TY - JOUR
T1 - Two de novo GluN2B mutations affect multiple NMDAR-functions and instigate severe pediatric encephalopathy
AU - Kellner, Shai
AU - Abbasi, Abeer
AU - Carmi, Ido
AU - Heinrich, Ronit
AU - Garin-Shkolnik, Tali
AU - Hershkovitz, Tova
AU - Giladi, Moshe
AU - Haitin, Yoni
AU - Johannesen, Katrine M
AU - Steensbjerre Møller, Rikke
AU - Berlin, Shai
N1 - © 2021, Kellner et al.
PY - 2021/7/2
Y1 - 2021/7/2
N2 - The N-methyl-D-aspartate receptors (NMDARs; GluNRS) are glutamate receptors, commonly located at excitatory synapses. Mutations affecting receptor function often lead to devastating neurodevelopmental disorders. We have identified two toddlers with different heterozygous missense mutations of the same, and highly conserved, glycine residue located in the ligand-binding-domain of GRIN2B: G689C and G689S. Structure simulations suggest severely impaired glutamate binding, which we confirm by functional analysis. Both variants show three orders of magnitude reductions in glutamate EC50, with G689S exhibiting the largest reductions observed for GRIN2B (~2000-fold). Moreover, variants multimerize with, and upregulate, GluN2Bwt-subunits, thus engendering a strong dominant-negative effect on mixed channels. In neurons, overexpression of the variants instigates suppression of synaptic GluNRs. Lastly, while exploring spermine potentiation as a potential treatment, we discovered that the variants fail to respond due to G689's novel role in proton-sensing. Together, we describe two unique variants with extreme effects on channel function. We employ protein-stability measures to explain why current (and future) LBD mutations in GluN2B primarily instigate Loss-of-Function.
AB - The N-methyl-D-aspartate receptors (NMDARs; GluNRS) are glutamate receptors, commonly located at excitatory synapses. Mutations affecting receptor function often lead to devastating neurodevelopmental disorders. We have identified two toddlers with different heterozygous missense mutations of the same, and highly conserved, glycine residue located in the ligand-binding-domain of GRIN2B: G689C and G689S. Structure simulations suggest severely impaired glutamate binding, which we confirm by functional analysis. Both variants show three orders of magnitude reductions in glutamate EC50, with G689S exhibiting the largest reductions observed for GRIN2B (~2000-fold). Moreover, variants multimerize with, and upregulate, GluN2Bwt-subunits, thus engendering a strong dominant-negative effect on mixed channels. In neurons, overexpression of the variants instigates suppression of synaptic GluNRs. Lastly, while exploring spermine potentiation as a potential treatment, we discovered that the variants fail to respond due to G689's novel role in proton-sensing. Together, we describe two unique variants with extreme effects on channel function. We employ protein-stability measures to explain why current (and future) LBD mutations in GluN2B primarily instigate Loss-of-Function.
U2 - 10.7554/elife.67555
DO - 10.7554/elife.67555
M3 - Article
C2 - 34212862
SN - 2050-084X
VL - 10
JO - eLife
JF - eLife
ER -