Intricacies of GABAA Receptor Function: The Critical Role of the β3 Subunit in Norm and Pathology.

Neuronal intracellular chloride ([Cl-]i) is a key determinant in γ-aminobutyric acid type A (GABA)ergic signaling. γ-Aminobutyric acid type A receptors (GABAARs) mediate both inhibitory and excitatory neurotransmission, as the passive fluxes of Cl- and HCO3- via pores can be reversed by changes in the transmembrane concentration gradient of Cl-. The cation-chloride co-transporters (CCCs) are the primary systems for maintaining [Cl-]i homeostasis. However, despite extensive electrophysiological data obtained in vitro that are supported by a wide range of molecular biological studies on the expression patterns and properties of CCCs, the presence of ontogenetic changes in [Cl-]i-along with the consequent shift in GABA reversal potential-remain a subject of debate. Recent studies showed that the β3 subunit possesses properties of the P-type ATPase that participates in the ATP-consuming movement of Cl- via the receptor. Moreover, row studies have demonstrated that the β3 subunit is a key player in GABAAR performance and in the appearance of serious neurological disorders. In this review, we discuss the properties and driving forces of CCCs and Cl-, HCO3-ATPase in the maintenance of [Cl-]i homeostasis after changes in upcoming GABAAR function. Moreover, we discuss the contribution of the β3 subunit in the manifestation of epilepsy, autism, and other syndromes.