TY - JOUR
T1 - Kavain, the Major Constituent of the Anxiolytic Kava Extract, Potentiates GABAA Receptors
T2 - Functional Characteristics and Molecular Mechanism
AU - Chua, Han Chow
AU - Christensen, Emilie H T
AU - Hoestgaard-Jensen, Kirsten
AU - Hartiadi, Leonny Y
AU - Ramzan, Iqbal
AU - Jensen, Anders A
AU - Absalom, Nathan L
AU - Chebib, Mary
PY - 2016/6/23
Y1 - 2016/6/23
N2 - Extracts of the pepper plant kava (Piper methysticum) are effecive in alleviating anxiety in clinical trials. Despite the long-standing therapeutic interest in kava, the molecular target(s) of the pharmacologically active constituents, kavalactones have not been established. γ-Aminobutyric acid type A receptors (GABAA Rs) are assumed to be the in vivo molecular target of kavalactones based on data from binding assays, but evidence in support of a direct interaction between kavalactones and GABAARs is scarce and equivocal. In this study, we characterised the functional properties of the major anxiolytic kavalactone, kavain at human recombinant α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5), α1βxδ2L (x = 1, 2 and 3) and α4β2ä GABAARs expressed in Xenopus oocytes using the two-electrode voltage clamp technique. We found that kavain positively modulated all receptors regardless of the subunit composition, but the degree of enhancement was greater at α4β2δ than at α1β2γ2L GABAARs. The modulatory effect of kavain was unaffected by flumazenil, indicating that kavain did not enhance GABAA Rs via the classical benzodiazepine binding site. The β3N265M point mutation which has been previously shown to profoundly decrease anaesthetic sensitivity, also diminished kavain-mediated potentiation. To our knowledge, this study is the first report of the functional characteristics of a single kavalactone at distinct GABAAR subtypes, and presents the first experimental evidence in support of a direct interaction between a kavalactone and GABAARs.
AB - Extracts of the pepper plant kava (Piper methysticum) are effecive in alleviating anxiety in clinical trials. Despite the long-standing therapeutic interest in kava, the molecular target(s) of the pharmacologically active constituents, kavalactones have not been established. γ-Aminobutyric acid type A receptors (GABAA Rs) are assumed to be the in vivo molecular target of kavalactones based on data from binding assays, but evidence in support of a direct interaction between kavalactones and GABAARs is scarce and equivocal. In this study, we characterised the functional properties of the major anxiolytic kavalactone, kavain at human recombinant α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5), α1βxδ2L (x = 1, 2 and 3) and α4β2ä GABAARs expressed in Xenopus oocytes using the two-electrode voltage clamp technique. We found that kavain positively modulated all receptors regardless of the subunit composition, but the degree of enhancement was greater at α4β2δ than at α1β2γ2L GABAARs. The modulatory effect of kavain was unaffected by flumazenil, indicating that kavain did not enhance GABAA Rs via the classical benzodiazepine binding site. The β3N265M point mutation which has been previously shown to profoundly decrease anaesthetic sensitivity, also diminished kavain-mediated potentiation. To our knowledge, this study is the first report of the functional characteristics of a single kavalactone at distinct GABAAR subtypes, and presents the first experimental evidence in support of a direct interaction between a kavalactone and GABAARs.
U2 - 10.1371/journal.pone.0157700
DO - 10.1371/journal.pone.0157700
M3 - Journal article
C2 - 27332705
SN - 1932-6203
VL - 11
SP - 1
EP - 17
JO - PLoS Computational Biology
JF - PLoS Computational Biology
IS - 6
M1 - e0157700
ER -