RT Journal Article
SR Electronic
T1 Bidirectional Effect of Pregnenolone Sulfate on GluN1/GluN2A <em>N</em>-Methyl-<span class="sc">d</span>-Aspartate Receptor Gating Depending on Extracellular Calcium and Intracellular Milieu
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 650
OP 659
DO 10.1124/mol.115.100396
VO 88
IS 4
A1 Chopra, Divyan A.
A1 Monaghan, Daniel T.
A1 Dravid, Shashank M.
YR 2015
UL http://molpharm.aspetjournals.org/content/88/4/650.abstract
AB Pregnenolone sulfate (PS), one of the most commonly occurring neurosteroids in the central nervous system, influences the function of several receptors. PS modulates N-methyl-d-aspartate receptors (NMDARs) and has been shown to have both positive and negative modulatory effects on NMDAR currents generally in a subtype-selective manner. We assessed the gating mechanism of PS modulation of GluN1/GluN2A receptors transiently expressed in human embryonic kidney 293 cells using whole-cell and single-channel electrophysiology. Only a modest effect on the whole-cell responses was observed by PS in dialyzed (nonperforated) whole-cell recordings. Interestingly, in perforated conditions, PS was found to increase the whole-cell currents in the absence of nominal extracellular Ca2+, whereas PS produced an inhibition of the current responses in the presence of 0.5 mM extracellular Ca2+. The Ca2+-binding DRPEER motif and GluN1 exon-5 were found to be critical for the Ca2+-dependent bidirectional effect of PS. Single-channel cell-attached analysis demonstrated that PS primarily affected the mean open time to produce its effects: positive modulation mediated by an increase in duration of open time constants, and negative modulation mediated by a reduction in the time spent in a long-lived open state of the receptor. Further kinetic modeling of the single-channel data suggested that the positive and negative modulatory effects are mediated by different gating steps which may represent GluN2 and GluN1 subunit-selective conformational changes, respectively. Our studies provide a unique mechanism of modulation of NMDARs by an endogenous neurosteroid, which has implications for identifying state-dependent molecules.