RECK-mediated suppression of tumor cell invasion is regulated by glycosylation in human tumor cell lines

RECK, a glycosylphosphatidylinositol (GPI)-anchored glycoprotein, negatively regulates matrix metalloproteinases (MMP), such as MMP-9, and inhibits tumor invasion and metastasis. The predicted amino acid sequence of human RECK includes five putative N-glycosylation sites; however, the precise biochemical role of glycosylated RECK remains unknown. In this study, we examined the link between glycosylation and the function of RECK in human tumor cell lines. RECK protein was glycosylated at Asn⁸⁶, Asn ²⁰⁰, Asn²⁹⁷, and Asn³⁵² residues but not at the Asn³⁹ residue in HT1080 cells. Although the glycosylation of these asparagine sites did not play a role in the cell surface localization of RECK as a GPI-anchored protein, the glycosylation of RECK Asn²⁹⁷ residue was involved in the suppression of MMP-9 secretion and Asn³⁵² residue was necessary to inhibit MMP-2 activation. Moreover, RECK-suppressed tumor cell invasion was reversed by inhibiting glycosylation at Asn⁸⁶, Asn ²⁹⁷, and Asn³⁵² residues of RECK. Thus, these findings indicate that glycosylation mediates RECK suppression of tumor cell invasion by multiple mechanisms such as suppressing MMP-9 secretion and inhibiting MMP-2 activation.