Background：

The alpha subunit has cell adhesive properties. Can act both as an adhesion and an anti-adhesion protein. May provide a protective layer on epithelial cells against bacterial and enzyme attack.
The beta subunit contains a C-terminal domain which is involved in cell signaling， through phosphorylations and protein-protein interactions. Modulates signaling in ERK， SRC and NF-kappa-B pathways. In activated T-cells， influences directly or indirectly the Ras/MAPK pathway. Promotes tumor progression. Regulates TP53-mediated transcription and determines cell fate in the genotoxic stress response. Binds， together with KLF4， the PE21 promoter element of TP53 and represses TP53 activity.