Journal
MOLECULAR AND CELLULAR BIOLOGY
Volume 26, Issue 8, Pages 3181-3193Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.26.8.3181-3193.2006
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- NCI NIH HHS [R01 CA046120, R37 CA046120] Funding Source: Medline
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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 beta 1,6GlcNAc-branched N-glycans, products of Golgi beta 1,6-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 phosphatidlylinositol 3-kinase (PI3K), recruits conformationally active alpha 5 beta 1-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 gallectin-3 N-terminal oligomerization domain stimulate alpha 5 beta 1 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 alpha 5 beta 1 translocation to fibrillar adhesions.
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