Characterization of human vascular endothelial cadherin glycans

Abstract

The glycosylation pattern of human vascular endothelial cadherin (VE-cadherin), purified from cultured human umbilical cord vein endothelial cells, was analyzed. VE-cadherin was metabolically radiolabeled with D-[6-3 H]glucosamine, isolated by immunoprecipitation, purified by SDS-PAGE and in-gel digested with endoproteinase Asp N. Oligosaccharides were sequentially released from resulting glycopeptides and analyzed by chromatographic profiling. The results revealed that VE-cadherin carries predominantly sialylated diantennary and hybrid-type glycans in addition to some triantennary and high mannose-type species. Highly branched, tetraantennary oligosaccharides were found in trace amounts only. Immunohistochemical labeling of VE-cadherin and sialic acids displayed a codistribution along the intercellular junctions in endothelial cells of human umbilical arteries, veins, and cultured endothelial monolayers. Ca 2+ -depletion, performed on cultured endothelial cells, resulted in a reversible complete disappearance of VE-cadherin and of almost all sialic acid staining from the junctions. Sialidase treatment of whole cells caused a change of VE-cadherin immunofluorescence from a continuous and netlike superstructural organization to a scattered inconsistent one. Hence, cell surface sialic acids might play a role in VE-cadherin organization.

Dynamics between actin and the VE-cadherin/catenin complex

“…23 The extracellular domain is highly glycosylated carrying large amounts of terminal sialic acids that might also contribute to adhesion features of the extracellular domain. 24 The extracellular (EC1-EC5) domain also binds regulatory molecules in cis as shown for the vascular endothelial (VE) phosphotyrosine phosphatase (VE-PTP) 25 that, in turn, is associated with the vascular endothelial growth factor receptor 2, VEGFR2. 26 The close association of VE-cadherin via its extracellular domain with other membrane receptors might cause functional clusters that are critical for local signal transduction.…”

VE-Cadherin

“…N-linked glycosylation of VE-cadherin has been demonstrated. 24 Some biophysical parameters of the homophilic VE-cadherin interaction have been determined by atomic force microscopy using a VE-cadherin-Fc fusion protein. 25 Trans association of VE-cadherin dimers was shown to be a low affinity reaction with a K D of 10 Ϫ3 to 10 Ϫ5 mol/L.…”

NEU1 and NEU3 Sialidase Activity Expressed in Human Lung Microvascular Endothelia

“…Increased ␣2,6-sialylation of the EC surface increases endothelial adhesiveness for CD22-bearing B cells (11,12) and lymphocyte function-associated antigen-1 expressing T cells (13). Vascular endothelial (VE)-cadherin is enriched to intercellular boundaries where it regulates EC-EC homophilic adhesion and paracellular pathway function (14). VE-cadherin is sialylated, and its desialylation results in its profound reorganization.…”

“…Other sialylated molecules at the EC surface regulate components of both the clotting (15,16) and complement (17) pathways. The sialylation state of these EC surface molecules influences their tertiary conformation, intermolecular interactions, resistance to proteolysis, and function (1,9,10,(12)(13)(14).…”