Brag2 differentially regulates β1- and β3-integrin-dependent adhesion in endothelial cells and is involved in developmental and pathological angiogenesis

  • Yosif Manavski
  • Guillaume Carmona
  • Katrin Bennewitz
  • Zhongshu Tang
  • Fan Zhang
  • Atsuko Sakurai
  • Andreas M. Zeiher
  • J. Silvio Gutkind
  • Xuri Li
  • Jens Kroll
  • Stefanie Dimmeler
  • Emmanouil Chavakis
Original Contribution


β1-Integrins are essential for angiogenesis. The mechanisms regulating integrin function in endothelial cells (EC) and their contribution to angiogenesis remain elusive. Brag2 is a guanine nucleotide exchange factor for the small Arf-GTPases Arf5 and Arf6. The role of Brag2 in EC and angiogenesis and the underlying molecular mechanisms remain unclear. siRNA-mediated Brag2-silencing reduced EC angiogenic sprouting and migration. Brag2-siRNA transfection differentially affected α5β1- and αVβ3-integrin function: specifically, Brag2-silencing increased focal/fibrillar adhesions and adhesion on β1-integrin ligands (fibronectin and collagen), while reducing the adhesion on the αVβ3-integrin ligand, vitronectin. Consistent with these results, Brag2-silencing enhanced surface expression of α5β1-integrin, while reducing surface expression of αVβ3-integrin. Mechanistically, Brag2-mediated αVβ3-integrin-recycling and β1-integrin endocytosis and specifically of the active/matrix-bound α5β1-integrin present in fibrillar/focal adhesions (FA), suggesting that Brag2 contributes to the disassembly of FA via β1-integrin endocytosis. Arf5 and Arf6 are promoting downstream of Brag2 angiogenic sprouting, β1-integrin endocytosis and the regulation of FA. In vivo silencing of the Brag2-orthologues in zebrafish embryos using morpholinos perturbed vascular development. Furthermore, in vivo intravitreal injection of plasmids containing Brag2-shRNA reduced pathological ischemia-induced retinal and choroidal neovascularization. These data reveal that Brag2 is essential for developmental and pathological angiogenesis by promoting EC sprouting through regulation of adhesion by mediating β1-integrin internalization and link for the first time the process of β1-integrin endocytosis with angiogenesis.


Angiogenesis Brag2 Endocytosis Integrins Migration 

Supplementary material

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Supplementary material 1 (PDF 759 kb)
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Yosif Manavski
    • 2
  • Guillaume Carmona
    • 2
    • 7
  • Katrin Bennewitz
    • 3
  • Zhongshu Tang
    • 4
  • Fan Zhang
    • 5
  • Atsuko Sakurai
    • 6
  • Andreas M. Zeiher
    • 1
  • J. Silvio Gutkind
    • 6
  • Xuri Li
    • 4
  • Jens Kroll
    • 3
    • 8
  • Stefanie Dimmeler
    • 2
  • Emmanouil Chavakis
    • 1
    • 2
  1. 1.Department of Internal Medicine III, CardiologyGoethe University of FrankfurtFrankfurtGermany
  2. 2.Institute of Cardiovascular Regeneration, Goethe University FrankfurtFrankfurtGermany
  3. 3.Department of Vascular Biology and Tumor Angiogenesis, Center for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty MannheimHeidelberg UniversityMannheimGermany
  4. 4.State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic CenterSun Yat-Sen UniversityGuangzhouPeople’s Republic of China
  5. 5.NEI, National Institutes of HealthBethesdaUSA
  6. 6.Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of HealthBethesdaUSA
  7. 7.David H Koch Institute for Integrative Cancer Research at Massachusetts Institute of TechnologyCambridgeUSA
  8. 8.Division of Vascular Oncology and MetastasisGerman Cancer Research Center (DKFZ-ZMBH Alliance)HeidelbergGermany

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