Structure-Activity Studies of 3,9-Diazaspiro[5.5]undecane-Based γ-Aminobutyric Acid Type A Receptor Antagonists with Immunomodulatory Effect.

The 3,9-diazaspiro[5.5]undecane-based compounds and have previously been reported to be potent competitive γ-aminobutyric acid type A receptor (GABAR) antagonists showing low cellular membrane permeability. Given the emerging peripheral application of GABAR ligands, we hypothesize analogs as promising lead structures for peripheral GABAR inhibition.

Molecular Determinants Underlying Delta Selective Compound 2 Activity at -Containing GABA Receptors.

Delta selective compound 2 (DS2; 4-chloro--[2-(2-thienyl)imidazo[1,2-]pyridin-3-yl]benzamide) is one of the most widely used tools to study selective actions mediated by -subunit-containing GABA receptors. DS2 was discovered over 10 years ago, but despite great efforts, the precise molecular site of action has remained elusive. Using a combination of computational modeling, site-directed mutagenesis, and cell-based pharmacological assays, we probed three potential binding sites for DS2 and analogs at receptors: an interface site in the extracellular domain (ECD), equivalent to the diazepam binding site in receptors, and two sites in the transmembrane domain (TMD) - one in the and one in the interface, with the site corresponding to the binding site for etomidate and a recently disclosed low-affinity binding site for diazepam.

Structural Determinants for the Mode of Action of Imidazopyridine DS2 at δ-Containing γ-Aminobutyric Acid Type A Receptors.

Despite the therapeutic relevance of δ-containing γ-aminobutyric acid type A receptors (GABARs) and the need for δ-selective compounds, the structural determinants for the mode and molecular site of action of δ-selective positive allosteric modulator imidazo[1,2-a]pyridine DS2 remain elusive. To guide the quest for insight, we synthesized a series of DS2 analogues guided by a structural receptor model. Using a fluorescence-based fluorometric imaging plate reader membrane potential assay, we found that the δ-selectivity and the pharmacological profile are severely affected by substituents in the 5-position of the imidazopyridine core scaffold.