title: Claudin-4 induction by E-protein activity in later stages of CD4/8 double-positive thymocytes to increase positive selection efficiency.
abstract: Claudins (Clds) are crucial constituents of tight-junction strands in epithelial cells and have a central role in barrier functions. We show that Cld4 is unexpectedly expressed in normal thymic lymphocytes independently of tight junctions. The Cld4 expression was mostly confined to a portion of the CD4/CD8 double-positive (DP) cells. The proportion of Cld4(+) DP cells was markedly increased in MHC-I(-/-) II(-/-) mice but decreased in Rorγ(-/-) mice, and Cld4(+) DP cells contained higher levels of the rearranged Tcra transcripts involving the most distal Va and Ja segments than Cld4(-) DP cells. The Cld4 expression levels were reduced in E47-deficient mice in a gene dose-dependent manner, and ChIP analysis indicated that E2A and HEB were bound to the E-box sites of the putative Cldn4 promoter region. Functionally, Cld4 showed a potent T-cell receptor costimulatory activity by coligation with CD3. The Cld4 was distributed diffusely on the cell surface and associated with CD4/lck independently of CD3 in the resting thymocytes. However, Cld4 was strongly recruited to the immunological synapse on specific T-cell receptor engagement through antigen-presenting cells. In the fetal thymic organ culture, knockdown of Cldn4 resulted in the reduced generation of CD4/CD8 single-positive cells from the DP cells. These results suggest that Cld4 is induced by E-protein activity in the later stages of DP cells to increase the efficiency of positive selection, uncovering a hitherto unrecognized function of a Cld family protein.
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hamazaki
authors.forename: Harumi
authors.initials: H
authors.lastname: Fujita
authors.forename: Akikazu
authors.initials: A
authors.lastname: Fujita
authors.forename: Takehito
authors.initials: T
authors.lastname: Sato
authors.forename: Mikio
authors.initials: M
authors.lastname: Furuse
authors.forename: Toyoshi
authors.initials: T
authors.lastname: Fujimoto
authors.forename: Anton M
authors.initials: AM
authors.lastname: Jetten
authors.forename: Yasutoshi
authors.initials: Y
authors.lastname: Agata
authors.forename: Nagahiro
authors.initials: N
authors.lastname: Minato
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000276:immunology*; D016827:CD8 Antigens / Q000276:immunology*; D002448:Cell Adhesion; D062506:Claudin-4; D055785:Gene Knockdown Techniques; D054992:Immunological Synapses; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology*
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D062506:Claudin-4; C568158:Cldn4 protein, mouse; D008565:Membrane Proteins