Down-regulation of platelet endothelial cell adhesion molecule-1 results in thrombospondin-1 expression and concerted regulation of endothelial cell phenotype.
bEND.3 cells are polyoma middle T-transformed mouse brain endothelial cells that express very little or no thrombospondin-1, a natural inhibitor of angiogenesis, but express high levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) that localizes to sites of cell-cell contact. Here, we have examined the role of PECAM-1 in regulation of bEND.3 cell proliferation, migration, morphogenesis, and hemangioma formation. We show that down-regulating PECAM-1 expression by antisense transfection of bEND. 3 cells has a dramatic effect on their morphology, proliferation, and morphogenesis on Matrigel. There is an optimal level for PECAM-1 expression such that high levels of PECAM-1 inhibit, whereas moderate levels of PECAM-1 stimulate, endothelial cell morphogenesis. The down-regulation of PECAM-1 in bEND.3 cells resulted in reexpression of endogenous thrombospondin-1 and its antiangiogenic receptor CD36. The expression of the vascular endothelial growth factor receptors flk-1 and flt-1, as well as integrins and metalloproteinases (which are involved in angiogenesis), were also affected. These observations are consistent with the changes observed in proliferation, migration, and adhesion characteristics of the antisense-transfected bEND.3 cells as well as with their lack of ability to form hemangiomas in mice. Thus, a reciprocal relationship exists between thrombospondin-1 and PECAM-1 expression, such that these two molecules appear to be constituents of a "switch" that regulates in concert many components of the angiogenic and differentiated phenotypes of endothelial cells.
Sheibani
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Washington University School of Medicine, Department of Biochemistry and Molecular Biophysics, St. Louis, Missouri 63110, USA.
Frazier
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WA
D000818:Animals; D001921:Brain / Q000378:metabolism; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism; D015197:Carcinogenicity Tests; D002448:Cell Adhesion; D002450:Cell Communication; D002478:Cells, Cultured; D015536:Down-Regulation; D004727:Endothelium / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D018919:Neovascularization, Physiologic / Q000502:physiology; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D018955:CD36 Antigens; D016376:Oligonucleotides, Antisense; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D019700:Thrombospondin 1