Laminin E8 alveolarization site: Heparin sensitivity, cell surface receptors, and role in cell spreading

Cell adhesion to amino acids 2179-2198 (SN-peptide) of the laminin-1 alpha 1-chain is required for lung alveolar formation in vitro (M. L. Matter and G. W. Laurie. J. Cell Biol. 124: 1083-1090, 1994). The nature of the SN-peptide receptor(s) was probed with neutralizing anti-integrin monoclonal antibodies (MAb), cells lacking integrin subunits, soluble heparin, and SN-peptide columns. Cell adhesion and spreading studies confirmed the specificity of SN-peptide and revealed adhesion to be unaffected by inclusion of anti-beta(1)- anti-alpha(2-6)- or anti-alpha(V) beta(5)-integrin MAb. Cells lacking beta(1)- or alpha(6)-integrin subunits were fully adherent. Adhesion was heparin, but not chondroitin sulfate or heparinase, sensitive, much as is alpha-dystroglycan-laminin-1 binding. Heparin eluted similar to 155- and 180-kDa cell-surface proteins from SN-peptide columns. An additional similar to 91-kDa protein was eluted by EDTA. All were unrecognized by anti-beta(1)-integrin MAb. SN-peptide therefore interacts with three cell-surface proteins for which the identity remains to be determined.