title: Brag2 differentially regulates β1- and β3-integrin-dependent adhesion in endothelial cells and is involved in developmental and pathological angiogenesis.
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.
authors: Institute of Cardiovascular Regeneration, Goethe University Frankfurt, Frankfurt, Germany.
authors: Yosif
authors: Y
authors: Manavski
authors: Guillaume
authors: G
authors: Carmona
authors: Katrin
authors: K
authors: Bennewitz
authors: Zhongshu
authors: Z
authors: Tang
authors: Fan
authors: F
authors: Zhang
authors: Atsuko
authors: A
authors: Sakurai
authors: Andreas M
authors: AM
authors: Zeiher
authors: J Silvio
authors: JS
authors: Gutkind
authors: Xuri
authors: X
authors: Li
authors: Jens
authors: J
authors: Kroll
authors: Stefanie
authors: S
authors: Dimmeler
authors: Emmanouil
authors: E
authors: Chavakis
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D019556:COS Cells; D002448:Cell Adhesion / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D002522:Chlorocebus aethiops; D020256:Choroidal Neovascularization / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000235:genetics / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism*; D039661:Integrin beta3 / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D018919:Neovascularization, Physiologic / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics; D019030:Receptors, Vitronectin / Q000235:genetics / Q000378:metabolism; D012178:Retinopathy of Prematurity / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D015027:Zebrafish
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020662:Guanine Nucleotide Exchange Factors; C504483:IQSEC1 protein, human; D039302:Integrin alphaVbeta3; D019012:Integrin beta1; D039661:Integrin beta3; D034741:RNA, Small Interfering; D019030:Receptors, Vitronectin; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C094340:integrin alphavbeta1; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse