Human Coronavirus HKU1 Spike Protein Uses O-Acetylated Sialic Acid as an Attachment Receptor Determinant and Employs Hemagglutinin-Esterase Protein as a Receptor-Destroying Enzyme
Human Coronavirus HKU1 Spike Protein Uses O-Acetylated Sialic Acid as an Attachment Receptor Determinant and Employs Hemagglutinin-Esterase Protein as a Receptor-Destroying Enzyme
复制标题
DOI：
10.1128/jvi.00854-15
复制
发表时间：
2015-07-01
影响因子：
5.4
通讯作者：
Sui, Jianhua
中科院分区：
文献类型：
--
作者：
Huang, Xingchuan;Dong, Wenjuan;Sui, Jianhua
人类冠状病毒（hCoV） HKU1是迄今为止发现的六种hCoV之一，也是唯一一种未识别细胞受体的hCoV。hCoV-HKU1编码a组β冠状病毒（2a组）特有的血凝素酯酶（HE）蛋白。HKU1-HE的功能在很大程度上仍未确定。在这项研究中，我们检测了hCoV-HKU1刺突S1结构域与一组细胞的结合，发现S1可以特异性地结合在人横纹肌肉瘤细胞系RD的细胞表面。用神经氨酸酶（NA）和胰蛋白酶预处理RD细胞大大降低了这种结合，表明这种结合是由唾液酸对糖蛋白的介导的。然而，与其他2a组冠状病毒不同，例如hCoV-OC43，其9- o -乙酰化唾液酸（9-O-Ac-Sia）作为受体决定因素，HKU1-S1既不与含有9-O-Ac-Sia的糖蛋白结合，也不与大鼠和小鼠红细胞结合。尽管如此，HKU1-HE与OC43-HE相似，也具有唾液酸- o -乙酰酯酶活性，并作为一种受体破坏酶（RDE），能够消除HKU1-S1与RD细胞的结合，而o -乙酰酯酶失活的HKU1-HE突变体则失去了这种能力。使用原代人纤毛气道上皮（HAE）细胞培养物（hCoV-HKU1感染的唯一体外复制模型），我们证实了用HE预处理HAE细胞而不是酶失活突变体阻断hCoV-HKU1感染。这些结果表明，hCoV-HKU1利用O-Ac-Sia作为细胞附着受体决定因子启动宿主细胞感染，其HE蛋白具有相应的唾液酸- o -乙酰酯酶RDE活性。人类冠状病毒（hCoV）是重要的人类呼吸道病原体。在迄今鉴定的6种hcov中，只有hCoV-HKU1没有明确的细胞受体。目前尚不清楚血凝素酯酶（HE）蛋白是否在病毒侵入中起作用。在这项研究中，我们发现，与其他2a组冠状病毒成员相似，糖蛋白上的唾液酸片段是hCoV-HKU1感染的关键受体决定因素。有趣的是，这种病毒似乎使用了一种不同于其他2a组冠状病毒使用的唾液酸。此外，我们确定HKU1-HE蛋白是一种o -乙酰酯酶，并作为hCoV-HKU1的受体破坏酶（RDE）。这是第一个证明hCoV-HKU1利用糖蛋白上某些类型的o -乙酰化唾液酸残基来启动宿主细胞感染，并且HKU1-HE蛋白具有唾液酸- o -乙酰酯酶RDE活性的研究。
Human coronavirus (hCoV) HKU1 is one of six hCoVs identified to date and the only one with an unidentified cellular receptor. hCoV-HKU1 encodes a hemagglutinin-esterase (HE) protein that is unique to the group a betacoronaviruses (group 2a). The function of HKU1-HE remains largely undetermined. In this study, we examined binding of the S1 domain of hCoV-HKU1 spike to a panel of cells and found that the S1 could specifically bind on the cell surface of a human rhabdomyosarcoma cell line, RD. Pretreatment of RD cells with neuraminidase (NA) and trypsin greatly reduced the binding, suggesting that the binding was mediated by sialic acids on glycoproteins. However, unlike other group 2a CoVs, e.g., hCoV-OC43, for which 9-O-acetylated sialic acid (9-O-Ac-Sia) serves as a receptor determinant, HKU1-S1 bound with neither 9-O-Ac-Sia-containing glycoprotein(s) nor rat and mouse erythrocytes. Nonetheless, the HKU1-HE was similar to OC43-HE, also possessed sialate-O-acetylesterase activity, and acted as a receptor-destroying enzyme (RDE) capable of eliminating the binding of HKU1-S1 to RD cells, whereas the O-acetylesterase-inactive HKU1-HE mutant lost this capacity. Using primary human ciliated airway epithelial (HAE) cell cultures, the only in vitro replication model for hCoV-HKU1 infection, we confirmed that pretreatment of HAE cells with HE but not the enzymatically inactive mutant blocked hCoV-HKU1 infection. These results demonstrate that hCoV-HKU1 exploits O-Ac-Sia as a cellular attachment receptor determinant to initiate the infection of host cells and that its HE protein possesses the corresponding sialate-O-acetylesterase RDE activity.IMPORTANCEHuman coronaviruses (hCoV) are important human respiratory pathogens. Among the six hCoVs identified to date, only hCoV-HKU1 has no defined cellular receptor. It is also unclear whether hemagglutinin-esterase (HE) protein plays a role in viral entry. In this study, we found that, similarly to other members of the group 2a CoVs, sialic acid moieties on glycoproteins are critical receptor determinants for the hCoV-HKU1 infection. Interestingly, the virus seems to employ a type of sialic acid different from those employed by other group 2a CoVs. In addition, we determined that the HKU1-HE protein is an O-acetylesterase and acts as a receptor-destroying enzyme (RDE) for hCoV-HKU1. This is the first study to demonstrate that hCoV-HKU1 uses certain types of O-acetylated sialic acid residues on glycoproteins to initiate the infection of host cells and that the HKU1-HE protein possesses sialate-O-acetylesterase RDE activity.