Migrating endothelial cells are distinctly hyperglycosylated and express specific migration-associated cell surface glycoproteins.

Abstract

Migration of endothelial cells is one of the first cellular responses in the cascade of events that leads to re-endothelialization of an injured vessel and neovascularization of growing tissues and tumors. To examine the hypothesis that endothelial cells express a specific migration-associated phenotype, we analyzed the cell surface glycoprotein expression of migrating bovine aortic endothelial cell (BAECs). Light microscopic analysis revealed an upregulation of binding sites for the lectins Concanavalin A (Con A), wheat germ agglutinin (WGA), and peanut agglutinin after neuraminidase treatment (N-PNA) on migrating endothelial cells relative to contact-inhibited cells. These findings were confirmed and quantitated with an enzyme-linked lectin assay (ELLA) of circularly scraped BAEC monolayers. The expression of migration-associated cell surface glycoproteins was also analyzed by SDS-PAGE. The overall expression of cell surface glycoproteins was upregulated on migrating BAECs. Migrating BAECs expressed Con A- and WGA-binding glycoproteins with apparent molecular masses of 25 and 48 kD that were not expressed by contact-inhibited BAEC monolayers and, accordingly, disappeared as circularly scraped monolayers reached confluence. Subconfluent BAEC monolayers expressed the same cell surface glycoconjugate pattern as migrating endothelial cells. FACS analysis of circularly scraped BAEC monolayers showed that the phenotypic changes of cell surface glycoprotein expression after release from growth arrest occurred before the recruitment of the cells into the cell cycle (3 vs. 12 h). Suramin, which inhibits endothelial cell migration, abrogated the expression of the migration-associated phenotype and induced the expression of a prominent 28-kD Con A- and WGA-binding cell surface glycoprotein. These results indicate that endothelial cells express a specific migration-associated phenotype, which is characterized by the upregulation of distinct cellular glycoconjugates and the expression of specific migration-associated cell surface glycoproteins.