α-芋螺毒素TxID对亚基不同配比α3β4乙酰胆碱受体的敏感性研究

Sensitivity of α-Conotoxin TxID on Stoichiometry of α3β4 Nicotinic Acetylcholine Receptors

目的研究α-芋螺毒素TxID对具有不同亚基配比组成的大鼠α3β4乙酰胆碱受体(nAChRs)的阻断活性敏感性。方法利用非洲爪蟾卵母细胞表达大鼠α3β4乙酰胆碱受体亚型,将其亚基α3和β4的cRNA分别以3种不同比例,即1∶1、1∶10或10∶1注射到非洲爪蟾卵母细胞中进行表达,形成不同亚基配比的α3β4受体,分别检测和比较α-芋螺毒素TxID对这些不同亚基配比受体的阻断活性。结果成功表达了α3和β4亚基的3个不同配比的受体,且α-芋螺毒素TxID对它们的敏感性有较大差异,与常规的1∶1α3β4乙酰胆碱受体相比,1∶10α3β4乙酰胆碱受体对TxID的敏感度与之接近,其活性差异在2倍以内,而10∶1α3β4乙酰胆碱受体对TxID的敏感度显著下降,其活性差异超过了5倍。结论α-芋螺毒素TxID对不同亚基配比的α3β4乙酰胆碱受体有不同的敏感性,并能反应该受体的α和β亚基不同的组成方式,这对于研究α3β4乙酰胆碱受体的结构和生理功能具有很重要的指导意义。

OBJECTIVE To interrogate differential sensitivity of α-conotoxin TxID on stoichiometry of α3β4 nicotinic acetylcholine receptors（ nAChRs）. METHODS Oocytes of Xenopus laevis were used to express rat α3β4 nAChRs with different stoichiometries by altering α3∶ β4 RNA injection ratios of 1∶ 1,1∶ 10 or 10∶ 1. Sensitivity of α-conotoxin TxID on these different stoichiometry receptors were evaluated and compared. RESULTS The three stoichiometry receptors of α3β4 nAChRs were expressed in oocytes successfully.α-Conotoxin TxID showed differential sensitivity on α3β4 n AChR stoichiometries. Inhibition of 1∶ 10 injection ratio by TxID was similar with regular 1∶ 1 α3β4 nAChRs within 2-fold difference. While potency of 10 ∶ 1 injection ratio by TxID decreased 5-fold significantly comparing with 1∶ 1 α3β4 nAChRs. CONCLUSION α-Conotoxin TxID exhibits distinct sensitivity on different stoichiometry of α3β4 nAChRs,which could reflecting different stoichiometries of α and β subunits. The results would be helpful for elucidation of structure and physiology function of α3β4 nAChRs.