CALCIUM-BINDING MYELOID PROTEIN (P8,14) IS PHOSPHORYLATED IN FMET-LEU-PHE STIMULATED NEUTROPHILS

In this report, we show that the p14 subunit of calcium-binding myeloi d protein complex (p8,14) is phosphorylated in human neutrophils stimu lated with either fMet-Leu-Phe, phorbol myristate acetate, or a calciu m ionophore. Trifluoperazine, a calmodulin antagonist, caused hyperpho sphorylation of pl 4 in intact resting neutrophils. Preincubation of r esting cells with 10-20 nM calyculin A, a potent protein phosphatase i nhibitor, also caused enhanced labeling of p14, which was further prog ressively increased on stimulation with fMLP. Thus, the phosphorylatio n level of p14 in resting as well as in stimulated neutrophils appears to be controlled by an active protein phosphatase. The phosphorylatio n of p14 by a chemoattractant and by a phorbol ester is a novel findin g supporting the current belief that p8,14 myeloid protein may play an important role in the metabolism of myeloid cells.