Ganglioside-binding specificities of E. coli enterotoxin LT-IIc: Importance of long-chain fatty acyl ceramide
Ganglioside-binding specificities of E. coli enterotoxin LT-IIc: Importance of long-chain fatty acyl ceramide
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DOI：
10.1093/glycob/cws123
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发表时间：
2013-01-01
期刊：
影响因子：
4.3
通讯作者：
Connell, Terry D.
中科院分区：
文献类型：
--
作者：
Berenson, Charles S.;Nawar, Hesham F.;Connell, Terry D.
细菌热不稳定（LT）肠毒素通过与宿主细胞神经节苷紧密调节的相互作用发出信号。大肠杆菌的LT-IIa和LT-IIb优先与NeuAc α 2-3Gal β 1-3GalNAc末端的神经节苷脂结合，在特异性上具有关键区别。LT- iic是一种新发现的大肠杆菌LT，由一个与LT- iia和LT- iib具有高度同源性的a多肽和一个与LT- iib具有中等同源性的B多肽组成。LT-IIc的细胞毒性低于LT-IIa和LT-IIb。我们推测lt - ii -宿主细胞相互作用是由免疫细胞神经节苷脂受体的特定结构属性调节的，并设计了实验来验证这一假设。覆盖免疫印迹对多种神经和巨噬细胞神经节苷脂的检测表明，LT-IIc与有限范围的神经节苷脂结合，每种神经节苷脂都具有NeuAc α 2-3Gal β 1-3GalNAc和必需的末端唾液酸。LT-IIc不通过短链脂肪酸酰神经酰胺与GM1a结合。对小鼠腹膜巨噬细胞的多种已知神经节苷脂结构构建亲和覆盖免疫印迹，证实与GM1a结合的LT-IIc由长链脂肪酰基神经酰胺组成。结果证实，LT-IIc也与RAW264.7细胞的GM1a结合，GM1a由长链脂肪酰基神经酰胺组成。因此，lt - iic -神经节苷脂结合与LT-IIa和LT-IIb的结合明显不同。LT-IIc的结合不仅取决于碳水化合物的组成，还取决于神经酰胺部分对GM1a低聚糖部分的取向。这些研究首次证明了lt神经节苷脂依赖于神经酰胺的组成，并强调了长链脂肪酰基神经酰胺对宿主细胞相互作用的贡献。
Bacterial heat-labile (LT) enterotoxins signal through tightly regulated interactions with host cell gangliosides. LT-IIa and LT-IIb of Escherichia coli bind preferentially to gangliosides with a NeuAc alpha 2-3Gal beta 1-3GalNAc terminus, with key distinctions in specificity. LT-IIc, a newly discovered E. coli LT, is comprised of an A polypeptide with high homology, and a B polypeptide with moderate homology, to LT-IIa and LT-IIb. LT-IIc is less cytotoxic than LT-IIa and LT-IIb. We theorized that LT-IIc-host cell interaction is regulated by specific structural attributes of immune cell ganglioside receptors and designed experiments to test this hypothesis. Overlay immunoblotting to a diverse array of neural and macrophage gangliosides indicated that LT-IIc bound to a restrictive range of gangliosides, each possessing a NeuAc alpha 2-3Gal beta 1-3GalNAc with a requisite terminal sialic acid. LT-IIc did not bind to GM1a with short-chain fatty acyl ceramides. Affinity overlay immunoblots, constructed to a diverse array of known ganglioside structures of murine peritoneal macrophages, established that LT-IIc bound to GM1a comprised of long-chain fatty acyl ceramides. Findings were confirmed with LT-IIc also binding to GM1a of RAW264.7 cells, comprised of a long-chain fatty acyl ceramide. Thus, LT-IIc-ganglioside binding differs distinctly from that of LT-IIa and LT-IIb. LT-IIc binding is not just dependent on carbohydrate composition, but also upon the orientation of the oligosaccharide portion of GM1a by the ceramide moiety. These studies are the first demonstration of LT-ganglioside dependence upon ceramide composition and underscore the contribution of long-chain fatty acyl ceramides to host cell interactions.