From Division of Vascular Signaling and Cancer (M.G.A., C.B., A.F., W.-J.Y., S.E.H., A.F.) and Division of Vascular Oncology and Metastasis (S.G., H.G.A.), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg, Germany; Division of Vascular Biology and Tumor Angiogenesis (M.G.A., C.B., W.-J.Y., J.W.-L., S.E.H., M.P., H.G.A., A.F.) and Fifth Medical Department (H.-P.H.), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; and BioNTech AG, Mainz, Germany (J.W.-L.).
Circ Res. 2013 Nov 8;113(11):1206-18. doi: 10.1161/CIRCRESAHA.113.301686. Epub 2013 Sep 11.
The formation of novel blood vessels is initiated by vascular endothelial growth factor. Subsequently, DLL4-Notch signaling controls the selection of tip cells, which guide new sprouts, and trailing stalk cells. Notch signaling in stalk cells is induced by DLL4 on the tip cells. Moreover, DLL4 and DLL1 are expressed in the stalk cell plexus to maintain Notch signaling. Notch loss-of-function causes formation of a hyperdense vascular network with disturbed blood flow.
This study was aimed at identifying novel modifiers of Notch signaling that interact with the intracellular domains of DLL1 and DLL4.
Synaptojanin-2 binding protein (SYNJ2BP, also known as ARIP2) interacted with the PDZ binding motif of DLL1 and DLL4, but not with the Notch ligand Jagged-1. SYNJ2BP was preferentially expressed in stalk cells, enhanced DLL1 and DLL4 protein stability, and promoted Notch signaling in endothelial cells. SYNJ2BP induced expression of the Notch target genes HEY1, lunatic fringe (LFNG), and ephrin-B2, reduced phosphorylation of ERK1/2, and decreased expression of the angiogenic factor vascular endothelial growth factor (VEGF)-C. It inhibited the expression of genes enriched in tip cells, such as angiopoietin-2, ESM1, and Apelin, and impaired tip cell formation. SYNJ2BP inhibited endothelial cell migration, proliferation, and VEGF-induced angiogenesis. This could be rescued by blockade of Notch signaling or application of angiopoietin-2. SYNJ2BP-silenced human endothelial cells formed a functional vascular network in immunocompromised mice with significantly increased vascular density.
These data identify SYNJ2BP as a novel inhibitor of tip cell formation, executing its functions predominately by promoting Delta-Notch signaling.
新血管的形成由血管内皮生长因子启动。随后，DLL4-Notch 信号通路控制尖端细胞的选择，从而引导新的芽生和尾随的茎细胞。茎细胞中的 Notch 信号由尖端细胞上的 DLL4 诱导。此外，DLL4 和 DLL1 在茎细胞丛中表达以维持 Notch 信号。Notch 功能丧失会导致血流紊乱的高密度血管网络形成。
本研究旨在鉴定与 DLL1 和 DLL4 细胞内结构域相互作用的 Notch 信号新调节剂。
突触结合蛋白 2 结合蛋白（SYNJ2BP，也称为 ARIP2）与 DLL1 和 DLL4 的 PDZ 结合基序相互作用，但不与 Notch 配体 Jagged-1 相互作用。SYNJ2BP 优先在茎细胞中表达，增强 DLL1 和 DLL4 蛋白稳定性，并促进内皮细胞中的 Notch 信号。SYNJ2BP 诱导 Notch 靶基因 HEY1、lunatic fringe（LFNG）和 ephrin-B2 的表达，降低 ERK1/2 的磷酸化，并减少血管生成因子血管内皮生长因子（VEGF）-C 的表达。它抑制富含尖端细胞的基因的表达，如血管生成素-2、ESM1 和 Apelin，并损害尖端细胞的形成。SYNJ2BP 抑制内皮细胞迁移、增殖和 VEGF 诱导的血管生成。通过 Notch 信号阻断或应用血管生成素-2可以挽救这一点。沉默 SYNJ2BP 的人内皮细胞在免疫缺陷小鼠中形成功能性血管网络，血管密度显著增加。
这些数据将 SYNJ2BP 鉴定为一种新的尖端细胞形成抑制剂，其主要通过促进 Delta-Notch 信号发挥作用。
