Induced cell surface expression of functional α2β1 integrin during megakaryocytic differentiation of K562 leukemic cells

Abstract The pluripotential hematopoietic cell line K562 was studied as a model of inducible integrin expression accompanying differentiation. Differentiation along the megakaryocytic pathway was induced with phorbol 12,13-dibutyrate and differentiation along the erythroid pathway with hemin. Induction of megakaryocytic differentiation was associated with changes in cell morphology and with increased cell-cell and cell-substrate adhesion and spreading. Erythroid differentiation was not associated with changes in morphology or adhesion. Cell surface expression of the IIb-IIIa and α 2 β 1 integrins increased markedly with phorbol treatment but decreased with hemin treatment. Phorboltreated K562 cells, but not control cells or hemintreated cells, adhered to collagen substrates in a Mg 2+ -dependent manner which was specifically inhibited by a monoclonal antibody directed against the α 2 β 1 integrin. Northern blot analysis revealed that megakaryocytic differentiation of K562 cells was accompanied by de novo expression of the α 2 integrin mRNA with no change in the level of mRNA for the β 1 subunit. K562 cells provide a model of differentiation-dependent, regulated integrin expression in which expression is up- or down-regulated depending upon the differentiation pathway selected.