N-glycans Regulate Integrin α5β1 Functions

Abstract

Integrin, which is formed by α and β subunits, is cell surface transmembrane glycoprotein that functions as an adhesion receptor. Integrin engagement during cell adhesion leads to intracellular phosphorylation, such as the phosphorylation of the focal adhesion kinase, thereby regulating gene expression, cell growth, differentiation and survival. Integrin is a major carrier of N-glycans. A growing body of evidence indicates that the N-glycosylation of integrin α5β1 plays crucial roles in hetero-dimer formation and in its biological functions (Gu and Taniguchi 2004). In fact, α5β1 integrin contains 26 potential N-linked glycosylation sites, 14 in the α5 subunit and 12 in the β1 subunit. To determine which of the N-glycosylation sites on the α5 subunit are essential for these functions, we sequentially mutated one or combined asparagines (N) residues in the putative N-glycosylation sites to glutamine (Q) residues as shown in Fig. 1, then transfected these mutant genes into α5-deficient Chinese hamster ovary (CHO) cells (CHO-B2) for cell spreading assay (Isaji et al. 2006).