The vascular barrier that separates blood from tissues is actively regulated by the endothelium and is essential for transport, inflammation, and haemostasis. Haemodynamic shear stress plays a critical role in maintaining endothelial barrier function, but how this occurs remains unknown. Here we use an engineered organotypic model of perfused microvessels to show that activation of the transmembrane receptor NOTCH1 directly regulates vascular barrier function through a non-canonical, transcription-independent signalling mechanism that drives assembly of adherens junctions, and confirm these findings in mouse models. Shear stress triggers DLL4-dependent proteolytic activation of NOTCH1 to expose the transmembrane domain of NOTCH1. This domain mediates establishment of the endothelial barrier; expression of the transmembrane domain of NOTCH1 is sufficient to rescue defects in barrier function induced by knockout of NOTCH1. The transmembrane domain restores barrier function by catalysing the formation of a receptor complex in the plasma membrane consisting of vascular endothelial cadherin, the transmembrane protein tyrosine phosphatase LAR, and the RAC1 guanidine-exchange factor TRIO. This complex activates RAC1 to drive assembly of adherens junctions and establish barrier function. Canonical transcriptional signalling via Notch is highly conserved in metazoans and is required for many processes in vascular development, including arterial–venous differentiation, angiogenesis and remodelling. We establish the existence of a non-canonical cortical NOTCH1 signalling pathway that regulates vascular barrier function, and thus provide a mechanism by which a single receptor might link transcriptional programs with adhesive and cytoskeletal remodelling.

中文翻译：

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一种非规范的 Notch 复合物调节粘附连接和血管屏障功能

将血液与组织分开的血管屏障由内皮主动调节，对运输、炎症和止血至关重要。血液动力学剪切应力在维持内皮屏障功能方面起着关键作用，但这种情况如何发生仍然未知。在这里，我们使用灌注微血管的工程器官模型来显示跨膜受体 NOTCH1 的激活通过非规范的、转录独立的信号传导机制直接调节血管屏障功能，该机制驱动粘附连接的组装，并在小鼠模型中证实了这些发现。剪切应力触发 NOTCH1 的 DLL4 依赖性蛋白水解激活，以暴露 NOTCH1 的跨膜结构域。该域介导内皮屏障的建立；NOTCH1 跨膜结构域的表达足以挽救由 NOTCH1 敲除引起的屏障功能缺陷。跨膜结构域通过催化质膜中受体复合物的形成来恢复屏障功能，该复合物由血管内皮钙粘蛋白、跨膜蛋白酪氨酸磷酸酶 LAR 和 RAC1 胍交换因子 TRIO 组成。这种复合物激活 RAC1 以驱动粘附连接的组装并建立屏障功能。通过 Notch 的经典转录信号在后生动物中高度保守，并且是许多血管发育过程所必需的，包括动静脉分化、血管生成和重塑。我们确定了调节血管屏障功能的非经典皮质 NOTCH1 信号通路的存在，