CD93 promotes β1 integrin activation and fibronectin fibrillogenesis during tumor angiogenesis
Roberta Lugano, … , Elisabetta Dejana, Anna Dimberg
Roberta Lugano, … , Elisabetta Dejana, Anna Dimberg
Published May 15, 2018
Citation Information: J Clin Invest. 2018;128(8):3280-3297. https://doi.org/10.1172/JCI97459.
View: Text | PDF
Research Article Oncology Vascular biology

CD93 promotes β1 integrin activation and fibronectin fibrillogenesis during tumor angiogenesis

Abstract

Tumor angiogenesis occurs through regulation of genes that orchestrate endothelial sprouting and vessel maturation, including deposition of a vessel-associated extracellular matrix. CD93 is a transmembrane receptor that is upregulated in tumor vessels in many cancers, including high-grade glioma. Here, we demonstrate that CD93 regulates β1 integrin signaling and organization of fibronectin fibrillogenesis during tumor vascularization. In endothelial cells and mouse retina, CD93 was found to be expressed in endothelial filopodia and to promote filopodia formation. The CD93 localization to endothelial filopodia was stabilized by interaction with multimerin-2 (MMRN2), which inhibited its proteolytic cleavage. The CD93-MMRN2 complex was required for activation of β1 integrin, phosphorylation of focal adhesion kinase (FAK), and fibronectin fibrillogenesis in endothelial cells. Consequently, tumor vessels in gliomas implanted orthotopically in CD93-deficient mice showed diminished activation of β1 integrin and lacked organization of fibronectin into fibrillar structures. These findings demonstrate a key role of CD93 in vascular maturation and organization of the extracellular matrix in tumors, identifying it as a potential target for therapy.

Authors

Roberta Lugano, Kalyani Vemuri, Di Yu, Michael Bergqvist, Anja Smits, Magnus Essand, Staffan Johansson, Elisabetta Dejana, Anna Dimberg

×

Figure 7

CD93 and MMRN2 interact with α5β1 integrin in endothelial cells and regulate its activity.

Options: View larger image (or click on image) Download as PowerPoint
CD93 and MMRN2 interact with α5β1 integrin in endothelial cells and regu...
(A) Immunofluorescent staining of the active β1 integrin (12G10) in control, CD93-silenced (siCD93_1, siCD93_2), and MMRN2-silenced (siMMRN2_3, siMMRN2_6) HDBECs cultured under confluent conditions. Scale bars: 20 μm. (B) Quantification of 12G10 staining in control, siCD93, and siMMRN2 cells. Values represent mean ± SEM expressed as arbitrary units (AU) of 12G10-positive area normalized by cell number (n = 8 different areas of the cell monolayer). *P < 0.05. (C) Colocalization between CD93 and α5β1 integrin and active β1 (12G10) is shown by arrowheads. Different distribution of CD93 and αvβ3 integrin is shown by arrowheads. Scale bars: 20 μm. (D) In situ PLA for CD93 and α5β1 integrin as well as CD93 and active β1 integrin (12G10) in HDBECs. Positive signal (green dots) indicates proximity between CD93 and integrins. F-actin (red) and nuclei (blue). Scale bars: 20 μm. Bars represent the quantification of CD93 and α5β1 integrin or CD93 and active β1 integrin interaction based on the number of positive signals per cell (n = 3 independent experiments). *P < 0.05; **P < 0.01. (E) Y397-phosphorylated FAK staining (p-FAK) in the migrating front of control or siCD93- and siMMRN2-silenced cells at 6 hours after scratch wound. Arrows indicate the direction of migration. Scale bars: 20 μm. (F) Quantification of the p-FAK–positive signal along the migrating front (20 μm distance from the migrating front, indicated by dotted line in E). Bars represent arbitrary units (AU) of p-FAK signal normalized by the number of cells at the migrating edge. *P < 0.05. Values represent mean ± SEM (4 different areas along the migrating edge, 3 independent experiments). 1-Way ANOVA with Dunnett’s post-test was used in all graphs. (G) Schematic representation of CD93 and MMRN2 interacting complex. FB, fibronectin; MMRN2, multimerin-2; sCD93, soluble CD93; Int α5β1, α5β1 integrin; p-FAK, phosphorylated focal adhesion kinase.