show great potential for modifying TM and more studies are needed to verify their effectiveness for the seafood industry. Possible mechanisms and the advantages/disadvantages of these technologies for the mitigation of TM allergenicity are also highlighted. Further work should be conducted to investigate the allergenicity caused by protein segments such as epitopes, examine the interaction sites between the allergen and the processing techniques and reveal the reduction mechanism of allergenicity.
Topics: Allergens; Cross Reactions; Epitopes; Seafood; Tropomyosin
PubMed: 34954871
DOI: 10.1111/1541-4337.12889 -
Advances in Experimental Medicine and... 2008Tropomyosin is known as the archetypal coiled coil, being the first to be sequenced and modeled. Studies of the structure and dynamics of tropomyosin, accompanied by... (Review)
Review
Tropomyosin is known as the archetypal coiled coil, being the first to be sequenced and modeled. Studies of the structure and dynamics of tropomyosin, accompanied by biochemical and biophysical analyses of tropomyosin, mutants and model peptides, have revealed the complexity and subtleties required for tropomyosin function. Interruptions in the canonical coiled coil allow for bends and regions of local instability that are required for tropomyosin to bind to the helical actin filament. This chapter highlights insights gained from recent structural studies as they relate to variations in tropomyosin's coiled-coil structure that are essential for binding to actin and the relationship of periodic repeats to actin molecules in the filament.
Topics: Actin Cytoskeleton; Actins; Animals; Binding Sites; Biochemistry; Biophysics; Gene Expression Regulation; Humans; Magnetic Resonance Spectroscopy; Models, Biological; Mutation; Peptides; Protein Conformation; Protein Structure, Secondary; Tropomyosin
PubMed: 19209813
DOI: 10.1007/978-0-387-85766-4_5 -
Trends in Cell Biology Jun 2005Actin filament functional diversity is paralleled by variation in the composition of isoforms of tropomyosin in these filaments. Although the role of tropomyosin is well... (Review)
Review
Actin filament functional diversity is paralleled by variation in the composition of isoforms of tropomyosin in these filaments. Although the role of tropomyosin is well understood in skeletal muscle, where it regulates the actin-myosin interaction, its role in the cytoskeleton has been obscure. The intracellular sorting of tropomyosin isoforms indicated a role in spatial specialization of actin filament function. Genetic manipulation and protein chemistry studies have confirmed that these isoforms are functionally distinct. Tropomyosins differ in their recruitment of myosin motors and their interaction with actin filament regulators such as ADF-cofilin. Tropomyosin isoforms have therefore provided a powerful mechanism to diversify actin filament function in different intracellular compartments.
Topics: Actins; Alternative Splicing; Animals; Cytoskeleton; Gene Expression Regulation, Developmental; Humans; Protein Isoforms; Tropomyosin
PubMed: 15953552
DOI: 10.1016/j.tcb.2005.04.007