Gamma 2 subunit-containing GABAA receptors display resistance to ROS modulation

LÓPEZ PAZOS MI; DEL VAS M; BELTRÁN GONZÁLEZ AN ; CALVO DJ

Modalidad virtual

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Biofísica; 2021

Sociedad Argentina de Biofísica

Endogenous reactive oxygen species (ROS) are involved in neuronal signalling and plasticity in normal physiology, aging and neurodegenerative disorders. Besides, GABAergic neurotransmission is sensitive to several redox agents including ROS. For example, we previously shown that tonic responses mediated by GABAAρ1 receptors can be modulated by hydrogen peroxide (H2O2) , ascorbic acid, glutathione and nitric oxide, through thiol modification of cysteines. We have also identified endogenous redox agents that modulate GABAA receptors involved in phasic inhibitory neurotransmission in the retina and hippocampus, but the molecular mechanisms of action remain elusive. Our studies have been now extended in order to analyze the effects of H2O2 on tonic and phasic responses mediated by diverse GABAA receptors subtypes. Heterologous expression of the GABA-gated Cl- channels was performed in Xenopus laevis oocytes followed by twoelectrode voltage-clamp recordings of the GABA-evoked ionic currents. H2O2 (1mM) potentiated GABAAα1β2 and GABAAα5β3 receptor responses elicited by submaximal concentrations of GABA (EC5-10). In contrast, equivalent responses mediated by GABAAα1β2γ2 and GABA Aα5β3γ2 receptors were not altered in the presence of H 2O2, suggesting that γ2 subunit conferred significant insensitivity to ROS modulation. H2O2 effects on GABAAα1β2 responses were reversible, dose and use-dependent, voltageinsensitive and partially prevented by irreversible alkylation of sulfhydryl groups with NEM. The degree of potentiation exerted by H2O2 was reduced by increases in agonist concentration. Concentration-response curves in the presence of H2O2 showed a leftward shift, compared to control values, and an increase in the maximal response. Potentiation induced by H2O2 on GABAAα5β3 receptor responses showed a similar profile. Additional experiments are being performed to elucidate the mechanisms of action underlying the effects of H2O2 on GABAA receptors.