Naringin directly activates inwardly rectifying potassium channels at an overlapping binding site to tertiapin-Q

Tin T. Yow, Elena Pera, Nathan Absalom, Marika Heblinski, Graham Ar Johnston, Jane R. Hanrahan, Mary Chebib*

*Corresponding author for this work

    Research output: Contribution to journalArticle

    36 Citations (Scopus)

    Abstract

    BACKGROUND G protein-coupled inwardly rectifying potassium (K IR3) channels are important proteins that regulate numerous physiological processes including excitatory responses in the CNS and the control of heart rate. Flavonoids have been shown to have significant health benefits and are a diverse source of compounds for identifying agents with novel mechanisms of action. EXPERIMENTAL APPROACH The flavonoid glycoside, naringin, was evaluated on recombinant human K IR3.1-3.4 and K IR3.1-3.2 expressed in Xenopus oocytes using two-electrode voltage clamp methods. In addition, we evaluated the activity of naringin alone and in the presence of the K IR3 channel blocker tertiapin-Q (0.5 nM, 1 nM and 3 nM) at recombinant K IR3.1-3.4 channels. Site-directed mutagenesis was used to identify amino acids within the M1-M2 loop of the K IR3.1 F137S mutant channel important for naringin's activity. KEY RESULTS Naringin (100 μM) had minimal effect on uninjected oocytes but activated K IR3.1-3.4 and K IR3.1-3.2 channels. The activation by naringin of K IR3.1-3.4 channels was inhibited by tertiapin-Q in a competitive manner. An alanine-scan performed on the K IR3.1 F137S mutant channel, replacing one by one aromatic amino acids within the M1-M2 loop, identified tyrosines 148 and 150 to be significantly contributing to the affinity of naringin as these mutations reduced the activity of naringin by 20- and 40-fold respectively. CONCLUSIONS AND IMPLICATIONS These results show that naringin is a direct activator of K IR3 channels and that tertiapin-Q shares an overlapping binding site on the K IR3.1-3.4. This is the first example of a ligand that activates K IR3 channels by binding to the extracellular M1-M2 linker of the channel.

    Original languageEnglish
    Pages (from-to)1017-1033
    Number of pages17
    JournalBritish Journal of Pharmacology
    Volume163
    Issue number5
    DOIs
    Publication statusPublished - Jul 2011

    Keywords

    • flavonoid glycosides
    • flavonoids
    • G protein-coupled inwardly rectifying potassium channels
    • G protein-coupled receptor
    • naringin
    • tertiapin-Q

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