Novel Bacterial Lipoprotein Structures Conserved in Low-GC Content Gram-positive Bacteria Are Recognized by Toll-like Receptor 2
Novel Bacterial Lipoprotein Structures Conserved in Low-GC Content Gram-positive Bacteria Are Recognized by Toll-like Receptor 2
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DOI：
10.1074/jbc.m111.292235
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发表时间：
2012-04-13
影响因子：
4.8
通讯作者：
Lee, Bok Luel
中科院分区：
文献类型：
--
作者：
Kurokawa, Kenji;Ryu, Kyoung-Hwa;Lee, Bok Luel
诱导宿主先天免疫反应的细菌脂蛋白/脂肽由哺乳动物 Toll 样受体 2 (TLR2) 感知。这些细菌脂蛋白在结构上根据是否存在酰胺连接的脂肪酸而分为两组：二酰化脂蛋白或三酰化脂蛋白。根据基因组中缺乏一种修饰酶，可以预测低 GC 含量的革兰氏阳性细菌和支原体中存在二酰化脂蛋白；然而，我们最近确定了低 GC 革兰氏阳性金黄色葡萄球菌中的三酰化结构，这对其他低 GC 含量革兰氏阳性细菌中的实际脂蛋白结构提出了疑问。在这里，通过深入的质谱分析，我们从低GC革兰氏阳性粪肠球菌、蜡样芽孢杆菌、血链球菌和保加利亚乳杆菌中鉴定出一种新颖且独特的细菌脂蛋白结构，其中含有N-酰基-S-单酰基-甘油基-半胱氨酸（称为溶血结构）。两种纯化的天然溶血型脂蛋白以 TLR2 依赖性和 TLR1 独立性方式诱导小鼠巨噬细胞产生促炎细胞因子，但对 TLR6 的依赖性不同。此外，还鉴定了另外两种新的脂蛋白结构。一种是含有N-乙酰基-S-二酰基甘油基-半胱氨酸的“N-乙酰基”脂蛋白结构，在包括枯草芽孢杆菌在内的五种革兰氏阳性菌中发现。 N-乙酰脂蛋白通过 TLR2/6 异二聚体诱导促炎细胞因子。另一种是在支原体菌株中发现的，是一种不寻常的二酰基脂蛋白结构，在脂质修饰的半胱氨酸残基之前含有两个氨基酸。总而言之，我们的结果表明存在新的 TLR2 刺激溶血和 N-乙酰形式的脂蛋白，这些脂蛋白在低 GC 含量的革兰氏阳性细菌中保守，并为细菌脂蛋白生物合成中涉及的尚未鉴定的关键酶的存在提供了明确的证据。
Bacterial lipoproteins/lipopeptides inducing host innate immune responses are sensed by mammalian Toll-like receptor 2 (TLR2). These bacterial lipoproteins are structurally divided into two groups, diacylated or triacylated lipoproteins, by the absence or presence of an amide-linked fatty acid. The presence of diacylated lipoproteins has been predicted in low-GC content Gram-positive bacteria and mycoplasmas based on the absence of one modification enzyme in their genomes; however, we recently determined triacylated structures in low-GC Gram-positive Staphylococcus aureus, raising questions about the actual lipoprotein structure in other low-GC content Gram-positive bacteria. Here, through intensive MS analyses, we identified a novel and unique bacterial lipoprotein structure containing an N-acyl-S-monoacyl-glyceryl-cysteine (named the lyso structure) from low-GC Gram-positive Enterococcus faecalis, Bacillus cereus, Streptococcus sanguinis, and Lactobacillus bulgaricus. Two of the purified native lyso-form lipoproteins induced proinflammatory cytokine production from mice macrophages in a TLR2-dependent and TLR1-independent manner but with a different dependence on TLR6. Additionally, two other new lipoprotein structures were identified. One is the "N-acetyl" lipoprotein structure containing N-acetyl-S-diacylglyceryl-cysteine, which was found in five Gram-positive bacteria, including Bacillus subtilis. The N-acetyl lipoproteins induced the proinflammatory cytokines through the TLR2/6 heterodimer. The other was identified in a mycoplasma strain and is an unusual diacyl lipoprotein structure containing two amino acids before the lipid-modified cysteine residue. Taken together, our results suggest the existence of novel TLR2-stimulating lyso and N-acetyl forms of lipoproteins that are conserved in low-GC content Gram-positive bacteria and provide clear evidence for the presence of yet to be identified key enzymes involved in the bacterial lipoprotein biosynthesis.