Aims SCUBE2 (Signal peptide-CUB-epidermal growth factor-like domain-containing protein 2) is a secreted or membrane-bound protein originally identified from endothelial cells (ECs). Our previous work showed that SCUBE2 forms a complex with E-cadherin and stabilizes epithelial adherens junctions (AJs) to promote epithelial phenotypes. However, it remains unclear whether SCUBE2 also interacts with vascular endothelial (VE)-cadherin and modulates EC barrier function. In this study, we investigated whether and how SCUBE2 in ECs regulates vascular barrier maintenance. Methods and results We showed that SCUBE2 colocalized and interacted with VE-cadherin and VE-protein tyrosine phosphatase (VE-PTP) within EC AJs. Furthermore, SCUBE2 knockdown disrupted EC AJs and increased EC permeability. Expression of EC SCUBE2 was suppressed at both mRNA and protein levels via the nuclear factor-κB (NF-κB) signaling pathway in response to pro-inflammatory cytokines or permeability-inducing agents. In line with these findings, EC-specific deletion of Scube2 (EC-KO) in mice impaired baseline barrier function and worsened vascular leakiness of peripheral capillaries after local injection of histamine or vascular endothelial growth factor. EC-KO mice were also sensitive to pulmonary vascular hyperpermeability and leukocyte infiltration in response to acute endotoxin- or influenza virus-induced systemic inflammation. Meanwhile, EC-specific SCUBE2-overexpressing mice were protected from these effects. Molecular studies suggested that SCUBE2 acts as a scaffold molecule enabling VE-PTP to dephosphorylate VE-cadherin, which prevents VE-cadherin internalization and stabilizes EC AJs. As such, loss of SCUBE2 resulted in hyperphosphorylation of VE-cadherin at tyrosine 685, which led to its endocytosis, thus destabilizing EC AJs and reducing barrier function. All of these effects were exacerbated by inflammatory insults. Conclusions We found that SCUBE2 contributes to vascular integrity by recruiting VE-PTP to dephosphorylate VE-cadherin and stabilize AJs, thereby promoting EC barrier function. Moreover, our data suggest that genetic overexpression or pharmacological upregulation of SCUBE2 may help to prevent vascular leakage and edema in inflammatory diseases.

中文翻译：

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SCUBE2 在炎症过程中调节粘附连接动力学和血管屏障功能


目标 SCUBE2（信号肽-CUB-表皮生长因子样结构域蛋白 2）是一种最初从内皮细胞 (EC) 中鉴定出的分泌型或膜结合蛋白。我们之前的工作表明，SCUBE2 与 E-钙粘蛋白形成复合物，并稳定上皮粘附连接 (AJ)，从而促进上皮表型。然而，目前尚不清楚 SCUBE2 是否也与血管内皮 (VE)-钙粘蛋白相互作用并调节 EC 屏障功能。在这项研究中，我们研究了 EC 中的 SCUBE2 是否以及如何调节血管屏障的维持。方法和结果我们发现 SCUBE2 在 EC AJ 内与 VE-钙粘蛋白和 VE-蛋白酪氨酸磷酸酶 (VE-PTP) 共定位并相互作用。此外，SCUBE2 敲低破坏了 EC AJ，并增加了 EC 通透性。 EC SCUBE2 的表达通过核因子-κB (NF-κB) 信号通路在 mRNA 和蛋白质水平上受到促炎细胞因子或通透性诱导剂的抑制。与这些发现一致的是，局部注射组胺或血管内皮生长因子后，小鼠中 EC 特异性删除 Scube2 (EC-KO) 会损害基线屏障功能，并加剧外周毛细血管的血管渗漏。 EC-KO 小鼠还对肺血管通透性过高和白细胞浸润敏感，以响应急性内毒素或流感病毒诱导的全身炎症。同时，EC 特异性 SCUBE2 过表达小鼠免受这些影响。分子研究表明，SCUBE2 作为支架分子，使 VE-PTP 能够使 VE-钙粘蛋白去磷酸化，从而防止 VE-钙粘蛋白内化并稳定 EC AJ。 因此，SCUBE2 的缺失导致 VE-钙粘蛋白在酪氨酸 685 处过度磷酸化，从而导致其内吞作用，从而破坏 EC AJ 的稳定性并降低屏障功能。所有这些影响都因炎症损伤而加剧。结论 我们发现 SCUBE2 通过招募 VE-PTP 使 VE-钙粘蛋白去磷酸化并稳定 AJ，从而促进 EC 屏障功能，从而有助于血管完整性。此外，我们的数据表明，SCUBE2 的基因过度表达或药理学上调可能有助于预防炎症性疾病中的血管渗漏和水肿。