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Barragan EV, Anisimova M, Vijayakumar V, Coblentz A, Park DK, Salaka RJ, Nisan AFK, Petshow S, Dore K, Zito K, Gray JA. d-Serine Inhibits Non-ionotropic NMDA Receptor Signaling. J Neurosci 2024; 44:e0140242024. [PMID: 38942470 PMCID: PMC11308331 DOI: 10.1523/jneurosci.0140-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/24/2024] [Accepted: 06/25/2024] [Indexed: 06/30/2024] Open
Abstract
NMDA-type glutamate receptors (NMDARs) are widely recognized as master regulators of synaptic plasticity, most notably for driving long-term changes in synapse size and strength that support learning. NMDARs are unique among neurotransmitter receptors in that they require binding of both neurotransmitter (glutamate) and co-agonist (e.g., d-serine) to open the receptor channel, which leads to the influx of calcium ions that drive synaptic plasticity. Over the past decade, evidence has accumulated that NMDARs also support synaptic plasticity via ion flux-independent (non-ionotropic) signaling upon the binding of glutamate in the absence of co-agonist, although conflicting results have led to significant controversy. Here, we hypothesized that a major source of contradictory results might be attributed to variable occupancy of the co-agonist binding site under different experimental conditions. To test this hypothesis, we manipulated co-agonist availability in acute hippocampal slices from mice of both sexes. We found that enzymatic scavenging of endogenous co-agonists enhanced the magnitude of long-term depression (LTD) induced by non-ionotropic NMDAR signaling in the presence of the NMDAR pore blocker MK801. Conversely, a saturating concentration of d-serine completely inhibited LTD and spine shrinkage induced by glutamate binding in the presence of MK801 or Mg2+ Using a Förster resonance energy transfer (FRET)-based assay in cultured neurons, we further found that d-serine completely blocked NMDA-induced conformational movements of the GluN1 cytoplasmic domains in the presence of MK801. Our results support a model in which d-serine availability serves to modulate NMDAR signaling and synaptic plasticity even when the NMDAR is blocked by magnesium.
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Affiliation(s)
- Eden V Barragan
- Center for Neuroscience, University of California, Davis, California 95618
| | - Margarita Anisimova
- Center for Neuroscience, University of California, Davis, California 95618
- Departments of Neurobiology, Physiology and Behavior, University of California, Davis, California 95618
| | - Vishnu Vijayakumar
- Center for Neural Circuits and Behavior, Department of Neuroscience and Section for Neurobiology, Division of Biology, University of California at San Diego, San Diego, California 92093
| | - Azariah Coblentz
- Center for Neuroscience, University of California, Davis, California 95618
- Departments of Neurobiology, Physiology and Behavior, University of California, Davis, California 95618
| | - Deborah K Park
- Center for Neuroscience, University of California, Davis, California 95618
- Departments of Neurobiology, Physiology and Behavior, University of California, Davis, California 95618
| | - Raghava Jagadeesh Salaka
- Center for Neuroscience, University of California, Davis, California 95618
- Neurology, University of California, Davis, California 95618
| | - Atheer F K Nisan
- Center for Neuroscience, University of California, Davis, California 95618
| | - Samuel Petshow
- Center for Neuroscience, University of California, Davis, California 95618
- Departments of Neurobiology, Physiology and Behavior, University of California, Davis, California 95618
| | - Kim Dore
- Center for Neural Circuits and Behavior, Department of Neuroscience and Section for Neurobiology, Division of Biology, University of California at San Diego, San Diego, California 92093
| | - Karen Zito
- Center for Neuroscience, University of California, Davis, California 95618
- Departments of Neurobiology, Physiology and Behavior, University of California, Davis, California 95618
| | - John A Gray
- Center for Neuroscience, University of California, Davis, California 95618
- Neurology, University of California, Davis, California 95618
- Psychiatry and Behavioral Sciences, University of California, Davis, California 95618
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Brown SE, Wang Z(Z, Newman EL, Engin E, Berretta S, Balu DT, Folorunso OO. Serine racemase deletion alters adolescent social behavior and whole-brain cFos activation. Front Psychiatry 2024; 15:1365231. [PMID: 38979499 PMCID: PMC11228300 DOI: 10.3389/fpsyt.2024.1365231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 05/06/2024] [Indexed: 07/10/2024] Open
Abstract
Background Neurodevelopmental disorders (NDDs) can cause debilitating impairments in social cognition and aberrant functional connectivity in large-scale brain networks, leading to social isolation and diminished everyday functioning. To facilitate the treatment of social impairments, animal models of NDDs that link N- methyl-D-aspartate receptor (NMDAR) hypofunction to social deficits in adulthood have been used. However, understanding the etiology of social impairments in NDDs requires investigating social changes during sensitive windows during development. Methods We examine social behavior during adolescence using a translational mouse model of NMDAR hypofunction (SR-/-) caused by knocking out serine racemase (SR), the enzyme needed to make D-serine, a key NMDAR coagonist. Species-typical social interactions are maintained through brain-wide neural activation patterns; therefore, we employed whole-brain cFos activity mapping to examine network-level connectivity changes caused by SR deletion. Results In adolescent SR-/- mice, we observed disinhibited social behavior toward a novel conspecific and rapid social habituation toward familiar social partners. SR-/- mice also spent more time in the open arm of the elevated plus maze which classically points to an anxiolytic behavioral phenotype. These behavioral findings point to a generalized reduction in anxiety-like behavior in both social and non-social contexts in SR-/- mice; importantly, these findings were not associated with diminished working memory. Inter-regional patterns of cFos activation revealed greater connectivity and network density in SR-/- mice compared to controls. Discussion These results suggest that NMDAR hypofunction - a potential biomarker for NDDs - can lead to generalized behavioral disinhibition in adolescence, potentially arising from disrupted communication between and within salience and default mode networks.
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Affiliation(s)
- Stephanie E. Brown
- Division of Basic Neuroscience, Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, United States
| | - Ziyi (Zephyr) Wang
- Division of Basic Neuroscience, Stress Neurobiology Laboratory, McLean Hospital, Belmont, MA, United States
| | - Emily L. Newman
- Department of Psychiatry, Harvard Medical School, Boston, MA, United States
- Division of Depression and Anxiety Disorders, Neurobiology of Fear Laboratory, McLean Hospital, Belmont, MA, United States
| | - Elif Engin
- Division of Basic Neuroscience, Stress Neurobiology Laboratory, McLean Hospital, Belmont, MA, United States
- Department of Psychiatry, Harvard Medical School, Boston, MA, United States
| | - Sabina Berretta
- Department of Psychiatry, Harvard Medical School, Boston, MA, United States
- Division of Basic Neuroscience, Translational Neuroscience Laboratory, McLean Hospital, Belmont, MA, United States
| | - Darrick T. Balu
- Division of Basic Neuroscience, Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, United States
- Department of Psychiatry, Harvard Medical School, Boston, MA, United States
| | - Oluwarotimi O. Folorunso
- Division of Basic Neuroscience, Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, United States
- Department of Psychiatry, Harvard Medical School, Boston, MA, United States
- Division of Basic Neuroscience, Translational Neuroscience Laboratory, McLean Hospital, Belmont, MA, United States
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Barragan EV, Anisimova M, Vijayakumar V, Coblentz AC, Park DK, Salaka RJ, Nisan AFK, Petshow S, Dore K, Zito K, Gray JA. D-Serine inhibits non-ionotropic NMDA receptor signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596266. [PMID: 38854020 PMCID: PMC11160797 DOI: 10.1101/2024.05.29.596266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
NMDA-type glutamate receptors (NMDARs) are widely recognized as master regulators of synaptic plasticity, most notably for driving long-term changes in synapse size and strength that support learning. NMDARs are unique among neurotransmitter receptors in that they require binding of both neurotransmitter (glutamate) and co-agonist (e.g. d -serine) to open the receptor channel, which leads to the influx of calcium ions that drive synaptic plasticity. Over the past decade, evidence has accumulated that NMDARs also support synaptic plasticity via ion flux-independent (non-ionotropic) signaling upon the binding of glutamate in the absence of co-agonist, although conflicting results have led to significant controversy. Here, we hypothesized that a major source of contradictory results can be attributed to variable occupancy of the co-agonist binding site under different experimental conditions. To test this hypothesis, we manipulated co-agonist availability in acute hippocampal slices from mice of both sexes. We found that enzymatic scavenging of endogenous co-agonists enhanced the magnitude of LTD induced by non-ionotropic NMDAR signaling in the presence of the NMDAR pore blocker, MK801. Conversely, a saturating concentration of d -serine completely inhibited both LTD and spine shrinkage induced by glutamate binding in the presence of MK801. Using a FRET-based assay in cultured neurons, we further found that d -serine completely blocked NMDA-induced conformational movements of the GluN1 cytoplasmic domains in the presence of MK801. Our results support a model in which d -serine inhibits ion flux-independent NMDAR signaling and plasticity, and thus d -serine availability could serve to modulate NMDAR signaling even when the NMDAR is blocked by magnesium. Significance Statement NMDARs are glutamate-gated cation channels that are key regulators of neurodevelopment and synaptic plasticity and unique in their requirement for binding of a co-agonist (e.g. d -serine) in order for the channel to open. NMDARs have been found to drive synaptic plasticity via non-ionotropic (ion flux-independent) signaling upon the binding of glutamate in the absence of co-agonist, though conflicting results have led to controversy. Here, we found that d -serine inhibits non-ionotropic NMDAR-mediated LTD and LTD-associated spine shrinkage. Thus, a major source of the contradictory findings might be attributed to experimental variability in d -serine availability. In addition, the developmental regulation of d -serine levels suggests a role for non-ionotropic NMDAR plasticity during critical periods of plasticity.
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Arizanovska D, Emodogo JA, Lally AP, Palavicino-Maggio CB, Liebl DJ, Folorunso OO. Cross species review of the physiological role of D-serine in translationally relevant behaviors. Amino Acids 2023; 55:1501-1517. [PMID: 37833512 PMCID: PMC10689556 DOI: 10.1007/s00726-023-03338-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 09/19/2023] [Indexed: 10/15/2023]
Abstract
Bridging the gap between preclinical models of neurological and psychiatric disorders with their human manifestations is necessary to understand their underlying mechanisms, identify biomarkers, and develop novel therapeutics. Cognitive and social impairments underlie multiple neuropsychiatric and neurological disorders and are often comorbid with sleep disturbances, which can exacerbate poor outcomes. Importantly, many symptoms are conserved between vertebrates and invertebrates, although they may have subtle differences. Therefore, it is essential to determine the molecular mechanisms underlying these behaviors across different species and their translatability to humans. Genome-wide association studies have indicated an association between glutamatergic gene variants and both the risk and frequency of psychiatric disorders such as schizophrenia, bipolar disorder, and autism spectrum disorder. For example, changes in glutamatergic neurotransmission, such as glutamate receptor subtype N-methyl-D-aspartate receptor (NMDAR) hypofunction, have been shown to contribute to the pathophysiology of schizophrenia. Furthermore, in neurological disorders, such as traumatic brain injury and Alzheimer's disease, hyperactivation of NMDARs leads to synaptic damage. In addition to glutamate binding, NMDARs require the binding of a co-agonist D-serine or glycine to the GluN1 subunit to open. D-serine, which is racemized from L-serine by the neuronal enzyme serine racemase (SRR), and both SRR and D-serine are enriched in cortico-limbic brain regions. D-serine is critical for complex behaviors, such as cognition and social behavior, where dysregulation of its synthesis and release has been implicated in many pathological conditions. In this review, we explore the role of D-serine in behaviors that are translationally relevant to multiple psychiatric and neurological disorders in different models across species.
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Affiliation(s)
- Dena Arizanovska
- The Miami Project to Cure Paralysis, Department of Neurosurgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Jada A Emodogo
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA
| | - Anna P Lally
- Translational Neuroscience Laboratory, McLean Hospital, Belmont, MA, USA
| | - Caroline B Palavicino-Maggio
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA
- Neurobiological Mechanisms of Aggression Laboratory, McLean Hospital, Belmont, MA, USA
| | - Daniel J Liebl
- The Miami Project to Cure Paralysis, Department of Neurosurgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Oluwarotimi O Folorunso
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA.
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Yoshikawa M, Okubo M, Shirose K, Kan T, Kawaguchi M. d-Serine Increases Release of Acetylcholine in Rat Submandibular Glands. BIOLOGY 2023; 12:1227. [PMID: 37759626 PMCID: PMC10526048 DOI: 10.3390/biology12091227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/10/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023]
Abstract
d-serine has been observed in submandibular gland tissue in rats, but its functions remain to be clarified. Oral administration of d-serine, but not l-serine, increased its concentrations in the submandibular gland and pilocarpine-induced salivary secretion. In vivo microdialysis was used to collect the d- and l-enantiomers of amino acids from local interstitial fluid in the rat submandibular gland. The proportion of the d-form of serine in interstitial fluid was higher than that in plasma or saliva. Perfusion of the rat submandibular gland with d-serine and l-glutamic acid via the submandibular gland artery resulted in a significant increase in salivary secretion after stimulation of muscarinic receptors with carbachol. In vivo microdialysis applied to the submandibular glands of rats showed that infusion of d-serine along with l-glutamate through the microdialysis probe significantly elevated acetylcholine levels in local interstitial fluids in the submandibular glands of anesthetized rats as compared to that with l-glutamate alone in an N-methyl-d-aspartate receptor glycine site antagonist-sensitive manner. These results indicate that d-serine augments salivary secretion by increasing acetylcholine release in the salivary glands.
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Affiliation(s)
- Masanobu Yoshikawa
- Department of Clinical Pharmacology, School of Medicine, Tokai University, Isehara 259-1193, Japan
| | - Migiwa Okubo
- Kawano Dental Clinic, Yachimata 289-1101, Japan;
| | - Kosuke Shirose
- Department of Anesthesiology, School of Medicine, Tokai University, Isehara 259-1193, Japan; (K.S.); (T.K.)
| | - Takugi Kan
- Department of Anesthesiology, School of Medicine, Tokai University, Isehara 259-1193, Japan; (K.S.); (T.K.)
| | - Mitsuru Kawaguchi
- Tokyo Dental College, Misaki-cho, Chiyoda-ku, Tokyo 101-0061, Japan;
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Park DK, Petshow S, Anisimova M, Barragan EV, Gray JA, Stein IS, Zito K. Reduced d-serine levels drive enhanced non-ionotropic NMDA receptor signaling and destabilization of dendritic spines in a mouse model for studying schizophrenia. Neurobiol Dis 2022; 170:105772. [PMID: 35605760 PMCID: PMC9352378 DOI: 10.1016/j.nbd.2022.105772] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 05/15/2022] [Accepted: 05/16/2022] [Indexed: 10/31/2022] Open
Abstract
Schizophrenia is a psychiatric disorder that affects over 20 million people globally. Notably, schizophrenia is associated with decreased density of dendritic spines and decreased levels of d-serine, a co-agonist required for opening of the N-methyl-d-aspartate receptor (NMDAR). We hypothesized that lowered d-serine levels associated with schizophrenia would enhance ion flux-independent signaling by the NMDAR, driving destabilization and loss of dendritic spines. We tested our hypothesis using the serine racemase knockout (SRKO) mouse model, which lacks the enzyme for d-serine production. We show that activity-dependent spine growth is impaired in SRKO mice, but can be acutely rescued by exogenous d-serine. Moreover, we find a significant bias of synaptic plasticity toward spine shrinkage in the SRKO mice as compared to wild-type littermates. Notably, we demonstrate that enhanced ion flux-independent signaling through the NMDAR contributes to this bias toward spine destabilization, which is exacerbated by an increase in synaptic NMDARs in hippocampal synapses of SRKO mice. Our results support a model in which lowered d-serine levels associated with schizophrenia enhance ion flux-independent NMDAR signaling and bias toward spine shrinkage and destabilization.
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