Delineation of a novel pathway that regulates CD154 (CD40 ligand) expression
Delineation of a novel pathway that regulates CD154 (CD40 ligand) expression
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DOI：
10.1128/mcb.23.2.510-525.2003
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发表时间：
2003-01-01
影响因子：
5.3
通讯作者：
Rigby, WFC
中科院分区：
文献类型：
--
作者：
Hamilton, BJ;Genin, A;Rigby, WFC
活化的T淋巴细胞表达的CD 154（CD 40配体）在体液和细胞免疫中起着重要作用。这种蛋白质在建立免疫应答中的根本重要性使其成为免疫调节的有吸引力的靶标。几项研究表明，CD 154的表达在mRNA周转水平上以不同于其他细胞因子基因的方式进行调节。我们已经纯化、测序并表征了结合CD 154 3'非翻译区（3' UTR）的两种主要蛋白质作为多聚嘧啶道结合蛋白（PTB）家族的成员。这些蛋白质之一是以前未报道的选择性剪接PTB同种型，我们称之为PTB-T。这些蛋白质与CD 154 3 'UTR内缺乏任何已知顺式作用不稳定元件的多聚嘧啶富集区相互作用。CD 154 YUTR的多聚嘧啶富集区是介导报告基因表达和mRNA积累变化的必要和充分条件，表明存在一种新的顺式作用不稳定元件。使用四环素反应报告基因方法证实了在多嘧啶富集区存在顺式作用不稳定元件。该顺式作用元件的功能似乎依赖于PTB和PTB-T的相对细胞质水平。共转染编码PTB-T的载体持续降低CD 154 3 'UTR依赖性荧光素酶表达。相反，转染编码PTB的质粒倾向于增加CD 154 3 'UTR依赖性荧光素酶表达。因此，CD 154 YUTR含有一个新的顺式作用元件，其功能由PTB和PTB-T的结合决定。这些数据确定了一种调节CD 154表达的特定途径，该途径可能被选择性靶向用于治疗自身免疫性疾病和同种异体移植排斥。
The expression of CD154 (CD40 ligand) by activated T lymphocytes plays a central role in humoral and cellular immunity. The fundamental importance of this protein in mounting an immune response has made it an attractive target for immunomodulation. Several studies have demonstrated that CD154 expression is regulated at the level of mRNA turnover in a manner distinct from other cytokine genes. We have purified, sequenced, and characterized the two major proteins that bind the CD154 3' untranslated region (3'UTR) as members of the polypyrimidine tract binding protein (PTB) family. One of these proteins is a previously unreported alternatively spliced PTB isoform, which we call PTB-T. These proteins interact with a polypyrimidine-rich region within the CD154 3'UTR that lacks any known cis-acting instability elements. The polypyrimidine-rich region of the CD154 YUTR was both necessary and sufficient to mediate changes in reporter gene expression and mRNA accumulation, indicating the presence of a novel cis-acting instability element. The presence of a cis-acting instability element in the polypyrimidine-rich region was confirmed using a tetracycline-responsive reporter gene approach. The function of this cis-acting element appears to be dependent on the relative cytoplasmic levels of PTB and PTB-T. Cotransfection of vectors encoding PTB-T consistently decreased the CD154 3'UTR-dependent luciferase expression. In contrast, transfection of plasmids encoding PTB tended to increase CD154 3'UTR-dependent luciferase expression. Thus, the CD154 YUTR contains a novel cis-acting element whose function is determined by the binding of PTB and PTB-T. These data identify a specific pathway that regulates CD154 expression that can potentially be selectively targeted for the treatment of autoimmune disease and allograft rejection.