Identification of a 110-kDa nonintegrin cell surface laminin-binding protein which recognizes an A chain neurite-promoting peptide.

Laminin is a potent promoter of neurite outgrowth, and a synthetic peptide of 19 amino acids, PA22-2, from the A chain has been found to promote process formation. Using peptide affinity chromatography, we have identified a 110-kDa, cell surface ligand from both neural cells and brain which binds this sequence. This binding protein does not share immunological identity with the B1 chain of integrin, and reduction does not alter its mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antibody to the 110-kDa protein stained cellular processes in vivo. Sequence analysis of the first 18 amino acids from the amino terminus yielded almost exact sequence identity with nucleolin, a major 110-kDa nucleolar phosphoprotein. Antibody to nucleolin, however, does not interact with the neural-derived, laminin-peptide-binding 110-kDa protein. The 110-kDa protein appears to be a ligand for a specific site on laminin.