ABSTRACT
Clavulanic acid (CLAV) is a component of Augmentin® that preserves antibiotic efficacy by inhibiting ß-lactamase activity. It also enhances cellular glutamate uptake and is a potential CNS therapeutic. Because increased glutamate transmission in brain reward circuits facilitates methamphetamine (METH) locomotor activation and sensitization, we tested the hypothesis that CLAV inhibits acute and sensitized locomotor responses to METH in mice and investigated effects of CLAV on METH-induced changes in glutaminase, the major glutamate-producing enzyme in the brain. Acute METH (3 mg/kg) produced hyperlocomotion that was reduced by CLAV (20 mg/kg but not 10 mg/kg). Mice injected with METH (3 mg/kg) every other day for 9 d and then challenged with METH 27 d later displayed locomotor sensitization. CLAV (10 mg/kg), when injected 15 min before each METH injection during the 9-d exposure interval, blocked locomotor sensitization induced by METH challenge. In METH-sensitized mice, mRNA levels of both isoforms of glutaminase (GLS and GLS2) were altered in the nucleus accumbens compared to mice exposed to a single injection of METH (i.e., GLS decreased and GLS2 increased). CLAV normalized the METH-induced GLS deficit but not the increase in GLS2. In summary, CLAV reduced acute and sensitized locomotor responses to METH and normalized the METH-induced reduction of GLS gene expression in the NAC. Given that glutaminases belong to the ß-lactamase superfamily and CLAV is a ß-lactamase inhibitor, our data point toward studying glutaminase as a therapeutic target of CLAV.
Subject(s)
Central Nervous System Stimulants , Clavulanic Acid , Glutaminase , Methamphetamine , Nucleus Accumbens , RNA, Messenger , Animals , Methamphetamine/pharmacology , Nucleus Accumbens/drug effects , Nucleus Accumbens/metabolism , Glutaminase/metabolism , Male , Clavulanic Acid/pharmacology , RNA, Messenger/metabolism , RNA, Messenger/drug effects , Central Nervous System Stimulants/pharmacology , Mice, Inbred C57BL , Mice , Locomotion/drug effects , Motor Activity/drug effects , Dose-Response Relationship, DrugABSTRACT
Identifying biomarkers to evaluate the therapeutic effect of immune checkpoint inhibitors (ICIs) is crucial. Regulatory Associated Protein of MTOR Complex 1 (RPTOR), one of the genes in the mTOR pathway, plays a role in regulating tumor progression. However, the connection between RPTOR mutation and the efficacy of ICIs in melanoma remains unclear. The data of ICIs-treated melanoma patients in discovery (n = 384) and validation (n = 320) cohorts were obtained from cBioPortal databases. The genomic data in the two cohorts was used to investigate the connection between RPTOR mutation and immunotherapy efficacy. The underlying mechanisms were explored based on data from the The Cancer Genome Atlas (TCGA)-skin cutaneous melanoma (SKCM) cohort. Compared to melanoma patients with RPTOR wildtype (RPTOR-WT), RPTOR-mutation (RPTOR-Mut) patients achieved prolonged overall survival (OS) in both discovery cohort (median OS of 49.3 months vs. 21.7 months; HR = 0.41, 95% CI: 0.18-0.92; P = 0.026) and validation cohorts (not reached vs. 42.0 months; HR = 0.34, 95% CI: 0.11-1.06; P = 0.049). RPTOR-Mut melanoma patients exhibited a higher objective response rate (ORR) than RPTOR-WT patients in the discovery cohort (55.0% vs. 29.0%, P = 0.022). RPTOR-Mut patients exhibited higher TMB than RPTOR-WT patients in both discovery and validation cohorts (P < 0.001). RPTOR-Mut melanoma patients had an increased number of DNA damage response (DDR) mutations in TCGA-SKCM cohort. Immune cell infiltration analysis suggested that activated CD4 memory T cells were more enriched in RPTOR-Mut tumors. RPTOR-Mut melanoma patients had higher expression levels of immune-related genes than the RPTOR-WT patients. Our results suggest that RPTOR mutation could serve as a predictor of effective immunotherapy for melanoma.
Subject(s)
Melanoma , Skin Neoplasms , Humans , Melanoma/drug therapy , Melanoma/genetics , Regulatory-Associated Protein of mTOR , Skin Neoplasms/drug therapy , Skin Neoplasms/genetics , Immunotherapy , Mutation , Biomarkers, Tumor/geneticsABSTRACT
TPC2 is a pathophysiologically relevant lysosomal ion channel that is activated directly by the phosphoinositide PI(3,5)P2 and indirectly by the calcium ion (Ca2+)-mobilizing molecule NAADP through accessory proteins that associate with the channel. TPC2 toggles between PI(3,5)P2-induced, sodium ion (Na+)-selective and NAADP-induced, Ca2+-permeable states in response to these cues. To address the molecular basis of polymodal gating and ion-selectivity switching, we investigated the mechanism by which NAADP and its synthetic functional agonist, TPC2-A1-N, induced Ca2+ release through TPC2 in human cells. Whereas NAADP required the NAADP-binding proteins JPT2 and LSM12 to evoke endogenous calcium ion signals, TPC2-A1-N did not. Residues in TPC2 that bind to PI(3,5)P2 were required for channel activation by NAADP but not for activation by TPC2-A1-N. The cryptic voltage-sensing region of TPC2 was required for the actions of TPC2-A1-N and PI(3,5)P2 but not for those of NAADP. These data mechanistically distinguish natural and synthetic agonist action at TPC2 despite convergent effects on Ca2+ permeability and delineate a route for pharmacologically correcting impaired NAADP-evoked Ca2+ signals.
Subject(s)
Calcium , Cues , Humans , Permeability , Phosphatidylinositols , Research PersonnelABSTRACT
AIMS: Mitragynine (MG) is an alkaloid found in Mitragyna speciosa (kratom), a plant used to self-treat symptoms of opioid withdrawal and pain. Kratom products are commonly used in combination with cannabis, with the self-treatment of pain being a primary motivator of use. Both cannabinoids and kratom alkaloids have been characterized to alleviate symptoms in preclinical models of neuropathic pain such as chemotherapy-induced peripheral neuropathy (CIPN). However, the potential involvement of cannabinoid mechanisms in MG's efficacy in a rodent model of CIPN have yet to be explored. MAIN METHODS: Prevention of oxaliplatin-induced mechanical hypersensitivity and formalin-induced nociception were assessed following intraperitoneal administration of MG and CB1, CB2, or TRPV1 antagonists in wildtype and cannabinoid receptor knockout mice. The effects of oxaliplatin and MG exposure on the spinal cord endocannabinoid lipidome was assessed by HPLC-MS/MS. KEY FINDINGS: The efficacy of MG on oxaliplatin-induced mechanical hypersensitivity was partially attenuated upon genetic deletion of cannabinoid receptors, and completely blocked upon pharmacological inhibition of CB1, CB2, and TRPV1 channels. This cannabinoid involvement was found to be selective to a model of neuropathic pain, with minimal effects on MG-induced antinociception in a model of formalin-induced pain. Oxaliplatin was found to selectively disrupt the endocannabinoid lipidome in the spinal cord, which was prevented by repeated MG exposure. SIGNIFICANCE: Our findings suggest that cannabinoid mechanisms contribute to the therapeutic efficacy of the kratom alkaloid MG in a model of CIPN, which may result in increased therapeutic efficacy when co-administered with cannabinoids.
Subject(s)
Antineoplastic Agents , Cannabinoids , Mitragyna , Neuralgia , Secologanin Tryptamine Alkaloids , Mice , Animals , Cannabinoids/pharmacology , Endocannabinoids , Oxaliplatin , Tandem Mass Spectrometry , Antineoplastic Agents/adverse effects , Secologanin Tryptamine Alkaloids/adverse effects , Neuralgia/chemically induced , Neuralgia/drug therapy , Neuralgia/prevention & control , Receptors, CannabinoidABSTRACT
GPR55 is an orphan G-protein coupled receptor involved in various pathophysiological conditions. However, there are only a few noncannabinoid GPR55 ligands reported so far. The lack of potent and selective GPR55 ligands precludes a deep exploration of this receptor. The studies presented here focused on a thienopyrimidine scaffold based on the GPR55 antagonist ML192, previously discovered by high-throughput screening. The GPR55 activities of the new synthesized compounds were assessed using ß-arrestin recruitment assays in Chinese hamster ovary cells overexpressing human GPR55. Some derivatives were identified as GPR55 antagonists with functional efficacy and selectivity versus CB1 and CB2 cannabinoid receptors.
ABSTRACT
Riluzole, approved to manage amyotrophic lateral sclerosis, is mechanistically unique among glutamate-based therapeutics because it reduces glutamate transmission through a dual mechanism (i.e., reduces glutamate release and enhances glutamate reuptake). The profile of riluzole is favorable for normalizing glutamatergic dysregulation that perpetuates methamphetamine (METH) dependence, but pharmacokinetic and metabolic liabilities hinder repurposing. To mitigate these limitations, we synthesized troriluzole (TRLZ), a third-generation prodrug of riluzole, and tested the hypothesis that TRLZ inhibits METH hyperlocomotion and conditioned place preference (CPP) and normalizes METH-induced changes in mesolimbic glutamate biomarkers. TRLZ (8, 16 mg/kg) reduced hyperlocomotion caused by METH (1 mg/kg) without affecting spontaneous activity. TRLZ (1, 4, 8, 16 mg/kg) administered during METH conditioning (0.5 mg/kg x 4 d) inhibited development of METH place preference, and TRLZ (16 mg/kg) administered after METH conditioning reduced expression of CPP. In rats with established METH place preference, TRLZ (16 mg/kg) accelerated extinction of CPP. In cellular studies, chronic METH enhanced mRNA levels of glutamate carboxypeptidase II (GCPII) in the ventral tegmental area (VTA) and prefrontal cortex (PFC). Repeated METH also caused enhancement of GCPII protein levels in the VTA that was prevented by TRLZ (16 mg/kg). TRLZ (16 mg/kg) administered during chronic METH did not affect brain or plasma levels of METH. These results indicate that TRLZ, already in clinical trials for cerebellar ataxia, reduces development, expression and maintenance of METH CPP. Moreover, normalization of METH-induced GCPII levels in mesolimbic substrates by TRLZ points toward studying GCPII as a therapeutic target of TRLZ.
Subject(s)
Amphetamine-Related Disorders , Central Nervous System Stimulants , Methamphetamine , Rats , Animals , Methamphetamine/pharmacology , Central Nervous System Stimulants/pharmacology , Glutamate Carboxypeptidase II/therapeutic use , Riluzole/therapeutic use , Amphetamine-Related Disorders/drug therapy , Glutamates/therapeutic useABSTRACT
Background: Activation of signaling effectors by G-protein coupled receptors (GPCRs) depends on different molecular mechanisms triggered by conserved amino acid residues. Although studies have focused on the G-protein signaling state, the mechanism for ß-arrestin signaling by CB1 is not yet well defined. Studies have indicated that transmembrane helix 7 (TMH7) and the highly conserved NPXXY motif can be subject to different conformational changes in response to biased ligands and could therefore participate in a molecular mechanism to trigger ß-arrestin recruitment. Objective: To investigate the effect of mutations in the NPXXY motif on different signaling pathways activated by the CB1 receptor. Materials and Methods: Point mutations of the NPXXY motif and associated residues were generated in the CB1 receptor using site-directed mutagenesis and transfection into HEK-293 cells. Signaling by wild-type and mutant receptors was analyzed by quantifying inhibition of cAMP, and by ß-arrestin recruitment assays. Results: We found that N7.49 and Y7.53 are essential for ß-arrestin recruitment by CB1. N7.49A and Y7.53F impair ß-arrestin signaling, with no effect on G-protein signaling. We found a regulatory role for residue I2.43; I2.43 interacts with Y7.53, affecting its positioning. Reducing steric bulk at I2.43 (I2.43A) enhances ß-arrestin1 recruitment, while introducing a polar residue (I2.43T) reduces ß-arrestin recruitment. Conclusions: These findings point to a novel mechanism for ß-arrestin recruitment, implicating amino acids in the NPXXY motif as critical for the putative ß-arrestin biased conformational state of Class A GPCRs.
Subject(s)
Receptor, Cannabinoid, CB1 , beta-Arrestin 1 , Humans , beta-Arrestin 1/genetics , beta-Arrestin 1/metabolism , beta-Arrestins/metabolism , Cannabinoids , GTP-Binding Proteins/metabolism , HEK293 Cells , Receptor, Cannabinoid, CB1/genetics , Receptor, Cannabinoid, CB1/metabolism , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolismABSTRACT
The present study aimed to assess the correlation of C-X-C motif chemokine ligand (CXCL)1, CXCL2, CXCL8, CXCL13 and CXCL14 with clinicopathological features and survival profile in patients with colorectal cancer (CRC). Patients with primary CRC (n=232) were retrospectively reviewed, with their tumor tissue specimens acquired from the Department of Pathology (The First Hospital of Jilin University, Changchun, China), their demographic data and preoperative tumor features collected from the hospital database, and their survival data obtained from the follow-up documents. Tumor CXCL expression was detected by immunohistochemistry (IHC). Based on the total IHC score, the expression of CXCL1, CXCL2, CXCL8, CXCL13 and CXCL14 was categorized as low expression (IHC score ≤3) and high expression (IHC score >3). CXCL1 (51.3% high and 48.7% low), CXCL2 (59.9% high and 40.1% low), CXCL8 (44.4% high and 55.6% low), CXCL13 (40.9% high and 59.1% low) and CXCL14 (31.0% high and 69.0% low) were expressed in CRC tumor tissues, and their expression levels were correlated with each other, except between CXCL8 and CXCL14, and between CXCL13 and CXCL14. CXCL1 was associated with a larger tumor size, and an advanced T stage, N stage and Tumor-Node-Metastasis (TNM) stage. CXCL2 was associated with an advanced N stage and TNM stage, and CXCL8 was associated with a greater T stage and TNM stage. CXCL13 was associated with a greater T stage, N stage and TNM stage, while CXCL14 was not associated with any clinical characteristics. As for survival, CXCL1, CXCL2, CXCL8 and CXCL13, but not CXCL14, were associated with poor overall survival (OS) rate, and further multivariate Cox's regression model analysis revealed that CXCL1 independently predicted unfavorable OS in patients with CRC. Overall, CXCL1, CXCL2, CXCL8 and CXCL13 have good potential as an indicator for tumor features and survival in patients with CRC.
ABSTRACT
Chemokine-opioid crosstalk is a physiological crossroads for influencing therapeutic and adverse effects of opioids. Activation of chemokine receptors, especially CCR2, CCR5 and CXCR4, reduces opioid-induced analgesia by desensitizing OPRM1 receptors. Chemokine receptor antagonists (CRAs) enhance opioid analgesia, but knowledge about how CRAs impact adverse opioid effects remains limited. We examined effects of RAP-103, a multi-CRA orally active peptide analog of "DAPTA", on opioid-derived dependence, reinforcement, and respiratory depression in male rats and on changes in chemokine and OPRM1 (µ opioid) receptor levels in mesolimbic substrates during opioid abstinence. In rats exposed to chronic morphine (75 mg pellet x 7 d), daily RAP-103 (1 mg/kg, IP) treatment reduced the severity of naloxone-precipitated withdrawal responses. For self-administration (SA) studies, RAP-103 (1 mg/kg, IP) reduced heroin acquisition (0.1 mg/kg/inf) and reinforcing efficacy (assessed by motivation on a progressive-ratio reinforcement schedule) but did not impact sucrose intake. RAP-103 (1-3 mg/kg, IP) also normalized the deficits in oxygen saturation and enhancement of respiratory rate caused by morphine (5 mg/kg, SC) exposure. Abstinence from chronic morphine elicited brain-region specific changes in chemokine receptor protein levels. CCR2 and CXCR4 were increased in the ventral tegmental area (VTA), whereas CCR2 and CCR5 were reduced in the nucleus accumbens (NAC). Effects of RAP-103 (1 mg/kg, IP) were focused in the NAC, where it normalized morphine-induced deficits in CCR2 and CCR5. These results identify CRAs as potential biphasic function opioid signaling modulators to enhance opioid analgesia and inhibit opioid-derived dependence and respiratory depression.
Subject(s)
Analgesics, Opioid , Respiratory Insufficiency , Analgesics, Opioid/pharmacology , Animals , Male , Morphine/pharmacology , Nucleus Accumbens , Peptides/metabolism , Peptides/pharmacology , Rats , Receptors, Chemokine/metabolism , Receptors, Opioid , Receptors, Opioid, mu , Respiratory Insufficiency/chemically induced , Respiratory Insufficiency/drug therapyABSTRACT
The role of mast cells in colorectal cancer (CRC) has been an area of intense interest. Mast cell density is closely related to CRC development and prognosis. The identification of mast cell progenitors (MCps) in peripheral blood provides an opportunity to explore the frequency and distribution of mast cells in the circulation and tumour microenvironment of patients with CRC at different disease stages. The aim of the presents study was to investigate the changes of MCps and mast cells in CRC. Flow cytometry was used to measure the circulating frequency of MCps in 37 patients with CRC and 12 healthy control (HC) patients, and the frequency of mast cells in tissue from 15 patients with CRC and 7 patients with haemorrhoids. In the present study, lower levels of circulating MCps in patients with CRC were found, which was significantly related to CRC development. After surgery, the frequency of circulating MCps was significantly increased. However, the frequency of mast cells in tumour tissues was lower than that in adjacent normal tissues and compared with HC tissues and was not associated with CRC progression.
Subject(s)
Colorectal Neoplasms , Mast Cells , Cell Count , Colorectal Neoplasms/pathology , Humans , Mast Cells/pathology , Prognosis , Stem Cells/pathology , Tumor MicroenvironmentABSTRACT
Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX1 and OX2, Gq-coupled GPCRs. We examined the effect of a selective OX1 agonist, OXA (17-33) on cytosolic calcium concentration, [Ca2+]i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca2+]i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX1 receptors antagonist. In Ca2+-free saline, the OXA (17-33)-induced increase in [Ca2+]i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP3) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca2+]i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca2+]i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX1 via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine-orexin A interaction in nucleus accumbens neurons.
Subject(s)
Choline/metabolism , Cocaine/pharmacology , Neurons/physiology , Nucleus Accumbens/physiology , Orexin Receptors/metabolism , Orexins/metabolism , Receptors, sigma/metabolism , Animals , Animals, Newborn , Gene Expression Regulation , Neurons/drug effects , Nucleus Accumbens/drug effects , Orexin Receptors/genetics , Orexins/genetics , Rats , Rats, Sprague-Dawley , Receptors, sigma/genetics , Vasoconstrictor Agents/pharmacology , Sigma-1 ReceptorABSTRACT
Background: Circulating B cells are crucial for the pathogenesis of IgA nephropathy (IgAN). This study aimed at investigating the relationship between frequency of different subsets of circulating B cells and clinical measures in IgAN patients.Methods: The percentages of different subsets of circulating B cells in 23 IgAN patients and 14 healthy controls (HC) were determined by flow cytometry. Their serum IL-6 levels were measured by Cytometric Bead Array (CBA). Clinical parameters in five patients were measured before and after treatment for 8-12 weeks. The potential relationship between variants was analyzed.Results: In comparison with the HC, the frequency of CD3-CD19+ CD27+ IgD+IgM+ non-switched memory B cells (P = .0038) and CD3-CD19+ CD27hiCD38hi plasmablasts (P = .0467) and serum IL-6 (P = .0392) levels significantly increased in IgAN patients. The percentages of non-switched memory B cells were positively correlated with plasmablasts (R = 0.5781, P = .0039) and serum IL-6 levels (R = 0.6663, P = .0005) in the patients. The percentages of non-switched memory B cells (R = 0.8399, P < .0001), plasmablasts (R = 0.4486, P = .0318) and the levels of serum IL-6 (R = 0.5461, P = .0070) were positively correlated with the values of 24-h urine proteins in IgAN patients. The serum levels of IL-6 were negatively correlated with the eGFR values. Following standard treatment, the frequency of non-switched memory B cells and plasmablasts and the levels of 24-h urine proteins (P = .0317, P = .0079, P < .05) significantly decreased in IgAN patients.Conclusions: Abnormally higher frequency of non-switched memory B cells and plasmablasts may contribute to the pathogenesis of IgAN and be potential biomarkers for IgAN.
Subject(s)
B-Lymphocyte Subsets/immunology , Glomerulonephritis, IGA/immunology , Interleukin-6/blood , Plasma Cells/immunology , Adolescent , Adult , Aged , Female , Glomerulonephritis, IGA/blood , Glomerulonephritis, IGA/pathology , Humans , Immunologic Memory/immunology , Interleukin-6/immunology , Male , Middle Aged , Young AdultABSTRACT
Chronic hepatitis C (CHC) is associated with biological activity of T follicular helper (Tfh) cells and memory B cells (MBCs). However, the nature of Tfh cell subsets that are responsible for MBCs in CHC patients has not been evaluated. This study aimed to investigate Tfh and MBC immunity before and after direct-acting antiviral (DAA) therapy in patients with CHC. A total of 31 CHC patients and 15 healthy controls (HCs) were recruited. Individual patients were treated with sofosbuvir/ribavirin (SOF/RBV) or in combination with pegylated interferon alpha-2a (PEG-IFN-α-2a) for 12 weeks. Immunofluorescence revealed the frequency of ICOS+CD4+CXCR5+ active Tfh cells in liver tissue of CHC patients was higher than that of healthy control. Tfh and B cell co-culture experiments showed that Tfh2 cells from CHC patients have potential ability to induce B cell differentiation and IgG production. Flow cytometry showed that the frequencies of CD21-CD27+IgD- activated MBCs, ICOS+CD4+CXCR5+ activated Tfh cells, Tfh1 (IFN-γ+CD4+CXCR5+) cells, and Tfh2 (IL-4+CD4+CXCR5+) cells, but not of Tfh17 (IL-17+CD4+CXCR5+) cells, increased in CHC patients before and after DAA therapy. Collectively, ICOS+ Tfh, Tfh1, Tfh2 cells, and MBCs participated in the antiviral treatment process of SOF/RBV with or without PEG-IFN-α-2a in CHC patients, and their activity was further enhanced during the treatment. KEY MESSAGES: This study aimed to investigate Tfh cells and MBC immunity in CHC patients. CD21-CD27+IgD- activated MBCs increased in CHC patients before and after treatment. Tfh1 and Tfh2 cells increased in CHC patients before and after antiviral treatment. Intrahepatic activated Tfh cells increased in CHC patients before treatment. Tfh2 cells from CHC patients have a stronger ability to induce B cell differentiation.
Subject(s)
B-Lymphocytes/immunology , Hepatitis C, Chronic/immunology , T-Lymphocytes, Helper-Inducer/immunology , Antiviral Agents/pharmacology , Antiviral Agents/therapeutic use , B-Lymphocytes/drug effects , Cells, Cultured , Coculture Techniques , Drug Therapy, Combination , Female , Hepatitis C, Chronic/drug therapy , Humans , Interferon-alpha/pharmacology , Interferon-alpha/therapeutic use , Male , Polyethylene Glycols/pharmacology , Polyethylene Glycols/therapeutic use , Recombinant Proteins/pharmacology , Recombinant Proteins/therapeutic use , Ribavirin/pharmacology , Ribavirin/therapeutic use , Sofosbuvir/pharmacology , Sofosbuvir/therapeutic use , T-Lymphocytes, Helper-Inducer/drug effectsABSTRACT
Sigma-1 receptors (Sig-1Rs) are integral ER membrane proteins. They bind diverse ligands, including psychoactive drugs, and regulate many signaling proteins, including the inositol 1,4,5-trisphosphate receptors (IP3Rs) that release Ca2+ from the ER. The endogenous ligands of Sig-1Rs are unknown. Phospholipase D (PLD) cleaves phosphatidylcholine to choline and phosphatidic acid (PA), with PA assumed to mediate all downstream signaling. We show that choline is also an intracellular messenger. Choline binds to Sig-1Rs, it mimics other Sig-1R agonists by potentiating Ca2+ signals evoked by IP3Rs, and it is deactivated by metabolism. Receptors, by stimulating PLC and PLD, deliver two signals to IP3Rs: IP3 activates IP3Rs, and choline potentiates their activity through Sig-1Rs. Choline is also produced at synapses by degradation of acetylcholine. Choline uptake by transporters activates Sig-1Rs and potentiates Ca2+ signals. We conclude that choline is an endogenous agonist of Sig-1Rs linking extracellular stimuli, and perhaps synaptic activity, to Ca2+ signals.
Subject(s)
Calcium Signaling , Choline/metabolism , Inositol 1,4,5-Trisphosphate Receptors/metabolism , Receptors, sigma/metabolism , Animals , Cell Line , Humans , MCF-7 Cells , Mice , Phospholipase D/metabolism , Sigma-1 ReceptorABSTRACT
In this work, we explored the molecular framework of the known CB1R allosteric modulator PSNCBAM-1 with the aim to generate new bioactive analogs and to deepen the structure-activity relationships of this type of compounds. In particular, the introduction of a NH group between the pyridine ring and the phenyl nucleus generated the amino-phenyl-urea derivative SN15b that behaved as a positive allosteric modulator (PAM), increasing the CB1R binding affinity of the orthosteric ligand CP55,940. The functional activity was evaluated using serum response element (SRE) assay, which assesses the CB1R-dependent activation of the MAPK/ERK signaling pathway. SN15b and the biphenyl-urea analog SC4a significantly inhibited the response produced by CP55,940 in the low µM range, thus behaving as negative allosteric modulators (NAMs). The new derivatives presented here provide further insights about the modulation of CB1R binding and functional activity by allosteric ligands.
Subject(s)
Phenylurea Compounds/pharmacology , Pyridines/pharmacology , Receptor, Cannabinoid, CB1/metabolism , Allosteric Regulation/drug effects , Dose-Response Relationship, Drug , HEK293 Cells , Humans , Molecular Structure , Phenylurea Compounds/chemical synthesis , Phenylurea Compounds/chemistry , Pyridines/chemical synthesis , Pyridines/chemistry , Structure-Activity RelationshipABSTRACT
With the approach of the 30th year since the pioneering discovery of a cannabinoid receptor in rat brain (Devane et al., 1988), the field of cannabinoid pharmacology and physiology has impacted human physiology at multiple levels. The development of highly specific and potent orthosteric ligands, as well as the blossoming field of allosteric ligand development, has placed the endocannabinoid system in the forefront as a modulator of a multitude of physiologic processes. Reproducibility among laboratories is especially important due to the development of novel tools to investigate the role(s) of the endocannabinoid system in human physiology, and to clarify the roles for medicinal marijuana. Any definitive role in normal, or diseased states, must be satisfied through the demonstration of a specific receptor-mediated event. This chapter provides working protocols for the study of cannabinoid receptor-ligand binding, as well as immediate and downstream G protein-dependent signaling assays to assess receptor function.
Subject(s)
Receptors, Cannabinoid/physiology , Guanosine 5'-O-(3-Thiotriphosphate)/chemistry , HEK293 Cells , Humans , Protein Binding , Receptors, Cannabinoid/chemistry , Receptors, Cannabinoid/isolation & purification , Reproducibility of Results , Scintillation Counting , Signal Transduction , Sulfur Radioisotopes/chemistryABSTRACT
Interest in lipoamino acids as endogenous modulators of G-protein coupled receptors has escalated due to their involvement in a variety of physiologic processes. In particular, a role for these amino acid conjugates has emerged in the endocannabinoid system. The study presented herein investigated the effects of N-arachidonoyl glycine (NAGly) on a candidate endocannabinoid receptor, GPR55. Our novel findings reveal that NAGly induces concentration dependent increases in calcium mobilization and mitogen-activated protein kinase activities in HAGPR55/CHO cells. These increases were attenuated by the selective GPR55 antagonist ML193 (N-[4-[[(3,4-Dimethyl-5-isoxazolyl)amino]sulfonyl]phenyl]-6,8-dimethyl-2-(2-pyridinyl)-4-quinolinecarboxamide), supporting receptor mediated signaling. To our knowledge this is the first report identifying GPR55 as a target of the endogenous lipoamino acid, NAGly.
Subject(s)
Arachidonic Acids/pharmacology , Calcium/metabolism , Glycine/analogs & derivatives , Receptors, G-Protein-Coupled/genetics , Animals , CHO Cells , Cricetulus , Dose-Response Relationship, Drug , Gene Expression Regulation , Glycine/pharmacology , Humans , Inositol 1,4,5-Trisphosphate Receptors/genetics , Inositol 1,4,5-Trisphosphate Receptors/metabolism , Kinetics , Mitogen-Activated Protein Kinase 1/antagonists & inhibitors , Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/antagonists & inhibitors , Mitogen-Activated Protein Kinase 3/genetics , Mitogen-Activated Protein Kinase 3/metabolism , Quinolines/pharmacology , Receptors, Cannabinoid , Receptors, G-Protein-Coupled/agonists , Receptors, G-Protein-Coupled/metabolismABSTRACT
The first structure-activity relationships for a benzothiazole scaffold acting as an antagonist at GPR35 is presented. Analogues were designed based on a lead compound that was previously determined to have selective activity as a GPR35 antagonist. The synthetic route was modular in nature to independently explore the role of the middle and both ends of the scaffold. The activities of the analogues illustrate the importance of all three segments of the compound.
Subject(s)
Benzothiazoles/chemistry , Receptors, G-Protein-Coupled/antagonists & inhibitors , Benzothiazoles/chemical synthesis , Benzothiazoles/metabolism , Cell Line, Tumor , Humans , Inhibitory Concentration 50 , Protein Binding , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Structure-Activity RelationshipABSTRACT
GPR55 is a newly deorphanized class A G-protein-coupled receptor that has been implicated in inflammatory pain, neuropathic pain, metabolic disorder, bone development, and cancer. Few potent GPR55 ligands have been identified to date. This is largely due to an absence of information about salient features of GPR55, such as residues important for signaling and residues implicated in the GPR55 signaling cascade. The goal of this work was to identify residues that are key for the signaling of the GPR55 endogenous ligand, l-α-lysophosphatidylinositol (LPI), as well as the signaling of the GPR55 agonist, ML184 {CID 2440433, 3-[4-(2,3-dimethylphenyl)piperazine-1-carbonyl]-N,N-dimethyl-4-pyrrolidin-1-ylbenzenesulfonamide}. Serum response element (SRE) and serum response factor (SRF) luciferase assays were used as readouts for studying LPI and ML184 signaling at the GPR55 mutants. A GPR55 R* model based on the recent δ-opioid receptor (DOR) crystal structure was used to interpret the resultant mutation data. Two residues were found to be crucial for agonist signaling at GPR55, K2.60 and E3.29, suggesting that these residues form the primary interaction site for ML184 and LPI at GPR55. Y3.32F, H(170)F, and F6.55A/L mutation results suggested that these residues are part of the orthosteric binding site for ML184, while Y3.32F and H(170)F mutation results suggest that these two residues are part of the LPI binding pocket. Y3.32L, M3.36A, and F6.48A mutation results suggest the importance of a Y3.32/M3.36/F6.48 cluster in the GPR55 signaling cascade. C(10)A and C(260)A mutations suggest that these residues form a second disulfide bridge in the extracellular domain of GPR55, occluding ligand extracellular entry in the TMH1-TMH7 region of GPR55. Taken together, these results provide the first set of discrete information about GPR55 residues important for LPI and ML184 signaling and for GPR55 activation. This information should aid in the rational design of next-generation GPR55 ligands and the creation of the first high-affinity GPR55 radioligand, a tool that is sorely needed in the field.