Iwamoto Koji, Matsuoka Satomi, Ueda Masahiro
Laboratory of Single Molecule Biology, Graduate School of Science and Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Laboratory for Cell Signaling Dynamics, Center for Biosystems Dynamics Research (BDR), RIKEN, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Nat Commun. 2025 Jan 2;16(1):117. doi: 10.1038/s41467-024-55389-2.
Excitable systems of eukaryotic chemotaxis can generate asymmetric signals of Ras-GTP-enriched domains spontaneously to drive random cell migration without guidance cues. However, the molecules responsible for the spontaneous signal generation remain elusive. Here, we characterized RasGEFs encoded in Dictyostelium discoideum by live-cell imaging of the spatiotemporal dynamics of Ras-GTP and hierarchical clustering, finding that RasGEFX is primarily required for the spontaneous generation of Ras-GTP-enriched domains and is essential for random migration in combination with RasGEFB/M/U in starved cells, and they are dispensable for chemotaxis to chemoattractant cAMP. RasGEFX and RasGEFB that co-localize with Ras-GTP regulate the temporal periods and spatial sizes of the oscillatory Ras-GTP waves propagating along the membrane, respectively, and thus control the protrusions of motile cells differently, while RasGEFU and RasGEFM regulate adhesion and migration speed, respectively. Remarkably, RasGEFX is also important for Ras/PIP3-driven macropinocytosis in proliferating cells, but RasGEFB/M/U are not. These findings illustrate a specific and coordinated control of the cytoskeletal dynamics by multiple RasGEFs for spontaneous motility and macropinocytosis.
真核生物趋化性的可兴奋系统能够自发产生富含Ras - GTP结构域的不对称信号，以驱动细胞在没有引导线索的情况下随机迁移。然而，负责自发信号产生的分子仍然难以捉摸。在这里，我们通过对Ras - GTP的时空动态进行活细胞成像和层次聚类，对盘基网柄菌中编码的Ras鸟苷酸交换因子（RasGEFs）进行了表征，发现RasGEFX主要是自发产生富含Ras - GTP结构域所必需的，并且在饥饿细胞中与RasGEFB/M/U结合时对于随机迁移至关重要，而它们对于向趋化因子环磷酸腺苷（cAMP）的趋化作用是可有可无的。与Ras - GTP共定位的RasGEFX和RasGEFB分别调节沿膜传播的振荡Ras - GTP波的时间周期和空间大小，从而以不同方式控制运动细胞的突起，而RasGEFU和RasGEFM分别调节黏附力和迁移速度。值得注意的是，RasGEFX对于增殖细胞中Ras/磷脂酰肌醇 - 3,4,5 - 三磷酸（PIP3）驱动的巨胞饮作用也很重要，但RasGEFB/M/U则不然。这些发现说明了多种RasGEFs对细胞骨架动力学进行特定且协调的控制，以实现自发运动和巨胞饮作用。
