The Effect of Receptor Protein Tyrosine Phosphatase Kappa on the Change of Cell Adhesion and Proliferation Induced by N-Acetylglucosaminyltransferase V

N-acelylglucosaminyltransferase V (GnT-V) has been reported to be positively associated with tumor progression, but its mechanism still remains unknown. In the present study, We found that GnT-V overexpression not only changed the glycosylation of receptor protein tyrosine phosphatase kappa (RPTP kappa) but also decreased its protein level. Moreover, GnT-V overexpression decreased cell calcium-independent adhesion and increased the tyrosine phosphorylation level of P-catenin, in which RPTP kappa played an important role. Since RPTP kappa has an RXKR motif, which is a favored cleavage site for furin, we used furin inhibitor to further explore the effect or RPTP kappa on the change of cell adhesion beta-catenin signaling induced by GnT-V. Our results showed that preventing RPTP kappa cleavage rescued the above effects of GnT-V, suggesting that furin cleavage could be one of the factors for RPTP kappa to regulate cell adhesion and beta-catenin signaling in GnT-V overexpression cell lines. In addition, the increased tyrosine phosphorylation level of beta-catenin was associated with the increased nuclear level of beta-catenin and downstream signaling molecules such as c-myc and cyclin D1 that were associated with cell proliferation. Our results suggest that GnT-V could decrease human hepatoma SMMC-7721 cell adhesion and promote cell proliferation partially through RPTP kappa. J. Cell. Biochem. 109: 113-123, 2010. (C) 2009 Wiley-Liss, Inc.