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

Y1 - 2010

N2 - The novel ginkgolide analog ginkgolide X was characterized functionally at human glycine and gamma-aminobutyric acid type A receptors (GlyRs and GABAARs, respectively) in the fluorescence-based FLIPR Membrane Potential assay. The compound inhibited the signalling of all GABAAR subtypes included in the study with high nanomolar/low micromolar IC50 values, except the rho1 receptor at which it was a significantly weaker antagonist. Ginkgolide X also displayed high nanomolar/low micromolar IC50 values at the homomeric alpha1 and alpha2 GlyRs, whereas it was inactive at the heteromeric alpha1beta and alpha2beta subtypes at concentrations up to 300 muM. Thus, the functional properties of the compound were significantly different from those of the naturally occuring 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 alpha1 GlyR homology model revealed two distinct putative binding sites formed by the 6' M2 residues together with the 2' residues and with the 10' and 13' residues, respectively. Thus, we propose that the distinct functionalities of ginkgolide X compared to 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 gamma-aminobutyric acid type A receptors (GlyRs and GABAARs, respectively) in the fluorescence-based FLIPR Membrane Potential assay. The compound inhibited the signalling of all GABAAR subtypes included in the study with high nanomolar/low micromolar IC50 values, except the rho1 receptor at which it was a significantly weaker antagonist. Ginkgolide X also displayed high nanomolar/low micromolar IC50 values at the homomeric alpha1 and alpha2 GlyRs, whereas it was inactive at the heteromeric alpha1beta and alpha2beta subtypes at concentrations up to 300 muM. Thus, the functional properties of the compound were significantly different from those of the naturally occuring 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 alpha1 GlyR homology model revealed two distinct putative binding sites formed by the 6' M2 residues together with the 2' residues and with the 10' and 13' residues, respectively. Thus, we propose that the distinct functionalities of ginkgolide X compared to 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

VL - 285

SP - 10141

EP - 10153

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 13

ER -