title: Sequence motifs in IL-4R alpha mediating cell-cycle progression of primary lymphocytes.
abstract: IL-4 signaling through the IL-4Ralpha chain regulates the development and proliferation of the Th2 lineage of effector CD4(+) T cells. Analyses of the IL-4R in factor-dependent cell lines led to the development of two apparently conflicting models of the primary structural determinants of IL-4R-mediated proliferative signaling. In one model, proliferation was dependent on the first conserved tyrosine in the cytoplasmic tail (Y1), while in the second, proliferation was independent of cytoplasmic tyrosines. We found that in activated primary T cells, mutation of only the Y1 residue resulted in a modest decrease in IL-4-induced S phase entry, a further decrease in cell-cycle completion, and a complete failure of IL-4 to induce p70S6 kinase phosphorylation. Consistent with a role for the PI3K/mammalian target of rapamycin pathway in mediating cytokine acceleration of G(2)/M transit, pretreatment of activated T cells with rapamycin resulted in only a modest decrease in IL-4-induced S phase entry, but a total block of cell-cycle completion. Strikingly, IL-4Ralpha chains that lacked all cytoplasmic tyrosines were competent to signal for STAT5 phosphorylation, mediated efficient S phase entry, and promoted cell-cycle progression. The ability of tyrosine-deficient IL-4Rs to mediate proliferative signaling and STAT phosphorylation was absolutely dependent on the presence of an intact ID-1 region. These findings show that IL-4Ralpha lacking cytoplasmic tyrosine residues is competent to induce ID-1-dependent proliferation, and indicate that IL-4 can promote G(2)/M progression via activation of the mammalian target of rapamycin pathway initiated at the Y1 residue.
authors.affiliation: Department of Microbiology and Immunology, Vanderbilt University Medical School, Nashville, TN 37232-3463, USA.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Stephenson
authors.forename: Do-Sim
authors.initials: DS
authors.lastname: Park
authors.forename: Ana L
authors.initials: AL
authors.lastname: Mora
authors.forename: Shreevrat
authors.initials: S
authors.lastname: Goenka
authors.forename: Mark
authors.initials: M
authors.lastname: Boothby
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D016193:G1 Phase / Q000502:physiology; D016195:G2 Phase / Q000502:physiology; D016131:Lymphocyte Subsets / Q000737:chemistry* / Q000166:cytology* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011494:Protein Kinases / Q000502:physiology; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016196:S Phase / Q000502:physiology; D050799:STAT5 Transcription Factor / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D053662:Interleukin-4 Receptor alpha Subunit
chemical_list: D011494:Protein Kinases; D011956:Receptors, Cell Surface; D050799:STAT5 Transcription Factor; D058570:TOR Serine-Threonine Kinases; D014443:Tyrosine; C504002:Il4ra protein, mouse; D053662:Interleukin-4 Receptor alpha Subunit; C546843:mTOR protein, mouse