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Title: Aging Enhances Indirect Flight Muscle Fiber Performance yet Decreases Flight Ability in Drosophila

Abstract

We investigated the effects of aging on Drosophila melanogaster indirect flight muscle from the whole organism to the actomyosin cross-bridge. Median-aged (49-day-old) flies were flight impaired, had normal myofilament number and packing, barely longer sarcomeres, and slight mitochondrial deterioration compared with young (3-day-old) flies. Old (56-day-old) flies were unable to beat their wings, had deteriorated ultrastructure with severe mitochondrial damage, and their skinned fibers failed to activate with calcium. Small-amplitude sinusoidal length perturbation analysis showed median-aged indirect flight muscle fibers developed greater than twice the isometric force and power output of young fibers, yet cross-bridge kinetics were similar. Large increases in elastic and viscous moduli amplitude under active, passive, and rigor conditions suggest that median-aged fibers become stiffer longitudinally. Small-angle x-ray diffraction indicates that myosin heads move increasingly toward the thin filament with age, accounting for the increased transverse stiffness via cross-bridge formation. We propose that the observed protein composition changes in the connecting filaments, which anchor the thick filaments to the Z-disk, produce compensatory increases in longitudinal stiffness, isometric tension, power and actomyosin interaction in aging indirect flight muscle. We also speculate that a lack of MgATP due to damaged mitochondria accounts for the decreased flight performance.

Authors:
; ; ; ; ; ; ;  [1];  [2]
  1. (IIT)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1006827
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biophys. J.; Journal Volume: 95; Journal Issue: 2008
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; AGING; AMPLITUDES; CALCIUM; DROSOPHILA; FIBERS; FLEXIBILITY; FLIES; KINETICS; MITOCHONDRIA; MUSCLES; MYOSIN; PERFORMANCE; PROTEINS; X-RAY DIFFRACTION

Citation Formats

Miller, Mark S., Lekkas, Panagiotis, Braddock, Joan M., Farman, Gerrie P., Ballif, Bryan A., Irving, Thomas C., Maughan, David W., Vigoreaux, Jim O., and Vermont). Aging Enhances Indirect Flight Muscle Fiber Performance yet Decreases Flight Ability in Drosophila. United States: N. p., 2008. Web. doi:10.1529/biophysj.108.130005.
Miller, Mark S., Lekkas, Panagiotis, Braddock, Joan M., Farman, Gerrie P., Ballif, Bryan A., Irving, Thomas C., Maughan, David W., Vigoreaux, Jim O., & Vermont). Aging Enhances Indirect Flight Muscle Fiber Performance yet Decreases Flight Ability in Drosophila. United States. doi:10.1529/biophysj.108.130005.
Miller, Mark S., Lekkas, Panagiotis, Braddock, Joan M., Farman, Gerrie P., Ballif, Bryan A., Irving, Thomas C., Maughan, David W., Vigoreaux, Jim O., and Vermont). Thu . "Aging Enhances Indirect Flight Muscle Fiber Performance yet Decreases Flight Ability in Drosophila". United States. doi:10.1529/biophysj.108.130005.
@article{osti_1006827,
title = {Aging Enhances Indirect Flight Muscle Fiber Performance yet Decreases Flight Ability in Drosophila},
author = {Miller, Mark S. and Lekkas, Panagiotis and Braddock, Joan M. and Farman, Gerrie P. and Ballif, Bryan A. and Irving, Thomas C. and Maughan, David W. and Vigoreaux, Jim O. and Vermont)},
abstractNote = {We investigated the effects of aging on Drosophila melanogaster indirect flight muscle from the whole organism to the actomyosin cross-bridge. Median-aged (49-day-old) flies were flight impaired, had normal myofilament number and packing, barely longer sarcomeres, and slight mitochondrial deterioration compared with young (3-day-old) flies. Old (56-day-old) flies were unable to beat their wings, had deteriorated ultrastructure with severe mitochondrial damage, and their skinned fibers failed to activate with calcium. Small-amplitude sinusoidal length perturbation analysis showed median-aged indirect flight muscle fibers developed greater than twice the isometric force and power output of young fibers, yet cross-bridge kinetics were similar. Large increases in elastic and viscous moduli amplitude under active, passive, and rigor conditions suggest that median-aged fibers become stiffer longitudinally. Small-angle x-ray diffraction indicates that myosin heads move increasingly toward the thin filament with age, accounting for the increased transverse stiffness via cross-bridge formation. We propose that the observed protein composition changes in the connecting filaments, which anchor the thick filaments to the Z-disk, produce compensatory increases in longitudinal stiffness, isometric tension, power and actomyosin interaction in aging indirect flight muscle. We also speculate that a lack of MgATP due to damaged mitochondria accounts for the decreased flight performance.},
doi = {10.1529/biophysj.108.130005},
journal = {Biophys. J.},
number = 2008,
volume = 95,
place = {United States},
year = {Thu Oct 02 00:00:00 EDT 2008},
month = {Thu Oct 02 00:00:00 EDT 2008}
}
  • The indirect flight muscle (IFM) of insects is characterized by a near crystalline myofilament lattice structure that likely evolved to achieve high power output. In Drosophila IFM, the myosin rod binding protein flightin plays a crucial role in thick filament organization and sarcomere integrity. Here we investigate the extent to which the COOH terminus of flightin contributes to IFM structure and mechanical performance using transgenic Drosophila expressing a truncated flightin lacking the 44 COOH-terminal amino acids (fln{sup {Delta}C44}). Electron microscopy and X-ray diffraction measurements show decreased myofilament lattice order in the fln{sup {Delta}C44} line compared with control, a transgenic flightin-nullmore » rescued line (fln{sup +}). fln{sup {Delta}C44} fibers produced roughly 1/3 the oscillatory work and power of fln{sup +}, with reduced frequencies of maximum work (123 Hz vs. 154 Hz) and power (139 Hz vs. 187 Hz) output, indicating slower myosin cycling kinetics. These reductions in work and power stem from a slower rate of cross-bridge recruitment and decreased cross-bridge binding in fln{sup {Delta}C44} fibers, although the mean duration of cross-bridge attachment was not different between both lines. The decreases in lattice order and myosin kinetics resulted in fln{sup {Delta}C44} flies being unable to beat their wings. These results indicate that the COOH terminus of flightin is necessary for normal myofilament lattice organization, thereby facilitating the cross-bridge binding required to achieve high power output for flight.« less
  • The control of expression of the Drosophila melanogaster tropomyosin I (TmI) gene has been investigated by P-element transformation and rescue of the flightless TmI mutant strain, Ifm(3)3. To localize cis-acting DNA sequences that control TmI gene expression, Ifm(3)3 flies were transformed with P-element plasmids containing various deletions and rearrangements of the TmI gene. The effects of these mutations on TmI gene expression were studied by analyzing both the extent of rescue of the Ifm(3)3 mutant phenotypes and determining TmI RNA levels in the transformed flies by primer extension analysis. The results of this analysis indicate that a region located withinmore » intron 1 of the gene is necessary and sufficient for directing muscle-specific TmI expression in the adult fly. This intron region has characteristics of a muscle regulatory enhancer element that can function in conjunction with the heterologous nonmuscle hsp70 promoter to promote rescue of the mutant phenotypes and to direct expression of an hsp70-Escherichia coli lacZ reporter gene in adult muscle. The enhancer can be subdivided further into two domains of activity based on primer extension analysis of TmI mRNA levels and on the rescue of mutant phenotypes.« less
  • We have analyzed the ultrastructure of indirect flight muscles in Drosophila pupae heterozygous for the mutation Mhc{sup M66}, which is a cold-sensitive allele of locus Mhc (Myosin heavy chain). We found that initially the differentiation of the muscle fiber in the mutant does not differ from that of the wild type. The first visible changes (loss of individual myosin protofibrils) appear in myofibrils reaching a certain size. Disintegration of contractile machinery progresses with the increase in the size of myofibrils. We discuss possible mechanisms of triggering and progression of these destructive processes during ontogenesis. 26 refs., 2 figs.
  • Mechanisms involved in establishing the organization and numbers of fibres in a muscle are not completely understood. During Drosophila indirect flight muscle (IFM) formation, muscle growth is achieved by both incorporating hundreds of nuclei, and hypertrophy. As a result, IFMs provide a good model with which to understand the mechanisms that govern overall muscle organization and growth. We present a detailed analysis of the organization of dorsal longitudinal muscles (DLMs), a subset of the IFMs. We show that each DLM is similar to a vertebrate fascicle and consists of multiple muscle fibres. However, increased fascicle size does not necessarily changemore » the number of constituent fibres, but does increase the number of myofibrils packed within the fibres. We also find that altering the number of myoblasts available for fusion changes DLM fascicle size and fibres are loosely packed with myofibrils. Additionally, we show that knock down of genes required for mitochondrial fusion causes a severe reduction in the size of DLM fascicles and fibres. Our results establish the organization levels of DLMs and highlight the importance of the appropriate number of nuclei and mitochondrial fusion in determining the overall organization, growth and size of DLMs. - Highlights: • Drosophila dorsal longitudinal muscles are similar to vertebrate skeletal muscles. • A threshold number of myoblasts governs the organization of a fibre and its size. • Mitochondrial fusion defect leads to abnormal fibre growth and organization.« less
  • X-ray diffraction of the indirect flight muscle (IFM) in living Drosophila at rest and electron microscopy of intact and glycerinated IFM was used to compare the effects of mutations in the regulatory light chain (RLC) on sarcomeric structure. Truncation of the RLC N-terminal extension (Dmlc2{sup {Delta}2-46}) or disruption of the phosphorylation sites by substituting alanines (Dmlc2{sup S66A, S67A}) decreased the equatorial intensity ratio (I{sub 20}/I{sub 10}), indicating decreased myosin mass associated with the thin filaments. Phosphorylation site disruption (Dmlc2{sup S66A, S67A}), but not N-terminal extension truncation (Dmlc2{sup {Delta}2-46}), decreased the 14.5 nm reflection intensity, indicating a spread of the axialmore » distribution of the myosin heads. The arrangement of thick filaments and myosin heads in electron micrographs of the phosphorylation mutant (Dmlc2{sup S66A, S67A}) appeared normal in the relaxed and rigor states, but when calcium activated, fewer myosin heads formed cross-bridges. In transgenic flies with both alterations to the RLC (Dmlc2{sup {Delta}2-46; S66A, S67A}), the effects of the dual mutation were additive. The results suggest that the RLC N-terminal extension serves as a 'tether' to help pre-position the myosin heads for attachment to actin, while phosphorylation of the RLC promotes head orientations that allow optimal interactions with the thin filament.« less