The GABAA receptor is a hetero-oligomeric membrane protein that hyperpolarizes neuronal membranes by opening an intrinsic Cl- channel gated by the neurotransmitter GABA. The principle function of GABAA receptors is inhibitory and aberrant GABAergic transmission has been associated with the etiology of several neurological and psychological disorders including epilepsy, myotonia, panic disorders and chronic drug dependence. Numerous clinically efficacious drugs enhance central nervous system inhibition by acting at their associated recognition sites and allosterically potentiating GABA-gated Cl- currents. These include the barbiturates, steroids, volatile anesthetics and benzodiazepines (BZDs). While it has been known for some time that BZDs exert their therapeutic action by modulating the GABAA receptor, the molecular mechanism by which this occurs is still somewhat controversial. The proposal will use a combination of molecular biological and electrophysiological techniques to obtain structural and functional information regarding the actions of BZDs at GABAA receptors. Residues critical for the actions of several BZD ligands will be identified in the alpha1 (a1) subunit (for alpha-beta-gamma receptors, a-b-g receptors) and the gamma2 (g2) subunit (beta-gamma receptors, b-g receptors) using site- directed mutagenesis and recombinant expression studies. Whole-cell electrophysiological recording techniques will be used to evaluate mechanisms by which these mutations impair the sensitivities of the recombinant receptors to BZDs and the actions of BZDs on the kinetic properties (such as agonist sensitivity and desensitization) of the GABAA receptor. These whole-cell and single-channel data will then be used to test and adapt working hypotheses that BZDs exert their effects by modulating receptor activation at steps subsequent to GABA binding. The design of more efficacious BZDs that can target the many different GABAA receptor subtypes that have been identified in the brain ultimately depend on understanding the structural requirements and precise mechanisms of action of this important class of compounds. Collectively, results from the proposed experiments should contribute to that effort.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS036195-03
Application #
2892221
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Program Officer
Jacobs, Margaret
Project Start
1997-04-01
Project End
2001-03-31
Budget Start
1999-04-01
Budget End
2000-03-31
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Alabama Birmingham
Department
Physiology
Type
Schools of Medicine
DUNS #
004514360
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Zheleznova, Nadezhda N; Sedelnikova, Anna; Weiss, David S (2009) Function and modulation of delta-containing GABA(A) receptors. Psychoneuroendocrinology 34 Suppl 1:S67-73
Zheleznova, N; Sedelnikova, A; Weiss, D S (2008) alpha1beta2delta, a silent GABAA receptor: recruitment by tracazolate and neurosteroids. Br J Pharmacol 153:1062-71
Torres, Viviana I; Weiss, David S (2002) Identification of a tyrosine in the agonist binding site of the homomeric rho1 gamma-aminobutyric acid (GABA) receptor that, when mutated, produces spontaneous opening. J Biol Chem 277:43741-8
Chang, Yongchang; Ghansah, Emmanuel; Chen, Yonghui et al. (2002) Desensitization mechanism of GABA receptors revealed by single oocyte binding and receptor function. J Neurosci 22:7982-90
Ghansah, E; Weiss, D S (2001) Modulation of GABA(A) receptors by benzodiazepines and barbiturates is autonomous of PKC activation. Neuropharmacology 40:327-33
Filippova, N; Sedelnikova, A; Zong, Y et al. (2000) Regulation of recombinant gamma-aminobutyric acid (GABA)(A) and GABA(C) receptors by protein kinase C. Mol Pharmacol 57:847-56
Filippova, N; Dudley, R; Weiss, D S (1999) Evidence for phosphorylation-dependent internalization of recombinant human rho1 GABAC receptors. J Physiol 518 ( Pt 2):385-99
Wotring, V E; Chang, Y; Weiss, D S (1999) Permeability and single channel conductance of human homomeric rho1 GABAC receptors. J Physiol 521 Pt 2:327-36
Ghansah, E; Weiss, D S (1999) Benzodiazepines do not modulate desensitization of recombinant alpha1beta2gamma2 GABA(A) receptors. Neuroreport 10:817-21