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Holtschulte C, Börgel F, Westphälinger S, Schepmann D, Civenni G, Laurini E, Marson D, Catapano CV, Pricl S, Wünsch B. Synthesis of aminoethyl substituted piperidine derivatives as σ1 receptor ligands with antiproliferative properties. ChemMedChem 2022; 17:e202100735. [PMID: 35077612 PMCID: PMC9303367 DOI: 10.1002/cmdc.202100735] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/17/2022] [Indexed: 12/05/2022]
Abstract
A series of novel σ1 receptor ligands with a 4‐(2‐aminoethyl)piperidine scaffold was prepared and biologically evaluated. The underlying concept of our project was the improvement of the lipophilic ligand efficiency of previously synthesized potent σ1 ligands. The key steps of the synthesis comprise the conjugate addition of phenylboronic acid at dihydropyridin‐4(1H)‐ones 7, homologation of the ketones 8 and introduction of diverse amino moieties and piperidine N‐substituents. 1‐Methylpiperidines showed particular high σ1 receptor affinity and selectivity over the σ2 subtype, whilst piperidines with a proton, a tosyl moiety or an ethyl moiety exhibited considerably lower σ1 affinity. Molecular dynamics simulations with per‐residue binding free energy deconvolution demonstrated that different interactions of the basic piperidine‐N‐atom and its substituents (or the cyclohexane ring) with the lipophilic binding pocket consisting of Leu105, Thr181, Leu182, Ala185, Leu186, Thr202 and Tyr206 are responsible for the different σ1 receptor affinities. Recorded logD7.4 and calculated clogP values of 4a and 18a indicate low lipophilicity and thus high lipophilic ligand efficiency. Piperidine 4a inhibited the growth of human non‐small cell lung cancer cells A427 to a similar extent as the σ1 antagonist haloperidol. 1‐Methylpiperidines 20a, 21a and 22a showed stronger antiproliferative effects on androgen negative human prostate cancer cells DU145 than the σ1 ligands NE100 and S1RA.
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Affiliation(s)
- Catharina Holtschulte
- Institut für Pharmazeutische und Medizinische ChemieWestfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
| | - Frederik Börgel
- Institut für Pharmazeutische und Medizinische ChemieWestfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
| | - Stefanie Westphälinger
- Institut für Pharmazeutische und Medizinische ChemieWestfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
| | - Dirk Schepmann
- Institut für Pharmazeutische und Medizinische ChemieWestfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
| | - Gianluca Civenni
- Institute of Oncology ResearchUniversità della Svizzera Italiana (USI)Via Vincenzo Vela 66500BellinzonaSwitzerland
| | - Erik Laurini
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTS), DEAUniversity of Trieste34127TriesteItaly
| | - Domenico Marson
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTS), DEAUniversity of Trieste34127TriesteItaly
| | - Carlo V. Catapano
- Institute of Oncology ResearchUniversità della Svizzera Italiana (USI)Via Vincenzo Vela 66500BellinzonaSwitzerland
| | - Sabrina Pricl
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTS), DEAUniversity of Trieste34127TriesteItaly
- Department of General BiophysicsFaculty of Biology and Environmental ProtectionUniversity of Lodz90-237LodzPoland
| | - Bernhard Wünsch
- Institut für Pharmazeutische und Medizinische ChemieWestfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
- Chemical biology of ion channels (Chembion)Westfälische Wilhelms-Universität MünsterCorrensstraße 4848149MünsterGermany
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2
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Oyer HM, Sanders CM, Kim FJ. Small-Molecule Modulators of Sigma1 and Sigma2/TMEM97 in the Context of Cancer: Foundational Concepts and Emerging Themes. Front Pharmacol 2019; 10:1141. [PMID: 31695608 PMCID: PMC6816035 DOI: 10.3389/fphar.2019.01141] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/04/2019] [Indexed: 12/17/2022] Open
Abstract
There are two known subtypes of the so-called sigma receptors, Sigma1 and Sigma2. Sigma1 (encoded by the SIGMAR1 gene and also known as Sigma-1 receptor, S1R) is a unique pharmacologically regulated integral membrane chaperone or scaffolding protein that allosterically modulates the activity of its associated proteins. Sigma2, recently identified as transmembrane protein 97 (TMEM97), is an integral membrane protein implicated in cellular cholesterol homeostasis. A number of publications over the past two decades have suggested a role for both sigma proteins in tumor biology. Although there is currently no clinically used anti-cancer drug that targets Sigma1 or Sigma2/TMEM97, a growing body of evidence supports the potential of small-molecule compounds with affinity for these proteins, putative sigma ligands, as therapeutic agents to treat cancer. In preclinical models, these compounds have been reported to inhibit cancer cell proliferation, survival, adhesion, and migration; furthermore, they have been demonstrated to suppress tumor growth, to alleviate cancer-associated pain, and to exert immunomodulatory properties. Here, we will address the known knowns and the known unknowns of Sigma1 and Sigma2/TMEM97 ligand actions in the context of cancer. This review will highlight key discoveries and published evidence in support of a role for sigma proteins in cancer and will discuss several fundamental questions regarding the physiological roles of sigma proteins in cancer and sigma ligand mechanism of action.
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Affiliation(s)
- Halley M Oyer
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
| | - Christina M Sanders
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
| | - Felix J Kim
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
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Kronenberg E, Weber F, Brune S, Schepmann D, Almansa C, Friedland K, Laurini E, Pricl S, Wünsch B. Synthesis and Structure-Affinity Relationships of Spirocyclic Benzopyrans with Exocyclic Amino Moiety. J Med Chem 2019; 62:4204-4217. [PMID: 30939014 DOI: 10.1021/acs.jmedchem.9b00449] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
σ1 and/or σ2 receptors play a crucial role in pathological conditions such as pain, neurodegenerative disorders, and cancer. A set of spirocyclic cyclohexanes with diverse O-heterocycles and amino moieties (general structure III) was prepared and pharmacologically evaluated. In structure-activity relationships studies, the σ1 receptor affinity and σ1:σ2 selectivity were correlated with the stereochemistry, the kind and substitution pattern of the O-heterocycle, and the substituents at the exocyclic amino moiety. cis-configured 2-benzopyran cis-11b bearing a methoxy group and a tertiary cyclohexylmethylamino moiety showed the highest σ1 affinity ( Ki = 1.9 nM) of this series of compounds. In a Ca2+ influx assay, cis-11b behaved as a σ1 antagonist. cis-11b reveals high selectivity over σ2 and opioid receptors. The interactions of the novel σ1 ligands were analyzed on the molecular level using the recently reported X-ray crystal structure of the σ1 receptor protein. The protonated amino moiety forms a persistent salt bridge with E172. The spiro[benzopyran-1,1'-cyclohexane] scaffold and the cyclohexylmethyl moiety occupy two hydrophobic pockets. Exchange of the N-cyclohexylmethyl moiety by a benzyl group led unexpectedly to potent and selective μ-opioid receptor ligands.
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Affiliation(s)
- Elisabeth Kronenberg
- Institut für Pharmazeutische und Medizinische Chemie der Universität Münster , Corrensstraße 48 , D-48149 Münster , Germany
| | - Frauke Weber
- Institut für Pharmazeutische und Medizinische Chemie der Universität Münster , Corrensstraße 48 , D-48149 Münster , Germany
| | - Stefanie Brune
- Institut für Pharmazeutische und Medizinische Chemie der Universität Münster , Corrensstraße 48 , D-48149 Münster , Germany
| | - Dirk Schepmann
- Institut für Pharmazeutische und Medizinische Chemie der Universität Münster , Corrensstraße 48 , D-48149 Münster , Germany
| | - Carmen Almansa
- Esteve Pharmaceuticals S.A. , Baldiri Reixach 4-8 , 08028 Barcelona , Spain
| | - Kristina Friedland
- Pharmakologie und Toxikologie, Institut für Pharmazie und Biochemie , Universität Mainz , Staudinger Weg 5 , D-55128 Mainz , Germany
| | - Erik Laurini
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTS), DEA , University of Trieste , 34127 Trieste , Italy
| | - Sabrina Pricl
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTS), DEA , University of Trieste , 34127 Trieste , Italy
| | - Bernhard Wünsch
- Institut für Pharmazeutische und Medizinische Chemie der Universität Münster , Corrensstraße 48 , D-48149 Münster , Germany
- Cells-in-motion Cluster of Excellence (EXC 1003-CiM) , University of Münster , D-48149 Münster , Germany
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4
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Abstract
Sigma1 (also known as sigma-1 receptor, Sig1R, σ1 receptor) is a unique pharmacologically regulated integral membrane chaperone or scaffolding protein. The majority of publications on the subject have focused on the neuropharmacology of Sigma1. However, a number of publications have also suggested a role for Sigma1 in cancer. Although there is currently no clinically used anti-cancer drug that targets Sigma1, a growing body of evidence supports the potential of Sigma1 ligands as therapeutic agents to treat cancer. In preclinical models, compounds with affinity for Sigma1 have been reported to inhibit cancer cell proliferation and survival, cell adhesion and migration, tumor growth, to alleviate cancer-associated pain, and to have immunomodulatory properties. This review will highlight that although the literature supports a role for Sigma1 in cancer, several fundamental questions regarding drug mechanism of action and the physiological relevance of aberrant SIGMAR1 transcript and Sigma1 protein expression in certain cancers remain unanswered or only partially answered. However, emerging lines of evidence suggest that Sigma1 is a component of the cancer cell support machinery, that it facilitates protein interaction networks, that it allosterically modulates the activity of its associated proteins, and that Sigma1 is a selectively multifunctional drug target.
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Affiliation(s)
- Felix J Kim
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA, USA.
- Sidney Kimmel Cancer Center, Philadelphia, PA, USA.
| | - Christina M Maher
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA, USA
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Weber F, Brune S, Börgel F, Lange C, Korpis K, Bednarski PJ, Laurini E, Fermeglia M, Pricl S, Schepmann D, Wünsch B. Rigidity versus Flexibility: Is This an Issue in σ1 Receptor Ligand Affinity and Activity? J Med Chem 2016; 59:5505-19. [PMID: 27156565 DOI: 10.1021/acs.jmedchem.6b00585] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Stereoisomeric 2,5-diazabicyclo[2.2.2]octanes 14 and 15 were prepared in a chiral-pool synthesis starting from (S)- or (R)-aspartate. The key step in the synthesis was a Dieckmann-analogous cyclization of (dioxopiperazinyl)acetates 8, which involved trapping of the intermediate hemiketal anion with Me3SiCl. The σ1 affinity was tested using membrane preparations from animal (guinea pig) and human origin. The binding of bicyclic compounds was analyzed by molecular dynamics simulations based on a 3D homology model of the σ1 receptor. The good correlation between Ki values observed in the σ1 assays and calculated free binding energy, coupled with the identification of four crucial ligand/receptor interactions, allowed the formulation of structure-affinity relationships. In an in vitro antitumor assay with seven human tumor cell lines, the bicyclic compounds inhibited selectively the growth of the cell line A427, which is due to induction of apoptosis. In this assay, the compounds behave like the known σ1 receptor antagonist haloperidol.
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Affiliation(s)
- Frauke Weber
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster , Corrensstraße 48, D-48149 Münster, Germany
| | - Stefanie Brune
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster , Corrensstraße 48, D-48149 Münster, Germany
| | - Frederik Börgel
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster , Corrensstraße 48, D-48149 Münster, Germany
| | - Carsten Lange
- Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, University of Greifswald , Friedrich-Ludwig-Jahn-Straße 17, 17487 Greifswald, Germany
| | - Katharina Korpis
- Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, University of Greifswald , Friedrich-Ludwig-Jahn-Straße 17, 17487 Greifswald, Germany
| | - Patrick J Bednarski
- Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, University of Greifswald , Friedrich-Ludwig-Jahn-Straße 17, 17487 Greifswald, Germany
| | - Erik Laurini
- Molecular Simulations Engineering (MOSE) Laboratory, Department of Engineering and Architecture (DEA), University of Trieste , Via Valerio 6, 34127 Trieste, Italy
| | - Maurizio Fermeglia
- Molecular Simulations Engineering (MOSE) Laboratory, Department of Engineering and Architecture (DEA), University of Trieste , Via Valerio 6, 34127 Trieste, Italy
| | - Sabrina Pricl
- Molecular Simulations Engineering (MOSE) Laboratory, Department of Engineering and Architecture (DEA), University of Trieste , Via Valerio 6, 34127 Trieste, Italy.,National Interuniversity Consortium for Material Science and Technology (INSTM), Research Unit MOSE-DEA, University of Trieste , Via Valerio 6, 32127 Trieste, Italy
| | - Dirk Schepmann
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster , Corrensstraße 48, D-48149 Münster, Germany
| | - Bernhard Wünsch
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster , Corrensstraße 48, D-48149 Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC 1003-CiM), University of Münster, 48149 Münster, Germany
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van Waarde A, Rybczynska AA, Ramakrishnan NK, Ishiwata K, Elsinga PH, Dierckx RAJO. Potential applications for sigma receptor ligands in cancer diagnosis and therapy. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1848:2703-14. [PMID: 25173780 DOI: 10.1016/j.bbamem.2014.08.022] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/04/2014] [Accepted: 08/19/2014] [Indexed: 01/03/2023]
Abstract
Sigma receptors (sigma-1 and sigma-2) represent two independent classes of proteins. Their endogenous ligands may include the hallucinogen N,N-dimethyltryptamine (DMT) and sphingolipid-derived amines which interact with sigma-1 receptors, besides steroid hormones (e.g., progesterone) which bind to both sigma receptor subpopulations. The sigma-1 receptor is a ligand-regulated molecular chaperone with various ion channels and G-protein-coupled membrane receptors as clients. The sigma-2 receptor was identified as the progesterone receptor membrane component 1 (PGRMC1). Although sigma receptors are over-expressed in tumors and up-regulated in rapidly dividing normal tissue, their ligands induce significant cell death only in tumor tissue. Sigma ligands may therefore be used to selectively eradicate tumors. Multiple mechanisms appear to underlie cell killing after administration of sigma ligands, and the signaling pathways are dependent both on the type of ligand and the type of tumor cell. Recent evidence suggests that the sigma-2 receptor is a potential tumor and serum biomarker for human lung cancer and an important target for inhibiting tumor invasion and cancer progression. Current radiochemical efforts are focused on the development of subtype-selective radioligands for positron emission tomography (PET) imaging. Right now, the mostpromising tracers are [18F]fluspidine and [18F]FTC-146 for sigma-1 receptors and [11C]RHM-1 and [18F]ISO-1 for the sigma-2 subtype. Nanoparticles coupled to sigma ligands have shown considerable potential for targeted delivery of antitumor drugs in animal models of cancer, but clinical studies exploring this strategy in cancer patients have not yet been reported. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.
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Affiliation(s)
- Aren van Waarde
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
| | - Anna A Rybczynska
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Nisha K Ramakrishnan
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Kiichi Ishiwata
- Tokyo Metropolitan Institute of Gerontology, Research Team for Neuroimaging, 35-2 Sakae-Cho, Itabashi-Ku, Tokyo 173-0015, Japan
| | - Philip H Elsinga
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - Rudi A J O Dierckx
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ Groningen, The Netherlands; University of Ghent, University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
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Abstract
This review compares the biological and physiological function of Sigma receptors [σRs] and their potential therapeutic roles. Sigma receptors are widespread in the central nervous system and across multiple peripheral tissues. σRs consist of sigma receptor one (σ1R) and sigma receptor two (σ2R) and are expressed in numerous regions of the brain. The sigma receptor was originally proposed as a subtype of opioid receptors and was suggested to contribute to the delusions and psychoses induced by benzomorphans such as SKF-10047 and pentazocine. Later studies confirmed that σRs are non-opioid receptors (not an µ opioid receptor) and play a more diverse role in intracellular signaling, apoptosis and metabolic regulation. σ1Rs are intracellular receptors acting as chaperone proteins that modulate Ca2+ signaling through the IP3 receptor. They dynamically translocate inside cells, hence are transmembrane proteins. The σ1R receptor, at the mitochondrial-associated endoplasmic reticulum membrane, is responsible for mitochondrial metabolic regulation and promotes mitochondrial energy depletion and apoptosis. Studies have demonstrated that they play a role as a modulator of ion channels (K+ channels; N-methyl-d-aspartate receptors [NMDAR]; inositol 1,3,5 triphosphate receptors) and regulate lipid transport and metabolism, neuritogenesis, cellular differentiation and myelination in the brain. σ1R modulation of Ca2+ release, modulation of cardiac myocyte contractility and may have links to G-proteins. It has been proposed that σ1Rs are intracellular signal transduction amplifiers. This review of the literature examines the mechanism of action of the σRs, their interaction with neurotransmitters, pharmacology, location and adverse effects mediated through them.
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Affiliation(s)
- Colin G Rousseaux
- a Department of Pathology and Laboratory Medicine , University of Ottawa , Ottawa , ON , Canada and
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8
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Weber F, Brune S, Korpis K, Bednarski PJ, Laurini E, Dal Col V, Pricl S, Schepmann D, Wünsch B. Synthesis, Pharmacological Evaluation, and σ1 Receptor Interaction Analysis of Hydroxyethyl Substituted Piperazines. J Med Chem 2014; 57:2884-94. [DOI: 10.1021/jm401707t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Frauke Weber
- Institute
of Pharmaceutical and Medicinal Chemistry, University of Münster, Corrensstraße 48, D-48149 Münster, Germany
| | - Stefanie Brune
- Institute
of Pharmaceutical and Medicinal Chemistry, University of Münster, Corrensstraße 48, D-48149 Münster, Germany
| | - Katharina Korpis
- Institute
of Pharmacy, Department of Pharmaceutical and Medicinal Chemistry, University of Greifswald, F.-L.-Jahn-Straße 17, 17487 Greifswald, Germany
| | - Patrick J. Bednarski
- Institute
of Pharmacy, Department of Pharmaceutical and Medicinal Chemistry, University of Greifswald, F.-L.-Jahn-Straße 17, 17487 Greifswald, Germany
| | - Erik Laurini
- Molecular
Simulations Engineering (MOSE) Laboratory, Department of Engineering
and Architecture (DEA), University of Trieste, Via Valerio 6, 34127 Trieste, Italy
| | - Valentina Dal Col
- Molecular
Simulations Engineering (MOSE) Laboratory, Department of Engineering
and Architecture (DEA), University of Trieste, Via Valerio 6, 34127 Trieste, Italy
| | - Sabrina Pricl
- Molecular
Simulations Engineering (MOSE) Laboratory, Department of Engineering
and Architecture (DEA), University of Trieste, Via Valerio 6, 34127 Trieste, Italy
- National
Interuniversity Consortium for Material Science and Technology (INSTM),
Research Unit MOSE-DEA, University of Trieste, Via Valerio 6, 32127 Trieste, Italy
| | - Dirk Schepmann
- Institute
of Pharmaceutical and Medicinal Chemistry, University of Münster, Corrensstraße 48, D-48149 Münster, Germany
| | - Bernhard Wünsch
- Institute
of Pharmaceutical and Medicinal Chemistry, University of Münster, Corrensstraße 48, D-48149 Münster, Germany
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Korpis K, Weber F, Brune S, Wünsch B, Bednarski PJ. Involvement of apoptosis and autophagy in the death of RPMI 8226 multiple myeloma cells by two enantiomeric sigma receptor ligands. Bioorg Med Chem 2014; 22:221-33. [DOI: 10.1016/j.bmc.2013.11.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 11/08/2013] [Accepted: 11/16/2013] [Indexed: 10/26/2022]
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10
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Guo LW, Hajipour AR, Karaoglu K, Mavlyutov TA, Ruoho AE. Development of benzophenone-alkyne bifunctional sigma receptor ligands. Chembiochem 2012; 13:2277-89. [PMID: 23001760 DOI: 10.1002/cbic.201200427] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2012] [Indexed: 12/12/2022]
Abstract
Sigma (σ) receptors are unique non-opioid binding sites that are associated with a broad range of disease states. Sigma-2 receptors provide a promising target for diagnostic imaging and pharmacological interventions to curb tumor progression. Most recently, the progesterone receptor (PGRMC1, 25 kDa) has been shown to have σ2 receptor-like binding properties, thus highlighting the need to understand the biological function of an 18 kDa protein that exhibits σ2-like photoaffinity labeling (denoted here as σ2-18k) but the amino acid sequence of which is not known. In order to provide new tools for the study of the σ2-18k protein, we have developed bifunctional σ receptor ligands each bearing a benzophenone photo-crosslinking moiety and an alkyne group to which an azide-containing biotin affinity tag can be covalently attached through click chemistry after photo-crosslinking. Although several compounds showed favorable σ2 binding properties, the highest affinity (2 nM) and the greatest potency in blocking photolabeling of σ2-18k by a radioactive photoaffinity ligand was shown by compound 22. These benzophenone-alkyne σ receptor ligands might therefore be amenable for studying the σ2-18k protein through chemical biology approaches. To the best of our knowledge, these compounds represent the first reported benzophenone-containing clickable σ receptor ligands, which might potentially have broad applications based on the "plugging in" of various tags.
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Affiliation(s)
- Lian-Wang Guo
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1300 University Ave., Madison, WI 53706, USA
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A 96-well filtration method for radioligand binding analysis of σ receptor ligands. J Pharm Biomed Anal 2012; 71:157-61. [PMID: 22910107 DOI: 10.1016/j.jpba.2012.07.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 07/18/2012] [Accepted: 07/22/2012] [Indexed: 11/24/2022]
Abstract
σ receptors represent a potential drug target for numerous therapeutic indications including cancer, depression, psychostimulant abuse, and stroke. Most published radioligand binding studies for σ receptors utilize a low throughput method employing a "cell harvester." Higher throughput methods are required to facilitate efficient screening of large numbers of novel compounds. In this study, a series of reference compounds was analyzed with a new medium-throughput 96-well filtration method and the results were compared to those obtained using the conventional cell harvester-based method. The 96-well assay utilized rat liver membranes for the determination of both known σ receptor subtypes (σ(1) and σ(2)) because this tissue contains high densities of both subtypes and fulfills criteria required for reliable use with the 96-well format. The new method gave comparable K(i) values for reference ligands analyzed in parallel with samples prepared in rat brain membranes and processed on the traditional cell harvester. For σ(1) receptors, equivalent affinity values were observed for both methods/tissues. For σ(2) receptors, approximately 2-fold higher affinities were observed for most compounds in liver, as compared to brain membranes, but excellent correlation with brain-derived values was maintained. To further demonstrate the utility of the new method it was used to screen a novel series of 2(3H)-benzothiazolone compounds, resulting in the identification of several analogues with nanomolar affinity and greater than 50-fold specificity for σ(1) versus σ(2) receptors.
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