EPILIGRIN, A NEW CELL-ADHESION LIGAND FOR INTEGRIN ALPHA-3-BETA-1 IN EPITHELIAL BASEMENT-MEMBRANES

Epiligrin is a new glycoprotein in most epithelial basement membranes (BMs) and is a ligand for cell adhesion via integrin alpha-3-beta-1. In the extracellular matrix of human foreskin keratinocytes (HFKs), epiligrin contains three disulfide-bonded, glycoprotein subunits, E170, E145, and E135, based on molecular size in kilo-daltons. Epiligrin, immunopurified with MAb P1E1, induced cell adhesion and localization of integrin alpha-3-beta-1 in focal adhesions (FAs). Cell adhesion to epiligrin was inhibited with an anti-alpha-3-beta-1 MAb. Epiligrin also colocalized with integrin alpha-6-beta-4 in hemidesmosome-like stable anchoring contacts (SACs). Alpha-3-beta-1-FAs encircled alpha-6-beta-4-SACs in a complex adhesion structure. Alpha-3-beta-1 and epiligrin localized in BM junctions of epithelial cells primarily in organs of endodermal/ectodermal origin. In epidermis, epiligrin was detected in the lamina lucida of BMs. Alpha-3-beta-1 localized in plasma membranes of basal cells in contact with epiligrin and also in lateral/apical membranes. Epiligrin is the ligand of an adhesion super complex composed of alpha-3-beta-1-FAs and alpha-6-beta-4-SACs (hemidesmosomes).