Loop-F of the α-subunit determines the pharmacologic profile of novel competitive inhibitors of GABAAreceptors.
The neurotransmitter γ-amino butyric acid (GABA) has a fundamental role in CNS function and ionotropic (GABAA) receptors that mediate many of the actions of GABA are important therapeutic targets. This study reports the mechanism of action of novel GABAAantagonists based on a tricyclic oxazolo-2,3-benzodiazepine scaffold. These compounds are orthosteric antagonists of GABA on heteropentameric GABAAreceptors of αxβ2γ2 configuration expressed in HEK293 cells. In silico modelling predicted that the test compounds docked in the GABA binding-pocket and would interact with amino-acid residues in the α- and β-subunit interface that are known to be important for the binding of GABA. Intriguingly, optimal docking also required an interaction with the non-conserved amino-terminal segment of Loop-F of the α-subunit. Testing of a compound with altered regiochemistry of the oxazolone moiety supported the model with respect to the conserved GABA-interacting residues in vitro as well as in vivo. The prediction regarding loop-F was examined by replacing the amino-terminal variable segment of loop-F of the α5-subunit with the corresponding residues in the α1- and α2-subunits. When tested with the novel inhibitors, the receptors formed by the modified α5-subunits displayed the pharmacologic phenotype of the source of loop-F. In summary, these data show that the variable amino-terminal segment of loop-F of the α-subunit determines the pharmacologic selectivity of the novel tricyclic inhibitors of GABAAreceptors.
Division of Preclinical Research, Egis Pharmaceuticals PLC, Hungary.
Balázs
B
Mihalik
Division of Preclinical Research, Egis Pharmaceuticals PLC, Hungary.
Adrienn
A
Pálvölgyi
MTA-SZTE Supramolecular and Nanostructured Materials Research Group of HAS, University of Szeged, Hungary.
Ferenc
F
Bogár
Division of Preclinical Research, Egis Pharmaceuticals PLC, Hungary.
Katalin
K
Megyeri
Chemical Research Division, Egis Pharmaceuticals PLC, Budapest, Hungary.
István
I
Ling
Chemical Research Division, Egis Pharmaceuticals PLC, Budapest, Hungary.
József
J
Barkóczy
Department of Medical Chemistry, University of Szeged, Hungary.
Ferenc
F
Bartha
Institute of Pharmaceutical Analysis, SZTE-MTA Lendület Foldamer Research Group, University of Szeged, Szeged, Hungary.
Tamás A
TA
Martinek
Division of Preclinical Research, Egis Pharmaceuticals PLC, Hungary.
István
I
Gacsályi
Division of Preclinical Research, Egis Pharmaceuticals PLC, Hungary. Electronic address: franzantoni@gmail.com.
Ferenc A
FA
Antoni
D001569:Benzodiazepines / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001667:Binding, Competitive; D003198:Computer Simulation; D058787:GABA-A Receptor Antagonists / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D062105:Molecular Docking Simulation; D010080:Oxazoles / Q000737:chemistry; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D058787:GABA-A Receptor Antagonists; D010080:Oxazoles; D021122:Protein Subunits; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D005680:gamma-Aminobutyric Acid
Extrasynaptic receptors; GABA; GABA(A) antagonists; Loop-F; Molecular modelling; Nootropic agents