Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Accumulating evidence from both genetic and clinico-pharmacological studies suggests that D-serine, an endogenous coagonist to the NMDA subtype glutamate receptor, may be implicated in schizophrenia (SZ). Although an association of genes for D-serine degradation, such as D-amino acid oxidase and G72, has been reported, a role for D-serine in SZ has been unclear. In this study, we identify and characterize protein interacting with C-kinase (PICK1) as a protein interactor of the D-serine synthesizing enzyme, serine racemase (SR). The binding of endogenous PICK1 and SR requires the PDZ domain of PICK1. The gene coding for PICK1 is located at chromosome 22q13, a region frequently linked to SZ. In a case-control association study using well-characterized Japanese subjects, we observe an association of the PICK1 gene with SZ, which is more prominent in disorganized SZ. Our findings implicating PICK1 as a susceptibility gene for SZ are consistent with a role for D-serine in the disease.
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PMID:Serine racemase binds to PICK1: potential relevance to schizophrenia. 1631 70

D-Serine is a co-agonist at the NMDA receptor glycine-binding site. Early studies have emphasized a glial localization for D-serine. However the nature of the glial cells has not been fully resolved, because previous D-serine antibodies needed glutaraldehyde-fixation, precluding co-localization with fixation-sensitive antigens. We have raised a new D-serine antibody optimized for formaldehyde-fixation. Light and electron microscopic observations indicated that D-serine was concentrated into vesicle-like compartments in astrocytes and radial glial cells, rather than being distributed uniformly in the cytoplasm. In aged animals, patches of cortex and hippocampus were devoid of immunolabeling for D-serine, suggesting that impaired glial modulation of forebrain glutamatergic signaling might occur. Dual immunofluorescence labeling for glutamate and D-serine revealed D-serine in a subset of glutamatergic neurons, particularly in brainstem regions and in the olfactory bulbs. Microglia also contain D-serine. We suggest that some D-serine may be derived from the periphery. Collectively, our data suggest that the cellular compartmentation and distribution of D-serine may be more complex and extensive than previously thought and may have significant implications for our understanding of the role of D-serine in disease states including hypoxia and schizophrenia.
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PMID:Immunocytochemical analysis of D-serine distribution in the mammalian brain reveals novel anatomical compartmentalizations in glia and neurons. 1634 69

D-Amino acid oxidase (DAAO) has been proposed to be involved in the oxidation of D-serine, an allosteric activator of the NMDA-type glutamate receptor in the brain, and to be associated with the onset of schizophrenia. The recombinant human DAAO was expressed in Escherichia coli and was isolated as an active homodimeric flavoenzyme. It shows the properties of the dehydrogenase-oxidase class of flavoproteins, possesses a low kinetic efficiency, and follows a ternary complex (sequential) kinetic mechanism. In contrast to the other known DAAOs, the human enzyme is a stable homodimer even in the apoprotein form and weakly binds the cofactor in the free form.
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PMID:Characterization of human D-amino acid oxidase. 1661 39

With the exception of dementia, the use of neuroprotective agents in psychiatric disorders is not yet well established. However, recent data from brain imaging studies and clinical trials support the view that neurodegenerative mechanisms may play a role in the pathophysiology of schizophrenia and affective disorders. Further evidence for the use of neuroprotective agents can be drawn from the findings that second-generation antipsychotics, mood stabilizers and antidepressants have been shown to have neuroprotective effects in vitro and in vivo. Neuroprotective agents as add-on therapies (e.g., modafinil, erythropoietin, glycine, D-serine, memantine and celecoxib) are currently being evaluated in schizophrenia and related disorders. This paper reviews the current options for neuroprotective treatment approaches focusing on schizophrenia and affective disorders.
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PMID:Neuroprotective agents in schizophrenia and affective disorders. 1663 7

It has been proposed that glutamatergic transmission, in particular NMDA receptor function, might be altered in schizophrenia. This hypothesis is mainly based on the observation that uncompetitive NMDA receptor antagonists, e.g. phencyclidine, evoke psychotic symptoms in healthy subjects, whereas agonists interacting at the glycine site of the NMDA receptor complex, e.g. glycine or D-serine, administered jointly with typical neuroleptics, can alleviate schizophrenic symptoms. The function of NMDA receptors may be modulated by group I mGluRs (mGluR1 and mGluR5), which have also been shown to be altered in schizophrenia. In rodents, mGluR5 antagonists, but not mGluR1 ones, potentiate the locomotor activity and the deficit of prepulse inhibition (PPI) induced by uncompetitive NMDA receptor antagonists. These antagonists (of either type) administered alone are not active in the above tests. Hence, antagonists of mGluR1 and mGluR5 may evoke different effects on the NMDA receptor antagonists-induced behavior and, possibly, on schizophrenic symptoms.
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PMID:The role of group I metabotropic glutamate receptors in schizophrenia. 1669 16

Non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist administration induces a syndrome indistinguishable from schizophrenia including positive and negative symptoms and cognitive deficits. Concordantly, augmentation of the NMDA receptor function by glycine-site agonists such as D-serine and D-cycloserine has been reported to improve negative symptoms and some cognitive deficits in schizophrenia patients when added to conventional antipsychotic treatment, although they appear less effective when combined with clozapine specifically. In contrast, administration of the AMPAkine CX-516 (which positively modulate the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor) as an adjuvant to clozapine, has been shown to exert some beneficial action on the negative symptoms and cognitive deficits in schizophrenia. In the rat, selective suppression of conditioned avoidance response (CAR) behaviour has been widely reported to be a test with high predictive validity for antipsychotic efficacy. We found that D-serine and CX-516, at doses ineffective by themselves, significantly potentiated the suppression of CAR induced by threshold doses of risperidone (0.16 mg/kg, s.c.), olanzapine (0.63 mg/kg, s.c.) and clozapine (1.3 mg/kg, s.c.) without causing additional motor disturbances. Thus, the adjunct enhancement of NMDA or AMPA receptor function observed clinically, appears reflected in the present rat CAR study. Consequently, our data lend further support to the potential use of the CAR test in the investigation of augmentation strategies involving the addition of non-dopaminergic target compounds to existing atypical antipsychotics.
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PMID:Positive modulation of glutamatergic receptors potentiates the suppressive effects of antipsychotics on conditioned avoidance responding in rats. 1678 80

Evidence of glutamatergic dysfunction in schizophrenia associated with the N-methyl-D-aspartate receptor has historically demonstrated changes primarily attributable to neurons. We propose an astrocytic component to N-methyl-D-aspartate receptor dysfunction in this illness. We studied the expression of serine racemase, an astrocytic enzyme which synthesizes the N-methyl-D-aspartate receptor coagonist D-serine, using Western blot analysis in postmortem hippocampus and cortex in schizophrenia and a comparison group. We found increased expression in the hippocampus in schizophrenia. This is the first study to demonstrate alterations in schizophrenia of an astrocytic enzyme responsible for synthesizing a neuromodulator, and further evidence that astrocytes may play a direct role in N-methyl-D-aspartate receptor dysfunction in schizophrenia.
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PMID:Serine racemase protein expression in cortex and hippocampus in schizophrenia. 1683 50

D-amino acid oxidase (DAO) degrades D-serine, a co-agonist at the NMDA receptor (NMDAR). Hypofunction of the NMDAR has been suggested to contribute to the pathophysiology of schizophrenia. Intriguingly, DAO has been recently identified as a risk factor for schizophrenia through genetic association studies. A naturally occurring mouse strain (ddY/DAO-) has been identified which lacks DAO activity. We have characterized this strain both behaviorally and biochemically to evaluate DAO as a target for schizophrenia. We have confirmed that this strain lacks DAO activity and shown for the first time it has increased occupancy of the NMDAR glycine site due to elevated extracellular D-serine levels and has enhanced NMDAR function in vivo. Furthermore, the ddY/DAO- strain displays behaviors which suggest that it will be a useful tool for evaluation of the clinical benefit of DAO inhibition in schizophrenia.
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PMID:Behavioral and biochemical characterization of a mutant mouse strain lacking D-amino acid oxidase activity and its implications for schizophrenia. 1684 4

Cognitive dysfunction in schizophrenia differs from cognitive dysfunction in neurodegenerative illnesses because it is associated with neuronal dysfunction and not neurodegeneration. Pharmacologically, potential targets for developing treatments may differ from cognition in dementing disorders. Several putative molecular targets for treating cognition in schizophrenia show promise, such as treatments that act on the D(1) receptor of the dopamine system; the 5HT(1A), 5HT(2A), and 5HT(6), receptors of the serotonin system; and ampakines, Glycine/D-cycloserine, D-serine, and mGluR 2/3 agonists of the glutamatergic system. Other receptors associated with improvement in cognition include nicotinic and muscarinic receptors, and the alphalpha2 subunit receptor of the brain GABA system. Domain treatment of schizophrenia is a new method of treating schizophrenia that involves treating a single domain of dysfunction at a time.
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PMID:The neurobiology of cognition in schizophrenia. 1708 Oct 78

In the brain, the extensively studied FAD-dependent enzyme D-amino acid oxidase (DAO) degrades the gliotransmitter D-serine, a potent activator of N-methyl-D-aspartate type glutamate receptors, and evidence suggests that DAO, together with its activator G72 protein, may play a key role in the pathophysiology of schizophrenia. Indeed, its potential clinical importance highlights the need for structural and functional analyses of human DAO. We recently succeeded in purifying human DAO, and found that it weakly binds FAD and shows a significant slower rate of flavin reduction compared with porcine DAO. However, the molecular basis for the different kinetic features remains unclear because the active site of human DAO was considered to be virtually identical to that of porcine DAO, as would be expected from the 85% sequence identity. To address this issue, we determined the crystal structure of human DAO in complex with a competitive inhibitor benzoate, at a resolution of 2.5 Angstrom. The overall dimeric structure of human DAO is similar to porcine DAO, and the catalytic residues are fully conserved at the re-face of the flavin ring. However, at the si-face of the flavin ring, despite the strict sequence identity, a hydrophobic stretch (residues 47-51, VAAGL) exists in a significantly different conformation compared with both of the independently determined porcine DAO-benzoate structures. This suggests that a context-dependent conformational variability of the hydrophobic stretch accounts for the low affinity for FAD as well as the slower rate of flavin reduction, thus highlighting the unique features of the human enzyme.
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PMID:Crystal structure of human D-amino acid oxidase: context-dependent variability of the backbone conformation of the VAAGL hydrophobic stretch located at the si-face of the flavin ring. 1708 22


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