Galectin binding to Mgat5-modified N-glycans regulates fibronectin matrix remodeling in tumor cells.
Oncogenic signaling stimulates the dynamic remodeling of actin microfilaments and substrate adhesions, essential for cell spreading and motility. Transformation is associated with increased expression of beta1,6GlcNAc-branched N-glycans, products of Golgi beta1,6-acetylglucosaminyltransferase V (Mgat5) and the favored ligand for galectins. Herein we report that fibronectin fibrillogenesis and fibronectin-dependent cell spreading are deficient in Mgat5(-/-) mammary epithelial tumor cells and inhibited in Mgat5(+/+) cells by blocking Golgi N-glycan processing with swainsonine or by competitive inhibition of galectin binding. At an optimum dosage, exogenous galectin-3 added to Mgat5(+/+) cells activates focal adhesion kinase (FAK) and phosphatidylinositol 3-kinase (PI3K), recruits conformationally active alpha5beta1-integrin to fibrillar adhesions, and increases F-actin turnover. RGD peptide inhibits PI3K-dependent fibronectin matrix remodeling and fibronectin-dependent cell motility, while galectin-3 stimulates and overrides the inhibitory effects of RGD. Antibodies to the galectin-3 N-terminal oligomerization domain stimulate alpha5beta1 activation and recruitment to fibrillar adhesions in Mgat5(+/+) cells, an effect that is blocked by disrupting galectin-glycan binding. Our results demonstrate that fibronectin polymerization and tumor cell motility are regulated by galectin-3 binding to branched N-glycan ligands that stimulate focal adhesion remodeling, FAK and PI3K activation, local F-actin instability, and alpha5beta1 translocation to fibrillar adhesions.
Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
Annick
A
Lagana
Jacky G
JG
Goetz
Pam
P
Cheung
Avraham
A
Raz
James W
JW
Dennis
Ivan R
IR
Nabi
D000199:Actins / Q000378:metabolism; D000818:Animals; D002277:Carcinoma / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002999:Clone Cells; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D005353:Fibronectins / Q000378:metabolism* / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D037502:Galectin 3 / Q000737:chemistry / Q000378:metabolism; D037161:Galectins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015151:Immunoblotting; D039081:Integrin alpha5beta1 / Q000378:metabolism; D015674:Mammary Neoplasms, Animal / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D017351:N-Acetylglucosaminyltransferases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary
D000199:Actins; D005353:Fibronectins; D037502:Galectin 3; D037161:Galectins; D039081:Integrin alpha5beta1; D011134:Polysaccharides; D017351:N-Acetylglucosaminyltransferases; D019869:Phosphatidylinositol 3-Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases