Cell adhesion via murine alpha 4 human beta 1 integrin chimera on transfected K562 cells to endothelial cells

To evaluate the property of binding activity of alpha 4 beta 1 integrin in cell-cell interaction, we newly established a cell line, alpha 4mK562, by transfecting cDNA of murine integrin alpha 4 subunit into human erythroleukemic K562 cells, alpha 4mK562 transfectant expressed both murine alpha 4 and human beta 1 subunit, which generated a functional heterodimer. alpha 4mK562 cells more efficiently bound to murine endothelial cell lines and recombinant human TNF alpha (rhTNF)-treated human umbilical vein endothelial cells (HUVEC) than the parental K562 cells, These adhesion resulted from the interaction between alpha 4 beta 1 and VCAM-1. Interestingly, treatment with mAb against human beta 1 (4B4 clone), which has been known as inhibitory mAb, enhanced binding of alpha 4mK562 cells to rhTNF-treated HUVEC but not to murine endothelial cells, This increase in binding induced by 4B4 mAb was completely inhibited by another mAb against human beta 1 (mAb13), but only partially by anti-alpha 4 mAb (PS/2), The increase in binding induced by 4B4 mAb was also abolished by metabolic inhibitors, indicating that the increased binding is energy dependent, These observations suggest that the binding of 4B4 mAb to the chimeric alpha 4 beta 1 induces an unique outside-in signaling and enhances the specific binding of alpha 4mK562 cells to rhTNF-treated HUVEC. (C) 1996 Academic Press, Inc.