N-Glycosylation of β4 Integrin Controls the Adhesion and Motility of Keratinocytes

alpha 6 beta 4 integrin is an essential component of hemidesmosomes and modulates cell migration in wound healing and cancer invasion. To elucidate the role of N-glycosylation on beta 4 integrin, we investigated keratinocyte adhesion and migration through the re-expression of wild-type or N-glycosylation-defective beta 4 integrin (Delta N beta 4) in beta 4 integrin null keratinocytes. N-glycosylation of beta 4 integrin was not essential for the heterodimer formation of beta 4 integrin with alpha 6 integrin and its expression on a cell surface, but N-glycosylation was required for integrin-mediated cell adhesion and migration. Concomitantly with the reduction of beta 4 integrin in the membrane microdomain, the intracellular signals of Akt and ERK activation were decreased in cells expressing DN beta 4 integrin. Forced cross-linking of beta 4 integrin rescued the decreased ERK activation in Delta N beta 4 integrin-expressing cells to a similar extent in wild-type beta 4 integrin-expressing cells. Surprisingly, compared with cells expressing wild-type beta 4 integrin, an alternation in N-glycan structures expressed on epidermal growth factor receptor (EGFR), and the induction of a stronger association between EGFR and beta 4 integrin were observed in Delta N beta 4 integrin-expressing cells. These results clearly demonstrated that N-glycosylation on beta 4 integrin plays an essential role in keratinocyte cellular function by allowing the appropriate complex formation on cell surfaces.