Lopez Rioja Alba, Faulkner Ashton, Mellor Harry
School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol, UK.
Vasc Biol. 2022 Feb 28;4(1):K1-K10. doi: 10.1530/VB-21-0012. eCollection 2022 Feb 1.
The endothelial barrier is a tightly regulated gateway in the transport of material between circulation and the tissues. Inflammatory mediators such as thrombin are able to open paracellular spaces in the endothelial monolayer to allow the extravasation of plasma proteins and leukocytes. Here we show that the protein SLIT-ROBO Rho GTPase-activating protein 2 (srGAP2) plays a critical role in regulating the extent of thrombin-mediated opening. We show that srGAP2 is not required for normal barrier function in resting endothelial cells, but that depletion of srGAP2 significantly increases the magnitude and duration of junctional opening in response to thrombin. We show that srGAP2 acts to switch off RhoA signaling after the contraction phase of thrombin-induced permeability, allowing respreading of cells and reformation of the barrier. srGAP2 is also required for effective restoration of the barrier after treatment with two other vasoactive agents that active RhoA - TNFα and angiotensin II. Taken together, we show that srGAP2 has a general function in controlling RhoA signaling in endothelial permeability, acting to limit the degree and duration of opening, by triggering the switch from endothelial cell contraction to respreading.
内皮屏障是循环系统与组织之间物质运输的一个受到严格调控的通道。凝血酶等炎症介质能够在内皮单层细胞中打开细胞旁间隙，使血浆蛋白和白细胞外渗。在此我们表明，蛋白质SLIT-ROBO Rho GTP酶激活蛋白2（srGAP2）在调节凝血酶介导的开放程度中起关键作用。我们发现，srGAP2对于静息内皮细胞的正常屏障功能并非必需，但srGAP2的缺失会显著增加凝血酶诱导的连接开放的幅度和持续时间。我们表明，srGAP2在凝血酶诱导的通透性收缩阶段后发挥作用，关闭RhoA信号，使细胞重新铺展并恢复屏障功能。在用另外两种激活RhoA的血管活性药物——肿瘤坏死因子α（TNFα）和血管紧张素II处理后，有效恢复屏障功能也需要srGAP2。综上所述，我们表明srGAP2在控制内皮通透性中的RhoA信号方面具有一般功能，通过触发从内皮细胞收缩到重新铺展的转变，来限制开放的程度和持续时间。
