Glutathione gates GABAAβ3 receptors

AN BELTRÁN GONZÁLEZ; M LÓPEZ PAZOS; DJ CALVO

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

SAIC, SAIB, SAI, SAA, SAB, SAB, SAFE, SAFIS, SAH, SAP

Glutathione (GSH) is a thiol tripeptide that acts as the major antioxidant and redox buffer in the brain. It can be found at mM concentrations in all the neuronal compartments and the extracellular milieu. GSH exerts a protective role against oxidative stress, in the detoxification of H2O2 and lipid peroxides (as cofactor of the GSH peroxidase), scavenging of OH? and regeneration of the most important antioxidants (vitamins C and E). GSH is also involved in the regulation of many synaptic functions and in neuronal plasticity. Furthermore, GSH deficiency has been implicated in neurodegenerative diseases. Previous reports demonstrated that GSH modulates GABAergic neurotransmission, although experimental evidence is limited. We analyzed the effect of GSH on responses mediated by homomeric GABAAβ3 receptors. GABAAβ3 receptors are ionic channels exhibiting spontaneous openings that give place to agonist-independent Cl- currents, which are sensitive to picrotoxin and Zn2+. GABAAβ3 receptors can also be activated by mM concentrations of GABA (>3mM). In the present study, human GABAAβ3 receptors were expressed in Xenopus laevis oocytes and Cl- currents recorded by two-electrode voltage-clamp. Experimental results showed that the concentrations of GSH needed to gate GABAAβ3 receptors are lower than those of GABA. GSH effects were reversible, dose dependent and voltage independent. GSH also prevented Zn2+ inhibition of GABAAβ3 responses. GSSG, the oxidized form of GSH, also activated GABAAβ3 currents, but in a lesser extent than GSH. Irreversible alkylation of sulphydryl groups within the β3 subunits by N-ethylmaleimide failed to prevent GSH effects. Meanwhile, in preliminary experiments, GSH modulated GABAAα4β3 but not GABAAα4β3γ receptors. Given the molecular arrangement of these receptors, the presence of the β3-β3 interface might be essential for GSH actions. Further experiments are being carried out to elucidate the mechanisms of action underlying GSH effects.