GABAA-coupled Cl-/HCO3-ATPase: switching Сl--channel/Сl--pump

Abstract

The paper reviewed the multifunctional nature of the biochemical properties of the GABAA-coupled Cl-/HCO3--ATPase from plasma membranes of neuronal cells of animal brain. It was shown, the enzyme can be an ion channel, in particular, including the properties of GABAA/benzodiazepine-Cl--channel receptor complex. The data in favor its functional and structural similarity with the inhibitory receptors. Yet, a number other enzyme properties indicates that it belongs to a transport ATPase of P-type (Cl--pump). The paper focuses on the possibilities of the protein functioning as a Cl--channel and Cl-- pump, it discusses the mechanisms of switching its modes of operation. Particular attention is paid to the key role of the relative concentrations of Cl- and HCO3- in neurons and in the extracellular medium, which determine how the protein functions (channel/pump) and in which direction (in/out) will be the Cl--transport. The review is a schematic model of the differential functioning of the enzyme in neuronal membranes. It is concluded that the understanding of the mechanisms of action enzyme can contribute to the study of the epileptogenesis processes.