DIFFERENTIAL PHOSPHORYLATION IN NORMAL AND LEUKEMIC GRANULOCYTES IN RESPONSE TO PHORBOL 12-MYRISTATE 13-ACETATE

Granulocytes from the peripheral blood of patients with chronic myeloi d leukemia (CML) exhibit a number of functional defects. To explore th e relationship of these aberrations to signal transduction, granulocyt es from normal subjects and CML patients were labelled with (32)Pi, st imulated with phorbol myristate acetate (PMA) and the phosphoproteins (Pps) in the unstimulated and stimulated cells analyzed by 2D-SDS-PAGE followed by autoradiography. Results show that there are six distinct reproducibly phosphorylated proteins referred to as Pp1-Pp6 identifia ble in the basal patterns of the resting granulocytes. Amongst these, Pp1 and Pp5 are more intensely phosphorylated and Pp3 is very faint or absent in unstimulated CML cells, relative to the normal granulocytes . On stimulation of normal cells with PMA, Pp1, Pp3, Pp4 and Pp6 exhib it distinct patterns of phosphon/lation-dephosphorylation. In the CML cells, however, Pp1 and Pp4 are unresponsive to PMA. We conclude that PKC-mediated functions involving Pp1, Pp3 and Pp4 are most probably de fective in CML cells.