title: Rap1 promotes VEGFR2 activation and angiogenesis by a mechanism involving integrin αvβ₃.
abstract: Vascular endothelial growth factor (VEGF) acting through VEGF receptor 2 (VEGFR2) on endothelial cells (ECs) is a key regulator of angiogenesis, a process essential for wound healing and tumor metastasis. Rap1a and Rap1b, 2 highly homologous small G proteins, are both required for angiogenesis in vivo and for normal EC responses to VEGF. Here we sought to determine the mechanism through which Rap1 promotes VEGF-mediated angiogenesis. Using lineage-restricted Rap1-knockout mice we show that Rap1-deficiency in endothelium leads to defective angiogenesis in vivo, in a dose-dependent manner. Using ECs obtained from Rap1-deficient mice we demonstrate that Rap1b promotes VEGF-VEGFR2 kinase activation and regulates integrin activation. Importantly, the Rap1b-dependent VEGF-VEGFR2 activation is in part mediated via integrin α(v)β(3). Furthermore, in an in vivo model of zebrafish angiogenesis, we demonstrate that Rap1b is essential for the sprouting of intersomitic vessels, a process known to be dependent on VEGF signaling. Using 2 distinct pharmacologic VEGFR2 inhibitors we show that Rap1b and VEGFR2 act additively to control angiogenesis in vivo. We conclude that Rap1b promotes VEGF-mediated angiogenesis by promoting VEGFR2 activation in ECs via integrin α(v)β(3). These results provide a novel insight into the role of Rap1 in VEGF signaling in ECs.
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53201, USA.
authors.forename: Sribalaji
authors.initials: S
authors.lastname: Lakshmikanthan
authors.forename: Magdalena
authors.initials: M
authors.lastname: Sobczak
authors.forename: Changzoon
authors.initials: C
authors.lastname: Chun
authors.forename: Angela
authors.initials: A
authors.lastname: Henschel
authors.forename: Jillian
authors.initials: J
authors.lastname: Dargatz
authors.forename: Ramani
authors.initials: R
authors.lastname: Ramchandran
authors.forename: Magdalena
authors.initials: M
authors.lastname: Chrzanowska-Wodnicka
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D015536:Down-Regulation; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D017353:Gene Deletion; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018919:Neovascularization, Physiologic; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*; D015027:Zebrafish; D020668:rap GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D039302:Integrin alphaVbeta3; D040301:Vascular Endothelial Growth Factor Receptor-2; C492136:Rap1b protein, mouse; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins