title: Identification of tribbles-1 as a novel binding partner of Foxp3 in regulatory T cells.
abstract: In a previous study, we identified TRIB1, a serine-threonine kinase-like molecule, as a biomarker of chronic antibody-mediated rejection of human kidneys when measured in peripheral blood mononuclear cells. Here, we focused our analysis on a specific subset of peripheral blood mononuclear cells that play a dominant role in regulating immune responses in health and disease, so-called CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs). We isolated both human and murine Treg and non-Treg counterparts and analyzed TRIB1 and Foxp3 mRNA expression by quantitative PCR on the freshly isolated cells or following 24 h of activation. Physical interaction between the human TRIB1 and Foxp3 proteins was analyzed in live cell lines by protein complementation assay using both flow cytometry and microscopy and confirmed in primary freshly isolated human CD4(+)CD25(hi)CD127(-) Tregs by co-immunoprecipitation. Both TRIB1 and Foxp3 were expressed at significantly higher levels in Tregs than in their CD4(+)CD25(-) counterparts (p < 0.001). Moreover, TRIB1 and Foxp3 mRNA levels correlated tightly in Tregs (Spearman r = 1.0; p < 0.001, n = 7), but not in CD4(+)CD25(-) T cells. The protein complementation assay revealed a direct physical interaction between TRIB1 and Foxp3 in live cells. This interaction was impaired upon deletion of the TRIB1 N-terminal but not the C-terminal domain, suggesting an interaction in the nucleus. This direct interaction within the nucleus was confirmed in primary human Tregs by co-immunoprecipitation. These data show a direct relationship between TRIB1 and Foxp3 in terms of their expression and physical interaction and highlight Tribbles-1 as a novel binding partner of Foxp3 in Tregs.
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; TcLand Expression, 21 rue de la Noue Bras de Fer, 44200 Nantes, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Emilie
authors: E
authors: Dugast
authors: Department of Cardiovascular Science, University of Sheffield, Sheffield S10 2TN, United Kingdom.
authors: Endre
authors: E
authors: Kiss-Toth
authors: Department of Cardiovascular Science, University of Sheffield, Sheffield S10 2TN, United Kingdom.
authors: Louise
authors: L
authors: Docherty
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Richard
authors: R
authors: Danger
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Mélanie
authors: M
authors: Chesneau
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Virginie
authors: V
authors: Pichard
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Jean-Paul
authors: JP
authors: Judor
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Ségolène
authors: S
authors: Pettré
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Faculté de Médecine Université de Nantes, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France.
authors: Sophie
authors: S
authors: Conchon
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France; Centre Hospitalier Universitaire de Nantes, Nantes 44000, France.
authors: Jean-Paul
authors: JP
authors: Soulillou
authors: UMR1064, Institut National de la Santé et de la Recherche Médicale, Nantes 44000, France; Institut de Recherche en Transplantation, Institut de Transplantation Urologie-Néphrologie, Nantes 44000, France; Centre Hospitalier Universitaire de Nantes, Nantes 44000, France. Electronic address: sophie.brouard@univ-nantes.fr.
authors: Sophie
authors: S
authors: Brouard
authors: TcLand Expression, 21 rue de la Noue Bras de Fer, 44200 Nantes, France. Electronic address: jashtonchess@tcland-expression.com.
authors: Joanna
authors: J
authors: Ashton-Chess
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002448:Cell Adhesion; D002453:Cell Cycle; D049109:Cell Proliferation; D002470:Cell Survival; D018076:DNA, Complementary / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005816:Genetic Complementation Test; D057809:HEK293 Cells; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D053699:Interleukin-7 Receptor alpha Subunit / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000166:cytology; D051379:Mice; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology; D050378:T-Lymphocytes, Regulatory / Q000166:cytology* / Q000378:metabolism
chemical_list: D015415:Biomarkers; D018076:DNA, Complementary; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D053699:Interleukin-7 Receptor alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; C493170:TRIB1 protein, human; C523598:Trib1 protein, mouse; D017346:Protein Serine-Threonine Kinases