RT Journal Article
SR Electronic
T1 Inhibition of Plasma Membrane Na/Ca-Exchanger by KB-R7943 or Lithium Reveals Its Role in Ca-Dependent <em>N</em>-methyl-<span class="sc">d</span>-aspartate Receptor Inactivation
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 484
OP 495
DO 10.1124/jpet.115.227173
VO 355
IS 3
A1 Dmitry A. Sibarov
A1 Polina A. Abushik
A1 Ekaterina E. Poguzhelskaya
A1 Konstantin V. Bolshakov
A1 Sergei M. Antonov
YR 2015
UL http://jpet.aspetjournals.org/content/355/3/484.abstract
AB To evaluate the possible role of the plasma membrane Na+/Ca2+-exchanger (NCX) in regulation of N-methyl-d-aspartate (NMDA) receptors (NMDARs), we studied effects of 2-[2-[4-(4-nitrobenzyloxy) phenyl]ethyl]isothiourea methanesulfonate (KB-R7943; KBR) and lithium (inhibitors of NCX) on NMDA-elicited whole-cell currents using the patch-clamp technique on rat cortical neurons and human embryonic kidney 293T cells expressing recombinant NMDARs. KBR inhibited NMDAR currents in a voltage-independent manner with similar potency for receptors of GluN1/2A and GluN1/2B subunit compositions that excludes open-channel block and GluN2B-selective inhibition. The inhibition by KBR depended on glycine (Gly) concentration. At 30 μM NMDA, the KBR IC50 values were 5.3 ± 0.1 and 41.2 ± 8.8 μM for 1 and 300 μM Gly, respectively. Simultaneous application of NMDA + KBR in the absence of Gly induced robust inward NMDAR currents that peaked and then rapidly decreased. KBR, therefore, is an agonist (EC50 is 1.18 ± 0.16 µM) of the GluN1 subunit coagonist binding sites. The decrease of NMDA-elicited currents in the presence of KBR was abolished in Ca2+-free solution and was not observed in the presence of extracellular Ca2+ on 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-loaded neurons, suggesting that Ca2+ affects NMDARs from the cytosol. In agreement, the substitution of Li+ for extracellular Na+ caused a considerable decrease of NMDAR currents, which was not observed in the absence of extracellular Ca2+. Most likely, the accumulation of intracellular Ca2+ is caused by the inhibition of Ca2+ extrusion via NCX. Thus, KBR and Li+ provoke Ca2+-dependent receptor inactivation due to the disruption of Ca2+ extrusion by the NCX. The data reveal the role of NCX in regulation of Ca2+-dependent inactivation of NMDARs.