Claudin-4 induction by E-protein activity in later stages of CD4/8 double-positive thymocytes to increase positive selection efficiency
Claudin-4 induction by E-protein activity in later stages of CD4/8 double-positive thymocytes to increase positive selection efficiency
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DOI：
10.1073/pnas.1014178108
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发表时间：
2011-03-08
影响因子：
11.1
通讯作者：
Minato, Nagahiro
中科院分区：
文献类型：
--
作者：
Kawai, Yohei;Hamazaki, Yoko;Minato, Nagahiro
紧密连接蛋白（Clds）是上皮细胞紧密连接链的重要组成部分，在屏障功能中具有核心作用。我们发现，Cld 4出乎意料地表达在正常胸腺淋巴细胞独立的紧密连接。Cld 4的表达主要局限于部分CD 4/CD 8双阳性（DP）细胞。Cld 4 + DP细胞在MHC-I（-/-）II（-/-）小鼠中的比例显著增加，而在Ror γ（-/-）小鼠中的比例降低，并且Cld 4（+）DP细胞比Cld 4-DP细胞含有更高水平的涉及最远端Va和Ja节段的重排Tcra转录物。Cld 4表达水平在E47缺陷小鼠中以基因剂量依赖性方式降低，ChIP分析表明E2 A和HEB与推定的Cldn 4启动子区域的E-box位点结合。在功能上，Cld 4通过与CD 3共连接显示出有效的T细胞受体共刺激活性。Cld 4弥散分布于细胞表面，与静息胸腺细胞中的CD 3无关，与CD 4/lck相关。然而，Cld 4通过抗原呈递细胞被强烈招募到特异性T细胞受体接合的免疫突触。在胎儿胸腺器官培养中，敲低Cldn 4导致DP细胞产生的CD 4/CD 8单阳性细胞减少。这些结果表明，Cld 4诱导的E-蛋白活性在DP细胞的后期阶段，以增加阳性选择的效率，揭示了迄今未被认识的功能的Cld家族蛋白。
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 Ror gamma(-/-)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.