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)

Schizophrenia is associated with abnormalities in glucose metabolism that may lead to insulin resistance and a 3 fold higher incidence of type II diabetes mellitus. The goal of the present studies was to assess the role of insulin-dependent Akt signaling in schizophrenia and in animal and cellular models of insulin resistance. Our studies revealed a functional decrease in insulin receptor (IR)-mediated signal transduction in the dorsolateral prefrontal cortex (BA46) of medicated schizophrenics relative to control patients using post-mortem brain material. We found approximately 50% decreases in the content and autophosphorylation levels of IRbeta and approximately 76-78% decreases in Akt content and activity (pSer(473)-Akt). The inhibition of IRbeta signaling was accompanied by an elevated content of glycogen synthase kinase (GSK)-3 alpha and GSK-3beta without significant changes in phospho-Ser(21/9) GSK-3 alpha/beta levels. A cellular model of insulin resistance was induced by IRbeta knockdown (siRNA). As in schizophrenia, the IRbeta knockdown cells demonstrated a reduction in the Akt content and activity. Total GSK-3 alpha/beta content remained unaltered, but phospho-Ser(21/9) GSK-3 alpha/beta levels were reduced indicating a net increase in the overall enzyme activity similar to that in schizophrenia. Insulin resistance phenotype was induced in mice by treatment with antipsychotic drug, clozapine. Behavioral testing showed decreases in startle response magnitude in animals treated with clozapine for 68 days. The treatment resulted in a functional inhibition of IRbeta but the Akt activation status remained unaltered. Changes in GSK-3 alpha/beta were consistent with a net decrease in the enzyme activity, as opposed to that in schizophrenia. The results suggest that alterations in insulin-dependent Akt signaling in schizophrenia are similar to those observed in our cellular but not animal models of insulin resistance. In animal model, clozapine ameliorates IRbeta deficits at the GSK-3 alpha/beta level, which may justify its role in treatment of schizophrenia. Our studies suggest that aberrant IR function may be important in the pathophysiology of schizophrenia.
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PMID:Insulin receptor deficits in schizophrenia and in cellular and animal models of insulin receptor dysfunction. 1658 Dec 31

AKT-glycogen synthase kinase 3beta (GSK3beta) signaling is a target of lithium and has been implicated in the pathogenesis of mood disorders and schizophrenia. AKT1 protein level is decreased in the peripheral lymphocytes and brains of schizophrenic patients. The SNP2/3/4 TCG haplotype of AKT1 was associated with schizophrenia in patients with Northern European origin. In the present study, we genotyped five single nucleotide polymorphisms (SNP1-5) of AKT1 gene according to the original study in Iranians comprising of 321 schizophrenic patients and 383 controls, all residing in Mashhad city, Northeastern Iran. Haplotype analysis showed that the frequency of a five-SNP haplotype (AGCAG) was significantly higher in schizophrenic patients (0.068) than that of controls (0.034) (P = 0.03 after Bonferroni correction, OR = 2.04, CI = 1.2-3.4). In stratified analysis by schizophrenia subtypes, the frequency of the same haplotype was significantly higher in disorganized subtype (n = 78, frequency of haplotype=0.081) when compared with normal controls (P = 0.04 after Bonferroni correction, OR = 2.59, CI = 1.3-5.2). Our findings did not confirm the association of AKT1 SNP2/3/4 TCG haplotype with the risk of schizophrenia as reported in the original study but showed the evidence of association with a different haplotype, AKT1 five-SNP AGCAG haplotype, with the risk of schizophrenia in Iranian population.
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PMID:Association of AKT1 haplotype with the risk of schizophrenia in Iranian population. 1658 35

Glycogen synthase kinase-3 (GSK3) has been recognized as an important enzyme that modulates many aspects of neuronal function. Accumulating evidence implicates abnormal activity of GSK3 in mood disorders and schizophrenia, and GSK3 is a potential protein kinase target for psychotropics used in these disorders. We previously reported that serotonin, a major neurotransmitter involved in mood disorders, regulates GSK3 by acutely increasing its N-terminal serine phosphorylation. The present study was undertaken to further determine if atypical antipsychotics, which have therapeutic effects in both mood disorders and schizophrenia, can regulate phospho-Ser-GSK3 and inhibit its activity. The results showed that acute treatment of mice with risperidone rapidly increased the level of brain phospho-Ser-GSK3 in the cortex, hippocampus, striatum, and cerebellum in a dose-dependent manner. Regulation of phospho-Ser-GSK3 was a shared effect among several atypical antipsychotics, including olanzapine, clozapine, quetiapine, and ziprasidone. In addition, combination treatment of mice with risperidone and a monoamine reuptake inhibitor antidepressant imipramine or fluoxetine elicited larger increases in brain phospho-Ser-GSK3 than each agent alone. Taken together, these results provide new information suggesting that atypical antipsychotics, in addition to mood stabilizers and antidepressants, can inhibit the activity of GSK3. These findings may support the pharmacological mechanisms of atypical antipsychotics in the treatment of mood disorders.
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PMID:Regulation of mouse brain glycogen synthase kinase-3 by atypical antipsychotics. 1678 49

Historically, success in the pharmacological treatment of bipolar disorder has arisen either from serendipitous findings or from studies with drugs (antipsychotics and anticonvulsants) developed for other indications (schizophrenia and epilepsy, respectively). Lithium has been in widespread clinical use in the treatment of bipolar disorder for > 30 years. Development of lithium-mimetic compounds has the potential to result in a more specific medication, with fewer side effects and a less narrow dose range. However, novel medications based upon a known mechanism of action of this drug are yet to be developed. Increasing evidence suggests that a next-generation lithium compound may derive from knowledge of a direct target of lithium, glycogen synthase kinase-3 (GSK-3). GSK-3 is an intracellular enzyme implicated as a critical component in many neuronal signalling pathways. However, despite the large body of preclinical data discussed in this review, definitive validation of GSK-3 as therapeutically relevant target of lithium will require clinical trials with novel GSK-3 inhibitors. A number of recent reports suggest that it is possible to develop selective, small-molecule GSK-3 inhibitors.
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PMID:Targeting glycogen synthase kinase-3 as an approach to develop novel mood-stabilising medications. 1670 78

The objective of this review is to identify a target or biomarker of altered neurochemical sensitivity that is common to the many animal models of human psychoses associated with street drugs, brain injury, steroid use, birth injury, and gene alterations. Psychosis in humans can be caused by amphetamine, phencyclidine, steroids, ethanol, and brain lesions such as hippocampal, cortical, and entorhinal lesions. Strikingly, all of these drugs and lesions in rats lead to dopamine supersensitivity and increase the high-affinity states of dopamine D2 receptors, or D2High, by 200-400% in striata. Similar supersensitivity and D2High elevations occur in rats born by Caesarian section and in rats treated with corticosterone or antipsychotics such as reserpine, risperidone, haloperidol, olanzapine, quetiapine, and clozapine, with the latter two inducing elevated D2High states less than that caused by haloperidol or olanzapine. Mice born with gene knockouts of some possible schizophrenia susceptibility genes are dopamine supersensitive, and their striata reveal markedly elevated D2High states; suchgenes include dopamine-beta-hydroxylase, dopamine D4 receptors, G protein receptor kinase 6, tyrosine hydroxylase, catechol-O-methyltransferase, the trace amine-1 receptor, regulator of G protein signaling RGS9, and the RIIbeta form of cAMP-dependent protein kinase (PKA). Striata from mice that are not dopamine supersensitive did not reveal elevated D2High states; these include mice with knockouts of adenosine A2A receptors, glycogen synthase kinase GSK3beta, metabotropic glutamate receptor 5, dopamine D1 or D3 receptors, histamine H1, H2, or H3 receptors, and rats treated with ketanserin or aD1 antagonist. The evidence suggests that there are multiple pathways that convergetoelevate the D2High state in brain regions and that this elevation may elicit psychosis. This proposition is supported by the dopamine supersensitivity that is a common feature of schizophrenia and that also occurs in many types of genetically altered, drug-altered, and lesion-altered animals. Dopamine supersensitivity, in turn, correlates with D2High states. The finding that all antipsychotics, traditional and recent ones, act on D2High dopamine receptors further supports the proposition.
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PMID:Psychosis pathways converge via D2high dopamine receptors. 1678 61

The protein kinase v-akt murine thymoma viral oncogene homolog (AKT) gene family comprises three human homologs that phosphorylate and inactivate glycogen synthase kinase 3beta (GSK3beta). Studies have reported the genetic association of AKT1 with schizophrenia. Additionally, decreased AKT1 protein expression and the reduced phosphorylation of GSK3beta were reported in this disease, leading to a new theory of attenuated AKT1-GSK3beta signaling in schizophrenia pathogenesis. We have evaluated this theory by performing both genetic and protein expression analyses. A family based association test of AKT1 did not show association with schizophrenia in Japanese subjects. The expression levels of total AKT, AKT1 and phosphorylated GSK3beta detected in the schizophrenic brains from two different brain banks also failed to support the theory. In addition, no attenuated AKT-GSK3beta signaling was observed in the lymphocytes from Japanese schizophrenics, contrasting with previous findings. Importantly, we found that the level of phosphorylated GSK3beta at Ser9 tended to be inversely correlated with postmortem intervals, and that the phosphorylation levels of AKT were inversely correlated with brain pH, issues not assessed in the previous study. These data introduce a note of caution when estimating the phosphorylation levels of GSK3beta and AKT in postmortem brains. Collectively, this study failed to support reduced signaling of the AKT-GSK3beta molecular cascade in schizophrenia.
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PMID:Failure to support a genetic contribution of AKT1 polymorphisms and altered AKT signaling in schizophrenia. 1698 50

The analysis of submicroscopic copy number variations (CNVs), also known as copy number polymorphisms (CNPs), is emerging as a new tool for understanding the genetic basis of cancer, developmental disorders, and complex traits. One area where this may be particularly useful is in the identification of genetic variants underlying schizophrenia (SZ) and bipolar disorder (BD). Linkage analysis and pharmacological studies carried out over the past decade have implicated a number of positional and physiological candidate genes. Yet, despite extensive analysis, the underlying allelic variants responsible for disease susceptibility have remained, largely, elusive. Although the borders of most CNV have not been precisely mapped, it appears that a considerable number of SZ and BD candidate genes have their coding elements disrupted by polymorphic CNVs, suggesting that these would be good variants to consider for underlying disease susceptibility. One such gene is GSK3beta, which codes for glycogen synthase kinase, a key component of the Wnt signaling pathway and a target of lithium salts. A CNV in the GSK3beta locus at chromosome 3q13.3 appears to disrupt the gene's 3'-coding elements. The CNV also affects two other annotated genes. We now report that patients with BD have an increased frequency of this CNV-primarily the duplication variant-compared with controls (P = 0.002). The finding suggests that GSK3beta may be involved in BD susceptibility in some individuals and that CNVs in this and other candidate genes for psychiatric disorders should be analyzed as causative functional genetic variants.
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PMID:Increase in GSK3beta gene copy number variation in bipolar disorder. 1735 45

The GSK-3 beta gene encodes a protein kinase which is abundant in the brain, and its product is involved in signal transduction cascades of neuronal cell development, energy metabolism and body pattern formation. Previous studies have suggested that GSK-3 beta might act as a potential candidate locus for schizophrenia susceptibility. We genotyped six SNPs within the gene and conducted a case-control study involving 329 schizophrenic patients and 288 healthy subjects in the Chinese population. We examined allele and genotype frequencies and haplotype distributions in the subtype of paranoid schizophrenic patients as well as schizophrenic subjects in general. Our results fail to replicate the association of the GSK-3 beta gene with susceptibility to schizophrenia in the Chinese population.
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PMID:No significant association between the genetic polymorphisms in the GSK-3 beta gene and schizophrenia in the Chinese population. 1736 86

Protein kinase B (Akt), glycogen synthase kinase-3 (GSK-3) and members of the Wnt signal transduction pathway were recently found to be altered in schizophrenia and targeted by antipsychotic drugs. In the current study, selected Wnt signalling proteins were investigated to determine if they are altered by the antipsychotics clozapine or haloperidol in the rat prefrontal cortex. Pheochromocytoma (PC12) and neuroblastoma (SH-SY5Y) cells were also used to elucidate how antipsychotics generated the pattern of changes observed in vivo. Western blotting (WB) revealed that treatment with haloperidol or clozapine caused an up-regulation of Wnt-5a, dishevelled-3, Axin, total and phosphorylated GSK-3 and beta-catenin protein levels. Treatment of PC12 and SH-SY5Y cells with a variety of pharmacological agents as well as the over-expression of several Wnt related proteins failed to mimic the pattern observed in vivo following antipsychotic treatment. However, the over-expression of dishevelled-3 nearly perfectly duplicated the changes observed in vivo. Immunoprecipitations (IP) conducted using protein isolated from the rat prefrontal cortex indicated that dishevelled-3 is associated with the D2 dopamine receptor thereby suggesting that antipsychotics may act on dishevelled-3 via D2 dopamine receptors to initiate a cascade of downstream changes involving Axin, GSK-3 and beta-catenin that may help to alleviate psychosis in schizophrenic patients.
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PMID:Activation of the canonical Wnt pathway by the antipsychotics haloperidol and clozapine involves dishevelled-3. 1747 3

Par-4 has been suggested to mediate dopamine neurotransmission. Dopamine D2 receptor (DRD2) activation induces a signalling complex of AKT1, PP2A and beta-arrestin2 which dephosphorylates/inactivates AKT1 thereby activating GSK-3beta, transducing dopamine-dependent behaviour. DRD2 activation also results in down-regulation of PKA activity. Among other substrates PKA phosphorylates GSK-3beta. Prolonged DRD2 activation leads to its 'desensitization' which involves GRKs and beta-arrestins. beta-arrestin1 binds to phosphorylated receptors preventing further G-protein stimulation. This study examined whether Par-4, beta-arrestin1, AKT1 and GSK-3beta are involved in the pathophysiology of schizophrenia. Lymphocytes obtained from schizophrenia and bipolar patients and healthy controls recruited from the Beer-Sheva Mental Health Center were transformed by Epstein-Barr virus (EBV) into lymphocyte-derived cell lines (LDCL). Post-mortem brain samples were obtained from the Rebecca L. Cooper Brain Bank, Parkville, Australia. The study was approved by the IRB committees of Beer-Sheva, Israel and Parkville, Australia. Levels of the specific proteins were assayed by Western blotting. beta-arrestin1 protein levels were significantly ~2-fold increased in LDCL from schizophrenia patients while Par-4 protein levels were unaltered. A 63% significant decrease was found in frontal cortex phospho-Ser9-GSK-3beta protein levels in schizophrenia but not in those of AKT1, Par-4 or beta-arrestin1. Elevated beta-arrestin1 protein levels in LDCL and decreased phospho-Ser9-GSK-3beta protein levels in post-mortem frontal cortex of schizophrenia patients vs. control groups support the possible involvement of these proteins in the pathophysiology of schizophrenia. However, since we did not find differences in beta-arrestin1, AKT1 and Par-4 protein levels in post-mortem frontal cortex of schizophrenia patients and although GSK-3beta participates in other signalling cascades we can not rule out the possibility that the differences found reflect deviation in DRD2 signalling.
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PMID:Possible involvement of post-dopamine D2 receptor signalling components in the pathophysiology of schizophrenia. 1768 Oct 85


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