Deglycosylation of FcalphaR at N58 increases its binding to IgA.
Deglycosylation of FcalphaR at N58 increases its binding to IgA.
复制标题
DOI：
10.1093/glycob/cwq048
复制
发表时间：
2010-07
期刊：
影响因子：
4.3
通讯作者：
Jing Xue;Qing-huan Zhao;Li-ping Zhu;Wei Zhang
中科院分区：
文献类型：
--
作者：
Jing Xue;Qing-huan Zhao;Li-ping Zhu;Wei Zhang
FcalphaR （CD89）是免疫球蛋白A （IgA）的Fc受体，在IgA介导的免疫应答中起重要作用。它是一种高度糖基化的蛋白，具有6个潜在的n链糖基化位点。先前的报道显示，FcalphaR异常糖基化参与了一些疾病，包括人类免疫缺陷病毒感染、酒精性肝硬化和IgA肾病。在这项研究中，我们检测了n -糖基化对FcalphaR和IgA相互作用的影响。我们发现，tunicamycin在中国仓鼠卵巢（CHO）细胞中转染FcalphaR后，其n -糖基化缺失导致IgA结合增加。为了确定哪个糖基化位点与IgA结合增加有关，我们通过将天冬酰胺转变为谷氨酰胺，对每个n链糖基化位点进行了定点诱变。转染突变FcalphaR的CHO细胞IgA结合的流式细胞术分析显示，FcalphaR在单个N44、N120、N156、N165或N177位点的去糖基化不影响IgA结合，但在N58位点的去糖基化导致IgA结合显著增加。转染N58Q-FcalphaR的大鼠嗜碱性白血病细胞系RBL2H3也显示出类似的结果。此外，在神经氨酸酶处理后，还观察到去乙酰化的FcalphaR上IgA结合增加，而N58的去乙酰化是增加IgA结合的主要原因。这些数据表明N58位点的糖基化影响了FcalphaR与IgA的结合。
FcalphaR (CD89) is the Fc receptor for immunoglobulin A (IgA) and plays important roles in IgA-mediated immune responses. It is a heavily glycosylated protein with six potential N-linked glycosylation sites. Previous reports showed that abnormal glycosylation of FcalphaR was involved in some diseases, including human immunodeficiency virus infection, alcoholic liver cirrhosis and IgA nephropathy. In this study, we examined the effects of N-glycosylation on interaction between FcalphaR and IgA. We found that depletion of N-glycosylation of FcalphaR transfected in Chinese hamster ovary (CHO) cells by tunicamycin resulted in increased IgA binding. To identify which glycosylation site is responsible for increased IgA binding, we performed site-directed mutagenesis at each N-linked glycosylation site by changing asparagine to glutamine. Flow cytometry analysis of IgA binding to CHO cells transfected with mutated FcalphaR showed that deglycosylation of FcalphaR at individual N44, N120, N156, N165 or N177 site did not affect IgA binding but deglycosylation at N58 resulted in marked increase of IgA binding. Similar result was shown for N58Q-FcalphaR transfected RBL2H3, a rat basophilic leukemia cell line. Furthermore, increased IgA binding was also observed on desialylated FcalphaR after neuraminidase treatment and desialylation of N58 contributed most to the increased IgA binding. These data demonstrated that glycosylation at N58 site influenced FcalphaR binding to IgA.