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1.
Handb Exp Pharmacol ; 2023 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-37495853

RESUMO

Research into the involvement of adrenoceptor subtypes in the cause(s) of psychiatric disorders is particularly challenging. This is partly because of difficulties in developing animal models that recapitulate the human condition but also because no evidence for any causal links has emerged from studies of patients. These, and other obstacles, are outlined in this chapter. Nevertheless, many drugs that are used to treat psychiatric disorders bind to adrenoceptors to some extent. Direct or indirect modulation of the function of specific adrenoceptor subtypes mediates all or part of the therapeutic actions of drugs in various psychiatric disorders. On the other hand, interactions with central or peripheral adrenoceptors can also explain their side effects. This chapter discusses both aspects of the field, focusing on disorders that are prevalent: depression, schizophrenia, anxiety, attention-deficit hyperactivity disorder, binge-eating disorder, and substance use disorder. In so doing, we highlight some unanswered questions that need to be resolved before it will be feasible to explain how changes in the function of any adrenoceptor subtype affect mood and behavior in humans and other animals.

2.
J Biol Chem ; 295(31): 10822-10830, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32576659

RESUMO

The interplay between G protein-coupled receptors (GPCRs) is critical for controlling neuronal activity that shapes neuromodulatory outcomes. Recent evidence indicates that the orphan receptor GPR139 influences opioid modulation of key brain circuits by opposing the actions of the µ-opioid receptor (MOR). However, the function of GPR139 and its signaling mechanisms are poorly understood. In this study, we report that GPR139 activates multiple heterotrimeric G proteins, including members of the Gq/11 and Gi/o families. Using a panel of reporter assays in reconstituted HEK293T/17 cells, we found that GPR139 functions via the Gq/11 pathway and thereby distinctly regulates cellular effector systems, including stimulation of cAMP production and inhibition of G protein inward rectifying potassium (GIRK) channels. Electrophysiological recordings from medial habenular neurons revealed that GPR139 signaling via Gq/11 is necessary and sufficient for counteracting MOR-mediated inhibition of neuronal firing. These results uncover a mechanistic interplay between GPCRs involved in controlling opioidergic neuromodulation in the brain.


Assuntos
Encéfalo/metabolismo , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa de Proteínas de Ligação ao GTP/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Receptores Opioides mu/metabolismo , Sistemas do Segundo Mensageiro , Animais , Encéfalo/citologia , AMP Cíclico/genética , AMP Cíclico/metabolismo , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/genética , Células HEK293 , Humanos , Camundongos , Proteínas do Tecido Nervoso/genética , Neurônios/citologia , Receptores Acoplados a Proteínas G/genética , Receptores Opioides mu/genética
3.
J Biol Chem ; 294(45): 16884-16896, 2019 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-31575661

RESUMO

Activation of the mitogen-activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK) by the Gi/o protein-coupled κ opioid receptor (KOR), µ opioid, and D2 dopamine receptors stimulates peroxiredoxin 6 (PRDX6)-mediated production of reactive oxygen species (ROS). ROS production by KOR-inactivating antagonists norbinaltorphimine (norBNI) and JDTic blocks Gαi protein activation, but the signaling mechanisms and consequences of JNK activation by KOR agonists remain uncharacterized. Binding of arrestins to KOR causes desensitization of G protein signaling and acts as a scaffold to initiate MAPK activation. Here, we found that the KOR agonists U50,488 and dynorphin B stimulated biphasic JNK activation with an early arrestin-independent phase, requiring the small G protein RAC family small GTPase 1 (RAC1) and protein kinase C (PKC), and a later arrestin-scaffolded phase, requiring RAC1 and Ras homolog family member (RHO) kinase. JNK activation by U50,488 and dynorphin B also stimulated PRDX6-dependent ROS production but with an inverted U-shaped dose-response relationship. KOR agonist-induced ROS generation resulted from the early arrestin-independent phase of JNK activation, and this ROS response was suppressed by arrestin-dependent activation of the MAPK p38. The apparent balance between p38 MAPK and JNK/ROS signaling has important physiological implications for understanding of dynorphin activities during the stress response. To visualize these activities, we monitored KOR agonist-mediated activation of ROS in transfected live cells by two fluorescent sensors, CellROX Green and HyPerRed. These findings establish an important aspect of opioid receptor signaling and suggest that ROS induction may be part of the physiological response to KOR activation.


Assuntos
Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptores Opioides kappa/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Ativação Enzimática/efeitos dos fármacos , Células HEK293 , Humanos , Fosforilação/efeitos dos fármacos , Receptores Opioides kappa/agonistas
4.
J Biol Chem ; 294(44): 16198-16213, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31515267

RESUMO

Ligand-dependent differences in the regulation and internalization of the µ-opioid receptor (MOR) have been linked to the severity of adverse effects that limit opiate use in pain management. MOR activation by morphine or [d-Ala2,N-MePhe4, Gly-ol]enkephalin (DAMGO) causes differences in spatiotemporal signaling dependent on MOR distribution at the plasma membrane. Morphine stimulation of MOR activates a Gαi/o-Gßγ-protein kinase C (PKC) α phosphorylation pathway that limits MOR distribution and is associated with a sustained increase in cytosolic extracellular signal-regulated kinase (ERK) activity. In contrast, DAMGO causes a redistribution of the MOR at the plasma membrane (before receptor internalization) that facilitates transient activation of cytosolic and nuclear ERK. Here, we used proximity biotinylation proteomics to dissect the different protein-interaction networks that underlie the spatiotemporal signaling of morphine and DAMGO. We found that DAMGO, but not morphine, activates Ras-related C3 botulinum toxin substrate 1 (Rac1). Both Rac1 and nuclear ERK activity depended on the scaffolding proteins IQ motif-containing GTPase-activating protein-1 (IQGAP1) and Crk-like (CRKL) protein. In contrast, morphine increased the proximity of the MOR to desmosomal proteins, which form specialized and highly-ordered membrane domains. Knockdown of two desmosomal proteins, junction plakoglobin or desmocolin-1, switched the morphine spatiotemporal signaling profile to mimic that of DAMGO, resulting in a transient increase in nuclear ERK activity. The identification of the MOR-interaction networks that control differential spatiotemporal signaling reported here is an important step toward understanding how signal compartmentalization contributes to opioid-induced responses, including anti-nociception and the development of tolerance and dependence.


Assuntos
Analgésicos Opioides/metabolismo , Receptores Opioides mu/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Analgésicos Opioides/farmacologia , Animais , Membrana Celular/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Células HEK293 , Humanos , Ligantes , Sistema de Sinalização das MAP Quinases/fisiologia , Morfina/metabolismo , Morfina/farmacologia , Fosforilação , Mapeamento de Interação de Proteínas/métodos , Mapas de Interação de Proteínas , Receptores Opioides mu/genética , Transdução de Sinais/fisiologia , Proteínas rac1 de Ligação ao GTP/fisiologia , Proteínas Ativadoras de ras GTPase/metabolismo , Proteínas Ativadoras de ras GTPase/fisiologia
5.
J Biol Chem ; 292(21): 8762-8772, 2017 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-28381559

RESUMO

µ-Opioid receptor (MOR) agonists are often used to treat severe pain but can result in adverse side effects. To circumvent systemic side effects, targeting peripheral opioid receptors is an attractive alternative treatment for severe pain. Activation of the δ-opioid receptor (DOR) produces similar analgesia with reduced side effects. However, until primed by inflammation, peripheral DOR is analgesically incompetent, raising interest in the mechanism. We recently identified a novel role for G-protein-coupled receptor kinase 2 (GRK2) that renders DOR analgesically incompetent at the plasma membrane. However, the mechanism that maintains constitutive GRK2 association with DOR is unknown. Protein kinase A (PKA) phosphorylation of GRK2 at Ser-685 targets it to the plasma membrane. Protein kinase A-anchoring protein 79/150 (AKAP), residing at the plasma membrane in neurons, scaffolds PKA to target proteins to mediate downstream signal. Therefore, we sought to determine whether GRK2-mediated DOR desensitization is directed by PKA via AKAP scaffolding. Membrane fractions from cultured rat sensory neurons following AKAP siRNA transfection and from AKAP-knock-out mice had less PKA activity, GRK2 Ser-685 phosphorylation, and GRK2 plasma membrane targeting than controls. Site-directed mutagenesis revealed that GRK2 Ser-685 phosphorylation drives the association of GRK2 with plasma membrane-associated DOR. Moreover, overexpression studies with AKAP mutants indicated that impaired AKAP-mediated PKA scaffolding significantly reduces DOR-GRK2 association at the plasma membrane and consequently increases DOR activity in sensory neurons without a priming event. These findings suggest that AKAP scaffolds PKA to increase plasma membrane targeting and phosphorylation of GRK2 to maintain DOR analgesic incompetence in peripheral sensory neurons.


Assuntos
Membrana Celular/metabolismo , Receptores Opioides delta/metabolismo , Células Receptoras Sensoriais/metabolismo , Transdução de Sinais , Proteínas de Ancoragem à Quinase A/genética , Proteínas de Ancoragem à Quinase A/metabolismo , Animais , Bovinos , Membrana Celular/genética , Proteínas Quinases Dependentes de AMP Cíclico/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Quinase 2 de Receptor Acoplado a Proteína G/genética , Quinase 2 de Receptor Acoplado a Proteína G/metabolismo , Masculino , Camundongos , Fosforilação/genética , Ratos , Ratos Sprague-Dawley , Receptores Opioides delta/agonistas , Receptores Opioides delta/genética , Células Receptoras Sensoriais/patologia
6.
J Biol Chem ; 292(25): 10414-10428, 2017 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-28450396

RESUMO

Recent advances in developing opioid treatments for pain with reduced side effects have focused on the signaling cascades of the µ-opioid receptor (MOR). However, few such signaling targets have been identified for exploitation. To address this need, we explored the role of heat-shock protein 90 (Hsp90) in opioid-induced MOR signaling and pain, which has only been studied in four previous articles. First, in four cell models of MOR signaling, we found that Hsp90 inhibition for 24 h with the inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) had different effects on protein expression and opioid signaling in each line, suggesting that cell models may not be reliable for predicting pharmacology with this protein. We thus developed an in vivo model using CD-1 mice with an intracerebroventricular injection of 17-AAG for 24 h. We found that Hsp90 inhibition strongly blocked morphine-induced anti-nociception in models of post-surgical and HIV neuropathic pain but only slightly blocked anti-nociception in a naive tail-flick model, while enhancing morphine-induced precipitated withdrawal. Seeking a mechanism for these changes, we found that Hsp90 inhibition blocks ERK MAPK activation in the periaqueductal gray and caudal brain stem. We tested these signaling changes by inhibiting ERK in the above-mentioned pain models and found that ERK inhibition could account for all of the changes in anti-nociception induced by Hsp90 inhibition. Taken together, these findings suggest that Hsp90 promotes opioid-induced anti-nociception by an ERK mechanism in mouse brain and that Hsp90 could be a future target for improving the therapeutic index of opioid drugs.


Assuntos
Analgésicos Opioides/farmacologia , Benzoquinonas/farmacologia , Tronco Encefálico/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Lactamas Macrocíclicas/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Nociceptividade/efeitos dos fármacos , Animais , Tronco Encefálico/patologia , Células CHO , Cricetinae , Cricetulus , Células HEK293 , Humanos , Masculino , Camundongos , Neuralgia/tratamento farmacológico , Neuralgia/metabolismo , Neuralgia/patologia
7.
J Biol Chem ; 291(16): 8475-85, 2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-26917724

RESUMO

The µ-opioid receptor (MOR, encoded by Oprm1) agonists are the mainstay analgesics for treating moderate to severe pain. Nerve injury causes down-regulation of MORs in the dorsal root ganglion (DRG) and diminishes the opioid effect on neuropathic pain. However, the epigenetic mechanisms underlying the diminished MOR expression caused by nerve injury are not clear. G9a (encoded by Ehmt2), a histone 3 at lysine 9 methyltransferase, is a key chromatin regulator responsible for gene silencing. In this study, we determined the role of G9a in diminished MOR expression and opioid analgesic effects in animal models of neuropathic pain. We found that nerve injury in rats induced a long-lasting reduction in the expression level of MORs in the DRG but not in the spinal cord. Nerve injury consistently increased the enrichment of the G9a product histone 3 at lysine 9 dimethylation in the promoter of Oprm1 in the DRG. G9a inhibition or siRNA knockdown fully reversed MOR expression in the injured DRG and potentiated the morphine effect on pain hypersensitivity induced by nerve injury. In mice lacking Ehmt2 in DRG neurons, nerve injury failed to reduce the expression level of MORs and the morphine effect. In addition, G9a inhibition or Ehmt2 knockout in DRG neurons normalized nerve injury-induced reduction in the inhibitory effect of the opioid on synaptic glutamate release from primary afferent nerves. Our findings indicate that G9a contributes critically to transcriptional repression of MORs in primary sensory neurons in neuropathic pain. G9a inhibitors may be used to enhance the opioid analgesic effect in the treatment of chronic neuropathic pain.


Assuntos
Analgesia , Gânglios Espinais/metabolismo , Histona-Lisina N-Metiltransferase/metabolismo , Traumatismos dos Nervos Periféricos/metabolismo , Receptores Opioides mu/metabolismo , Células Receptoras Sensoriais/metabolismo , Transcrição Gênica/efeitos dos fármacos , Animais , Feminino , Gânglios Espinais/lesões , Gânglios Espinais/patologia , Histona-Lisina N-Metiltransferase/genética , Histonas/genética , Histonas/metabolismo , Masculino , Camundongos , Traumatismos dos Nervos Periféricos/tratamento farmacológico , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/patologia , Ratos , Ratos Sprague-Dawley , Receptores Opioides mu/genética
8.
J Biol Chem ; 289(41): 28697-706, 2014 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-25183007

RESUMO

The dynamic organization of G protein-coupled receptors in the plasma membrane is suspected of playing a role in their function. The regulation of the diffusion mode of the mu-opioid (MOP) receptor was previously shown to be agonist-specific. Here we investigate the regulation of MOP receptor diffusion by heterologous activation of other G protein-coupled receptors and characterize the dynamic properties of the MOP receptor within the heterodimer MOP/neuropeptide FF (NPFF2) receptor. The data show that the dynamics and signaling of the MOP receptor in SH-SY5Y cells are modified by the activation of α2-adrenergic and NPFF2 receptors, but not by the activation of receptors not described to interact with the opioid receptor. By combining, for the first time, fluorescence recovery after photobleaching at variable radius experiments with bimolecular fluorescence complementation, we show that the MOP/NPFF2 heterodimer adopts a specific diffusion behavior that corresponds to a mix of the dynamic properties of both MOP and NPFF2 receptors. Altogether, the data suggest that heterologous regulation is accompanied by a specific organization of receptors in the membrane.


Assuntos
Analgésicos Opioides/farmacologia , Transporte Proteico/efeitos dos fármacos , Receptor Cross-Talk/efeitos dos fármacos , Receptores Adrenérgicos alfa 2/metabolismo , Receptores de Neuropeptídeos/metabolismo , Receptores Opioides mu/metabolismo , Linhagem Celular Tumoral , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Clonidina/farmacologia , Difusão , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Recuperação de Fluorescência Após Fotodegradação , Corantes Fluorescentes , Regulação da Expressão Gênica , Humanos , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neuropeptídeo Y/farmacologia , Oligopeptídeos/farmacologia , Multimerização Proteica , Receptores Adrenérgicos alfa 2/genética , Receptores de Neuropeptídeos/genética , Receptores Opioides mu/genética , Transdução de Sinais
9.
J Neurochem ; 135(1): 76-87, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26119705

RESUMO

The interaction of Regulator of G protein Signaling 4 (RGS4) with the rat mu opioid receptor (MOR)/G protein complex was investigated. Solubilized MOR from rat brain membranes was immunoprecipitated in the presence of RGS4 with antibodies against the N-terminus of MOR (anti-MOR10-70 ). Activation of MOR with [D-Ala(2) , N-Me-Phe(4) , Gly(5) -ol] enkephalin (DAMGO) during immunoprecipitation caused a 150% increase in Goα and a 50% increase in RGS4 in the pellet. When 10 µM GTP was included with DAMGO, there was an additional 72% increase in RGS4 co-immunoprecipitating with MOR (p = 0.003). Guanosine 5'-O-(3-thiotriphosphate) (GTPγS) increased the amount of co-precipitating RGS4 by 93% (compared to DAMGO alone, p = 0.008), and the inclusion of GTPγS caused the ratio of MOR to RGS4 to be 1 : 1 (31 fmoles : 28 fmoles, respectively). GTPγS also increased the association of endogenous RGS4 with MOR. In His6 RGS4/Ni(2+) -NTA agarose pull down experiments, 0.3 µM GTPγS tripled the binding of Goα to His6 RGS4, whereas the addition of 100 µM GDP blocked this effect. Importantly, activation of solubilized MOR with DAMGO in the presence of 100 µM GDP and 0.3 µM GTPγS increased Goα binding to His6 RGS4/Ni(2+) -NTA agarose (p = 0.001). Regulators of G protein Signaling (RGS) shorten the time that G proteins are active. Activation of the mu opioid receptor (MOR) causes GTP to bind to and to activate Go (αoßγ). RGS4 then binds to the activated αo-GTP/MOR complex and accelerates the intrinsic GTPase of αo. After αo dissociates from MOR, RGS4 remains bound to the C-terminal region of MOR.


Assuntos
Analgésicos Opioides/farmacologia , Guanosina Trifosfato/metabolismo , Proteínas RGS/metabolismo , Receptores Opioides mu/metabolismo , Transdução de Sinais/efeitos dos fármacos , Animais , Linhagem Celular Tumoral , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Guanosina 5'-O-(3-Tiotrifosfato)/farmacologia , Humanos , Imunoprecipitação/métodos , Ratos
10.
J Biol Chem ; 288(48): 34470-83, 2013 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-24121503

RESUMO

The crystal structures of opioid receptors provide a novel platform for inquiry into opioid receptor function. The molecular determinants for activation of the κ-opioid receptor (KOR) were studied using a combination of agonist docking, functional assays, and site-directed mutagenesis. Eighteen positions in the putative agonist binding site of KOR were selected and evaluated for their effects on receptor binding and activation by ligands representing four distinct chemotypes: the peptide dynorphin A(1-17), the arylacetamide U-69593, and the non-charged ligands salvinorin A and the octahydroisoquinolinone carboxamide 1xx. Minimally biased docking of the tested ligands into the antagonist-bound KOR structure generated distinct binding modes, which were then evaluated biochemically and pharmacologically. Our analysis identified two types of mutations: those that affect receptor function primarily via ligand binding and those that primarily affect function. The shared and differential mechanisms of agonist binding and activation in KOR are further discussed. Usually, mutations affecting function more than binding were located at the periphery of the binding site and did not interact strongly with the various ligands. Analysis of the crystal structure along with the present results provide fundamental insights into the activation mechanism of the KOR and suggest that "functional" residues, along with water molecules detected in the crystal structure, may be directly involved in transduction of the agonist binding event into structural changes at the conserved rotamer switches, thus leading to receptor activation.


Assuntos
Analgésicos Opioides/química , Sítios de Ligação/genética , Receptores Opioides kappa/química , Receptores Opioides kappa/genética , Relação Estrutura-Atividade , Analgésicos Opioides/metabolismo , Cristalografia por Raios X , Dinorfinas/química , Dinorfinas/metabolismo , Células HEK293 , Humanos , Ligantes , Simulação de Acoplamento Molecular , Mutagênese Sítio-Dirigida , Mutação/genética , Conformação Proteica , Receptores Opioides kappa/agonistas , Receptores Opioides kappa/metabolismo
11.
J Biol Chem ; 288(51): 36703-16, 2013 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-24187130

RESUMO

The kappa opioid receptor (KOR) is widely expressed in the CNS and can serve as a means to modulate pain perception, stress responses, and affective reward states. Therefore, the KOR has become a prominent drug discovery target toward treating pain, depression, and drug addiction. Agonists at KOR can promote G protein coupling and ßarrestin2 recruitment as well as multiple downstream signaling pathways, including ERK1/2 MAPK activation. It has been suggested that the physiological effects of KOR activation result from different signaling cascades, with analgesia being G protein-mediated and dysphoria being mediated through ßarrestin2 recruitment. Dysphoria associated with KOR activation limits the therapeutic potential in the use of KOR agonists as analgesics; therefore, it may be beneficial to develop KOR agonists that are biased toward G protein coupling and away from ßarrestin2 recruitment. Here, we describe two classes of biased KOR agonists that potently activate G protein coupling but weakly recruit ßarrestin2. These potent and functionally selective small molecule compounds may prove to be useful tools for refining the therapeutic potential of KOR-directed signaling in vivo.


Assuntos
Receptores Opioides kappa/agonistas , Animais , Arrestinas/metabolismo , Células CHO , Cricetinae , Cricetulus , Descoberta de Drogas , Proteínas de Ligação ao GTP/metabolismo , Humanos , Ligantes , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Quinolonas/síntese química , Quinolonas/farmacologia , Receptores Opioides kappa/metabolismo , Transdução de Sinais , Triazóis/síntese química , Triazóis/farmacologia , beta-Arrestinas
12.
J Biol Chem ; 288(33): 23964-78, 2013 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-23836900

RESUMO

Using a cell-free bioluminescence resonance energy transfer strategy we compared the levels of spontaneous and ligand-induced receptor-G protein coupling in δ (DOP) and µ (MOP) opioid receptors. In this assay GDP can suppress spontaneous coupling, thus allowing its quantification. The level of constitutive activity was 4-5 times greater at the DOP than at the MOP receptor. A series of opioid analogues with a common peptidomimetic scaffold displayed remarkable inversions of efficacy in the two receptors. Agonists that enhanced coupling above the low intrinsic level of the MOP receptor were inverse agonists in reducing the greater level of constitutive coupling of the DOP receptor. Yet the intrinsic activities of such ligands are identical when scaled over the GDP base line of both receptors. This pattern is in conflict with the predictions of the ternary complex model and the "two state" extensions. According to this theory, the order of spontaneous and ligand-induced coupling cannot be reversed if a shift of the equilibrium between active and inactive forms raises constitutive activation in one receptor type. We propose that constitutive activation results from a lessened intrinsic barrier that restrains spontaneous coupling. Any ligand, regardless of its efficacy, must enhance this constraint to stabilize the ligand-bound complexed form.


Assuntos
Receptores Opioides delta/metabolismo , Receptores Opioides mu/metabolismo , Arrestinas/metabolismo , Linhagem Celular Tumoral , Simulação por Computador , Agonismo Inverso de Drogas , Proteínas de Ligação ao GTP/metabolismo , Guanosina Difosfato/metabolismo , Humanos , Ligantes , Modelos Biológicos , Quinuclidinas/química , Quinuclidinas/farmacologia , Receptores Opioides delta/agonistas , Tirosina/análogos & derivados , Tirosina/química , Tirosina/farmacologia , beta-Arrestinas
13.
J Biol Chem ; 288(31): 22387-98, 2013 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-23775075

RESUMO

There is considerable evidence to suggest that drug actions at the κ-opioid receptor (KOR) may represent a means to control pain perception and modulate reward thresholds. As a G protein-coupled receptor (GPCR), the activation of KOR promotes Gαi/o protein coupling and the recruitment of ß-arrestins. It has become increasingly evident that GPCRs can transduce signals that originate independently via G protein pathways and ß-arrestin pathways; the ligand-dependent bifurcation of such signaling is referred to as "functional selectivity" or "signaling bias." Recently, a KOR agonist, 6'-guanidinonaltrindole (6'-GNTI), was shown to display bias toward the activation of G protein-mediated signaling over ß-arrestin2 recruitment. Therefore, we investigated whether such ligand bias was preserved in striatal neurons. Although the reference KOR agonist U69,593 induces the phosphorylation of ERK1/2 and Akt, 6'-GNTI only activates the Akt pathway in striatal neurons. Using pharmacological tools and ß-arrestin2 knock-out mice, we show that KOR-mediated ERK1/2 phosphorylation in striatal neurons requires ß-arrestin2, whereas Akt activation depends upon G protein signaling. These findings reveal a point of KOR signal bifurcation that can be observed in an endogenous neuronal setting and may prove to be an important indicator when developing biased agonists at the KOR.


Assuntos
Corpo Estriado/efeitos dos fármacos , Guanidinas/farmacologia , Naltrexona/análogos & derivados , Neurônios/efeitos dos fármacos , Receptores Opioides kappa/efeitos dos fármacos , Animais , Células CHO , Corpo Estriado/citologia , Corpo Estriado/metabolismo , Cricetinae , Cricetulus , Sistema de Sinalização das MAP Quinases , Masculino , Camundongos , Naltrexona/farmacologia , Neurônios/metabolismo , Fosforilação
14.
J Biol Chem ; 288(29): 21211-21227, 2013 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-23760268

RESUMO

The µ-opioid receptor gene, OPRM1, undergoes extensive alternative pre-mRNA splicing, as illustrated by the identification of an array of splice variants generated by both 5' and 3' alternative splicing. The current study reports the identification of another set of splice variants conserved across species that are generated through exon skipping or insertion that encodes proteins containing only a single transmembrane (TM) domain. Using a Tet-Off system, we demonstrated that the truncated single TM variants can dimerize with the full-length 7-TM µ-opioid receptor (MOR-1) in the endoplasmic reticulum, leading to increased expression of MOR-1 at the protein level by a chaperone-like function that minimizes endoplasmic reticulum-associated degradation. In vivo antisense studies suggested that the single TM variants play an important role in morphine analgesia, presumably through modulation of receptor expression levels. Our studies suggest the functional roles of truncated receptors in other G protein-coupled receptor families.


Assuntos
Processamento Alternativo/genética , Membrana Celular/metabolismo , Chaperonas Moleculares/metabolismo , Receptores Opioides mu/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Brefeldina A/farmacologia , Clonagem Molecular , DNA Complementar/genética , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina , Perfilação da Expressão Gênica , Guanosina 5'-O-(3-Tiotrifosfato) , Humanos , Camundongos , Morfina/farmacologia , Oligonucleotídeos Antissenso/farmacologia , Ligação Proteica , Multimerização Proteica , Estabilidade Proteica , Estrutura Terciária de Proteína , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Receptores Opioides mu/química , Receptores Opioides mu/genética , Ubiquitinação/efeitos dos fármacos
16.
Prog Brain Res ; 242: 217-257, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30471681

RESUMO

Ibogaine is an indole alkaloid found in the root bark of the Iboga shrub native to west Africa possessing hallucinogenic properties. For centuries it has been used in religious ceremonies and to gain spiritual enlightenment. However, since the early 1960s, its apparent ability to reduce craving for psychoactive substances including alcohol, cocaine, methamphetamine, opiates, and nicotine has led to its use in detoxification treatments. In many instances, clients receive treatment in non-medical settings, with little by way of robust scientific clinical trials. This chapter provides an overview of the potential benefits that could arise from such research. This is balanced against the serious adverse effects that can occur due to undiagnosed health conditions and/or concomitant use of other drugs. A detailed update is provided of the 33 deaths known to have occurred, including 5 in the UK. Looking forward, there is a need to develop better opiate detoxification treatment against a background of increasing opioid-related fatalities. A congener of ibogaine, 18-MC, appears to be safer and is to undergo clinical trials. In the meantime, would-be consumers and treatment providers must make more careful, detailed risk-assessments before using ibogaine. Treatment outcomes, including deaths, need to be accurately recorded and published.


Assuntos
Ensaios Clínicos como Assunto , Alucinógenos/uso terapêutico , Ibogaína/uso terapêutico , Transtornos Relacionados ao Uso de Substâncias/tratamento farmacológico , Feminino , Humanos , Masculino , Reino Unido
17.
Rev Recent Clin Trials ; 12(4): 226-232, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28814260

RESUMO

BACKGROUND: The evaluation and management of infants with neonatal abstinence syndrome (NAS), the constellation of opioid withdrawal specific to newborns, have received renewed attention over the past decade during a new epidemic of opioid use, misuse, abuse, and dependence. Infants with NAS often endure long and costly hospital stays. OBJECTIVE: We aim to review recent literature on the management and outcomes of infants with, and at risk for, opioid withdrawal. METHODS: We reviewed articles indexed in PubMed over the past 5 years that examined interventions and/or outcomes related to the management of infants with NAS. Thirty-seven studies were included in our review comprising 8 categories: 1) identification of infants at risk for NAS, 2) prenatal factors, 3) evaluation of signs and symptoms, 4) non-pharmacologic care, including rooming-in and breastfeeding, 5) standardization of traditional protocols, 6) pharmacologic management, 7) alternative treatment approaches, and 8) long-term outcomes. RESULTS: Non-pharmacologic interventions, standardization of traditional protocols, and alternative treatment approaches were all associated with improved outcomes. Lengths of stay were generally lowest in the studies of non-pharmacologic interventions. Patients exposed to buprenorphine in utero tended to have better short-term outcomes than those exposed to methadone. Longer-term outcomes for infants with NAS appear to be worse than those of control groups. CONCLUSION: The current epidemic necessitates both continued research, and the application of new evidence-based practices in the assessment and treatment of newborns exposed to opioids in utero. Projects focused on non-pharmacologic interventions appear to hold the most promise.


Assuntos
Analgésicos Opioides/efeitos adversos , Aleitamento Materno , Gerenciamento Clínico , Síndrome de Abstinência Neonatal/terapia , Humanos , Recém-Nascido
18.
Artigo em Inglês | MEDLINE | ID: mdl-29034323

RESUMO

In order to explore the initiation of detoxification of addictive patients to opiates/opioids (along with some other anti-withdrawal agents), we developed a protocol to be utilized in treatment centers particularly with heavily dependent opiate/opioid subjects. Out of 17 subjects, only three received Buprenorphine/Naloxone (Bup/nx) along with KB220Z. In this pilot, we first used a dose of KB220Z of 2 oz twice daily before meals along with clonidine and benzodiazepines and other anti-nausea and sleep aids including Gabapentin. The dose of KB220Z was maintained for 6 days in five individuals. In a second scenario, we utilized a higher dose of 4 oz every 6 hours, over a 6-day period. The higher dose was employed in another 12 patients. It is noteworthy that only 3 people have relapsed utilizing these two protocols during the first two weeks of the study, allowing for the remaining 82% to be maintained on KB220Z. The patients have been maintained without any additional Bup/nx for a minimum of 120 days and in one subject, 214 days. We are in the process of testing this hypothesis in multiple treatment centers across the United Sates utilizing data from the Clinical opiate Withdrawal Scale (COWS) pre and post KB220Z. We are in the process of testing this hypothesis in multiple treatment centers across the United Sates. While this does not constitute an acceptable controlled experiment, it does provide some preliminary evidence that agrees with an earlier study. Moreover, because of the utilization of standard detoxifying agents in this detoxification protocol, we cannot make any inference to KB220Z's effects. However, out of 17 subjects, only three required Bup/nx suggesting an interesting finding. If further confirmed in larger studies, the utilization for opiate/opioid detoxification may provide a novel way to eliminate the need for addictive opioids during withdrawal and detoxification. This paradigm shift may translate to a reduction in utilizing powerful and addictive opioids like buprenorphine and methadone (especially in these patients at high genetic risk for addiction) as not only detoxifying agents, but also maintenance drugs. While extensive research is required, this pilot paves the way for future investigations that could assist in the reduction of addictive opiate/opioid use and mortalities amongst both the young and old in America.

19.
J Syst Integr Neurosci ; 2(3): 162-165, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28491463

RESUMO

Since it is known that relapse, morality, and hospitalizations have been tied to the presence of the Dopamine D2 Receptor A1 allele, as one example, and carriers of this gene variant have a proclivity to favor amino-acid therapy, it seems intuitive that the incorporation of modalities to provide a balance and or restoration of hypodopaminergia should be considered as a front-line tactic to overcome the current American opiate/opioid epidemic, saving millions from death and unwanted locked-in-addiction. If we continue down the prim road path of fighting addiction to narcotics with narcotics, we are doomed to fail. This lesson can also have global interest.

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