The orientation of cell polarity depends on the position of the centrosome, the main microtubule-organizing center (MTOC). Microtubules (MTs) transmit pushing forces to the MTOC as they grow against the cell periphery. How the actin network regulates these forces remains unclear. Here, in a cell-free assay, we used purified proteins to reconstitute the interaction of a microtubule aster with actin networks of various architectures in cell-sized microwells. In the absence of actin filaments, MTOC positioning was highly sensitive to variations in microtubule length. The presence of a bulk actin network limited microtubule displacement, and MTOCs were held in place. In contrast, the assembly of a branched actin network along the well edges centered the MTOCs by maintaining an isotropic balance of pushing forces. An anisotropic peripheral actin network caused the MTOC to decenter by focusing the pushing forces. Overall, our results show that actin networks can limit the sensitivity of MTOC positioning to microtubule length and enforce robust MTOC centering or decentering depending on the isotropy of its architecture.

中文翻译：

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肌动蛋白网络架构可以确保中心体的稳健居中或敏感偏心

细胞极性的方向取决于中心体（主要微管组织中心（MTOC））的位置。微管 (MT) 在细胞外围生长时将推力传递给 MTOC。肌动蛋白网络如何调节这些力量仍不清楚。在这里，在无细胞测定中，我们使用纯化的蛋白质来重建微管紫苑与细胞大小的微孔中各种结构的肌动蛋白网络的相互作用。在没有肌动蛋白丝的情况下，MTOC 定位对微管长度的变化高度敏感。大量肌动蛋白网络的存在限制了微管位移，并且 MTOC 被固定在适当的位置。相比之下，沿着井边缘组装的分支肌动蛋白网络通过维持推力的各向同性平衡而使 MTOC 居中。各向异性的外周肌动蛋白网络通过集中推力导致 MTOC 偏心。总的来说，我们的结果表明，肌动蛋白网络可以限制 MTOC 定位对微管长度的敏感性，并根据其结构的各向同性强制执行稳健的 MTOC 居中或偏心。