Development of the predictor HERG fluorescence polarization assay using a membrane protein enrichment approach.
The life-threatening consequences of acquired, or drug-induced, long QT syndrome due to block of the human ether-a-go-go-related gene (hERG) channel are well appreciated and have been the cause of several drugs being removed from the market in recent years because of patient death. In the last decade, the propensity for block of the hERG channel by a diverse and expanding set of compounds has led to the requirement that all new drugs be tested for hERG channel block in a functional patch-clamp assay. Because of the need to identify potential hERG blockers early in the discovery process, radiometric hERG binding assays are preferred over patch-clamp assays for compound triage, because of relative advantages in speed and cost. Even so, these radiometric binding assays are laborious and require dedicated instrumentation and infrastructure to cope with the regulatory and safety issues associated with the use of radiation. To overcome these limitations, we developed a homogeneous, fluorescence polarization-based assay to identify and characterize the affinity of small molecules for the hERG channel and have demonstrated tight correlation with data obtained from either radioligand binding or patch-clamp assays. Key to the development of this assay was a cell line that expressed highly elevated levels of hERG protein, which was generated by coupling expression of the hERG channel to that of a selectable cell surface marker. A high-expressing clone was isolated by flow cytometry and used to generate membrane preparations that contained >50-fold the typical density of hERG channels measured by [(3)H]astemizole binding. This strategy enabled the Predictor (Invitrogen, Carlsbad, CA) hERG fluorescence polarization assay and should be useful in the development of other fluorescence polarization-based assays that use membrane proteins.
Piper
David R
DR
Invitrogen Discovery Sciences, Madison, WI 53719, USA. david.piper@invitrogen.com
Duff
Steve R
SR
Eliason
Hildegard C
HC
Frazee
W Jack
WJ
Frey
Elizabeth A
EA
Fuerstenau-Sharp
Maya
M
Jachec
Christine
C
Marks
Bryan D
BD
Pollok
Brian A
BA
Shekhani
Mohammed Saleh
MS
Thompson
David V
DV
Whitney
Pam
P
Vogel
Kurt W
KW
Hess
Stephen D
SD
D016827:CD8 Antigens / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D005434:Flow Cytometry; D005454:Fluorescence Polarization / Q000379:methods*; D005456:Fluorescent Dyes; D005818:Genetic Engineering; D006801:Humans; D007150:Immunohistochemistry; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology; D018408:Patch-Clamp Techniques; D011869:Radioligand Assay
D016827:CD8 Antigens; D051638:Ether-A-Go-Go Potassium Channels; D005456:Fluorescent Dyes; D008565:Membrane Proteins