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Granulocyte-macrophage colony-stimulating factor enhances cationic antimicrobial protein synthesis by human
Y Waksman1, D W Golde, N Savion
1Department of Histology and Cell Biology, Tel Aviv University, Sackler Faculty of Medicine, Ramat-Aviv, Israel.
Abstract:
We analyzed the effect of recombinant human granulocyte macrophage CSF (GM-CSF) on protein synthesis in peripheral blood polymorphonuclear leukocytes. GM-CSF enhanced PMN 35S-methionine incorporation 1.5-fold over a 2-h incubation period. The effect of GM-CSF on the synthesis of specific proteins was investigated by separating the radiolabeled proteins on SDS-PAGE followed by autoradiography. Stimulation of protein synthesis by GM-CSF was rapid (2 h), dose dependent, and affected at least 10 separate polypeptides. Using ion exchange chromatography some of the GM-CSF-enhanced proteins were identified to have a cationic nature, including the 37- and the 57-kDA proteins whose synthesis was increased by GM-CSF 2.4-fold and 1.6-fold, respectively. The cationic protein fractions from GM-CSF-primed and control cells were eluted from an ion exchange column and tested for their antimicrobial activity. An overall twofold increase in the amount of cationic proteins was recovered from GM-CSF-treated cells as compared to control cells, and these proteins showed a proportional enhanced killing of S. typhimurium. These results suggest that enhanced cationic protein synthesis is an important mechanism whereby GM-CSF can increase neutrophil microbicidal activity via nonoxidative pathways.
Insights
Recombinant human granulocyte macrophage colony-stimulating factor (GM-CSF) boosts protein synthesis in neutrophils, enhancing their antimicrobial cationic proteins and improving bacterial killing through nonoxidative pathways.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Neutrophils play a critical role in host defense against microbial infections.
- Granulocyte macrophage colony-stimulating factor (GM-CSF) is a cytokine known to modulate myeloid cell function.
- The precise mechanisms by which GM-CSF enhances neutrophil antimicrobial activity are under investigation.
Purpose of the Study:
- To investigate the effect of recombinant human GM-CSF on protein synthesis in polymorphonuclear leukocytes (PMNs).
- To identify specific proteins whose synthesis is modulated by GM-CSF.
- To determine if GM-CSF-induced changes in protein synthesis correlate with enhanced antimicrobial activity.
Main Methods:
- Peripheral blood polymorphonuclear leukocytes (PMNs) were incubated with recombinant human GM-CSF.
- Protein synthesis was assessed by measuring 35S-methionine incorporation.
- Radiolabeled proteins were analyzed using SDS-PAGE and autoradiography.
- Cationic proteins were isolated using ion exchange chromatography and tested for antimicrobial activity against S. typhimurium.
Main Results:
- GM-CSF significantly enhanced overall protein synthesis in PMNs by 1.5-fold within 2 hours.
- GM-CSF stimulation rapidly increased the synthesis of at least 10 distinct polypeptides, including 37- and 57-kDa cationic proteins.
- Cationic protein fractions from GM-CSF-treated cells showed a twofold increase and enhanced killing of S. typhimurium compared to controls.
Conclusions:
- Enhanced synthesis of cationic proteins is a key mechanism by which GM-CSF augments neutrophil microbicidal activity.
- GM-CSF-induced protein synthesis contributes to nonoxidative antimicrobial pathways in neutrophils.
- These findings elucidate a novel aspect of GM-CSF's immunomodulatory function in innate immunity.