Widespread sequence variations in VAMP1 across vertebrates suggest a potential selective pressure from botulinum neurotoxins.
Widespread sequence variations in VAMP1 across vertebrates suggest a potential selective pressure from botulinum neurotoxins.
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DOI：
10.1371/journal.ppat.1004177
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发表时间：
2014-07
期刊：
影响因子：
6.7
通讯作者：
Dong M
中科院分区：
文献类型：
--
作者：
Peng L;Adler M;Demogines A;Borrell A;Liu H;Tao L;Tepp WH;Zhang SC;Johnson EA;Sawyer SL;Dong M
肉毒杆菌神经毒素（BoNT/A-G）是已知最有效的毒素，通过切割突触囊泡胞外分泌所需的三种SNARE蛋白起作用。先前对bont的研究通常使用在大脑中表达的主要SNARE同源物（VAMP2， syntaxin 1和SNAP-25）。然而，bont以周围运动神经元为目标，通过麻痹膈肌等呼吸肌而导致死亡。在这里，我们报告了VAMP1，而不是VAMP2，是在成年啮齿动物膈运动神经末梢和分化的人类运动神经元中主要表达的SNARE同源基因。与高度保守的VAMP2相反，VAMP1的bont抗性变异在脊椎动物中广泛存在。特别是，我们在大鼠中发现了VAMP1的48位多态性，这使得VAMP1对BoNT/D具有抗性（I48）或敏感性（M48）。利用这一发现，我们发现与VAMP1中含有I48的大鼠膈相比，VAMP1中含有M48的大鼠膈对BoNT/D不敏感。这种独特的种内比较确定了VAMP1是横膈膜运动神经末梢的生理毒素靶点，并表明VAMP1对BoNTs的抗性可能是物种对BoNTs成员不敏感的基础。人类VAMP1始终含有I48，这可能解释了为什么人类对BoNT/D不敏感。最后，我们报告了VAMP1的残基48在17种密切相关的灵长类动物中在M和I之间经常变化，这表明bont成员对脊椎动物的抗性存在潜在的选择压力。肉毒杆菌神经毒素（BoNTs）以外周运动神经元为目标，通过切割SNARE蛋白起作用，而SNARE蛋白是神经末梢释放神经递质所必需的。SNARE蛋白存在于多个同源物中，在密切相关的SNARE同源物如VAMP1和VAMP2中，很难确定哪一个是运动神经末梢生理相关的毒素靶点。在这里，我们报告说，与高度保守的VAMP2相反，VAMP1中赋予bont抗性的序列变异在脊椎动物中广泛存在。值得一提的是，VAMP1的残基48在BoNT/ d敏感残基M和BoNT/ d抗性残基I之间存在多态性。利用这一发现，我们进行了种内比较，结果表明，与M48相比，VAMP1中I48的大鼠膈肌运动神经末梢对BoNT/D不敏感。由于VAMP2在大鼠中是保守的，这些数据表明VAMP1是运动神经元中生理相关的毒素靶点。有趣的是，人类VAMP1编码BoNT/D抗性残基I48，这可能解释了为什么人类对BoNT/D不敏感。最后，我们发现VAMP1的残基48在17种灵长类动物中频繁地在M和I之间切换，这表明BoNT/D对灵长类动物的抗性有潜在的选择压力。
Botulinum neurotoxins (BoNT/A-G), the most potent toxins known, act by cleaving three SNARE proteins required for synaptic vesicle exocytosis. Previous studies on BoNTs have generally utilized the major SNARE homologues expressed in brain (VAMP2, syntaxin 1, and SNAP-25). However, BoNTs target peripheral motor neurons and cause death by paralyzing respiratory muscles such as the diaphragm. Here we report that VAMP1, but not VAMP2, is the SNARE homologue predominantly expressed in adult rodent diaphragm motor nerve terminals and in differentiated human motor neurons. In contrast to the highly conserved VAMP2, BoNT-resistant variations in VAMP1 are widespread across vertebrates. In particular, we identified a polymorphism at position 48 of VAMP1 in rats, which renders VAMP1 either resistant (I48) or sensitive (M48) to BoNT/D. Taking advantage of this finding, we showed that rat diaphragms with I48 in VAMP1 are insensitive to BoNT/D compared to rat diaphragms with M48 in VAMP1. This unique intra-species comparison establishes VAMP1 as a physiological toxin target in diaphragm motor nerve terminals, and demonstrates that the resistance of VAMP1 to BoNTs can underlie the insensitivity of a species to members of BoNTs. Consistently, human VAMP1 contains I48, which may explain why humans are insensitive to BoNT/D. Finally, we report that residue 48 of VAMP1 varies frequently between M and I across seventeen closely related primate species, suggesting a potential selective pressure from members of BoNTs for resistance in vertebrates. Botulinum neurotoxins (BoNTs) target peripheral motor neurons and act by cleaving SNARE proteins, which are essential for neurotransmitter release from nerve terminals. SNARE proteins occur in multiple homologues and it has been difficult to determine which one is the physiologically relevant toxin target in motor nerve terminals among closely related SNARE homologues such as VAMP1 and VAMP2. Here we report that, in contrast to the highly conserved VAMP2, sequence variations in VAMP1 that confer resistance to BoNTs are widespread across vertebrates. In particular, residue 48 of VAMP1 is polymorphic between BoNT/D-sensitive residue M and BoNT/D-resistant residue I in rats. Taking advantage of this finding, we carried out an intra-species comparison, which showed that diaphragm motor nerve terminals from rats with I48 in VAMP1 were insensitive to BoNT/D as compared to those with M48. Since VAMP2 is conserved in rats, these data demonstrate that VAMP1 is the physiologically relevant toxin target in motor neurons. Interestingly, human VAMP1 encodes the BoNT/D-resistant residue I48, which may explain why humans are insensitive to BoNT/D. Finally, we found that residue 48 of VAMP1 switches frequently between M and I among 17 primate species, suggesting a potential selective pressure from BoNT/D for resistance in primates.
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