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Protein-tyrosine phosphorylation regulates apoptosis in human eosinophils and neutrophils
Abstract:
Early signaling events that control the process of programmed cell death are largely unknown. Tyrosine phosphorylation plays a major role in transmembrane signal transduction through most cell surface receptors. Granulocyte/macrophage colony-stimulating factor (GM-CSF), a cytokine released by activated T cells, has been shown to increase tyrosine phosphorylation in several cells and to inhibit granulocyte cell death in vitro. In this study, we demonstrate that the effect of GM-CSF on granulocyte cell death can be blocked by the tyrosine kinase inhibitor genistein, suggesting that increases in tyrosine phosphorylation are essential to inhibit cell death. To analyze the role of tyrosine phosphorylation for the regulation of granulocyte cell death more precisely, we increased levels of tyrosine phosphorylation using the protein-tyrosine phosphatase inhibitor phenylarsine oxide (PAO). Similar to GM-CSF, treatment of the cells with PAO was followed by high increases in tyrosine phosphorylation and inhibition of programmed cell death in human eosinophils and neutrophils. Strikingly, at low concentrations of the inhibitor and low induction of tyrosine phosphorylation, acceleration of apoptosis was observed. Genistein and herbimycin A reversed the effects of PAO on tyrosine phosphorylation and granulocyte apoptosis. These results suggest that programmed eosinophil and neutrophil death is regulated by early events of signal transduction pathways such as tyrosine phosphorylation.
Insights
Granulocyte/macrophage colony-stimulating factor (GM-CSF) inhibits programmed cell death by increasing tyrosine phosphorylation. This study reveals that modulating tyrosine phosphorylation levels precisely controls granulocyte apoptosis, impacting cell survival.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Programmed cell death (apoptosis) regulation involves early signaling events.
- Tyrosine phosphorylation is crucial for transmembrane signal transduction.
- Granulocyte/macrophage colony-stimulating factor (GM-CSF) inhibits granulocyte cell death and increases tyrosine phosphorylation.
Purpose of the Study:
- To investigate the precise role of tyrosine phosphorylation in regulating programmed cell death of granulocytes.
- To determine if increased tyrosine phosphorylation inhibits granulocyte apoptosis.
Main Methods:
- Utilized tyrosine kinase inhibitor genistein to block GM-CSF effects.
- Increased tyrosine phosphorylation using protein-tyrosine phosphatase inhibitor phenylarsine oxide (PAO).
- Observed effects on human eosinophils and neutrophils, assessing apoptosis and tyrosine phosphorylation levels.
Main Results:
- GM-CSF's inhibition of granulocyte cell death was blocked by genistein, confirming the necessity of tyrosine phosphorylation.
- PAO treatment increased tyrosine phosphorylation and inhibited apoptosis in eosinophils and neutrophils, similar to GM-CSF.
- Low concentrations of PAO paradoxically accelerated apoptosis, indicating a dose-dependent effect of tyrosine phosphorylation.
Conclusions:
- Tyrosine phosphorylation is a key regulator of programmed cell death in human eosinophils and neutrophils.
- Early signal transduction events, specifically tyrosine phosphorylation, play a critical role in controlling granulocyte apoptosis.
- The level of tyrosine phosphorylation influences whether granulocyte apoptosis is inhibited or accelerated.