Modulation by divalent cations of GABA rho 1 receptor from human retina expressed in Xenopus oocytes.

Research Center of Basic Medicine, Wuhan Institute of Children Disease, Wuhan 430016, People's Republic of China. kinvinw@hotmail.com

OBJECTIVE: To investigate functional homooligomeric GABA rho 1 receptors expressed in Xenopus oocytes and the modulation of divalent cations. METHODS: GABA rho 1 cDNA from human retina was transcribed in vitro to obtain sense rho 1 mRNA, which was microinjected into Xenopus oocytes. Two-electrodes voltage clamp technique was performed to record GABA-induced currents. RESULTS: Expressed receptors were found to have similar properties to GABAc receptors characterized in the retina. Cl-currents induced by GABA were blocked by picrotoxin instead of bicuculline. GABA-induced currents reversed at -19 +/- 2.5 mV, and EC50 was 3.3 mumol/L. Zn++ modulated GABA-induced currents with an IC50 = 9.6 mumol/L. Ni++, Cu++ and Cd++ inhibited GABA rho 1 obviously, too. Their rank order of potency was Zn++ > Ni++ > Cu++ > Cd++. CONCLUSION: Zinc (10 mumol/L) inhibited GABA-induced currents in a competitive manner, and its action was sensitive to extracellular pH. Site-directed mutagenesis revealed that substitution of a single histidine residue (H44 and H48) failed to affect zinc sensitivity.

PMID: 11862606 [PubMed - indexed for MEDLINE]