Nasir Waqas, Frank Martin, Kunze Angelika, Bally Marta, Parra Francisco, Nyholm Per-Georg, Höök Fredrik, Larson Göran
Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg , Gothenburg, Sweden.
Biognos AB , Generatorsgatan 1, P.O. Box 8963, 40274 Gothenburg, Sweden.
ACS Chem Biol. 2017 May 19;12(5):1288-1296. doi: 10.1021/acschembio.7b00152. Epub 2017 Mar 27.
Virus entry depends on biomolecular recognition at the surface of cell membranes. In the case of glycolipid receptors, these events are expected to be influenced by how the glycan epitope close to the membrane is presented to the virus. This presentation of membrane-associated glycans is more restricted than that of glycans in solution, particularly because of orientational constraints imposed on the glycolipid through its lateral interactions with other membrane lipids and proteins. We have developed and employed a total internal reflection fluorescence microscopy-based binding assay and a scheme for molecular dynamics (MD) membrane simulations to investigate the consequences of various glycan presentation effects. The system studied was histo-blood group antigen (HBGA) epitopes of membrane-bound glycosphingolipids (GSLs) derived from small intestinal epithelium of humans (type 1 chain) and dogs (type 2 chain) interacting with GII.4 norovirus-like particles. Our experimental results showed strong binding to all lipid-linked type 1 chain HBGAs but no or only weak binding to the corresponding type 2 chain HBGAs. This is in contrast to results derived from STD experiments with free HBGAs in solution where binding was observed for Lewis x. The MD data suggest that the strong binding to type 1 chain glycolipids was due to the well-exposed (1,2)-linked α-l-Fucp and (1,4)-linked α-l-Fucp residues, while the weaker binding or lack of binding to type 2 chain HBGAs was due to the very restricted accessibility of the (1,3)-linked α-l-Fucp residue when the glycolipid is embedded in a phospholipid membrane. Our results not only contribute to a general understanding of protein-carbohydrate interactions on model membrane surfaces, particularly in the context of virus binding, but also suggest a possible role of human intestinal GSLs as potential receptors for norovirus uptake.
病毒进入细胞依赖于细胞膜表面的生物分子识别。对于糖脂受体而言，这些过程预计会受到靠近膜的聚糖表位呈现给病毒的方式的影响。与溶液中的聚糖相比，膜相关聚糖的这种呈现受到更多限制，特别是由于糖脂通过与其他膜脂和蛋白质的侧向相互作用而受到的取向限制。我们开发并采用了基于全内反射荧光显微镜的结合测定法和分子动力学（MD）膜模拟方案，以研究各种聚糖呈现效应的后果。所研究的系统是源自人类小肠上皮（1型链）和狗（2型链）的膜结合糖鞘脂（GSL）的组织血型抗原（HBGA）表位与GII.4诺如病毒样颗粒相互作用。我们的实验结果表明，它与所有脂质连接的1型链HBGA有强烈结合，但与相应的2型链HBGA没有结合或只有弱结合。这与在溶液中对游离HBGA进行STD实验的结果形成对比，在该实验中观察到了与Lewis x的结合。MD数据表明，与1型链糖脂的强烈结合是由于暴露良好的（1,2）连接的α - l - Fucp和（1,4）连接的α - l - Fucp残基，而与2型链HBGA的较弱结合或无结合是由于当糖脂嵌入磷脂膜时，（1,3）连接的α - l - Fucp残基的可及性非常有限。我们的结果不仅有助于对模型膜表面上蛋白质 - 碳水化合物相互作用的一般理解，特别是在病毒结合的背景下，而且还表明人类肠道GSL作为诺如病毒摄取的潜在受体可能发挥的作用。
