Association of cell surface mucins with galectin-3 contributes to the ocular surface epithelial barrier.
Maintenance of an intact mucosal barrier is critical to preventing damage to and infection of wet-surfaced epithelia. The mechanism of defense has been the subject of much investigation, and there is evidence now implicating O-glycosylated mucins on the epithelial cell surface. Here we investigate a new role for the carbohydrate-binding protein galectin-3 in stabilizing mucosal barriers through its interaction with mucins on the apical glycocalyx. Using the surface of the eye as a model system, we found that galectin-3 colocalized with two distinct membrane-associated mucins, MUC1 and MUC16, on the apical surface of epithelial cells and that both mucins bound to galectin-3 affinity columns in a galactose-dependent manner. Abrogation of the mucin-galectin interaction in four different mucosal epithelial cell types using competitive carbohydrate inhibitors of galectin binding, beta-lactose and modified citrus pectin, resulted in decreased levels of galectin-3 on the cell surface with concomitant loss of barrier function, as indicated by increased permeability to rose bengal diagnostic dye. Similarly, down-regulation of mucin O-glycosylation using a stable tetracycline-inducible RNA interfering system to knockdown c1galt1 (T-synthase), a critical galactosyltransferase required for the synthesis of core 1 O-glycans, resulted in decreased cell surface O-glycosylation, reduced cell surface galectin-3, and increased epithelial permeability. Taken together, these results suggest that galectin-3 plays a key role in maintaining mucosal barrier function through carbohydrate-dependent interactions with cell surface mucins.
Argüeso
Pablo
P
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA. pablo.argueso@schepens.harvard.edu
Guzman-Aranguez
Ana
A
Mantelli
Flavio
F
Cao
Zhiyi
Z
Ricciuto
Jessica
J
Panjwani
Noorjahan
N
D019921:Biotinylation; D015153:Blotting, Western; D018394:CA-125 Antigen / Q000378:metabolism*; D002460:Cell Line; D016764:Cell Polarity; D002846:Chromatography, Affinity; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005123:Eye / Q000166:cytology* / Q000378:metabolism*; D005700:Galactosyltransferases / Q000235:genetics / Q000502:physiology; D037502:Galectin 3 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000378:metabolism*; D018396:Mucin-1 / Q000378:metabolism*; D009077:Mucins; D009092:Mucous Membrane / Q000378:metabolism; D011485:Protein Binding; D015531:Radioimmunoprecipitation Assay
D018394:CA-125 Antigen; D037502:Galectin 3; C451759:MUC16 protein, human; D008565:Membrane Proteins; D018396:Mucin-1; D009077:Mucins; C505293:C1GALT1 protein, human; D005700:Galactosyltransferases