title: G-CSF receptor truncations found in SCN/AML relieve SOCS3-controlled inhibition of STAT5 but leave suppression of STAT3 intact.
abstract: Truncated granulocyte colony-stimulating factor receptors (G-CSF-Rs) are implicated in severe congenital neutropenia (SCN) and the consecutive development of acute myeloid leukemia (AML). Mice expressing G-CSF-R truncation mutants (gcsfr-d715) show defective receptor internalization, an increased signal transducer and activator of transcription 5 (STAT5)/STAT3 activation ratio, and hyperproliferative responses to G-CSF treatment. We determined whether a lack of negative feedback by suppressor of cytokine signaling (SOCS) proteins contributes to the signaling abnormalities of G-CSF-R-d715. Expression of SOCS3 transcripts in bone marrow cells from G-CSF-treated gcsfr-d715 mice was approximately 60% lower than in wild-type (WT) littermates. SOCS3 efficiently suppressed STAT3 and STAT5 activation by WT G-CSF-R in luciferase reporter assays. In contrast, while SOCS3 still inhibited STAT3 activation by G-CSF-R-d715, STAT5 activation was no longer affected. This was due mainly to loss of the SOCS3 recruitment site Tyr729, with an additional contribution of the internalization defects of G-CSF-R-d715. Because Tyr729 is also a docking site for the Src homology 2-containing protein tyrosine phosphatase-2 (SHP-2), which binds to and inactivates STAT5, we suggest a model in which reduced SOCS3 expression, combined with the loss of recruitment of both SOCS3 and SHP-2 to the activated receptor complex, determine the increased STAT5/STAT3 activation ratio and the resulting signaling abnormalities projected by truncated G-CSF-R mutants.
authors.affiliation: Institute of Hematology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Gert-Jan M
authors.initials: GJ
authors.lastname: van de Geijn
authors.forename: Judith
authors.initials: J
authors.lastname: Gits
authors.forename: Lambertus H J
authors.initials: LH
authors.lastname: Aarts
authors.forename: Claudia
authors.initials: C
authors.lastname: Heijmans-Antonissen
authors.forename: Ivo P
authors.initials: IP
authors.lastname: Touw
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D004195:Disease Models, Animal; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D051379:Mice; D008817:Mice, Mutant Strains; D008894:Milk Proteins; D009503:Neutropenia / Q000235:genetics*; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000235:genetics* / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D017384:Sequence Deletion; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014443:Tyrosine; D018909:src Homology Domains
chemical_list: D004268:DNA-Binding Proteins; D008894:Milk Proteins; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D012097:Repressor Proteins; C106644:SOCS3 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; C491411:Socs3 protein, mouse; C494087:Stat3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014443:Tyrosine