RESUMEN

Rett syndrome (RTT) is an autism spectrum disorder caused by loss-of-function mutations in the methyl-CPG-binding protein 2 (Mecp2) gene. Frequent apneas and irregular breathing are prevalent in RTT, and also occur in rodent models of the disorder, including Mecp2Bird and Mecp2R168X mice. Sarizotan, a serotonin 5-HT1a and dopamine D2-like receptor agonist, reduces the incidence of apneas and irregular breathing in mouse models of RTT (Abdala et al., 2014). Targeting the 5HT1a receptor alone also improves respiration in RTT mice (Levitt et al., 2013). However, the contribution of D2-like receptors in correcting these respiratory disturbances remains untested. PAOPA, a dopamine D2-like receptor positive allosteric modulator, and quinpirole, a dopamine D2-like receptor orthosteric agonist, were used in conjunction with whole-body plethysmography to evaluate whether activation of D2-like receptors is sufficient to improve breathing disturbances in female heterozygous Mecp2Bird/+ and Mecp2R168X/+ mice. PAOPA did not significantly change apnea incidence or irregularity score in RTT mice. PAOPA also had no effect on the ventilatory response to hypercapnia (7 % CO2). In contrast, quinpirole reduced apnea incidence and irregularity scores and improved the hypercapnic ventilatory response in Mecp2R168X/+ and Mecp2Bird/+ mice, while also reducing respiratory rate. These results suggest that D2-like receptors could contribute to the positive effects of sarizotan in the correction of respiratory abnormalities in Rett syndrome. However, positive allosteric modulation of D2-like receptors alone was not sufficient to evoke these effects.

Asunto(s)

Modelos Animales de Enfermedad , Agonistas de Dopamina , Proteína 2 de Unión a Metil-CpG , Quinpirol , Receptores de Dopamina D2 , Síndrome de Rett , Animales , Síndrome de Rett/tratamiento farmacológico , Síndrome de Rett/metabolismo , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D2/agonistas , Agonistas de Dopamina/farmacología , Femenino , Ratones , Quinpirol/farmacología , Proteína 2 de Unión a Metil-CpG/genética , Respiración/efectos de los fármacos , Ratones Transgénicos , Regulación Alostérica/efectos de los fármacos , Ratones Endogámicos C57BL

RESUMEN

Dopamine (DA) D2 receptors (D2Rs) have 2 isoforms, a long form (D2L) and a short form (D2S). D2L is predominantly postsynaptic in the striatal medium spiny neurons and cholinergic interneurons. D2S is principally presynaptic autoreceptors in the nigrostriatal DA neurons. Recently, we demonstrated that L-3,4-dihydroxyphenylalanine (L-DOPA) augments D2L function through the coupling between D2L and GPR143, a receptor of L-DOPA that was originally identified as the gene product of ocular albinism 1. Here we show that GPR143 modifies the functions of D2L and D2S in an opposite manner. Haloperidol-induced catalepsy was attenuated in DA neuron-specific Gpr143 gene-deficient (Dat-cre;Gpr143flox/y) mice, compared with wild-type (Wt) mice. Haloperidol increased in vivo DA release from the dorsolateral striatum, and this increase was augmented in Gpr143-/y mice compared with Wt mice. A D2R agonist quinpirole-induced increase in the phosphorylation of GSK3ß(pGSK3ß(S9)) was enhanced in Chinese hamster ovary (CHO) cells coexpressing D2L and GPR143 compared with cells expressing D2L alone, while it was suppressed in cells coexpressing D2S and GPR143 compared with D2S alone, suggesting that GPR143 differentially modifies D2R functions depending on its isoforms of D2L and D2S.

Asunto(s)

Cricetulus , Dopamina , Haloperidol , Receptores de Dopamina D2 , Animales , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D2/genética , Haloperidol/farmacología , Células CHO , Dopamina/metabolismo , Cuerpo Estriado/metabolismo , Masculino , Glicoproteínas de Membrana/metabolismo , Glicoproteínas de Membrana/genética , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/genética , Ratones , Levodopa/farmacología , Catalepsia/inducido químicamente , Catalepsia/genética , Catalepsia/metabolismo , Ratones Endogámicos C57BL , Fosforilación , Receptores Acoplados a Proteínas G/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiología , Quinpirol/farmacología , Neuronas Dopaminérgicas/metabolismo , Glucógeno Sintasa Quinasa 3 beta/metabolismo

RESUMEN

Dopamine and histamine receptors D2R and H3R are G protein-coupled receptors (GPCRs) which can establish physical receptor-receptor interactions (RRIs), leading to homo/hetero-complexes in a dynamic equilibrium. Although D2R and H3R expression has been detected within the carotid body (CB), their possible heterodimerization has never been demonstrated. The aim of this work was to verify D2R and H3R colocalization in the CB, thus suggesting a possible interplay that, in turn, may be responsible of specific D2R-H3R antagonistic functional implications. The CBs of both Sprague-Dawley rats (n = 5) and human donors (n = 5) were dissected, and immunolocalization of D2R and H3R was performed; thereafter, in situ proximity ligation assay (PLA) was developed. According to experimental evidence (immunohistochemistry and double immunofluorescence), all the samples displayed positive D2R/H3R elements; hence, PLA assay followed by confocal microscopy analysis was positive for D2R-H3R RRIs. Additionally, D2R-H3R heterodimers were mainly detected in type I cells (ßIII-tubulin-positive cells), but type II cells' involvement cannot be excluded. RRIs may play a role in functional modulation of CB cells; investigating RRIs in the CB may guide toward the comprehension of its plastic changes and fine regulatory role while also unveiling their possible clinical implications.

RESUMEN

Alloparenting refers to the practice of caring for the young by individuals other than their biological parents. The relationship between the dynamic changes in psychological functions underlying alloparenting and the development of specific neuroreceptors remains unclear. Using a classic 10-day pup sensitization procedure, together with a pup preference and pup retrieval test on the EPM (elevated plus maze), we showed that both male and female adolescent rats (24 days old) had significantly shorter latency than adult rats (65 days old) to be alloparental, and their motivation levels for pups and objects were also significantly higher. In contrast, adult rats retrieved more pups than adolescent rats even though they appeared to be more anxious on the EPM. Analysis of mRNA expression using real-time-PCR revealed a higher dopamine D2 receptor (DRD2) receptor expression in adult hippocampus, amygdala, and ventral striatum, along with higher dopamine D1 receptor (DRD1) receptor expression in ventral striatum compared to adolescent rats. Adult rats also showed significantly higher levels of 5-hydroxytryptamine receptor 2A (HTR2A) receptor expression in the medial prefrontal cortex, amygdala, ventral striatum, and hypothalamus. These results suggest that the faster onset of alloparenting in adolescent rats compared to adult rats, along with the psychological functions involved, may be mediated by varying levels of dopamine DRD1, DRD2, and HTR2A in different forebrain regions.

Asunto(s)

Prosencéfalo , ARN Mensajero , Receptor de Serotonina 5-HT2A , Receptores de Dopamina D1 , Receptores de Dopamina D2 , Animales , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D2/genética , Masculino , Ratas , Femenino , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D1/genética , ARN Mensajero/metabolismo , ARN Mensajero/genética , Receptor de Serotonina 5-HT2A/metabolismo , Receptor de Serotonina 5-HT2A/genética , Prosencéfalo/metabolismo , Empatía/fisiología , Factores de Edad , Caracteres Sexuales , Ratas Sprague-Dawley , Conducta Animal/fisiología , Amígdala del Cerebelo/metabolismo

RESUMEN

Erasing traumatic memory during memory reconsolidation is a promising retrieval-extinction strategy for post-traumatic stress disorder (PTSD). Here, we developed an acute social defeat stress (SDS) mouse model with short-term and re-exposure-evoked long-term social avoidance. SDS-associated traumatic memories were identified to be stored in basolateral amygdala (BLA) engram cells. A single intraperitoneal administration of subanesthetic-dose ketamine within, but not beyond, the re-exposure time window significantly alleviates SDS-induced social avoidance, which reduces the activity and quantity of reactivated BLA engram cells. Furthermore, activation or inhibition of dopaminergic projections from the ventral tegmental area to the BLA effectively mimics or blocks the therapeutic effect of re-exposure with ketamine and is dopamine D2 receptor dependent. Single-cell RNA sequencing reveals that re-exposure with ketamine triggered significant changes in memory-related pathways in the BLA. Together, our research advances the understanding of how ketamine mitigates PTSD symptoms and offers promising avenues for developing more effective treatments for trauma-related disorders.

RESUMEN

Traditional Chinese medicines (TCMs) are popular in clinic because of their safety and efficacy. They contain abundant natural active compounds, which are important sources of new drug discovery. However, how to efficiently identify active compounds from complex ingredients remains a challenge. In this study, a method combining UHPLC-MS/MS characterization and in silico screening was developed to discover compounds with dopamine D2 receptor (D2R) activity in Stephania epigaea (S. epigaea). By combining the compounds identified in S. epigaea by UHPLC-MS/MS with reported compounds, a virtual library of 80 compounds was constructed for in silico screening. Potentially active compounds were chosen based on screening scores and subsequently tested for in vitro activity on a transfected cell line CHO-K1-D2 model using label-free cellular phenotypic assay. Three D2R agonists and five D2R antagonists were identified. (-)-Asimilobine, N-nornuciferine and (-)-roemerine were reported for the first time as D2R agonists, with EC50 values of 0.35 ± 0.04 µM, 1.37 ± 0.10 µM and 0.82 ± 0.22 µM, respectively. Their target specificity was validated by desensitization and antagonism assay. (-)-Isocorypalmine, (-)-tetrahydropalmatine, (-)-discretine, (+)-corydaline and (-)-roemeroline showed strong antagonistic activity on D2R with IC50 values of 92 ± 9.9 nM, 1.73 ± 0.13 µM, 0.34 ± 0.02 µM, 2.09 ± 0.22 µM and 0.85 ± 0.08 µM, respectively. Their kinetic binding profiles were characterized using co-stimulation assay and they were both D2R competitive antagonists. We docked these ligands with human D2R crystal structure and analyzed the structure-activity relationship of aporphine-type D2R agonists and protoberberine-type D2R antagonists. These results would help to elucidate the mechanism of action of S. epigaea for its analgesic and sedative efficacy and benefit for D2R drug design. This study demonstrated the potential of integrating UHPLC-MS/MS with in silico and in vitro screening for accelerating the discovery of active compounds from TCMs.

Asunto(s)

Cricetulus , Receptores de Dopamina D2 , Stephania , Espectrometría de Masas en Tándem , Espectrometría de Masas en Tándem/métodos , Células CHO , Animales , Cromatografía Líquida de Alta Presión/métodos , Stephania/química , Receptores de Dopamina D2/metabolismo , Simulación por Computador , Medicamentos Herbarios Chinos/farmacología , Medicamentos Herbarios Chinos/química , Antagonistas de los Receptores de Dopamina D2/farmacología , Antagonistas de los Receptores de Dopamina D2/química , Descubrimiento de Drogas/métodos , Agonistas de Dopamina/farmacología , Agonistas de Dopamina/química , Humanos , Medicina Tradicional China/métodos , Cromatografía Líquida con Espectrometría de Masas

RESUMEN

BACKGROUND: The association of impaired dopaminergic neurotransmission with the development and maintenance of alcohol use disorder is well known. More specifically, reduced dopamine D2/3 receptors in the striatum of subjects with alcohol dependence (AD) compared to healthy controls have been found in previous studies. Furthermore, alterations of gamma-aminobutyric acid (GABA) and glutamate (Glu) levels in the anterior cingulate cortex (ACC) of AD subjects have been documented in several studies. However, the interaction between cortical Glu levels and striatal dopamine D2/3 receptors has not been investigated in AD thus far. METHODS: This study investigated dopamine D2/3 receptor availability via 18F-fallypride positron emission tomography (PET) and GABA as well as Glu levels via magnetic resonance spectroscopy (MRS) in 19 detoxified AD subjects, 18 healthy controls (low risk, LR) controls and 19 individuals at high risk (HR) for developing AD, carefully matched for sex, age and smoking status. RESULTS: We found a significant negative correlation between GABA levels in the ACC and dopamine D2/3 receptor availability in the associative striatum of LR but not in AD or HR individuals. Contrary to our expectations, we did not observe a correlation between Glu concentrations in the ACC and striatal D2/3 receptor availability. CONCLUSIONS: The results may reflect potential regulatory cortical mechanisms on mesolimbic dopamine receptors and their disruption in AD and individuals at high risk, mirroring complex neurotransmitter interactions associated with the pathogenesis of addiction. This is the first study combining 18F-fallypride PET and MRS in AD subjects and individuals at high risk.

Asunto(s)

Alcoholismo , Giro del Cíngulo , Espectroscopía de Resonancia Magnética , Tomografía de Emisión de Positrones , Receptores de Dopamina D2 , Receptores de Dopamina D3 , Ácido gamma-Aminobutírico , Humanos , Giro del Cíngulo/metabolismo , Giro del Cíngulo/diagnóstico por imagen , Masculino , Alcoholismo/metabolismo , Alcoholismo/diagnóstico por imagen , Receptores de Dopamina D2/metabolismo , Adulto , Femenino , Receptores de Dopamina D3/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Persona de Mediana Edad , Cuerpo Estriado/metabolismo , Cuerpo Estriado/diagnóstico por imagen , Estudios de Casos y Controles , Ácido Glutámico/metabolismo , Benzamidas

RESUMEN

Chronic migraine is a disabling disorder without effective therapeutic medicine. AMPA receptors have been proven to be essential to pathological pain and headaches, but the related regulatory mechanisms in chronic migraine have not yet been explored. In this study, we found that the level of surface GluA2 was reduced in chronic migraine rats. Tat-GluR23Y (a GluA2 endocytosis inhibitor) reduced calcium inward flow and weakened synaptic structures, thus alleviating migraine-like pain sensitization. In addition, the inhibition of GluA2 endocytosis reduced the calcium influx and alleviated mitochondrial calcium overload and ROS generation in primary neurons. Furthermore, our results showed that ROS can induce allodynia and GluA2 endocytosis in rats, thus promoting migraine-like pain sensitization. In our previous study, the dopamine D2 receptor was identified as a potential target in the treatment of chronic migraine, and here we found that dopamine D2 receptor activation suppressed chronic-migraine-related pain sensitization through blocking the GluA2/ROS positive feedback loop in vivo and in vitro. Additionally, ligustrazine, a core component of ligusticum chuanxiong, was shown to target the dopamine D2 receptor, thereby alleviating ROS production and abnormal nociception in CM rats. This study provides valuable insight into the treatment of chronic migraine.

RESUMEN

PURPOSE: Brain functional and physiological plasticity is essential to combat dynamic environmental challenges. The rhythmic dopamine signaling pathway, which regulates emotion, reward and learning, shows seasonal patterns with higher capacity of dopamine synthesis and lower number of dopamine transporters during dark seasons. However, seasonal variation of the dopamine receptor signaling remains to be characterized. METHODS: Based on a historical database of healthy human brain [11C]raclopride PET scans (n = 291, 224 males and 67 females), we investigated the seasonal patterns of D2/3 dopamine receptor signaling. Daylength at the time of scanning was used as a predictor for brain regional non-displaceable binding of the radiotracer, while controlling for age and sex. RESULTS: Daylength was negatively correlated with availability of D2/3 dopamine receptors in the striatum. The largest effect was found in the left caudate, and based on the primary sample, every 4.26 h (i.e., one standard deviation) increase of daylength was associated with a mean 2.8% drop (95% CI -0.042 to -0.014) of the receptor availability. CONCLUSIONS: Seasonally varying D2/3 receptor signaling may also underlie the seasonality of mood, feeding, and motivational processes. Our finding suggests that in future studies of brain dopamine signaling, especially in high-latitude regions, the effect of seasonality should be considered.

Asunto(s)

Encéfalo , Tomografía de Emisión de Positrones , Receptores de Dopamina D2 , Receptores de Dopamina D3 , Estaciones del Año , Humanos , Masculino , Receptores de Dopamina D2/metabolismo , Femenino , Receptores de Dopamina D3/metabolismo , Adulto , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagen , Persona de Mediana Edad , Racloprida/metabolismo , Anciano , Adulto Joven

RESUMEN

Losses in dopamine (DA) functioning may contribute to aging-related decline in cognition. Hippocampal DA is necessary for successful episodic memory formation. Previously, we reported that higher DA D2 receptor (D2DR) availability in hippocampus is beneficial for episodic memory only in older carriers of more advantageous genotypes of well-established plasticity-related genetic variations, the brain-derived neurotrophic factor (BDNF, rs6265) and the kidney and brain expressed protein (KIBRA, rs17070145) polymorphisms. Extending our observations to the longitudinal level, the current data show that individuals with one or no beneficial BDNF and KIBRA genotype (n = 80) decline more in episodic memory across five years, without any contribution of losses in hippocampal D2DR availability to memory decline. Although carriers of two beneficial genotypes (n = 39) did not decline overall in episodic memory, losses of hippocampal D2DR availability were predictive of episodic-memory decline among these individuals. Our findings have implications for interventions targeting DA modulation to enhance episodic memory in aging, which may not benefit all older individuals.

Asunto(s)

Factor Neurotrófico Derivado del Encéfalo , Genotipo , Hipocampo , Memoria Episódica , Receptores de Dopamina D2 , Humanos , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Hipocampo/metabolismo , Factor Neurotrófico Derivado del Encéfalo/genética , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Masculino , Femenino , Anciano , Envejecimiento/fisiología , Envejecimiento/genética , Polimorfismo de Nucleótido Simple , Persona de Mediana Edad , Trastornos de la Memoria/genética , Trastornos de la Memoria/metabolismo , Estudios Longitudinales , Polimorfismo Genético/genética , Pruebas Neuropsicológicas , Anciano de 80 o más Años , Péptidos y Proteínas de Señalización Intracelular

RESUMEN

Dopamine D2 receptors (D2Rs) play crucial roles in regulating diverse physiological functions of the central nervous system and peripheral organs. D2Rs are also expressed in mammary glands. However, which cell types express D2Rs and whether they are involved in milk production remains unclear. The present findings revealed that D2Rs are expressed in the apical regions of the lateral membranes of mammary epithelial cells (MECs) in lactating mice. We also investigated the effects of the D2R agonist bromocriptine and/or antagonist domperidone on intracellular cAMP levels, milk protein production, and apoptosis in a lactation culture model of MECs that produce major milk components like lactating MECs in vivo. We found that bromocriptine decreased intracellular cAMP levels, whereas domperidone dose-dependently neutralized this effect. Bromocriptine also inhibited casein and lactoferrin production and suppressed activities of STAT5 and glucocorticoid receptors (GRs). Domperidone neutralized the inhibition of casein production as well as STAT5 and GR inactivation induced by bromocriptine. Furthermore, D2R activation by bromocriptine induced apoptosis and inactivated ERK, a signaling molecule responsible for promoting cell proliferation and survival. Domperidone attenuated ERK inactivation and apoptosis induced by bromocriptine. These findings suggest that D2Rs play regulatory roles in milk protein production and apoptosis in MECs.

Asunto(s)

Apoptosis , Bromocriptina , Domperidona , Células Epiteliales , Lactancia , Glándulas Mamarias Animales , Proteínas de la Leche , Receptores de Dopamina D2 , Animales , Femenino , Ratones , Apoptosis/efectos de los fármacos , Bromocriptina/farmacología , Células Cultivadas , AMP Cíclico/metabolismo , Domperidona/farmacología , Células Epiteliales/metabolismo , Células Epiteliales/efectos de los fármacos , Lactancia/metabolismo , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/metabolismo , Proteínas de la Leche/metabolismo , Proteínas de la Leche/genética , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D2/genética , Factor de Transcripción STAT5/metabolismo

RESUMEN

BACKGROUND AND PURPOSE: The dopamine D2 receptor is expressed as a short (D2S) and a long (D2L) isoform with 29 additional amino acids in the third intracellular loop. The D2S isoform shows higher presynaptic expression than the D2L isoform, and decreased D2S expression has recently been linked to an increased risk for schizophrenia. Here, we present the first investigation, at receptor isoform level, of kinetic differences in the G protein activation profiles of the D2S, compared with the D2L isoform. EXPERIMENTAL APPROACH: We employed a NanoBRET-based approach to G protein dissociation to interrogate the time-resolved coupling profile of 3×HA-tagged D2L and D2S to Gαi/o/z proteins in vitro. KEY RESULTS: Using dopamine as a D2 receptor agonist, we observed a more pronounced activation of Gαo and Gαz than Gαi proteins by D2L compared with D2S. This differentiation was not observed for D2S, which activated Gαo and Gαz with lower efficacy than D2L. These signalling differences were preserved on second messenger level and were not due to differences in receptor expression. Expanding to a set of seven full and partial D2 receptor agonists showed these effects were not restricted to dopamine but rather a mutual, receptor-associated property. Contrasting this trend, we found that D2S activated G proteins faster than D2L upon full receptor activation. CONCLUSION AND IMPLICATIONS: The findings highlight that both D2L and D2S are mechanistically able to activate all non-visual Gαi/o proteins. Thereby, they add to previous reports about isoform-specificity to certain Gαi/o proteins observed in specific cell types.

RESUMEN

The D2 dopamine receptor (DRD2) gene has garnered substantial attention as one of the most extensively studied genes across various neuropsychiatric disorders. Since its initial association with severe alcoholism in 1990, particularly through the identification of the DRD2 Taq A1 allele, numerous international investigations have been conducted to elucidate its role in different conditions. As of February 22, 2024, there are 5485 articles focusing on the DRD2 gene listed in PUBMED. There have been 120 meta-analyses with mixed results. In our opinion, the primary cause of negative reports regarding the association of various DRD2 gene polymorphisms is the inadequate screening of controls, not adequately eliminating many hidden reward deficiency syndrome behaviors. Moreover, pleiotropic effects of DRD2 variants have been identified in neuropsychologic, neurophysiologic, stress response, social stress defeat, maternal deprivation, and gambling disorder, with epigenetic DNA methylation and histone post-translational negative methylation identified as discussed in this article. There are 70 articles listed in PUBMED for DNA methylation and 20 articles listed for histone methylation as of October 19, 2022. For this commentary, we did not denote DNA and/or histone methylation; instead, we provided a brief summary based on behavioral effects. Based on the fact that Blum and Noble characterized the DRD2 Taq A1 allele as a generalized reward gene and not necessarily specific alcoholism, it now behooves the field to find ways to either use effector moieties to edit the neuroepigenetic insults or possibly harness the idea of potentially removing negative mRNA-reduced expression by inducing "dopamine homeostasis."

RESUMEN

OBJECTIVE: Binge-eating disorder is an eating disorder characterized by recurrent binge-eating episodes, during which individuals consume excessive amounts of highly palatable food (HPF) in a short time. This study investigates the intricate relationship between repeated binge-eating episode and the transcriptional regulation of two key genes, adenosine A2A receptor (A2AAR) and dopamine D2 receptor (D2R), in selected brain regions of rats. METHOD: Binge-like eating behavior on HPF was induced through the combination of food restrictions and frustration stress (15 min exposure to HPF without access to it) in female rats, compared to control rats subjected to only restriction or only stress or none of these two conditions. After chronic binge-eating episodes, nucleic acids were extracted from different brain regions, and gene expression levels were assessed through real-time quantitative PCR. The methylation pattern on genes' promoters was investigated using pyrosequencing. RESULTS: The analysis revealed A2AAR upregulation in the amygdala and in the ventral tegmental area (VTA), and D2R downregulation in the nucleus accumbens in binge-eating rats. Concurrently, site-specific DNA methylation alterations at gene promoters were identified in the VTA for A2AAR and in the amygdala and caudate putamen for D2R. DISCUSSION: The alterations on A2AAR and D2R genes regulation highlight the significance of epigenetic mechanisms in the etiology of binge-eating behavior, and underscore the potential for targeted therapeutic interventions, to prevent the development of this maladaptive feeding behavior. These findings provide valuable insights for future research in the field of eating disorders. PUBLIC SIGNIFICANCE: Using an animal model with face, construct, and predictive validity, in which cycles of food restriction and frustration stress evoke binge-eating behavior, we highlight the significance of epigenetic mechanisms on adenosine A2A receptor (A2AAR) and dopamine D2 receptor (D2R) genes regulation. They could represent new potential targets for the pharmacological management of eating disorders characterized by this maladaptive feeding behavior.

Asunto(s)

Trastorno por Atracón , Bulimia , Receptor de Adenosina A2A , Receptores de Dopamina D2 , Recompensa , Animales , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D2/genética , Femenino , Ratas , Receptor de Adenosina A2A/genética , Receptor de Adenosina A2A/metabolismo , Bulimia/metabolismo , Bulimia/genética , Trastorno por Atracón/genética , Trastorno por Atracón/metabolismo , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Metilación de ADN , Área Tegmental Ventral/metabolismo , Conducta Alimentaria , Núcleo Accumbens/metabolismo , Ratas Sprague-Dawley

RESUMEN

Natural G-protein-coupled receptors (GPCRs) rarely have an additional transmembrane (TM) helix, such as an artificial TM-linker that can unite two class A GPCRs in tandem as a single-polypeptide chain (sc). Here, we report that three groups of TM-linkers exist in the intervening regions of natural GPCR fusions from vertebrates: (1) the original consensus (i.e., consensus 1) and consensus 2~4 (related to GPCR itself or its receptor-interacting proteins); (2) the consensus but GPCR-unrelated ones, 1~7; and (3) the inability to apply 1/2 that show no similarity to any other proteins. In silico analyses indicated that all natural GPCR fusions from Amphibia lack a TM-linker, and reptiles have no GPCR fusions; moreover, in either the GPCR-GPCR fusion or fusion protein of (GPCR monomer) and non-GPCR proteins from vertebrates, excluding tetrapods, i.e., so-called fishes, TM-linkers differ from previously reported mammalian and are avian sequences and are classified as Groups 2 and 3. Thus, previously reported TM-linkers were arranged: Consensus 1 is [T(I/A/P)(A/S)-(L/N)(I/W/L)(I/A/V)GL(L/G)(A/T)(S/L/G)(I/L)] first identified in invertebrate sea anemone Exaiptasia diaphana (LOC110241027) and (330-SPSFLCI-L-SLL-340) identified in a tropical bird Opisthocomus hoazin protein LOC104327099 (XP_009930279.1); GPCR-related consensus 2~4 are, respectively, (371-prlilyavfc fgtatg-386) in the desert woodrat Neotoma lepida A6R68_19462 (OBS78147.1), (363-lsipfcll yiaallgnfi llfvi-385) in Gavia stellate (red-throated loon) LOC104264164 (XP_009819412.1), and (479-ti vvvymivcvi glvgnflvmy viir-504) in a snailfish GPCR (TNN80062.1); In Mammals Neotoma lepida, Aves Erythrura gouldiae, and fishes protein (respectively, OBS83645.1, RLW13346.1 and KPP79779.1), the TM-linkers are Group 2. Here, we categorized, for the first time, natural TM-linkers as rare evolutionary events among all vertebrates.

Asunto(s)

Receptores Acoplados a Proteínas G , Animales , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/clasificación , Receptores Acoplados a Proteínas G/metabolismo , Vertebrados/genética , Vertebrados/clasificación , Simulación por Computador , Secuencia de Aminoácidos , Humanos

RESUMEN

Dystonia is thought to arise from abnormalities in the motor loop of the basal ganglia; however, there is an ongoing debate regarding cerebellar involvement. We adopted an established cerebellar dystonia mouse model by injecting ouabain to examine the contribution of the cerebellum. Initially, we examined whether the entopeduncular nucleus (EPN), substantia nigra pars reticulata (SNr), globus pallidus externus (GPe) and striatal neurons were activated in the model. Next, we examined whether administration of a dopamine D1 receptor agonist and dopamine D2 receptor antagonist or selective ablation of striatal parvalbumin (PV, encoded by Pvalb)-expressing interneurons could modulate the involuntary movements of the mice. The cerebellar dystonia mice had a higher number of cells positive for c-fos (encoded by Fos) in the EPN, SNr and GPe, as well as a higher positive ratio of c-fos in striatal PV interneurons, than those in control mice. Furthermore, systemic administration of combined D1 receptor agonist and D2 receptor antagonist and selective ablation of striatal PV interneurons relieved the involuntary movements of the mice. Abnormalities in the motor loop of the basal ganglia could be crucially involved in cerebellar dystonia, and modulating PV interneurons might provide a novel treatment strategy.

Asunto(s)

Cuerpo Estriado , Modelos Animales de Enfermedad , Distonía , Interneuronas , Parvalbúminas , Proteínas Proto-Oncogénicas c-fos , Receptores de Dopamina D2 , Animales , Interneuronas/metabolismo , Interneuronas/efectos de los fármacos , Parvalbúminas/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Distonía/patología , Distonía/metabolismo , Distonía/fisiopatología , Cuerpo Estriado/patología , Cuerpo Estriado/metabolismo , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D1/metabolismo , Cerebelo/patología , Cerebelo/metabolismo , Ouabaína/farmacología , Ratones Endogámicos C57BL , Ratones , Masculino

RESUMEN

Schizophrenia is a serious mental illness with unknown etiology, and shows increasing incidence and high lifetime prevalence rate. The main receptors related to the disease are DRD2 and 5-HTR2A. Thus, a comprehensive understanding of the interaction mode between antipsychotic drugs with relevant receptors is very important for developing more effective drugs. 5-HTR2A-SNAP-Tag/CMC and DRD2-SNAP-Tag/CMC models constructed in this work provided a new method for studying the interaction between atypical antipsychotics and the two receptors. The results of comparative experiments showed that the new models not only met the high selectivity and specificity of the screening requirements but were also more stable and long-lasting than the traditional CMC model. Binding assays showed that the effects of three atypical antipsychotics (including clozapine, olanzapine, and quetiapine) on 5-HTR2A were stronger than their effects on DRD2. Additionally, two potentially active components, magnolol and honokiol, were screened in Magnolia officinalis methanol extract using the 5-HTR2A-SNAP-Tag/CMCHPLC-MS system. Nonlinear chromatographic analysis and molecular docking were conducted to study the interactions between screened compounds and the two receptors. The binding constants (KA) of magnolol and honokiol with 5-HTR2A were 17,854 ± 1,117 M-1 and 38,858 ± 4,964 M-1, respectively, and KA values with DRD2 were 4,872 ± 1,618 M-1 and 20,692 ± 10,267 M-1, respectively. We concluded that the established models are reliable for studying receptor-ligand interactions and screening antagonists of schizophrenia.

Asunto(s)

Compuestos Alílicos , Antipsicóticos , Compuestos de Bifenilo , Lignanos , Magnolia , Fenoles , Esquizofrenia , Antipsicóticos/farmacología , Antipsicóticos/química , Magnolia/química , Ligandos , Simulación del Acoplamiento Molecular , Esquizofrenia/tratamiento farmacológico , Esquizofrenia/metabolismo

RESUMEN

Effective rational drug discovery hinges on understanding the functional states of the target protein and distinguishing it from homologues. However, for the G protein coupled receptors, both activation-related conformational changes (ACCs) and intrinsic divergence among receptors can be misled or obscured by ligand-specific conformational changes (LCCs). Here, we unraveled ACCs and intrinsic divergence from LCCs of the dopamine D3 and D2 receptors (D3R and D2R), by analyzing their experimentally determined structures and the molecular dynamics (MD) simulation results of the receptors bound with various ligands. In addition to the ACCs common to other aminergic receptors, we revealed unique ACCs for these two receptors, including the extracellular portion of TM5 (TM5e) and TM6e shifting away from TM2e and TM3e, with a subtle rotation of TM5e. In identifying intrinsic divergence, we found more outward tilting of TM6e in the D2R compared to the D3R in both the experimental structures and simulations bound with ligands in different scaffolds. However, this difference was drastically reduced in the simulations bound with nonselective agonist quinpirole, suggesting a misleading effect of LCCs. Further, in the quinpirole-bound simulations, TM1 showed a greater disparity between these receptors, indicating that LCCs may also obscure intrinsic divergence. Importantly, our MD simulations revealed divergence in the dynamics of these receptors. Specifically, the D2R exhibited heightened flexibility compared to the D3R in the extracellular loops and TMs 5e, 6e, and 7e, associated with its greater ligand binding site plasticity. Our results lay the groundwork for crafting ligands specifically targeting the D2R and D3R with more precise pharmacological profiles.

Asunto(s)

Dopamina , Receptores de Dopamina D2 , Ligandos , Quinpirol , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D3/química , Receptores de Dopamina D3/metabolismo

RESUMEN

BACKGROUND: Hyperprolactinemia is a commonly underestimated adverse effect of antipsychotic medications. There are still no consensus guidelines for the optimal monitoring and treatment strategies. OBJECTIVE: The aim of the study was to assess the monitoring and treatment practices of antipsychotic-induced hyperprolactinemia, in addition to the prevalence and risk factors associated with it. METHODS: A retrospective cohort observational study was conducted among patients attending the psychiatric clinics at an academic tertiary hospital in Riyadh, Saudi Arabia, from May 2020 until May 2021, by reviewing each patient's medical record for up to five years. RESULTS: Among the 662 patients, 35 patients (5.3%) and 242 patients (36.6%) had their serum prolactin levels monitored (at baseline and at follow-up, respectively). The prevalence of hyperprolactinemia was observed in 212 patients (32%). Only 76 patients (36%) were symptomatic. Female gender, younger age, and bipolar disorder had a significantly higher risk of developing hyperprolactinemia. 60% of the confirmed cases received treatment, of which 76 (60%) were adherent to treatment guidelines. The most common treatment strategies implemented were dose reduction (42.5%) and aripiprazole augmentation (29.1%). CONCLUSION: It is imperative to conduct a baseline check of prolactin levels before commencing any antipsychotic therapy. Similarly, routine prolactin level monitoring is recommended regardless of symptoms in patients treated with antipsychotics with a possible prolactin-raising effect. Adherence to evidence-based treatment guidelines can improve patient quality of life and therapeutic compliance.

RESUMEN

Heterotrimeric G proteins are responsible for signal transduction from G-protein-coupled receptors (GPCRs) to intracellular effectors. This process is only possible when G proteins are located on the inner side of the cell membrane due to the specific localization of GPCR receptors. The Gα subunit is directed to the cell membrane through several signals, including modification by fatty acid moieties, interaction with the Gßγ complex, and, as observed in some Gα proteins, the presence of basic amino acid residues in the N-terminal region. In this work, we focused on investigating the influence of the polybasic region on the localization and function of a representative member of the Gαi family, Gαi3. Through the use of confocal microscopy and fluorescence lifetime microscopy, we showed that, in the case of this protein, neutralizing the positive charge does not significantly affect its abundance in the cell membrane. However, it does affect its spatial arrangement concerning the dopamine D2 receptor and influences inhibitory effect of Gαi3 on intracellular cAMP production triggered by D2 receptor stimulation. Moreover, in this work, we have shown, for the first time, that nonlipidated Gαi3 binds to negatively charged lipids through electrostatic interactions, and membrane fluidity plays a significant role in this interaction.

Asunto(s)

Proteínas de Unión al GTP Heterotriméricas , Transducción de Señal , Transducción de Señal/fisiología , Receptores Acoplados a Proteínas G/metabolismo , Proteínas de Unión al GTP Heterotriméricas/metabolismo , Membrana Celular/metabolismo