1Br. J. Pharmacol. 2006 Dec 149: 967-78
TitleTrace amine-associated receptors and their ligands.
AbstractClassical biogenic amines (adrenaline, noradrenaline, dopamine, serotonin and histamine) interact with specific families of G protein-coupled receptors (GPCRs). The term 'trace amines' is used when referring to p-tyramine, beta-phenylethylamine, tryptamine and octopamine, compounds that are present in mammalian tissues at very low (nanomolar) concentrations. The pharmacological effects of trace amines are usually attributed to their interference with the aminergic pathways, but in 2001 a new gene was identified, that codes for a GPCR responding to p-tyramine and beta-phenylethylamine but not to classical biogenic amines. Several closely related genes were subsequently identified and designated as the trace amine-associated receptors (TAARs). Pharmacological investigations in vitro show that many TAAR subtypes may not respond to p-tyramine, beta-phenylethylamine, tryptamine or octopamine, suggesting the existence of additional endogenous ligands. A novel endogenous thyroid hormone derivative, 3-iodothyronamine, has been found to interact with TAAR1 and possibly other TAAR subtypes. In vivo, micromolar concentrations of 3-iodothyronamine determine functional effects which are opposite to those produced on a longer time scale by thyroid hormones, including reduction in body temperature and decrease in cardiac contractility. Expression of all TAAR subtypes except TAAR1 has been reported in mouse olfactory epithelium, and several volatile amines were shown to interact with specific TAAR subtypes. In addition, there is evidence that TAAR1 is targeted by amphetamines and other psychotropic agents, while genetic linkage studies show a significant association between the TAAR gene family locus and susceptibility to schizophrenia or bipolar affective disorder.
SCZ Keywordsschizophrenia
2J. Neurosci. Res. 2008 Nov 86: 3435-46
TitleCloning, expression, and functional analysis of rhesus monkey trace amine-associated receptor 6: evidence for lack of monoaminergic association.
AbstractSeveral recent studies report an association between trace amine-associated receptor 6 (TAAR6) and susceptibility to schizophrenia and bipolar affective disorder in humans. However, endogenous TAAR6 agonists and the receptor signaling profile and brain distribution remain unclear. Here, we clone TAAR6 from the rhesus monkey and use transfected cells to investigate whether this receptor interacts with brain monoamines and a psychostimulant drug to trigger cAMP signaling or extracellular signal-regulated kinase (ERK) phosphorylation, while investigating its expression profile in the rhesus monkey brain. Unlike TAAR1, rhesus monkey TAAR6 did not alter cAMP levels in response to 10 microM of monoamines (dopamine, norepinephrine, serotonin, beta-phenylethylamine (beta-PEA), octopamine, tryptamine, and tyramine) or methamphetamine in stably transfected cells in vitro. Real-time cell electronic sensing analysis indicated that the receptor did not alter cell impedance or change the effect of forskolin on cell impedance at exposure to 20 microM of each monoamine, suggesting a lack of either Gs or Gi-linked signaling. Whereas kappa opioid receptor activation led to ERK phosphorylation at exposure to 1 microM U69593, rhesus monkey TAAR6 had no such effect at exposure to 10 microM of monoamines or methamphetamine. Membrane and cell surface localization of TAAR6 was confirmed by immunocytochemistry, biotinylation, and Western blot testing with a TAAR6 antibody in the transfected cells. Real-time reverse transcriptase-polymerase chain reaction amplification showed that TAAR6 mRNA was undetectable in selected rhesus monkey brain regions. Together, the data reveal that TAAR6 is unresponsive to brain monoamines and is not expressed in rhesus monkey brain monoaminergic nuclei, suggesting TAAR6 lacks direct association with brain monoaminergic neuronal function.
SCZ Keywordsschizophrenia
3PLoS ONE 2010 -1 5: e13452
TitleThe dopamine metabolite 3-methoxytyramine is a neuromodulator.
AbstractDopamine (3-hydroxytyramine) is a well-known catecholamine neurotransmitter involved in multiple physiological functions including movement control. Here we report that the major extracellular metabolite of dopamine, 3-methoxytyramine (3-MT), can induce behavioral effects in a dopamine-independent manner and these effects are partially mediated by the trace amine associated receptor 1 (TAAR1). Unbiased in vivo screening of putative trace amine receptor ligands for potential effects on the movement control revealed that 3-MT infused in the brain is able to induce a complex set of abnormal involuntary movements in mice acutely depleted of dopamine. In normal mice, the central administration of 3-MT caused a temporary mild hyperactivity with a concomitant set of abnormal movements. Furthermore, 3-MT induced significant ERK and CREB phosphorylation in the mouse striatum, signaling events generally related to PKA-mediated cAMP accumulation. In mice lacking TAAR1, both behavioral and signaling effects of 3-MT were partially attenuated, consistent with the ability of 3-MT to activate TAAR1 receptors and cause cAMP accumulation as well as ERK and CREB phosphorylation in cellular assays. Thus, 3-MT is not just an inactive metabolite of DA, but a novel neuromodulator that in certain situations may be involved in movement control. Further characterization of the physiological functions mediated by 3-MT may advance understanding of the pathophysiology and pharmacology of brain disorders involving abnormal dopaminergic transmission, such as Parkinson's disease, dyskinesia and schizophrenia.
SCZ Keywordsschizophrenia
4PLoS ONE 2011 -1 6: e27073
TitleDifferential modulation of Beta-adrenergic receptor signaling by trace amine-associated receptor 1 agonists.
AbstractTrace amine-associated receptors (TAAR) are rhodopsin-like G-protein-coupled receptors (GPCR). TAAR are involved in modulation of neuronal, cardiac and vascular functions and they are potentially linked with neurological disorders like schizophrenia and Parkinson's disease. Subtype TAAR1, the best characterized TAAR so far, is promiscuous for a wide set of ligands and is activated by trace amines tyramine (TYR), phenylethylamine (PEA), octopamine (OA), but also by thyronamines, dopamine, and psycho-active drugs. Unfortunately, effects of trace amines on signaling of the two homologous ?-adrenergic receptors 1 (ADRB1) and 2 (ADRB2) have not been clarified yet in detail. We, therefore, tested TAAR1 agonists TYR, PEA and OA regarding their effects on ADRB1/2 signaling by co-stimulation studies. Surprisingly, trace amines TYR and PEA are partial allosteric antagonists at ADRB1/2, whereas OA is a partial orthosteric ADRB2-antagonist and ADRB1-agonist. To specify molecular reasons for TAAR1 ligand promiscuity and for observed differences in signaling effects on particular aminergic receptors we compared TAAR, tyramine (TAR) octopamine (OAR), ADRB1/2 and dopamine receptors at the structural level. We found especially for TAAR1 that the remarkable ligand promiscuity is likely based on high amino acid similarity in the ligand-binding region compared with further aminergic receptors. On the other hand few TAAR specific properties in the ligand-binding site might determine differences in ligand-induced effects compared to ADRB1/2. Taken together, this study points to molecular details of TAAR1-ligand promiscuity and identified specific trace amines as allosteric or orthosteric ligands of particular ?-adrenergic receptor subtypes.
SCZ Keywordsschizophrenia
5Brain Res. 2011 Jun 1393: 91-9
TitleBehavioral effects of clozapine: involvement of trace amine pathways in C. elegans and M. musculus.
AbstractClozapine is an antipsychotic medication with superior efficacy in treatment refractory schizophrenia. The molecular basis of clozapine's therapeutic profile is not well understood. We studied behavioral effects of clozapine in Caenorhabditis elegans to identify novel pathways that modulate clozapine's biological effects. Clozapine stimulated egg laying in C. elegans in a dose-dependent manner. This effect was clozapine-specific, as it was not observed with exposure to a typical antipsychotic, haloperidol or an atypical antipsychotic, olanzapine. A candidate gene screen of biogenic amine neurotransmitter systems identified signaling pathways that mediate this clozapine-specific effect on egg laying. Specifically, we found that clozapine-induced increase in egg laying requires tyramine biosynthesis. To test the implications of this finding across species, we explored whether trace amine systems modulate clozapine's behavioral effects in mammals by studying trace amine-associated receptor 1 (TAAR1) knockout mice. Clozapine increased prepulse inhibition (PPI) in wild-type mice. This increase in PPI was abrogated in TAAR1 knockout mice, implicating TAAR1 in clozapine-induced PPI enhancement. In transfected mammalian cell lines, we found no TAAR activation by antipsychotics, suggesting that modulation of trace amine signaling in mice does not occur directly at the receptor itself. In summary, we report a heretofore-unknown role for trace amine systems in clozapine-mediated effects across two species: C. elegans and mice.
SCZ Keywordsschizophrenia
6Bioorg. Med. Chem. Lett. 2012 Aug 22: 5244-8
TitleOptimisation of imidazole compounds as selective TAAR1 agonists: discovery of RO5073012.
AbstractA series of imidazole compounds has been identified which affords potent and selective partial and full agonists of the TAAR1 receptor. Starting from 2-benzyl-imidazoline screening hits, a series of structurally related 2-benzyl- and 4-benzyl-imidazoles was investigated first, but it proved highly challenging to obtain compounds having sufficient selectivity against the adrenergic alpha 2 receptor. This issue could be successfully addressed by modification of the linker region and SAR exploration led to the discovery of highly selective isopropyl-substituted 4-aminomethyl-imidazole compounds. The work culminated in the identification of the selective TAAR1 partial agonist RO5073012 (4-chlorophenyl)-(1H-imidazol-4-ylmethyl)-isopropyl-amine, 24), which has a good pharmacokinetic profile after oral administration in rodents. RO5073012 has been found to be active in a behavioural rat model which is considered indicative for schizophrenia.
SCZ Keywordsschizophrenia
7Neuropsychopharmacology 2012 Nov 37: 2580-92
TitleBrain-specific overexpression of trace amine-associated receptor 1 alters monoaminergic neurotransmission and decreases sensitivity to amphetamine.
AbstractTrace amines (TAs) such as ?-phenylethylamine, p-tyramine, or tryptamine are biogenic amines found in the brain at low concentrations that have been implicated in various neuropsychiatric disorders like schizophrenia, depression, or attention deficit hyperactivity disorder. TAs are ligands for the recently identified trace amine-associated receptor 1 (TAAR1), an important modulator of monoamine neurotransmission. Here, we sought to investigate the consequences of TAAR1 hypersignaling by generating a transgenic mouse line overexpressing TAAR1 specifically in neurons. TAAR1 transgenic mice did not show overt behavioral abnormalities under baseline conditions, despite augmented extracellular levels of dopamine and noradrenaline in the accumbens nucleus (Acb) and of serotonin in the medial prefrontal cortex. In vitro, this was correlated with an elevated spontaneous firing rate of monoaminergic neurons in the ventral tegmental area, dorsal raphe nucleus, and locus coeruleus as the result of ectopic TAAR1 expression. Furthermore, TAAR1 transgenic mice were hyposensitive to the psychostimulant effects of amphetamine, as it produced only a weak locomotor activation and failed to alter catecholamine release in the Acb. Attenuating TAAR1 activity with the selective partial agonist RO5073012 restored the stimulating effects of amphetamine on locomotion. Overall, these data show that TAAR1 brain overexpression causes hyposensitivity to amphetamine and alterations of monoaminergic neurotransmission. These observations confirm the modulatory role of TAAR1 on monoamine activity and suggest that in vivo the receptor is either constitutively active and/or tonically activated by ambient levels of endogenous agonist(s).
SCZ Keywordsschizophrenia
8Chem Biol Drug Des 2013 Apr 81: 509-16
TitleInsights into the structure and pharmacology of the human trace amine-associated receptor 1 (hTAAR1): homology modelling and docking studies.
AbstractTrace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor that belongs to the family of TAAR receptors and responds to a class of compounds called trace amines, such as ?-phenylethylamine (?-PEA) and 3-iodothyronamine (T(1)AM). The receptor is known to have a very rich pharmacology and could be also activated by other classes of compounds, including adrenergic and serotonergic ligands. It is expected that targeting TAAR1 could provide a novel pharmacological approach to correct monoaminergic dysfunctions found in several brain disorders, such as schizophrenia, depression, attention deficit hyperactivity disorder and Parkinson's disease. Only recently, the first selective TAAR1 agonist RO5166017 has been identified. To explore the molecular mechanisms of protein-agonist interaction and speed up the identification of new chemical entities acting on this biomolecular target, we derived a homology model for the hTAAR1. The putative protein-binding site has been explored by comparing the hTAAR1 model with the ?(2)-adrenoreceptor binding site, available by X-ray crystallization studies, and with the homology modelled 5HT(1A) receptor. The obtained results, in tandem with docking studies performed with RO5166017, ?-PEA and T(1)AM, provided an opportunity to reasonably identify the hTAAR1 key residues involved in ligand recognition and thus define important starting points to design new agonists.
SCZ Keywordsschizophrenia
9Mol. Psychiatry 2013 May 18: 543-56
TitleA new perspective for schizophrenia: TAAR1 agonists reveal antipsychotic- and antidepressant-like activity, improve cognition and control body weight.
Abstractschizophrenia is a chronic, severe and highly complex mental illness. Current treatments manage the positive symptoms, yet have minimal effects on the negative and cognitive symptoms, two prominent features of the disease with critical impact on the long-term morbidity. In addition, antipsychotic treatments trigger serious side effects that precipitate treatment discontinuation. Here, we show that activation of the trace amine-associated receptor 1 (TAAR1), a modulator of monoaminergic neurotransmission, represents a novel therapeutic option. In rodents, activation of TAAR1 by two novel and pharmacologically distinct compounds, the full agonist RO5256390 and the partial agonist RO5263397, blocks psychostimulant-induced hyperactivity and produces a brain activation pattern reminiscent of the antipsychotic drug olanzapine, suggesting antipsychotic-like properties. TAAR1 agonists do not induce catalepsy or weight gain; RO5263397 even reduced haloperidol-induced catalepsy and prevented olanzapine from increasing body weight and fat accumulation. Finally, TAAR1 activation promotes vigilance in rats and shows pro-cognitive and antidepressant-like properties in rodent and primate models. These data suggest that TAAR1 agonists may provide a novel and differentiated treatment of schizophrenia as compared with current medication standards: TAAR1 agonists may improve not only the positive symptoms but also the negative symptoms and cognitive deficits, without causing adverse effects such as motor impairments or weight gain.
SCZ Keywordsschizophrenia
10Nihon Shinkei Seishin Yakurigaku Zasshi 2013 Aug 33: 141-7
Title[Localization and functions of the D-neuron: significance in pathogenesis of schizophrenia].
AbstractThe author proposes the "D-cell hypothesis" for molecular basis of the mesolimbic dopamine (DA) hyperactivity of schizophrenia. D-neurons, which were defined as "non-monoaminergic aromatic L-amino acid decarboxylase (AADC)-containing cells", produce trace amines (TAs), such as tyramine, phenylethylamine (PEA) and tryptamine. D-neurons may also take up amine precursors, and may convert them to amines by decarboxylation. The author's preliminary report showed that the number of AADC-containing neurons, that is D-neurons, was reduced in the striatum and nucleus accumbens of patients with schizophrenia. TA-associated receptor type 1 (TAAR1) has been shown to have a number of ligands, such as tyramine, PEA, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), and lysergic acid diethylamide (LSD), that may change human mental states. In patients with schizophrenia, the reduction of striatal D-neurons and possible decrease of striatal TA, is caused by neural stem cell dysfunction in the subventricular zone of the lateral ventricle. The reduced stimulation of TAAR1 on terminals of ventral tegmental area (VTA) DA neurons increases the firing frequency of VTA DA neurons, as recently published reports have shown, resulting in mesolimbic DA hyperactivity. In addition, increased DA D2 receptor stimulation, caused by striatal DA hyperactivity, may suppress forebrain neural stem cell proliferation, and would cause an additional decrease of D-neurons.
SCZ Keywordsschizophrenia
11Chem Biol Drug Des 2014 Dec 84: 712-20
TitleFurther insights into the pharmacology of the human trace amine-associated receptors: discovery of novel ligands for TAAR1 by a virtual screening approach.
AbstractTrace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor that is expressed in brain and periphery and responds to a class of compounds called trace amines, such as ?-phenylethylamine (?-PEA), tyramine, tryptamine, octopamine. The receptor is known to have a very rich pharmacology and could be also activated by different classes of compounds, including dopaminergic, adrenergic and serotonergic ligands. It is expected that targeting hTAAR1 could provide a novel pharmacological approach for several human disorders, such as schizophrenia, depression, attention deficit hyperactivity disorder, Parkinson's disease and metabolic diseases. Only recently, a small number of selective hTAAR1 agonists (among which RO5166017 and T1 AM) and antagonist (EPPTB), have been reported in literature. With the aim to identify new molecular entities able to act as ligands for this target, we used an homology model for the hTAAR1 and performed a virtual screening procedure on an in-house database of compounds. A number of interesting molecules were selected and by testing them in an in vitro assay we found several agonists and one antagonist, with activities in the low micromolar range. These compounds could represent the starting point for the development of more potent and selective TAAR1 ligands.
SCZ Keywordsschizophrenia
12Neuropharmacology 2014 Jun 81: 283-91
TitleTaar1-mediated modulation of presynaptic dopaminergic neurotransmission: role of D2 dopamine autoreceptors.
AbstractTrace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor (GPCR) expressed in several mammalian brain areas and activated by "trace amines" (TAs). TAs role is unknown; however, discovery of their receptors provided an opportunity to investigate their functions. In vivo evidence has indicated an inhibitory influence of TAAR1 on dopamine (DA) neurotransmission, presumably via modulation of dopamine transporter (DAT) or interaction with the D2 DA receptor and/or activation of inwardly rectifying K(+) channels. To elucidate the mechanisms of TAAR1-dependent modulation, we used TAAR1 knockout mice (TAAR1-KO), a TAAR1 agonist (RO5166017) and a TAAR1 antagonist (EPPTB) in a set of neurochemical experiments. Analysis of the tissue content of TAAR1-KO revealed increased level of the DA metabolite homovanillic acid (HVA), and in vivo microdialysis showed increased extracellular DA in the nucleus accumbens (NAcc) of TAAR1-KO. In fast scan cyclic voltammetry (FSCV) experiments, the evoked DA release was higher in the TAAR1-KO NAcc. Furthermore, the agonist RO5166017 induced a decrease in the DA release in wild-type that could be prevented by the application of the TAAR1 antagonist EPPTB. No alterations in DA clearance, which are mediated by the DAT, were observed. To evaluate the interaction between TAAR1 and D2 autoreceptors, we tested the autoreceptor-mediated dynamics. Only in wild type mice, the TAAR1 agonist was able to potentiate quinpirole-induced inhibitory effect on DA release. Furthermore, the short-term plasticity of DA release following paired pulses was decreased in TAAR1-KO, indicating less autoinhibition of D2 autoreceptors. These observations suggest a close interaction between TAAR1 and the D2 autoreceptor regulation.
SCZ Keywordsschizophrenia
13Eur. J. Pharmacol. 2015 Sep 763: 136-42
TitleIn-vivo pharmacology of Trace-Amine Associated Receptor 1.
AbstractTrace-amines (TAs) are endogenous amines that are implicated in several physiological processes including modulation of aminergic neurotransmission. These compounds exert their effect by activating a class of G protein-coupled receptors termed Trace-Amine Associated Receptors (TAARs), where TAAR1 is the only human receptor that has been shown to bind endogenous TAs. Most of the studies have focused on studying the role of TAAR1 on modulation of the dopamine transmission. These studies indicate that TAAR1 is a negative regulator of dopamine transmission making TAAR1 a novel target for neuropsychiatric disorders that arises from dopamine dysfunction such as schizophrenia. This review discusses the unique pharmacology of TAAR1 with the major focus on the physiological role of TAAR1 and its modulation of dopamine transmission.
SCZ Keywordsschizophrenia
14Eur Neuropsychopharmacol 2015 Nov 25: 2049-61
TitleTrace amine-associated receptor 1 activation silences GSK3? signaling of TAAR1 and D2R heteromers.
AbstractTrace amine-associated receptor 1 (TAAR1) activation by selective endogenous agonists modulates dopaminergic neurotransmission. This results in antipsychotic-like behavior in vivo which might be initiated by an interaction of TAAR1 and dopamine D2L receptor (D2R). Here we analyzed the functional link between TAAR1 and D2R using highly potent and selective TAAR1 agonists, and newly generated tools such as TAAR1 knock-out and TAAR1 overexpressing rats as well as specific anti-rat TAAR1 antibodies. We provide data from co-immunoprecipitation experiments supporting a functional interaction of the two receptors in heterologous cells and in brain tissue. Interaction of TAAR1 with D2R altered the subcellular localization of TAAR1 and increased D2R agonist binding affinity. Using specific ?-arrestin 2 (?Arr2) complementation assays we show that the interaction of TAAR1 with D2R reduced ?Arr2 recruitment to D2R. In addition, we report that besides G?s-protein signaling TAAR1 also signals via ?Arr2. In the presence of D2R, cAMP signaling of TAAR1 was reduced while its ?Arr2 signaling was enhanced, resulting in reduced GSK3? activation. These results demonstrate that ?Arr2 signaling may be an important pathway for TAAR1 function and that the activation of the TAAR1-D2R complex negatively modulates GSK3? signaling. Given that patients with schizophrenia or bipolar disorder show increased GSK3? signaling, such a reduction of GSK3? signaling triggered by the interaction of D2R with activated TAAR1 further supports TAAR1 as a target for the treatment of psychiatric disorders.
SCZ Keywordsschizophrenia
15ACS Med Chem Lett 2016 Feb 7: 192-7
TitleDiscovery and Characterization of 2-Aminooxazolines as Highly Potent, Selective, and Orally Active TAAR1 Agonists.
Abstract2-Aminooxazolines were discovered as a novel structural class of TAAR1 ligands. Starting from a known adrenergic compound 1, structural modifications were made to obtain highly potent and selective TAAR1 ligands such as 12 (RO5166017), 18 (RO5256390), 36 (RO5203648), and 48 (RO5263397). These compounds exhibit drug-like physicochemical properties, have good oral bioavailability, and display in vivo activity in a variety of animal models relevant for psychiatric diseases and addiction.
SCZ Keywordsschizophrenia
16Front Neurosci 2016 -1 10: 148
TitleTrace Amines and the Trace Amine-Associated Receptor 1: Pharmacology, Neurochemistry, and Clinical Implications.
AbstractBiogenic amines are a collection of endogenous molecules that play pivotal roles as neurotransmitters and hormones. In addition to the "classical" biogenic amines resulting from decarboxylation of aromatic acids, including dopamine (DA), norepinephrine, epinephrine, serotonin (5-HT), and histamine, other biogenic amines, present at much lower concentrations in the central nervous system (CNS), and hence referred to as "trace" amines (TAs), are now recognized to play significant neurophysiological and behavioral functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both TAs, such as ?-phenylethylamine, octopamine, and tyramine, and structurally-related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways, laying the foundations for deciphering the functional significance of TAs and its mammalian CNS receptor, TAAR1. Although, its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signaling and interferes with the ?-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson's disease, schizophrenia, mood disorders, and addiction. Indeed, the recent development of novel pharmacological tools targeting TAAR1 has uncovered the remarkable potential of TAAR1-based medications as new generation pharmacotherapies in neuropsychiatry. This review summarizes recent developments in the study of TAs and TAAR1, their intricate neurochemistry and pharmacology, and their relevance for neurodegenerative and neuropsychiatric disease.
SCZ Keywordsschizophrenia
17PLoS ONE 2016 -1 11: e0152581
TitleGenetic Polymorphisms Affect Mouse and Human Trace Amine-Associated Receptor 1 Function.
AbstractMethamphetamine (MA) and neurotransmitter precursors and metabolites such as tyramine, octopamine, and ?-phenethylamine stimulate the G protein-coupled trace amine-associated receptor 1 (TAAR1). TAAR1 has been implicated in human conditions including obesity, schizophrenia, depression, fibromyalgia, migraine, and addiction. Additionally TAAR1 is expressed on lymphocytes and astrocytes involved in inflammation and response to infection. In brain, TAAR1 stimulation reduces synaptic dopamine availability and alters glutamatergic function. TAAR1 is also expressed at low levels in heart, and may regulate cardiovascular tone. TAAR1 knockout mice orally self-administer more MA than wild type and are insensitive to its aversive effects. DBA/2J (D2) mice express a non-synonymous single nucleotide polymorphism (SNP) in TAAR1 that does not respond to MA, and D2 mice are predisposed to high MA intake, compared to C57BL/6 (B6) mice. Here we demonstrate that endogenous agonists stimulate the recombinant B6 mouse TAAR1, but do not activate the D2 mouse receptor. Progeny of the B6XD2 (BxD) family of recombinant inbred (RI) strains have been used to characterize the genetic etiology of diseases, but contrary to expectations, BXDs derived 30-40 years ago express only the functional B6 TAAR1 allele whereas some more recently derived BXD RI strains express the D2 allele. Data indicate that the D2 mutation arose subsequent to derivation of the original RIs. Finally, we demonstrate that SNPs in human TAAR1 alter its function, resulting in expressed, but functional, sub-functional and non-functional receptors. Our findings are important for identifying a predisposition to human diseases, as well as for developing personalized treatment options.
SCZ Keywordsschizophrenia
18Drug Alcohol Depend 2016 Feb 159: 9-16
Title"TAARgeting Addiction"--The Alamo Bears Witness to Another Revolution: An Overview of the Plenary Symposium of the 2015 Behavior, Biology and Chemistry Conference.
AbstractIn keeping with the free-thinking tradition San Antonians are known for, the Scientific Program Committee of the Behavior, Biology and Chemistry: Translational Research in Addiction Conference chose trace amine-associated receptor 1 (TAAR1) as the focus of the plenary symposium for its 7th annual meeting held at the University of Texas Health Science Center at San Antonio on March 14 and 15, 2015. The timing of the meeting's plenary session on TAAR1 coincided with the Ides of March, an apt concurrence given the long association of this date with the overthrow of the status quo. And whether aware of the coincidence or not, those in attendance witnessed the plunging of the metaphorical dagger into the heart of the dopamine (DA) transporter (DAT)-centric view of psychostimulant action.
The symposium's four plenary presentations focused on the molecular and cellular biology, genetics, medicinal chemistry and behavioral pharmacology of the TAAR1 system and the experimental use of newly developed selective TAAR1 ligands.
The consensus was that TAAR1 is a DA and methamphetamine receptor, interacts with DAT and DA D2 receptors, and is essential in modulating addiction-related effects of psychostimulants.
Collectively the findings presented during the symposium constitute a significant challenge to the current view that psychostimulants such as methamphetamine and amphetamine solely target DAT to interfere with normal DA signaling and provide a novel conceptual framework from which a more complete understanding of the molecular mechanisms underlying the actions of DA and METH is likely to emerge.
SCZ Keywordsschizophrenia