Conformational remodeling of the fibronectin matrix selectively regulates VEGF signaling

Abstract

The fibronectin matrix plays a crucial role in the regulation of angiogenesis during development, tissue repair and pathogenesis. Previous work has identified a fibronectin-derived homophilic binding peptide, anastellin, as an effective inhibitor of angiogenesis; however, its mechanism of action is not well understood. In the present study, we demonstrate that anastellin selectively inhibits microvessel cell signaling in response to the VEGF 165 isoform, but not VEGF 121 , by preventing the assembly of the complex containing the VEGF receptor and neuropilin-1. Anastellin treatment resulted in the inactivation of a5b1 integrins but was not accompanied by a change in either adhesion complexes or adhesion-based signaling. Integrin inactivation was associated with a masking of the fibronectin synergy site within the extracellular matrix (ECM), indicating that a5b1 inactivation resulted from a decrease in available ligand. These data demonstrate that anastellin influences the microvessel cell response to growth factors by controlling the repertoire of ligated integrins and point to anastellin as an effective regulator of fibronectin matrix organization. These studies further suggest that homophilic fibronectin binding peptides might have novel applications in the field of tissue regeneration as tools to regulate neovascularization.

Extracellular matrix stiffness modulates VEGF calcium signaling in endothelial cells: individual cell and population analysis

“…The mechanism of action of VEGF has been linked to the state of the extracellular matrix in a number of studies. Prior studies have assessed the ability of VEGF to interact with a variety of different ECM proteins including fibronectin 18, 19, 39 . Binding of VEGF to the matrix can extend downstream MAPK activation 22, 23 .…”

Cooperative effects of fibronectin matrix assembly and initial cell–substrate adhesion strength in cellular self-assembly

“…Once assembled, highly elastic ECM fibronectin fibrils can be further remodeled in response to cell and tissue-derived forces [23, 25, 26]. Compressive, tensile and/or shear stresses exerted on polymerized fibronectin fibrils may subsequently alter the spacing and/or availability of cell and protein binding sites within fibronectin fibrils [27], giving rise to a dynamic range of structurally and functionally distinct forms of ECM fibronectin. How different structural or conformational forms of fibrillar fibronectin influence cell and tissue function is only beginning to be understood.…”

Extracellular Matrix Stiffness Controls VEGF Signaling and Processing in Endothelial Cells

“…Both αvβ3 and α5β1 have distinct roles in angiogenesis in both normal and pathologic conditions (Wijelath et al, ; Ambesi and McKeown‐Longo, ). Blocking αvβ3 activity decreased angiogenesis, but completely knocking it out results in an abundance of endothelial cell sheets and embryonic lethality (Olsson et al, ; Ramjaun and Hodivala‐Dilke, ).…”

“…Both integrin heterodimers can complex with VEGFR2, but β1 integrin only does so in the presence of VEGF (Wijelath et al, , ). These receptors are also capable of complexing with neuropilin‐1 (NRP‐1, a VEGFR co‐receptor) and syndecans (cell associated heparan sulfate proteoglycans (HSPGs)), leading to alterations in cell matrix binding and migration (Eliceiri, ; Olsson et al, ; Sarrazin et al, ; Ambesi and McKeown‐Longo, ). As stiffness changes, it is likely integrin interactions will be altered which could influence endothelial function.…”