N-Methyl-d-aspartate receptors (NMDARs), encoded by GRIN genes, are ionotropic glutamate receptors playing a critical role in synaptic transmission, plasticity, and synapse development. Genome sequence analyses have identified variants in GRIN genes in patients with neurodevelopmental disorders, but the underlying disease mechanisms are not well understood. Here, we have created and evaluated a transgenic mouse line carrying a missense variant Grin2bL825V , corresponding to a de novo GRIN2B variant encoding GluN2B(L825V) found in a patient with intellectual disability (ID) and autism spectrum disorder (ASD). We used HEK293T cells expressing recombinant receptors and primary hippocampal neurons prepared from heterozygous Grin2bL825V/+ (L825V/+) and wild-type (WT) Grin2b+/+ (+/+) male and female mice to assess the functional impact of the variant. Whole-cell NMDAR currents were reduced in neurons from L825V/+ compared with +/+ mice. The peak amplitude of NMDAR-mediated evoked excitatory postsynaptic currents (NMDAR-eEPSCs) was unchanged, but NMDAR-eEPSCs in L825V/+ neurons had faster deactivation compared with +/+ neurons and were less sensitive to a GluN2B-selective antagonist ifenprodil. Together, these results suggest a decreased functional contribution of GluN2B subunits to synaptic NMDAR currents in hippocampal neurons from L825V/+ mice. The analysis of the GluN2B(L825V) subunit surface expression and synaptic localization revealed no differences compared with WT GluN2B. Behavioral testing of mice of both sexes demonstrated hypoactivity, anxiety, and impaired sensorimotor gating in the L825V/+ strain, particularly affecting males, as well as cognitive symptoms. The heterozygous L825V/+ mouse offers a clinically relevant model of GRIN2B-related ID/ASD, and our results suggest synaptic-level functional changes that may contribute to neurodevelopmental pathology.

• Klíčová slova
• GluN2B, NMDA receptors, autism spectrum disorder, mouse model, synaptic transmission,
• MeSH
• excitační postsynaptické potenciály fyziologie   MeSH
• HEK293 buňky MeSH
• hipokampus metabolismus   MeSH
• lidé MeSH
• missense mutace MeSH
• myši inbrední C57BL MeSH
• myši transgenní * MeSH
• myši MeSH
• neurony metabolismus   MeSH
• neurovývojové poruchy * genetika   patofyziologie   metabolismus   MeSH
• receptory N-methyl-D-aspartátu * genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• NR2B NMDA receptor MeSH Prohlížeč
• receptory N-methyl-D-aspartátu * MeSH

N-methyl-D-aspartate receptors (NMDARs) are a subtype of ionotropic glutamate receptors critical for synaptic transmission and plasticity, and for the development of neural circuits. Rare or de-novo variants in GRIN genes encoding NMDAR subunits have been associated with neurodevelopmental disorders characterized by intellectual disability, developmental delay, autism, schizophrenia, or epilepsy. In recent years, some disease-associated variants in GRIN genes have been characterized using recombinant receptors expressed in non-neuronal cells, and a few variants have also been studied in neuronal preparations or animal models. Here we review the current literature on the functional evaluation of human disease-associated variants in GRIN1, GRIN2A and GRIN2B genes at all levels of analysis. Focusing on the impact of different patient variants at the level of receptor function, we discuss effects on receptor agonist and co-agonist affinity, channel open probability, and receptor cell surface expression. We consider how such receptor-level functional information may be used to classify variants as gain-of-function or loss-of-function, and discuss the limitations of this classification at the synaptic, cellular, or system level. Together this work by many laboratories worldwide yields valuable insights into NMDAR structure and function, and represents significant progress in the effort to understand and treat GRIN disorders. Keywords: NMDA receptor , GRIN genes, Genetic variants, Electrophysiology, Synapse, Animal models.

• MeSH
• genetická predispozice k nemoci MeSH
• genetická variace MeSH
• lidé MeSH
• neurovývojové poruchy genetika   MeSH
• proteiny nervové tkáně genetika   metabolismus   MeSH
• receptory N-methyl-D-aspartátu * genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• GRIN1 protein, human MeSH Prohlížeč
• N-methyl D-aspartate receptor subtype 2A MeSH Prohlížeč
• NR2B NMDA receptor MeSH Prohlížeč
• proteiny nervové tkáně MeSH
• receptory N-methyl-D-aspartátu * MeSH

N-methyl-D-aspartate receptor (NMDAR) hypofunction has been implicated in several neurodevelopmental disorders. NMDAR function can be augmented by positive allosteric modulators, including endogenous compounds, such as cholesterol and neurosteroid pregnenolone sulfate (PES). Here we report that PES accesses the receptor via the membrane, and its binding site is different from that of cholesterol. Alanine mutagenesis has identified residues that disrupt the steroid potentiating effect at the rat GluN1 (G638; I642) and GluN2B (W559; M562; Y823; M824) subunit. Molecular dynamics simulation indicates that, in the absence of PES, the GluN2B M1 helix residue W559 interacts with the M4 helix residue M824. In the presence of PES, the M1 and M4 helices of agonist-activated receptor rearrange, forming a tighter interaction with the GluN1 M3 helix residues G638 and I642. This stabilizes the open-state position of the GluN1 M3 helices. Together, our data identify a likely binding site for the NMDAR-positive allosteric modulator PES and describe a novel molecular mechanism by which NMDAR activity can be augmented.SIGNIFICANCE STATEMENT There is considerable interest in drugs that enhance NMDAR function and could compensate for receptor hypofunction associated with certain neuropsychiatric disorders. Positive allosteric modulators of NMDARs include an endogenous neurosteroid pregnenolone sulfate (PES), but the binding site of PES on the NMDAR and the molecular mechanism of potentiation are unknown. We use patch-clamp electrophysiology in combination with mutagenesis and in silico modeling to describe the interaction of PES with the NMDAR. Our data indicate that PES binds to the transmembrane domain of the receptor at a discrete group of residues at the GluN2B membrane helices M1 and M4 and the GluN1 helix M3, and that PES potentiates NMDAR function by stabilizing the open-state position of the GluN1 M3 helices.

• Klíčová slova
• glutamate receptors, neurosteroids, patch clamp, structure,
• MeSH
• alanin genetika   MeSH
• buněčná membrána účinky léků   MeSH
• cholesterol metabolismus   MeSH
• elektrofyziologické jevy MeSH
• HEK293 buňky MeSH
• konformace proteinů MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• metoda terčíkového zámku MeSH
• pregnenolon farmakologie   MeSH
• receptory N-methyl-D-aspartátu účinky léků   MeSH
• simulace molekulární dynamiky MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• alanin MeSH
• cholesterol MeSH
• NMDA receptor A1 MeSH Prohlížeč
• NR2B NMDA receptor MeSH Prohlížeč
• pregnenolon MeSH
• pregnenolone sulfate MeSH Prohlížeč
• receptory N-methyl-D-aspartátu MeSH

Cholesterol is a structural component of cellular membranes particularly enriched in synapses but its role in synaptic transmission remains poorly understood. We used rat hippocampal cultures and their acute cholesterol depletion by methyl-β-cyclodextrin as a tool to describe the physiological role of cholesterol in glutamatergic synaptic transmission. Cholesterol proved to be a key molecule for the function of synapses as its depletion resulted in a significant reduction of both NMDA receptor (NMDAR) and AMPA/kainate receptor-mediated evoked excitatory postsynaptic currents (eEPSCs), by 94% and 72%, respectively. We identified two presynaptic and two postsynaptic steps of synaptic transmission which are modulated by cholesterol and explain together the above-mentioned reduction of eEPSCs. In the postsynapse, we show that physiological levels of cholesterol are important for maintaining the normal probability of opening of NMDARs and for keeping NMDARs localized in synapses. In the presynapse, our results favour the hypothesis of a role of cholesterol in the propagation of axonal action potentials. Finally, cholesterol is a negative modulator of spontaneous presynaptic glutamate release. Our study identifies cholesterol as an important endogenous regulator of synaptic transmission and provides insight into molecular mechanisms underlying the neurological manifestation of diseases associated with impaired cholesterol synthesis or decomposition.

• MeSH
• AMPA receptory metabolismus   MeSH
• cholesterol farmakologie   MeSH
• excitační postsynaptické potenciály účinky léků   MeSH
• hipokampus účinky léků   metabolismus   MeSH
• krysa rodu Rattus MeSH
• kyselina glutamová metabolismus   MeSH
• mozková kůra účinky léků   metabolismus   MeSH
• nervový přenos * MeSH
• neurony účinky léků   metabolismus   MeSH
• potkani Wistar MeSH
• presynaptická zakončení účinky léků   metabolismus   MeSH
• receptory N-methyl-D-aspartátu metabolismus   MeSH
• synapse účinky léků   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AMPA receptory MeSH
• cholesterol MeSH
• kyselina glutamová MeSH
• receptory N-methyl-D-aspartátu MeSH