OSTEOPONTIN ADHESION RECEPTORS ON GINGIVAL FIBROBLASTS

Osteopontin (OPN) promotes attachment and spreading of cells in an RGD dependent fashion, suggesting that OPN interacts with integrins on ce ll surfaces. Here in, we show that LM-609, a monoclonal antibody to th e alpha(v) beta(3) integrin (a vitronectin receptor), inhibited OPN-me diated attachment of gingival fibroblasts. To characterize the cell su rface receptors responsible for this interaction, we performed OPN-sep harose affinity chromatography using detergent extracts of S-35-methio nine or I-125-surface labeled gingival fibroblasts. Proteins bound to the OPN-matrix were eluted with EDTA and subjected to SDS-PAGE under r educing conditions. EDTA eluates from both I-125-surface labeled and S -35- methionine labeled extracts demonstrated prominent bands in the 9 0kDa and 50kDa regions, by both autoradiography and fluorography, resp ectively. These studies suggest that OPN is associated with other cell surface molecules in addition to alpha(v) beta(3). Furthermore, these as yet to be characterized proteins, may prove to have a stronger aff inity for OPN than alpha(v) beta(3).