The antihistamine fexofenadine does not affect I(Kr) currents in a case report of drug-induced cardiac arrhythmia.
1. The human HERG gene encodes the cardiac repolarizing K(+) current I(Kr) and is genetically inactivated in inherited long QT syndrome 2 (LQTS2). The antihistamine terfenadine blocks HERG channels, and can cause QT prolongation and torsades de pointes, whereas its carboxylate fexofenadine lacks HERG blocking activity. 2. In the present study the ability of fexofenadine to block the K897T HERG channel variant was investigated. The underlying single nucleotide polymorphism (SNP) A2960C was identified in a patient reported to develop fexofenadine-associated LQTS. 3. K897T HERG channels produced wild-type-like currents in Xenopus oocytes. Even at a concentration of 100 micro M, fexofenadine did not inhibit wild-type or K897T HERG channels. Coexpression of wild-type and K897T HERG with the ss-subunit MiRP1, slightly changed current kinetics but did not change sensitivity to terfenadine and fexofenadine. 4. Western blot analysis and immunostaining of transiently transfected COS-7 cells demonstrated that overall expression level, glycosylation pattern and subcellular localization of K897T HERG is indistinguishable from wild-type HERG protein, and not altered in the presence of 1 micro M fexofenadine. 5. We provide the first functional characterization of the K897T HERG variant. We demonstrated that K897T HERG is similar to wild-type HERG, and is insensitive to fexofenadine. Although the polymorphism changes PKA and PKC phosphorylation sites, regulation of K897T HERG by these kinases is not altered. 6. Our results strongly indicate that QT lengthening and cardiac arrhythmia in the reported case of drug-induced LQT are not due to the K897T exchange or to an inhibitory effect of fexofenadine on cardiac I(Kr) currents. British Journal of
Scherer
Constanze R
CR
Aventis Pharma Deutschland GmbH, Cardiovascular Diseases, 65926 Frankfurt am Main, Germany.
Lerche
Christian
C
Decher
Niels
N
Dennis
Adrienne T
AT
Maier
Patrick
P
Ficker
Eckhard
E
Busch
Andreas E
AE
Wollnik
Bernd
B
Steinmeyer
Klaus
K
D000368:Aged; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000235:genetics* / Q000503:physiopathology; D001483:Base Sequence; D015153:Blotting, Western; D019556:COS Cells; D027682:Cation Transport Proteins; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D005838:Genotype; D006634:Histamine H1 Antagonists / Q000009:adverse effects / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D018807:Polymorphism, Single-Stranded Conformational; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011537:Pruritus / Q000188:drug therapy; D017386:Sequence Homology, Amino Acid; D016593:Terfenadine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000627:therapeutic use; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG
D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006634:Histamine H1 Antagonists; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; C059983:potassium channel protein I(sk); D005576:Colforsin; D016593:Terfenadine; D004247:DNA; C093230:fexofenadine; D013755:Tetradecanoylphorbol Acetate