title: Inhibition of Plasma Membrane Na/Ca-Exchanger by KB-R7943 or Lithium Reveals Its Role in Ca-Dependent N-methyl-d-aspartate Receptor Inactivation.
abstract: To evaluate the possible role of the plasma membrane Na(+)/Ca(2+)-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 Ca(2+)-free solution and was not observed in the presence of extracellular Ca(2+) on 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-loaded neurons, suggesting that Ca(2+) 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 Ca(2+). Most likely, the accumulation of intracellular Ca(2+) is caused by the inhibition of Ca(2+) extrusion via NCX. Thus, KBR and Li(+) provoke Ca(2+)-dependent receptor inactivation due to the disruption of Ca(2+) extrusion by the NCX. The data reveal the role of NCX in regulation of Ca(2+)-dependent inactivation of NMDARs.
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Dmitry A
authors.identifier: http://orcid.org/0000-0002-2224-2145
authors.initials: DA
authors.lastname: Sibarov
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Polina A
authors.initials: PA
authors.lastname: Abushik
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Ekaterina E
authors.initials: EE
authors.lastname: Poguzhelskaya
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Bolshakov
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia antonov452002@yahoo.com.
authors.forename: Sergei M
authors.identifier: http://orcid.org/0000-0002-0644-9330
authors.initials: SM
authors.lastname: Antonov
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects*; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005998:Glycine / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D018020:Lithium Compounds / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D002614:Chelating Agents; D018691:Excitatory Amino Acid Antagonists; D018020:Lithium Compounds; D016194:Receptors, N-Methyl-D-Aspartate; D019831:Sodium-Calcium Exchanger; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D013890:Thiourea; D002118:Calcium; D005998:Glycine