The Role of Sialylated Glycans in Human Platelet Endothelial Cell Adhesion Molecule 1 (PECAM-1)-mediated Trans Homophilic Interactions and Endothelial Cell Barrier Function

Abstract

Edited by Gerald HartPlatelet Endothelial Cell Adhesion Molecule 1 (PECAM-1) is a major component of the endothelial cell intercellular junction. Previous studies have shown that PECAM-1 homophilic interactions, mediated by amino-terminal immunoglobulin homology domain 1, contribute to maintenance of the vascular permeability barrier and to its re-establishment following inflammatory or thrombotic insult. PECAM-1 glycans account for ϳ30% of its molecular mass, and the newly solved crystal structure of human PECAM-1 immunoglobulin homology domain 1 reveals that a glycan emanating from the asparagine residue at position 25 (Asn-25) is located within the trans homophilic-binding interface, suggesting a role for an Asn-25-associated glycan in PECAM-1 homophilic interactions. In support of this possibility, unbiased molecular docking studies revealed that negatively charged ␣2,3 sialic acid moieties bind tightly to a groove within the PECAM-1 homophilic interface in an orientation that favors the formation of an electrostatic bridge with positively charged Lys-89, mutation of which has been shown previously to disrupt PECAM-1-mediated homophilic binding. To verify the contribution of the Asn-25 glycan to endothelial barrier function, we generated an N25Q mutant form of PECAM-1 that is not glycosylated at this position and examined its ability to contribute to vascular integrity in endothelial celllike REN cells. Confocal microscopy showed that although N25Q PECAM-1 concentrates normally at cell-cell junctions, the ability of this mutant form of PECAM-1 to support re-establishment of a permeability barrier following disruption with thrombin was significantly compromised. Taken together, these data suggest that a sialic acid-containing glycan emanating from Asn-25 reinforces dynamic endothelial cell-cell interactions by stabilizing the PECAM-1 homophilic binding interface.

Dissecting the defects in the neonatal CD8+ T-cell response

“…At 8 and 15 days postinfection, OT‐I CD8 + T cells were sorted and found to have a significant reduction in Pecam‐1 transcripts . Interestingly, CD31 can colocalize with the TGFβ receptor on the cell surface to enhance the suppressive effects of TGFβ . Given that TGFβ levels are elevated in multiple neonatal infection models, it is interesting to speculate that neonatal CTLs would be exquisitely sensitive to TGFβ/CD31‐mediated suppression .…”

“…87 Interestingly, CD31 can colocalize with the TGF receptor on the cell surface to enhance the suppressive effects of TGF . 88 Given that TGF levels are elevated in multiple neonatal infection models, it is interesting to speculate that neonatal CTLs would be exquisitely sensitive to TGF /CD31-mediated suppression. 21,22 Therefore, in addition to differences in TCR structure and avidity, there are inhibitory molecules that regulate the TCR and regulate effector function.…”

Application of medical adhesive inhibits intimal hyperplasia involving the downregulation of ERK1/2 and eNOS levels

“…PECAM-1 is able to control the activity of platelets, regulate the migration of leukocytes to the vascular intima and maintain the integrity of the vessel wall. If endothelial cells are injured, their function is decreased, leading to adverse consequences (31,32). The results of the present study suggested that PECAM-1 and VCAM-1 may serve important roles in the regulation of endometrial hyperplasia by medical adhesive.…”

Endothelial Dysfunction as a Consequence of Endothelial Glycocalyx Damage: A Role in the Pathogenesis of Preeclampsia

“…However, carbohydrates part in leukocyte transmigration is still not clear. The recent studies show that N-glycosylation of JAM-A is required for the protein's ability to reinforce barrier function [22]; sialic acid-containing glycan of PECAM-1 reinforces dynamic endothelial cell-cell interactions by stabilizing the PECAM-1 homophilic binding interface [52]; glycosylation status of ICAM-2 (hypo-or non-glycosylated variants) significantly affects the function of this protein in cell motility assays [107]; in pro-inflammatory conditions, modification of VE-cadherin glycans is observed [55]. This obviously requires further investigations.…”

“…N-glycans of the junctional adhesion molecule-A (JAM-A) regulate leukocyte adhesion and lymphocyte function-associated antigen-1 (LFA-1) binding [22]. Platelet/endothelial cell adhesion molecule-1 (PECAM-1 or CD31), a membrane highly glycosylated protein (~30% of molecular mass), has N-linked glycans represented by neutral and sialylated glycans [51,52]. E-selectin is heavily glycosylated protein with hybrid/complex type N-linked oligosaccharides [53].…”