Suppressor of cytokine signaling-3 is recruited to the activated granulocyte-colony stimulating factor receptor and modulates its signal transduction.
G-CSF is a polypeptide growth factor used in treatment following chemotherapy. G-CSF regulates granulopoiesis and acts on its target cells by inducing homodimerization of the G-CSFR, thereby activating intracellular signaling cascades. The G-CSFR encompasses four tyrosine motifs on its cytoplasmic tail that have been shown to recruit a number of regulatory proteins. Suppressor of cytokine signaling 3 (SOCS-3), also referred to as cytokine-inducible Src homolgy 2-containing protein 3, is a member of a recently discovered family of feedback inhibitors that have been shown to inhibit the Janus kinase/STAT pathway. In this study, we demonstrate that human SOCS-3 is rapidly induced by G-CSF in polymorphonuclear neutrophils as well as in the myeloid precursor cell line U937 and that SOCS-3 negatively regulates G-CSFR-mediated STAT activation. Most importantly, we show that SOCS-3 is recruited to the G-CSFR in a phosphorylation-dependent manner and we identify phosphotyrosine (pY)729 as the major recruitment site for SOCS-3. Furthermore, we demonstrate that SOCS-3 directly binds to this pY motif. Surface plasmon resonance analysis reveals a dissociation constant (K(D)) for this interaction of around 2.8 microM. These findings strongly suggest that the recruitment of SOCS-3 to pY729 is important for the modulation of G-CSFR-mediated signal transduction by SOCS-3.
Bayer Pharma Research Center, Wuppertal, Germany.
Michael
M
Hörtner
Ulrich
U
Nielsch
Lorenz M
LM
Mayr
James A
JA
Johnston
Peter C
PC
Heinrich
Serge
S
Haan
D002352:Carrier Proteins / Q000502:physiology; D002478:Cells, Cultured; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009000:Monocytes / Q000502:physiology; D009504:Neutrophils / Q000502:physiology; D011506:Proteins / Q000502:physiology*; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000502:physiology*; D012097:Repressor Proteins; D015398:Signal Transduction / Q000502:physiology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D014443:Tyrosine / Q000378:metabolism
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D012097:Repressor Proteins; C108944:SOCS1 protein, human; C106644:SOCS3 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D016179:Granulocyte Colony-Stimulating Factor; D014443:Tyrosine