Abstract
Integrins are a family of cell surface, transmembrane, heterodimeric glycoprotein complexes consisting of an α and a β subunit that act as cell-substrate and cell-cell adhesion receptors. The β1-containing integrins are the major cell adhesion receptors on many cell types for such extracellular matrix and basement membrane components as collagen, laminin, and fibronectin. Intracellular maturation of the asparagine-linked carbohydrates on β1 integrins is unusually slow, involves the addition of are latively large glycan structure, and is required for the acquisition of ligand-binding activity of the α5β1 high affinity fibronectin-binding integrin. Ligand-binding function may be specifically associated with sialylation of the β1 integrin. Activation of keratinocytes, which is accompanied by increased adhesiveness to, and migration on, fibronectin substrates, is also associated with changes in the intracellular glycan processing of integrins. Oncogenic transformation does not necessarily result in changes in the cell surface expression of β1 integrins but does increase the rate of integrin processing, decrease the size of the intracellular pool of immature integrin β1 polypeptides, and alter the cell-surface localization of integrins.
