Disease-associated missense mutations in GluN2B subunit alter NMDA receptor ligand binding and ion channel properties

Fedele, Laura; Newcombe, Joseph; Topf, Maya; Gibb, Alasdair J.; Harvey, Richard J.; Smart, Trevor G.

doi:10.1038/s41467-018-02927-4

Cited by 67 publications

(69 citation statements)

References 67 publications

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“…A second important conclusion from this study is that the M2 region can influence a host of receptor properties in addition to Mg 2+ block and Ca 2+ permeability, including agonist potency, proton sensitivity, open probability, and response time course, consistent with the recent studies (Fedele et al, ; Marwick, Hansen, Skehel, Hardingham, & Wyllie, ; Marwick, Skehel, Hardingham, & Wyllie, ; Mullier et al, ). For some variants, multiple functional effects have seemingly opposite actions when viewed simplistically as either enhancing or decreasing NMDAR function.…”

Section: Discussionsupporting

confidence: 88%

De novoGRINvariants in NMDA receptor M2 channel pore‐forming loop are associated with neurological diseases

Zhang

Tang

et al. 2019

Human Mutation

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N-methyl-D-aspartate receptors (NMDARs) mediate slow excitatory postsynaptic transmission in the central nervous system, thereby exerting a critical role in neuronal development and brain function. Rare genetic variants in the GRIN genes encoding NMDAR subunits segregated with neurological disorders. Here, we summarize the clinical presentations for 18 patients harboring 12 de novo missense variants in GRIN1, GRIN2A, and GRIN2B that alter residues in the M2 re-entrant loop, a region that lines the pore and is intolerant to missense variation. These de novo variants were identified in children with a set of neurological and neuropsychiatric conditions. Evaluation of the receptor cell surface expression, pharmacological properties, and biophysical characteristics show that these variants can have modest changes in agonist potency, proton inhibition, and surface expression. However, voltage-dependent magnesium inhibition is significantly reduced in all variants. The NMDARs hosting a single copy of a mutant subunit showed a dominant reduction in magnesium inhibition for some variants. These variant NMDARs also show reduced calcium permeability and single-channel conductance, as well as altered open probability. The data suggest that M2 missense variants increase NMDAR charge

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Section: Discussionsupporting

confidence: 88%

De novoGRINvariants in NMDA receptor M2 channel pore‐forming loop are associated with neurological diseases

Zhang

Tang

et al. 2019

Human Mutation

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“…Observing an effect of the variant despite the presence of wild-type subunits further supports a role for GluN2A N615K in disease causation. This finding indirectly supports the disease relevance of other NMDA receptor pore mutations where functional consequences have been established in diheteromers (Fedele et al 2018;Fernández-Marmiesse et al 2018).…”

Section: Glun2a N615k Reduces Mg 2+ Blockadesupporting

confidence: 73%

“…This finding indirectly supports the disease relevance of other NMDA receptor pore mutations where functional consequences have been established in diheteromers (Fedele et al . ; Fernández‐Marmiesse et al . ).…”

Section: Discussionmentioning

confidence: 99%

Functional assessment of triheteromeric NMDA receptors containing a human variant associated with epilepsy

Marwick

Hansen

Skehel

et al. 2019

The Journal of Physiology

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Key points NMDA receptors are neurotransmitter‐gated ion channels that are critically involved in brain cell communication Variations in genes encoding NMDA receptor subunits have been found in a range of neurodevelopmental disorders. We investigated a de novo genetic variant found in patients with epileptic encephalopathy that changes a residue located in the ion channel pore of the GluN2A NMDA receptor subunit. We found that this variant (GluN2A N615K ) impairs physiologically important receptor properties: it markedly reduces Mg 2+ blockade and channel conductance, even for receptors in which one GluN2A N615K is co‐assembled with one wild‐type GluN2A subunit. Our findings are consistent with the GluN2A N615K mutation being the primary cause of the severe neurodevelopmental disorder in carriers. Abstract NMDA receptors are ionotropic calcium‐permeable glutamate receptors with a voltage‐dependence mediated by blockade by Mg 2+ . Their activation is important in signal transduction, as well as synapse formation and maintenance. Two unrelated individuals with epileptic encephalopathy carry a de novo variant in the gene encoding the GluN2A NMDA receptor subunit: a N615K missense variant in the M2 pore helix ( GRIN2A C1845A ). We hypothesized that this variant underlies the neurodevelopmental disorders in carriers and explored its functional consequences by electrophysiological analysis in heterologous systems. We focused on GluN2A N615K co‐expressed with wild‐type GluN2 subunits in physiologically relevant triheteromeric NMDA receptors containing two GluN1 and two distinct GluN2 subunits, whereas previous studies have investigated the impact of the variant in diheteromeric NMDA receptors with two GluN1 and two identical GluN2 subunits. We found that GluN2A N615K ‐containing triheteromers showed markedly reduced Mg 2+ blockade, with a value intermediate between GluN2A N615K diheteromers and wild‐type NMDA receptors. Single‐channel conductance was reduced by four‐fold in GluN2A N615K diheteromers, again with an intermediate value in GluN2A N615K ‐containing triheteromers. Glutamate deactivation rates were unaffected. Furthermore, we expressed GluN2A N615K in cultured primary mouse cortical neurons, observing a decrease in Mg 2+ blockade and reduction in current density, confirming that the variant continues to have significant functional impact in neuronal systems. Our results ...

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“…The recurrence of de novo ASD-associated mutations in GRIN2B and rigorous analyses indicate that GRIN2B is a true ASD-associated gene (De Rubeis et al, 2014;Iossifov et al, 2014;O'Roak et al, 2012b;Stessman et al, 2017). However, we are only beginning to understand the impact of ASD-associated GRIN2B mutations on NMDAR function (Fedele et al, 2018;Liu et al, 2017;Vyklicky et al, 2018), and it is not yet clear how GRIN2B mutations alter neuronal development to cause ASD.…”

Section: Introductionmentioning

confidence: 99%

An autism-associated mutation in GluN2B prevents NMDA receptor trafficking and interferes with dendrite growth

Sceniak

Fedder

Wang

et al. 2019

Journal of Cell Science

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Autism spectrum disorders (ASDs) are neurodevelopmental disorders with multiple genetic associations. Analysis of de novo mutations identified GRIN2B, which encodes the GluN2B subunit of NMDA receptors, as a gene linked to ASDs with high probability. However, the mechanisms by which GRIN2B mutations contribute to ASD pathophysiology are not understood. Here, we investigated the cellular phenotypes induced by a human mutation that is predicted to truncate GluN2B within the extracellular loop. This mutation abolished NMDA-dependent Ca 2+ influx. Mutant GluN2B co-assembled with GluN1 but was not trafficked to the cell surface or dendrites. When mutant GluN2B was expressed in developing cortical neurons, dendrites appeared underdeveloped, with shorter and fewer branches, while spine density was unaffected. Mutant dendritic arbors were often dysmorphic, displaying abnormal filopodial-like structures. Interestingly, dendrite maldevelopment appeared when mutant GluN2B was expressed on a wild-type background, reflecting the disease given that individuals are heterozygous for GRIN2B mutations. Restoring the fourth transmembrane domain and cytoplasmic tail did not rescue the phenotypes. Finally, abnormal development was not accompanied by reduced mTOR signaling. These data suggest that mutations in GluN2B contribute to ASD pathogenesis by disrupting dendrite development.

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Disease-associated missense mutations in GluN2B subunit alter NMDA receptor ligand binding and ion channel properties

Cited by 67 publications

References 67 publications

De novoGRINvariants in NMDA receptor M2 channel pore‐forming loop are associated with neurological diseases

De novoGRINvariants in NMDA receptor M2 channel pore‐forming loop are associated with neurological diseases

Functional assessment of triheteromeric NMDA receptors containing a human variant associated with epilepsy

An autism-associated mutation in GluN2B prevents NMDA receptor trafficking and interferes with dendrite growth

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