Physiological Role of ATPase for GABAA Receptor Resensitization

Abstract

γ-Aminobutyric acid type A receptors (GABAARs) mediate primarily inhibitory synaptic transmission in the central nervous system. Following fast-paced activation, which provides the selective flow of mainly chloride (Cl−) and less bicarbonate (HCO3−) ions via the pore, these receptors undergo desensitization that is paradoxically prevented by the process of their recovery, referred to as resensitization. To clarify the mechanism of resensitization, we used the cortical synaptoneurosomes from the rat brain and HEK 293FT cells. Here, we describe the effect of γ-phosphate analogues (γPAs) that mimic various states of ATP hydrolysis on GABAAR-mediated Cl− and HCO3− fluxes in response to the first and repeated application of the agonist. We found that depending on the presence of bicarbonate, opened and desensitized states of the wild or chimeric GABAARs had different sensitivities to γPAs. This study presents the evidence that recovery of neuronal Cl− and HCO3− concentrations after desensitization is accompanied by a change in the intracellular ATP concentration via ATPase performance. The transition between the desensitization and resensitization states was linked to changes in both conformation and phosphorylation. In addition, the chimeric β3 isoform did not exhibit the desensitization of the GABAAR-mediated Cl− influx but only the resensitization. These observations lend a new physiological significance to the β3 subunit in the manifestation of GABAAR resensitization.

Phenols and GABAA receptors: from structure and molecular mechanisms action to neuropsychiatric sequelae

“…It was shown that the transition from the desensitization state to resensitization is coupled with a fall in [ATP]i, which is carried out via ATPase performance ( Figure 5 ). The critical role of ATPase during the resensitization process and the resulting conformational changes in GABA A Rs were confirmed using a thiol alkylating agent and a mutant receptor ( Menzikov et al, 2022 ). Phenol modulates the formation of a phosphoprotein (high-energy phosphate bond) and the rate of ATP-consuming Cl − transport by the ATPase ( Menzikov and Morozov, 2019 ).…”

“…Although some kinases play a role in the desensitization and retardation of GABA A R deactivation, the main players involved in the resensitization process have not been fully established. Recently, it was reported that the β3 and β1 subunits possess a phenol-regulated ATPase, which is localized in the ICD ( Menzikov, 2018 ; Menzikov et al, 2021 ) and that resensitization by the enzyme facilitates the replenishment of the neuronal concentrations of chloride ([Cl − ] i ) and bicarbonate ([HCO 3 − ] i ) after GABA A R activity and desensitization ( Menzikov et al, 2021 ; Menzikov et al, 2022 ). A recent finding showed that the Cl − ATPase activities belonging to the β1 and the β3 subunits have Cl − , HCO 3 − ATPase activity, which determines differences in their sensitivity to phenol ( Menzikov et al, 2023 ).…”

“…In this state, GABA can shift the TMP from hyperpolarization toward depolarization and even excitation, which depends not only on Cl − influx but also on HCO 3 − efflux via the channel ( Fujiwara-Tsukamoto et al, 2003 ; Kaila et al, 2014 ). Several reports showed that changing the [Cl − ] i is essential for desensitization ( Ghit et al, 2021 ), whereas changing the [HCO 3 − ] i is essential for receptor resensitization ( Menzikov et al, 2022 ).…”