Potentiated activation of VLA-4 and VLA-5 accelerates proplatelet-like formation
Effect of fibronectin (FN) fragment derived from the carboxyl-terminal heparin-binding (Hep 2) domain on cell adhesion was studied. A 30-kDa Hep 2 fragment showed no significant effect on adhesion of Mardin Darbyn caine kidney (MDCK) cells to FN substrate, whereas after exposure to urea, the Hep 2 fragment suppressed the MDCK cell adhesion to FN in an incompetitive fashion. This anti-cell adhesive Hep 2 fragment preferentially inhibited the RGD (Arg-Gly-Asp)-dependent cell adhesion to FN. No significant binding of the Hep 2 fragment with FN was detected. Additionally, data of flow cytometry showed the presence of specific binding site for the Hep 2 fragment on MDCK cell surface. These results indicate that the Hep 2 domain of FN has a cryptic molecular region having the anti-cell adhesive activity that is probably transduced by a putative cell surface receptor.