Zinc Inhibits the GABAAR/ATPase during Postnatal Rat Development: The Role of Cysteine Residue

Abstract

Zinc ions (Zn2+) are concentrated in various brain regions and can act as a neuromodulator, targeting a wide spectrum of postsynaptic receptors and enzymes. Zn2+ inhibits the GABAARs, and its potency is profoundly affected by the subunit composition and neuronal developmental stage. Although the extracellular amino acid residues of the receptor’s hetero-oligomeric structure are preferred for Zn2+ binding, there are intracellular sites that, in principle, could coordinate its potency. However, their role in modulating the receptor function during postembryonic development remains unclear. The GABAAR possesses an intracellular ATPase that enables the energy-dependent anion transport via a pore. Here, we propose a mechanistic and molecular basis for the inhibition of intracellular GABAAR/ATPase function by Zn2+ in neonatal and adult rats. The enzymes within the scope of GABAAR performance as Cl−ATPase and then as Cl−, HCO3−ATPase form during the first week of postnatal rat development. In addition, we have shown that the Cl−ATPase form belongs to the β1 subunit, whereas the β3 subunit preferably possesses the Cl−, HCO3−ATPase activity. We demonstrated that a Zn2+ with variable efficacy inhibits the GABAAR as well as the ATPase activities of immature or mature neurons. Using fluorescence recording in the cortical synaptoneurosomes (SNs), we showed a competitive association between Zn2+ and NEM in parallel changes both in the ATPase activity and the GABAAR-mediated Cl− and HCO3− fluxes. Finally, by site-directed mutagenesis, we identified in the M3 domain of β subunits the cysteine residue (C313) that is essential for the manifestation of Zn2+ potency.

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

“…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 ). Furthermore, this enzyme is within the scope of GABA A R performance as Cl − ATPase during the first week of postnatal rodent development and then as a Cl − , HCO 3 − ATPase.…”