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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Forces generated during actin-based propulsion: A direct measurement by micromanipulation
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Forces generated during actin-based propulsion: A direct measurement by micromanipulation

机译：基于肌动蛋白的推进过程中产生的力：通过显微操作直接测量

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摘要

Dynamic actin networks generate forces for numerous types of movements such as lamellipodia protrusion or the motion of endocytic vesicles. The actin-based propulsive movement of Listeria monocytogenes or of functionalized microspheres have been extensively used as model systems to identify the biochemical components that are necessary for actin-based motility. However, quantitative force measurements are required to elucidate the mechanism of force generation, which is still under debate. To directly probe the forces generated in the process of actin-based propulsion, we developed a micromanipulation experiment. A comet growing from a coated polystyrene bead is held by a micropipette while the bead is attached to a force probe, by using a specially designed "flexible handle." This system allows us to apply both pulling and pushing external forces up to a few nanonewtons. By pulling the actin tail away from the bead at high speed, we estimate the elastic modulus of the gel and measure the force necessary to detach the tail from the bead. By applying a constant force in the range of -1.7 to 4.3 nN, the force-velocity relation is established. We find that the relation is linear for pulling forces and decays more weakly for pushing forces. This behavior is explained by using a dimensional elastic analysis.
机译：动态肌动蛋白网络为多种类型的运动产生力，例如片状脂膜突出或内吞小泡运动。单核细胞增生李斯特菌或功能化微球的基于肌动蛋白的推进运动已广泛用作模型系统，以鉴定基于肌动蛋白的运动所必需的生化成分。然而，需要定量的力测量来阐明力产生的机理，这仍在争论中。为了直接探究基于肌动蛋白的推进过程中产生的力，我们开发了微操纵实验。使用特殊设计的“柔性手柄”，用微移液管将由涂覆的聚苯乙烯珠子长出的彗星固定在测力仪上，然后将其固定在测力探头上。该系统允许我们将拉力和推力都施加到几纳牛顿。通过以高速将肌动蛋白尾巴拉离珠子，我们估计了凝胶的弹性模量，并测量了将尾巴与珠子分开所需的力。通过施加-1.7到4.3 nN范围内的恒定力，可以建立力-速度关系。我们发现该关系对于拉力是线性的，而对于推力则更弱。通过使用尺寸弹性分析来解释此行为。

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