Department of Biochemistry, Sanger Building, University of Cambridge, Cambridge, United Kingdom.
Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge, United Kingdom.
J Med Virol. 2022 Sep;94(9):4181-4192. doi: 10.1002/jmv.27845. Epub 2022 Jun 7.
Cleavage of the severe respiratory syndrome coronavirus-2 (SARS-CoV-2) spike protein has been demonstrated to contribute to viral-cell fusion and syncytia formation. Studies have shown that variants of concern (VOC) and variants of interest (VOI) show differing membrane fusion capacity. Mutations near cleavage motifs, such as the S1/S2 and S2' sites, may alter interactions with host proteases and, thus, the potential for fusion. The biochemical basis for the differences in interactions with host proteases for the VOC/VOI spike proteins has not yet been explored. Using sequence and structure-based bioinformatics, mutations near the VOC/VOI spike protein cleavage sites were inspected for their structural effects. All mutations found at the S1/S2 sites were predicted to increase affinity to the furin protease but not TMPRSS2. Mutations at the spike residue P681 in several strains, such P681R in the Delta strain, resulted in the disruption of a proline-directed kinase phosphorylation motif at the S1/S2 site, which may lessen the impact of phosphorylation for these variants. However, the unique N679K mutation in the Omicron strain was found to increase the propensity for O-linked glycosylation at the S1/S2 cleavage site, which may prevent recognition by proteases. Such glycosylation in the Omicron strain may hinder entry at the cell surface and, thus, decrease syncytia formation and induce cell entry through the endocytic pathway as has been shown in previous studies. Further experimental work is needed to confirm the effect of mutations and posttranslational modifications on SARS-CoV-2 spike protein cleavage sites.
严重急性呼吸综合征冠状病毒 2 型（SARS-CoV-2）刺突蛋白的裂解已被证明有助于病毒细胞融合和合胞体形成。研究表明，关注变体（VOC）和感兴趣变体（VOI）显示出不同的膜融合能力。靠近切割基序的突变，如 S1/S2 和 S2'位点，可能改变与宿主蛋白酶的相互作用，从而改变融合的潜力。VOC/VOI 刺突蛋白与宿主蛋白酶相互作用的差异的生化基础尚未得到探索。本研究使用基于序列和结构的生物信息学方法，检查了 VOC/VOI 刺突蛋白切割位点附近的突变对结构的影响。在 S1/S2 位点发现的所有突变都被预测为增加与弗林蛋白酶的亲和力，但不增加与 TMPRSS2 的亲和力。在几种毒株中，如在 Delta 株中的 P681R，刺突残基 P681 处的突变导致 S1/S2 位点的一个脯氨酸定向激酶磷酸化基序被破坏，这可能会减轻这些变体的磷酸化的影响。然而，在奥密克戎株中发现的独特的 N679K 突变增加了 S1/S2 切割位点的 O 连接糖基化倾向，这可能会阻止蛋白酶的识别。奥密克戎株中的这种糖基化可能会阻碍细胞表面的进入，从而减少合胞体的形成，并通过内吞途径诱导细胞进入，正如之前的研究所示。需要进一步的实验工作来确认突变和翻译后修饰对 SARS-CoV-2 刺突蛋白切割位点的影响。
