Direct block of hERG potassium channels by the protein kinase C inhibitor bisindolylmaleimide I (GF109203X).
OBJECTIVE
The human ether-a-go-go-related gene (hERG) encodes the rapid component of the cardiac repolarizing delayed rectifier potassium current, I(Kr). The direct interaction of the commonly used protein kinase C (PKC) inhibitor bisindolylmaleimide I (BIM I) with hERG, KvLQT1/minK, and I(Kr) currents was investigated in this study.


METHODS
hERG and KvLQT1/minK channels were heterologously expressed in Xenopus laevis oocytes, and currents were measured using the two-microelectrode voltage clamp technique. In addition, hERG currents in stably transfected human embryonic kidney (HEK 293) cells, native I(Kr) currents and action potentials in isolated guinea pig ventricular cardiomyocytes were recorded using whole-cell patch clamp electrophysiology.


RESULTS
Bisindolylmaleimide I blocked hERG currents in HEK 293 cells and Xenopus oocytes in a concentration-dependent manner with IC(50) values of 1.0 and 13.2 muM, respectively. hERG channels were primarily blocked in the open state in a frequency-independent manner. Analysis of the voltage-dependence of block revealed a reduction of inhibition at positive membrane potentials. BIM I caused a shift of -20.3 mV in the voltage-dependence of inactivation. The point mutations tyrosine 652 alanine (Y652A) and phenylalanine 656 alanine (F656A) attenuated hERG current blockade, indicating that BIM I binds to a common drug receptor within the pore region. KvLQT1/minK currents were not significantly altered by BIM I. Finally, 1 muM BIM I reduced native I(Kr) currents by 69.2% and lead to action potential prolongation.


CONCLUSIONS
In summary, PKC-independent effects have to be carefully considered when using BIM I as PKC inhibitor in experimental models involving hERG channels and I(Kr) currents.
Thomas
Dierk
D
Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany. Dierk_Thomas@med.uni-heidelberg.de
Hammerling
Bettina C
BC
Wimmer
Anna-Britt
AB
Wu
Kezhong
K
Ficker
Eckhard
E
Kuryshev
Yuri A
YA
Scherer
Daniel
D
Kiehn
Johann
J
Katus
Hugo A
HA
Schoels
Wolfgang
W
Karle
Christoph A
CA
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D027682:Cation Transport Proteins / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D007668:Kidney / Q000196:embryology; D008301:Maleimides / Q000494:pharmacology*; D009154:Mutation; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009865:Oocytes; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000009:adverse effects*; D014982:Xenopus laevis
D027682:Cation Transport Proteins; D051638:Ether-A-Go-Go Potassium Channels; D007211:Indoles; C092509:KCNH6 protein, human; D008301:Maleimides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C; C070515:bisindolylmaleimide I