Max Planck Institute for Molecular Biomedicine, Münster, Germany.
Institute for Molecular Cell Biology, University of Münster, Münster, Germany.
EMBO J. 2021 May 3;40(9):e106113. doi: 10.15252/embj.2020106113. Epub 2021 Feb 19.
Leukocyte extravasation is an essential step during the immune response and requires the destabilization of endothelial junctions. We have shown previously that this process depends in vivo on the dephosphorylation of VE-cadherin-Y731. Here, we reveal the underlying mechanism. Leukocyte-induced stimulation of PECAM-1 triggers dissociation of the phosphatase SHP2 which then directly targets VE-cadherin-Y731. The binding site of PECAM-1 for SHP2 is needed for VE-cadherin dephosphorylation and subsequent endocytosis. Importantly, the contribution of PECAM-1 to leukocyte diapedesis in vitro and in vivo was strictly dependent on the presence of Y731 of VE-cadherin. In addition to SHP2, dephosphorylation of Y731 required Ca -signaling, non-muscle myosin II activation, and endothelial cell tension. Since we found that β-catenin/plakoglobin mask VE-cadherin-Y731 and leukocyte docking to endothelial cells exert force on the VE-cadherin-catenin complex, we propose that leukocytes destabilize junctions by PECAM-1-SHP2-triggered dephosphorylation of VE-cadherin-Y731 which becomes accessible by actomyosin-mediated mechanical force exerted on the VE-cadherin-catenin complex.
白细胞渗出是免疫反应的一个必要步骤，需要破坏内皮细胞连接。我们之前已经表明，这个过程在体内依赖于 VE-钙粘蛋白-Y731 的去磷酸化。在这里，我们揭示了潜在的机制。白细胞诱导的 PECAM-1 刺激触发 SHP2 磷酸酶的解离，然后 SHP2 直接靶向 VE-钙粘蛋白-Y731。PECAM-1 与 SHP2 的结合位点对于 VE-钙粘蛋白的去磷酸化和随后的内吞作用是必需的。重要的是，PECAM-1 对体外和体内白细胞渗出的贡献严格依赖于 VE-钙粘蛋白 Y731 的存在。除了 SHP2 之外，Y731 的去磷酸化还需要 Ca2+信号、非肌肉肌球蛋白 II 的激活和内皮细胞张力。由于我们发现β-连环蛋白/斑联蛋白掩盖 VE-钙粘蛋白-Y731，并且白细胞与内皮细胞的对接对 VE-钙粘蛋白-连环蛋白复合物施加力，因此我们提出，白细胞通过 PECAM-1-SHP2 触发的 VE-钙粘蛋白-Y731 去磷酸化来破坏连接，这种去磷酸化可通过肌动球蛋白介导的对 VE-钙粘蛋白-连环蛋白复合物施加的机械力来实现。
