Effect of the interaction between fibronectin and VLA-4 on the proliferation of human B cells, especially a novel human B-cell line, OPM-3

Very late antigen (VLA)-4 integrin has been suggested to play an important role in haemopoiesis. However, little is known concerning the roles of the fibronectin (FN)/VLA-4 interaction in the proliferation of human B cells, I n this study we investigated the effect of immobilized FN on the proliferat ion of various B-cell lines, including a newly-established B-cell line, OPM -3, and human tonsillar B cells, that primarily express VLA-4 but not VLA-5 . Immobilized FN significantly promoted the proliferation of OPM-3 cells an d normal B cells via VLA-4. The cross-linking of beta 1 integrins of OPM-3 cells resulted in the phosphorylation of the focal adhesion kinase (FAK) as sociated 90 kD protein, an increase in FAK-associated kinase activity and t he phosphorylation of Raf-l. Furthermore, the MEK1 inhibitor, PD98059, inhi bited the FN-promoted proliferation of OPM-3 cells. These results demonstra te that the FN/VLA-4 interaction transmits the growth signal(s) which may b e mediated by Ras pathway in OPM-3 cells, and suggest that OPM-3 cells may be of great value in studying the roles of the FN/VLA-4 interaction in huma n B-cell growth.