Integrin α8β1 promotes attachment, cell spreading, and neurite outgrowth on fibronectin

The integrin α8 subunit, isolated by low stringency hybridization, is a novel integrin subunit that associates with β1. To identify ligands, we have prepared a function-blocking antiserum to the extracellular domain of α8, and we have established by transfection K562 cell lines that stably express α8β1 heterodimers on the cell surface. We demonstrate here by cell adhesion and neurite outgrowth assays that α8β1 is a fibronectin receptor. Studies on fibronectin fragments using RGD peptides as inhibitors show that α8β1 binds to the RGD site of fibronectin. In contrast to the endogenous α5β1 fibronectin receptor in K562 cells, α8β1 not only promotes cell attachment but also extensive cell spreading, suggesting functional differences between the two receptors. In chick embryo fibroblasts, α8β1 is localized to focal adhesions. We conclude that α8β1 is a receptor for fibronectin and can promote attachment, cell spreading, and neurite outgrowth on fibronectin.