Antagonistic Activity of α-Conotoxin TxIB Isomers on Rat and Human α6 /α3β2β3 Nicotinic Acetylcholine Receptors / 中国药学杂志

OBJECTIVE: To investigate antagonistic activities of three isomers of α-conotoxin TxIB on rat and human α6 /α3β2β3 nicotinic acetylcholine receptors (nAChRs). METHODS: Three disulfide bond isomers were synthesized using Fmoc chemistry, which were identified by ultra performance liquid chromatography (UPLC)and confirmed by MALDI-TOF mass spectrometry. Rat and human α6/α3β2β3 nAChRs were expressed in oocytes of Xenopus laevis, which were used to test the antagonistic abilities of the 3 isomers. RESULTS: The three isomers of α-conotoxin TxIB were synthesized successfully. The retention time of each isomer of α-conotoxin TxIB was different each other significantly. The observed molecular masses of three isomers were the same, which were consistent with their theoretical molecular mass. Their hydrophilicity orders were globular > ribbon > bead. Both rat and human α6/α3β2β3 nAChRs were expressed in oocytes well. Inhibition of three isomers of α-conotoxin TxIB on rat and human α6 /α3β2β3 nAChRs were evaluated respectively. Among the three isomers of TxIB, the activity of the globular isomer was the most potent one, which had almost same activity at rat and human α6/α3β2β3 nAChRs with corresponding IC50 of 28.2 and 32.0 nmol·L-1 respectively. However, the other two isomers, ribbon and bead isomers displayed little antagonistic effect on both rat and human α6/α3β2β3 nAChRs only with an IC50 of > 10 μmol·L-1. CONCLUSION: The synthesized globular isomer of α-conotoxin TxIB in this work has a high selectivity and potent antagonistic activity on rat and human α6/α3β2β3 nAChRs, which would be helpful for its new drug development.

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.