Department of Physics, Lehigh University, Bethlehem, PA, USA.
Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
Nat Commun. 2024 Sep 27;15(1):8363. doi: 10.1038/s41467-024-52655-1.
Polarized exocytosis induced by local Cdc42 GTPase activity results in membrane flows that deplete low-mobility membrane-associated proteins. A reaction-diffusion particle model comprising Cdc42 positive feedback activation, hydrolysis by GTPase-activating proteins (GAPs), and flow-induced displacement by exo/endocytosis shows that flow-induced depletion of low mobility GAPs promotes polarization. We modified Cdc42 mobility in Schizosaccharomyces pombe by replacing its prenylation site with 1, 2 or 3 repeats of the Rit C-terminal membrane-binding domain (ritC), yielding alleles with progressively lower mobility and increased flow-coupling. While Cdc42-1ritC cells are viable and polarized, Cdc42-2ritC polarize poorly and Cdc42-3ritC are inviable, in agreement with model's predictions. Deletion of Cdc42 GAPs restores viability to Cdc42-3ritC cells, verifying the model's prediction that GAP deletion increases Cdc42 activity at the expense of polarization. Our work demonstrates how membrane flows are an integral part of Cdc42-driven pattern formation and require Cdc42-GTP to turn over faster than the surface on which it forms.
局部 Cdc42 GTP 酶活性诱导的极化胞吐作用导致膜流，从而耗尽低迁移率的膜相关蛋白。一个包含 Cdc42 正反馈激活、GTP 酶激活蛋白（GAPs）水解和胞吐/胞吞引起的流动位移的反应扩散粒子模型表明，流动诱导的低迁移率 GAP 的耗竭促进了极化。我们通过用 Rit C 末端膜结合结构域（ritC）的 1、2 或 3 个重复取代酿酒酵母的 Cdc42 的 prenylation 位点来改变 Cdc42 的迁移率，得到了迁移率逐渐降低且流动耦合增加的等位基因。虽然 Cdc42-1ritC 细胞是存活和极化的，但 Cdc42-2ritC 极化不良，Cdc42-3ritC 则是不可存活的，这与模型的预测一致。Cdc42 GAP 的缺失恢复了 Cdc42-3ritC 细胞的活力，这验证了模型的预测，即 GAP 的缺失以牺牲极化的代价增加了 Cdc42 的活性。我们的工作表明，膜流是 Cdc42 驱动的模式形成的一个组成部分，并且需要 Cdc42-GTP 比它形成的表面更快地周转。
