Molecular Cancer Research, University Medical Center Utrecht, 3582 CG Utrecht, The Netherlands.
Proc Natl Acad Sci U S A. 2013 Jul 9;110(28):11427-32. doi: 10.1073/pnas.1306595110. Epub 2013 Jun 24.
Rap1 is a small GTPase regulating cell-cell adhesion, cell-matrix adhesion, and actin rearrangements, all processes dynamically coordinated during cell spreading and endothelial barrier function. Here, we identify the adaptor protein ras-interacting protein 1 (Rasip1) as a Rap1-effector involved in cell spreading and endothelial barrier function. Using Förster resonance energy transfer, we show that Rasip1 interacts with active Rap1 in a cellular context. Rasip1 mediates Rap1-induced cell spreading through its interaction partner Rho GTPase-activating protein 29 (ArhGAP29), a GTPase activating protein for Rho proteins. Accordingly, the Rap1-Rasip1 complex induces cell spreading by inhibiting Rho signaling. The Rasip1-ArhGAP29 pathway also functions in Rap1-mediated regulation of endothelial junctions, which controls endothelial barrier function. In this process, Rasip1 cooperates with its close relative ras-association and dilute domain-containing protein (Radil) to inhibit Rho-mediated stress fiber formation and induces junctional tightening. These results reveal an effector pathway for Rap1 in the modulation of Rho signaling and actin dynamics, through which Rap1 modulates endothelial barrier function.
Rap1 是一种调节细胞-细胞黏附、细胞-基质黏附以及肌动蛋白重排的小 GTP 酶，所有这些过程在细胞扩展和内皮屏障功能中都被动态协调。在这里，我们确定衔接蛋白 Ras 相互作用蛋白 1（Rasip1）是参与细胞扩展和内皮屏障功能的 Rap1 效应物。我们使用荧光共振能量转移（Förster resonance energy transfer）显示，Rasip1 在细胞环境中与活性 Rap1 相互作用。Rasip1 通过其相互作用伙伴 Rho GTP 酶激活蛋白 29（ArhGAP29）介导 Rap1 诱导的细胞扩展，ArhGAP29 是 Rho 蛋白的 GTP 酶激活蛋白。因此，Rap1-Rasip1 复合物通过抑制 Rho 信号通路诱导细胞扩展。Rasip1-ArhGAP29 途径也在 Rap1 介导的内皮连接调节中发挥作用，从而控制内皮屏障功能。在这个过程中，Rasip1 与其密切相关的 ras-association 和稀释结构域蛋白（Radil）合作，抑制 Rho 介导的应力纤维形成，并诱导连接的收紧。这些结果揭示了 Rap1 在调节 Rho 信号和肌动蛋白动力学中的效应途径，通过该途径 Rap1 调节内皮屏障功能。
