Laminin-1 and laminin-2 G-domain synthetic peptides bind syndecan-1 and are involved in acinar formation of a human submandibular gland cell line

The culture of human submandibular gland (HSG) cells on laminin-l induces acinar differentiation. me identified a site on laminin involved in acinar differentiation using synthetic peptides derived from the C-terminal G-domain of the laminin alpha 1 and alpha 2 chains. The alpha 1 chain peptide AG73 (RKRLQVQLSIRT) decreases the size of acini formed on laminin-1, Cells cultured with either AG73 or the homologous alpha 2 chain peptide MG73 (KNRLTIELEVRT) form structures that appear acinar-like, but the cell nuclei are not polarized to the basal surface and no lumen formation occurs, indicating that additional sites on laminin are required for complete differentiation. The G-domain of laminin-l contains both integrin and heparin binding sites, and anti-beta(1)-integrin antibodies disrupt acinar formation. Cell adhesion to the peptides and to E3, an elastase digest fragment of laminin-1 containing AG73, is specific, since other laminin peptides or EDTA do not compete the binding. Heparin and heparan sulfate decrease cell adhesion to AG73 and MG73 but anti-beta(1)-integrin antibodies have no effect. Treating the cell surface with heparitinase inhibits adhesion to both AG73 and MG73, We isolated cell surface ligands using both peptide affinity chromatography and laminin-l affinity chromatography, Treating the material bound to the affinity columns with heparitinase and chondroitinase enriches for a core protein identified as syndecan-1 by Western blot analysis, thus identifying a syndecan-1 binding site in the globular domain of laminin-2 and laminin-2, In summary, multiple interactions between laminin and HSG cells contribute to acinar differentiation, involving both beta(1)-integrins and syndecan-1.