Immunohistochemical and molecular analysis of β1 and β3 integrins

The expression and function of integrin subunits was examined by immunohistochemical staining of normal and malignant tissues and by producing specific changes in avian β subunit cDNA that were subsequently expressed in mammalian cells. Most tissues express only a restricted number of integrins. These include primarily those thought to function as collagen/laminin receptors. With the exception of metastatic melanomas, tumors show a general down regulation of integrins. Structure/function studies of the β subunit show that the cytoplasmic domain is required for inclusion in adhesion plaques and for promotion of adhesive functions; that the transmembrane domain is required for subunit association, but not proper α subunit selection; and that the amino terminal one third of the subunit must remain intact for subunit selection and ligand binding to occur.