Wiens Matthias, Korzhev Michael, Perovic-Ottstadt Sanja, Luthringer Bérengère, Brandt David, Klein Stefanie, Müller Werner E G
Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Johannes Gutenberg Universität, Mainz, Germany.
Mol Biol Evol. 2007 Mar;24(3):792-804. doi: 10.1093/molbev/msl208. Epub 2006 Dec 26.
During evolution and with the emergence of multicellular animals, the need arose to ward off foreign organisms that threaten the integrity of the animal body. Among many different receptors that participate in the recognition of microbial invaders, toll-like receptors (TLRs) play an essential role in mediating the innate immune response. After binding distinct microbial components, TLRs activate intracellular signaling cascades that result in an induced expression of diverse antimicrobial molecules. Because sponges (phylum Porifera) are filter feeders, they are abundantly exposed to microorganisms that represent a potential threat. Here, we describe the identification, cloning, and deduced protein sequence from 3 major elements of the poriferan innate response (to bacterial lipopeptides): the TLR, the IL-1 receptor-associated kinase-4-like protein (IRAK-4l), and a novel effector caspase from the demosponge Suberites domuncula. Each molecule shares significant sequence similarity with its homologues in higher Metazoa. Sequence homologies were found in particular within the family-specific domains toll/interleukin-1 receptor/resistance (TLR family), Ser/Thr/Tyr kinase domain (IRAK family), and CASc (caspase family). In addition, in situ hybridization and immunohistological analyses revealed an abundance of SDTLR (TLR) transcripts in epithelial layers of the sponge surface (exopinacoderm and endopinacoderm). Furthermore, it is shown that both SDTLR and SDIRAK-4 like (IRAK) are expressed constitutively, regardless of treatment with synthetic triacyl lipopeptide Pam(3)Cys-Ser-(Lys)(4). In contrast, SDCASL (caspase) expression is highly Pam(3)Cys-Ser-(Lys)(4) inducible. However, blocking of the lipopeptide with recombinant TLR prior to its application completely prevented the induced expression of this poriferan caspase. These results underscore that the phylogenetically oldest extant metazoan phylum is provided already with the signaling pathways of the antimicrobial host-defense system of Metazoa.
在进化过程中，随着多细胞动物的出现，抵御威胁动物体完整性的外来生物体的需求应运而生。在众多参与识别微生物入侵者的不同受体中，Toll样受体（TLRs）在介导先天性免疫反应中发挥着至关重要的作用。在结合不同的微生物成分后，TLRs激活细胞内信号级联反应，导致多种抗菌分子的诱导表达。由于海绵动物（多孔动物门）是滤食性动物，它们大量接触到可能构成潜在威胁的微生物。在此，我们描述了来自海绵动物先天性反应（对细菌脂肽）的3个主要元件的鉴定、克隆及推导的蛋白质序列：TLR、白细胞介素-1受体相关激酶-4样蛋白（IRAK-4l）以及来自寻常海绵纲的一种新型效应半胱天冬酶。每个分子与其在高等后生动物中的同源物具有显著的序列相似性。特别在家族特异性结构域Toll/白细胞介素-1受体/抗性（TLR家族）、丝氨酸/苏氨酸/酪氨酸激酶结构域（IRAK家族）和CASc（半胱天冬酶家族）中发现了序列同源性。此外，原位杂交和免疫组织学分析显示，海绵表面上皮层（外皮层和内皮层）中存在大量的SDTLR（TLR）转录本。此外，研究表明，无论是否用合成三酰基脂肽Pam(3)Cys-Ser-(Lys)(4)处理，SDTLR和SDIRAK-4样（IRAK）均组成性表达。相比之下，SDCASL（半胱天冬酶）的表达对Pam(3)Cys-Ser-(Lys)(4)高度可诱导。然而，在应用脂肽之前用重组TLR阻断它可完全阻止这种海绵动物半胱天冬酶的诱导表达。这些结果强调，现存系统发育上最古老的后生动物门已经具备了后生动物抗菌宿主防御系统的信号通路。
