A Key Regulator of Cell Adhesion: Identification and Characterization of Important -Glycosylation Sites on Integrin α5 for Cell Migration

The -glycosylation of integrin α5β1 is thought to control many fundamental aspects of cell behavior, including cell adhesion and migration. However, the mechanism of how -glycans function remains largely obscure. Here, we used a loss-of-function approach. Wild-type (WT) integrin α5 and -glycosylation mutant S3-5 (sites 3 to 5) integrin α5, which contains fewer -glycans, were stably reconstituted in α5 knockout cancer cells. We found that the migration ability of S3-5 cells was decreased in comparison with that of the WT. Interestingly, the levels of phosphorylated focal adhesion kinase and actin stress fiber formation were greatly enhanced in the S3-5 mutant. In a mechanistic manner, the internalization of active but not total integrin α5β1 was inhibited in S3-5 cells, which is a process that is related to the enhanced expression of active integrin α5β1 on the cell surface. Importantly, restoration of -glycosylation on the β-propeller domain of α5 reinstated the cell migration ability, active α5β1 expression, and internalization. Moreover, these -glycans are critical for α5-syndecan-4 complex formation. These findings indicate that -glycosylation on the β-propeller domain functions as a molecular switch to control the dynamics of α5β1 on the cell surface that in turn is required for optimum adhesion for cell migration.