近日來(lái)自浙江大學(xué)生命科學(xué)學(xué)院細(xì)胞與發(fā)育生物學(xué)研究所的研究人員從硬骨魚(yú)中首次鑒別出Toll-IL-1受體家族的一個(gè)新成員DIGIRR，并證實(shí)其在IL-1信號(hào)通路中發(fā)揮重要的負(fù)調(diào)控作用。這一研究成果于7月29日在線發(fā)表在著名的免疫學(xué)期刊《免疫學(xué)期刊》（The Journal of Immunology）上。
Toll蛋白樣受體（TLR）是在研究果蠅胚胎腹背側(cè)體軸形成過(guò)程中新發(fā)現(xiàn)的一種介導(dǎo)機(jī)體天然免疫(innate immunity)的受體蛋白。因其結(jié)構(gòu)、功能及信號(hào)轉(zhuǎn)導(dǎo)途徑均與白介素-1受體（IL-1R）類(lèi)似，故統(tǒng)歸于Toll/IL-1R家族。哺乳動(dòng)物Toll受體稱(chēng)為T(mén)oll樣受體（Toll like receptors, TLRs）。迄今為止，10種人類(lèi)TLRs(human TLRs,hTLRs)已被先后發(fā)現(xiàn)。近年來(lái)大量研究證實(shí)Toll/IL-1R家族成員在炎癥、免疫、病源體識(shí)別中都起著十分重要的作用，參與許多疾病的發(fā)病過(guò)程，與傳染病、腫瘤、心血管病、自身免 疫性疾病、過(guò)敏等都有著密切關(guān)系。它亦是研究和開(kāi)發(fā)新藥的一個(gè)新的靶點(diǎn)，故受到國(guó)際醫(yī)學(xué)生物學(xué)廣泛關(guān)注。然而目前對(duì)科學(xué)家們其信號(hào)通路的負(fù)調(diào)控機(jī)制尚缺乏深入理解。
在這篇文章中，研究人員從三種硬骨魚(yú)模型中首次鑒定出該家族的一個(gè)新成員，命名為Double-Ig-IL-1R Related Molecule (DIGIRR)，并證實(shí)這個(gè)DIGIRR分子包含有兩個(gè)胞外Ig結(jié)構(gòu)域，一個(gè)胞內(nèi)Arg-Tyr536位點(diǎn)突TIR結(jié)構(gòu)域，且定位于高爾基體的胞內(nèi)受體。這些特征表明DIGIRR有別于其他已知的Toll/IL-1R家族成員。隨后研究人員在體外實(shí)驗(yàn)中證實(shí)將DIGIRR注入到斑馬魚(yú)胚胎中可顯著抑制脂多糖（LPS）和IL-1β誘導(dǎo)的NF-κB激活。當(dāng)研究人員在斑馬魚(yú)體內(nèi)用小干擾RNA(siRNA)沉默DIGIRR基因表達(dá)時(shí)發(fā)現(xiàn)在DIGIRR沉默的肝腎組織及白細(xì)胞中IL-1β即促炎細(xì)胞因子IL-6的表達(dá)水平顯著增高。研究結(jié)果表明DIGIRR是LPS和IL-1β介導(dǎo)的信號(hào)傳導(dǎo)通路及炎癥反應(yīng)中發(fā)揮重要的負(fù)調(diào)控因子作用。此外研究人員還證實(shí)一個(gè)胞外Ig結(jié)構(gòu)域的缺失和胞內(nèi)TIR結(jié)構(gòu)域中Arg-Tyr536位點(diǎn)的突變，是IL-1R家族成員演化為負(fù)調(diào)節(jié)受體的重要機(jī)制。
浙江大學(xué)生命科學(xué)學(xué)院的邵建忠教授及項(xiàng)黎新副教授為這篇文章的共同通訊作者。這一研究獲得了國(guó)家基礎(chǔ)研究發(fā)展規(guī)劃（973）項(xiàng)目（2006CB101805）、國(guó)家高技術(shù)研究發(fā)展計(jì)劃（863）項(xiàng)目（2008AA09Z409）、國(guó)家自然科學(xué)基金（30871936, 31072234）以及浙江省科學(xué)技術(shù)基金（2007C12011）的資助。
Discovery of the DIGIRR Gene from Teleost Fish: A Novel Toll–IL-1 Receptor Family Member Serving as a Negative Regulator of IL-1 Signaling
Yi-feng Gu, Yu Fang, Yang Jin, Wei-ren Dong, Li-xin Xiang and Jian-zhong Shao
Toll–IL-1R (TIR) family members play crucial roles in a variety of defense, inflammatory, injury, and stress responses. Although they have been widely investigated in mammals, little is known about TIRs in ancient vertebrates. In this study, we report a novel double Ig IL-1R related molecule (DIGIRR) from three model fish (Tetraodon nigroviridis, Gasterosteus aculeatus, and Takifugu rubripes), adding a previously unknown homolog to the TIR family. This DIGIRR molecule contains two Ig-like domains in the extracellular region, one Arg-Tyr–mutated TIR domain in the intracellular region, and a unique subcellular distribution within the Golgi apparatus. These characteristics distinguish DIGIRR from other known family members. In vitro injection of DIGIRR into zebrafish embryos dramatically inhibited LPS-induced and IL-1β–induced NF-κB activation. Moreover, in vivo knockdown of DIGIRR by small interfering RNA significantly promoted the expression of IL-1β–stimulated proinflammatory cytokines (IL-6 and IL-1β) in DIGIRR-silenced liver and kidney tissues and in leukocytes. These results strongly suggest that DIGIRR is an important negative regulator of LPS-mediated and IL-1β–mediated signaling pathways and inflammatory responses. The Arg-Tyr–mutated site disrupted the signal transduction ability of DIGIRR TIR. Evolutionally, we propose a hypothesis that DIGIRR and single Ig IL-1R related molecule (SIGIRR) might originate from a common ancient IL-1R–like molecule that lost one (in DIGIRR) or two (in SIGIRR) extracellular Ig-like domains and intracellular Ser and Arg-Tyr amino acids. DIGIRR might be an evolutionary “transitional molecule” between IL-1R and SIGIRR, representing a shift from a potent receptor to a negative regulator. These results help define the evolutionary history of TIR family members and their associated signaling pathways and mechanisms.
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