Wullaert Andy, Verstrepen Lynn, Van Huffel Sofie, Adib-Conquy Minou, Cornelis Sigrid, Kreike Marja, Haegman Mira, El Bakkouri Karim, Sanders Matthew, Verhelst Kelly, Carpentier Isabelle, Cavaillon Jean-Marc, Heyninck Karen, Beyaert Rudi
Unit of Molecular Signal Transduction in Inflammation, Department for Molecular Biomedical Research, Flanders Interuniversity Institute for Biotechnology, Ghent University, Belgium.
J Biol Chem. 2007 Jan 5;282(1):81-90. doi: 10.1074/jbc.M607481200. Epub 2006 Nov 6.
Recognition of lipopolysaccharide (LPS) by Toll-like receptor (TLR)4 initiates an intracellular signaling pathway leading to the activation of nuclear factor-kappaB (NF-kappaB). Although LPS-induced activation of NF-kappaB is critical to the induction of an efficient immune response, excessive or prolonged signaling from TLR4 can be harmful to the host. Therefore, the NF-kappaB signal transduction pathway demands tight regulation. In the present study, we describe the human protein Listeria INDuced (LIND) as a novel A20-binding inhibitor of NF-kappaB activation (ABIN) that is related to ABIN-1 and -2 and, therefore, is further referred to as ABIN-3. Similar to the other ABINs, ABIN-3 binds to A20 and inhibits NF-kappaB activation induced by tumor necrosis factor, interleukin-1, and 12-O-tetradecanoylphorbol-13-acetate. However, unlike the other ABINs, constitutive expression of ABIN-3 could not be detected in different human cells. Treatment of human monocytic cells with LPS strongly induced ABIN-3 mRNA and protein expression, suggesting a role for ABIN-3 in the LPS/TLR4 pathway. Indeed, ABIN-3 overexpression was found to inhibit NF-kappaB-dependent gene expression in response to LPS/TLR4 at a level downstream of TRAF6 and upstream of IKKbeta. NF-kappaB inhibition was mediated by the ABIN-homology domain 2 and was independent of A20 binding. Moreover, in vivo adenoviral gene transfer of ABIN-3 in mice reduced LPS-induced NF-kappaB activity in the liver, thereby partially protecting mice against LPS/D-(+)-galactosamine-induced mortality. Taken together, these results implicate ABIN-3 as a novel negative feedback regulator of LPS-induced NF-kappaB activation.
Toll样受体（TLR）4对脂多糖（LPS）的识别启动了一条细胞内信号通路，导致核因子-κB（NF-κB）活化。虽然LPS诱导的NF-κB活化对于诱导有效的免疫反应至关重要，但来自TLR4的过度或延长信号传导可能对宿主有害。因此，NF-κB信号转导通路需要严格调控。在本研究中，我们将人源蛋白质李斯特菌诱导蛋白（LIND）描述为一种新型的NF-κB活化A20结合抑制剂（ABIN），它与ABIN-1和-2相关，因此进一步称为ABIN-3。与其他ABINs类似，ABIN-3与A20结合并抑制由肿瘤坏死因子、白细胞介素-1和12-O-十四酰佛波醇-13-乙酸酯诱导的NF-κB活化。然而，与其他ABINs不同，在不同的人类细胞中未检测到ABIN-3的组成型表达。用LPS处理人单核细胞强烈诱导ABIN-3 mRNA和蛋白表达，表明ABIN-3在LPS/TLR4通路中起作用。事实上，发现ABIN-3过表达在TRAF6下游和IKKβ上游水平抑制对LPS/TLR4应答的NF-κB依赖性基因表达。NF-κB抑制由ABIN同源结构域2介导，且独立于A20结合。此外，在小鼠体内进行ABIN-3的腺病毒基因转移降低了肝脏中LPS诱导的NF-κB活性，从而部分保护小鼠免受LPS/D-（+）-半乳糖胺诱导的死亡。综上所述，这些结果表明ABIN-3是LPS诱导的NF-κB活化的新型负反馈调节因子。
