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1.
《Life sciences》1996,59(8):659-668
Cannabinoid receptors belong to the class of G-protein-coupled receptors which inhibit adenylyl cyclase. Coupling of receptors to G-proteins can be assessed by the ability of agonists to stimulate guanosine-5′-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding in the presence of excess GDP. The present study examined the effect of cannabinoid agonists on [35S]GTPγS binding in rat brain membranes. Assays were conducted with 0.05 nM [35S]GTPγS, incubated with rat cerebellar membranes, 1–30 μM GDP and the cannabinoid agonist WIN 55212-2. Results showed that the ability of WIN 55212-2 to stimulate [35S]GTPγS binding increased with increasing concentrations of GDP, with 10–30 μM GDP providing approximately 150–200% stimulation by the cannabinoid agonist. The pharmacology of cannabinoid agonist stimulation of [35S]GTPγS binding paralleled that of previously reported receptor binding and adenylyl cyclase assays, and agonist stimulation of [35S]GTPγS binding was blocked by the cannabinoid antagonist SR141716A. Brain regional studies revealed widespread stimulation of [35S]GTPγS binding by WIN 55212-2 in a number of brain areas, consistent with in vitro [35S]GTPγS autoradiography. These results demonstrate that [35S]GTPγS binding in the presence of excess GDP is an effective measure of cannabinoid receptor coupling to G-proteins in brain membranes. 相似文献
2.
Lawrence C. Blume Caroline E. Bass Steven R. Childers George D. Dalton David C. S. Roberts Jasmine M. Richardson Ruoyu Xiao Dana E. Selley Allyn C. Howlett 《Journal of neurochemistry》2013,124(6):808-820
Although biochemical and physiological evidence suggests a strong interaction between striatal CB1 cannabinoid (CB1R) and D2 dopamine (D2R) receptors, the mechanisms are poorly understood. We targeted medium spiny neurons of the indirect pathway using shRNA to knockdown either CB1R or D2R. Chronic reduction in either receptor resulted in deficits in gene and protein expression for the alternative receptor and concomitantly increased expression of the cannabinoid receptor interacting protein 1a (CRIP1a), suggesting a novel role for CRIP1a in dopaminergic systems. Both CB1R and D2R knockdown reduced striatal dopaminergic‐stimulated [35S]GTPγS binding, and D2R knockdown reduced pallidal WIN55212‐2‐stimulated [35S]GTPγS binding. Decreased D2R and CB1R activity was associated with decreased striatal phosphoERK. A decrease in mRNA for opioid peptide precursors pDYN and pENK accompanied knockdown of CB1Rs or D2Rs, and over‐expression of CRIP1a. Down‐regulation in opioid peptide mRNAs was followed in time by increased DOR1 but not MOR1 expression, leading to increased [D‐Pen2, D‐Pen5]‐enkephalin‐stimulated [35S]GTPγS binding in the striatum. We conclude that mechanisms intrinsic to striatal medium spiny neurons or extrinsic via the indirect pathway adjust for changes in CB1R or D2R levels by modifying the expression and signaling capabilities of the alternative receptor as well as CRIP1a and the DELTA opioid system. 相似文献
3.
《Journal of receptor and signal transduction research》2013,33(1):98-106
AbstractContext: Previous studies have indicated a role for beta-arrestin2 in the regulation of brain cannabinoid effects and cannabinoid CB1 receptors, but whether beta-arrestin1 has a role has not been investigated. Objective: To determine the role of beta-arrestin1 in cannabinoid activity. Materials and methods: Beta-arrestin1 ?/? mice and their wild-type (+/+) counterparts were assayed for antinociceptive and temperature-decreasing effects of two ligands, Δ9-tetrahydrocannabinol (THC) and CP55940, after both single and repeated administration. In vitro assays examined the effects of deletion on CB1 receptor density, agonist-binding and G-protein activation. Results: Deletion of beta-arrestin1 diminished the effects of CP55940 in both antinociception (latency to tail withdrawal) and temperature-depression assays in mice. However, deleting beta-arrestin1 had no effect on the actions of THC in either assay. Antagonist radioligand ([3H]SR141716A) saturation binding indicated no difference between beta-arrestin1 +/+ and ?/? mice in the density or affinity for cannabinoid CB1 receptors in brain membranes. CP55940 agonist binding in brain membranes from beta-arrestin1 +/+ mice exhibited high- and intermediate-affinity sites, but beta-arrestin1 ?/? membranes exhibited an additional site with low affinity. CP55940 produced greater stimulation of [35S]GTPγS binding to membranes from whole brain of beta-arrestin1 ?/? than +/+ mice. The rates of the development of tolerance to chronic THC or CP55940 administration did not appear to be affected by genotype. Discussion: Beta-arrestin1 appeared to mediate the actions of CP55940, but did not affect the activity of THC. Conclusion: Beta-arrestin1 regulates cannabinoid CB1 receptor sensitivity in an agonist-selective manner, but may not be the primary mediator of tolerance to cannabinoid agonists. 相似文献
4.
《Peptides》2014
Previous studies suggest that cannabinoids system plays an important role in cardiovascular regulation. (m)VD-hemopressin(α) (VD-Hpα), an 11-residue peptide originating from the α1 chain of hemoglobin, was recently reported as a selective agonist of cannabinoid CB1 receptor. The present study was undertaken to investigate the intrathecal (i.t.) action of (m)VD-Hpα on blood pressure in urethane-anesthetized rats. Our results demonstrated that injections of (m)VD-Hpα (5–30 nmol, i.t.) produced a dose-dependent decrease in mean arterial pressure (MAP), similar to that of the non-peptidic cannabinoid receptor agonist WIN55212-2 (1.25–10 nmol, i.t.). The hypotensive effect of (m)VD-Hpα was not influenced by the CB1 receptor antagonist AM251 (20 nmol, i.t.) or the CB2 receptor antagonist AM630 (20 nmol, i.t.). However, WIN55212-2-induced hypotension was almost completely prevented by i.t. administration of AM251, not by AM630. The spinal hypotension of (m)VD-Hpα and WIN55212-2 was significantly reduced by pretreatment with the α-adrenoceptor antagonist phentolamine (1 mg/kg, i.v.), but not by the β-adrenoceptor antagonist propranolol (2 mg/kg, i.v.) or the muscarinic receptor antagonist atropine (2 mg/kg, i.v.). In addition, l-NAME (50 mg/kg, i.v.), the inhibitor of nitric oxide (NO) synthase, significantly reduced WIN55212-2-induced hypotension, but had no effect on the hypotensive response to (m)VD-Hpα. Collectively, the results show that i.t. administration of (m)VD-Hpα induces a decrease in MAP via a non-CB1 and non-CB2 mechanism. 相似文献
5.
Maider López De Jesús Cristina Hostalot Jesús M. Garibi Joan Sallés J. Javier Meana Luis F. Callado 《Neurochemistry international》2010,56(6-7):829-833
Gliomas are the most important group of malignant primary brain tumors and one of the most aggressive forms of cancer. During the last years, several studies have demonstrated that cannabinoids induce apoptosis of glioma cells and inhibit angiogenesis of gliomas in vivo. As the effects of cannabinoids rely on CB1 and CB2 receptors activation, the aim of the present study was to investigate both receptors protein expression in cellular membrane homogenates of human glial tumors using specific antibodies raised against these proteins. Additionally, we studied the functionality of the cannabinoid receptors in glioblastomas by using WIN 55,212-2 stimulated [35S]GTPγS binding.Western blot analysis showed that CB1 receptor immunoreactivity was significantly lower in glioblastoma multiforme (?43%, n = 10; p < 0.05) than in normal post-mortem brain tissue (n = 16). No significant differences were found for astrocytoma (n = 6) and meningioma (n = 8) samples. Conversely, CB2 receptor immunoreactivity was significantly greater in membranes of glioblastoma multiforme (765%, n = 9; p < 0.05) and astrocytoma (471%, n = 4; p < 0.05) than in control brain tissue (n = 10). Finally, the maximal stimulation of [35S]GTPγS binding by WIN 55,212-2 was significantly lower in glioblastomas (134 ± 4%) than in control membranes (183 ± 2%; p < 0.05). The basal [35S]GTPγS binding and the EC50 values were not significantly different between both groups.The present results demonstrate opposite changes in CB1 and CB2 receptor protein expression in human gliomas. These changes may be of interest for further research about the therapeutic effects of cannabinoids in glial tumors. 相似文献
6.
《Cell Adhesion & Migration》2013,7(2):91-99
Recent findings indicate that cannabinoid-altered vocal development involves elevated densities of dendritic spines in a subset of brain regions involved in zebra finch song learning and production suggesting that cannabinoid receptor activation may regulate cell structure. Here we report that activation of zebra finch CB1 receptors (zfCB1, delivered by a lentivector to CHO cells) produces dose-dependent biphasic effects on the mean length of filopodia expressed: Low agonist concentrations (3 nM WIN55212-2) increase lengths while higher concentrations reduce them. In contrast, treatment of zfCB1-expressing cells with the antagonist/inverse agonist SR141716A causes increases in both mean filopodia length and number at 30 and 100 nM. These results demonstrate that CB1 receptor activation can differentially influence filiopodia elongation depending on dose, and demonstrate that manipulation of cannabinoid receptor activity is capable of modulating cell morphology. 相似文献
7.
Recent findings indicate that cannabinoid-altered vocal development involves elevated densities of dendritic spines in a subset of brain regions involved in zebra finch song learning and production suggesting that cannabinoid receptor activation may regulate cell structure. Here we report that activation of zebra finch CB1 receptors (zfCB1, delivered by a lentivector to CHO cells) produces dose-dependent biphasic effects on the mean length of filopodia expressed: Low agonist concentrations (3 nM WIN55212-2) increase lengths while higher concentrations reduce them. In contrast, treatment of zfCB1-expressing cells with the antagonist/inverse agonist SR141716A causes increases in both mean filopodia length and number at 30 and 100 nM. These results demonstrate that CB1 receptor activation can differentially influence filiopodia elongation depending on dose, and demonstrate that manipulation of cannabinoid receptor activity is capable of modulating cell morphology. 相似文献
8.
《Neurochemistry international》2009,54(6-8):309-316
Formerly considered as an exclusively peripheral receptor, it is now accepted that CB2 cannabinoid receptor is also present in limited amounts and distinct locations in the brain of several animal species, including mice. However, the possible roles of CB2 receptors in the brain need to be clarified. The aim of our work was to study the μ-opioid receptor (MOR) mRNA expression level and functional activity after acute in vivo and in vitro treatments with the endocannabinoid noladin ether (NE) and with the CB2 receptor antagonist SR144528 in brainstem of mice deficient in either CB1 or CB2 receptors. This study is based on our previous observations that noladin ether (NE) produces decrease in the activity of MOR in forebrain and this attenuation can be antagonized by the CB2 cannabinoid antagonist SR144528, suggesting a CB2 receptor mediated effect. We used quantitative real-time PCR to examine the changes of MOR mRNA levels, [35S]GTPγS binding assay to analyze the capability of μ-opioid agonist DAMGO to activate G-proteins and competition binding assays to directly measure the ligand binding to MOR in mice brainstem. After acute NE administration no significant changes were observed on MOR signaling. Nevertheless pretreatment of mice with SR144528 prior to the administration of NE significantly decreased MOR signaling suggesting the involvement of SR144528 in mediating the effect of MOR. mRNA expression of MORs significantly decreased both in CB1 wild-type and CB1 knockout mice after a single injection of SR144528 at 0.1 mg/kg when compared to the vehicle treated controls. Consequently, MOR-mediated signaling was attenuated after acute in vivo treatment with SR144528 in both CB1 wild-type and CB1 knockout mice. In vitro addition of 1 μM SR144528 caused a decrease in the maximal stimulation of DAMGO in [35S]GTPγS binding assays in CB2 wild-type brainstem membranes whereas no significant changes were observed in CB2 receptor knockouts. Radioligand binding competition studies showed that the noticed effect of SR144528 on MOR signaling is not mediated through MORs. Our data demonstrate that the SR144528 caused pronounced decrease in the activity of MOR is mediated via CB2 cannabinoid receptors. 相似文献
9.
Cannabinoid CB1 receptor (CB1R) activation decreases synaptic GABAergic and glutamatergic transmission and it also controls peripheral metabolism. Here we aimed at testing with 13C NMR isotopomer analysis whether CB1Rs could have a local metabolic role in brain areas having high CB1R density, such as the hippocampus. We labelled hippocampal slices with the tracers [2-13C]acetate, which is oxidized in glial cells, and [U-13C]glucose, which is metabolized both in glia and neurons, to evaluate metabolic compartmentation between glia and neurons. The synthetic CB1R agonist WIN55212-2 (1 μM) significantly decreased the metabolism of both [2-13C]acetate (−11.6 ± 2.0%) and [U-13C]glucose (−11.2 ± 3.4%) in the tricarboxylic acid cycle that contributes to the glutamate pool. WIN55212-2 also significantly decreased the metabolism of [U-13C]glucose (−11.7 ± 4.0%) but not that of [2-13C]acetate contributing to the pool of GABA. These effects of WIN55212-2 were prevented by the CB1R antagonist AM251 (500 nM). These results thus suggest that CB1Rs might be present also in hippocampal astrocytes besides their well-known neuronal localization. Indeed, confocal microscopy analysis revealed the presence of specific CB1R immunoreactivity in astrocytes and pericytes throughout the hippocampus.In conclusion, CB1Rs are able to control hippocampal intermediary metabolism in both neuronal and glial compartments, which suggests new alternative mechanisms by which CB1Rs control cell physiology and afford neuroprotection. 相似文献
10.
Bastien Reux Tapio Nevalainen Katri H. Raitio Ari M.P. Koskinen 《Bioorganic & medicinal chemistry》2009,17(13):4441-4447
A series of quinolinyl and isoquinolinyl phenyl ketones was synthesized and their CB2 receptor-dependent G-protein activities were determined using the [35S]GTPγS binding assay. Both quinoline and isoquinoline derivatives exhibited similar CB2 receptor agonist activity, the most potent ligands being the 2-(Me2N)-phenyl substituted derivatives, which were also full agonists at the CB2-receptor. 相似文献
11.
《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1999,122(3):327-330
The influence of saturated and unsaturated fatty acid ethanolamides as well as Δ9-tetrahydrocannabinol (Δ9-THC), WIN 55,212-2 and cannabinoid CB1 receptor antagonist SR 141716 on sea urchin fertilization was studied. The ethanolamides of arachidonic, oleic and linoleic acids but not saturated fatty acid (C14–C20) derivatives inhibited fertilization when pre-incubated with sperm cells. Δ9-THC and WIN 55,212-2 also inhibited fertilization, Δ9-THC being ten times as potent as WIN 55,212-2. Selective cannabinoid CB1 receptor antagonist SR 141716 also blocked fertilization and did not antagonize the action of Δ9-THC. The obtained results indicate that different unsaturated fatty acid ethanolamides may control sea urchin fertilization, and that sea urchin sperm cell cannabinoid receptor may differ from the known cannabinoid receptor subtypes. 相似文献
12.
Kevin Wilhelmsen Samira Khakpour Alphonso Tran Kayla Sheehan Mark Schumacher Fengyun Xu Judith Hellman 《The Journal of biological chemistry》2014,289(19):13079-13100
Although cannabinoids, such as Δ9-tetrahydrocannabinol, have been studied extensively for their psychoactive effects, it has become apparent that certain cannabinoids possess immunomodulatory activity. Endothelial cells (ECs) are centrally involved in the pathogenesis of organ injury in acute inflammatory disorders, such as sepsis, because they express cytokines and chemokines, which facilitate the trafficking of leukocytes to organs, and they modulate vascular barrier function. In this study, we find that primary human ECs from multiple organs express the cannabinoid receptors CB1R, GPR18, and GPR55, as well as the ion channel transient receptor potential cation channel vanilloid type 1. In contrast to leukocytes, CB2R is only minimally expressed in some EC populations. Furthermore, we show that ECs express all of the known endocannabinoid (eCB) metabolic enzymes. Examining a panel of cannabinoids, we demonstrate that the synthetic cannabinoid WIN55,212-2 and the eCB N-arachidonoyl dopamine (NADA), but neither anandamide nor 2-arachidonoylglycerol, reduce EC inflammatory responses induced by bacterial lipopeptide, LPS, and TNFα. We find that endothelial CB1R/CB2R are necessary for the effects of NADA, but not those of WIN55,212-2. Furthermore, transient receptor potential cation channel vanilloid type 1 appears to counter the anti-inflammatory properties of WIN55,212-2 and NADA, but conversely, in the absence of these cannabinoids, its inhibition exacerbates the inflammatory response in ECs activated with LPS. These data indicate that the eCB system can modulate inflammatory activation of the endothelium and may have important implications for a variety of acute inflammatory disorders that are characterized by EC activation. 相似文献
13.
Carmel O'Neill Alex Evers-Donnelly David Nicholson Kathy M. O'Boyle John J. O'Connor 《Journal of neurochemistry》2009,108(3):545-551
Cannabinoid CB1 receptors are highly expressed in the striatum where they are known to be co‐localized with dopamine D2 receptors. There is now strong evidence that cannabinoids modulate dopamine release in the brain. Using fast cyclic voltammetry, single pulse stimulation (0.1 ms; 10 V) was applied every 5 min and peak dopamine release was measured with a carbon fibre microelectrode. Application of the D2 receptor agonist, quinpirole, inhibited single pulse dopamine overflow in a concentration‐dependent manner (IC50: 3.25 × 10?8 M). The CB1 receptor agonist WIN55212‐2 (WIN; 1 μM) had no effect on single pulse dopamine release (93.9 ± 6.6% at 60 min, n = 5) but attenuated the inhibitory effect of quinpirole (30 nM; quinpirole 39.0 ± 4.2% vs. quinpirole + WIN, 48.2 ± 3.7%, n = 5, p < 0.05). This affect was antagonized by the CB1 receptor anatgonist [N‐(Piperidin‐1‐yl)‐5‐(4‐iodophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐methyl‐1H‐pyrazole‐3‐carboxamide] (AM‐251, 1 μM). Dopamine release evoked by four pulses delivered at 1 Hz (4P1Hz) and 10 pulses delivered at 5 Hz (10P5Hz) was significantly inhibited by WIN [72.3 ± 7.9% control (peak 4 to 1 ratio measurement) and 66.9 ± 3.8% control (area under the curve measurement), respectively, p < 0.05; n = 6 for both]. Prior perfusion of WIN significantly attenuated the effects of quinpirole on multiple pulse‐evoked dopamine release (4P1Hz: quinpirole, 28.4 ± 4.8% vs. WIN + quinpirole, 52.3 ± 1.2%; 10P5Hz: quinpirole, 29.5 ± 1.3% vs. WIN + quinpirole, 59.4 ±7.1%; p < 0.05 for both; n = 6). These effects were also antagonized by AM‐251 (1 μM). This is the first report demonstrating a functional, antagonistic interaction between CB1 receptors and D2 autoreceptors in regulating rat striatal dopamine release. 相似文献
14.
Sheryl Stark Mary A. Pacheco Steven R. Childers 《Cellular and molecular neurobiology》1997,17(5):483-493
1. Aminoalkylindoles, typified by WIN 55212-2, bind to G protein-coupled cannabinoid receptors in brain. Although cannabinoids inhibit adenylyl cyclase in NG108-15 neuroblastoma × glioma hybrid cells, cannabinoid receptor binding in these cells has not been described previously. This study compares pharamcological characteristics of [3H]WIN 55212-2 binding sites in rat cerebellar membranes and in NG108-15 membranes.2. Although the K
D of specifid [3H]WIN 55212-2 binding was similar in brain and NG108-15 membranes, the B
max was 10 times lower in NG108-15 than in cerebellar membranes. In both brain and NG108-15 membranes, aminoalkylindole analogues were relatively potent in displacing [3H]WIN 55212-2 binding.However, IC50 values for more traditional cannabinoids were significantly higher in NG108-15 membranes than in brain, e.g., the K
i values for CP55,940 were1.2nM in brain and >5000nM in NG108-15 membranes. Moreover, sodium and GTP--S decreased [3H]WIN 55212-2 binding in brain but not in NG108-15membranes.3. These data suggest that WIN 55212-2 does not label traditional cannabinoid receptors in NG108-15 cells and that these novel aminoalkylindolebinding sites are not coupled to G proteins. 相似文献
15.
Maurice R. Elphick 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2012,367(1607):3201-3215
CB1- and CB2-type cannabinoid receptors mediate effects of the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide in mammals. In canonical endocannabinoid-mediated synaptic plasticity, 2-AG is generated postsynaptically by diacylglycerol lipase alpha and acts via presynaptic CB1-type cannabinoid receptors to inhibit neurotransmitter release. Electrophysiological studies on lampreys indicate that this retrograde signalling mechanism occurs throughout the vertebrates, whereas system-level studies point to conserved roles for endocannabinoid signalling in neural mechanisms of learning and control of locomotor activity and feeding. CB1/CB2-type receptors originated in a common ancestor of extant chordates, and in the sea squirt Ciona intestinalis a CB1/CB2-type receptor is targeted to axons, indicative of an ancient role for cannabinoid receptors as axonal regulators of neuronal signalling. Although CB1/CB2-type receptors are unique to chordates, enzymes involved in biosynthesis/inactivation of endocannabinoids occur throughout the animal kingdom. Accordingly, non-CB1/CB2-mediated mechanisms of endocannabinoid signalling have been postulated. For example, there is evidence that 2-AG mediates retrograde signalling at synapses in the nervous system of the leech Hirudo medicinalis by activating presynaptic transient receptor potential vanilloid-type ion channels. Thus, postsynaptic synthesis of 2-AG or anandamide may be a phylogenetically widespread phenomenon, and a variety of proteins may have evolved as presynaptic (or postsynaptic) receptors for endocannabinoids. 相似文献
16.
Kathleen M. BissetAmey S. Dhopeshwarkar Chengyong LiaoRussell A. Nicholson 《Neurochemistry international》2011,59(5):706-713
This research examines the in vitro interaction of phthalate diesters and monoesters with the G protein-coupled cannabinoid 1 (CB1) receptor, a presynaptic complex involved in the regulation of synaptic activity in mammalian brain. The diesters, n-butylbenzylphthalate (nBBP), di-n-hexylphthalate (DnHP), di-n-butylphthalate (DnBP), di-2-ethylhexylphthalate (DEHP), di-isooctylphthalate (DiOP) and di-n-octylphthalate (DnOP) inhibited the specific binding of the CB1 receptor agonist [3H]CP-55940 to mouse whole brain membranes at micromolar concentrations (IC50s: nBBP 27.4 μM; DnHP 33.9 μM; DnBP 45.9 μM; DEHP 47.4 μM; DiOP 55.4 μM; DnOP 75.2 μM). DnHP, DnBP and nBBP achieved full (or close to full) blockade of [3H]CP-55940 binding, whereas DEHP, DiOP and DnOP produced partial (55-70%) inhibition. Binding experiments with phenylmethane-sulfonylfluoride (PMSF) indicated that the ester linkages of nBBP and DnBP remain intact during assay. The monoesters mono-2-ethylhexylphthalate (M2EHP) and mono-isohexylphthalate (MiHP) failed to reach IC50 at 150 μM and mono-n-butylphthalate (MnBP) was inactive. Inhibitory potencies in the [3H]CP-55940 binding assay were positively correlated with inhibition of CB1 receptor agonist-stimulated binding of [35S]GTPγS to the G protein, demonstrating that phthalates cause functional impairment of this complex. DnBP, nBBP and DEHP also inhibited binding of [3H]SR141716A, whereas inhibition with MiHP was comparatively weak and MnBP had no effect. Equilibrium binding experiments with [3H]SR141716A showed that phthalates reduce the Bmax of radioligand without changing its Kd. DnBP and nBBP also rapidly enhanced the dissociation of [3H]SR141716A. Our data are consistent with an allosteric mechanism for inhibition, with phthalates acting as relatively low affinity antagonists of CB1 receptors and cannabinoid agonist-dependent activation of the G-protein. Further studies are warranted, since some phthalate esters may have potential to modify CB1 receptor-dependent behavioral and physiological outcomes in the whole animal. 相似文献
17.
Ankur Kapur Pingwei Zhao Haleli Sharir Yushi Bai Marc G. Caron Larry S. Barak Mary E. Abood 《The Journal of biological chemistry》2009,284(43):29817-29827
The cannabinoid receptor 1 (CB1) and CB2 cannabinoid receptors, associated with drugs of abuse, may provide a means to treat pain, mood, and addiction disorders affecting widespread segments of society. Whether the orphan G-protein coupled receptor GPR55 is also a cannabinoid receptor remains unclear as a result of conflicting pharmacological studies. GPR55 has been reported to be activated by exogenous and endogenous cannabinoid compounds but surprisingly also by the endogenous non-cannabinoid mediator lysophosphatidylinositol (LPI). We examined the effects of a representative panel of cannabinoid ligands and LPI on GPR55 using a β-arrestin-green fluorescent protein biosensor as a direct readout of agonist-mediated receptor activation. Our data demonstrate that AM251 and SR141716A (rimonabant), which are cannabinoid antagonists, and the lipid LPI, which is not a cannabinoid receptor ligand, are GPR55 agonists. They possess comparable efficacy in inducing β-arrestin trafficking and, moreover, activate the G-protein-dependent signaling of protein kinase CβII. Conversely, the potent synthetic cannabinoid agonist CP55,940 acts as a GPR55 antagonist/partial agonist. CP55,940 blocks GPR55 internalization, the formation of β-arrestin GPR55 complexes, and the phosphorylation of ERK1/2; CP55,940 produces only a slight amount of protein kinase CβII membrane recruitment but does not stimulate membrane remodeling like LPI, AM251, or rimonabant. Our studies provide a paradigm for measuring the responsiveness of GPR55 to a variety of ligand scaffolds comprising cannabinoid and novel compounds and suggest that at best GPR55 is an atypical cannabinoid responder. The activation of GPR55 by rimonabant may be responsible for some of the off-target effects that led to its removal as a potential obesity therapy.The CB12 and CB2 cannabinoid receptors comprise a two-member subfamily of G-protein-coupled receptors (GPCRs) that are notable as the targets of the tetrahydrocannabinol (THC) derivatives found in marijuana. More recently CB1 receptors along with other GPCRs have been promoted as therapeutic pharmacological targets in the billion dollar weight loss market for controversial drugs such as rimonabant (SR141716A) and Fen-phen. Thus, an important utility of cannabinoid family receptors to society appears to arise from their role in regulating a broad spectrum of addiction-based behaviors, and the addition of new members to the cannabinoid receptor family may have social and economic implications that reach far beyond the initial scientific discovery. As a consequence, the re-classification of an orphan GPCR as a cannabinoid family member should be done with caution requiring strict criteria of receptor activation by THC derivatives or endogenous cannabinoid compounds and a widespread agreement of the results by the scientific community.Marijuana, one of the most widely abused substances (1), mediates many of its psychotropic effects by targeting CB1 receptors in the central nervous system, but studies with CB1 and CB2 knock-out mice indicate that the complex pharmacological properties on pain, mood, and memory exhibited by exogenous cannabinoids and the endogenous arachidonic acid-based endo-cannabinoids, including anandamide and 2-arachidonoylglycerol (2-AG), are not fully explained by their activation of CB1 and CB2 (2–4). The CB1 and CB2 receptors are 44% identical and signal through Gi/o-mediated pathways. Activation of either receptor is inhibitory for cAMP production via adenylyl cyclase and stimulatory for mitogen-activated protein kinase (MAPK) (extracellular-regulated protein kinase 1/2 (ERK1/2)) activation (5). However, the failure of these two receptors to account for the full complement of physiological effects observed with cannabinoid ligands has led to the hypothesis that additional cannabinoid-like receptors exist.The orphan GPCR, GPR55, which exhibits only 10–15% homology to the two human cannabinoid receptors (6), is one of a number of plausible cannabinoid family member candidates (7). GPR55 was first identified and mapped to human chromosome 2q37 a decade ago (8). In the human central nervous system, it is predominantly localized to the caudate, putamen, and striatum (8), coupling to Gα13 (9, 10), Gα12, or Gαq (11).GPR55 has been tested against a number of cannabinoid ligands with mixed results. Observations using a GTPγS functional assay indicate that GPR55 is activated by nanomolar concentrations of the endocannabinoids 2-AG, virodhamine, noladin ether, and palmitoylethanolamine (10) and the atypical cannabinoids Abn-CBD and O-1602 (12) as well as by the drugs CP55,950, HU210, and Δ9-THC (11). Exposure of GPR55 to the cannabinoids THC and JWH015 in dorsal root ganglion neurons and in receptor-transfected HEK293 cells correlates with increases of intracellular Ca2+ (11). In contrast, GPR55 is insensitive to the CB1 inverse agonist AM281 and the potent cannabinoid agonist WIN55212-2 but is antagonized by the marijuana constituent CBD (9, 10). However, Oka et al. (13) reported that GPR55 is not a typical cannabinoid receptor, as numerous endogenous and synthetic cannabinoids, including many mentioned above, had no effect on GPR55 activity. They present compelling data suggesting that the endogenous lipid LPI and its 2-arachidonyl analogs are agonists at GPR55 as a result of their abilities to phosphorylate extracellular-regulated kinase and induce calcium signaling (13, 14). Further studies indicate that LPI and the rimonabant-like CB1 inverse agonist AM251 induce oscillatory Ca2+ release through Gα13 and RhoA (9). These reports were all performed in HEK 293 cells, yet each documented a distinct and conflicting chemical space of agonists that recognized GPR55. To resolve these inconsistencies in classification, an alternative approach for identifying GPR55 ligands that is insensitive to the endogenous complement of cellular receptors could circumvent many of the challenges that have arisen in the measurements of G-protein signaling.β-Arrestins are intracellular proteins that bind and desensitize activated GPCRs and in the process form stable receptor/arrestin signaling complexes (15, 16). β-Arrestin redistribution to the activated membrane-bound receptor represents one of the early intracellular events provoked by agonist binding and, consequently, is less prone to a false positive or negative readout as compared with studying a downstream signaling event as a readout of receptor activation. β-arrestin-green fluorescent chimeras can make this process attractive to monitor by forming remarkably sensitive and specific probes of GPCR activation that are independent of downstream G-protein-mediated signaling (17–19). We have determined GPR55 responsiveness to a representative panel of cannabinoid ligands and LPI in the presence (and absence) of a β-arrestin2-green fluorescent protein (βarr2-GFP) biosensor. Our data demonstrate that LPI, the CB1 inverse agonist/antagonists SR141716A, and AM251 are GPR55 agonists, and the CB1 agonist CP55940 is a GPR55 antagonist/partial agonist. These data together with our inability to observe activation of GPR55 by Δ9-THC and endocannabinoids indicate that GPR55 should be classified as an atypical cannabinoid receptor at best. 相似文献
18.
Andrea Behrenswerth Nicole Volz Jakob Toräng Sonja Hinz Stefan Bräse Christa E. Müller 《Bioorganic & medicinal chemistry》2009,17(7):2842-2851
In the present study we synthesized 36 coumarin and 2H-chromene derivatives applying a recently developed umpoled domino reaction using substituted salicylaldehyde and α,β-unsaturated aldehyde derivatives as starting compounds. In radioligand binding studies 5-substituted 3-benzylcoumarin derivatives showed affinity to cannabinoid CB1 and CB2 receptors and were identified as new lead structures. In further GTPγS binding studies selected compounds were shown to be antagonists or inverse agonists. 相似文献
19.
《Journal of receptor and signal transduction research》2013,33(1-4):483-495
ABSTRACTIn Chinese Hamster Ovary (CHO) cells expressing cloned human 5-hydroxy-tryptamine1A (5-HT1A) receptors, (R)-3-N,N-dicyclobutylamino-8-fluoro-[6-3H]-3,4-dihydro-2H-1-benzopyran-5-carboxamide ([3H]NAD-299) exhibited high affinity (Kd = 0.16?nM) and labeled 34% more receptors than 8-hydroxy-2-([2,3-3H]di-n-propylamino)tetralin ([3H]8-OH-DPAT). NAD-299 behaved as a silent antagonist in [35S]GTPγS binding similar to N-tert-butyl-3-(4-(2-methoxyphenyl)-piperazin-1-yl)-2-phenylpropanamide (WAY-100635) and (S)-5-fluoro-8-hydroxy-2-(di-n-propylamino)tetralin ((S)UH-301). 5-HT and 5-carboxamidotryptamine (5-CT) stimulated [35S]GTPγS binding 2.5-fold while spiperone and methiothepin inhibited [35S]GTPγS binding 1.4-fold. Furthermore, NAD-299 antagonised both the 5-HT stimulated and the spiperone inhibited [35S]GTPγS binding to basal levels. The KiL/KiH ratios for spiperone (0.66), methiothepin (0.39), WAY-100635 (0.32), (S)UH-301 (0.94), NAD-299 (1.29), NAN-190 (1.23), (S)pindolol (5.85), ipsapirone (13.1), buspirone (24.6), (±)8-OH-DPAT (47.3), flesinoxan (55.8), 5-HT (200) and 5-CT (389) correlated highly significantly with the intrinsic activity obtained with [35S] GTPγS (r = 0.97). 相似文献
20.
Maria Luisa Rojo Mariateresa Cipriano Ingegerd Söderström Kotryna Šimonytė Tommy Olsson Christopher J. Fowler 《Life sciences》2014