Downregulation of calcium-dependent NMDA receptor desensitization by sodium-calcium exchangers: a role of membrane cholesterol

Abstract

BackgroundThe plasma membrane Na+/Ca2+-exchanger (NCX) has recently been shown to regulate Ca2+-dependent N-methyl-d-aspartate receptor (NMDAR) desensitization, suggesting a tight interaction of NCXs and NMDARs in lipid nanoclasters or “rafts”. To evaluate possible role of this interaction we studied effects of Li+ on NMDA-elicited whole-cell currents and Ca2+ responses of rat cortical neurons in vitro before and after cholesterol extraction by methyl-β-cyclodextrin (MβCD).ResultsSubstitution Li+ for Na+ in the external solution caused a concentration-dependent decrease of steady-state NMDAR currents from 440 ± 71 pA to 111 ± 29 pA in 140 mM Na+ and 140 mM Li+, respectively. The Li+ inhibition of NMDAR currents disappeared in the absence of Ca2+ in the external solution (Ca2+-free), suggesting that Li+ enhanced Ca2+-dependent NMDAR desensitization. Whereas the cholesterol extraction with MβCD induced a decrease of NMDAR currents to 136 ± 32 pA in 140 mM Na+ and 46 ± 15 pA in 140 mM Li+, the IC50 values for the Li+ inhibition were similar (about 44 mM Li+) before and after this procedure. In the Ca2+-free Na+ solution the steady-state NMDAR currents after the cholesterol extraction were 47 ± 6% of control values. Apparently this amplitude decrease was not Ca2+-dependent. In the Na+ solution containing 1 mM Ca2+ the Ca2+-dependent NMDAR desensitization was greater when cholesterol was extracted. Obviously, this procedure promoted its development. In agreement, Li+ and KB-R7943, an inhibitor of NCX, both considerably reduced NMDA-activated Ca2+ responses. The cholesterol extraction itself caused a decrease of NMDA-activated Ca2+ responses and, in addition, abolished the effects of Li+ and KB-R7943. The cholesterol loading into the plasma membrane caused a recovery of the KB-R7943 effects.ConclusionsTaken together our data suggest that NCXs downregulate the Ca2+-dependent NMDAR desensitization. Most likely, this is determined by a tight functional interaction of NCX and NMDAR molecules because of their co-localization in membrane lipid rafts. The destruction of these rafts is accompanied by an enhancement of NMDAR desensitization and a loss of NCX-selective agent effects on NMDARs.

Ca2+-Dependent Inactivation of GluN2A and GluN2B NMDA Receptors Occurs by a Common Kinetic Mechanism

“…Specifically, this observation may highlight the ability of channels to gate cooperatively as through a Ca 2þ -spillover mechanism as has been observed as well as in other channels (65) or through interactions with other channels (64,66). In addition to these inhibitory mechanisms, Na þ / Ca 2þ exchangers have been shown to be important in moderating the extent of CDI (67). Thus, CDI can be recruited by local as well as global Ca 2þ signals and may be under multiple regulatory mechanisms in postsynaptic compartments, consistent with the physiological importance of this process.…”

Spatial Coupling Tunes NMDA Receptor Responses via Ca2+Diffusion

“…Values reported in the literature for NMDA receptor CDI vary widely (ϳ20 -60%; Legendre et al, 1993;Medina et al, 1995;Zhang et al, 1998;Vissel et al, 2002;Sibarov et al, 2015Sibarov et al, , 2016Sibarov et al, , 2018. Much of this variability persists even when controlling for other forms of NMDA receptor time-dependent changes in activity by normalizing the current drop (I ss /I pk ) observed in the presence of external Ca 2ϩ to that observed in the absence of Ca 2ϩ (Iacobucci and Popescu, 2017; Fig.…”

Psychotropic Drugs for the Management of Chronic Pain and Itch

“…The data obtained make it possible to consider the possible therapeutic use of KB-R7943 and the NCX inhibitors that are similar to it in the mechanism of action. It was proposed that this effect is determined by a tight functional interaction of NCX and NMDAR molecules because of their co-localisation in membrane lipid rafts [137].…”