负载波动驱动子网络增长
Load fluctuations drive actin network growth
摘要：
肌动蛋白丝网络的生长是一个基本的生物学过程，驱动各种细胞和细胞内的运动。在运动过程中，真核细胞和胞内病原体由成核促进因子组织的肌动蛋白网络推动，这些因子触发网络中现有细丝一侧的新生细丝形成。一个布朗棘轮（BR）机制已被提出耦合肌动蛋白聚合细胞运动，其中热运动被纠正的肌动蛋白单体在生长丝的末端。在这里，通过使用三维激光跟踪跟踪肌动蛋白推进的微球，我们发现粘附在不断增长的网络上的珠子通过一个物体-波动的BR移动。速度随热波动的幅度而变化，与BR预测的粘度成反比。此外，运动是跳跃式的，具有与时间相关的步长的广泛分布。这些数据指向一个模型，其中微球或整个肌动蛋白网络的热波动，而不是个别丝，支配运动。这一结论是支持的蒙特卡罗模拟的粘附-为基础的BR，并建议在控制肌动蛋白为基础的细胞突起的膜张力的重要作用。
英文摘要：
The growth of actin filament networks is a fundamental biological process that drives a variety of cellular and intracellular motions. During motility, eukaryotic cells and intracellular pathogens are propelled by actin networks organized by nucleation-promoting factors, which trigger the formation of nascent filaments off the side of existing filaments in the network. A Brownian ratchet (BR) mechanism has been proposed to couple actin polymerization to cellular movements, whereby thermal motions are rectified by the addition of actin monomers at the end of growing filaments. Here, by following actin--propelled microspheres using three--dimensional laser tracking, we find that beads adhered to the growing network move via an object--fluctuating BR. Velocity varies with the amplitude of thermal fluctuation and inversely with viscosity as predicted for a BR. In addition, motion is saltatory with a broad distribution of step sizes that is correlated in time. These data point to a model in which thermal fluctuations of the microsphere or entire actin network, and not individual filaments, govern motility. This conclusion is supported by Monte Carlo simulations of an adhesion--based BR and suggests an important role for membrane tension in the control of actin--based cellular protrusions.
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