Stimulation of Stat5 by granulocyte colony-stimulating factor (G-CSF) is modulated by two distinct cytoplasmic regions of the G-CSF receptor.
In a manner similar to many other cytokines, treatment of cells with granulocyte CSF (G-CSF) has been shown to induce the tyrosine phosphorylation of the STAT proteins. Activation of Stat1 and Stat5 by G-CSF requires the membrane-proximal cytoplasmic domain of the receptor, including box1 and box2, while G-CSF-stimulated tyrosine phosphorylation of Stat3 also requires a region distal to box 2. In this study, we show that although the membrane-proximal 55 amino acids of the G-CSF receptor are sufficient for activation of Stat5, the maximal rate of Stat5 activation requires an additional 30 amino acids of the cytoplasmic domain. In contrast, the distal carboxyl-terminal region of the receptor appears to down-regulate Stat5 activation in that deletion of this carboxyl terminus results in increased amplitude and prolonged duration of Stat5 activation by G-CSF. Significantly, expression of a truncated dominant-negative Stat5 protein in hemopoietic cells not only inhibits G-CSF-dependent cell proliferation, but also suppresses cell survival upon G-CSF withdrawal. We further show that a potential protein tyrosine phosphatase may play a critical role in the down-regulation of G-CSF-stimulated Stat5 activation. These results demonstrate that two distinct cytoplasmic regions of the G-CSF receptor are involved in the regulation of the intensity and duration of Stat5 activation, and that Stat5 may be an important player in G-CSF-mediated cell proliferation and survival.
Dong
F
F
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Liu
X
X
de Koning
J P
JP
Touw
I P
IP
Hennighausen
L
L
Larner
A
A
Grimley
P M
PM
D000818:Animals; D019556:COS Cells; D002455:Cell Division; D002470:Cell Survival; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D016179:Granulocyte Colony-Stimulating Factor / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D051379:Mice; D008894:Milk Proteins; D017434:Protein Structure, Tertiary; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D008894:Milk Proteins; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D016179:Granulocyte Colony-Stimulating Factor