Abstract
Integrin α6β1 is a major adhesion receptor for the basement membrane, specifically binding to laminin-1. To identify the peptide sequences recognized by α6β1, we screened a 15-mer phage display library by panning with α6β1 purified from human placenta. DNA sequencing of 73 randomly picked phage revealed that three clones were dominantly enriched after repeated panning with α6β1. None of the peptide sequences displayed on these phage showed significant homology to laminin-1. A synthetic peptide modeled after the sequence displayed by one of these phage, designated P3, was found to strongly inhibit the binding of laminin-1 to α6β1. This inhibitory effect of the P3 peptide seems to be specific for α6β1, since it did not affect the binding of fibronectin to integrin α5β1. A synthetic peptide with a scrambled P3 amino acid sequence barely inhibited the binding of laminin-1 to α6β1. When coated on a substratum after conjugation with bovine serum albumin, the P3 peptide was capable of promoting cell spreading in an α6β1 -dependent manner, although the peptide with the scrambled sequence showed activity similar to that of a control peptide. These results taken together indicate that the P3 peptide is a novel ligand for integrin α6β1 with potent cell spreading activity.
