Cortical condensates, transient punctate-like structures rich in actin and the actin nucleation pathway member N-WASP, form during activation of the actin cortex in the C. elegans oocyte. Their emergence and spontaneous dissolution is linked to a phase separation process driven by chemical kinetics. However, the physical process that drives the onset of cortical condensate formation near membranes remains unexplored. Here, using a reconstituted phase separation assay of cortical condensate proteins, we demonstrate that the key component, NWASP, can collectively undergo surface condensation on supported lipid bilayers via a prewetting transition. Actin partitions into the condensates, where it polymerizes and counteracts the N-WASP prewetting transition. Taken together, the dynamics of condensate-assisted cortex formation appear to be controlled by a balance between surface-assisted condensate formation and polymer-driven condensate dissolution. This opens new perspectives for understanding how the formation of complex intracellular structures is affected and controlled by phase separation.

中文翻译：

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肌动蛋白聚合抵消 N-WASP 在支持的脂质双层上的预润湿

皮质凝结物是富含肌动蛋白和肌动蛋白成核途径成员 N-WASP 的瞬时点状结构，是在线虫卵母细胞中肌动蛋白皮质激活过程中形成的。它们的出现和自发溶解与化学动力学驱动的相分离过程有关。然而，驱动膜附近皮质冷凝物形成的物理过程仍未被探索。在这里，使用皮质凝聚蛋白的重构相分离测定，我们证明了关键成分 NWASP 可以通过预润湿转变共同在支持的脂质双层上进行表面凝聚。肌动蛋白分配到凝结物中，在凝结物中聚合并抵消 N-WASP 预润湿转变。总的来说，冷凝物辅助皮层形成的动力学似乎是由表面辅助冷凝物形成和聚合物驱动的冷凝物溶解之间的平衡控制的。这为理解相分离如何影响和控制复杂细胞内结构的形成开辟了新的视角。