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Molecular determinants of inactivation and dofetilide block in ether a-go-go (EAG) channels and EAG-related K(+) channels.
Mol Pharmacol. 2001 Dec; 60(6):1343-8.MP

Abstract

The major subunit of the cardiac delayed rectifier current I(Kr) is encoded by the human ether a-go-go related gene (HERG). HERG/I(Kr) channels are blocked selectively by class III antiarrhythmic methanesulfonanilide drugs such as dofetilide. The binding site for methanesulfonanilides is believed to be similar for nonantiarrhythmic drugs such as antihistamines, antibiotics, and antipsychotics. To gain further insight into the binding site, we examined the minimal structural changes necessary to transform low-affinity binding of dofetilide by the related bovine ether a-go-go channel bEAG to high-affinity binding of HERG. Previously, it was shown that high-affinity binding in HERG required intact C-type inactivation; the bovine ether a-go-go K(+) channel (bEAG), unlike HERG, is noninactivating. Therefore, we introduced C-type inactivation into noninactivating bEAG using site-directed mutagenesis. Two point mutations in the pore region, T432S and A443S, were sufficient to produce C-type inactivation. Low concentrations of dofetilide produced block of bEAG T432S/A443S; unlike HERG, block was almost irreversible. Substitution of an additional amino acid in transmembrane domain S6 made the block reversible. Dofetilide blocked the triply mutated bEAG T432S/A443S/A453S with an IC(50) value of 1.1 microM. The blocking potency was 30-fold greater than bEAG WT and about one third that of HERG WT. We conclude that high affinity methanesulfonanilide binding to HERG channels is strongly dependent on C-type inactivation.

Authors+Show Affiliations

Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44109-1998, USA. eficker@metrohealth.orgNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

11723241

Citation

Ficker, E, et al. "Molecular Determinants of Inactivation and Dofetilide Block in Ether A-go-go (EAG) Channels and EAG-related K(+) Channels." Molecular Pharmacology, vol. 60, no. 6, 2001, pp. 1343-8.
Ficker E, Jarolimek W, Brown AM. Molecular determinants of inactivation and dofetilide block in ether a-go-go (EAG) channels and EAG-related K(+) channels. Mol Pharmacol. 2001;60(6):1343-8.
Ficker, E., Jarolimek, W., & Brown, A. M. (2001). Molecular determinants of inactivation and dofetilide block in ether a-go-go (EAG) channels and EAG-related K(+) channels. Molecular Pharmacology, 60(6), 1343-8.
Ficker E, Jarolimek W, Brown AM. Molecular Determinants of Inactivation and Dofetilide Block in Ether A-go-go (EAG) Channels and EAG-related K(+) Channels. Mol Pharmacol. 2001;60(6):1343-8. PubMed PMID: 11723241.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Molecular determinants of inactivation and dofetilide block in ether a-go-go (EAG) channels and EAG-related K(+) channels. AU - Ficker,E, AU - Jarolimek,W, AU - Brown,A M, PY - 2001/11/28/pubmed PY - 2002/1/5/medline PY - 2001/11/28/entrez SP - 1343 EP - 8 JF - Molecular pharmacology JO - Mol. Pharmacol. VL - 60 IS - 6 N2 - The major subunit of the cardiac delayed rectifier current I(Kr) is encoded by the human ether a-go-go related gene (HERG). HERG/I(Kr) channels are blocked selectively by class III antiarrhythmic methanesulfonanilide drugs such as dofetilide. The binding site for methanesulfonanilides is believed to be similar for nonantiarrhythmic drugs such as antihistamines, antibiotics, and antipsychotics. To gain further insight into the binding site, we examined the minimal structural changes necessary to transform low-affinity binding of dofetilide by the related bovine ether a-go-go channel bEAG to high-affinity binding of HERG. Previously, it was shown that high-affinity binding in HERG required intact C-type inactivation; the bovine ether a-go-go K(+) channel (bEAG), unlike HERG, is noninactivating. Therefore, we introduced C-type inactivation into noninactivating bEAG using site-directed mutagenesis. Two point mutations in the pore region, T432S and A443S, were sufficient to produce C-type inactivation. Low concentrations of dofetilide produced block of bEAG T432S/A443S; unlike HERG, block was almost irreversible. Substitution of an additional amino acid in transmembrane domain S6 made the block reversible. Dofetilide blocked the triply mutated bEAG T432S/A443S/A453S with an IC(50) value of 1.1 microM. The blocking potency was 30-fold greater than bEAG WT and about one third that of HERG WT. We conclude that high affinity methanesulfonanilide binding to HERG channels is strongly dependent on C-type inactivation. SN - 0026-895X UR - https://www.unboundmedicine.com/medline/citation/11723241/Molecular_determinants_of_inactivation_and_dofetilide_block_in_ether_a_go_go__EAG__channels_and_EAG_related_K_+__channels_ L2 - http://molpharm.aspetjournals.org/cgi/pmidlookup?view=long&pmid=11723241 DB - PRIME DP - Unbound Medicine ER -