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Ciba Foundation Symposium 1972
Review
Topics: Actins; Macromolecular Substances; Models, Biological; Models, Structural; Molecular Weight; Muscle Contraction; Muscle Proteins; Myofibrils; Myosins; Protein Conformation; Tropomyosin
PubMed: 4580343
DOI: 10.1002/9780470719909.ch13 -
Cell Biochemistry and Biophysics 2006Over the last half century, major theoretical and experimental advances have been made in understanding the molecular architecture (e.g., sarcomeric organization) and... (Review)
Review
Over the last half century, major theoretical and experimental advances have been made in understanding the molecular architecture (e.g., sarcomeric organization) and biophysics (e.g., excitation-contraction coupling) of striated muscle. Studies of how the contractile apparatus is assembled have a shorter history, but our understanding has deepened considerably over the last decade. This review focuses on spontaneous intracellular calcium (Ca2+) signals and their role in skeletal muscle myofibrillogenesis. In embryonic skeletal muscle, several classes of spontaneous Ca2+ signal occur both in vivo and in culture, and blocking their production prevents de novo sarcomere assembly. This review includes a brief overview of myofibrillogenesis, discussion of spontaneous Ca2+ signals produced in embryonic skeletal muscle, the Xenopus model system, the role of Ca2+ signals in regulating assembly of the three major filament systems (actin, titin, and myosin), integration of physiological and biochemical approaches to the problem, and the clinical relevance of basic research in this area. Interspersed throughout are suggestions for future directions and citations for reviews in closely related areas not covered herein.
Topics: Animals; Calcium; Calcium Signaling; Humans; Models, Biological; Molecular Motor Proteins; Muscle Contraction; Muscle, Skeletal; Myofibrils; Sarcomeres
PubMed: 16845177
DOI: 10.1385/CBB:45:3:317 -
Life Science Alliance Apr 2022Protein isoform transitions confer muscle fibers with distinct properties and are regulated by differential transcription and alternative splicing. RNA-binding Fox...
Protein isoform transitions confer muscle fibers with distinct properties and are regulated by differential transcription and alternative splicing. RNA-binding Fox protein 1 (Rbfox1) can affect both transcript levels and splicing, and is known to contribute to normal muscle development and physiology in vertebrates, although the detailed mechanisms remain obscure. In this study, we report that Rbfox1 contributes to the generation of adult muscle diversity in Rbfox1 is differentially expressed among muscle fiber types, and RNAi knockdown causes a hypercontraction phenotype that leads to behavioral and eclosion defects. Misregulation of fiber type-specific gene and splice isoform expression, notably loss of an indirect flight muscle-specific isoform of Troponin-I that is critical for regulating myosin activity, leads to structural defects. We further show that Rbfox1 directly binds the 3'-UTR of target transcripts, regulates the expression level of myogenic transcription factors myocyte enhancer factor 2 and Salm, and both modulates expression of and genetically interacts with the CELF family RNA-binding protein Bruno1 (Bru1). Rbfox1 and Bru1 co-regulate fiber type-specific alternative splicing of structural genes, indicating that regulatory interactions between FOX and CELF family RNA-binding proteins are conserved in fly muscle. Rbfox1 thus affects muscle development by regulating fiber type-specific splicing and expression dynamics of identity genes and structural proteins.
Topics: Animals; Drosophila; Drosophila Proteins; Female; Gene Knockdown Techniques; Male; Myofibrils; Protein Isoforms; RNA-Binding Proteins
PubMed: 34996845
DOI: 10.26508/lsa.202101342 -
Molecules (Basel, Switzerland) Feb 2020We compare steps observed during the fibrillogenesis of myofibrils with the sequence of steps predictable by a recent analysis of the structurization and functioning of...
We compare steps observed during the fibrillogenesis of myofibrils with the sequence of steps predictable by a recent analysis of the structurization and functioning of striated muscles. The predicted assembly steps are based solely on fundamental equilibrium processes, particularly supramolecular interactions and liquid crystalline alignment of the rigid thick and thin filaments hosted within the sarcomer. Satisfactory agreement is obtained between several of the observed and the predicted fibrillogenesis steps. In several cases, however, the actual steps appear to be more complex than expected, evidencing the occurrence of transport and kinetic pathways that may assist the attainment of the equilibrium structure. The memory of the order of a precursor mesophase is imprinted during the remodeling of the surfaces at which the two sets of filaments are anchored. The relevance of the present analysis to the functioning of the myofibril is considered.
Topics: Actin Cytoskeleton; Actins; Animals; Connectin; Humans; Liquid Crystals; Models, Biological; Myofibrils; Myosins
PubMed: 32075335
DOI: 10.3390/molecules25040862 -
Journal of Muscle Research and Cell... 2005Building a myofibril from its component proteins requires the interactions of many different proteins in a process whose details are not understood. Several models have...
Building a myofibril from its component proteins requires the interactions of many different proteins in a process whose details are not understood. Several models have been proposed to provide a framework for understanding the increasing data on new myofibrillar proteins and their localizations during muscle development. In this article we discuss four current models that seek to explain how the assembly occurs in vertebrate cross-striated muscles. The models hypothesize: (a) stress fiber-like structures as templates for the assembly of myofibrils, (b) assembly in which the actin filaments and Z-bands form subunits independently from A-band subunits, with the two subsequently joined together to form a myofibril, (c) premyofibrils as precursors of myofibrils, or (d) assembly occurring without any intermediary structures. The premyofibril model, proposed by the authors, is discussed in more detail as it could explain myofibrillogenesis under a variety of different conditions: in ovo, in explants, and in tissue culture studies on cardiac and skeletal muscles.
Topics: Actinin; Actins; Animals; Cell Fusion; Cells, Cultured; Connectin; Microscopy, Fluorescence; Microtubules; Models, Biological; Muscle Development; Muscle Fibers, Skeletal; Muscle Proteins; Muscle, Skeletal; Myoblasts; Myofibrils; Paclitaxel; Protein Kinases; Quail
PubMed: 16465476
DOI: 10.1007/s10974-005-9016-7 -
Scientific Reports Jun 2019Rapid sarcomere lengthening waves propagate along a single muscle myofibril during spontaneous oscillatory contraction (SPOC). In asynchronous insect flight muscles,...
Rapid sarcomere lengthening waves propagate along a single muscle myofibril during spontaneous oscillatory contraction (SPOC). In asynchronous insect flight muscles, SPOC is thought to be almost completely synchronized over the entire myofibril. This phenomenon does not require Ca regulation of the dynamics of the motor proteins, and cannot be explained simply by the longitudinal mechanical equilibrium among sarcomeres in the myofibril. In the present study, we rationalize these phenomena by considering the lateral mechanical equilibrium, in which two tensions originating from the inverse relationship between sarcomere length and lattice spacing, along with the lattice alignment, play important roles in the mechanical communication between motor proteins on adjacent filaments via the Z-disc. The proposed model is capable of explaining various SPOC phenomena based on the stochastic power-stroke mechanism of motor proteins, which responds to temporal changes in longitudinal mechanical load.
Topics: Algorithms; Biomechanical Phenomena; Elasticity; Mechanotransduction, Cellular; Models, Biological; Molecular Motor Proteins; Muscle Contraction; Muscle, Skeletal; Myofibrils; Myosins; Sarcomeres
PubMed: 31249348
DOI: 10.1038/s41598-019-45772-1 -
ELife Jan 2021Skeletal muscles are composed of gigantic cells called muscle fibers, packed with force-producing myofibrils. During development, the size of individual muscle fibers...
Skeletal muscles are composed of gigantic cells called muscle fibers, packed with force-producing myofibrils. During development, the size of individual muscle fibers must dramatically enlarge to match with skeletal growth. How muscle growth is coordinated with growth of the contractile apparatus is not understood. Here, we use the large flight muscles to mechanistically decipher how muscle fiber growth is controlled. We find that regulated activity of core members of the Hippo pathway is required to support flight muscle growth. Interestingly, we identify Dlg5 and Slmap as regulators of the STRIPAK phosphatase, which negatively regulates Hippo to enable post-mitotic muscle growth. Mechanistically, we show that the Hippo pathway controls timing and levels of sarcomeric gene expression during development and thus regulates the key components that physically mediate muscle growth. Since Dlg5, STRIPAK and the Hippo pathway are conserved a similar mechanism may contribute to muscle or cardiomyocyte growth in humans.
Topics: Animals; Drosophila melanogaster; Gene Expression Regulation; Hippo Signaling Pathway; Muscle Fibers, Skeletal; Myofibrils; Sarcomeres
PubMed: 33404503
DOI: 10.7554/eLife.63726 -
Food Chemistry Mar 2024The effect of frozen time and the temperature on myofibril degradation and the structure of myofibrillar proteins of porcine longissimus muscles were investigated. With...
The effect of frozen time and the temperature on myofibril degradation and the structure of myofibrillar proteins of porcine longissimus muscles were investigated. With extended frozen time and increased temperature, the muscle fibres became broken; the muscle cells became irregularly arranged; and the fragmentation index value, number of ionic bonds, and number of hydrogen bonds of the samples significantly decreased. Meanwhile, the myofibril fragmentation index value, number of hydrophobic interactions, and number of disulphide bonds significantly increased (P < 0.05). After 12 months of storage, the intensities of I/I, I/I, I/I, and I/I in the samples frozen at -8 °C were reduced by 4.36 %, 1.28 %, 1.86 %, and 0.74 %, respectively. A reduction in the maximum absorption peak and a red shift were observed in the ultraviolet spectrum. Therefore, frozen storage resulted in significant damage to the tissue microstructureand caused accelerated protein degradation, and the loss of protein structural integrity.
Topics: Animals; Swine; Myofibrils; Muscle, Skeletal; Meat; Freezing; Proteolysis
PubMed: 37813022
DOI: 10.1016/j.foodchem.2023.137671 -
Journal of Cell Science Jul 2023Myofibrils are long intracellular cables specific to muscles, composed mainly of actin and myosin filaments. The actin and myosin filaments are organized into repeated...
Myofibrils are long intracellular cables specific to muscles, composed mainly of actin and myosin filaments. The actin and myosin filaments are organized into repeated units called sarcomeres, which form the myofibrils. Muscle contraction is achieved by the simultaneous shortening of sarcomeres, which requires all sarcomeres to be the same size. Muscles have a variety of ways to ensure sarcomere homogeneity. We have previously shown that the controlled oligomerization of Zasp proteins sets the diameter of the myofibril. Here, we looked for Zasp-binding proteins at the Z-disc to identify additional proteins coordinating myofibril growth and assembly. We found that the E1 subunit of the oxoglutarate dehydrogenase complex localizes to both the Z-disc and the mitochondria, and is recruited to the Z-disc by Zasp52. The three subunits of the oxoglutarate dehydrogenase complex are required for myofibril formation. Using super-resolution microscopy, we revealed the overall organization of the complex at the Z-disc. Metabolomics identified an amino acid imbalance affecting protein synthesis as a possible cause of myofibril defects, which is supported by OGDH-dependent localization of ribosomes at the Z-disc.
Topics: Animals; Myofibrils; Sarcomeres; Drosophila; Actins; Myosins; Ketoglutarate Dehydrogenase Complex
PubMed: 37272588
DOI: 10.1242/jcs.260717 -
Handbook of Clinical Neurology 2011Myofibrillar myopathies (MFMs) represent a group of muscular dystrophies with a similar morphological phenotype. The diagnosis is established by muscle biopsy. The MFMs... (Review)
Review
Myofibrillar myopathies (MFMs) represent a group of muscular dystrophies with a similar morphological phenotype. The diagnosis is established by muscle biopsy. The MFMs are characterized by a distinct pathological pattern of myofibrillar dissolution associated with disintegration of the Z-disk, accumulation of myofibrillar degradation products, and ectopic expression of multiple proteins that include desmin, αB-crystallin, dystrophin, and sometimes congophilic material. The clinical features of MFMs are more variable. These include progressive muscle weakness that often involves or begins in distal muscles, but limb-girdle or scapuloperoneal distributions can also occur. Cardiomyopathy and peripheral neuropathy are frequent associated features. Electromyography of the affected muscles reveals myopathic motor unit potentials and abnormal irritability, often with myotonic discharges. Rarely, neurogenic motor unit potentials or slowing of nerve conduction velocities are present. To date, all MFM mutations have appeared in Z-disk-associated proteins: namely, desmin, αB-crystallin, myotilin, ZASP, filamin C, and Bag3. However, in the majority of patients with MFM, the disease gene awaits discovery.
Topics: Muscular Diseases; Myofibrils
PubMed: 21496631
DOI: 10.1016/B978-0-08-045031-5.00011-6