The Robo4-TRAF7 complex suppresses endothelial hyperpermeability in inflammation

Abstract

Roundabout4 (Robo4) is an endothelial cell-specific receptor that stabilizes the vasculature in pathological angiogenesis. Although Robo4 has been shown to suppress vascular hyperpermeability induced by vascular endothelial growth factor (VEGF) in angiogenesis, the roles of Robo4 in inflammation are poorly understood. In this study, we investigated the roles of Robo4 on vascular hyperpermeability in inflammation. Endotoxemia models using Robo4−/− mice showed increased mortality and vascular leakage. In endothelial cell, Robo4 suppressed tumor necrosis factor α (TNFα)-induced hyperpermeability by stabilizing VE-cadherin at cell junctions. Robo4 deletion assays revealed that Robo4 suppressed hyperpermeability through its C-terminus. Immunoprecipitation of Robo4-binding proteins in endothelial cells followed by mass spectrometry identified TNF receptor associated factor 7 (TRAF7). Coimmunoprecipitation and immunofluorescence staining demonstrated that TRAF7 colocalized with Robo4 by interacting with its C-terminus. Gain- and loss-of-function studies of TRAF7 with or without Robo4 expression showed that Robo4-mediated suppression of hyperpermeability required TRAF7. Together, we demonstrated that the Robo4-TRAF7 complex is a novel negative regulator of inflammatory hyperpermeability. We propose this complex as a novel target for protection against inflammatory diseases.