Molecular basis of the differential sensitivity of nematode and mammalian muscle to the anthelmintic agent levamisole
Molecular basis of the differential sensitivity of nematode and mammalian muscle to the anthelmintic agent levamisole
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DOI：
10.1074/jbc.m403096200
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发表时间：
2004-08-27
影响因子：
4.8
通讯作者：
Bouzat, C
中科院分区：
文献类型：
--
作者：
Rayes, D;De Rosa, MAJ;Bouzat, C
左旋咪唑是一种驱虫剂，通过作为线虫肌肉尼古丁受体(AChR)的完全激动剂发挥其治疗作用。它在哺乳动物肌肉AChR中的作用迄今尚未阐明，尽管它在人类和牛身上广泛用作驱虫剂。通过单通道和宏观电流记录，我们研究了左旋咪唑与哺乳动物肌肉AChR的相互作用。左旋咪唑激活哺乳动物的AChRs。然而，单通道开口比乙酰胆碱(ACh)激活的通道更短，在高浓度时不会出现簇状。左旋咪唑诱发的峰电流约为ACh激活的3%。因此，驱虫剂是哺乳动物AChR的弱激动剂。左旋咪唑还能阻断AChR的开放通道。对BLOCK的表观亲和力(-70 mV时为190微米)与线虫AChR相似，表明通道激活动力学的差异决定了线虫和哺乳动物肌肉对驱虫剂的不同敏感性。为了确定这种不同敏感性的结构基础，我们针对脊椎动物和线虫之间不同的阿尔法亚单位中的残基进行了突变。用线虫AChR的同源谷氨酸取代保守的α-Gly-153显著增加了左旋咪唑激活通道的效果。通道活动发生在具有两种不同动力学模式的簇中。当激动剂为ACh或左旋咪唑时，高开放概率模式的动力学几乎相同。结论：α-Gly-153参与了左旋咪唑激活哺乳动物肌肉AChRs的低效作用。
Levamisole is an anthelmintic agent that exerts its therapeutic effect by acting as a full agonist of the nicotinic receptor (AChR) of nematode muscle. Its action at the mammalian muscle AChR has not been elucidated to date despite its wide use as an anthelmintic in humans and cattle. By single channel and macroscopic current recordings, we investigated the interaction of levamisole with the mammalian muscle AChR. Levamisole activates mammalian AChRs. However, single channel openings are briefer than those activated by acetylcholine (ACh) and do not appear in clusters at high concentrations. The peak current induced by levamisole is about 3% that activated by ACh. Thus, the anthelmintic acts as a weak agonist of the mammalian AChR. Levamisole also produces open channel blockade of the AChR. The apparent affinity for block (190 muM at -70 mV) is similar to that of the nematode AChR, suggesting that differences in channel activation kinetics govern the different sensitivity of nematode and mammalian muscle to anthelmintics. To identify the structural basis of this different sensitivity, we performed mutagenesis targeting residues in the alpha subunit that differ between vertebrates and nematodes. The replacement of the conserved alphaGly-153 with the homologous glutamic acid of nematode AChR significantly increases the efficacy of levamisole to activate channels. Channel activity takes place in clusters having two different kinetic modes. The kinetics of the high open probability mode are almost identical when the agonist is ACh or levamisole. It is concluded that alphaGly-153 is involved in the low efficacy of levamisole to activate mammalian muscle AChRs.