title: Changes in signal transduction downstream from the granulocyte-macrophage colony-stimulating factor receptor during differentiation of primary hemopoietic cells.
abstract: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multifunctional cytokine, having different effects on primitive hemopoietic cells and terminally differentiated end-cells of the myeloid lineage. Human primitive hemopoietic cells (CD34+) were obtained from the peripheral blood after mobilization and induced to proliferate and then differentiate with a combination of cytokines in vitro. Cells at different time points were then used to analyze the expression of the GM-CSF receptor and GM-CSF mediated activation of the JAK 2-STAT 5 and MAP kinase pathways. Scatchard analysis as measured by radioligand binding revealed that freshly purified CD34+ cells expressed 36+/-1 high affinity receptors per cell (mean +/- SE, n = 3) and the level of expression was not significantly different after 3 days in culture, but rose five- to tenfold by day 8. The day 0 CD34+ cells were hyporesponsive to GM-CSF, but by 3 days in culture the cells were still morphologically immature but were actively proliferating and exhibited maximal GM-CSF induced JAK 2-STAT 5 and MAP kinase activation at the optimal time point. Further culture of the CD34+ cells resulted in myeloid differentiation associated with prolongation of MAP kinase activation but not JAK 2-STAT 5 activation. These data indicate that the JAK 2-STAT 5 and MAP kinase pathways are independently regulated and that changes in these signaling pathways occur with differentiation.
authors.affiliation: Department of Haematology, University College London Medical School, United Kingdom.
authors.forename: H
authors.initials: H
authors.lastname: Wheadon
authors.forename: P J
authors.initials: PJ
authors.lastname: Roberts
authors.forename: M J
authors.initials: MJ
authors.lastname: Watts
authors.forename: D C
authors.initials: DC
authors.lastname: Linch
mesh_terms: D018952:Antigens, CD34 / Q000032:analysis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2; D008894:Milk Proteins; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D018952:Antigens, CD34; D004268:DNA-Binding Proteins; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D019000:Phosphotyrosine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases