CHARACTERIZATION OF SIGNAL TRANSDUCTION SYSTEM OF IL-13 RECEPTOR -MOLECULAR CLONING OF A NOVEL SIGNAL TRANSDUCTION MOLECULES FOR IL-13 SIGNALING.

目前已知的IL-13信号转导途径主要是通过IL-4Ra，但对IL-13Ra1‘S下游信号转导途径知之甚少。利用酵母三杂交系统寻找与IL-13受体相关的蛋白质。我们从人胎儿cDNA文库中发现了一个新的IL-13Ra1结合蛋白，命名为IL13RBP1(Genbank登录号：A242456)。经Northern印迹分析，所有受试组织中均检测到4.4kb和2.4kb两种IL13RBP1mRNA。在精巢中，在2.5-2.7kb之间检测到额外的条带。从人睾丸cDNA文库中克隆的IL13RBP1基因全长2568个氨基酸，开放阅读框为692个氨基酸。而在正常组织中，IL13RBP1的开放阅读框为625aa，与睾丸相比，其中部缺少插入片段。在酵母双杂交系统和哺乳动物细胞中证实了IL-13RBP1‘S与IL-13Ral的相关性：有趣的是，这种关联不依赖于酪氨酸磷酸化。IL13RBP1除了与IL-13Ra1相互作用外，还能抑制IL-4和IL-13刺激下的状态酪氨酸磷酸化。此外，瞬时表达的IL13RBP1还部分抑制了STAT6‘S的DNA结合活性和转录活性。有趣的是，IL13RBP1编码的蛋白与TRAF3相关的微管相互作用蛋白MIP-T3相同。MIP-T3与TRAF3蛋白发生结构性相互作用。体外实验发现MIP-T3可与微管和微管蛋白结合。这些结果表明，IL13RBP1/MIP-T3可能同时在IL-13和CD40信号通路中发挥作用，但具体机制有待进一步研究。我们的结果表明，IL13RBP1是一种新的IL-13信号抑制因子，可能是一种有用的分子，可用于改善包括过敏、肺部哮喘、寄生虫感染和癌症在内的多种疾病，其中IL-13起核心作用。

Current known IL-13 signaling is mainly mediated through IL-4Ra, but few are known about IL-13Ra1's downstream. Yeast tri-hybrid system was utilized for searching proteins which can associate with IL-13 receptor. We found a novel IL-13Ra1 binding protein from human fetal cDNA library and named as IL13RBP1 (Genbank Accession Number : A242456). Through northern blot analysis, 2 kinds of IL13RBP1 mRNA, 4.4 kb and 2.4 kb, were detected in all tissues examined. In testis, additional bands were detected between 2.5-2.7 kb. IL13RBP1 gene cloned from human testis cDNA library has a whole length of 2568 by and an open reading frame of 692 aa. While in normal tissues, IL13RBP1 has an open reading frame of 625 aa, which lacks an insert fragment in the middle part compared that in testis. IL13RBP1's association with IL-13Ral was proved in yeast two-, tri-hybrid system and mammalian cells : Interestingly, the association was independent of tyrosine phosphorylation. Besides interaction with IL-13Ra1, IL13RBP1 was found to inhibit STATE tyrosine phosphorylation in response to IL-4 and IL-13 stimulation. Furthermore, STAT6's DNA binding activity and transcriptional activity were also partly inhibited by transient expressed IL13RBP1 Interestingly, IL13RBP1 was found to encode the same protein as MIP-T3 (Microtubule interacted protein that associated with TRAF3). MIP-T3 constitutively interacts with TRAF3 protein. MIP-T3 was found to bind to microtubule and tubulin in vitro. These findings indicate that ILl3RBPl/MIP-T3 may play a role in both IL-13 and CD40 signaling, but detailed mechanism has to be further investigated.Our results suggest that IL13RBP1 is a novel inhibitor of IL-13 signaling and may be a useful molecular in ameliorating various conditions including allergies, pulmonary asthma, parasitic infection and cancer in which IL-13 plays a central role.