A role of the protein Cbl in FGF-2-induced angiogenesis in murine brain endothelial cells.
The Cbl protein functions both as a multivalent adaptor and a negative regulator of receptor tyrosine kinases (RTKs), the latter by directing polyubiquitination of RTKs. To study the function of Cbl in endothelial cell signalling and angiogenesis, wild-type Cbl and tyrosine kinase binding (TKB) domain mutated Cbl (G306E) were overexpressed in murine immortalised brain endothelial (IBE) cells. Wild-type Cbl cells exhibited enhanced proliferation in low serum compared with the control and G306E Cbl cells. Furthermore, up-regulated phosphorylation of fibroblast growth factor receptor 1 (FGFR-1) and Akt were observed in wild-type Cbl cells upon FGF-2 stimulation. A Cbl TKB domain mutant, G306E, disrupted the phosphorylation of the FGFR-1 but not that of FRS2. In the tubular morphogenesis assay, cells expressing wild-type Cbl initially formed tubular structures. These showed decreased stability and converted into cell aggregates, possibly due to a failure to cease proliferating. Our data support the idea that the wild-type Cbl cells exhibit enhanced proliferation, and thus lose their ability to differentiate appropriately. The present study reveals a role of the Cbl protein in FGF-2 dependent signalling in endothelial cells by its destabilisation of tubular structures.
Holmqvist
Kristina
K
Department of Medical Cell Biology, Husargatan 3, Box 571, S-751 23 Uppsala, Sweden.
Welsh
Michael
M
Lu
Lingge
L
D000818:Animals; D001921:Brain / Q000098:blood supply; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D003470:Culture Media; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology*; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D051379:Mice; D009154:Mutation; D018919:Neovascularization, Physiologic; D010766:Phosphorylation; D050721:Proto-Oncogene Proteins c-cbl / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism; D044967:Serum; D015398:Signal Transduction
D003470:Culture Media; D016222:Fibroblast Growth Factor 2; D050721:Proto-Oncogene Proteins c-cbl; C496349:Fgfr1 protein, mouse; D051496:Receptor, Fibroblast Growth Factor, Type 1; C493849:Cbl protein, mouse