Change in the accessibility of an epitope of the human granulocyte-colony stimulating factor after binding to receptors

The granulocyte colony stimulating factor (G-CSF) activates Jak/STAT and MAPK pathways in a trophoblastic cell line

Granulocyte colony-stimulating factor receptor (G-CSFR) has been found in placenta tissues, although its functional role has not yet been defined. In order to explore the molecular pathways induced by G-CSF in this tissue, we first reveal the presence of G-CSFR in the JEG-3 human trophoblastic cell line and then examined the phosphorylation of Janus tyrosine kinases (Jak), signal transducers and activators of transcription (STAT) proteins and mitogen-activated protein kinases (MAPK) after G-CSF binding to receptors. We showed that Jak1, Jak2, Tyk2, and STAT3 were phosphorylated after incubation with G-CSF. Phosphorylation of p38 and p44/42 MAPK was also activated by G-CSF, and specifically blocked in the presence of the corresponding inhibitors. Similar intracellular pathways were induced by G-CSF in a myeloid leukemia NFS-60 cell line that was studied in parallel. Conversely to cytokine action in myeloid cells, G-CSF did not induce a proliferative response in JEG-3 cells. When the effect of G-CSF on cellular viability was evaluated, cytokine-stimulated JEG-3 cells were protected from foetal serum starvation. In addition, when JEG-3 cells deprived of serum were incubated at different times in the presence of G-CSF, a progressive decrease in the percentage of hypodiploid cells was observed. In summary, we identified the molecular pathways activated after G-CSF binding to trophoblastic cell receptors and showed that G-CSF behaved as a protective cytokine, which supports JEG-3 cells survival.

Interactions of dextran sulfates with granulocyte colony-stimulating factor and their effects on leukemia cells

The interactions between granulocyte colony-stimulating factor (G-CSF) and dextran sulfate (DS) with different chain lengths and sulfate contents were studied by capillary zone electrophoresis. It was found that DS with a molecular mass of 500 kDa (DS500) could bind to G-CSF and the binding constant and binding sites were determined using Scatchard plot to be 1.17 x 10(6) M(-1) and 3, respectively. DS with a molecular mass of 40 kDa also had the affinity to G-CSF and the binding constant and binding sites were 1.01 x 10(6) M(-1) and 8, respectively. However, DS with a molecular mass of 8 kDa and the non-sulfated saccharide, dextran, had no affinity to G-CSF. The results indicate that the interactions between G-CSF and DS are dependent on the chain lengths and sulfate contents of the saccharides. In addition, the effects of G-CSF-binding DS on a G-CSF-dependent leukemia cell line were investigated using biological methods. Results show that DS500 plus G-CSF has potential therapeutic effect on cancers because their combination could inhibit the growth and induce the differentiation of the leukemia cells.

Separation, identification, and interaction of heparin oligosaccharides with granulocyte-colony stimulating factor using capillary electrophoresis and mass spectrometry

A capillary electrophoresis (CE) method was developed for the separation of heparin oligosaccharides compatible to study the interactions between the oligosaccharides and granulocyte-colony stimulating factor (G-CSF). Unfractionated heparin was eliminitively degraded to heparin oligosaccharides by an endolytic heparinase. The degraded smaller oligosaccharides (M(r) < 1000) were baseline-separated by CE under a 50 mM phosphate buffer (pH 9.0) in 10 min. Standard heparin disaccharides and larger oligosaccharides (1000 < M(r) < 8000) were all separated under optimized separation conditions. Compared with standard heparin disaccharides, smaller oligosaccharides contained one nonsulfated, two monosulfated, and two disulfated disaccharides, but trisulfated disaccharides were not found. The smaller oligosaccharides were also identified and molecular mass was deduced by electrospray ionization-mass spectrometry (ESI-MS). Furthermore, interactions between G-CSF and the oligosaccharides were studied by using capillary zone electrophoresis (CZE) under the above separation conditions. It was found that larger oligosaccharides could interact with G-CSF while smaller oligosaccharides were not observed to bind to G-CSF under the experimental conditions. In conclusion, the purified heparinase could selectively degrade heparin into oligosaccharides and the interaction between G-CSF and heparin was correlated with the chain length of heparin.