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Calcium-binding myeloid protein (P8,14) is phosphorylated in fMet-Leu-Phe-stimulated neutrophils
1Department of Biochemistry, Lady Davis Carmel Hospital, Haifa, Israel.
Abstract:
In this report, we show that the p14 subunit of calcium-binding myeloid protein complex (p8,14) is phosphorylated in human neutrophils stimulated with either fMet-Leu-Phe, phorbol myristate acetate, or a calcium ionophore. Trifluoperazine, a calmodulin antagonist, caused hyperphosphorylation of p14 in intact resting neutrophils. Preincubation of resting cells with 10-20 nM calyculin A, a potent protein phosphatase inhibitor, also caused enhanced labeling of p14, which was further progressively increased on stimulation with fMLP. Thus, the phosphorylation level of p14 in resting as well as in stimulated neutrophils appears to be controlled by an active protein phosphatase. The phosphorylation of p14 by a chemoattractant and by a phorbol ester is a novel finding supporting the current belief that p8,14 myeloid protein may play an important role in the metabolism of myeloid cells.
Insights
The p14 subunit of myeloid protein is phosphorylated in human neutrophils upon stimulation. Protein phosphatase activity regulates p14 phosphorylation levels in both resting and stimulated cells.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- The p8,14 myeloid protein complex is involved in cellular processes.
- Understanding the regulation of myeloid protein phosphorylation is crucial for cell metabolism insights.
Purpose of the Study:
- To investigate the phosphorylation of the p14 subunit in human neutrophils.
- To identify factors influencing p14 phosphorylation in response to stimuli.
Main Methods:
- Human neutrophils were stimulated with fMet-Leu-Phe, phorbol myristate acetate, and calcium ionophore.
- Calmodulin antagonist (trifluoperazine) and protein phosphatase inhibitor (calyculin A) were used.
- Phosphorylation levels of p14 were assessed through labeling studies.
Main Results:
- p14 subunit phosphorylation was observed in neutrophils stimulated with chemoattractants and phorbol esters.
- Trifluoperazine induced hyperphosphorylation of p14 in resting neutrophils.
- Calyculin A enhanced p14 labeling, with further increases upon fMLP stimulation, indicating phosphatase control.
Conclusions:
- Neutrophil stimulation leads to p14 subunit phosphorylation.
- An active protein phosphatase regulates the phosphorylation state of p14.
- These findings support a significant role for p8,14 myeloid protein in myeloid cell metabolism.