title: Identification of a novel Stat3 recruitment and activation motif within the granulocyte colony-stimulating factor receptor.
abstract: Stat3 is essential for early embryonic development and for myeloid differentiation induced by the cytokines granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6). Two isoforms of Stat3 have been identified, (p92) and beta (p83), which have distinct transcriptional and biological functions. Activation of both Stat3 and Stat3beta requires the distal cytoplasmic domain of the G-CSFR, which contains four Tyr at positions 704, 729, 744, and 764. The studies reported here were undertaken to determine which, if any, of these tyrosine residues participated in Stat3/beta recruitment and activation. We showed that Stat3 and Stat3beta were affinity purified using phosphopeptides containing Y704 and Y744 but not by nonphosphorylated peptide analogues or by phosphopeptides containing Y729 and Y764. Complementary results were obtained in studies examining the ability of these peptides to destabilize and inhibit DNA binding of activated Stat3. Both Y704 and Y744 contributed to optimal activation of Stat3/beta in M1 murine myeloid leukemia cells containing wild-type and Y-to-F mutant G-CSFR constructs. Carboxy-terminal to Y704 at the +3 position is Gln; YXXQ represents a consensus Stat3 recruitment and activation motif. Y744 is followed at the +3 position by Cys (C); YXXC, represents a novel motif implicated in the recruitment and activation of Stat3. Modeling of the SH2 domain of Stat3 based on homologous SH2 domains of known structure revealed polar residues whose side chains contact the +3 position. This substitution may confer specificity for the Y704- and Y744-based ligands by allowing H-bond formation between the binding surface and the Gln or Cys found at the respective +3 position.
authors.affiliation: Division of Infectious Diseases, the Department of Medicine, University of Pittsburgh School of Medicine and the University of Pittsburgh Cancer Institute, 200 Lothrop St, Pittsburgh,
authors.forename: A
authors.initials: A
authors.lastname: Chakraborty
authors.forename: K F
authors.initials: KF
authors.lastname: Dyer
authors.forename: M
authors.initials: M
authors.lastname: Cascio
authors.forename: T A
authors.initials: TA
authors.lastname: Mietzner
authors.forename: D J
authors.initials: DJ
authors.lastname: Tweardy
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001667:Binding, Competitive / Q000235:genetics; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D016179:Granulocyte Colony-Stimulating Factor / Q000502:physiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D010748:Phosphopeptides / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D010748:Phosphopeptides; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D016179:Granulocyte Colony-Stimulating Factor; D014443:Tyrosine