Activities of α-conotoxin TxID isomers on human nicotinic acetylcholine receptors / 中国药科大学学报

@#To investigate activities of three isomers of α-conotoxin TxID on human α3β4 and α6/α3β4 nicotinic acetylcholine receptors(nAChRs). The three isomers of α-conotoxin TxID were synthesized using solid phase Fmoc chemistry and fully folded by two-step oxidations. Human α3β4 and α6/α3β4 nAChRs were expressed in oocytes of Xenopus laevis, which were used for bioassay of the three isomers, including inhibition and washout reversibility. There were obvious differences between the inhibition potency of each isomers at human α3β4 and α6/α3β4 nAChRs. The blocking was reversible and washout rapidly. The most potent isomer is the globular form with an IC50 of 9. 3 nmol/L on human α3β4 and α6/α3β4 nAChRs respectively. The 2nd potent isomer was the ribbon form with much less potency, which had an IC50 of > 5 μmol/L. The bead isomer had little or no block on human α3β4 and α6/α3β4 nAChRs with an IC50 of > 10 μmol/L. The three isomers of α-conotoxin TxID were synthesized successfully with two pairs of desired disulfide bond. Inhibition activities of the 3 isomers on human α3β4 and α6/α3β4 nAChRs were obtained respectively, which would be basis for new marine drug development of α-conotoxin TxID.

Sensitivity of α-conotoxin TxID on stoichiometry of α3β4 nicotinic acetylcholine receptors / 中国药学杂志

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 nAChR 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.