Effects of allelic variations in the human myxovirus resistance protein A on its antiviral activity
Effects of allelic variations in the human myxovirus resistance protein A on its antiviral activity
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DOI：
10.1074/jbc.m117.812784
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发表时间：
2018-03-02
影响因子：
4.8
通讯作者：
Kochs, Georg
中科院分区：
文献类型：
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作者：
Graf, Laura;Dick, Alexej;Kochs, Georg
只有少数感染季节性甲型流感病毒的患者表现出严重或致命的感染结果，但这种流感易感性个体间差异的原因尚不清楚。为了进一步了解这种变异背后的分子机制，我们研究了编码流感限制因子MxA的黏液病毒抗性1 （MX1）基因的自然等位基因变异。干扰素诱导的动力蛋白样GTPase由一个n端GTPase结构域、一个束信号元件和一个负责寡聚化和病毒靶标识别的c端柄组成。我们使用在线数据库搜索MX1基因的变异。采用体外方法，我们发现GTPase结构域的非同义变异导致抗病毒和酶活性的丧失。此外，我们发现这些氨基酸取代破坏了刺激GTP水解所需的GTP酶结构域二聚化的界面。茎秆的变异是中性的或轻微增强或减弱MxA抗病毒功能。值得注意的是，另外两种茎变异体改变了MxA的抗病毒特异性。导致抗病毒活性丧失的变异仅在杂合携带者中发现。有趣的是，失活的茎变异体以显性阴性的方式阻断了WT MxA的抗病毒活性，这表明杂合子表型上是MxA阴性的。相比之下，gtpase缺陷变体没有显示出显性负效应，这表明杂合携带者应该不受影响。我们的研究结果表明，人类MX1基因中自然发生的突变可以影响MxA功能，这可能解释了人类流感病毒易感性的个体差异。
Only a minority of patients infected with seasonal influenza A viruses exhibit a severe or fatal outcome of infection, but the reasons for this inter-individual variability in influenza susceptibility are unclear. To gain further insights into the molecular mechanisms underlying this variability, we investigated naturally occurring allelic variations of the myxovirus resistance 1 (MX1) gene coding for the influenza restriction factor MxA. The interferon-induced dynamin-like GTPase consists of an N-terminal GTPase domain, a bundle signaling element, and a C-terminal stalk responsible for oligomerization and viral target recognition. We used online databases to search for variations in the MX1 gene. Deploying in vitro approaches, we found that non-synonymous variations in the GTPase domain cause the loss of antiviral and enzymatic activities. Furthermore, we showed that these amino acid substitutions disrupt the interface for GTPase domain dimerization required for the stimulation of GTP hydrolysis. Variations in the stalk were neutral or slightly enhanced or abolished MxA antiviral function. Remarkably, two other stalk variants altered MxA's antiviral specificity. Variations causing the loss of antiviral activity were found only in heterozygous carriers. Interestingly, the inactive stalk variants blocked the antiviral activity of WT MxA in a dominant-negative way, suggesting that heterozygotes are phenotypically MxA-negative. In contrast, the GTPase-deficient variants showed no dominant-negative effect, indicating that heterozygous carriers should remain unaffected. Our results demonstrate that naturally occurring mutations in the human MX1 gene can influence MxA function, which may explain individual variations in influenza virus susceptibility in the human population.