Filopodia act as phagocytic tentacles and pull with discrete steps and a load-dependent velocity
Filopodia act as phagocytic tentacles and pull with discrete steps and a load-dependent velocity
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DOI：
10.1073/pnas.0702449104
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发表时间：
2007-07-10
影响因子：
11.1
通讯作者：
Rohrbach, Alexander
中科院分区：
文献类型：
--
作者：
Kress, Holger;Stelzer, Ernst H. K.;Rohrbach, Alexander
丝状足是细胞表面的细刺状突起，含有平行的肌动蛋白丝束。到目前为止，对丝状伪足动力学的研究主要是利用荧光和差示干涉对比（DIC）显微镜在重叠贴壁丝状伪足细胞运动的背景下进行的。在这项研究中，我们使用光学陷阱和纳米精度的干涉粒子跟踪来测量巨噬细胞丝状足的三维动力学，这些丝状足不附着在平面上。我们发现丝状足就像细胞的触手一样：在与一个粒子结合几秒钟后，丝状足就会缩回，把被结合的粒子拉向细胞。我们观察到f -actin依赖的丝状足逐步收缩，平均步长为36 nm，表明丝状足牵拉过程中存在分子运动活动。值得注意的是，这种细胞内的步进运动，在高达19 pN的反作用力下被测量到，通过丝状的f -肌动蛋白束和细胞膜传递到细胞外的跟踪颗粒。拉力在很大程度上取决于反作用力，在< 1 pN的力下，拉力在600 nm/s之间，在> - 15 pN的力下，拉力在40 nm/s左右。这一结果为先前文献报道的丝状回缩速度的显著差异提供了解释。测得的丝线回缩力-速度关系与力相关的多运动动力学模型一致。
Filopodia are thin, spike-like cell surface protrusions containing bundles of parallel actin filaments. So far, filopodial dynamics has mainly been studied in the context of cell motility on coverslip-adherent filopodia by using fluorescence and differential interference contrast (DIC) microscopy. In this study, we used an optical trap and interferometric particle tracking with nanometer precision to measure the three-dimensional dynamics of macrophage filopodia, which were not attached to flat surfaces. We found that filopodia act as cellular tentacles: a few seconds after binding to a particle, filopodia retract and pull the bound particle toward the cell. We observed F-actin-dependent stepwise retraction of filopodia with a mean step size of 36 nm, suggesting molecular motor activity during filopodial pulling. Remarkably, this intracellular stepping motion, which was measured at counteracting forces of up to 19 pN, was transmitted to the extracellular tracked particle via the filopodial F-actin bundle and the cell membrane. The pulling velocity depended strongly on the counteracting force and ranged between 600 nm/s at forces < 1 pN and approximate to 40 nm/s at forces > 15 pN. This result provides an explanation of the significant differences in filopodial retraction velocities previously reported in the literature. The measured filopodial retraction force-velocity relationship is in agreement with a model for force-dependent multiple motor kinetics.