TY - JOUR
T1 - Coexistence of hERG current block and disruption of protein trafficking in ketoconazole-induced long QT syndrome
AU - Takemasa, H.
AU - Nagatomo, T.
AU - Abe, H.
AU - Kawakami, K.
AU - Igarashi, T.
AU - Tsurugi, T.
AU - Kabashima, N.
AU - Tamura, M.
AU - Okazaki, M.
AU - Delisle, B. P.
AU - January, C. T.
AU - Otsuji, Y.
PY - 2008/2
Y1 - 2008/2
N2 - Background and purpose: Many drugs associated with acquired long QT syndrome (LQTS) directly block human ether-a-go-go-related gene (hERG) K + channels. Recently, disrupted trafficking of the hERG channel protein was proposed as a new mechanism underlying LQTS, but whether this defect coexists with the hERG current block remains unclear. This study investigated how ketoconazole, a direct hERG current inhibitor, affects the trafficking of hERG channel protein. Experimental approach: Wild-type hERG and SCN5A/hNa v 1.5 Na + channels or the Y652A and F656C mutated forms of the hERG were stably expressed in HEK293 cells. The K + and Na + currents were recorded in these cells by using the whole-cell patch-clamp technique (23°C). Protein trafficking of the hERG was evaluated by Western blot analysis and flow cytometry. Key results: Ketoconazole directly blocked the hERG channel current and reduced the amount of hERG channel protein trafficked to the cell surface in a concentration-dependent manner. Current density of the hERG channels but not of the hNa v 1.5 channels was reduced after 48 h of incubation with ketoconazole, with preservation of the acute direct effect on hERG current. Mutations in drug-binding sites (F656C or Y652A) of the hERG channel significantly attenuated the hERG current blockade by ketoconazole, but did not affect the disruption of trafficking. Conclusions and implications: Our findings indicate that ketoconazole might cause acquired LQTS via a direct inhibition of current through the hERG channel and by disrupting hERG protein trafficking within therapeutic concentrations. These findings should be considered when evaluating new drugs.
AB - Background and purpose: Many drugs associated with acquired long QT syndrome (LQTS) directly block human ether-a-go-go-related gene (hERG) K + channels. Recently, disrupted trafficking of the hERG channel protein was proposed as a new mechanism underlying LQTS, but whether this defect coexists with the hERG current block remains unclear. This study investigated how ketoconazole, a direct hERG current inhibitor, affects the trafficking of hERG channel protein. Experimental approach: Wild-type hERG and SCN5A/hNa v 1.5 Na + channels or the Y652A and F656C mutated forms of the hERG were stably expressed in HEK293 cells. The K + and Na + currents were recorded in these cells by using the whole-cell patch-clamp technique (23°C). Protein trafficking of the hERG was evaluated by Western blot analysis and flow cytometry. Key results: Ketoconazole directly blocked the hERG channel current and reduced the amount of hERG channel protein trafficked to the cell surface in a concentration-dependent manner. Current density of the hERG channels but not of the hNa v 1.5 channels was reduced after 48 h of incubation with ketoconazole, with preservation of the acute direct effect on hERG current. Mutations in drug-binding sites (F656C or Y652A) of the hERG channel significantly attenuated the hERG current blockade by ketoconazole, but did not affect the disruption of trafficking. Conclusions and implications: Our findings indicate that ketoconazole might cause acquired LQTS via a direct inhibition of current through the hERG channel and by disrupting hERG protein trafficking within therapeutic concentrations. These findings should be considered when evaluating new drugs.
KW - Acquired long QT syndrome
KW - K channels
KW - Ketoconazole
KW - hERG channel
KW - hERG protein trafficking
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UR - http://www.scopus.com/inward/citedby.url?scp=38849139779&partnerID=8YFLogxK
U2 - 10.1038/sj.bjp.0707537
DO - 10.1038/sj.bjp.0707537
M3 - Article
C2 - 17965736
AN - SCOPUS:38849139779
SN - 0007-1188
VL - 153
SP - 439
EP - 447
JO - British Journal of Pharmacology
JF - British Journal of Pharmacology
IS - 3
ER -