Cholesterol modulates open probability and desensitization of NMDA receptors

Abstract

Key pointsr NMDA receptors (NMDARs) are tetrameric cation channels permeable to calcium; they mediate excitatory synaptic transmission in the CNS and their excessive activation can lead to neurodegeneration.r Although these receptors are in direct contact with plasma membrane, lipid-NMDAR interactions are little understood.r Using cultured rat cerebellar granule cells, we show that acute and chronic pretreatments resulting in cell cholesterol depletion profoundly diminish NMDAR responses and increase NMDAR desensitization, and also that cholesterol enrichment potentiates NMDAR responses; however, cholesterol manipulation has no effect on the amplitude of AMPA/kainate receptor responses.r Diminution of NMDAR responses by cholesterol depletion is the result of a reduction of the ion channel open probability, whereas the increase in receptor desensitization is the result of an increase in the rate constant of entry into the desensitized state.r These results demonstrate the physiological role of membrane lipids in the modulation of NMDAR activity.Abstract NMDA receptors (NMDARs) are glutamate-gated ion channels that mediate excitatory neurotransmission in the CNS. Although these receptors are in direct contact with plasma membrane, lipid-NMDAR interactions are little understood. In the present study, we aimed at characterizing the effect of cholesterol on the ionotropic glutamate receptors. Whole-cell current responses induced by fast application of NMDA in cultured rat cerebellar granule cells (CGCs) were almost abolished (reduced to 3%) and the relative degree of receptor desensitization was increased (by seven-fold) after acute cholesterol depletion by methyl-β-cyclodextrin. Both of these effects were fully reversible by cholesterol repletion. By contrast, the responses mediated by AMPA/kainate receptors were not affected by cholesterol depletion. Similar results were obtained in CGCs after chronic inhibition of cholesterol biosynthesis by simvastatin and acute enzymatic cholesterol degradation to 4-cholesten-3-one by cholesterol oxidase. Fluorescence anisotropy measurements showed that membrane fluidity increased after methyl-β-cyclodextrin pretreatment. However, no change in fluidity was observed after cholesterol enzymatic degradation, suggesting that the effect of cholesterol on NMDARs is not mediated by changes in membrane fluidity. Our data show that diminution of NMDAR responses by cholesterol depletion is the result of a reduction of the open probability, whereas the increase in receptor desensitization is the result of an increase in the rate constant of entry into the desensitized state. Surface NMDAR population, agonist affinity, single-channel conductance and open time were not altered in cholesterol-depleted CGCs. The results of our experiments show that cholesterol is a strong endogenous modulator of NMDARs. N,N,3,phenylammonium p-toluenesulphonate.

Effects of the adipokinetic hormone/red pigment‐concentrating hormone (AKH/RPCH) family of peptides on MK‐801‐induced schizophrenia models

“…In a recent study, the physiological role of membrane lipids in the modulation of NMDAR activity was shown . In that study, it was shown that acute and chronic pretreatments resulting in cell cholesterol depletion profoundly diminished NMDAR responses and increased NMDAR desensitization in cultured rat cerebellar granule cells.…”

Biochemical and electrophysiological characterization of N‐glycans on NMDA receptor subunits

“…(i) The x ‐axis shows the total concentration of applied glycine including 0.04 μM of background glycine (Korinek et al . ). Dose–response curves for glycine are nearly identical between control‐treated and lectin‐treated CGC s, including the calculated values of the EC 50 (control: 1.7 ± 0.2 μM; AAL : 2 ± 0.3 μM; WGA : 1.5 ± 0.3 μM; ConA: 1.5 ± 0.3 μM; n ≥ 5; p > 0.05; anova ).…”

“…The calculated values of the EC 50 for NMDA (control: 112.5 AE 7.0 lM; AAL: 200.6 AE 13.4 lM; WGA: 188.6 AE 29.0 lM; ConA: 180.6 AE 21.4 lM; n ≥ 5) obtained from lectin-treated CGCs significantly differed from the control CGCs (p < 0.05; ANOVA; Student-Newman-Keuls method). (i) The x-axis shows the total concentration of applied glycine including 0.04 lM of background glycine(Korinek et al 2015). Dose-response curves for glycine are nearly identical between control-treated and lectin-treated CGCs, including the calculated values of the EC 50 (control: 1.7 AE 0.2 lM; AAL: 2 AE 0.3 lM; WGA: 1.5 AE 0.3 lM; ConA: 1.5 AE 0.3 lM; n≥ 5; p > 0.05; ANOVA).…”

Advancing NMDA Receptor Physiology by Integrating Multiple Approaches

“…Further, their activity is modulated by an array of small ions and molecules (protons, Zn 2+ , spermine) [1, 6], membrane lipids [7], as well as post-translational modifications such as phosphorylation [8]. Missense mutations distributed throughout NMDAR subunits have recently been associated with devastating neurological disorders [9, 10].…”