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Tanaka M, Watanabe Y. RNA Editing of Serotonin 2C Receptor and Alcohol Intake. Front Neurosci 2020; 13:1390. [PMID: 32009879 PMCID: PMC6971223 DOI: 10.3389/fnins.2019.01390] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 12/10/2019] [Indexed: 01/30/2023] Open
Abstract
Serotonin 2C receptor (5-HT2 CR) belongs to the superfamily of seven transmembrane domain receptors coupled to G proteins (GPCR). It is broadly distributed in the CNS and its expression is relatively high in the limbic system including the amygdala, nucleus accumbens (NAc), hippocampus, and hypothalamus. Based on its expression patterns and numerous pharmacological studies, 5-HT2 CR is thought to be involved in various brain functions including emotion, appetite, and motor behavior. Here, we review 5-HT2 CR and its relationship with alcohol intake with a particular focus on the involvement of 5-HT2 CR mRNA editing and its association with alcohol preference in mice. RNA editing is a post-transcriptional modification mechanism. In mammals, adenosine is converted to inosine by the deamination enzymes ADAR1 and ADAR2. 5-HT2 CR is the only GPCR subjected to RNA editing within the coding region. It has five editing sites in exon 5 that encode the second intracellular loop. Consequently, three amino acids residues (I156, N158, and I160) of the unedited receptor (INI) may be altered to differently edited isoforms, resulting in a change of receptor activity such as 5-HT potency and G-protein coupling. 5-HT2 CR in the NAc is involved in enhanced alcohol drinking after chronic alcohol exposure and alterations in 5-HT2 CR mRNA editing is important in determining the alcohol preference using different strains of mice and genetically modified mice. RNA editing of this receptor may participate in the development of alcoholism.
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Affiliation(s)
- Masaki Tanaka
- Department of Anatomy and Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yoshihisa Watanabe
- Department of Basic Geriatrics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
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Kubota-Sakashita M, Iwamoto K, Bundo M, Kato T. A role of ADAR2 and RNA editing of glutamate receptors in mood disorders and schizophrenia. Mol Brain 2014; 7:5. [PMID: 24443933 PMCID: PMC3902024 DOI: 10.1186/1756-6606-7-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 01/09/2014] [Indexed: 01/04/2023] Open
Abstract
Background Pre-mRNAs of 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)-propanoic acid (AMPA)/kainate glutamate receptors undergo post-transcriptional modification known as RNA editing that is mediated by adenosine deaminase acting on RNA type 2 (ADAR2). This modification alters the amino acid sequence and function of the receptor. Glutamatergic signaling has been suggested to have a role in mood disorders and schizophrenia, but it is unknown whether altered RNA editing of AMPA/kainate receptors has pathophysiological significance in these mental disorders. In this study, we found that ADAR2 expression tended to be decreased in the postmortem brains of patients with schizophrenia and bipolar disorder. Results Decreased ADAR2 expression was significantly correlated with decreased editing of the R/G sites of AMPA receptors. In heterozygous Adar2 knockout mice (Adar2+/− mice), editing of the R/G sites of AMPA receptors was decreased. Adar2+/− mice showed a tendency of increased activity in the open-field test and a tendency of resistance to immobility in the forced swimming test. They also showed enhanced amphetamine-induced hyperactivity. There was no significant difference in amphetamine-induced hyperactivity between Adar2+/− and wild type mice after the treatment with an AMPA/kainate receptor antagonist, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline. Conclusions These findings collectively suggest that altered RNA editing efficiency of AMPA receptors due to down-regulation of ADAR2 has a possible role in the pathophysiology of mental disorders.
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Affiliation(s)
| | | | | | - Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
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O'Neil RT, Emeson RB. Quantitative analysis of 5HT(2C) receptor RNA editing patterns in psychiatric disorders. Neurobiol Dis 2011; 45:8-13. [PMID: 21914481 DOI: 10.1016/j.nbd.2011.08.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/19/2011] [Accepted: 08/26/2011] [Indexed: 02/06/2023] Open
Abstract
Initially identified as an RNA modification in the anticodon loop of tRNAs from animal, plant and eubacterial origin, the deamination of adenosine-to-inosine by RNA editing has become increasingly recognized as an important RNA processing event to generate diversity in both the transcriptome and proteome and is essential for modulating the activity of numerous proteins critical for nervous system function. Here, we focus on the editing of transcripts encoding the 2C-subtype of serotonin receptor (5HT(2C)) to generate multiple receptor isoforms that differ in G-protein coupling efficacy and constitutive activity. 5HT(2C) receptors have been implicated in the regulation of anxiety, components of the stress response, and are thought to play a role in compulsive behavioral disorders, depression and drug addiction. A number of studies have been conducted to assess whether 5HT(2C) editing is altered in individuals suffering from psychiatric disorders, yet the results from these studies have been inconsistent, and thus inconclusive. This review provides a discussion of the challenges involved with characterizing 5HT(2C) editing patterns in human postmortem tissue samples and how differences in quantitative methodology have contributed to the observed inconsistencies between multiple laboratories. Additionally, we discuss new high-throughput sequencing tools, which provide an opportunity to overcome previous methodological challenges, and permit reliable systematic analyses of RNA editing in control and pathologic disease states.
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Affiliation(s)
- Richard T O'Neil
- Center for Molecular Neuroscience, Molecular Physiology & Biophysics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232-8548, USA
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Iwamoto K, Bundo M, Kasai K, Kato T. Measuring RNA editing of serotonin 2C receptor. BIOCHEMISTRY (MOSCOW) 2011; 76:912-914. [DOI: 10.1134/s0006297911080062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
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Bundo M, Iwamoto K, Yamada K, Yoshikawa T, Kato T. Mutation screening and assessment of the effect of genetic variations on expression and RNA editing of serotonin receptor 2C in the human brain. Psychiatry Clin Neurosci 2010; 64:57-61. [PMID: 20015120 DOI: 10.1111/j.1440-1819.2009.02046.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Serotonin receptor 2C (HTR2C) has been postulated as being involved in the etiology or pathophysiology of mental disorders such as bipolar disorder, major depression and schizophrenia. We previously revealed the altered mRNA expression and RNA editing of HTR2C in the postmortem brains of patients with mental disorders. Here we examined the relationship between genetic variations and expression level or RNA editing level of HTR2C in the human brain. METHODS We performed mutation screening of the HTR2C gene by sequencing all exons, exon-intron boundaries, and promoter region in the same cohort used for expression and RNA editing studies (n = 58). Using the detected genetic variations, we examined the relationship between genetic variations and expression or RNA editing level. RESULTS AND CONCLUSION We did not find novel mutations or single nucleotide polymorphisms that were specific to patients. Genotype and haplotype-based analyses revealed that genetic variations of HTR2C did not account for observed altered expression or RNA editing level of HTR2C in the brain.
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Affiliation(s)
- Miki Bundo
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Saitama, Japan
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Werry TD, Loiacono R, Sexton PM, Christopoulos A. RNA editing of the serotonin 5HT2C receptor and its effects on cell signalling, pharmacology and brain function. Pharmacol Ther 2008; 119:7-23. [DOI: 10.1016/j.pharmthera.2008.03.012] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 03/10/2008] [Indexed: 01/05/2023]
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IWAMOTO K, KATO T. RNA Editing of Serotonin 2C Receptor and Major Mental Disorders. YAKUGAKU ZASSHI 2008; 128:521-5. [DOI: 10.1248/yakushi.128.521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Kazuya IWAMOTO
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute
| | - Tadafumi KATO
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute
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Iwamoto K, Nakatani N, Bundo M, Yoshikawa T, Kato T. Altered RNA editing of serotonin 2C receptor in a rat model of depression. Neurosci Res 2005; 53:69-76. [PMID: 16005997 DOI: 10.1016/j.neures.2005.06.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2005] [Revised: 05/13/2005] [Accepted: 06/06/2005] [Indexed: 11/20/2022]
Abstract
Altered RNA editing of serotonin 2C receptor (HTR2C) has been suggested to be involved in the pathophysiology of major depression. Here we examined RNA editing status of HTR2C in the learned helplessness (LH) rats, one of well-established animal models of depression. LH rats showed the significantly increased RNA editing of site E, and tendency for increased RNA editing of other editing sites. Treatment with fluoxetine, a selective serotonin reuptake inhibitor, or imipramine, a tricyclic antidepressant, affected the RNA editing status of the LH rats. Although, these antidepressants differentially altered RNA editing status, they commonly reduced RNA editing efficiency of site E. We further revealed that altered RNA editing in the LH rats and by antidepressants was not explained by altered expression of RNA editing enzymes or their substrates (adenosine deaminases that act on RNA, HTR2C, and spliced form of HTR2C). These results suggest that alteration of RNA editing of HTR2C may play a role in the pathophysiology of depression and action of antidepressants.
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Affiliation(s)
- Kazuya Iwamoto
- Laboratory for Molecular Dynamics of Mental Disorders, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako city, Saitama 351 0198, Japan.
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Iwamoto K, Bundo M, Kato T. Estimating RNA editing efficiency of five editing sites in the serotonin 2C receptor by pyrosequencing. RNA (NEW YORK, N.Y.) 2005; 11:1596-603. [PMID: 16199765 PMCID: PMC1370844 DOI: 10.1261/rna.2114505] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Accumulating evidence suggests that altered RNA editing of the serotonin 2C receptor (HTR2C) is involved in the pathophysiology of mental disorders and the action of antidepressants. Estimating RNA editing of HTR2C in various samples is a first step to understanding its pathophysiological roles. Here, we developed a high-throughput quantification method of RNA editing efficiency by pyrosequencing. By optimizing the dispensation order, the RNA editing efficiency of all five RNA editing sites including consecutively ordered sites in HTR2C was obtained. More importantly, our method made it possible to determine the content of partial HTR2C isoforms, which enabled us to monitor possible functional changes of HTR2C. This method was validated in both oligonucleotide and RT-PCR product templates, and showed good correlation with conventional cloning-sequencing analysis. Our method could be a valuable tool in the rapid assessment of RNA editing status, including assessment of natural variations, alterations in disease tissues, and responses to drugs.
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Affiliation(s)
- Kazuya Iwamoto
- Laboratory for Molecular Dynamics of Mental Disorders, Brain Science Institute, RIKEN, Wako-city, Saitama 351-0198, Japan.
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Schmauss C. Regulation of serotonin 2C receptor pre-mRNA editing by serotonin. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 63:83-100. [PMID: 15797466 DOI: 10.1016/s0074-7742(05)63004-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Claudia Schmauss
- Department of Psychiatry and Neuroscience, Columbia University College of Physicians & Surgeons and New York State Psychiatric Institute New York, New York 10032, USA
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Iwamoto K, Kato T. RNA editing of serotonin 2C receptor in human postmortem brains of major mental disorders. Neurosci Lett 2003; 346:169-72. [PMID: 12853111 DOI: 10.1016/s0304-3940(03)00608-6] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The importance of serotonin 2C receptor (HTR2C) in mental disorders has been implicated by studies of HTR2C-deficient mice and linkage and association studies. Recent studies have revealed that RNA editing of HTR2C is involved in mental disorders. Here we examined RNA editing efficiencies of site A and D of HTR2C in the prefrontal cortex samples of patients with bipolar disorder, schizophrenia, and major depression as well as control subjects by using primer extension combined with denaturing high performance liquid chromatography. Postmortem samples were donated by the Stanley Foundation Brain Collection. We could not find significant alterations of RNA editing efficiencies of these sites in patients. However, we found trends for increased RNA editing efficiencies of site D in depressive patients (P=0.08) and site A in suicide victims (P=0.07). These findings are in accordance with the previous findings, and suggest that altered RNA editing of HTR2C may have some significance in major depression and suicide.
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Affiliation(s)
- Kazuya Iwamoto
- Laboratory for Molecular Dynamics of Mental Disorders, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-City, Saitama, 351-0198, Japan
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