Localization of Lutheran, a novel laminin receptor, in normal, knockout, and transgenic mice suggests an interaction with laminin α5 in vivo

Abstract

Laminins are major components of all basement membranes. One laminin that has garnered particular interest, due to its widespread expression pattern and importance during development, is the laminin α5 chain. In vitro studies have suggested that the Lutheran blood group glycoprotein/basal cell adhesion molecule (Lu), an Ig superfamily transmembrane protein, is a receptor for laminins containing the α5 chain. However, there are no in vivo studies showing that these proteins are capable of interacting in tissues. We have isolated the mouse ortholog of Lu and characterized its expression and localization in mouse tissues. Lu was primarily found on the basal surface of epithelial cells and on muscle cells adjacent to basement membranes containing laminin α5. In addition, there was both a dramatic reduction in the basal concentration of Lu in mice lacking laminin α5, and a significant increase in Lu protein in transgenic mice overexpressing laminin α5. Together, these data provide the first in vivo evidence for an interaction between Lu and laminin α5 and support the hypothesis that Lu is a laminin α5 receptor. We propose that laminin α5 is involved in concentrating Lu on the basal surface of epithelial cells. This may be one mechanism by which basement membrane signals are transmitted to the cell.