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首页> 外文期刊>American Journal of Physiology >Mutations that affect flightin expression in Drosophila alter the viscoelastic properties of flight muscle fibers.
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Mutations that affect flightin expression in Drosophila alter the viscoelastic properties of flight muscle fibers.

机译：影响果蝇中Flightin表达的突变会改变飞行肌纤维的粘弹性。

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摘要

Striated muscles across phyla share a highly conserved sarcomere design yet exhibit broad diversity in contractile velocity, force, power output, and efficiency. Insect asynchronous flight muscles are characterized by high-frequency contraction, endurance, and high-power output. These muscles have evolved an enhanced delayed force response to stretch that is largely responsible for their enhanced oscillatory work and power production. In this study we investigated the contribution of flightin to oscillatory work using sinusoidal analysis of fibers from three flightless mutants affecting flightin expression: 1) fln0, a flightin null mutant, 2) Mhc13, a myosin rod point mutant with reduced levels of flightin, and 3) Mhc6, a second myosin rod point mutant with reduced levels of phosphorylated flightin. Fibers from the three mutants show deficits in their passive and dynamic viscoelastic properties that are commensurate with their effect on flightin expression and result in a significant loss of oscillatory work and power. Passive tension and passive stiffness were significantly reduced in fln0 and Mhc13 but not in Mhc6. The dynamic viscous modulus was significantly reduced in the three mutants, whereas the dynamic elastic modulus was reduced in fln0 and Mhc13 but not in Mhc6. Tension generation under isometric conditions was not impaired in fln0. However, when subjected to sinusoidal length perturbations, work-absorbing processes dominated over work-producing processes, resulting in no net positive work output. We propose that flightin is a major contributor to myofilament stiffness and a key determinant of the enhanced delayed force response to stretch in Drosophila flight muscles.
机译：跨门的横纹肌具有高度保守的肌节设计，但在收缩速度，力，功率输出和效率方面表现出广泛的差异。昆虫异步飞行肌肉的特点是高频收缩，耐力和大功率输出。这些肌肉已发展出对延迟拉伸的增强的延迟力响应，这在很大程度上是其增强的振动功和动力产生的原因。在这项研究中，我们使用正弦分析对来自三个影响Flightin表达的非飞行突变体的纤维进行正弦分析，研究了Flightin对振荡工作的贡献：1）fln0（一个Flightin空突变体），2）Mhc13（一种具有降低Flightin水平的肌球蛋白杆点突变体）和3）Mhc6，第二个肌球蛋白杆点突变体，磷酸化的Flightin含量降低。来自这三个突变体的纤维显示出它们的被动和动态粘弹性性质的缺陷，这与它们对flightin表达的影响相称，并且导致振荡功和功率的显着损失。在fln0和Mhc13中，被动张力和被动刚度显着降低，而在Mhc6中则没有。动态粘度模量在三个突变体中显着降低，而动态弹性模量在fln0和Mhc13中降低，但在Mhc6中没有降低。在fln0中，等轴测条件下的张力生成不会受到影响。但是，当受到正弦波长度扰动时，吸收工作的过程比产生工作的过程要占主导地位，因此没有净正功输出。我们建议，flightin是导致肌丝僵硬的主要因素，也是决定果蝇飞行肌肉拉伸力延迟反应增强的关键因素。

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