Blanchard Helen, Yu Xing, Coulson Barbara S, von Itzstein Mark
Institute for Glycomics, Griffith University, Gold Coast Campus, PMB 50 Gold Coast Mail Centre, Queensland, 9726, Australia.
J Mol Biol. 2007 Apr 6;367(4):1215-26. doi: 10.1016/j.jmb.2007.01.028. Epub 2007 Jan 13.
Rotavirus infection leads to the death of half a million children annually. The exact specifics of interaction between rotavirus particles and host cells enabling invasion and infection have remained elusive. Host cell oligosaccharides are critical components, and their involvement aids the virus in cell-recognition and attachment, as well as dictation of the remarkable host-specificity that rotaviruses demonstrate. Interaction between the rotavirus spike-protein carbohydrate-binding domain (VP8*) and cell surface oligosaccharides facilitate virus recognition of host cells and attachment. Rotaviruses are considered, controversially, to recognise vastly different carbohydrate structures and either with incorporation of terminal sialic acid or without, as assessed by their ability to infect cells that have been pre-treated with sialidases. Herein, the X-ray crystallographic structures of VP8* from the sialidase insensitive Wa and the sialidase sensitive CRW-8 rotavirus strains that cause debilitating gastroenteritis in human and pig are reported. Striking differences are apparent regarding recognition of the sialic acid derivative methyl alpha-D-N-acetylneuraminide, presenting the first experimental evidence of the inability of the human rotavirus strain to bind this monosaccharide, that correlates with Wa and CRW-8 recognising sialidase-resistant and sialidase-sensitive receptors, respectively. Identified are structural features that provide insight in attainment of substrate specificity exhibited by porcine strains as compared to rhesus rotavirus. Revealed in the CRW-8 VP8* structure is an additional bound ligand that intriguingly, is within a cleft located equivalent to the carbohydrate-binding region of galectins, and is suggestive of a new region for interaction with cell-surface carbohydrates. This novel result and detailed comparison of our representative sialidase-sensitive CRW-8 and insensitive Wa VP8* structures with those reported leads to our hypothesis that this groove is used for binding carbohydrates, and that for the human strains, as for other sialidase-insensitive strains could represent a major oligosaccharide-binding region.
轮状病毒感染每年导致五十万儿童死亡。轮状病毒颗粒与宿主细胞之间相互作用的确切细节，使得病毒能够入侵和感染，这一点仍然难以捉摸。宿主细胞寡糖是关键成分，它们的参与有助于病毒进行细胞识别和附着，以及决定轮状病毒所表现出的显著宿主特异性。轮状病毒刺突蛋白碳水化合物结合结构域（VP8*）与细胞表面寡糖之间的相互作用促进了病毒对宿主细胞的识别和附着。有争议的是，轮状病毒被认为能够识别截然不同的碳水化合物结构，无论是否结合末端唾液酸，这可以通过它们感染经唾液酸酶预处理的细胞的能力来评估。在此，报道了来自对唾液酸酶不敏感的Wa株和对唾液酸酶敏感的CRW-8轮状病毒株的VP8的X射线晶体结构，这两种病毒分别在人类和猪中引起使人虚弱的肠胃炎。在识别唾液酸衍生物α-D-N-乙酰神经氨酸甲酯方面存在显著差异，这首次提供了实验证据，表明人类轮状病毒株无法结合这种单糖，这与Wa株和CRW-8株分别识别抗唾液酸酶和对唾液酸酶敏感的受体相关。已确定的结构特征为了解猪株与恒河猴轮状病毒相比所表现出的底物特异性提供了线索。在CRW-8 VP8结构中发现了一个额外的结合配体，有趣的是，它位于与半乳糖凝集素碳水化合物结合区域相当的裂隙内，这表明存在一个与细胞表面碳水化合物相互作用的新区域。这一新颖的结果以及我们将具有代表性的对唾液酸酶敏感的CRW-8和不敏感的Wa VP8*结构与已报道结构进行的详细比较，使我们提出这样的假设：这个凹槽用于结合碳水化合物，对于人类毒株以及其他对唾液酸酶不敏感的毒株来说，它可能代表一个主要的寡糖结合区域。
