Blockade of HERG K+ channel by isoquinoline alkaloid neferine in the stable transfected HEK293 cells
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We studied the effects of isoquinoline alkaloid neferine (Nef) extracted from the seed embryo of Nelumbo nucifera Gaertn on Human ether-à-go-go-related gene (HERG) channels stably expressed in human embryonic kidney (HEK293) cells using whole-cell patch clamp technique, western blot analysis and immunofluorescence experiment. Nef induced a concentration-dependent decrease in current amplitude according to the voltage steps and tail currents of HERG with an IC50 of 7.419 μM (n H −0.5563). Nef shifted the activation curve in a significantly negative direction and accelerated recovery from inactivation and onset of inactivation, however, slowed deactivation. In addition, it had no significant influence on steady-state inactivation curve. Western blot and immunofluorescence results suggested Nef had no significant effect on the expression of HERG protein. In summary, Nef can block HERG K+ channels that functions by changing the channel activation and inactivation kinetics. Nef has no effect on the generation and trafficking of HERG protein. A blocked-off HERG channel was one mechanism of the anti-arrhythmic effects by Nef.
KeywordsNeferine HEK293 cells HERG channel Patch clamp Immunofluorescence Western blot
This work was supported by grants from the National Natural Science Foundation of China (no. 30572181), the National Natural Science Foundation of China (no. 30672644), the National Grand Fundamental Research 973 Program of China (no. 2007CB512000, 2007CB512006), and the Specialized Research Fund for the Doctoral Program of Higher Education (no. 20060226019).
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