Functionally distinct roles for glycosylation of alpha and beta integrin chains in cell-matrix interactions.

Abstract

Laminin interaction with gpl20/140, a B16-F10 laminin-binding protein immunologically related to a6p1integrin, has been shown to be dependent on oligosaccharides from both ligand and receptor. Lectin analysis of gpl20/140 led to the conclusion that this integrin is a sialoglycoprotein bearing mainly complex antennary structures. By means of exoglycosidase treatment, it was possible to identify a-galactosyl residues on the integrin a chain as the laminin-binding determinants. These residues are involved in cell adhesion to laminin. On the other hand, (3-chain complex antennary structures, whose synthesis could be inhibited by swainsonine, were associated with cell spreading rather than cell adhesion. Thus, it was possible to modulate integrin-mediated ceOl adhesion and spreading through changes in the glycosylation state of integrin a and ( chains.Cell-matrix interactions are mediated by integrin and nonintegrin receptors (1). Integrins are heterodimeric glycoproteins consisting of two subunits, a and ,B. Combinations of two such polypeptides lead to the formation of different receptors, presenting different ligand specificities. Although the molecular basis of the integrin-ligand interaction is not completely understood, some experimental evidence suggests that posttranslational events are important determining factors (2). In a previous report (3), we characterized the binding of laminin-nidogen complex (LN) to gpl20/140, a LN-binding integrin from B16-F1O melanoma cells, as dependent on asparagine-linked oligosaccharides from both interactants. In the present study, we report on the further characterization of the oligosaccharide chains of affinity-purified gpl20/140 based on its reactivity with a panel of lectins. We have evaluated the functional role of the sugar residues present in the integrin molecule in cell-matrix interactions. A suggestion is made of probable carbohydrate residues involved in adhesion to or spreading of B16-F1O cells on LN surfaces.EXPERIMENTAL PROCEDURES Cell Culture. Murine melanoma cells (B16-F10 line), a gift from M. Hendrix (University of Arizona), were maintained in tissue culture flasks with RPMI 1640 medium (Sigma), supplemented with 10% heat-inactivated fetal calf serum (Cultilab, Campinas, Brazil) [3H]leucine uptake) and displayed no effect on cell viability, as determined by trypan blue exclusion.

Potential of N-glycan in cell adhesion and migration as either a positive or negative regulator

“…[17][18][19] On the other hand, the enzymatic removal of α2, eight-linked oligosialic acids from the α5 integrin subunit inhibited cell adhesion to FN, 20 supporting the observation that the N-glycans of α and β integrin subunits play distinct roles in cell-ECM interactions. 21 Collectively, these findings suggest that the interaction of integrin α5β1 with FN is dependent on N-glycosylation and the processing status of N-glycans.…”

Importance of cell-matrix interactions in rat islet beta-cell secretion in vitro: role of alpha6beta1 integrin.

“…First, it is tempting to speculate that the known alterations of matrix compositions in type 2 diabetes (38) might contribute, at least in part, to the decreased insulin sensitivi t y, due to possible interference with integrin signaling (39) and -cell spreading (40). Second, the characterization of the molecules involved in these interactions might be of help in defining the optimal islet conditioning and appropriate host tissue for improving the success of transplantation to t y p e 1 diabetic patients (41).…”

α2-6–Linked Sialic Acids on N-Glycans Modulate Carcinoma Differentiation In vivo

“…Although integrin-mediated adhesion is primarily based on protein interactions, binding can be significantly modulated by the glycosylation status of the integrin (15,16). Increased Sia6LacNAc on h1-integrins has been reported in several transformed cell types and postulated to alter integrin function by enhancing its activation state and binding to collagen (17,18).…”