Molecular Cancer Research, Centre of Biomedical Genetics and Cancer Genomics Centre, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, Netherlands.
Sci Signal. 2012 Feb 21;5(212):pe6. doi: 10.1126/scisignal.2002913.
Plexins are transmembrane receptors for semaphorins that serve as guidance cues for neurite outgrowth. The intracellular region of plexins contains a guanosine triphosphatase (GTPase)-activating protein (GAP) domain for Ras. New evidence shows that the GAP activity is specific for Rap proteins, small GTPases involved in the regulation of processes that are potentially important for axon guidance, including cell adhesion and migration. Semaphorin-induced dimerization stimulates plexin GAP activity, thereby locally inhibiting Rap1 and enabling neurite retraction. This important finding connects semaphorin signaling to Rap-mediated signaling and is another intriguing example of how small GTPases are used for spatial and temporal control of cell behavior.
神经丛蛋白是神经突生长的导向线索——神经递质的跨膜受体。神经丛蛋白的细胞内区域包含一个鸟苷三磷酸酶（GTPase）激活蛋白（GAP）域，用于 Ras。新的证据表明，GAP 活性是 Rap 蛋白的特异性，Rap 是一种小 GTPase，参与调节对轴突导向很重要的过程，包括细胞黏附和迁移。神经递质诱导的二聚化刺激神经丛 GAP 活性，从而局部抑制 Rap1 并使神经突缩回。这一重要发现将神经递质信号与 Rap 介导的信号联系起来，是小 GTPase 如何用于细胞行为的时空控制的另一个有趣例子。
