INDUCED CELL-SURFACE EXPRESSION OF FUNCTIONAL ALPHA-2-BETA-1-INTEGRIN DURING MEGAKARYOCYTIC DIFFERENTIATION OF K562 LEUKEMIC-CELLS

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 α2β1 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 Mg2+-dependent manner which was specifically inhibited by a monoclonal antibody directed against the α2β1 integrin. Northern blot analysis revealed that megakaryocytic differentiation of K562 cells was accompanied by de novo expression of the α2 integrin mRNA with no change in the level of mRNA for the β1 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. © 1992.