Dataset Information

Myosin transducer mutations differentially affect motor function, myofibril structure, and the performance of skeletal and cardiac muscles.

ABSTRACT: 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.

SUBMITTER: Cammarato A

PROVIDER: S-EPMC2230588 | biostudies-literature | 2008 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Myosin transducer mutations differentially affect motor function, myofibril structure, and the performance of skeletal and cardiac muscles.

Cammarato Anthony A Dambacher Corey M CM Knowles Aileen F AF Kronert William A WA Bodmer Rolf R Ocorr Karen K Bernstein Sanford I SI

Molecular biology of the cell 20071128 2

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 ...[more]

PMID: 18045988

Similar Datasets

Project description:Muscle myosin heavy chain (MHC) rod domains intertwine to form alpha-helical coiled-coil dimers; these subsequently multimerize into thick filaments via electrostatic interactions. The subfragment 2/light meromyosin "hinge" region of the MHC rod, located in the C-terminal third of heavy meromyosin, may form a less stable coiled-coil than flanking regions. Partial "melting" of this region has been proposed to result in a helix to random-coil transition. A portion of the Drosophila melanogaster MHC hinge is encoded by mutually exclusive alternative exons 15a and 15b, the use of which correlates with fast (hinge A) or slow (hinge B) muscle physiological properties. To test the functional significance of alternative hinge regions, we constructed transgenic fly lines in which fast muscle isovariant hinge A was switched for slow muscle hinge B in the MHC isoforms of indirect flight and jump muscles. Substitution of the slow muscle hinge B impaired flight ability, increased sarcomere lengths by approximately 13% and resulted in minor disruption to indirect flight muscle sarcomeric structure compared with a transgenic control. With age, residual flight ability decreased rapidly and myofibrils developed peripheral defects. Computational analysis indicates that hinge B has a greater coiled-coil propensity and thus reduced flexibility compared to hinge A. Intriguingly, the MHC rod with hinge B was approximately 5 nm longer than myosin with hinge A, consistent with the more rigid coiled-coil conformation predicted for hinge B. Our study demonstrates that hinge B cannot functionally substitute for hinge A in fast muscle types, likely as a result of differences in the molecular structure of the rod, subtle changes in myofibril structure and decreased ability to maintain sarcomere structure in indirect flight muscle myofibrils. Thus, alternative hinges are important in dictating the distinct functional properties of myosin isoforms and the muscles in which they are expressed.

Project description:BackgroundUnc-45 is a myosin chaperone and a Hsp90 co-chaperone that plays a key role in muscle development. Genetic and biochemical studies in C. elegans have demonstrated that Unc-45 facilitates the process of myosin folding and assembly in body wall muscles. Loss or overexpression of Unc-45 in C. elegans results in defective myofibril organization. In the zebrafish Danio rerio, unc-45b, a homolog of C. elegans unc-45, is expressed in both skeletal and cardiac muscles. Earlier studies indicate that mutation or knockdown of unc-45b expression in zebrafish results in a phenotype characterized by a loss of both thick and thin filament organization in skeletal and cardiac muscle. The effects of unc-45b knockdown on other sarcomeric structures and the phenotype of Unc-45b overexpression, however, are poorly understood in vertebrates.ResultsBoth knockdown and overexpression provide useful tools to study gene function during animal development. Using such methods, we characterized the role of Unc-45b in myofibril assembly of skeletal muscle in Danio rerio. We showed that, in addition to thick and thin filament defects, knockdown of unc-45b expression disrupted sarcomere organization in M-lines and Z-lines of skeletal muscles in zebrafish embryos. Western blotting analysis showed that myosin protein levels were significantly decreased in unc-45b knockdown embryos. Similarly, embryos overexpressing Unc-45b also exhibited severely disorganized myosin thick filaments. Disruption of thick filament organization by Unc-45b overexpression depends on the C-terminal UCS domain in Unc-45b required for interaction with myosin. Deletion of the C-terminal UCS domain abolished the disruptive activity of Unc-45b in myosin thick filament organization. In contrast, deletion of the N-terminal TPR domain required for binding with Hsp90α had no effect.ConclusionCollectively, these studies indicate that the expression levels of Unc-45b must be precisely regulated to ensure normal myofibril organization. Loss or overexpression of Unc-45b leads to defective myofibril organization.

Dataset Information

Myosin transducer mutations differentially affect motor function, myofibril structure, and the performance of skeletal and cardiac muscles.

Publications

Myosin transducer mutations differentially affect motor function, myofibril structure, and the performance of skeletal and cardiac muscles.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets