EXOGENOUSLY EXPRESSED GRANULOCYTE-COLONY-STIMULATING FACTOR (G-CSF) RECEPTOR ON K562 CELLS CAN TRANSDUCE G-CSF TRIGGERED GROWTH AND DIFFERENTIATION SIGNALS

Human granulocyte colony-stimulating factor (G-CSF) receptor cDNA was introduced into the erythroleukemic cell line K562, which normally doe s not express the receptor, using lipofection transfection of a G-CSF receptor expression plasmid vector, Transfected cells expressed the re ceptor with a dissociation constant of 130 pmol/L, and a maximum of 11 800 binding sites per cell. Culture of G-CSF receptor-expressing cell s (GR-K562) in the presence of G-CSF enhanced DNA synthesis and a stim ulation index of 4.61 was obtained in a H-3-thymidine uptake assay, Fu rthermore, flow cytometric studies revealed induced expression of CD11 b (29% from 7%), and enhanced expression of CD13 (57% from 27%) on GR- K562 cultured in the presence of G-CSF, Our findings indicate that the exogenously expressed G-CSF receptor can deliver signals and function efficiently on these immature cells on which the receptor is not norm ally expressed, which suggests the presence of intact intracellular si gnal transduction pathways that can be used by the ectopically express ed receptor.