title: GSK3-mediated instability of tubulin polymers is responsible for the failure of immature CD4+CD8+ thymocytes to polarize their MTOC in response to TCR stimulation.
abstract: Although mature T cells divide and differentiate when they receive strong TCR stimulation, most immature CD4+CD8+ thymocytes die. The molecular basis for this marked difference in response is not known. Observations that TCR-stimulated CD4+CD8+ thymocytes fail to polarize their microtubule-organizing center (MTOC), one of the first events that occurs upon antigen activation of mature T cells, suggests that TCR signaling routes in immature and mature T cells diverge early and upstream of MTOC polarization. To better understand the source of the divergence, we examined the molecular basis for the difference in TCR-mediated MTOC polarization. We show that unstable microtubules are a feature of immature murine CD4+CD8+ thymocytes, which also exhibit higher levels of glycogen synthase kinase 3 (GSK3) activity, a known inhibitor of microtubule stability. Importantly, CD4+CD8+ thymocytes gained the ability to polarize their MTOC in response to TCR signals when GSK3 activity was inhibited. GSK3 inhibition also abrogated TCR-mediated apoptosis of immature thymocytes. Together, our results suggest that a developmentally regulated difference in GSK3 activity has a major influence on immature CD4+CD8+ thymocyte versus mature T-cell responses to TCR stimulation.
authors.affiliation: Biology Department, Haverford College, Haverford, PA 19041, USA.
authors.forename: Nicole R
authors.initials: NR
authors.lastname: Cunningham
authors.forename: Emily M
authors.initials: EM
authors.lastname: Hinchcliff
authors.forename: Vassily I
authors.initials: VI
authors.lastname: Kutyavin
authors.forename: Thomas
authors.initials: T
authors.lastname: Beck
authors.forename: Whitney A
authors.initials: WA
authors.lastname: Reid
authors.forename: Jenni A
authors.initials: JA
authors.lastname: Punt
mesh_terms: D000627:Aminophenols / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D015704:CD4 Antigens / Q000276:immunology; D016827:CD8 Antigens / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental / Q000276:immunology; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D022101:Microtubule-Organizing Center / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D058105:Polymerization / Q000187:drug effects; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D060168:Thymocytes / Q000166:cytology / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
chemical_list: C417520:3-(3-chloro-4-hydroxyphenylamino)-4-(4-nitrophenyl)-1H-pyrrole-2,5-dione; D000627:Aminophenols; D015704:CD4 Antigens; D016827:CD8 Antigens; D004791:Enzyme Inhibitors; D008301:Maleimides; D011948:Receptors, Antigen, T-Cell; D014404:Tubulin; D038362:Glycogen Synthase Kinase 3