Phosphorylation of cytosolic proteins by resting and activated human
neutrophils
PC Andrews and BM Babior
A study was conducted on the phosphorylation of proteins in the neutrophil
cytosol in response to phorbol myristate acetate (PMA) and N-
formyl-methionyl-leucyl-phenylalanine (fMLP). Autoradiography of gel
electrophoretograms prepared from neutrophils incubated with 32Pi in the
presence and absence of the activators showed nine proteins whose state of
phosphorylation was affected by neutrophil activation. 32P was gained by
eight of these proteins and was lost by the ninth. For all but one of these
proteins, the change in the extent of labeling appeared to reach completion
by one to two minutes. It was possible to quantitate the changes in 32P
content of three of the nine proteins. One of these was the 20-kD protein
that lost label when the neutrophils were activated. Quantitation showed
that over half the 32P present in this protein in the resting state was
gone within 0.2 minutes after activation. The other two were proteins
weighing 11 and 69 kD. The phosphorylation characteristics of these two
proteins differed, depending on whether activation had been carried out
with PMA or fMLP. These differences in protein phosphorylation support
other evidence suggesting that PMA and fMLP do not activate neutrophils by
identical biochemical pathways. Differences in phosphorylation between
resting and activated cells were not affected by dibutyryl cyclic guanosine
monophosphate (cGMP), dibutyryl cyclic adenosine monophosphate (cAMP),
theophylline, aspirin, hydrocortisone, or colchicine. The differences were
abolished, however, by 30 mumol/L trifluoperazine. This finding is
consistent with the hypothesis that the calcium/calmodulin system plays a
biochemical role in the activation of neutrophils.
Volume 64,
Issue 4,
pp. 883-890,
10/01/1984
Copyright © 1984 by The American Society of Hematology
