Drosophila Muscle Regulation Characterized by Electron Microscopy and Three-Dimensional Reconstruction of Thin Filament Mutants

Cammarato, Anthony; Hatch, Victoria; Saide, Judith D.; Craig, Roger; Sparrow, John C.; Tobacman, Larry S.; Lehman, William

doi:10.1016/s0006-3495(04)74229-0

Cited by 37 publications

(60 citation statements)

References 45 publications

(64 reference statements)

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“…The AI for D45 hearts also increased significantly with age, but it increased by a significantly larger amount over time compared with control hearts. myosin binding sites remain unblocked in both the absence and presence of activating Ca 2ϩ (Cammarato et al, 2004). Thus, cross-bridge cycling and force generation would proceed uninhibited and may initiate IFM hypercontraction.…”

Section: Discussionmentioning

confidence: 99%

Myosin Transducer Mutations Differentially Affect Motor Function, Myofibril Structure, and the Performance of Skeletal and Cardiac Muscles

Cammarato

Dambacher

Knowles

et al. 2008

MBoC

Self Cite

116

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Striated muscle myosin is a multidomain ATP-dependent molecular motor. Alterations to various domains affect the chemomechanical properties of the motor, and they are associated with skeletal and cardiac myopathies. The myosin transducer domain is located near the nucleotide-binding site. Here, we helped define the role of the transducer by using an integrative approach to study how Drosophila melanogaster transducer mutations D45 and Mhc 5 affect myosin function and skeletal and cardiac muscle structure and performance. We found D45 (A261T) myosin has depressed ATPase activity and in vitro actin motility, whereas Mhc 5 (G200D) myosin has these properties enhanced. Depressed D45 myosin activity protects against age-associated dysfunction in metabolically demanding skeletal muscles. In contrast, enhanced Mhc 5 myosin function allows normal skeletal myofibril assembly, but it induces degradation of the myofibrillar apparatus, probably as a result of contractile disinhibition. Analysis of beating hearts demonstrates depressed motor function evokes a dilatory response, similar to that seen with vertebrate dilated cardiomyopathy myosin mutations, and it disrupts contractile rhythmicity. Enhanced myosin performance generates a phenotype apparently analogous to that of human restrictive cardiomyopathy, possibly indicating myosin-based origins for the disease. The D45 and Mhc 5 mutations illustrate the transducer's role in influencing the chemomechanical properties of myosin and produce unique pathologies in distinct muscles. Our data suggest Drosophila is a valuable system for identifying and modeling mutations analogous to those associated with specific human muscle disorders. INTRODUCTIONThe myosin molecular motor of striated muscle is a hexameric molecule composed of two myosin heavy chains (MHCs) and four light chains. The N-terminal globular motor domain is a product inhibited ATPase comprised of several communicating domains and functional units (reviewed by Holmes, 1999, 2005;. Alterations to the various domains dramatically affect the biochemical and mechanical properties of the motor in vitro, and mutations that diminish or enhance the molecular performance of myosin in vivo are associated with the pathogenesis of both skeletal and cardiac myopathies (reviewed by Sellers, 1999;Redowicz, 2002;Oldfors et al., 2004;Chang and Potter, 2005;Laing and Nowak, 2005;Tardiff, 2005;Oldfors, 2007). Central to an understanding of myosinbased myopathies is a fundamental appreciation for how depressed or enhanced molecular motor function differentially affects diverse striated muscles.Among the communicating functional units of myosin is the recently described transducer region (Coureux et al., 2004). Myosin V crystal structures reveal the transducer's central location within the motor domain near the nucleotide binding site. The transducer includes the last three strands of a seven-stranded ␤-sheet, which undergoes distortion essential for rearrangements within the nucleotide pocket during the ATPase cycle, and the loops an...

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Section: Discussionmentioning

confidence: 99%

Myosin Transducer Mutations Differentially Affect Motor Function, Myofibril Structure, and the Performance of Skeletal and Cardiac Muscles

Cammarato

Dambacher

Knowles

et al. 2008

MBoC

Self Cite

116

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“…Although there was early controversy over repeat distances and numbers of actin monomers per repeat, biochemical, X-ray, and electron microscopy work indicates that nematode (Rosenbluth, 1967), crustacea Maéda et al, 1979;Namba et al, 1980;Wray and Holmes, 1981), insect flight muscle (Hanson and Lowy, 1963;Rayns, 1972;Reedy et al, 1983b;Ruiz et al, 1998;Cammarato et al, 2004), mollusc (Bear, 1945;Selby and Bear, 1956;Worthington, 1959;Hanson and Lowy, 1963;Hanson, 1967;Lowy and Vibert, 1967;Tsuchiya et al, 1977a,b;Vibert and Craig, 1982;Egelman et al, 1983), sea urchin (Obinata et al, 1974), and annelid (Bear, 1945;Hanson and Lowy, 1963) thin filaments are very similar to vertebrate thin filaments, with the double helix repeating once every 35-40 nm in 13-15 monomers (if the fact that the two monomers in question are from different strands is ignored; Fig. 1A).…”

Section: Thin Filamentmentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

125

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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 vetebrates 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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“…Affinity of endogenous and recombinant Cdc8 tropomyosin for actin It has been suggested that acetylation stabilises Tm's coiledcoil structure at the amino terminus (Palm et al, 2003), allowing Tm dimers to interact to form filaments capable of associating with F-actin cables (Cammarato et al, 2004). We wished to explore whether acetylation could play a similar role in modifying the affinity of Cdc8 for actin and therefore the in vivo function in S. pombe.…”

Section: Cdc8 Is Acetylated In Vivomentioning

confidence: 99%

Acetylation regulates tropomyosin function in the fission yeastSchizosaccharomyces pombe

Skoumpla

Coulton

Lehman

et al. 2007

Journal of Cell Science

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121

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Tropomyosin is an evolutionarily conserved α-helical coiled-coil protein that promotes and maintains actin filaments. In yeast, Tropomyosin-stabilised filaments are used by molecular motors to transport cargoes or to generate motile forces by altering the dynamics of filament growth and shrinkage. The Schizosaccharomyces pombe tropomyosin Cdc8 localises to the cytokinetic actomyosin ring during mitosis and is absolutely required for its formation and function. We show that Cdc8 associates with actin filaments throughout the cell cycle and is subjected to post-translational modification that does not vary with cell cycle progression. At any given point in the cell cycle 80% of Cdc8 molecules are acetylated, which significantly enhances their affinity for actin. Reconstructions of electron microscopic images of actin-Cdc8 filaments establish that the majority of Cdc8 strands sit in the `closed' position on actin filaments, suggesting a role in the regulation of myosin binding. We show that Cdc8 regulates the equilibrium binding of myosin to actin without affecting the rate of myosin binding. Unacetylated Cdc8 isoforms bind actin, but have a reduced ability to regulate myosin binding to actin. We conclude that although acetylation of Cdc8 is not essential, it provides a regulatory mechanism for modulating actin filament integrity and myosin function.

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Drosophila Muscle Regulation Characterized by Electron Microscopy and Three-Dimensional Reconstruction of Thin Filament Mutants

Cited by 37 publications

References 45 publications

Myosin Transducer Mutations Differentially Affect Motor Function, Myofibril Structure, and the Performance of Skeletal and Cardiac Muscles

Myosin Transducer Mutations Differentially Affect Motor Function, Myofibril Structure, and the Performance of Skeletal and Cardiac Muscles

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Acetylation regulates tropomyosin function in the fission yeastSchizosaccharomyces pombe

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