DOWN-REGULATION OF PHOSPHOLIPASE C-GAMMA-1 DURING THE DIFFERENTIATIONOF U937 CELLS

Phospholipase C (PLC)-gamma 1 and -gamma 2 play a pivotal role in sign al transduction for cell proliferation and differentiation. The enzyme activity and protein level of PLC-gamma 1 were markedly decreased in the human histiocytic leukemia U937 cell line during the differentiati on process,which is induced by phorbol 12-myristate 13-acetate (PMA) b ut those of PLC-gamma 2 were not altered. Northern blot analysis showe d that the levels of PLC-gamma 1 and -gamma 2 transcripts were not cha nged. These results suggest that the expression of PLC-gamma 1 during the PMA-induced differentiation may be down-regulated by post-transcri ptional processing.