PASSIVE ACQUISITION OF LEUKOCYTE PROTEINS IS ASSOCIATED WITH CHANGES IN PHOSPHORYLATION OF CELLULAR PROTEINS AND CELL-CELL ADHESION PROPERTIES

In this report, we show that interaction of neoplastic epithelial cell s with vesicles derived from leukocytes results in passive acquisition by tumor cells of a diverse group of leukocyte proteins. Vesicles she d from leukocytes were heterogeneous and exhibited the specific protei ns expressed on leukocyte subsets. Accordingly, epithelial cells diffe rentially acquired leukocyte proteins associated with vesicles. Ultras tructural localization demonstrated that acquired proteins were associ ated with the plasma membranes of the epithelial cells. The binding of tumor cells that passively acquired leukocyte proteins to immobilized intercellular adhesion molecule-1 and to endothelial cells was signif icantly increased. Furthermore, passive acquisition of proteins on the plasma membranes of epithelial cells was associated with modulation o f overall phosphorylation of proteins in the range of 20-65 kd and con sisted of both increased as well as decreased phosphorylation of speci fic protein species in the cells. These findings demonstrate that leuk ocyte proteins that are shed in association with vesicles passively co at the plasma membranes of target epithelial cells. Passive acquisitio n of proteins by cells modulates the constitutive properties endowed u pon cells by their native plasma membranes and is associated with chan ges in phosphorylation of cell proteins.