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Abstract
In the last decade, improvements in electron microscopy and image processing have permitted significantly higher resolutions to be achieved (sometimes <1 nm) when studying isolated actin and myosin filaments. In the case of actin filaments the changing structure when troponin binds calcium ions can be followed using electron microscopy and single particle analysis to reveal what happens on each of the seven non-equivalent pseudo-repeats of the tropomyosin α-helical coiled-coil. In the case of the known family of myosin filaments not only are the myosin head arrangements under relaxing conditions being defined, but the latest analysis, also using single particle methods, is starting to reveal the way that the α-helical coiled-coil myosin rods are packed to give the filament backbones.
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Affiliation(s)
- John M Squire
- Muscle Contraction Group, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, BS8 1TD, UK.
| | - Danielle M Paul
- Muscle Contraction Group, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Edward P Morris
- Division of Structural Biology, The Institute of Cancer Research, London, SW3 6JB, UK
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2
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Qadota H, Mayans O, Matsunaga Y, McMurry JL, Wilson KJ, Kwon GE, Stanford R, Deehan K, Tinley TL, Ngwa VM, Benian GM. The SH3 domain of UNC-89 (obscurin) interacts with paramyosin, a coiled-coil protein, in Caenorhabditis elegans muscle. Mol Biol Cell 2016; 27:1606-20. [PMID: 27009202 PMCID: PMC4865318 DOI: 10.1091/mbc.e15-09-0675] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 03/16/2016] [Accepted: 03/16/2016] [Indexed: 11/11/2022] Open
Abstract
UNC-89 is a giant polypeptide located at the sarcomeric M-line of Caenorhabditis elegans muscle. The human homologue is obscurin. To understand how UNC-89 is localized and functions, we have been identifying its binding partners. Screening a yeast two-hybrid library revealed that UNC-89 interacts with paramyosin. Paramyosin is an invertebrate-specific coiled-coil dimer protein that is homologous to the rod portion of myosin heavy chains and resides in thick filament cores. Minimally, this interaction requires UNC-89's SH3 domain and residues 294-376 of paramyosin and has a KD of ∼1.1 μM. In unc-89 loss-of-function mutants that lack the SH3 domain, paramyosin is found in accumulations. When the SH3 domain is overexpressed, paramyosin is mislocalized. SH3 domains usually interact with a proline-rich consensus sequence, but the region of paramyosin that interacts with UNC-89's SH3 is α-helical and lacks prolines. Homology modeling of UNC-89's SH3 suggests structural features that might be responsible for this interaction. The SH3-binding region of paramyosin contains a "skip residue," which is likely to locally unwind the coiled-coil and perhaps contributes to the binding specificity.
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Affiliation(s)
- Hiroshi Qadota
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Olga Mayans
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Yohei Matsunaga
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Jonathan L McMurry
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144
| | - Kristy J Wilson
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Grace E Kwon
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Rachel Stanford
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Kevin Deehan
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Tina L Tinley
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Verra M Ngwa
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144
| | - Guy M Benian
- Department of Pathology, Emory University, Atlanta, GA 30322
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3
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Abstract
Research on Caenorhabditis elegans has led to the discovery of the consequences of mutation in myosin, its associated proteins, and the extracellular matrix-membrane cytoskeleton complex. Key results include understanding thick filament structure and assembly, the regulation of sarcomeric protein turnover, and the organization of thick and thin filaments into ordered sarcomeres. These results are critical to studies of cardiovascular diseases such as the cardiomyopathies, congenital septal defects, aneurysms of the thoracic aorta, and cardiac remodeling in heart failure.
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4
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Sousa AA, Leapman RD. Development and application of STEM for the biological sciences. Ultramicroscopy 2012; 123:38-49. [PMID: 22749213 PMCID: PMC3500455 DOI: 10.1016/j.ultramic.2012.04.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 04/06/2012] [Accepted: 04/13/2012] [Indexed: 01/06/2023]
Abstract
The design of the scanning transmission electron microscope (STEM), as conceived originally by Crewe and coworkers, enables the highly efficient and flexible collection of different elastic and inelastic signals resulting from the interaction of a focused probe of incident electrons with a specimen. In the present paper we provide a brief review for how the STEM today can be applied towards a range of different problems in the biological sciences, emphasizing four main areas of application. (1) For three decades, the most widely used STEM technique has been the mass determination of proteins and other macromolecular assemblies. Such measurements can be performed at low electron dose by collecting the high-angle dark-field signal using an annular detector. STEM mass mapping has proven valuable for characterizing large protein assemblies such as filamentous proteins with a well-defined mass per length. (2) The annular dark-field signal can also be used to image ultrasmall, functionalized nanoparticles of heavy atoms for labeling specific amino-acid sequences in protein assemblies. (3) By acquiring electron energy loss spectra (EELS) at each pixel in a hyperspectral image, it is possible to map the distributions of specific bound elements like phosphorus, calcium and iron in isolated macromolecular assemblies or in compartments within sectioned cells. Near single atom sensitivity is feasible provided that the specimen can tolerate a very high incident electron dose. (4) Electron tomography is a new application of STEM that enables three-dimensional reconstruction of micrometer-thick sections of cells. In this technique a probe of small convergence angle gives a large depth of field throughout the thickness of the specimen while maintaining a probe diameter of <2 nm; and the use of an on-axis bright-field detector reduces the effects of beam broadening and thus improves the spatial resolution compared to that attainable by STEM dark-field tomography.
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Affiliation(s)
- Alioscka A. Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Richard D. Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
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5
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Müller SA, Engel A. Looking back at a quarter-century of research at the Maurice E. Müller Institute for Structural Biology. J Struct Biol 2011; 177:3-13. [PMID: 22115996 DOI: 10.1016/j.jsb.2011.11.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 11/04/2011] [Accepted: 11/05/2011] [Indexed: 10/15/2022]
Abstract
The Maurice E. Müller Institute, embedded in the infrastructure of the Biozentrum, University of Basel, was founded in 1985 and financed by the Maurice E. Müller Foundation of Switzerland. For 26 years its two founders, Ueli Aebi and Andreas Engel, pursued the vision of integrated structural biology. This paper reviews selected publications issuing from the Maurice E. Müller Institute for Structural Biology and marks the end of this era.
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Affiliation(s)
- Shirley A Müller
- Center for Cellular Imaging and Nano Analytics, Biozentrum, University of Basel, Mattenstrasse 26, CH-4058 Basel, Switzerland
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6
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Molecular structure of sarcomere-to-membrane attachment at M-Lines in C. elegans muscle. J Biomed Biotechnol 2010; 2010:864749. [PMID: 20414365 PMCID: PMC2857872 DOI: 10.1155/2010/864749] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/30/2010] [Indexed: 01/09/2023] Open
Abstract
C. elegans is an excellent model for studying nonmuscle cell focal adhesions and the analogous muscle cell attachment structures. In the major striated muscle of this nematode, all of the M-lines and the Z-disk analogs (dense bodies) are attached to the muscle cell membrane and underlying extracellular matrix. Accumulating at these sites are many proteins associated with integrin. We have found that nematode M-lines contain a set of protein complexes that link integrin-associated proteins to myosin thick filaments. We have also obtained evidence for intriguing additional functions for these muscle cell attachment proteins.
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Determination of the mobility of novel and established Caenorhabditis elegans sarcomeric proteins in vivo. Eur J Cell Biol 2010; 89:437-48. [PMID: 20226563 DOI: 10.1016/j.ejcb.2009.11.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 11/02/2009] [Accepted: 11/11/2009] [Indexed: 11/23/2022] Open
Abstract
A screen was instigated to identify novel protein components of the Caenorhabditis elegans sarcomere. The subcellular localisation of full-length GFP fusion proteins was examined, in transgenic animals, for 62 essentially uncharacterized genes thought to be expressed within bodywall muscle cells. Three genes, T03G6.3, C46G7.2 and K04A8.6, were identified for further study. K04A8.6::GFP only displayed a regular sarcomeric distribution sporadically. However, C46G7.2::GFP localised to the centre of A-bands and dense bodies and T03G6.3::GFP localised in the I-band, of the bodywall muscle sarcomeres, consistently. This success with such a small screen suggests that there are further minor components of the C. elegans sarcomere yet to be discovered. Fluorescence Recovery After Photobleaching (FRAP) was applied to live transgenic individuals to assess the mobility of T03G6.3 and C46G7.2 and other well-known constituents of the sarcomere in vivo. Proteins associated with the thin filaments showed dynamic exchange whilst those associated with thick filaments appeared more static. This is the first demonstration that there are sarcomeric proteins in C. elegans muscle cells in dynamic exchange and that the rates of exchange in vivo correspond in general terms with observations in other experimental systems.
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Krzyzánek V, Müller SA, Engel A, Reichelt R. MASDET-A fast and user-friendly multiplatform software for mass determination by dark-field electron microscopy. J Struct Biol 2008; 165:78-87. [PMID: 19041401 DOI: 10.1016/j.jsb.2008.10.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 10/10/2008] [Accepted: 10/16/2008] [Indexed: 11/28/2022]
Abstract
Electron microscopy has been used to measure the mass of biological nanoparticles since the early 60s, and is the only way to obtain the mass of large structures or parameters such as the mass-per-length of filaments. The ability of this method to sort heterogeneous samples both in terms of mass and shape promises to make it a key tool for proteomics down to the single cell level. A new multiplatform software package, MASDET, that can be run under MATLAB or as a standalone program is described. Based on a user-friendly graphical interface MASDET streamlines mass evaluation and greatly increases the speed of required optimisation procedures. Importantly, the immediate application of Monte-Carlo simulations to describe multiple scattering is possible, allowing the mass analysis of thicker samples and the generation of mass thickness maps.
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Affiliation(s)
- Vladislav Krzyzánek
- Institute of Medical Physics and Biophysics, Universitätsklinikum Münster, University of Münster, Germany.
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Hooper SL, Hobbs KH, Thuma JB. Invertebrate muscles: thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle. Prog Neurobiol 2008; 86:72-127. [PMID: 18616971 PMCID: PMC2650078 DOI: 10.1016/j.pneurobio.2008.06.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 05/08/2008] [Accepted: 06/12/2008] [Indexed: 11/26/2022]
Abstract
This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vertebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca(++) binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.
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Affiliation(s)
- Scott L. Hooper
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
| | - Kevin H. Hobbs
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
| | - Jeffrey B. Thuma
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
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Miller RK, Qadota H, Mercer KB, Gernert KM, Benian GM. UNC-98 and UNC-96 interact with paramyosin to promote its incorporation into thick filaments of Caenorhabditis elegans. Mol Biol Cell 2008; 19:1529-39. [PMID: 18256289 DOI: 10.1091/mbc.e07-07-0723] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mutations in unc-96 or -98 cause reduced motility and a characteristic defect in muscle structure: by polarized light microscopy birefringent needles are found at the ends of muscle cells. Anti-paramyosin stains the needles in unc-96 and -98 mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96, and -98 animals. Anti-UNC-98 and anti-paramyosin colocalize in the paramyosin accumulations of missense alleles of unc-15 (encodes paramyosin). Anti-UNC-96 and anti-UNC-98 have diffuse localization within muscles of unc-15 null mutants. By immunoblot, in the absence of paramyosin, UNC-98 is diminished, whereas in paramyosin missense mutants, UNC-98 is increased. unc-98 and -15 or unc-96 and -15 interact genetically either as double heterozygotes or as double homozygotes. By yeast two-hybrid assay and ELISAs using purified proteins, UNC-98 interacts with paramyosin residues 31-693, whereas UNC-96 interacts with a separate region of paramyosin, residues 699-798. The importance of surface charge of this 99 residue region for UNC-96 binding was shown. Paramyosin lacking the C-terminal UNC-96 binding region fails to localize throughout A-bands. We propose a model in which UNC-98 and -96 may act as chaperones to promote the incorporation of paramyosin into thick filaments.
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Affiliation(s)
- Rachel K Miller
- Department of Pathology, Graduate Division of Biological and Biomedical Sciences, and BIMCORE (Molecular Graphics), Emory University, Atlanta, GA 30322, USA
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Mercer KB, Miller RK, Tinley TL, Sheth S, Qadota H, Benian GM. Caenorhabditis elegans UNC-96 is a new component of M-lines that interacts with UNC-98 and paramyosin and is required in adult muscle for assembly and/or maintenance of thick filaments. Mol Biol Cell 2006; 17:3832-47. [PMID: 16790495 PMCID: PMC1593161 DOI: 10.1091/mbc.e06-02-0144] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
To gain further insight into the molecular architecture, assembly, and maintenance of the sarcomere, we have carried out a molecular analysis of the UNC-96 protein in the muscle of Caenorhabditis elegans. By polarized light microscopy of body wall muscle, unc-96 mutants display reduced myofibrillar organization and characteristic birefringent "needles." By immunofluorescent staining of known myofibril components, unc-96 mutants show major defects in the organization of M-lines and in the localization of a major thick filament component, paramyosin. In unc-96 mutants, the birefringent needles, which contain both UNC-98 and paramyosin, can be suppressed by starvation or by exposure to reduced temperature. UNC-96 is a novel approximately 47-kDa polypeptide that has no recognizable domains. Antibodies generated to UNC-96 localize the protein to the M-line, a region of the sarcomere in which thick filaments are cross-linked. By genetic and biochemical criteria, UNC-96 interacts with UNC-98, a previously described component of M-lines, and paramyosin. Additionally, UNC-96 copurifies with native thick filaments. A model is presented in which UNC-96 is required in adult muscle to promote thick filament assembly and/or maintenance.
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Affiliation(s)
| | - Rachel K. Miller
- *Department of Pathology and
- Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322
| | - Tina L. Tinley
- *Department of Pathology and
- Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322
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Liu H, Miller MS, Swank DM, Kronert WA, Maughan DW, Bernstein SI. Paramyosin phosphorylation site disruption affects indirect flight muscle stiffness and power generation in Drosophila melanogaster. Proc Natl Acad Sci U S A 2005; 102:10522-7. [PMID: 16020538 PMCID: PMC1180758 DOI: 10.1073/pnas.0500945102] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The phosphoprotein paramyosin is a major structural component of invertebrate muscle thick filaments. To investigate the importance of paramyosin phosphorylation, we produced transgenic Drosophila melanogaster in which one, three, or four phosphorylatable serine residues in the N-terminal nonhelical domain were replaced by alanines. Depending on the residues mutated, transgenic lines were either unaffected or severely flight impaired. Flight-impaired strains had decreases in the most acidic paramyosin isoforms, with a corresponding increase in more basic isoforms. Surprisingly, ultrastructure of indirect flight muscle myofibrils was normal, indicating N-terminal phosphorylation is not important for myofibril assembly. However, mechanical studies of active indirect flight muscle fibers revealed that phosphorylation site mutations reduced elastic and viscous moduli by 21-59% and maximum power output by up to 42%. Significant reductions also occurred under relaxed and rigor conditions, indicating that the phosphorylation-dependent changes are independent of strong crossbridge attachment and likely arise from alterations in thick filament backbone properties. Further, normal crossbridge kinetics were observed, demonstrating that myosin motor function is unaffected in the mutants. We conclude that N-terminal phosphorylation of Drosophila paramyosin is essential for optimal force and oscillatory power transduction within the muscle fiber and is key to the high passive stiffness of asynchronous insect flight muscles. Phosphorylation may reinforce interactions between myosin rod domains, enhance thick filament connections to the central M-line of the sarcomere and/or stabilize thick filament interactions with proteins that contribute to fiber stiffness.
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Affiliation(s)
- Hongjun Liu
- Department of Biology and Molecular Biology Institute, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4614, USA
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White GE, Petry CM, Schachat F. The pathway of myofibrillogenesis determines the interrelationship between myosin and paramyosin synthesis in Caenorhabditis elegans. J Exp Biol 2003; 206:1899-906. [PMID: 12728011 DOI: 10.1242/jeb.00377] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Examination of null mutants in myosin B and paramyosin yields insights into the complex mechanisms that regulate expression of the three major components of Caenorhabditis elegans body-wall muscle thick filaments myosin A, myosin B and paramyosin. In the absence of myosin B, paramyosin accumulation is reduced, although neither its synthesis nor that of myosin A is affected. This implies that the interaction of myosin B with paramyosin inhibits paramyosin degradation. By contrast, the absence of paramyosin results in reduced synthesis and accumulation of myosin B but has no effect on myosin A synthesis. The non-reciprocal effects of the null mutants on turnover and synthesis are best understood as an epigenetic phenomenon that reflects the pathway of thick filament assembly. The synthesis of myosin A and paramyosin, which are involved in the initial steps of thick filament formation, is independent of myosin B; however, a properly assembled paramyosin-containing thick filament core is essential for efficient synthesis of myosin B.
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Affiliation(s)
- Glenn E White
- Department of Cell Biology-Box 3011, Duke University Medical School, Durham, NC 27710, USA
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Liu H, Mardahl-Dumesnil M, Sweeney ST, O'Kane CJ, Bernstein SI. Drosophila paramyosin is important for myoblast fusion and essential for myofibril formation. J Cell Biol 2003; 160:899-908. [PMID: 12642615 PMCID: PMC2173770 DOI: 10.1083/jcb.200208180] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Paramyosin is a major structural protein of thick filaments in invertebrate muscles. Coiled-coil dimers of paramyosin form a paracrystalline core of these filaments, and the motor protein myosin is arranged on the core surface. To investigate the function of paramyosin in myofibril assembly and muscle contraction, we functionally disrupted the Drosophila melanogaster paramyosin gene by mobilizing a P element located in its promoter region. Homozygous paramyosin mutants die at the late embryo stage. Mutants display defects in both myoblast fusion and in myofibril assembly in embryonic body wall muscles. Mutant embryos have an abnormal body wall muscle fiber pattern arising from defects in myoblast fusion. In addition, sarcomeric units do not assemble properly and muscle contractility is impaired. We confirmed that these defects are paramyosin-specific by rescuing the homozygous paramyosin mutant to adulthood with a paramyosin transgene. Antibody analysis of normal embryos demonstrated that paramyosin accumulates as a cytoplasmic protein in early embryo development before assembling into thick filaments. We conclude that paramyosin plays an unexpected role in myoblast fusion and is important for myofibril assembly and muscle contraction.
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Affiliation(s)
- Hongjun Liu
- Dept. of Biology, San Diego State University, 5500 Campanile Dr., Life Sciences 371, San Diego, CA 92182-4614, USA.
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