Role of ICAM‐1 hypoglycosylation in atherosclerotic plaque formation (1003.1)

Abstract

N‐glycosylation is an ubiquitous post‐translational modification of proteins secreted from cells or expressed on the cell surface. N‐glycan maturation occurs sequentially moving from high mannose to hybrid to complex glycoforms. We recently showed that that during chronic vascular inflammation that underlies atherosclerosis, endothelial cell surface proteins are hypoglycosylated, characterized by increases in high mannose / hybrid glycoforms. Importantly, these epitopes provide ligands for monocyte rolling and adhesion. The protein(s) or adhesion molecule(s) that harbor high mannose epitopes to mediate monocyte rolling and adhesion was determined in this study. Evidence is provided that that a high mannose glycoform of intercellular adhesion molecule‐1 (ICAM‐1), referred to as HM‐ICAM‐1, is produced in activated endothelial cells. HM‐ICAM‐1 formation was also indicated on human atherosclerotic lesions by proximity ligation assay analysis. Moreover, a role for HM‐ICAM‐1 in mediating monocyte rolling and adhesion was demonstrating in cell culture by expressing ICAM‐1 in Cos‐1 cells in the presence of absence of selective inhibitors of N‐glycan processing (kifunensine or swainsonine) which result in high mannose N‐glycan accumulation. Interestingly, at equal surface expression levels, HM‐ICAM‐1 was more effective at binding monocytes than WT (complex glycosylated ICAM‐1). Finally, we present data showing the effects of mutation of all eight individual N‐glycan binding sites on ICAM‐1 and effects on monocyte rolling and adhesion. The assessment of the specific role of each N‐glycan site in ICAM‐1 may lead to future N‐glycan targeted therapies to modulate atherogenic inflammation.Grant Funding Source: Supported in part by by NIH T32 HL007457, Mechanisms of Hypertension and Cardiovascular Disease