title: Regulation of the dephosphorylation of Stat6. Participation of Tyr-713 in the interleukin-4 receptor alpha, the tyrosine phosphatase SHP-1, and the proteasome.
abstract: Signal transducer and activator of transcription 6 (Stat6) plays an important role in interleukin (IL)-4-induced responses. To analyze the regulation of Stat6 phosphorylation, cells were cultured in the continuous presence of IL-4 or after a pulse and washout. In the continual presence of IL-4, Stat6 remained phosphorylated for an extended period. After IL-4 removal and inhibition of the Janus family kinase, tyrosine-phosphorylated Stat6 decayed at a rate dependent upon the length of IL-4 stimulation. The decay of tyrosine-phosphorylated Stat6 was similar in the presence or absence of either cycloheximide or actinomycin D. In the absence of functional Src homology-containing phosphatase-1 (SHP-1), the early loss of tyrosine-phosphorylated Stat6 was substantially reduced. Furthermore, the rate of loss of tyrosine-phosphorylated Stat6 in cells expressing a mutation of the human IL-4 receptor alpha in the immunoreceptor tyrosine-based inhibitory motif sequence (Y5F) was dramatically decreased compared with wild-type cells. The early rate of decay was similar in the presence or absence of MG132, an inhibitor of the proteasome, but the later rate of decay was decreased 5-fold. These results suggest that the loss of tyrosine phosphorylation of Stat6 is regulated by the action of SHP-1 and the proteasome but is not dependent on new protein synthesis.
authors.affiliation: Department of Immunology, Holland Laboratory, American Red Cross, Rockville, Maryland 20855, USA.
authors.forename: Erica M
authors.initials: EM
authors.lastname: Hanson
authors.forename: Harold
authors.initials: H
authors.lastname: Dickensheets
authors.forename: Cheng-Kui
authors.initials: CK
authors.lastname: Qu
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Donnelly
authors.forename: Achsah D
authors.initials: AD
authors.lastname: Keegan
mesh_terms: D000818:Animals; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D054645:Protein Phosphatase 1; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D019948:Receptors, Interleukin-4 / Q000737:chemistry / Q000378:metabolism*; D050800:STAT6 Transcription Factor; D015534:Trans-Activators; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009097:Multienzyme Complexes; D019948:Receptors, Interleukin-4; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; C494100:Stat6 protein, mouse; D015534:Trans-Activators; D014443:Tyrosine; D054645:Protein Phosphatase 1; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C509248:Ptpn6 protein, mouse; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex