Cell Adhesion via Murine α4 Human β1 Integrin Chimera on Transfected K562 Cells to Endothelial Cells

Abstract

To evaluate the property of binding activity of α4β1 integrin in cell–cell interaction, we newly established a cell line, α4mK562, by transfecting cDNA of murine integrin α4 subunit into human erythroleukemic K562 cells. α4mK562 transfectant expressed both murine α4 and human β1 subunit, which generated a functional heterodimer. α4mK562 cells more efficiently bound to murine endothelial cell lines and recombinant human TNFα (rhTNF)-treated human umbilical vein endothelial cells (HUVEC) than the parental K562 cells. These adhesion resulted from the interaction between α4β1 and VCAM-1. Interestingly, treatment with mAb against human β1 (4B4 clone), which has been known as inhibitory mAb, enhanced binding of α4mK562 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 β1 (mAb13), but only partially by anti-α4 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 α4β1 induces an unique outside-in signaling and enhances the specific binding of α4mK562 cells to rhTNF-treated HUVEC.