title: The TCR C beta FG loop regulates alpha beta T cell development.
abstract: The TCRbeta chain constant domain contains an unusually elongated, solvent-exposed FG loop. This structural element forms one component of an alphabeta TCR cavity against which CD3epsilongamma may abut to facilitate Ag-specific signaling. Consistent with this notion, in the present study we show that N15alphabeta TCR transfectants expressing a FG loop-deleted chain (betaDeltaFG) stimulate less tyrosine protein phosphorylation than those bearing a wild-type beta-chain (betawt) upon TCR cross-linking. Furthermore, coimmunoprecipitation studies suggest a weakened association between the CD3epsilongamma heterodimer and the beta-chain in TCR complexes containing the betaDeltaFG variant. To further investigate the biologic role of the Cbeta FG loop in development, we competitively reconstituted the thymus of Ly5 congenic or RAG-2-/- mice using bone marrow cells from betawt or betaDeltaFG transgenic C57BL/6 (B6) mice. Both betawt and betaDeltaFG precursor cells generate thymocytes representative of all maturational stages. However, betaDeltaFG-expressing thymocytes dominate during subsequent development, resulting in an excess of betaDeltaFG-expressing peripheral T cells with reduced proliferative and cytokine production abilities upon TCR stimulation. Collectively, our results show that the unique Cbeta FG loop appendage primarily controls alphabeta T cell development through selection processes.
authors.affiliation: Laboratory of Immunobiology, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
authors.forename: Maki
authors.initials: M
authors.lastname: Touma
authors.forename: Hsiu-Ching
authors.initials: HC
authors.lastname: Chang
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Sasada
authors.forename: Maris
authors.initials: M
authors.lastname: Handley
authors.forename: Linda K
authors.initials: LK
authors.lastname: Clayton
authors.forename: Ellis L
authors.initials: EL
authors.lastname: Reinherz
mesh_terms: D000818:Animals; D017252:CD3 Complex / Q000737:chemistry / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology*; D049109:Cell Proliferation; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology / Q000378:metabolism
chemical_list: D017252:CD3 Complex; C452842:CD3 antigen, gamma chain; C485468:Cd3e protein, mouse; D016207:Cytokines; D010446:Peptide Fragments; D016693:Receptors, Antigen, T-Cell, alpha-beta