Influenza Virus Neuraminidases with Reduced Enzymatic Activity That Avidly Bind Sialic Acid Receptors
Influenza Virus Neuraminidases with Reduced Enzymatic Activity That Avidly Bind Sialic Acid Receptors
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DOI：
10.1128/jvi.01426-12
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发表时间：
2012-12-01
影响因子：
5.4
通讯作者：
Wilson, Ian A.
中科院分区：
文献类型：
--
作者：
Zhu, Xueyong;McBride, Ryan;Wilson, Ian A.
流感病毒神经氨酸酶（NA）从血凝素（HA）细胞受体上裂解唾液酸，使后代能够逃离受感染的细胞。然而，最近人类 H3N2 病毒的 NA 变体 (D151G) 也被报道能够结合红细胞上的受体，但这些受体的性质以及突变对 NA 活性的影响尚未确定。在这里，我们比较了来自 A/Tanzania/205/2010 的人 H3N2 NA 及其 D151G 突变体的功能和结构特性，该突变体支持 HA 独立受体结合。虽然野生型 NA 可以有效地将唾液酸从 α 2-6 连接聚糖和 α 2-3 连接聚糖上裂解下来，但突变体对两种类型的唾液酸苷的酶活性均显着降低。相反，虽然野生型 NA 未显示出与唾液酸苷的可检测结合，但 D151G NA 对 α 2-3 唾液酸苷表现出广泛特异性的强烈结合。 D151G NA 结合 3' 唾液酸乳糖胺 (3'-SLN) 和 6'-SLN 唾液酸苷，平衡解离常数 (K-D) 值分别为 30.0 μM 和 645 μM，这对应于比 HA 对这些聚糖的相应亲和力（低 mM）高得多的亲和力。野生型和突变型 NA 的晶体结构通过专门损害糖苷键水解步骤揭示了活性位点中聚糖结合的结构基础。通过将 D151G 突变引入三个 N1 NA 和一个 N2 NA，进一步探讨了 D151 在流感病毒 NA 中的一般意义，这些突变均表现出酶活性降低并优先与 α 2-3 唾液酸苷结合。由于 NA 的酶活性和结合活性并未得到常规评估，因此 NA 受体结合对流感病毒生物学贡献的潜力可能被低估。
Influenza virus neuraminidase (NA) cleaves off sialic acid from cellular receptors of hemagglutinin (HA) to enable progeny escape from infected cells. However, NA variants (D151G) of recent human H3N2 viruses have also been reported to bind receptors on red blood cells, but the nature of these receptors and the effect of the mutation on NA activity were not established. Here, we compare the functional and structural properties of a human H3N2 NA from A/Tanzania/205/2010 and its D151G mutant, which supports HA-independent receptor binding. While the wild-type NA efficiently cleaves sialic acid from both alpha 2-6- and alpha 2-3-linked glycans, the mutant exhibits much reduced enzymatic activity toward both types of sialosides. Conversely, while wild-type NA shows no detectable binding to sialosides, the D151G NA exhibits avid binding with broad specificity toward alpha 2-3 sialosides. D151G NA binds the 3' sialyllactosamine (3'-SLN) and 6'-SLN sialosides with equilibrium dissociation constant (K-D) values of 30.0 mu M and 645 mu M, respectively, which correspond to much higher affinities than the corresponding affinities (low mM) of HA to these glycans. Crystal structures of wild-type and mutant NAs reveal the structural basis for glycan binding in the active site by exclusively impairing the glycosidic bond hydrolysis step. The general significance of D151 among influenza virus NAs was further explored by introducing the D151G mutation into three N1 NAs and one N2 NA, which all exhibited reduced enzymatic activity and preferential binding to alpha 2-3 sialosides. Since the enzymatic and binding activities of NAs are not routinely assessed, the potential for NA receptor binding to contribute to influenza virus biology may be underappreciated.