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Vieira MM, Peng S, Won S, Hong E, Inati SK, Thurm A, Thiam AH, Kim S, Myers SJ, Badger JD, Traynelis SF, Lu W, Roche KW. A Frameshift Variant of GluN2A Identified in an Epilepsy Patient Results in NMDA Receptor Mistargeting. J Neurosci 2024; 44:e0557232023. [PMID: 38050135 PMCID: PMC10860613 DOI: 10.1523/jneurosci.0557-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 08/24/2023] [Accepted: 11/14/2023] [Indexed: 12/06/2023] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs) are crucial for neuronal development and synaptic plasticity. Dysfunction of NMDARs is associated with multiple neurodevelopmental disorders, including epilepsy, autism spectrum disorder, and intellectual disability. Understanding the impact of genetic variants of NMDAR subunits can shed light on the mechanisms of disease. Here, we characterized the functional implications of a de novo mutation of the GluN2A subunit (P1199Rfs*32) resulting in the truncation of the C-terminal domain. The variant was identified in a male patient with epileptic encephalopathy, multiple seizure types, severe aphasia, and neurobehavioral changes. Given the known role of the CTD in NMDAR trafficking, we examined changes in receptor localization and abundance at the postsynaptic membrane using a combination of molecular assays in heterologous cells and rat primary neuronal cultures. We observed that the GluN2A P1199Rfs*32-containing receptors traffic efficiently to the postsynaptic membrane but have increased extra-synaptic expression relative to WT GluN2A-containing NMDARs. Using in silico predictions, we hypothesized that the mutant would lose all PDZ interactions, except for the recycling protein Scribble1. Indeed, we observed impaired binding to the scaffolding protein postsynaptic protein-95 (PSD-95); however, we found the mutant interacts with Scribble1, which facilitates the recycling of both the mutant and the WT GluN2A. Finally, we found that neurons expressing GluN2A P1199Rfs*32 have fewer synapses and decreased spine density, indicating compromised synaptic transmission in these neurons. Overall, our data show that GluN2A P1199Rfs*32 is a loss-of-function variant with altered membrane localization in neurons and provide mechanistic insight into disease etiology.
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Affiliation(s)
- M M Vieira
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda 20892, Maryland
| | - S Peng
- Synapse and Neural Circuit Research Section, NINDS, NIH, Bethesda 20892, Maryland
| | - S Won
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda 20892, Maryland
| | - E Hong
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda 20892, Maryland
| | - S K Inati
- Neurophysiology of Epilepsy Unit, NINDS, NIH, Bethesda 20892, Maryland
| | - A Thurm
- National Institute of Mental Health, National Institutes of Health, Bethesda 20892, Maryland
| | - A H Thiam
- Office of the Clinical Director, NINDS, NIH, Bethesda 20892, Maryland
| | - S Kim
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta 30322, Georgia
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta 30322, Georgia
| | - S J Myers
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta 30322, Georgia
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta 30322, Georgia
| | - J D Badger
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda 20892, Maryland
| | - S F Traynelis
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta 30322, Georgia
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta 30322, Georgia
| | - W Lu
- Synapse and Neural Circuit Research Section, NINDS, NIH, Bethesda 20892, Maryland
| | - K W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda 20892, Maryland
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