TY - JOUR
T1 - Ginkgolide X is a potent antagonist of anionic Cys-loop receptors with a unique selectivity profile at glycine receptors
AU - Jensen, Anders Asbjørn
AU - Bergmann, Marianne Lerbæk
AU - Sander, Tommy
AU - Balle, Thomas
PY - 2010/3/26
Y1 - 2010/3/26
N2 - The novel ginkgolide analog ginkgolide X was characterized functionally at human glycine and γ-aminobutyric acid type A receptors (GlyRs and GABAARs, respectively) in the fluorescence-based FLIPR™ Membrane Potential assay. The compound inhibited the signaling of all GABA AR subtypes included in the study with high nanomolar/low micromolar IC50 values, except the ρ1 receptor at which it was a significantly weaker antagonist. Ginkgolide X also displayed high nanomolar/low micromolar IC50 values at the homomeric α1 and α2 GlyRs, whereas it was inactive at the heteromeric α1β and α2β subtypes at concentrations up to 300 μM. Thus, the functional properties of the compound were significantly different from those of the naturally occurring ginkgolides A, B, C, J, and M but similar to those of picrotoxin. In a mutagenesis study the 6′ M2 residues in the GlyR ion channel were identified as the primary molecular determinant of the selectivity profile of ginkgolide X, and a 6′ M2 ring consisting of five Thr residues was found to be of key importance for its activity at the GABAAR. Conformational analysis and docking of low-energy conformations of the native ginkgolide A and ginkgolide X into a α1 GlyR homology model revealed two distinct putative binding sites formed by the 6′ M2 residues together with the 2′ residues and the 10′ and 13′ residues, respectively. Thus, we propose that the distinct functionalities of ginkgolide X compared with the other ginkgolides could arise from different flexibility and thus different binding modes to the ion channel of the anionic Cys-loop receptor.
AB - The novel ginkgolide analog ginkgolide X was characterized functionally at human glycine and γ-aminobutyric acid type A receptors (GlyRs and GABAARs, respectively) in the fluorescence-based FLIPR™ Membrane Potential assay. The compound inhibited the signaling of all GABA AR subtypes included in the study with high nanomolar/low micromolar IC50 values, except the ρ1 receptor at which it was a significantly weaker antagonist. Ginkgolide X also displayed high nanomolar/low micromolar IC50 values at the homomeric α1 and α2 GlyRs, whereas it was inactive at the heteromeric α1β and α2β subtypes at concentrations up to 300 μM. Thus, the functional properties of the compound were significantly different from those of the naturally occurring ginkgolides A, B, C, J, and M but similar to those of picrotoxin. In a mutagenesis study the 6′ M2 residues in the GlyR ion channel were identified as the primary molecular determinant of the selectivity profile of ginkgolide X, and a 6′ M2 ring consisting of five Thr residues was found to be of key importance for its activity at the GABAAR. Conformational analysis and docking of low-energy conformations of the native ginkgolide A and ginkgolide X into a α1 GlyR homology model revealed two distinct putative binding sites formed by the 6′ M2 residues together with the 2′ residues and the 10′ and 13′ residues, respectively. Thus, we propose that the distinct functionalities of ginkgolide X compared with the other ginkgolides could arise from different flexibility and thus different binding modes to the ion channel of the anionic Cys-loop receptor.
KW - Former Faculty of Pharmaceutical Sciences
U2 - 10.1074/jbc.M109.079319
DO - 10.1074/jbc.M109.079319
M3 - Journal article
C2 - 20106969
SN - 0021-9258
VL - 285
SP - 10141
EP - 10153
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 13
ER -