Cell polarity underlies key processes in all cells, including growth, differentiation and division. In the bacterium Myxococcus xanthus, front-rear polarity is crucial for motility. Notably, this polarity can be inverted, independent of the cell-cycle, by chemotactic signaling. However, a precise understanding of the protein network that establishes polarity and allows for its inversion has remained elusive. Here, we use a combination of quantitative experiments and data-driven theory to unravel the complex interplay between the three key components of the M. xanthus polarity module. By studying each of these components in isolation and their effects as we systematically reconstruct the system, we deduce the network of effective interactions between the polarity proteins. RomR lies at the root of this network, promoting polar localization of the other components, while polarity arises from interconnected negative and positive feedbacks mediated by the small GTPase MglA and its cognate GAP MglB, respectively. We rationalize this network topology as operating as a spatial toggle switch, providing stable polarity for persistent cell movement whilst remaining responsive to chemotactic signaling and thus capable of polarity inversions. Our results have implications not only for the understanding of polarity and motility in M. xanthus but also, more broadly, for dynamic cell polarity.

细胞极性是所有细胞的关键过程的基础，包括生长，分化和分裂。在黄色葡萄球菌中，前后极性对于运动至关重要。值得注意的是，该极性可以通过趋化信号转导而与细胞周期无关地反转。然而，对建立极性并允许其反转的蛋白质网络的精确了解仍然难以捉摸。在这里，我们结合了定量实验和数据驱动理论，以阐明M的三个关键组成部分之间的复杂相互作用。黄原木极性模块。通过孤立地研究这些成分中的每一个及其在系统地重建系统时的作用，我们得出了极性蛋白质之间有效相互作用的网络。RomR位于该网络的根部，促进其他组件的极性定位，而极性则分别由小​​GTPase MglA及其关联的GAP MglB介导的相互负反馈和正反馈产生。我们将这种网络拓扑合理化为空间切换开关，为稳定的细胞运动提供稳定的极性，同时保持对趋化信号的响应，因此能够进行极性反转。我们的研究结果不仅对理解M的极性和运动有影响。黄原木 而且，更广泛地说，是动态细胞极性。