The molecular basis of the specificity of action of K(ATP) channel openers.
K(ATP) channels incorporate a regulatory subunit of the ATP-binding cassette (ABC) transporter family, the sulfonylurea receptor (SUR), which defines their pharmacology. The therapeutically important K(+) channel openers (e.g. pinacidil, cromakalim, nicorandil) act specifically on the SUR2 muscle isoforms but, except for diazoxide, remain ineffective on the SUR1 neuronal/pancreatic isoform. This SUR1/2 dichotomy underpinned a chimeric strategy designed to identify the structural determinants of opener action, which led to a minimal set of two residues within the last transmembrane helix of SUR. Transfer of either residue from SUR2A to SUR1 conferred opener sensitivity to SUR1, while the reverse operation abolished SUR2A sensitivity. It is therefore likely that these residues form part of the site of interaction of openers with the channel. Thus, openers would target a region that, in other ABC transporters, is known to be tightly involved with the binding of substrates and other ligands. This first glimpse of the site of action of pharmacological openers should permit rapid progress towards understanding the structural determinants of their affinity and specificity.
Moreau
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C
CEA, DBMS, Biophysique Moléculaire et Cellulaire (UMR CNRS/UJF/CEA 5090), 17 Rue des Martyrs, 38054 Grenoble, France. vivaudou@cea.fr
Jacquet
H
H
Prost
A L
AL
D'hahan
N
N
Vivaudou
M
M
D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D006224:Cricetinae; D019806:Cromakalim / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000502:physiology; D020108:Nicorandil / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010179:Pancreas / Q000502:physiology; D020110:Pinacidil / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D017433:Protein Structure, Secondary; D051381:Rats; D011955:Receptors, Drug / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D064233:Sulfonylurea Receptors
D018528:ATP-Binding Cassette Transporters; C577508:Abcc8 protein, mouse; C577509:Abcc8 protein, rat; C577511:Abcc9 protein, mouse; C577512:Abcc9 protein, rat; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms; D011955:Receptors, Drug; D011993:Recombinant Fusion Proteins; D064233:Sulfonylurea Receptors; D019806:Cromakalim; D020108:Nicorandil; D020110:Pinacidil; D003981:Diazoxide