Polysialoganglioside GT1b, a keratinocyte membrane glycosphingolipid, inhibits normal keratinocyte adhesion and migration on a fibronectin matrix. The specificity of the inhibition for cells plated on a fibronectin matrix and competition of GT1b inhibition with peptide RGDS suggest that GT1b abrogates the α5β1/fibronectin interaction. We examined the effects of GT1b on the adhesion and migration of keratinocyte-derived cell lines and correlated GT1b responsiveness and α5β1 integrin expression. GT1b (5 nM) significantly inhibited migration of normal human keratinocytes, immortalized keratinocytes, and squamous cell carcinoma SCC12F2 cells on fibronectin, but not on collagen I. Concentrations as high as 5 μM had no effect on SCC13 or HaCaT cells. Likewise, GT1b inhibited fibronectin-dependent cell adhesion of normal human keratinocytes, immortalized keratinocytes, and SCC12F2 cells, but had no effect on SCC13 or HaCaT cells. Flow cytometric and Western immunoblot analysis of integrin expression showed significantly decreased α5 and β1 integrin expression in SCC13 and HaCaT cells compared to normal keratinocytes, immortalized keratinocytes, and SCC12F2 cells. Incubation with TGF-β1 increased α5β1 integrin expression and induced responsiveness to GT1b in HaCaT cells. These data imply that GT1b 'response' requires sufficient expression of α5β1 and further suggest that the mechanism of the inhibitory effect of GT1b involves GT1b/α5β1 interaction.
ASJC Scopus subject areas
- Cell Biology