Expression and dynamic modulation of the human granulocyte colony-stimulating factor receptor in immature and differentiated myeloid cells.
In this study we have examined the expression and modulation of the human granulocyte colony-stimulating factor (G-CSF) receptor (R) in immature and differentiated myeloid cells using a 125I labelled human G-CSF analogue (TG50). Equilibrium binding data revealed a single affinity class of receptor on all cell types expressing G-CSFR (KD 235-606 pM) with neutrophils expressing 2883 +/- 672 Rs/cell. Rapid internalization of surface receptor-bound ligand at 37 degrees C was detected in both immature cells (U937) and neutrophils with > 70% of specifically bound ligand internalized within 5 min. Concentration-response data showed that the level of occupancy of neutrophil G-CSFRs by ligand at 37 degrees C was approximately 5-fold greater than predicted by equilibrium binding data and correlated closely with concentration-response data for biological activity. Re-expression of G-CSFRs following down-regulation by internalization was not detected. Down-regulation of the neutrophil G-CSFR by several agents including granulocyte-macrophage colony-stimulating factor (GM-CSF), tumour necrosis factor (TNF), lipopolysaccharide (LPS), f-met-leu-phe (fMLP), phorbol ester (TPA) and C5a was observed at 37 degrees C but not at 4 degrees C. In contrast, G-CSFRs on immature myeloid cells were significantly down-regulated by TPA only. Differentiation of myeloid leukaemic cell line HL-60 with DMSO, a frequently used model of granulocytic differentiation, was associated with a significant reduction in G-CSFR expression (11 +/- 5% of control) whereas treatment with retinoic acid led to increased G-CSFR expression (161 +/- 3%).
Khwaja
A
A
Department of Haematology, University College London Medical School.
Carver
J
J
Jones
H M
HM
Paterson
D
D
Linch
D C
DC
D001667:Binding, Competitive; D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D009504:Neutrophils / Q000378:metabolism; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology
D016188:Receptors, Granulocyte Colony-Stimulating Factor; D011994:Recombinant Proteins; D016179:Granulocyte Colony-Stimulating Factor