title: Suppressor of cytokine signaling 6 (SOCS6) negatively regulates Flt3 signal transduction through direct binding to phosphorylated tyrosines 591 and 919 of Flt3.
abstract: The receptor tyrosine kinase Flt3 is an important growth factor receptor in hematopoiesis, and gain-of-function mutations of the receptor contribute to the transformation of acute myeloid leukemia. SOCS6 (suppressor of cytokine signaling 6) is a member of the SOCS family of E3 ubiquitin ligases that can regulate receptor tyrosine kinase signal transduction. In this study, we analyzed the role of SOCS6 in Flt3 signal transduction. The results show that ligand stimulation of Flt3 can induce association of SOCS6 and Flt3 and tyrosine phosphorylation of SOCS6. Phosphopeptide fishing indicated that SOCS6 binds directly to phosphotyrosines 591 and 919 of Flt3. By using stably transfected Ba/F3 cells with Flt3 and/or SOCS6, we show that the presence of SOCS6 can enhance ubiquitination of Flt3, as well as internalization and degradation of the receptor. The presence of SOCS6 also induces weaker activation of Erk1/2, but not Akt, in transfected Ba/F3 and UT-7 cells and in OCI-AML-5 cells. The absence of SOCS6 promotes Ba/F3 and UT-7 cell proliferation induced by oncogenic internal tandem duplications of Flt3. Taken together, these results suggest that SOCS6 negatively regulates Flt3 activation, the downstream Erk signaling pathway, and cell proliferation.
authors.affiliation: Experimental Clinical Chemistry, Department of Laboratory Medicine, Lund University, Wallenberg Laboratory, Skåne University Hospital, 20502 Malmö, Sweden.
authors.forename: Julhash U
authors.initials: JU
authors.lastname: Kazi
authors.forename: Jianmin
authors.initials: J
authors.lastname: Sun
authors.forename: Bengt
authors.initials: B
authors.lastname: Phung
authors.forename: Fahad
authors.initials: F
authors.lastname: Zadjali
authors.forename: Amilcar
authors.initials: A
authors.lastname: Flores-Morales
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnstrand
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding; D059748:Proteolysis; D015398:Signal Transduction / Q000502:physiology*; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000378:metabolism*
chemical_list: C473085:SOCS6 protein, human; D050826:Suppressor of Cytokine Signaling Proteins; D014443:Tyrosine; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D048049:Extracellular Signal-Regulated MAP Kinases