title: Essential role of Rap signal in pre-TCR-mediated beta-selection checkpoint in alphabeta T-cell development.
abstract: We demonstrate that lck promoter-driven conditional expression of transgenic SPA-1, a Rap GTPase-activation protein, causes a profound defect of alphabeta T-cell development at the CD4/CD8 double-negative (DN) stage due to enhanced cell death without affecting gammadelta T-cell development. The effect was specific to the DN stage, because CD4 promoter-driven SPA-1 expression hardly affected T-cell development. Rap1A17, a dominant-negative Rap mutant, interfered with the generation of double-positive (DP) cells from Rag2(-/-) fetal thymocytes in vitro in the presence of anti-CD3epsilon antibody and Notch ligand. Rap GTPases were activated in a DN cell line by the expression of self-oligomerizing CD3 (CD8:CD3epsilon chimera), which substituted autonomous pre-T-cell receptor (TCR) signal, inducing CD69 expression and CD25 down-regulation. Reciprocally, expression of C3G, a Rap guanine nucleotide exchange factor, in both normal and Rag2(-/-) DN cells markedly enhanced Notch-dependent generation and expansion of DP cells without additional anti-CD3epsilon antibody, thus bypassing pre-TCR. Defective alphabeta T-cell development in the conditional SPA-1-transgenic mice was restored completely by introducing a p53(-/-) mutation. These results suggest that endogenous Rap GTPases downstream of pre-TCR play an essential role in rescuing pre-T cells from the p53-mediated checkpoint response, thus allowing Notch-mediated expansion and differentiation.
authors.affiliation: Department of Immunology and Cell Biology, Kyoto University, Kyoto, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Kometani
authors.forename: Masaki
authors.initials: M
authors.lastname: Moriyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nakashima
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Katayama
authors.forename: Shu-Fang
authors.initials: SF
authors.lastname: Wang
authors.forename: Sho
authors.initials: S
authors.lastname: Yamasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hattori
authors.forename: Nagahiro
authors.initials: N
authors.lastname: Minato
mesh_terms: D000818:Animals; D016923:Cell Death / Q000235:genetics / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics* / Q000276:immunology; D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor / Q000502:physiology*; D016158:Genes, p53 / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000378:metabolism; D051880:Receptors, Notch / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D013950:Thymus Gland / Q000276:immunology / Q000378:metabolism; D020668:rap GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D009687:Nuclear Proteins; C499308:Rag2 protein, mouse; D016693:Receptors, Antigen, T-Cell, alpha-beta; D051880:Receptors, Notch; C091108:Sipa1 protein, mouse; D020668:rap GTP-Binding Proteins