Application of PatchXpress planar patch clamp technology to the screening of new drug candidates for cardiac KCNQ1/KCNE1 (I Ks) activity.
A cardiac safety concern for QT prolongation and potential for pro-arrhythmia exists due to inhibition of the cardiac slowly activating delayed rectifier potassium current, I(Ks). Selective inhibitors of I Ks have been shown to prolong the QT interval in animal models. On the other hand, I Ks has been considered as a target for anti-arrhythmic therapy due to certain biophysical and pharmacological properties and its expression pattern in the heart. Consequently, we have developed a method utilizing a human embryonic kidney (HEK)-293 cell line expressing KCNQ1/KCNE1 (genes that encode for the I Ks channel) as a model for screening of new compounds for I Ks activity. This study was designed (1) to establish and optimize the experimental conditions for measurement of I Ks using PatchXpress() 7000A (Molecular Devices Corporation, Sunnyvale, CA) and (2) to test the effects of I Ks inhibitors and compare the 50% inhibitory concentration (IC50) values determined with PatchXpress versus conventional patch clamp in order to validate the PatchXpress approach for higher-throughput I Ks screening. Biophysical properties of HEK/I Ks recorded with PatchXpress were similar to those recorded with conventional patch-clamp and reported in the literature. The IC50 values for I Ks block determined with PatchXpress correlated well with conventional patch-clamp values from HEK-293 cells as well as from native cardiac myocytes for the majority of compounds tested. Electrophysiological recording of I Ks expressed in HEK-293 cells with the PatchXpress is of acceptable quality for screening purposes. This approach can be utilized for functional prescreening of development compounds for I Ks inhibition either for optimizing lead anti-arrhythmic or other therapeutic candidates or to exclude compounds with the potential to prolong QT.
Trepakova
Elena S
ES
Merck Research Laboratories, West Point, PA 19486, USA. elena_trepakova@merck.com
Malik
Manish G
MG
Imredy
John P
JP
Penniman
Jacob R
JR
Dech
Spencer J
SJ
Salata
Joseph J
JJ
D000818:Animals; D016466:CHO Cells; D002317:Cardiovascular Agents / Q000494:pharmacology*; D002460:Cell Line; D002626:Chemistry, Pharmaceutical; D006224:Cricetinae; D003412:Cricetulus; D003627:Data Interpretation, Statistical; D004353:Drug Evaluation, Preclinical / Q000295:instrumentation*; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels / Q000187:drug effects; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D051657:KCNQ1 Potassium Channel / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects; D018408:Patch-Clamp Techniques / Q000295:instrumentation*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*
D002317:Cardiovascular Agents; D051638:Ether-A-Go-Go Potassium Channels; C489622:KCNE1 protein, human; C496884:KCNH1 protein, human; D051657:KCNQ1 Potassium Channel; D024642:Potassium Channels, Voltage-Gated