Nitric oxide potentiation of the homomeric rho(1) GABA(C) receptor function.

JAVIER GASULLA; ANDREA BELTRÁN GONZÁLEZ; DANIEL J. CALVO

BRITISH JOURNAL OF PHARMACOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 167 p. 1369 - 1377

0007-1188

BACKGROUND AND PURPOSE NO is a highly diffusible and reactive gas produced in the nervous system, which acts as a neuronal signal mediating physiological or pathological mechanisms. NO can modulate the activity of neurotransmitter receptors and ion channels, including NMDA and GABA A receptors. In the present work, we examined whether GABA C receptor function can also be regulated by NO. EXPERIMENTAL APPROACH Homomeric rho1 GABA C receptors were expressed in oocytes and GABA-evoked responses electrophysiologically recorded in the presence or absence of the NO donor DEA. Chemical protection of cysteines by selective sulfhydryl reagents and site-directed mutagenesis were used to determine the protein residues involved in the actions of NO. KEY RESULTS GABArho1 receptor responses were significantly enhanced in a dose-dependent, fast and reversible manner by DEA and the specfic NO scavenger CPTIO prevented these potentiating effects. The r1 subunits contain only three cysteine residues, two extracellular at the Cys-loop (C177 and C191) and one intracellular (C364). Mutations of C177 and C191 render the r1 GABA receptors non-functional, but C364 can be safely exchanged by alanine (C364A). NEM, N-ethyl maleimide and (2-aminoethyl) methanethiosulfonate prevented the effects of DEA on GABArho1 receptors. Meanwhile, the potentiating effects of DEA on mutant GABArho1 C364A receptors were similar to those observed on wild-type receptors. CONCLUSIONS AND IMPLICATIONS Our results suggest that the function of GABA C receptors can be enhanced by NO acting at the extracellular Cys-loop.