LYSOPHOSPHATIDIC ACID ENHANCES FIBRONECTIN-BINDING TO ADHERENT CELLS

1-Oleoyl lysophosphatidic acid (LPA) enhanced binding of I-125-labeled fibronectin by cultured MG-63 osteosarcoma cells and human fibroblast s in monolayer cultures up to threefold over control levels. For osteo sarcoma cells, LPA was minimally active at 0.1 ng/mL (0.2 nmol/L) and reached maximal activity at 10 ng/mL (20 nmol/L). Increased binding wa s evident within 10 minutes of treatment of cycloheximide-treated cell s with LPA and was due to an increase in the number of fibronectin bin ding sites. LPA also increased the binding of a fragment containing th e 70-kDa amino-terminal region of fibronectin that is primarily respon sible for the reversible binding of fibronectin to matrix assembly sit es on cell surfaces. Removal of LPA resulted in prompt return of fibro nectin binding to baseline levels. These results indicate that LPA is an important enhancer of fibronectin-rich matrix deposition by culture d cells, and it may be the active component in serum and lipoprotein f ractions that is responsible for enhancing fibronectin deposition.