Localization of ahe alpha 6 and beta 4 integrin subunits in normal human non-lymphoid tissues

The alpha 6/beta 4 integrin, of undefined receptor activity, has been shown to be expressed in a variety of murine epithelial cells. To gain information on the role of this heterodimer in tissue architecture as well as in malignant transformation we have performed an extensive immunohistochemical analysis of normal human tissues using monoclonal antibodies to alpha 6 and beta 4 subunits. Because alpha 6 is known to associate also with the beta 1 subunit to form a non-promiscuous receptor for laminin, the expression of beta 1 chain was also evaluated. The results of this study have shown that the alpha 6 chain has a wide distribution in tissues, including small vessels and peripheral nerves. alpha 6 colocalizes with beta 4 and beta 1 in most epithelial cells at the basolateral or basal aspect abutting the basement membrane. In a minority of tissues lacking beta 4, the alpha 6 chain is coexpressed with beta 1. These findings demonstrate that the expression of alpha 6/beta 1 laminin receptor and alpha 6/beta 4 heterodimer is phylogenetically conserved, suggesting that they are likely to play an important role in cellular scaffolding through binding to laminin and to still uncharacterized ligand/s present in basement membranes.