Homomeric rho1 GABAC receptor function is potentiated by S-nitrosylation

JAVIER GASULLA; ANDREA BELTRÁN GONZÁLEZ; DANIEL J. CALVO

Huerta Grande. Córdoba

Congreso; XXVI Reunión Anual de la Sociedad Argentina de Investigación en Neuroc; 2011

Sociedad Argentina de Investigación en Neurociencias

Nitric Oxide (NO) is a gas messenger produced in neurons that can modulate the activity of neurotransmitter receptors. We have previously shown that NO potentiates GABAC receptor function. Earlier studies reported the S-nitrosylation of cysteine residues in NMDA and GABAA receptors by NO. Thus, we examined if GABAC receptors can undergo analogous modifications. Homomeric ρ1 GABAC receptors (GABAρ1R) were expressed in oocytes and GABA-evoked responses electrophysiologically recorded in the presence or absence of the NO donor DEA/NONOate (DEA). GABAρ1 responses were significantly enhanced in a dose-dependent, fast and reversible manner by DEA. The specific NO scavenger CPTIO prevented these effects. Each GABAρ1R subunit contains three cysteine residues, namely: two extracellular at the cys-loop (C177 and C191) and one intracellular (C364). Site directed mutagenesis of the C177 and C191 renders non-functional receptors, but C364 can be safely exchanged by alanine. The chemical protection of these cysteine residues by sulfhydryl reagents (NEM, MTSEA) prevented DEA effects on GABAρ1R. Meanwhile, wild type receptors and mutant GABAρ1C364AR were similarly potentiated by DEA. These results suggest that NO enhances GABAC receptor function through S-nitrosylation occurring at the cys-loop.