1
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Rinne MK, Urvas L, Mandrika I, Fridmanis D, Riddy DM, Langmead CJ, Kukkonen JP, Xhaard H. Characterization of a putative orexin receptor in Ciona intestinalis sheds light on the evolution of the orexin/hypocretin system in chordates. Sci Rep 2024; 14:7690. [PMID: 38565870 PMCID: PMC10987541 DOI: 10.1038/s41598-024-56508-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 03/07/2024] [Indexed: 04/04/2024] Open
Abstract
Tunicates are evolutionary model organisms bridging the gap between vertebrates and invertebrates. A genomic sequence in Ciona intestinalis (CiOX) shows high similarity to vertebrate orexin receptors and protostome allatotropin receptors (ATR). Here, molecular phylogeny suggested that CiOX is divergent from ATRs and human orexin receptors (hOX1/2). However, CiOX appears closer to hOX1/2 than to ATR both in terms of sequence percent identity and in its modelled binding cavity, as suggested by molecular modelling. CiOX was heterologously expressed in a recombinant HEK293 cell system. Human orexins weakly but concentration-dependently activated its Gq signalling (Ca2+ elevation), and the responses were inhibited by the non-selective orexin receptor antagonists TCS 1102 and almorexant, but only weakly by the OX1-selective antagonist SB-334867. Furthermore, the 5-/6-carboxytetramethylrhodamine (TAMRA)-labelled human orexin-A was able to bind to CiOX. Database mining was used to predict a potential endogenous C. intestinalis orexin peptide (Ci-orexin-A). Ci-orexin-A was able to displace TAMRA-orexin-A, but not to induce any calcium response at the CiOX. Consequently, we suggested that the orexin signalling system is conserved in Ciona intestinalis, although the relevant peptide-receptor interaction was not fully elucidated.
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Affiliation(s)
- Maiju K Rinne
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, POB 56, 00014, Helsinki, Finland
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, POB 66, 00014, Helsinki, Finland
- Department of Pharmacology, Medicum, University of Helsinki, POB 63, 00014, Helsinki, Finland
| | - Lauri Urvas
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, POB 56, 00014, Helsinki, Finland
- Laboratoire d'Innovation Thérapeutique, Faculté de Pharmacie, Université de Strasbourg, Illkirch-Graffenstaden, France
| | - Ilona Mandrika
- Latvian Biomedical Research and Study Centre, Riga, Latvia
| | | | - Darren M Riddy
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Christopher J Langmead
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, POB 66, 00014, Helsinki, Finland.
- Department of Pharmacology, Medicum, University of Helsinki, POB 63, 00014, Helsinki, Finland.
| | - Henri Xhaard
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, POB 56, 00014, Helsinki, Finland.
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Melén K, Jalkanen P, Kukkonen JP, Partinen M, Nohynek H, Vuorela A, Vaarala O, Freitag TL, Meri S, Julkunen I. No evidence of autoimmunity to human OX 1 or OX 2 orexin receptors in Pandemrix-vaccinated narcoleptic children. J Transl Autoimmun 2020; 3:100055. [PMID: 32743535 PMCID: PMC7388359 DOI: 10.1016/j.jtauto.2020.100055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 04/15/2020] [Accepted: 04/23/2020] [Indexed: 12/12/2022] Open
Abstract
Narcolepsy type 1, likely an immune-mediated disease, is characterized by excessive daytime sleepiness and cataplexy. The disease is strongly associated with human leukocyte antigen (HLA) DQB1∗06:02. A significant increase in the incidence of childhood and adolescent narcolepsy was observed after a vaccination campaign with AS03-adjuvanted Pandemrix influenza vaccine in Nordic and several other countries in 2010 and 2011. Previously, it has been suggested that a surface-exposed region of influenza A nucleoprotein, a structural component of the Pandemrix vaccine, shares amino acid residues with the first extracellular domain of the human OX2 orexin/hypocretin receptor eliciting the development of autoantibodies. Here, we analyzed, whether H1N1pdm09 infection or Pandemrix vaccination contributed to the development of autoantibodies to the orexin precursor protein or the OX1 or OX2 receptors. The analysis was based on the presence or absence of autoantibody responses against analyzed proteins. Entire OX1 and OX2 receptors or just their extracellular N-termini were transiently expressed in HuH7 cells to determine specific antibody responses in human sera. Based on our immunofluorescence analysis, none of the 56 Pandemrix-vaccinated narcoleptic patients, 28 patients who suffered from a laboratory-confirmed H1N1pdm09 infection or 19 Pandemrix-vaccinated controls showed specific autoantibody responses to prepro-orexin, orexin receptors or the isolated extracellular N-termini of orexin receptors. We also did not find any evidence for cell-mediated immunity against the N-terminal epitopes of OX2. Our findings do not support the hypothesis that the surface-exposed region of the influenza nucleoprotein A would elicit the development of an immune response against orexin receptors. No evidence of humoral immunity against human OX1 or OX2 orexin receptors. No cross-reactive antibodies between influenza virus NP and orexin receptors. No evidence for cell-mediated immunity against the N-terminal epitopes of OX2.
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Affiliation(s)
- Krister Melén
- Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.,Expert Microbiology Unit, Finnish Institute for Health and Welfare, Mannerheimintie 166, 00300, Helsinki, Finland
| | - Pinja Jalkanen
- Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Jyrki P Kukkonen
- Department of Physiology and Department of Pharmacology, Institute of Biomedicine, Faculty of Medicine and Biochemistry and Cell Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Markku Partinen
- Helsinki Sleep Clinic, Vitalmed Research Centre Helsinki and Medicum, Faculty of Medicine, University of Helsinki, Finland
| | - Hanna Nohynek
- Infectious Disease Control and Vaccination Unit, Finnish Institute for Health and Welfare, Helsinki, Finland
| | - Arja Vuorela
- Reseach Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki
| | - Outi Vaarala
- Reseach Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki
| | - Tobias L Freitag
- Department of Bacteriology and Immunology and Translational Immunology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Seppo Meri
- Department of Bacteriology and Immunology and Translational Immunology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Ilkka Julkunen
- Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.,Turku University Hospital, Clinical Microbiology, Kiinamyllynkatu 10, 20520, Turku, Finland
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3
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Targeting the orexinergic system: Mainly but not only for sleep-wakefulness therapies. ALEXANDRIA JOURNAL OF MEDICINE 2019. [DOI: 10.1016/j.ajme.2014.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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4
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Turku A, Leino TO, Karhu L, Yli-Kauhaluoma J, Kukkonen JP, Wallén EAA, Xhaard H. Structure-Activity Relationships of 1-Benzoylazulenes at the OX 1 and OX 2 Orexin Receptors. ChemMedChem 2019; 14:965-981. [PMID: 30892823 DOI: 10.1002/cmdc.201900074] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 03/20/2019] [Indexed: 11/08/2022]
Abstract
We previously demonstrated the potential of di- or trisubstituted azulenes as ligands (potentiators, weak agonists, and antagonists) of the orexin receptors. In this study we investigated 27 1-benzoylazulene derivatives, uncovering seven potentiators of the orexin response on OX1 and two weak dual orexin receptor agonists. For potentiators, replacement of the azulene scaffold by indole retained the activity of four out of six compounds. The structure-activity relationships for agonism and potentiation can be summarized into a bicyclic aromatic ring system substituted with two hydrogen-bond acceptors (1-position, benzoyl; 6-position, carboxyl/ester) within 7-8 Å of each other; a third acceptor at the 3-position is also well tolerated. The same pharmacophoric signature is found in the preferred conformations of the orexin receptor agonist Nag26 from molecular dynamics simulations. Subtle changes switch the activity between weak agonism and potentiation, suggesting overlapping binding sites.
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Affiliation(s)
- Ainoleena Turku
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland.,Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland
| | - Teppo O Leino
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Lasse Karhu
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Jari Yli-Kauhaluoma
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Jyrki P Kukkonen
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland.,Department of Physiology, Faculty of Medicine, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Erik A A Wallén
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Henri Xhaard
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
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Turku A, Borrel A, Leino TO, Karhu L, Kukkonen JP, Xhaard H. Pharmacophore Model To Discover OX1 and OX2 Orexin Receptor Ligands. J Med Chem 2016; 59:8263-75. [DOI: 10.1021/acs.jmedchem.6b00333] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Ainoleena Turku
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
- Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, P.O. Box 66, FIN-00014 Helsinki, Finland
| | - Alexandre Borrel
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Teppo O. Leino
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Lasse Karhu
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Jyrki P. Kukkonen
- Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, P.O. Box 66, FIN-00014 Helsinki, Finland
| | - Henri Xhaard
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
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Imperatore R, Palomba L, Morello G, Spiezio AD, Piscitelli F, Marzo VD, Cristino L. Formation of OX-1R/CB 1 R heteromeric complexes in embryonic mouse hypothalamic cells: Effect on intracellular calcium, 2-arachidonoyl-glycerol biosynthesis and ERK phosphorylation. Pharmacol Res 2016; 111:600-609. [DOI: 10.1016/j.phrs.2016.07.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/27/2016] [Accepted: 07/06/2016] [Indexed: 12/16/2022]
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OX2 orexin/hypocretin receptor signal transduction in recombinant Chinese hamster ovary cells. Cell Signal 2015; 28:51-60. [PMID: 26582739 DOI: 10.1016/j.cellsig.2015.11.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/30/2015] [Accepted: 11/10/2015] [Indexed: 01/06/2023]
Abstract
There are two subtypes of orexin receptors, OX1 and OX2. Signalling pathways have been mapped in much higher detail for OX1 receptors than OX2 receptors. Almost all the detailed studies have been performed in Chinese hamster ovary cells, and we thus chose the same cell background for the studies on human OX2 receptors to allow comparison to human OX1 receptors. Adenylyl cyclase, phospholipase A2, C and D and diacylglycerol lipase activities were assessed by precursor radiolabelling and chromatographic separation (ion exchange, affinity or thin layer), calcium by a fluorescent method, and receptor binding with [(125)I]-orexin-A. Upon activation with orexin-A, OX2 receptors stimulated phospholipase A2, C and D, diacylglycerol lipase and calcium elevation, and both inhibited and stimulated adenylyl cyclase; i.e., the responses to OX2 activation by orexin-A were principally like those of OX1, in contrast to some previous suggestions. The responses occurred mostly in the same concentration range as those for OX1 activation and via the same signal cascades. However, some responses were weaker, suggesting a partially differential coupling to some cascades. In summary, OX2 receptor signalling is principally similar to OX1 receptor signalling suggesting also a physiologically similar coupling, though this needs to be verified in physiological contexts. Some (relatively weak) differences between the receptors may be investigated in further studies.
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Putula J, Pihlajamaa T, Kukkonen JP. Calcium affects OX1 orexin (hypocretin) receptor responses by modifying both orexin binding and the signal transduction machinery. Br J Pharmacol 2014; 171:5816-28. [PMID: 25132134 DOI: 10.1111/bph.12883] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 08/05/2014] [Accepted: 08/12/2014] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE One of the major responses upon orexin receptor activation is Ca(2+) influx, and this influx seems to amplify the other responses mediated by orexin receptors. However, the reduction in Ca(2+) , often used to assess the importance of Ca(2+) influx, might affect other properties, like ligand-receptor interactions, as suggested for some GPCR systems. Hence, we investigated the role of the ligand-receptor interaction and Ca(2+) signal cascades in the apparent Ca(2+) requirement of orexin-A signalling. EXPERIMENTAL APPROACH Receptor binding was assessed in CHO cells expressing human OX1 receptors with [(125) I]-orexin-A by conventional ligand binding as well as scintillation proximity assays. PLC activity was determined by chromatography. KEY RESULTS Both orexin receptor binding and PLC activation were strongly dependent on the extracellular Ca(2+) concentration. The relationship between Ca(2+) concentration and receptor binding was the same as that for PLC activation. However, when Ca(2+) entry was reduced by depolarizing the cells or by inhibiting the receptor-operated Ca(2+) channels, orexin-A-stimulated PLC activity was much more strongly inhibited than orexin-A binding. CONCLUSIONS AND IMPLICATIONS Ca(2+) plays a dual role in orexin signalling by being a prerequisite for both ligand-receptor interaction and amplifying orexin signals via Ca(2+) influx. Some previous results obtained utilizing Ca(2+) chelators have to be re-evaluated based on the results of the current study. From a drug discovery perspective, further experiments need to identify the target for Ca(2+) in orexin-A-OX1 receptor interaction and its mechanism of action.
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Affiliation(s)
- Jaana Putula
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
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9
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Abstract
Addiction is a chronic relapsing disorder which presents a significant global health burden and unmet medical need. The orexin/hypocretin system is an attractive potential therapeutic target as demonstrated by the successful clinical trials of antagonist medications like Suvorexant for insomnia. It is composed of two neuropeptides, orexin-A and orexin-B and two excitatory and promiscuous G-protein coupled receptors, OX1 and OX2. Orexins are known to have a variety of functions, most notably in regulating arousal, appetite and reward. The orexins have been shown to have a role in mediating the effects of several drugs of abuse, such as cocaine, morphine and alcohol via projections to key brain regions such as the ventral tegmental area, nucleus accumbens and prefrontal cortex. However, it has not yet been demonstrated whether the dual orexin receptor antagonists (DORAs) under development for insomnia are ideal drugs for the treatment of addiction. The question of whether to use a DORA or single orexin receptor antagonist (SORA) for the treatment of addiction is a key question that will need to be answered in order to maximize the clinical utility of orexin receptor antagonists. This review will examine the role of the orexin/hypocretin system in addiction, orexin-based pharmacotherapies under development and factors affecting the selection of one or both orexin receptors as drug targets for the treatment of addiction.
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10
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Thompson MD, Xhaard H, Sakurai T, Rainero I, Kukkonen JP. OX1 and OX2 orexin/hypocretin receptor pharmacogenetics. Front Neurosci 2014; 8:57. [PMID: 24834023 PMCID: PMC4018553 DOI: 10.3389/fnins.2014.00057] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Accepted: 03/12/2014] [Indexed: 01/01/2023] Open
Abstract
Orexin/hypocretin peptide mutations are rare in humans. Even though human narcolepsy is associated with orexin deficiency, this is only extremely rarely due to mutations in the gene coding prepro-orexin, the precursor for both orexin peptides. In contrast, coding and non-coding variants of the OX1 and OX2 orexin receptors have been identified in many human populations; sometimes, these have been associated with disease phenotype, although most confer a relatively low risk. In most cases, these studies have been based on a candidate gene hypothesis that predicts the involvement of orexins in the relevant pathophysiological processes. In the current review, the known human OX1/HCRTR1 and OX2/HCRTR2 genetic variants/polymorphisms as well as studies concerning their involvement in disorders such as narcolepsy, excessive daytime sleepiness, cluster headache, polydipsia-hyponatremia in schizophrenia, and affective disorders are discussed. In most cases, the functional cellular or pharmacological correlates of orexin variants have not been investigated—with the exception of the possible impact of an amino acid 10 Pro/Ser variant of OX2 on orexin potency—leaving conclusions on the nature of the receptor variant effects speculative. Nevertheless, we present perspectives that could shape the basis for further studies. The pharmacology and other properties of the orexin receptor variants are discussed in the context of GPCR signaling. Since orexinergic therapeutics are emerging, the impact of receptor variants on the affinity or potency of ligands deserves consideration. This perspective (pharmacogenetics) is also discussed in the review.
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Affiliation(s)
- Miles D Thompson
- University of Toronto Epilepsy Research Program, Department of Pharmacology, University of Toronto Toronto, ON, Canada
| | - Henri Xhaard
- Faculty of Pharmacy, Centre for Drug Research, University of Helsinki Helsinki, Finland
| | - Takeshi Sakurai
- Department of Molecular Neuroscience and Integrative Physiology, Faculty of Medicine, Kanazawa University Kanazawa, Japan
| | | | - Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki Helsinki, Finland
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11
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Jäntti MH, Mandrika I, Kukkonen JP. Human orexin/hypocretin receptors form constitutive homo- and heteromeric complexes with each other and with human CB1 cannabinoid receptors. Biochem Biophys Res Commun 2014; 445:486-90. [PMID: 24530395 DOI: 10.1016/j.bbrc.2014.02.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 02/06/2014] [Indexed: 12/17/2022]
Abstract
Human OX1 orexin receptors have been shown to homodimerize and they have also been suggested to heterodimerize with CB1 cannabinoid receptors. The latter has been suggested to be important for orexin receptor responses and trafficking. In this study, we wanted to assess the ability of the other combinations of receptors to also form similar complexes. Vectors for expression of human OX1, OX2 and CB1 receptors, C-terminally fused with either Renilla luciferase or GFP(2) green fluorescent protein variant, were generated. The constructs were transiently expressed in Chinese hamster ovary cells, and constitutive dimerization between the receptors was assessed by bioluminescence energy transfer (BRET). Orexin receptor subtypes readily formed homo- and hetero(di)mers, as suggested by significant BRET signals. CB1 receptors formed homodimers, and they also heterodimerized with both orexin receptors. Interestingly, BRET efficiency was higher for homodimers than for almost all heterodimers. This is likely to be due to the geometry of the interaction; the putatively symmetric dimers may place the C-termini in a more suitable orientation in homomers. Fusion of luciferase to an orexin receptor and GFP(2) to CB1 produced more effective BRET than the opposite fusions, also suggesting differences in geometry. Similar was seen for the OX1-OX2 interaction. In conclusion, orexin receptors have a significant propensity to make homo- and heterodi-/oligomeric complexes. However, it is unclear whether this affects their signaling. As orexin receptors efficiently signal via endocannabinoid production to CB1 receptors, dimerization could be an effective way of forming signal complexes with optimal cannabinoid concentrations available for cannabinoid receptors.
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Affiliation(s)
- Maria H Jäntti
- Department of Veterinary Biosciences, POB 66, FIN-00014 University of Helsinki, Finland.
| | - Ilona Mandrika
- Latvian Biomedical Research and Study Centre, Ratsupites Str. 1, Riga LV 1067, Latvia.
| | - Jyrki P Kukkonen
- Department of Veterinary Biosciences, POB 66, FIN-00014 University of Helsinki, Finland.
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12
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German NA, Decker AM, Gilmour BP, Thomas BF, Zhang Y. Truncated Orexin Peptides: Structure-Activity Relationship Studies. ACS Med Chem Lett 2013; 4:1224-1227. [PMID: 24707347 DOI: 10.1021/ml400333a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Orexin receptors are involved in many processes including energy homeostasis, wake/sleep cycle, metabolism and reward. Development of potent and selective ligands is an essential step for defining the mechanism(s) underlying such critical processes. The goal of this study was to further investigate the structure-activity relationships of these peptides and to identify truncated form of the orexin peptides active at OX1. Truncation studies have led to OXA (17-33) as the shortest active peptide known to date with a 23-fold selectivity for OX1 over OX2. Alanine, D-amino acid and proline scans have highlighted the particular importance of Tyr17, Leu20, Asn25 and His26 for agonist properties of OXA(17-33). The conformation of the C-terminus might also be a defining factor in agonist activity and selectivity of the orexin peptides for the OX1 receptor.
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Affiliation(s)
- Nadezhda A. German
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Ann M. Decker
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Brian P. Gilmour
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Brian F. Thomas
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
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13
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Kukkonen JP. Physiology of the orexinergic/hypocretinergic system: a revisit in 2012. Am J Physiol Cell Physiol 2012; 304:C2-32. [PMID: 23034387 DOI: 10.1152/ajpcell.00227.2012] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The neuropeptides orexins and their G protein-coupled receptors, OX(1) and OX(2), were discovered in 1998, and since then, their role has been investigated in many functions mediated by the central nervous system, including sleep and wakefulness, appetite/metabolism, stress response, reward/addiction, and analgesia. Orexins also have peripheral actions of less clear physiological significance still. Cellular responses to the orexin receptor activity are highly diverse. The receptors couple to at least three families of heterotrimeric G proteins and other proteins that ultimately regulate entities such as phospholipases and kinases, which impact on neuronal excitation, synaptic plasticity, and cell death. This article is a 10-year update of my previous review on the physiology of the orexinergic/hypocretinergic system. I seek to provide a comprehensive update of orexin physiology that spans from the molecular players in orexin receptor signaling to the systemic responses yet emphasizing the cellular physiological aspects of this system.
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Affiliation(s)
- Jyrki P Kukkonen
- Dept. of Veterinary Biosciences, University of Helsinki, Finland.
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14
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Gotter AL, Webber AL, Coleman PJ, Renger JJ, Winrow CJ. International Union of Basic and Clinical Pharmacology. LXXXVI. Orexin Receptor Function, Nomenclature and Pharmacology. Pharmacol Rev 2012; 64:389-420. [DOI: 10.1124/pr.111.005546] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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15
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Putula J, Kukkonen JP. Mapping of the binding sites for the OX1 orexin receptor antagonist, SB-334867, using orexin/hypocretin receptor chimaeras. Neurosci Lett 2012; 506:111-5. [DOI: 10.1016/j.neulet.2011.10.061] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 10/04/2011] [Accepted: 10/25/2011] [Indexed: 01/04/2023]
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