title: Identification of canonical tyrosine-dependent and non-canonical tyrosine-independent STAT3 activation sites in the intracellular domain of the interleukin 23 receptor.
abstract: Signaling of interleukin 23 (IL-23) via the IL-23 receptor (IL-23R) and the shared IL-12 receptor β1 (IL-12Rβ1) controls innate and adaptive immune responses and is involved in the differentiation and expansion of IL-17-producing CD4(+) T helper (TH17) cells. Activation of signal transducer and activator of transcription 3 (STAT3) appears to be the major signaling pathway of IL-23, and STAT binding sites were predicted in the IL-23R but not in the IL-12Rβ1 chain. Using site-directed mutagenesis and deletion variants of the murine and human IL-23R, we showed that the predicted STAT binding sites (pYXXQ; including Tyr-504 and Tyr-626 in murine IL-23R and Tyr-484 and Tyr-611 in human IL-23R) mediated STAT3 activation. Furthermore, we identified two uncommon STAT3 binding/activation sites within the murine IL-23R. First, the murine IL-23R carried the Y(542)PNFQ sequence, which acts as an unusual Src homology 2 (SH2) domain-binding protein activation site of STAT3. Second, we identified a non-canonical, phosphotyrosine-independent STAT3 activation motif within the IL-23R. A third predicted site, Tyr-416 in murine and Tyr-397 in human IL-23R, is involved in the activation of PI3K/Akt and the MAPK pathway leading to STAT3-independent proliferation of Ba/F3 cells upon stimulation with IL-23. In contrast to IL-6-induced short term STAT3 phosphorylation, cellular activation by IL-23 resulted in a slower but long term STAT3 phosphorylation, indicating that the IL-23R might not be a major target of negative feedback inhibition by suppressor of cytokine signaling (SOCS) proteins. In summary, we characterized IL-23-dependent signal transduction with a focus on STAT3 phosphorylation and identified canonical tyrosine-dependent and non-canonical tyrosine-independent STAT3 activation sites in the IL-23R.
authors.affiliation: Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf 40225, Germany.
authors.forename: Doreen M
authors.initials: DM
authors.lastname: Floss
authors.forename: Simone
authors.initials: S
authors.lastname: Mrotzek
authors.forename: Tobias
authors.initials: T
authors.lastname: Klöcker
authors.forename: Jutta
authors.initials: J
authors.lastname: Schröder
authors.forename: Joachim
authors.initials: J
authors.lastname: Grötzinger
authors.forename: Stefan
authors.initials: S
authors.lastname: Rose-John
authors.forename: Jürgen
authors.initials: J
authors.lastname: Scheller
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D049109:Cell Proliferation; D006224:Cricetinae; D003412:Cricetulus; D006367:HeLa Cells; D006801:Humans; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping / Q000379:methods; D010766:Phosphorylation / Q000502:physiology; D017434:Protein Structure, Tertiary; D018123:Receptors, Interleukin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D058504:Th17 Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*
chemical_list: C515500:IL23R protein, human; D018123:Receptors, Interleukin; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse
keywords: Cytokine; Interleukin; MAP Kinases (MAPKs); STAT Transcription Factor; Signal Transduction