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 indu ces acinar differentiation. me identified a site on laminin involved i n acinar differentiation using synthetic peptides derived from the C-t erminal 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 acina r-like, but the cell nuclei are not polarized to the basal surface and no lumen formation occurs, indicating that additional sites on lamini n are required for complete differentiation. The G-domain of laminin-l contains both integrin and heparin binding sites, and anti-beta(1)-in tegrin antibodies disrupt acinar formation. Cell adhesion to the pepti des and to E3, an elastase digest fragment of laminin-1 containing AG7 3, is specific, since other laminin peptides or EDTA do not compete th e 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 ch romatography and laminin-l affinity chromatography, Treating the mater ial 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 d omain of laminin-2 and laminin-2, In summary, multiple interactions be tween laminin and HSG cells contribute to acinar differentiation, invo lving both beta(1)-integrins and syndecan-1.