Identification and structure of intersubunit contact sites of GABAA receptors

Gamma-Aminobutyric acid (GABA) is the major inhibitory transmitter of the central nervous system. A large part of the actions of GABA are mediated by GABAA receptors. GABAA receptors are chloride ion channels that can be opened by GABA and are the site of action of a variety of pharmacologically and clinically important drugs, such as benzodiazepines, barbiturates, neuroactive steroids, anesthetics and convulsants. GABAA receptors located in distinct brain regions regulate anxiety, convulsions, muscle activity, cognition, vigilance, and memory. GABAA receptors consist of five subunits that can belong to different subunit classes (alpha, beta, gamma, delta, epsilon, pi, theta, rho). The major GABAA receptor subtypes consist of two alpha, two beta and one gamma subunit. Using molecular biological, biochemical, and immunological methods, in the present project amino acid sequences of alpha, beta und gamma subunits will be identified that are forming the direct contacts to neighbouring subunits and thus are important for the assembly of GABAA receptors. Using suitable computer programs, the three dimensional structure of these sequences will be predicted. These investigations will define a significant part of the surface structure of these subunits and are important for all further considerations on the structure and function of GABAA receptors. Studies in this project will also identify directly interacting sequences from neighbouring subunits. Structural prediction of these sequences and investigation of their most stable interaction using suitable computer programs will lead to a prediction of the structure of the subunit interface. Since pharmacological binding sites of GABAA receptors are located at subunit interfaces, information obtained will contribute to the generation of realistic structural models of such binding sites. Such models are of importance for the pharmaceutical industry because their application will lead to a more rational development of pharmacologically and clinically important drugs interacting with these binding sites.