title: Immature CD4+CD8+ thymocytes do not polarize lipid rafts in response to TCR-mediated signals.
abstract: TCR-mediated stimulation induces activation and proliferation of mature T cells. When accompanied by signals through the costimulatory receptor CD28, TCR signals also result in the recruitment of cholesterol- and glycosphingolipid-rich membrane microdomains (lipid rafts), which are known to contain several molecules important for T cell signaling. Interestingly, immature CD4(+)CD8(+) thymocytes respond to TCR/CD28 costimulation not by proliferating, but by dying. In this study, we report that, although CD4(+)CD8(+) thymocytes polarize their actin cytoskeleton, they fail to recruit lipid rafts to the site of TCR/CD28 costimulation. We show that coupling of lipid raft mobilization to cytoskeletal reorganization can be mediated by phosphoinositide 3-kinase, and discuss the relevance of these findings to the interpretation of TCR signals by immature vs mature T cells.
authors.affiliation: Department of Biology, Haverford College, Haverford, PA 19041, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Ebert
authors.forename: J F
authors.initials: JF
authors.lastname: Baker
authors.forename: J A
authors.initials: JA
authors.lastname: Punt
mesh_terms: D000199:Actins / Q000502:physiology; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation / Q000276:immunology; D016764:Cell Polarity / Q000187:drug effects / Q000276:immunology; D002867:Chromones / Q000494:pharmacology; D003599:Cytoskeleton / Q000276:immunology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D021962:Membrane Microdomains / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*
chemical_list: D000199:Actins; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011948:Receptors, Antigen, T-Cell; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one