Kinetic and mutational analysis of Zn2+ modulation of recombinant human inhibitory glycine receptors
- 1 January 2000
- journal article
- Published by Wiley in Journal Of Physiology-London
- Vol. 522 (2), 215-230
- https://doi.org/10.1111/j.1469-7793.2000.t01-1-00215.x
Abstract
1. The effects of Zn2+ on glycine receptor (GlyR) currents were analysed in Xenopus oocytes and human embryonic kidney cells expressing homomeric human wild-type and mutant alpha1 subunit GlyRs. 2. Low concentrations (10 microM) of extracellular Zn2+ converted the partial agonist taurine into a high-efficacy agonist. Concentration-response analysis showed that the EC50 for taurine decreased whereas the Hill coefficient increased under these conditions. In contrast, 50-500 microM Zn2+ showed an increased EC50 value and reduced maximal inducible taurine currents. The potency of competitive antagonists was not affected in the presence of Zn2+. 3. Single-channel recording from outside-out patches revealed different kinetics of glycine- and taurine-gated currents. With both agonists, Zn2+ altered the open probability of the alpha1 GlyR without changing its unitary conductance. Low Zn2+ concentrations (5 microM) increased both the opening frequency and mean burst duration, whereas higher Zn2+ concentrations (> 50 microM) reduced GlyR open probability mainly by decreasing the open frequency and the relative contribution of the longest burst of the single-channel events. 4. Site-directed mutagenesis of the GlyR alpha1 subunit identified aspartate 80 and threonine 112 as important determinants of Zn2+ potentiation and inhibition, respectively, without affecting potentiation by ethanol. 5. Our data support the view that Zn2+ modulates different steps of the receptor binding and gating cycle via specific allosteric high- and low-affinity binding sites in the extracellular N-terminal region of the GlyR alpha1 subunit.This publication has 54 references indexed in Scilit:
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