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Pottie E, Suresh RR, Jacobson KA, Stove CP. Assay-Dependent Inverse Agonism at the A 3 Adenosine Receptor: When Neutral Is Not Neutral. ACS Pharmacol Transl Sci 2023; 6:1266-1274. [PMID: 37705594 PMCID: PMC10496142 DOI: 10.1021/acsptsci.3c00071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Indexed: 09/15/2023]
Abstract
The A3 adenosine receptor (A3AR) is implicated in a variety of (patho)physiological conditions. While most research has focused on agonists and antagonists, inverse agonism at A3AR has been scarcely studied. Therefore, this study aimed at exploring inverse agonism, using two previously engineered cell lines (hA3ARLgBiT-SmBiTβarr2 and hA3ARLgBiT-SmBiTminiGαi), both employing the NanoBiT technology. The previously established inverse agonist PSB-10 showed a decrease in basal signal in the β-arrestin 2 (βarr2) but not the miniGαi recruitment assay, indicative of inverse agonism in the former assay. Control experiments confirmed the specificity and reversibility of this observation. Evaluation of a set of presumed neutral antagonists (MRS7907, MRS7799, XAC, and MRS1220) revealed that all displayed concentration-dependent signal decreases when tested in the A3AR-βarr2 recruitment assay, yielding EC50 and Emax values for inverse agonism. Conversely, in the miniGαi recruitment assay, no signal decreases were observed. To assess whether this observation was caused by the inability of the ligands to induce inverse agonism in the G protein pathway, or rather by a limitation inherent to the employed A3AR-miniGαi recruitment assay, a GloSensor cAMP assay was performed. The outcome of the latter also suggests inverse agonism by the presumed neutral antagonists in this latter assay. These findings emphasize the importance of prior characterization of ligands in the relevant test system. Moreover, it showed the suitability of the NanoBiT βarr2 recruitment and the GloSensor cAMP assays to capture inverse agonism at the A3AR, as opposed to the NanoBiT miniGαi recruitment assay.
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Affiliation(s)
- Eline Pottie
- Laboratory
of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical
Sciences, Ghent University, Campus Heymans, Ottergemsesteenweg
460, B-9000 Ghent, Belgium
| | - R. Rama Suresh
- Laboratory
of Bioorganic Chemistry, National Institute
of Diabetes & Digestive & Kidney Diseases, National Institutes
of Health, Bethesda, Maryland 20802, United States
| | - Kenneth A. Jacobson
- Laboratory
of Bioorganic Chemistry, National Institute
of Diabetes & Digestive & Kidney Diseases, National Institutes
of Health, Bethesda, Maryland 20802, United States
| | - Christophe P. Stove
- Laboratory
of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical
Sciences, Ghent University, Campus Heymans, Ottergemsesteenweg
460, B-9000 Ghent, Belgium
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2
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Gao ZG, Auchampach JA, Jacobson KA. Species dependence of A 3 adenosine receptor pharmacology and function. Purinergic Signal 2023; 19:523-550. [PMID: 36538251 PMCID: PMC9763816 DOI: 10.1007/s11302-022-09910-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 11/26/2022] [Indexed: 12/24/2022] Open
Abstract
Efforts to fully understand pharmacological differences between G protein-coupled receptor (GPCR) species homologues are generally not pursued in detail during the drug development process. To date, many GPCRs that have been successfully targeted are relatively well-conserved across species in amino acid sequence and display minimal variability of biological effects. However, the A3 adenosine receptor (AR), an exciting drug target for a multitude of diseases associated with tissue injury, ischemia, and inflammation, displays as little as 70% sequence identity among mammalian species (e.g., rodent vs. primate) commonly used in drug development. Consequently, the pharmacological properties of synthetic A3AR ligands vary widely, not only in binding affinity, selectivity, and signaling efficacy, but to the extent that some function as agonists in some species and antagonists in others. Numerous heterocyclic antagonists that have nM affinity at the human A3AR are inactive or weakly active at the rat and mouse A3ARs. Positive allosteric modulators, including the imidazo [4,5-c]quinolin-4-amine derivative LUF6000, are only active at human and some larger animal species that have been evaluated (rabbit and dog), but not rodents. A3AR agonists evoke systemic degranulation of rodent, but not human mast cells. The rat A3AR undergoes desensitization faster than the human A3AR, but the human homologue can be completely re-sensitized and recycled back to the cell surface. Thus, comprehensive pharmacological evaluation and awareness of potential A3AR species differences are critical in studies to further understand the basic biological functions of this unique AR subtype. Recombinant A3ARs from eight different species have been pharmacologically characterized thus far. In this review, we describe in detail current knowledge of species differences in genetic identity, G protein-coupling, receptor regulation, and both orthosteric and allosteric A3AR pharmacology.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0810, USA.
| | - John A Auchampach
- Department of Pharmacology and Toxicology, and the Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0810, USA.
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3
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Nucleoside transporters and immunosuppressive adenosine signaling in the tumor microenvironment: Potential therapeutic opportunities. Pharmacol Ther 2022; 240:108300. [PMID: 36283452 DOI: 10.1016/j.pharmthera.2022.108300] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/17/2022] [Accepted: 10/19/2022] [Indexed: 11/30/2022]
Abstract
Adenosine compartmentalization has a profound impact on immune cell function by regulating adenosine localization and, therefore, extracellular signaling capabilities, which suppresses immune cell function in the tumor microenvironment. Nucleoside transporters, responsible for the translocation and cellular compartmentalization of hydrophilic adenosine, represent an understudied yet crucial component of adenosine disposition in the tumor microenvironment. In this review article, we will summarize what is known regarding nucleoside transporter's function within the purinome in relation to currently devised points of intervention (i.e., ectonucleotidases, adenosine receptors) for cancer immunotherapy, alterations in nucleoside transporter expression reported in cancer, and potential avenues for targeting of nucleoside transporters for the desired modulation of adenosine compartmentalization and action. Further, we put forward that nucleoside transporters are an unexplored therapeutic opportunity, and modulation of nucleoside transport processes could attenuate the pathogenic buildup of immunosuppressive adenosine in solid tumors, particularly those enriched with nucleoside transport proteins.
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IJzerman AP, Jacobson KA, Müller CE, Cronstein BN, Cunha RA. International Union of Basic and Clinical Pharmacology. CXII: Adenosine Receptors: A Further Update. Pharmacol Rev 2022; 74:340-372. [PMID: 35302044 PMCID: PMC8973513 DOI: 10.1124/pharmrev.121.000445] [Citation(s) in RCA: 56] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Our previous International Union of Basic and Clinical Pharmacology report on the nomenclature and classification of adenosine receptors (2011) contained a number of emerging developments with respect to this G protein-coupled receptor subfamily, including protein structure, protein oligomerization, protein diversity, and allosteric modulation by small molecules. Since then, a wealth of new data and results has been added, allowing us to explore novel concepts such as target binding kinetics and biased signaling of adenosine receptors, to examine a multitude of receptor structures and novel ligands, to gauge new pharmacology, and to evaluate clinical trials with adenosine receptor ligands. This review should therefore be considered a further update of our previous reports from 2001 and 2011. SIGNIFICANCE STATEMENT: Adenosine receptors (ARs) are of continuing interest for future treatment of chronic and acute disease conditions, including inflammatory diseases, neurodegenerative afflictions, and cancer. The design of AR agonists ("biased" or not) and antagonists is largely structure based now, thanks to the tremendous progress in AR structural biology. The A2A- and A2BAR appear to modulate the immune response in tumor biology. Many clinical trials for this indication are ongoing, whereas an A2AAR antagonist (istradefylline) has been approved as an anti-Parkinson agent.
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Affiliation(s)
- Adriaan P IJzerman
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands (A.P.IJ.); National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Molecular Recognition Section, Bethesda, Maryland (K.A.J.); Universität Bonn, Bonn, Germany (C.E.M.); New York University School of Medicine, New York, New York (B.N.C.); and Center for Neurosciences and Cell Biology and Faculty of Medicine, University of Coimbra, Coimbra, Portugal (R.A.C.)
| | - Kenneth A Jacobson
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands (A.P.IJ.); National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Molecular Recognition Section, Bethesda, Maryland (K.A.J.); Universität Bonn, Bonn, Germany (C.E.M.); New York University School of Medicine, New York, New York (B.N.C.); and Center for Neurosciences and Cell Biology and Faculty of Medicine, University of Coimbra, Coimbra, Portugal (R.A.C.)
| | - Christa E Müller
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands (A.P.IJ.); National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Molecular Recognition Section, Bethesda, Maryland (K.A.J.); Universität Bonn, Bonn, Germany (C.E.M.); New York University School of Medicine, New York, New York (B.N.C.); and Center for Neurosciences and Cell Biology and Faculty of Medicine, University of Coimbra, Coimbra, Portugal (R.A.C.)
| | - Bruce N Cronstein
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands (A.P.IJ.); National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Molecular Recognition Section, Bethesda, Maryland (K.A.J.); Universität Bonn, Bonn, Germany (C.E.M.); New York University School of Medicine, New York, New York (B.N.C.); and Center for Neurosciences and Cell Biology and Faculty of Medicine, University of Coimbra, Coimbra, Portugal (R.A.C.)
| | - Rodrigo A Cunha
- Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands (A.P.IJ.); National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Molecular Recognition Section, Bethesda, Maryland (K.A.J.); Universität Bonn, Bonn, Germany (C.E.M.); New York University School of Medicine, New York, New York (B.N.C.); and Center for Neurosciences and Cell Biology and Faculty of Medicine, University of Coimbra, Coimbra, Portugal (R.A.C.)
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Kotulova J, Lonova K, Kubickova A, Vrbkova J, Kourilova P, Hajduch M, Dzubak P. 2‑Cl‑IB‑MECA regulates the proliferative and drug resistance pathways, and facilitates chemosensitivity in pancreatic and liver cancer cell lines. Int J Mol Med 2022; 49:31. [PMID: 35039871 PMCID: PMC8788926 DOI: 10.3892/ijmm.2022.5086] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 12/14/2021] [Indexed: 12/24/2022] Open
Abstract
Specific A3 adenosine receptor (A3AR) agonist, 2-chloro-N6-(3-iodobenzyl)-5′-N-methylcarboxamidoadenosine (2-Cl-IB-MECA), demonstrates anti-proliferative effects on various types of tumor. In the present study, the cytotoxicity of 2-Cl-IB-MECA was analyzed in a panel of tumor and non-tumor cell lines and its anticancer mechanisms in JoPaca-1 pancreatic and Hep-3B hepatocellular carcinoma cell lines were also investigated. Initially, decreased tumor cell proliferation, cell accumulation in the G1 phase and inhibition of DNA and RNA synthesis was found. Furthermore, western blot analysis showed decreased protein expression level of β-catenin, patched1 (Ptch1) and glioma-associated oncogene homolog zinc finger protein 1 (Gli1), which are components of the Wnt/β-catenin and Sonic hedgehog/Ptch/Gli transduction pathways. In concordance with these findings, the protein expression levels of cyclin D1 and c-Myc were reduced. Using a luciferase assay, it was revealed for the first time a decrease in β-catenin transcriptional activity, as an early event following 2-Cl-IB-MECA treatment. In addition, the protein expression levels of multidrug resistance-associated protein 1 and P-glycoprotein (P-gp) were reduced and the P-gp xenobiotic efflux function was also reduced. Next, the enhancing effects of 2-Cl-IB-MECA on the cytotoxicity of conventional chemotherapy was investigated. It was found that 2-Cl-IB-MECA enhanced carboplatin and doxorubicin cytotoxic effects in the JoPaca-1 and Hep-3B cell lines, and a greater synergy was found in the highly tumorigenic JoPaca-1 cell line. This provides a novel in vitro rationale for the utiliza- tion of 2-Cl-IB-MECA in combination with chemotherapeutic agents, not only for hepatocellular carcinoma, but also for pancreatic cancer. Other currently used conventional chemo- therapeutics, fluorouracil and gemcitabine, showed synergy only when combined with high doses of 2-Cl-IB-MECA. Notably, experiments with A3AR-specific antagonist, N-[9-Chloro-2-(2-furanyl)(1,2,4)-triazolo(1,5-c)quinazolin-5-yl] benzene acetamide, revealed that 2-Cl-IB-MECA had antitumor effects via both A3AR-dependent and -independent pathways. In conclusion, the present study identified novel antitumor mechanisms of 2-Cl-IB-MECA in pancreatic and hepatocellular carcinoma in vitro that further underscores the importance of A3AR agonists in cancer therapy.
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Affiliation(s)
- Jana Kotulova
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Katerina Lonova
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Agata Kubickova
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Jana Vrbkova
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Pavla Kourilova
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Marian Hajduch
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
| | - Petr Dzubak
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, 77900 Olomouc, Czech Republic
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Pharmacological characterization of DPTN and other selective A 3 adenosine receptor antagonists. Purinergic Signal 2021; 17:737-746. [PMID: 34713378 DOI: 10.1007/s11302-021-09823-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/19/2021] [Indexed: 10/20/2022] Open
Abstract
The A3 adenosine receptor (AR) is emerging as an attractive drug target. Antagonists are proposed for the potential treatment of glaucoma and asthma. However, currently available A3AR antagonists are potent in human and some large animals, but weak or inactive in mouse and rat. In this study, we re-synthesized a previously reported A3AR antagonist, DPTN, and evaluated its affinity and selectivity at human, mouse, and rat ARs. We showed that DPTN, indeed, is a potent A3AR antagonist for all three species tested, albeit a little less selective for mouse and rat A3AR in comparison to the human A3AR. DPTN's Ki values at respective A1, A2A, A2B, and A3 receptors were (nM) 162, 121, 230, and 1.65 (human); 411, 830, 189, and 9.61 (mouse); and 333, 1147, 163, and 8.53 (rat). Its antagonist activity at both human and mouse A3ARs was confirmed in a cyclic AMP functional assay. Considering controversial use of currently commercially available A3AR antagonists in rats and mice, we also re-examined other commonly used and selective A3AR antagonists under the same experimental conditions. The Ki values of MRS1523 were shown to be 43.9, 349, and 216 nM at human, mouse, and rat A3ARs, respectively. MRS1191 and MRS1334 showed incomplete inhibition of [125I]I-AB-MECA binding to mouse and rat A3ARs, while potent human A3AR antagonists, MRS1220, MRE3008F20, PSB10, PSB-11, and VUF5574 were largely inactive. Thus, we demonstrated that DPTN and MRS1523 are among the only validated A3AR antagonists that can be possibly used (at an appropriate concentration) in mouse or rat to confirm an A3AR-related mechanism or function.
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Abstract
Extracellular nucleosides and nucleotides have widespread functions in responding to physiological stress. The "purinome" encompasses 4 G-protein-coupled receptors (GPCRs) for adenosine, 8 GPCRs activated by nucleotides, 7 adenosine 5'-triphosphate-gated P2X ion channels, as well as the associated enzymes and transporters that regulate native agonist levels. Purinergic signaling modulators, such as receptor agonists and antagonists, have potential for treating chronic pain. Adenosine and its analogues potently suppress nociception in preclinical models by activating A1 and/or A3 adenosine receptors (ARs), but safely harnessing this pathway to clinically treat pain has not been achieved. Both A2AAR agonists and antagonists are efficacious in pain models. Highly selective A3AR agonists offer a novel approach to treat chronic pain. We have explored the structure activity relationship of nucleoside derivatives at this subtype using a computational structure-based approach. Novel A3AR agonists for pain control containing a bicyclic ring system (bicyclo [3.1.0] hexane) in place of ribose were designed and screened using an in vivo phenotypic model, which reflected both pharmacokinetic and pharmacodynamic parameters. High specificity (>10,000-fold selective for A3AR) was achieved with the aid of receptor homology models based on related GPCR structures. These A3AR agonists are well tolerated in vivo and highly efficacious in models of chronic neuropathic pain. Furthermore, signaling molecules acting at P2X3, P2X4, P2X7, and P2Y12Rs play critical roles in maladaptive pain neuroplasticity, and their antagonists reduce chronic or inflammatory pain, and, therefore, purine receptor modulation is a promising approach for future pain therapeutics. Structurally novel antagonists for these nucleotide receptors were discovered recently.
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McNeill SM, Baltos JA, White PJ, May LT. Biased agonism at adenosine receptors. Cell Signal 2021; 82:109954. [PMID: 33610717 DOI: 10.1016/j.cellsig.2021.109954] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/11/2021] [Accepted: 02/13/2021] [Indexed: 01/14/2023]
Abstract
Adenosine modulates many aspects of human physiology and pathophysiology through binding to the adenosine family of G protein-coupled receptors, which are comprised of four subtypes, the A1R, A2AR, A2BR and A3R. Modulation of adenosine receptor function by exogenous agonists, antagonists and allosteric modulators can be beneficial for a number of conditions including cardiovascular disease, Parkinson's disease, and cancer. Unfortunately, many preclinical drug candidates targeting adenosine receptors have failed in clinical trials due to limited efficacy and/or severe on-target undesired effects. To overcome the key barriers typically encountered when transitioning adenosine receptor ligands into the clinic, research efforts have focussed on exploiting the phenomenon of biased agonism. Biased agonism provides the opportunity to develop ligands that favour therapeutic signalling pathways, whilst avoiding signalling associated with on-target undesired effects. Recent studies have begun to define the structure-function relationships that underpin adenosine receptor biased agonism and establish how this phenomenon can be harnessed therapeutically. In this review we describe the recent advancements made towards achieving therapeutically relevant biased agonism at adenosine receptors.
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Affiliation(s)
- Samantha M McNeill
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia
| | - Jo-Anne Baltos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia; Department of Pharmacology, Monash University, Melbourne, VIC, Australia.
| | - Paul J White
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia
| | - Lauren T May
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia; Department of Pharmacology, Monash University, Melbourne, VIC, Australia.
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Pottie E, Tosh DK, Gao ZG, Jacobson KA, Stove CP. Assessment of biased agonism at the A 3 adenosine receptor using β-arrestin and miniGα i recruitment assays. Biochem Pharmacol 2020; 177:113934. [PMID: 32224136 DOI: 10.1016/j.bcp.2020.113934] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/23/2020] [Indexed: 12/12/2022]
Abstract
The A3 adenosine receptor (A3AR) is a G protein-coupled receptor that is involved in a wide variety of physiological and pathological processes, such as cancer. However, the use of compounds pharmacologically targeting this receptor remains limited in clinical practice, despite extensive efforts for compound synthesis. Moreover, the possible occurrence of biased agonism further complicates the interpretation of the functional characteristics of compounds. Hence the need for simple assays, which are comparable in terms of the used cell lines and read-out technique. We previously established a stable β-arrestin 2 (βarr2) bioassay, employing a simple, luminescent read-out via functional complementation of a split nanoluciferase enzyme. Here, we developed a complementary, new bioassay in which coupling of an engineered miniGαi protein to activated A3AR is monitored using a similar approach. Application of both bioassays for the concurrent determination of the potencies and efficacies of a set of 19 N6-substituted adenosine analogues not only allowed for the characterization of structure-activity relationships, but also for the quantification of biased agonism. Although a broad distribution in potency and efficacy values was obtained within the test panel, no significant bias was observed toward either the βarr2 or miniGαi pathway.
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Affiliation(s)
- Eline Pottie
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Campus Heymans, Ottergemsesteenweg 460, B-9000 Ghent, Belgium
| | - Dilip K Tosh
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD 20802, USA
| | - Zhan-Guo Gao
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD 20802, USA
| | - Kenneth A Jacobson
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD 20802, USA
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Campus Heymans, Ottergemsesteenweg 460, B-9000 Ghent, Belgium.
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Park CW, Han CT, Sakaguchi Y, Lee J, Youn HY. Safety evaluation of FM101, an A3 adenosine receptor modulator, in rat, for developing as therapeutics of glaucoma and hepatitis. EXCLI JOURNAL 2020; 19:187-200. [PMID: 32256265 PMCID: PMC7105940 DOI: 10.17179/excli2019-2058] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/05/2020] [Indexed: 12/16/2022]
Abstract
Adenosine is a critical regulator of inflammation and fibrosis, it affects endogenous cell signaling via binding to the A3 adenosine receptor. FM101 is a potent, highly selective A3 adenosine receptor modulator that has been developed as a treatment for glaucoma and hepatitis. We determined that FM101 is a biased ligand with functional activities both as a G protein agonist and a β-arrestin antagonist. The safety of FM101 was evaluated by administering an acute dose in rats, the results indicated that the approximate lethal dose was greater than 2000 mg/kg. In a subchronic toxicity study, FM101 was administered orally once per day to rats at doses of 250, 500, and 1000 mg/kg/day over a period of 28 days. Abnormal posture, irregular respiration, decreased movement, and ear flushing were observed during the early phase of dosing, and loose stools were observed sporadically among the animals that received 500 and 1000 mg/kg/day. Body weight and food consumption were decreased in one male and one female rat in the 1000 mg/kg/day group during the first 2 weeks of observation. However, there were no test substance-related changes or adverse effects observed during our ophthalmological, clinical chemistry, urine, organ weight, and histopathological analysis. These findings indicate that no observed adverse effect level of FM101 was 1000 mg/kg/day in male and female rats.
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Affiliation(s)
- Chong-Woo Park
- R&D Center, Futuremedicine Co., Ltd., Seongnam, Republic of Korea.,Laboratory of Veterinary Internal Medicine, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea
| | | | | | - Jiyoun Lee
- R&D Center, Futuremedicine Co., Ltd., Seongnam, Republic of Korea
| | - Hwa-Young Youn
- Laboratory of Veterinary Internal Medicine, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea
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Tan A, Babak MV, Venkatesan G, Lim C, Klotz KN, Herr DR, Cheong SL, Federico S, Spalluto G, Ong WY, Chen YZ, Loo JSE, Pastorin G. Design, Synthesis and Evaluation of New Indolylpyrimidylpiperazines for Gastrointestinal Cancer Therapy. Molecules 2019; 24:E3661. [PMID: 31614517 PMCID: PMC6832257 DOI: 10.3390/molecules24203661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/04/2019] [Accepted: 10/08/2019] [Indexed: 11/29/2022] Open
Abstract
Human A3 adenosine receptor hA3AR has been implicated in gastrointestinal cancer, where its cellular expression has been found increased, thus suggesting its potential as a molecular target for novel anticancer compounds. Observation made in our previous work indicated the importance of the carbonyl group of amide in the indolylpyrimidylpiperazine (IPP) for its human A2A adenosine receptor (hA2AAR) subtype binding selectivity over the other AR subtypes. Taking this observation into account, we structurally modified an indolylpyrimidylpiperazine (IPP) scaffold, 1 (a non-selective adenosine receptors' ligand) into a modified IPP (mIPP) scaffold by switching the position of the carbonyl group, resulting in the formation of both ketone and tertiary amine groups in the new scaffold. Results showed that such modification diminished the A2A activity and instead conferred hA3AR agonistic activity. Among the new mIPP derivatives (3-6), compound 4 showed potential as a hA3AR partial agonist, with an Emax of 30% and EC50 of 2.89 ± 0.55 μM. In the cytotoxicity assays, compound 4 also exhibited higher cytotoxicity against both colorectal and liver cancer cells as compared to normal cells. Overall, this new series of compounds provide a promising starting point for further development of potent and selective hA3AR partial agonists for the treatment of gastrointestinal cancers.
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Affiliation(s)
- Aaron Tan
- NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences, #05-01, 28 Medical Drive, Singapore 117456, Singapore.
| | - Maria V Babak
- Department of Pharmacy, National University of Singapore, Singapore 119260, Singapore.
| | | | - Clarissa Lim
- Department of Pharmacy, National University of Singapore, Singapore 119260, Singapore.
| | - Karl-Norbert Klotz
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, 97078 Würzburg, Germany.
| | - Deron Raymond Herr
- Department of Pharmacology, National University of Singapore, Singapore 117600, Singapore.
| | - Siew Lee Cheong
- Department of Pharmaceutical Chemistry, School of Pharmacy, International Medical University, 126 Jalan Jalil Perkasa 19, Bukit Jalil, Kuala Lumpur 57000, Malaysia.
| | - Stephanie Federico
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, 34127 Trieste, Italy.
| | - Giampiero Spalluto
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, 34127 Trieste, Italy.
| | - Wei-Yi Ong
- Department of Anatomy, National University of Singapore, Singapore 119260, Singapore.
| | - Yu Zong Chen
- Department of Pharmacy, National University of Singapore, Singapore 119260, Singapore.
| | - Jason Siau Ee Loo
- School of Pharmacy, Faculty of Health and Medical Sciences, Taylor's University, 1, Jalan Taylors, Subang Jaya, Selangor 47500, Malaysia.
| | - Giorgia Pastorin
- NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences, #05-01, 28 Medical Drive, Singapore 117456, Singapore.
- Department of Pharmacy, National University of Singapore, Singapore 119260, Singapore.
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Probing structure-activity relationship in β-arrestin2 recruitment of diversely substituted adenosine derivatives. Biochem Pharmacol 2018; 158:103-113. [PMID: 30292756 DOI: 10.1016/j.bcp.2018.10.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 10/02/2018] [Indexed: 12/18/2022]
Abstract
In the adenosine receptor (AR) subfamily of G protein-coupled receptors (GPCRs), biased agonism has been described for the human A1AR, A2BAR and A3AR. While diverse A3AR agonists have been evaluated for receptor binding and Gi-mediated cAMP signalling, the β-arrestin2 (βarr2) pathway has been left largely unexplored. We screened nineteen diverse adenosine derivatives for βarr2 recruitment using a stable hA3AR-NanoBit®-βarr2 HEK293T cell line. Their activity profiles were compared with a cAMP accumulation assay in stable hA3AR CHO cells. Structural features linked to βarr2 activation were further investigated by the evaluation of an additional ten A3AR ligands. The A3AR-selective reference agonist 2-Cl-IB-MECA, which is a full agonist in terms of cAMP inhibition, only showed partial agonist behaviour in βarr2 recruitment. Highly A3AR-selective (N)-methanocarba 5'-uronamide adenosine derivatives displayed higher potency in both cAMP signalling and βarr2 recruitment than reference agonists NECA and 2-Cl-IB-MECA. Their A3AR-preferred conformation tolerates C2-position substitutions, for increased βarr2 efficacy, better than the flexible scaffolds of ribose derivatives. The different amino functionalities in the adenosine scaffold of these derivatives each seem to be important for signalling as well. In conclusion, we have provided insights into ligand features that can help to guide the future therapeutic development of biased A3AR ligands with respect to G-protein and βarr2 signalling.
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Vecchio EA, Baltos JA, Nguyen ATN, Christopoulos A, White PJ, May LT. New paradigms in adenosine receptor pharmacology: allostery, oligomerization and biased agonism. Br J Pharmacol 2018; 175:4036-4046. [PMID: 29679502 DOI: 10.1111/bph.14337] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 03/29/2018] [Accepted: 04/04/2018] [Indexed: 12/17/2022] Open
Abstract
Adenosine receptors are a family of GPCRs containing four subtypes (A1 , A2A , A2B and A3 receptors), all of which bind the ubiquitous nucleoside adenosine. These receptors play an important role in physiology and pathophysiology and therefore represent attractive drug targets for a range of conditions. The theoretical framework surrounding drug action at adenosine receptors now extends beyond the notion of prototypical agonism and antagonism to encompass more complex pharmacological concepts. New paradigms include allostery, in which ligands bind a topographically distinct receptor site from that of the endogenous agonist, homomeric or heteromeric interactions across receptor oligomers and biased agonism, that is, ligand-dependent differential intracellular signalling. This review provides a concise overview of allostery, oligomerization and biased agonism at adenosine receptors and outlines how these paradigms may enhance future drug discovery endeavours focussed on the development of novel therapeutic agents acting at adenosine receptors. LINKED ARTICLES This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.
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Affiliation(s)
- Elizabeth A Vecchio
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.,Department of Pharmacology, Monash University, Melbourne, VIC, Australia
| | - Jo-Anne Baltos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.,Department of Pharmacology, Monash University, Melbourne, VIC, Australia
| | - Anh T N Nguyen
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.,Department of Pharmacology, Monash University, Melbourne, VIC, Australia
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.,Department of Pharmacology, Monash University, Melbourne, VIC, Australia
| | - Paul J White
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia
| | - Lauren T May
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.,Department of Pharmacology, Monash University, Melbourne, VIC, Australia
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Storme J, Cannaert A, Van Craenenbroeck K, Stove CP. Molecular dissection of the human A 3 adenosine receptor coupling with β-arrestin2. Biochem Pharmacol 2018; 148:298-307. [PMID: 29309765 DOI: 10.1016/j.bcp.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 01/03/2018] [Indexed: 02/07/2023]
Abstract
Besides classical G protein coupling, G protein-coupled receptors (GPCRs) are nowadays well known to show significant signalling via other adaptor proteins, such as β-arrestin2 (βarr2). The elucidation of the molecular mechanism of the GPCR-βarr2 interaction is a prerequisite for the structure-activity based design of biased ligands, which introduces a new chapter in drug discovery. The general mechanism of the interaction is believed to rely on phosphorylation sites, exposed upon agonist binding. However, it is not known whether this mechanism is universal throughout the GPCR family or if GPCR-specific patterns are involved. In recent years, promising orally active agonists for the human A3 adenosine receptor (A3AR), a GPCR highly expressed in inflammatory and cancer cells, have been evaluated in clinical trials for the treatment of rheumatoid arthritis, psoriasis, and hepatocellular carcinoma. In this study, the effect of cytoplasmic modifications of the A3AR on βarr2 recruitment was evaluated in transiently transfected HEK293T cells, using a live-cell split-reporter system (NanoBit®, Promega), based on the structural complementation of NanoLuc luciferase, allowing real-time βarr2 monitoring. The A3AR-selective reference agonist 2-Cl-IB-MECA yielded a robust, concentration dependent (5 nM-1 µM) recruitment of βarr2 (logEC50: -7.798 ± 0.076). The role of putative phosphorylation sites, located in the C-terminal part and cytoplasmic loops, and the role of the 'DRY' motif was evaluated. It was shown that the A3AR C-terminus was dispensable for βarr2 recruitment. This contrasts with studies in the past for the rat A3AR, which pointed at crucial C-terminal phosphorylation sites. When combining truncation of the A3AR with modification of the 'DRY' motif to 'AAY', the βarr2 recruitment was drastically reduced. Recruitment could be partly rescued by back-mutation to 'NQY', or by extending the C-terminus again. In conclusion, other parts of the human A3AR, either cytosolic or exposed upon receptor activation, rather than the C-terminus alone, are responsible for βarr2 recruitment in a complementary or synergistic way.
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Affiliation(s)
- Jolien Storme
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Annelies Cannaert
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Kathleen Van Craenenbroeck
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.
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15
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Gao ZG, Jacobson KA. Distinct Signaling Patterns of Allosteric Antagonism at the P2Y 1 Receptor. Mol Pharmacol 2017; 92:613-626. [PMID: 28864555 DOI: 10.1124/mol.117.109660] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 08/30/2017] [Indexed: 12/18/2022] Open
Abstract
Traditionally, G protein-coupled receptor antagonists are classified as competitive or noncompetitive and surmountable or insurmountable based on functional antagonism. P2Y1 receptor (P2Y1R) structures showed two antagonists binding to two spatially distinct sites: nucleotide MRS2500 (orthosteric, contacting the helical bundle) and urea BPTU (allosteric, on the external receptor surface). However, the nature of their P2Y1R antagonism has not been characterized. Here we characterized BPTU antagonism at various signaling pathways activated by structurally diverse agonists. BPTU rightward shifted the concentration-response curves of both 2-methylthioadenosine 5'-diphosphate trisodium salt and MRS2365 (5'-diphosphates) in some signaling events, such as extracellular signal-regulated kinase 1/2 and label free, in a parallel manner without affecting the maximum agonist effect (Emax) but antagonized insurmountably (suppressed agonist Emax) in signaling events such as guanosine 5'-3-O-(thio)triphosphate binding and β-arrestin2 recruitment. However, with dinucleotide Ap4A as an agonist, BPTU suppressed the Emax insurmountably in all signaling pathways. By comparison, MRS2500 behaved as surmountable antagonist rightward-shifting concentration-response curves of all three agonists in a parallel manner for all signaling pathways measured. Thus, we demonstrated a previously undocumented phenomenon that P2Y1R antagonism patterns could vary in different signaling pathways, which could be related to conformational selection, signaling amplification, and probe dependence. This phenomenon may apply generally to other receptors considering that antagonism by a specific ligand is often not compared at multiple signaling pathways. Thus, antagonism can be surmountable or insurmountable depending on the signaling pathways measured and the agonists used, which should be of broad relevance to drug discovery and disease treatment.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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Baltos JA, Paoletta S, Nguyen ATN, Gregory KJ, Tosh DK, Christopoulos A, Jacobson KA, May LT. Structure-Activity Analysis of Biased Agonism at the Human Adenosine A3 Receptor. Mol Pharmacol 2016; 90:12-22. [PMID: 27136943 DOI: 10.1124/mol.116.103283] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 04/29/2016] [Indexed: 02/06/2023] Open
Abstract
Biased agonism at G protein-coupled receptors (GPCRs) has significant implications for current drug discovery, but molecular determinants that govern ligand bias remain largely unknown. The adenosine A3 GPCR (A3AR) is a potential therapeutic target for various conditions, including cancer, inflammation, and ischemia, but for which biased agonism remains largely unexplored. We now report the generation of bias "fingerprints" for prototypical ribose containing A3AR agonists and rigidified (N)-methanocarba 5'-N-methyluronamide nucleoside derivatives with regard to their ability to mediate different signaling pathways. Relative to the reference prototypical agonist IB-MECA, (N)-methanocarba 5'-N-methyluronamide nucleoside derivatives with significant N(6) or C2 modifications, including elongated aryl-ethynyl groups, exhibited biased agonism. Significant positive correlation was observed between the C2 substituent length (in Å) and bias toward cell survival. Molecular modeling suggests that extended C2 substituents on (N)-methanocarba 5'-N-methyluronamide nucleosides promote a progressive outward shift of the A3AR transmembrane domain 2, which may contribute to the subset of A3AR conformations stabilized on biased agonist binding.
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Affiliation(s)
- Jo-Anne Baltos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Silvia Paoletta
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Anh T N Nguyen
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Karen J Gregory
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Dilip K Tosh
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Kenneth A Jacobson
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
| | - Lauren T May
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia (J.-A.B., A.T.N.N., K.J.G., A.C., L.T.M); and Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland (S.P., D.K.T., K.A.J)
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Abstract
G protein-coupled receptors (GPCRs) remain a major domain of pharmaceutical discovery. The identification of GPCR lead compounds and their optimization are now structure-based, thanks to advances in X-ray crystallography, molecular modeling, protein engineering and biophysical techniques. In silico screening provides useful hit molecules. New pharmacological approaches to tuning the pleotropic action of GPCRs include: allosteric modulators, biased ligands, GPCR heterodimer-targeted compounds, manipulation of polypharmacology, receptor antibodies and tailoring of drug molecules to fit GPCR pharmacogenomics. Measurements of kinetics and drug efficacy are factors influencing clinical success. With the exception of inhibitors of GPCR kinases, targeting of intracellular GPCR signaling or receptor cycling for therapeutic purposes remains a futuristic concept. New assay approaches are more efficient and multidimensional: cell-based, label-free, fluorescence-based assays, and biosensors. Tailoring GPCR drugs to a patient's genetic background is now being considered. Chemoinformatic tools can predict ADME-tox properties. New imaging technology visualizes drug action in vivo. Thus, there is reason to be optimistic that new technology for GPCR ligand discovery will help reverse the current narrowing of the pharmaceutical pipeline.
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Affiliation(s)
- Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8A, Rm. B1A-19, Bethesda, Maryland 20892, USA.
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18
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Chen JF, Lee CF, Chern Y. Adenosine receptor neurobiology: overview. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 119:1-49. [PMID: 25175959 DOI: 10.1016/b978-0-12-801022-8.00001-5] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Adenosine is a naturally occurring nucleoside that is distributed ubiquitously throughout the body as a metabolic intermediary. In the brain, adenosine functions as an important upstream neuromodulator of a broad spectrum of neurotransmitters, receptors, and signaling pathways. By acting through four G-protein-coupled receptors, adenosine contributes critically to homeostasis and neuromodulatory control of a variety of normal and abnormal brain functions, ranging from synaptic plasticity, to cognition, to sleep, to motor activity to neuroinflammation, and cell death. This review begun with an overview of the gene and genome structure and the expression pattern of adenosine receptors (ARs). We feature several new developments over the past decade in our understanding of AR functions in the brain, with special focus on the identification and characterization of canonical and noncanonical signaling pathways of ARs. We provide an update on functional insights from complementary genetic-knockout and pharmacological studies on the AR control of various brain functions. We also highlight several novel and recent developments of AR neurobiology, including (i) recent breakthrough in high resolution of three-dimension structure of adenosine A2A receptors (A2ARs) in several functional status, (ii) receptor-receptor heterodimerization, (iii) AR function in glial cells, and (iv) the druggability of AR. We concluded the review with the contention that these new developments extend and strengthen the support for A1 and A2ARs in brain as therapeutic targets for neurologic and psychiatric diseases.
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Affiliation(s)
- Jiang-Fan Chen
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA.
| | - Chien-fei Lee
- Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yijuang Chern
- Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
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19
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Stoddart LA, Kellam B, Briddon SJ, Hill SJ. Effect of a toggle switch mutation in TM6 of the human adenosine A₃ receptor on Gi protein-dependent signalling and Gi-independent receptor internalization. Br J Pharmacol 2015; 171:3827-44. [PMID: 24750014 PMCID: PMC4128046 DOI: 10.1111/bph.12739] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 04/07/2014] [Accepted: 04/14/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE The highly conserved tryptophan (W6.48) in transmembrane domain 6 of GPCRs has been shown to play a central role in forming an active conformation in response to agonist binding. We set out to characterize the effect of this mutation on the efficacy of two agonists at multiple signalling pathways downstream of the adenosine A3 receptor. EXPERIMENTAL APPROACH Residue W6.48 in the human adenosine A3 receptor fused to yellow fluorescent protein was mutated to phenylalanine and expressed in CHO-K1 cells containing a cAMP response element reporter gene. The effects on agonist-mediated receptor internalization were monitored by automated confocal microscopy and image analysis. Further experiments were carried out to investigate agonist-mediated ERK1/2 phosphorylation, inhibition of [3H]-cAMP accumulation and β-arrestin2 binding. KEY RESULTS NECA was able to stimulate agonist-mediated internalization of the W6.48F mutant receptor, while the agonist HEMADO was inactive. Investigation of other downstream signalling pathways indicated that G-protein coupling was impaired for both agonists tested. Mutation of W6.48F therefore resulted in differential effects on agonist efficacy, and introduced signalling pathway bias for HEMADO at the adenosine A3 receptor. CONCLUSIONS AND IMPLICATIONS Investigation of the pharmacology of the W6.48F mutant of the adenosine A3 receptor confirms that this region is important in forming the active conformation of the receptor for stimulating a number of different signalling pathways and that mutations in this residue can lead to changes in agonist efficacy and signalling bias.
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Affiliation(s)
- Leigh A Stoddart
- Institute of Cell Signalling, School of Life Sciences, The University of Nottingham, Nottingham, UK
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20
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Gao ZG, Balasubramanian R, Kiselev E, Wei Q, Jacobson KA. Probing biased/partial agonism at the G protein-coupled A(2B) adenosine receptor. Biochem Pharmacol 2014; 90:297-306. [PMID: 24853985 PMCID: PMC4128710 DOI: 10.1016/j.bcp.2014.05.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 05/12/2014] [Accepted: 05/13/2014] [Indexed: 10/25/2022]
Abstract
G protein-coupled A(2B) adenosine receptor (AR) regulates numerous important physiological functions, but its activation by diverse A(2B)AR agonists is poorly profiled. We probed potential partial and/or biased agonism in cell lines expressing variable levels of endogenous or recombinant A(2B)AR. In cAMP accumulation assays, both 5'-substituted NECA and C2-substituted MRS3997 are full agonists. However, only 5'-substituted adenosine analogs are full agonists in calcium mobilization, ERK1/2 phosphorylation and β-arrestin translocation. A(2B)AR overexpression in HEK293 cells markedly increased the agonist potency and maximum effect in cAMP accumulation, but less in calcium and ERK1/2. A(2B)AR siRNA silencing was more effective in reducing the maximum cAMP effect of non-nucleoside agonist BAY60-6583 than NECA's. A quantitative 'operational model' characterized C2-substituted MRS3997 as either balanced (cAMP accumulation, ERK1/2) or strongly biased agonist (against calcium, β-arrestin). N⁶-substitution biased against ERK1/2 (weakly) and calcium and β-arrestin (strongly) pathways. BAY60-6583 is ERK1/2-biased, suggesting a mechanism distinct from adenosine derivatives. BAY60-6583, as A(2B)AR antagonist in MIN-6 mouse pancreatic β cells expressing low A(2B)AR levels, induced insulin release. This is the first relatively systematic study of structure-efficacy relationships of this emerging drug target.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Blg. 8A, Rm B1 A-17, NDDK 8 Center Dr., 9000 Rockville Pike, Bethesda, MD 20892-0810, USA.
| | - Ramachandran Balasubramanian
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Blg. 8A, Rm B1 A-17, NDDK 8 Center Dr., 9000 Rockville Pike, Bethesda, MD 20892-0810, USA
| | - Evgeny Kiselev
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Blg. 8A, Rm B1 A-17, NDDK 8 Center Dr., 9000 Rockville Pike, Bethesda, MD 20892-0810, USA
| | - Qiang Wei
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Blg. 8A, Rm B1 A-17, NDDK 8 Center Dr., 9000 Rockville Pike, Bethesda, MD 20892-0810, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Blg. 8A, Rm B1 A-17, NDDK 8 Center Dr., 9000 Rockville Pike, Bethesda, MD 20892-0810, USA.
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Allosteric modulation and functional selectivity of G protein-coupled receptors. DRUG DISCOVERY TODAY. TECHNOLOGIES 2014; 10:e237-43. [PMID: 24050274 DOI: 10.1016/j.ddtec.2012.08.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Agonists of a single G protein-coupled receptor (GPCR) may activate distinct signaling pathways. Functional selectivity, an emerging concept with therapeutic relevance for GPCRs, may be due to conformational selection or stabilization with respect to particular agonists, receptor dimerization, variable expression levels of GPCRs and downstream signaling molecules, and allosteric modulation. Allosteric modulators may have potential advantages over orthosteric ligands, including greater selectivity and safety. This review focuses on functional selectivity resulting from allosteric modulation.
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22
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Jacobson KA. Structure-based approaches to ligands for G-protein-coupled adenosine and P2Y receptors, from small molecules to nanoconjugates. J Med Chem 2013; 56:3749-67. [PMID: 23597047 PMCID: PMC3701956 DOI: 10.1021/jm400422s] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Adenosine receptor (ARs) and P2Y receptors (P2YRs) that respond to extracellular nucleosides/nucleotides are associated with new directions for therapeutics. The X-ray structures of the A2AAR complexes with agonists and antagonists are examined in relationship to the G-protein-coupled receptor (GPCR) superfamily and applied to drug discovery. Much of the data on AR ligand structure from early SAR studies now are explainable from the A2AAR X-ray crystallography. The ligand-receptor interactions in related GPCR complexes can be identified by means of modeling approaches, e.g., molecular docking. Thus, molecular recognition in binding and activation processes has been studied effectively using homology modeling and applied to ligand design. Virtual screening has yielded new nonnucleoside AR antagonists, and existing ligands have been improved with knowledge of the receptor interactions. New agonists are being explored for central nervous system and peripheral therapeutics based on in vivo activity, such as chronic neuropathic pain. Ligands for receptors more distantly related to the X-ray template, i.e., P2YRs, have been introduced and are mainly used as pharmacological tools for elucidating the physiological role of extracellular nucleotides. Other ligand tools for drug discovery include fluorescent probes, radioactive probes, multivalent probes, and functionalized nanoparticles.
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Affiliation(s)
- Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, USA.
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23
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Functional selectivity of adenosine A1 receptor ligands? Purinergic Signal 2012; 9:91-100. [PMID: 23054444 DOI: 10.1007/s11302-012-9334-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/10/2012] [Indexed: 02/06/2023] Open
Abstract
The concept of functional selectivity offers great potential for the development of drugs that selectively activate a specific intracellular signaling pathway. During the last few years, it has become possible to systematically analyse compound libraries on G protein-coupled receptors (GPCRs) for this 'biased' form of signaling. We screened over 800 compounds targeting the class of adenosine A(1) receptors using a β-arrestin-mediated signaling assay in U2OS cells as a G protein-independent readout for GPCR activation. A selection of compounds was further analysed in a G protein-mediated GTPγS assay. Additionally, receptor affinity of these compounds was determined in a radioligand binding assay with the agonist [(3)H]CCPA. Of all compounds tested, only LUF5589 9 might be considered as functionally selective for the G protein-dependent pathway, particularly in view of a likely overestimation of β-arrestin signaling in the U2OS cells. Altogether, our study shows that functionally selective ligands for the adenosine A(1) receptor are rare, if existing at all. A thorough analysis of biased signaling on other GPCRs also reveals that only very few compounds can be considered functionally selective. This might indicate that the concept of functional selectivity is less common than speculated.
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Denis C, Saulière A, Galandrin S, Sénard JM, Galés C. Probing heterotrimeric G protein activation: applications to biased ligands. Curr Pharm Des 2012; 18:128-44. [PMID: 22229559 DOI: 10.2174/138161212799040466] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 11/09/2011] [Indexed: 12/17/2022]
Abstract
Cell surface G protein-coupled receptors (GPCRs) drive numerous signaling pathways involved in the regulation of a broad range of physiologic processes. Today, they represent the largest target for modern drugs development with potential application in all clinical fields. Recently, the concept of "ligand-directed trafficking" has led to a conceptual revolution in pharmacological theory, thus opening new avenues for drug discovery. Accordingly, GPCRs do not function as simple on-off switch but rather as filters capable of selecting the activation of specific signals and thus generating texture responses to ligands, a phenomenon often referred to as ligand-biased signaling. Also, one challenging task today remains optimization of pharmacological assays with increased sensitivity so to better appreciate the inherent texture of ligands. However, considering that a single receptor has pleiotropic signaling properties and that each signal can crosstalk at different levels, biased activity remains thus difficult to evaluate. One strategy to overcome these limitations would be examining the initial steps following receptor activation. Even, if some G protein independent functions have been recently described, heterotrimeric G protein activation remains a general hallmark for all GPCRs families and the first cellular event subsequent to agonist binding to the receptor. Herein, we review the different methodologies classically used or recently developed to monitor G protein activation and discussed them in the context of G protein biased-ligands.
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Affiliation(s)
- Colette Denis
- Institut des Maladies Métaboliques et Cardiovasculaires, Université Toulouse III Paul Sabatier, Centre Hospitalier Universitaire de Toulouse, France.
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Bassoni DL, Raab WJ, Achacoso PL, Loh CY, Wehrman TS. Measurements of β-arrestin recruitment to activated seven transmembrane receptors using enzyme complementation. Methods Mol Biol 2012; 897:181-203. [PMID: 22674166 DOI: 10.1007/978-1-61779-909-9_9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The recruitment of arrestins to activated 7TMRs results in the activation of alternative signaling pathways, quenching of G-protein activation, and coupling to clathrin-mediated endocytosis. The nearly ubiquitous involvement of arrestin in 7TMR signaling has spurred the development of several methods for monitoring this interaction in mammalian cells. Nonetheless, few maintain the reproducibility and precision necessary for drug discovery applications. Enzyme fragment complementation technology (EFC) is an emerging protein-protein interaction technology based on the forced complementation of a split enzyme that has proven to be highly effective in monitoring the formation of GPCR-arrestin complexes. In these systems, the target proteins are fused to two fragments of an enzyme that show little or no spontaneous complementation. Interaction of the two proteins forces the complementation of the enzyme, resulting in an enzymatic measure of the protein interaction. This chapter discusses the utility and methods involved in using the PathHunter β-galactosidase complementation system to monitor arrestin recruitment and the advantages of exploiting this pathway in the characterization of 7TMR function.
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Fishman P, Bar-Yehuda S, Liang BT, Jacobson KA. Pharmacological and therapeutic effects of A3 adenosine receptor agonists. Drug Discov Today 2011; 17:359-66. [PMID: 22033198 DOI: 10.1016/j.drudis.2011.10.007] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/27/2011] [Accepted: 10/12/2011] [Indexed: 10/16/2022]
Abstract
The A(3) adenosine receptor (A(3)AR) coupled to G(i) (inhibitory regulative guanine nucleotide-binding protein) mediates anti-inflammatory, anticancer and anti-ischemic protective effects. The receptor is overexpressed in inflammatory and cancer cells, while low expression is found in normal cells, rendering the A(3)AR as a potential therapeutic target. Highly selective A(3)AR agonists have been synthesized and molecular recognition in the binding site has been characterized. In this article, we summarize preclinical and clinical human studies that demonstrate that A(3)AR agonists induce specific anti-inflammatory and anticancer effects through a molecular mechanism that entails modulation of the Wnt and the NF-κB signal transduction pathways. At present, A(3)AR agonists are being developed for the treatment of inflammatory diseases, including rheumatoid arthritis (RA) and psoriasis; ophthalmic diseases such as dry eye syndrome and glaucoma; liver diseases such as hepatocellular carcinoma and hepatitis.
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Affiliation(s)
- Pnina Fishman
- Can-Fite BioPharma Ltd, Kiryat-Matalon, 10 Bareket St, PO Box 7537, Petah-Tikva 49170, Israel
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May LT, Bridge LJ, Stoddart LA, Briddon SJ, Hill SJ. Allosteric interactions across native adenosine-A3 receptor homodimers: quantification using single-cell ligand-binding kinetics. FASEB J 2011; 25:3465-76. [PMID: 21715680 PMCID: PMC3177574 DOI: 10.1096/fj.11-186296] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A growing awareness indicates that many G-protein-coupled receptors (GPCRs) exist as homodimers, but the extent of the cooperativity across the dimer interface has been largely unexplored. Here, measurement of the dissociation kinetics of a fluorescent agonist (ABA-X-BY630) from the human A1 or A3 adenosine receptors expressed in CHO-K1 cells has provided evidence for highly cooperative interactions between protomers of the A3-receptor dimer in single living cells. In the absence of competitive ligands, the dissociation rate constants of ABA-X-BY630 from A1 and A3 receptors were 1.45 ± 0.05 and 0.57 ± 0.07 min−1, respectively. At the A3 receptor, this could be markedly increased by both orthosteric agonists and antagonists [15-, 9-, and 19-fold for xanthine amine congener (XAC), 5′-(N-ethyl carboxamido)adenosine (NECA), and adenosine, respectively] and reduced by coexpression of a nonbinding (N250A) A3-receptor mutant. The changes in ABA-X-BY630 dissociation were much lower at the A1 receptor (1.5-, 1.4-, and 1.5-fold). Analysis of the pEC50 values of XAC, NECA, and adenosine for the ABA-X-BY630-occupied A3-receptor dimer yielded values of 6.0 ± 0.1, 5.9 ± 0.1, and 5.2 ± 0.1, respectively. This study provides new insight into the spatial and temporal specificity of drug action that can be provided by allosteric modulation across a GPCR homodimeric interface.—May, L. T., Bridge, L. J., Stoddart, L. A., Briddon, S. J., Hill, S. J. Allosteric interactions across native adenosine-A3 receptor homodimers: quantification using single-cell ligand-binding kinetics.
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Affiliation(s)
- Lauren T May
- Institute of Cell Signalling, School of Biomedical Sciences, The University of Nottingham, Nottingham, UK, NG7 2UH
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Gao ZG, Verzijl D, Zweemer A, Ye K, Göblyös A, Ijzerman AP, Jacobson KA. Functionally biased modulation of A(3) adenosine receptor agonist efficacy and potency by imidazoquinolinamine allosteric enhancers. Biochem Pharmacol 2011; 82:658-68. [PMID: 21718691 DOI: 10.1016/j.bcp.2011.06.017] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/13/2011] [Accepted: 06/13/2011] [Indexed: 10/24/2022]
Abstract
Allosteric modulators for the G(i)-coupled A(3) adenosine receptor (AR) are of considerable interest as therapeutic agents and as pharmacological tools to probe various signaling pathways. In this study, we initially characterized the effects of several imidazoquinolinamine allosteric modulators (LUF5999, LUF6000 and LUF6001) on the human A(3) AR stably expressed in CHO cells using a cyclic AMP functional assay. These modulators were found to affect efficacy and potency of the agonist Cl-IB-MECA differently. LUF5999 (2-cyclobutyl derivative) enhanced efficacy but decreased potency. LUF6000 (2-cyclohexyl derivative) enhanced efficacy without affecting potency. LUF6001 (2-H derivative) decreased both efficacy and potency. We further compared the agonist enhancing effects of LUF6000 in several other A(3) AR-mediated events. It was shown that although LUF6000 behaved somewhat differently in various signaling pathways, it was more effective in enhancing the effects of low-efficacy than of high-efficacy agonists. In an assay of cyclic AMP accumulation, LUF6000 enhanced the efficacy of all agonists examined, but in the membrane hyperpolarization assay, it only enhanced the efficacy of partial agonists. In calcium mobilization, LUF6000 did not affect the efficacy of the full agonist NECA but was able to switch the nucleoside antagonist MRS542 into a partial agonist. In translocation of β-arrestin2, the agonist-enhancing effect LUF6000 was not pronounced. In an assay of ERK1/2 phosphorylation LUF6000 did not show any effect on the efficacy of Cl-IB-MECA. The differential effects of LUF6000 on the efficacy and potency of the agonist Cl-IB-MECA in various signaling pathway were interpreted quantitatively using a mathematical model.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA.
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Verzijl D, IJzerman AP. Functional selectivity of adenosine receptor ligands. Purinergic Signal 2011; 7:171-92. [PMID: 21544511 PMCID: PMC3146648 DOI: 10.1007/s11302-011-9232-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 04/05/2011] [Indexed: 12/11/2022] Open
Abstract
Adenosine receptors are plasma membrane proteins that transduce an extracellular signal into the interior of the cell. Basically every mammalian cell expresses at least one of the four adenosine receptor subtypes. Recent insight in signal transduction cascades teaches us that the current classification of receptor ligands into agonists, antagonists, and inverse agonists relies very much on the experimental setup that was used. Upon activation of the receptors by the ubiquitous endogenous ligand adenosine they engage classical G protein-mediated pathways, resulting in production of second messengers and activation of kinases. Besides this well-described G protein-mediated signaling pathway, adenosine receptors activate scaffold proteins such as β-arrestins. Using innovative and sensitive experimental tools, it has been possible to detect ligands that preferentially stimulate the β-arrestin pathway over the G protein-mediated signal transduction route, or vice versa. This phenomenon is referred to as functional selectivity or biased signaling and implies that an antagonist for one pathway may be a full agonist for the other signaling route. Functional selectivity makes it necessary to redefine the functional properties of currently used adenosine receptor ligands and opens possibilities for new and more selective ligands. This review focuses on the current knowledge of functionally selective adenosine receptor ligands and on G protein-independent signaling of adenosine receptors through scaffold proteins.
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Affiliation(s)
- Dennis Verzijl
- Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
| | - Ad P. IJzerman
- Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
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Whalen EJ, Rajagopal S, Lefkowitz RJ. Therapeutic potential of β-arrestin- and G protein-biased agonists. Trends Mol Med 2010; 17:126-39. [PMID: 21183406 DOI: 10.1016/j.molmed.2010.11.004] [Citation(s) in RCA: 413] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 11/13/2010] [Accepted: 11/17/2010] [Indexed: 12/21/2022]
Abstract
Members of the seven-transmembrane receptor (7TMR), or G protein-coupled receptor (GPCR), superfamily represent some of the most successful targets of modern drug therapy, with proven efficacy in the treatment of a broad range of human conditions and disease processes. It is now appreciated that β-arrestins, once viewed simply as negative regulators of traditional 7TMR-stimulated G protein signaling, act as multifunctional adapter proteins that regulate 7TMR desensitization and trafficking and promote distinct intracellular signals in their own right. Moreover, several 7TMR biased agonists, which selectively activate these divergent signaling pathways, have been identified. Here we highlight the diversity of G protein- and β-arrestin-mediated functions and the therapeutic potential of selective targeting of these in disease states.
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Affiliation(s)
- Erin J Whalen
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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Mundell S, Kelly E. Adenosine receptor desensitization and trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1319-28. [PMID: 20550943 DOI: 10.1016/j.bbamem.2010.06.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 05/28/2010] [Accepted: 06/06/2010] [Indexed: 11/26/2022]
Abstract
As with the majority of G-protein-coupled receptors, all four of the adenosine receptor subtypes are known to undergo agonist-induced regulation in the form of desensitization and trafficking. These processes can limit the ability of adenosine receptors to couple to intracellular signalling pathways and thus reduce the ability of adenosine receptor agonists as well as endogenous adenosine to produce cellular responses. In addition, since adenosine receptors couple to multiple signalling pathways, these pathways may desensitize differentially, while the desensitization of one pathway could even trigger signalling via another. Thus, the overall picture of adenosine receptor regulation can be complex. For all adenosine receptor subtypes, there is evidence to implicate arrestins in agonist-induced desensitization and trafficking, but there is also evidence for other possible forms of regulation, including second messenger-dependent kinase regulation, heterologous effects involving G proteins, and the involvement of non-clathrin trafficking pathways such as caveolae. In this review, the evidence implicating these mechanisms is summarized for each adenosine receptor subtype, and we also discuss those issues of adenosine receptor regulation that remain to be resolved as well as likely directions for future research in this field.
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Affiliation(s)
- Stuart Mundell
- Department of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Kenakin T, Miller LJ. Seven transmembrane receptors as shapeshifting proteins: the impact of allosteric modulation and functional selectivity on new drug discovery. Pharmacol Rev 2010; 62:265-304. [PMID: 20392808 DOI: 10.1124/pr.108.000992] [Citation(s) in RCA: 458] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
It is useful to consider seven transmembrane receptors (7TMRs) as disordered proteins able to allosterically respond to a number of binding partners. Considering 7TMRs as allosteric systems, affinity and efficacy can be thought of in terms of energy flow between a modulator, conduit (the receptor protein), and a number of guests. These guests can be other molecules, receptors, membrane-bound proteins, or signaling proteins in the cytosol. These vectorial flows of energy can yield standard canonical guest allostery (allosteric modification of drug effect), effects along the plane of the cell membrane (receptor oligomerization), or effects directed into the cytosol (differential signaling as functional selectivity). This review discusses these apparently diverse pharmacological effects in terms of molecular dynamics and protein ensemble theory, which tends to unify 7TMR behavior toward cells. Special consideration will be given to functional selectivity (biased agonism and biased antagonism) in terms of mechanism of action and potential therapeutic application. The explosion of technology that has enabled observation of diverse 7TMR behavior has also shown how drugs can have multiple (pluridimensional) efficacies and how this can cause paradoxical drug classification and nomenclatures.
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Affiliation(s)
- Terry Kenakin
- GlaxoSmithKline, 5 Moore Drive, Mailtstop V-287, Research Triangle Park, NC 27709, USA.
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Leduc M, Breton B, Galés C, Le Gouill C, Bouvier M, Chemtob S, Heveker N. Functional selectivity of natural and synthetic prostaglandin EP4 receptor ligands. J Pharmacol Exp Ther 2009; 331:297-307. [PMID: 19584306 DOI: 10.1124/jpet.109.156398] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Classically, the prostaglandin E(2) (PGE(2)) receptor EP(4) has been classified as coupling to the Galpha(s) subunit, leading to intracellular cAMP increases. However, EP(4) signaling has been revealed to be more complex and also involves coupling to pertussis toxin-sensitive Galpha(i) proteins and beta-arrestin-mediated effects. There are now many examples of selective activation of independent pathways by G protein-coupled receptor (GPCR) ligands, a concept referred to as functional selectivity. Because most EP(4) ligands had thus far only been functionally characterized by their ability to stimulate cAMP production, we systematically determined the potencies and efficacies of a panel of EP(4) ligands for activation of Galpha(s), Galpha(i), and beta-arrestin relative to the endogenous ligand PGE(2). For this purpose, we adapted three bioluminescence resonance energy transfer (BRET) assays to evaluate the respective pathways in living cells. Our results suggest considerable functional selectivity among the tested, structurally related agonists. PGE(2) was the most selective in activating Galpha(s), whereas PGF(2alpha) and PGE(1) alcohol were the most biased for activating Galpha(i1) and beta-arrestin, respectively. We observed reversal in order of potencies between beta-arrestin 2 and Galpha(i1) functional assays comparing PGE(1) alcohol and either PGF(2alpha), PGD(2), or 7-[(1R,2R)-2-[(E,3R)-3-hydroxy-4-(phenoxy)but-1-enyl]-5-oxocyclopentyl]heptanoic acid (M&B28767). Most ligands were full agonists for the three pathways tested. Our results have implications for the use of PGE(2) analogs in experimental and possibly clinical settings, because their activity spectra on EP(4) differ from that of the native agonist. The BRET-based methodology used for this first systematic assessment of a set of EP(4) agonists should be applicable for the study of other GPCRs.
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Affiliation(s)
- Martin Leduc
- Department of Biochemistry, Université de Montréal, Québec, Canada
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Kim Y, de Castro S, Gao ZG, Ijzerman AP, Jacobson KA. Novel 2- and 4-substituted 1H-imidazo[4,5-c]quinolin-4-amine derivatives as allosteric modulators of the A3 adenosine receptor. J Med Chem 2009; 52:2098-108. [PMID: 19284749 PMCID: PMC2765805 DOI: 10.1021/jm801659w] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
4-Arylamino and 2- cycloalkyl (including amino substitution) modifications were made in a series of 1H-imidazo[4,5-c]quinolin-4-amine derivatives as allosteric modulators of the human A(3) adenosine receptor (AR). In addition to allosteric modulation of the maximum functional efficacy (in [(35)S]GTPgammaS G protein binding assay) of the A(3)AR agonist Cl-IB-MECA (15), some analogues also weakly inhibited equilibrium radioligand binding at ARs. 4-(3,5-Dichlorophenylamino) (6) or 2-(1-adamantyl) (20) substitution produced allosteric enhancement (twice the maximal agonist efficacy), with minimal inhibition of orthosteric AR binding. 2-(4-Tetrahydropyranyl) substitution abolished allosteric enhancement but preserved inhibition of orthosteric binding. Introduction of nitrogen in the six-membered ring at the 2 position, to improve aqueous solubility and provide a derivatization site, greatly reduced the allosteric enhancement. 2-(4-(Benzoylamino)cyclohexyl) analogues 23 and 24 were weak negative A(3)AR modulators. Thus, consistent with previous findings, the allosteric and orthosteric inhibitory A(3)AR effects in imidazoquinolines are structurally separable, suggesting the possible design of additional derivatives with enhanced positive or negative allosteric A(3)AR activity and improved selectivity in comparison to inhibition of orthosteric binding.
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Affiliation(s)
- Yoonkyung Kim
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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