Original Contribution

Basic Research in Cardiology

, 109:404

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

  • Yosif ManavskiAffiliated withInstitute of Cardiovascular Regeneration, Goethe University Frankfurt
  • , Guillaume CarmonaAffiliated withInstitute of Cardiovascular Regeneration, Goethe University FrankfurtDavid H Koch Institute for Integrative Cancer Research at Massachusetts Institute of Technology
  • , Katrin BennewitzAffiliated withDepartment of Vascular Biology and Tumor Angiogenesis, Center for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty Mannheim, Heidelberg University
  • , Zhongshu TangAffiliated withState Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University
  • , Fan ZhangAffiliated withNEI, National Institutes of Health
  • , Atsuko SakuraiAffiliated withOral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health
  • , Andreas M. ZeiherAffiliated withDepartment of Internal Medicine III, Cardiology, Goethe University of Frankfurt
  • , J. Silvio GutkindAffiliated withOral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health
  • , Xuri LiAffiliated withState Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University
    • , Jens KrollAffiliated withDepartment of Vascular Biology and Tumor Angiogenesis, Center for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty Mannheim, Heidelberg UniversityDivision of Vascular Oncology and Metastasis, German Cancer Research Center (DKFZ-ZMBH Alliance)
    • , Stefanie DimmelerAffiliated withInstitute of Cardiovascular Regeneration, Goethe University Frankfurt
    • , Emmanouil ChavakisAffiliated withDepartment of Internal Medicine III, Cardiology, Goethe University of FrankfurtInstitute of Cardiovascular Regeneration, Goethe University Frankfurt Email author 

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Abstract

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.

Keywords

Angiogenesis Brag2 Endocytosis Integrins Migration