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Employing novel animal models in the design of clinically efficacious GPCR ligands. Curr Opin Cell Biol 2013; 27:117-25. [PMID: 24680437 PMCID: PMC3989050 DOI: 10.1016/j.ceb.2013.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/02/2013] [Accepted: 12/03/2013] [Indexed: 12/12/2022]
Abstract
The headline success of targeting GPCRs in human diseases has masked the fact that many GPCR drug discovery programmes fail. This is despite a substantial increase in our understanding of GPCR pharmacology that has provided an array of ligands that target both orthosteric and allosteric sites as well as ligands that show stimulus bias. From this plethora of pharmacological possibilities, can we design ligand properties that would deliver maximal clinical efficacy with lowest toxicity? This may be achieved through animal models that both validate a particular GPCR as a target as well as revealing the signalling mechanisms that underlie receptor-mediated physiological and clinical responses. In this article, we examine recent novel transgenic models being employed to address this issue.
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2
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Shapiro MG, Frazier SJ, Lester HA. Unparalleled control of neural activity using orthogonal pharmacogenetics. ACS Chem Neurosci 2012; 3:619-29. [PMID: 22896806 DOI: 10.1021/cn300053q] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 06/01/2012] [Indexed: 11/28/2022] Open
Abstract
Studying the functional architecture of the brain requires technologies to precisely measure and perturb the activity of specific neural cells and circuits in live animals. Substantial progress has been made in recent years to develop and apply such tools. In particular, technologies that provide precise control of activity in genetically defined populations of neurons have enabled the study of causal relationships between and among neural circuit elements and behavioral outputs. Here, we review an important subset of such technologies, in which neurons are genetically engineered to respond to specific chemical ligands that have no interfering pharmacological effect in the central nervous system. A rapidly expanding set of these "orthogonal pharmacogenetic" tools provides a unique combination of genetic specificity, functional diversity, spatiotemporal precision, and potential for multiplexing. We review the main classes of orthogonal pharmacogenetic technologies, including neuroreceptors to control neuronal excitability, systems to control gene transcription and translation, and general constructs to control protein-protein interactions, enzymatic function, and protein stability. We describe the key performance characteristics informing the use of these technologies in the brain, and potential directions for improvement and expansion of the orthogonal pharmacogenetics toolkit to enable more sophisticated systems neuroscience.
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Affiliation(s)
- Mikhail G. Shapiro
- Miller Research Institute, Department
of Bioengineering, and Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California
94720, United States
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3
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Kazakia GJ, Speer D, Shanbhag S, Majumdar S, Conklin BR, Nissenson RA, Hsiao EC. Mineral composition is altered by osteoblast expression of an engineered G(s)-coupled receptor. Calcif Tissue Int 2011; 89:10-20. [PMID: 21526395 PMCID: PMC3110278 DOI: 10.1007/s00223-011-9487-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 03/06/2011] [Indexed: 01/22/2023]
Abstract
Activation of the G(s) G protein-coupled receptor Rs1 in osteoblasts increases bone mineral density by 5- to 15-fold in mice and recapitulates histologic aspects of fibrous dysplasia of the bone. However, the effects of constitutive G(s) signaling on bone tissue quality are not known. The goal of this study was to determine bone tissue quality in mice resulting from osteoblast-specific constitutive G(s) activation, by the complementary techniques of FTIR spectroscopy and synchrotron radiation micro-computed tomography (SRμCT). Col1(2.3)-tTA/TetO-Rs1 double transgenic (DT) mice, which showed osteoblast-specific constitutive G(s) signaling activity by the Rs1 receptor, were created. Femora and calvariae of DT and wild-type (WT) mice (6 and 15 weeks old) were analyzed by FTIR spectroscopy. WT and DT femora (3 and 9 weeks old) were imaged by SRμCT. Mineral-to-matrix ratio was 25% lower (P = 0.010), carbonate-to-phosphate ratio was 20% higher (P = 0.025), crystallinity was 4% lower (P = 0.004), and cross-link ratio was 11% lower (P = 0.025) in 6-week DT bone. Differences persisted in 15-week animals. Quantitative SRμCT analysis revealed substantial differences in mean values and heterogeneity of tissue mineral density (TMD). TMD values were 1,156 ± 100 and 711 ± 251 mg/cm(3) (mean ± SD) in WT and DT femoral diaphyses, respectively, at 3 weeks. Similar differences were found in 9-week animals. These results demonstrate that continuous G(s) activation in murine osteoblasts leads to deposition of immature bone tissue with reduced mineralization. Our findings suggest that bone tissue quality may be an important contributor to increased fracture risk in fibrous dysplasia patients.
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Affiliation(s)
- G J Kazakia
- Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA 94107, USA.
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4
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Abstract
A significant challenge for neuroscientists is to determine how both electrical and chemical signals affect the activity of cells and circuits and how the nervous system subsequently translates that activity into behavior. Remote, bidirectional manipulation of those signals with high spatiotemporal precision is an ideal approach to addressing that challenge. Neuroscientists have recently developed a diverse set of tools that permit such experimental manipulation with varying degrees of spatial, temporal, and directional control. These tools use light, peptides, and small molecules to primarily activate ion channels and G protein-coupled receptors (GPCRs) that in turn activate or inhibit neuronal firing. By monitoring the electrophysiological, biochemical, and behavioral effects of such activation/inhibition, researchers can better understand the links between brain activity and behavior. Here, we review the tools that are available for this type of experimentation. We describe the development of the tools and highlight exciting in vivo data. We focus primarily on designer GPCRs (receptors activated solely by synthetic ligands, designer receptors exclusively activated by designer drugs) and microbial opsins (e.g., channelrhodopsin-2, halorhodopsin, Volvox carteri channelrhodopsin) but also describe other novel techniques that use orthogonal receptors, caged ligands, allosteric modulators, and other approaches. These tools differ in the direction of their effect (activation/inhibition, hyperpolarization/depolarization), their onset and offset kinetics (milliseconds/minutes/hours), the degree of spatial resolution they afford, and their invasiveness. Although none of these tools is perfect, each has advantages and disadvantages, which we describe, and they are all still works in progress. We conclude with suggestions for improving upon the existing tools.
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Affiliation(s)
- Sarah C Rogan
- University of North Carolina School of Medicine, Department of Pharmacology, 120 Mason Farm Rd, Chapel Hill, NC 27514, USA
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5
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Hsiao EC, Nguyen TD, Ng JK, Scott MJ, Chang WC, Zahed H, Conklin BR. Constitutive Gs activation using a single-construct tetracycline-inducible expression system in embryonic stem cells and mice. Stem Cell Res Ther 2011; 2:11. [PMID: 21375737 PMCID: PMC3226282 DOI: 10.1186/scrt52] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Accepted: 03/04/2011] [Indexed: 01/19/2023] Open
Abstract
INTRODUCTION The controlled expression of many genes, including G-protein coupled receptors (GPCRs), is important for delineating gene functions in complex model systems. Binary systems for inducible regulation of transgene expression are widely used in mice. One system is the tTA/TRE expression system, composed of a tetracycline-dependent DNA binding factor and a separate tetracycline operon. However, the requirement for two separate transgenes (one for each tTA or TRE component) makes this system less amenable to models requiring directed cell targeting, increases the risk of multiple transgene integration sites, and requires extensive screening for appropriately-functioning clones. METHODS We developed a single, polycistronic tetracycline-inducible expression platform to control the expression of multiple cistrons in mammalian cells. This platform has three basic constructs: regulator, responder, and destination vectors. The modular platform is compatible with both the TetOff (tTA) and TetOn (rtTA) systems. The modular Gateway recombineering-compatible components facilitate rapidly generating vectors to genetically modify mammalian cells. We apply this system to use the elongation factor 1α (EF1α) promoter to drive doxycycline-regulated expression of both the fluorescent marker mCherry and an engineered Gs-coupled GPCR "Rs1" separated by a 2A ribosomal skip site. RESULTS We show that our combined expression construct drives expression of both the mCherry and Rs1 transgenes in a doxycycline-dependent manner. We successfully target the expression construct into the Rosa26 locus of mouse embryonic stem (ES) cells. Rs1 expression in mouse ES cells increases cAMP accumulation via both basal and ligand-induced Gs mechanisms and is associated with increased embryoid body size. Heterozygous mice carrying the Rs1 expression construct showed normal growth and weight, and developed small increases in bone formation that could be observed in the calvaria. CONCLUSIONS Our results demonstrate the feasibility of a single-vector strategy that combines both the tTA and TRE tetracycline-regulated components for use in cells and mouse models. Although the EF1α promoter is useful for driving expression in pluripotent cells, a single copy of the EF1α promoter did not drive high levels of mCherry and Rs1 expression in the differentiated tissues of adult mice. These findings indicate that promoter selection is an important factor when developing transgene expression models.
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Affiliation(s)
- Edward C Hsiao
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St., San Francisco, CA 94158, USA
- Division of Endocrinology and Metabolism, Department of Medicine, 400 Parnassus Ave., University of California, San Francisco, CA 94143-1222, USA
| | - Trieu D Nguyen
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St., San Francisco, CA 94158, USA
| | - Jennifer K Ng
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St., San Francisco, CA 94158, USA
| | - Mark J Scott
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St., San Francisco, CA 94158, USA
| | - Wei Chun Chang
- Department of Cellular and Molecular Pharmacology, 600 16th Street Rm. S-222, University of California, San Francisco, CA 94158-2140, USA
| | - Hengameh Zahed
- Gladstone Institute of Neurological Disease, 1650 Owens St., San Francisco, CA 94158, USA
- Biomedical Sciences Graduate Program, 513 Parnassus Ave. Rm. HSE-1285, University of California, San Francisco, CA 94158-0505, USA
| | - Bruce R Conklin
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St., San Francisco, CA 94158, USA
- Department of Medicine, 505 Parnassus Ave., University of California, San Francisco, CA 94143, USA
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6
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Masseck OA, Rubelowski JM, Spoida K, Herlitze S. Light- and drug-activated G-protein-coupled receptors to control intracellular signalling. Exp Physiol 2010; 96:51-6. [PMID: 21041315 DOI: 10.1113/expphysiol.2010.055517] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
G-protein-coupled receptors (GPCRs) integrate extracellular cues into intracellular signals to modulate the cellular state. Owing to their diverse modulatory functions, GPCRs represent one of the major drug targets of the pharmaceutical industry. Until now, the characterization and control of GPCRs and their intracellular signalling cascades have mainly relied on chemical compounds, which either activate or inhibit GPCR pathways, albeit with limited receptor and cell-type specificity. Recently, new approaches have been developed to control signalling cascades in cell- and receptor-type-specific ways. The chemical approach focuses on GPCR design and activation by an inert chemical compound, whereas the physical approach uses designer GPCRs and activation by physical stimuli, such as light.
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Affiliation(s)
- Olivia A Masseck
- Department of General Zoology and Neurobiology, Ruhr-University, Bochum, Germany
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7
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Hsiao EC, Boudignon BM, Halloran BP, Nissenson RA, Conklin BR. Gs G protein-coupled receptor signaling in osteoblasts elicits age-dependent effects on bone formation. J Bone Miner Res 2010; 25:584-93. [PMID: 20200944 PMCID: PMC3153396 DOI: 10.1002/jbmr.3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Age-dependent changes in skeletal growth are important for regulating skeletal expansion and determining peak bone mass. However, how G protein-coupled receptors (GPCRs) regulate these changes is poorly understood. Previously, we described a mouse model expressing Rs1, an engineered receptor with high basal G(s) activity. Rs1 expression in osteoblasts induced a dramatic age-dependent increase in trabecular bone with features resembling fibrous dysplasia. To further investigate how activation of the G(s)-GPCR pathway affects bone formation at different ages, we used the tetracycline-inducible system in the ColI(2.3)(+)/Rs1(+) mouse model to control the timing of Rs1 expression. We found that the Rs1 phenotype developed rapidly between postnatal days 4 and 6, that delayed Rs1 expression resulted in attenuation of the Rs1 phenotype, and that the Rs1-induced bone growth and deformities were markedly reversed when Rs1 expression was suppressed in adult mice. These findings suggest a distinct window of increased osteoblast responsiveness to G(s) signaling during the early postnatal period. In addition, adult bones encode information about their normal shape and structure independently from mechanisms regulating bone expansion. Finally, our model provides a powerful tool for investigating the effects of continuous G(s)-GPCR signaling on dynamic bone growth and remodeling.
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Affiliation(s)
- Edward C Hsiao
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA.
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8
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Hsiao EC, Millard SM, Louie A, Huang Y, Conklin BR, Nissenson RA. Ligand-mediated activation of an engineered gs g protein-coupled receptor in osteoblasts increases trabecular bone formation. Mol Endocrinol 2010; 24:621-31. [PMID: 20150184 DOI: 10.1210/me.2009-0424] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Age-dependent changes in skeletal growth play important roles in regulating skeletal expansion and in the course of many diseases affecting bone. How G protein-coupled receptor (GPCR) signaling affects these changes is poorly understood. Previously, we described a mouse model expressing Rs1, an engineered receptor with constitutive G(s) activity. Rs1 expression in osteoblasts from gestation induced a dramatic age-dependent increase in trabecular bone with features resembling fibrous dysplasia; however, these changes were greatly minimized if Rs1 expression was delayed until after puberty. To further investigate whether ligand-induced activation of the G(s)-GPCR pathway affects bone formation in adult mice, we activated Rs1 in adult mice with the synthetic ligand RS67333 delivered continuously via an osmotic pump or intermittently by daily injections. We found that osteoblasts from adult animals can be stimulated to form large amounts of bone, indicating that adult mice are sensitive to the dramatic bone- forming actions of G(s) signaling in osteoblasts. In addition, our results show that intermittent and continuous activation of Rs1 led to structurally similar but quantitatively different degrees of trabecular bone formation. These results indicate that activation of a G(s)-coupled receptor in osteoblasts of adult animals by either intermittent or continuous ligand administration can increase trabecular bone formation. In addition, osteoblasts located at the bone epiphyses may be more responsive to G(s) signaling than osteoblasts at the bone diaphysis. This model provides a powerful tool for investigating the effects of ligand-activated G(s)-GPCR signaling on dynamic bone growth and remodeling.
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Affiliation(s)
- Edward C Hsiao
- Gladstone Institute of Cardiovascular Disease, 1650 Owens Street, San Francisco, California 94158, USA.
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9
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Nichols CD, Roth BL. Engineered G-protein Coupled Receptors are Powerful Tools to Investigate Biological Processes and Behaviors. Front Mol Neurosci 2009; 2:16. [PMID: 19893765 PMCID: PMC2773177 DOI: 10.3389/neuro.02.016.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 09/12/2009] [Indexed: 12/03/2022] Open
Abstract
Understanding how discreet tissues and neuronal circuits function in relation to the whole organism to regulate physiological processes and behaviors is a fundamental goal of modern biological science. Powerful and important new tools in this discovery process are modified G-protein coupled receptors (GPCRs) known as ‘Receptors Activated Solely by Synthetic Ligands (RASSLs),’ and ‘Designer Receptors Exclusively Activated by a Designer Drug (DREADDs).’ Collectively, these are GPCRs modified either through rational design or directed molecular evolution, that do not respond to native ligand, but functionally respond only to synthetic ligands. Importantly, the utility of these receptors is not limited to examination of the role of GPCR-coupled effector signal transduction pathways. Due to the near ubiquitous expression of GPCRs throughout an organism, this technology, combined with whole animal transgenics to selectively target expression, has the ability to regulate activity of discreet tissues and neuronal circuits through effector pathway modulation to study function and behavior throughout the organism. Advantages over other systems currently used to modify in vivo function include the ability to rapidly, selectively and reversibly manipulate defined signal transduction pathways both in short term and long term studies, and no need for specialized equipment due to convenient systemic treatment with activating ligand.
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Affiliation(s)
- Charles D Nichols
- Department of Pharmacology and Therapeutics, Louisiana State University Health Sciences Center New Orleans, LA, USA
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10
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Pei Y, Rogan SC, Yan F, Roth BL. Engineered GPCRs as tools to modulate signal transduction. Physiology (Bethesda) 2009; 23:313-21. [PMID: 19074739 DOI: 10.1152/physiol.00025.2008] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Different families of G-protein-coupled receptors (GPCRs) have been engineered to provide exclusive control over the activation of these receptors and thus to understand better the consequences of their signaling in vitro and in vivo. These engineered receptors, named RASSLs (receptors activated solely by synthetic ligands) and DREADDs (designer receptors exclusively activated by designer drugs), are insensitive to their endogenous ligands but can be activated by synthetic drug-like compounds. Currently, the existing RASSLs and DREADDs cover the Gi, Gq, and Gs signaling pathways. These modified GPCRs can be utilized as ideal tools to study GPCR functions selectively in specific cellular populations.
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Affiliation(s)
- Ying Pei
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, USA
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11
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Conklin BR, Hsiao EC, Claeysen S, Dumuis A, Srinivasan S, Forsayeth JR, Guettier JM, Chang WC, Pei Y, McCarthy KD, Nissenson RA, Wess J, Bockaert J, Roth BL. Engineering GPCR signaling pathways with RASSLs. Nat Methods 2008; 5:673-8. [PMID: 18668035 DOI: 10.1038/nmeth.1232] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We are creating families of designer G protein-coupled receptors (GPCRs) to allow for precise spatiotemporal control of GPCR signaling in vivo. These engineered GPCRs, called receptors activated solely by synthetic ligands (RASSLs), are unresponsive to endogenous ligands but can be activated by nanomolar concentrations of pharmacologically inert, drug-like small molecules. Currently, RASSLs exist for the three major GPCR signaling pathways (G(s), G(i) and G(q)). We review these advances here to facilitate the use of these powerful and diverse tools.
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Affiliation(s)
- Bruce R Conklin
- Gladstone Institute of Cardiovascular Disease, 1650 Owens Street, San Francisco, California 94158, USA.
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12
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Wang S, Guo F, Liu K, Wang H, Rao S, Yang P, Jiang C. Endocytosis of the receptor-binding domain of SARS-CoV spike protein together with virus receptor ACE2. Virus Res 2008; 136:8-15. [PMID: 18554741 PMCID: PMC7114441 DOI: 10.1016/j.virusres.2008.03.004] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 03/03/2008] [Accepted: 03/07/2008] [Indexed: 01/10/2023]
Abstract
Cell entry of severe acute respiratory syndrome coronavirus (SARS-CoV) is mediated by the viral spike (S) protein. Amino acids 319-510 on the S protein have been mapped as the receptor-binding domain (RBD), which mediates binding to the SARS-CoV receptor angiotensin converting enzyme 2 (ACE2) on SARS-CoV susceptible cells. In this study, we expressed a fusion protein containing the human codon-optimized RBD of the SARS-CoV spike protein linked to the Fc portion of human IgG1 (named RBD-Fc) in HEK293 cells. The RBD-Fc protein was purified by affinity chromatography. The flow cytometry assay showed that the purified RBD-Fc protein could bind to ACE2. We demonstrated that the RBD spike protein alone could be internalized into SARS-CoV susceptible cells together with ACE2. We also showed that the removal of N-glycans from the RBD spike protein did not abolish this phenomenon. Our discoveries may have some implications for the development of the SARS vaccine.
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Affiliation(s)
- Shunxin Wang
- National Key Laboratory of Medical Molecular Biology, School of Basic Medicine, Peking Union Medical College, Tsinghua University and Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, Beijing 100005, China
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13
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Peng J, Bencsik M, Louie A, Lu W, Millard S, Nguyen P, Burghardt A, Majumdar S, Wronski TJ, Halloran B, Conklin BR, Nissenson RA. Conditional expression of a Gi-coupled receptor in osteoblasts results in trabecular osteopenia. Endocrinology 2008; 149:1329-37. [PMID: 18048501 PMCID: PMC2275363 DOI: 10.1210/en.2007-0235] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
G protein-coupled receptors (GPCRs) coupled to activation of Gs, such as the PTH1 receptor (PTH1R), have long been known to regulate skeletal function and homeostasis. However, the role of GPCRs coupled to other G proteins such as Gi is not well established. We used the tet-off system to regulate the expression of an activated Gi-coupled GPCR (Ro1) in osteoblasts in vivo. Skeletal phenotypes were assessed in mice expressing Ro1 from conception, from late stages of embryogenesis, and after weaning. Long bones were assessed histologically and by microcomputed tomography. Expression of Ro1 from conception resulted in neonatal lethality that was associated with reduced bone mineralization. Expression of Ro1 starting at late embryogenesis resulted in a severe trabecular bone deficit at 12 wk of age (>51% reduction in trabecular bone volume fraction in the proximal tibia compared with sex-matched control littermates; n = 11; P < 0.01). Ro1 expression for 8 wk beginning at 4 wk of age resulted in a more than 20% reduction in trabecular bone volume fraction compared with sex-matched control littermates (n = 16; P < 0.01). Bone histomorphometry revealed that Ro1 expression is associated with reduced rates of bone formation and mineral apposition without a significant change in osteoblast or osteoclast surface. Our results indicate that signaling by a Gi-coupled GPCR in osteoblasts leads to osteopenia resulting from a reduction in trabecular bone formation. The severity of the phenotype is related to the timing and duration of Ro1 expression during growth and development. The skeletal phenotype in Ro1 mice bears some similarity to that produced by knockout of Gs-alpha expression in osteoblasts and thus may be due at least in part to Gi-mediated inhibition of adenylyl cyclase.
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MESH Headings
- Animals
- Bone Density/physiology
- Bone Development/physiology
- Bone Diseases, Metabolic/metabolism
- Bone Diseases, Metabolic/pathology
- Bone and Bones/embryology
- Bone and Bones/metabolism
- Cells, Cultured
- Disease Models, Animal
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Gene Expression Regulation, Developmental/physiology
- Male
- Mice
- Mice, Transgenic
- Osteoblasts/metabolism
- Osteoblasts/pathology
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, kappa/genetics
- Receptors, Opioid, kappa/metabolism
- Signal Transduction/physiology
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Affiliation(s)
- J Peng
- Endocrine Research Unit, Veterans' Affairs Medical Center, and Department of Medicine, University of California, San Francisco, California 94121, USA
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14
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Mu opioid receptor mutant, T394A, abolishes opioid-mediated adenylyl cyclase superactivation. Neuroreport 2008; 18:1969-73. [PMID: 18007196 DOI: 10.1097/wnr.0b013e3282f228b2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
This study was to characterize the effects of a point-mutant at C-terminal of mu opioid receptor (MOR), namely MOR T394A, in chronic opioid-induced cellular responses. After 18 h of exposure to [D-Ala, N-Me-Phe, Gly-ol] enkephalin (DAMGO), adenylyl cyclase (AC) superactivation, a hallmark for the cellular adaptive response after chronic opioid stimulation, was observed in the cells expressing wild-type receptor, but was totally abolished in the cells expressing MOR T394A. Receptor phosphorylation was also attenuated in cells with MOR T394A after prolonged preexposure to agonist. Furthermore, MAP kinase kinase-1 (MKK1) overexpression was able to rescue AC superactivation in cells with MOR T394A, but showed no effect in the wild-type MOR-expressing cells. These results indicated that the amino acid T394 at C-terminus of MOR played a critical role in chronic agonist-induced AC superactivation and receptor phosphorylation.
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15
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Osteoblast expression of an engineered Gs-coupled receptor dramatically increases bone mass. Proc Natl Acad Sci U S A 2008; 105:1209-14. [PMID: 18212126 DOI: 10.1073/pnas.0707457105] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Osteoblasts are essential for maintaining bone mass, avoiding osteoporosis, and repairing injured bone. Activation of osteoblast G protein-coupled receptors (GPCRs), such as the parathyroid hormone receptor, can increase bone mass; however, the anabolic mechanisms are poorly understood. Here we use "Rs1," an engineered GPCR with constitutive G(s) signaling, to evaluate the temporal and skeletal effects of G(s) signaling in murine osteoblasts. In vivo, Rs1 expression induces a dramatic anabolic skeletal response, with midfemur girth increasing 1,200% and femur mass increasing 380% in 9-week-old mice. Bone volume, cellularity, areal bone mineral density, osteoblast gene markers, and serum bone turnover markers were also elevated. No such phenotype developed when Rs1 was expressed after the first 4 weeks of postnatal life, indicating an exquisite temporal sensitivity of osteoblasts to Rs1 expression. This pathway may represent an important determinant of bone mass and may open future avenues for enhancing bone repair and treating metabolic bone diseases.
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16
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Chang WC, Ng JK, Nguyen T, Pellissier L, Claeysen S, Hsiao EC, Conklin BR. Modifying ligand-induced and constitutive signaling of the human 5-HT4 receptor. PLoS One 2007; 2:e1317. [PMID: 18338032 PMCID: PMC2267039 DOI: 10.1371/journal.pone.0001317] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 11/18/2007] [Indexed: 11/26/2022] Open
Abstract
G protein–coupled receptors (GPCRs) signal through a limited number of G-protein pathways and play crucial roles in many biological processes. Studies of their in vivo functions have been hampered by the molecular and functional diversity of GPCRs and the paucity of ligands with specific signaling effects. To better compare the effects of activating different G-protein signaling pathways through ligand-induced or constitutive signaling, we developed a new series of RASSLs (receptors activated solely by synthetic ligands) that activate different G-protein signaling pathways. These RASSLs are based on the human 5-HT4b receptor, a GPCR with high constitutive Gs signaling and strong ligand-induced G-protein activation of the Gs and Gs/q pathways. The first receptor in this series, 5-HT4-D100A or Rs1 (RASSL serotonin 1), is not activated by its endogenous agonist, serotonin, but is selectively activated by the small synthetic molecules GR113808, GR125487, and RO110-0235. All agonists potently induced Gs signaling, but only a few (e.g., zacopride) also induced signaling via the Gq pathway. Zacopride-induced Gq signaling was enhanced by replacing the C-terminus of Rs1 with the C-terminus of the human 5-HT2C receptor. Additional point mutations (D66A and D66N) blocked constitutive Gs signaling and lowered ligand-induced Gq signaling. Replacing the third intracellular loop of Rs1 with that of human 5-HT1A conferred ligand-mediated Gi signaling. This Gi-coupled RASSL, Rs1.3, exhibited no measurable signaling to the Gs or Gq pathway. These findings show that the signaling repertoire of Rs1 can be expanded and controlled by receptor engineering and drug selection.
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Affiliation(s)
- Wei Chun Chang
- Gladstone Institute of Cardiovascular Disease, University of California at San Francisco, San Francisco, California, United States of America
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California at San Francisco, San Francisco, California, United States of America
| | - Jennifer K. Ng
- Gladstone Institute of Cardiovascular Disease, University of California at San Francisco, San Francisco, California, United States of America
| | - Trieu Nguyen
- Gladstone Institute of Cardiovascular Disease, University of California at San Francisco, San Francisco, California, United States of America
| | - Lucie Pellissier
- Institut de Génomique Fonctionnelle, Universités de Montpellier, CNRS UMR 5203, Montpellier, France
- INSERM U661, Montpellier, France
| | - Sylvie Claeysen
- Institut de Génomique Fonctionnelle, Universités de Montpellier, CNRS UMR 5203, Montpellier, France
- INSERM U661, Montpellier, France
| | - Edward C. Hsiao
- Gladstone Institute of Cardiovascular Disease, University of California at San Francisco, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, San Francisco, California, United States of America
| | - Bruce R. Conklin
- Gladstone Institute of Cardiovascular Disease, University of California at San Francisco, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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17
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Fishman P, Jacobson K, Ochaion A, Cohen S, Bar-Yehuda S. The Anti-Cancer Effect of A 3 Adenosine Receptor Agonists: A Novel, Targeted Therapy. IMMUNOLOGY, ENDOCRINE & METABOLIC AGENTS IN MEDICINAL CHEMISTRY 2007; 7:298-303. [PMID: 34824647 PMCID: PMC8611655 DOI: 10.2174/187152207781369878] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The A3 adenosine receptor (A3AR) is highly expressed in various human solid tumor cells whereas low expression is found in the adjacent normal tissues. Activation of the A3AR with synthetic highly selective agonists, such as IB-MECA, Cl-IB-MECA or LJ529, induces tumor growth inhibition of melanoma, lymphoma, breast, hepatoma, prostate and colon carcinoma cells both in vitro and in vivo. Two molecular events take place upon receptor activation and include: a. receptor internalization and subsequent degradation, followed by decreased receptor mRNA and protein expression level. b. modulation of down-stream signal transduction pathways, including those related to Wnt and NF-κB. Subsequently, the levels of cyclin D1 and c-Myc are decreased leading to tumor growth inhibition. IB-MECA synergizes with chemotherapeutic agents to yield an additive anti-tumor effect and protects against myelotoxicity induced by chemotherapy. Taken together, A3AR agonists may be suggested as a new family of orally bioavailable compounds to be developed as potent inhibitors of malignant diseases.
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Affiliation(s)
- P. Fishman
- Can-Fite BioPharma Ltd., Kiryat-Matalon, Petah -Tikva, 49170, Israel
| | - K.A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - A. Ochaion
- Can-Fite BioPharma Ltd., Kiryat-Matalon, Petah -Tikva, 49170, Israel
| | - S. Cohen
- Can-Fite BioPharma Ltd., Kiryat-Matalon, Petah -Tikva, 49170, Israel
| | - S. Bar-Yehuda
- Can-Fite BioPharma Ltd., Kiryat-Matalon, Petah -Tikva, 49170, Israel
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18
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Teerawanichpan P, Hoffman T, Ashe P, Datla R, Selvaraj G. Investigations of combinations of mutations in the jellyfish green fluorescent protein (GFP) that afford brighter fluorescence, and use of a version (VisGreen) in plant, bacterial, and animal cells. Biochim Biophys Acta Gen Subj 2007; 1770:1360-8. [PMID: 17658219 DOI: 10.1016/j.bbagen.2007.06.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 06/01/2007] [Accepted: 06/11/2007] [Indexed: 02/02/2023]
Abstract
Among the GFPs used for imaging green fluorescence, the Emerald version has been considered the best GFP to use but there is no formal report on its construction or the relevance of the amino acid (aa) substitutions in it relative to the commonly used GFPs. Here, we have shown that a version of Emerald makes Escherichia coli host cells visibly green even under dim room light conditions. Exploiting this feature, we have determined for the first time whether the changes in the structure of Emerald protein brought about by the aa substitutions are all indeed essential for brightness. F64L and S72A accompanying the classical S65T substitution on the chromophore-bearing helix are essential. Two amino acid changes, one on the surface (N149K) of the beta barrel that encases the helix and the other (I167T) near the chromophore enhance the visible green colour individually and additively when present together. The other two substitutions, M153T (on the surface) and H231L (on the surface), do not contribute to the visible green phenotype, even though in earlier studies M153T has been reported to enhance GFP fluorescence. The GFP version with F64L-S65T-S72A-N149K-I167T is referred to as VisGreen. We found VisGreen and Emerald to be indistinguishable in their quantum yield, molar extinction coefficient, folding efficiency, or photosensitivity. VisGreen rendered bacterial, plant, and animal cells highly fluorescent. Interestingly, N149K in the above combination was not essential to render bacterial cells highly fluorescent.
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Affiliation(s)
- Prapapan Teerawanichpan
- Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Canada S7N 0W9
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19
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Xie Z, Westmoreland SV, Bahn ME, Chen GL, Yang H, Vallender EJ, Yao WD, Madras BK, Miller GM. Rhesus monkey trace amine-associated receptor 1 signaling: enhancement by monoamine transporters and attenuation by the D2 autoreceptor in vitro. J Pharmacol Exp Ther 2007; 321:116-27. [PMID: 17234900 DOI: 10.1124/jpet.106.116863] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor that directly responds to endogenous monoamines as well as amphetamine-related psychostimulants, including methamphetamine. In the present study, we demonstrate TAAR1 mRNA and protein expression in rhesus monkey brain regions associated with monoaminergic systems, variable cellular distribution of TAAR1 in rhesus monkey brain, and TAAR1 coexpression with the dopamine transporter (DAT) in a subset of dopamine neurons in both rhesus monkey and mouse substantia nigra. On this basis, we evaluated rhesus monkey TAAR1 activation by different compounds and its functional relation with monoamine transporters and the dopamine D2 receptor (D2) short isoform (D2s) autoreceptor in vitro using a cAMP response element-luciferase assay. TAAR1 activation by monoamines and amphetamine-related compounds was greatly enhanced by coexpression of dopamine, norepinephrine, or serotonin transporters, and the activation enhancement was blocked by monoamine transporter inhibitors. This enhancement did not occur in control experiments in which the dopamine D1 receptor (D1) was substituted for TAAR1. Furthermore, activation of TAAR1 by dopamine was completely inhibited by D2s when coexpressed with TAAR1, and this inhibition was blocked by the D2 antagonist raclopride. Last, dopamine activation of TAAR1 could induce c-FOS-luciferase expression but only in the presence of DAT, whereas dopamine activation of D1 resulted in equivalent c-FOS expression in the presence or absence of DAT. Together, these data reveal a broad agonist spectrum for TAAR1, a functional relation of TAAR1 with monoamine transporters and D2s, and a mechanism by which D2 receptor drugs can influence brain monoaminergic function and have efficacy through affecting TAAR1 signaling.
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MESH Headings
- Amphetamine/pharmacology
- Animals
- Autoreceptors/physiology
- Blotting, Western
- Cells, Cultured
- Central Nervous System Stimulants/pharmacology
- Dopamine Plasma Membrane Transport Proteins/physiology
- Electrophoresis, Polyacrylamide Gel
- Fluorescent Antibody Technique
- Genes, Reporter/physiology
- Immunohistochemistry
- Luciferases/metabolism
- Macaca mulatta
- Neurons/physiology
- Proto-Oncogene Proteins c-fos/physiology
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Radioligand Assay
- Receptors, Dopamine D1/physiology
- Receptors, Dopamine D2/physiology
- Receptors, G-Protein-Coupled/biosynthesis
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction/physiology
- Substantia Nigra/cytology
- Substantia Nigra/physiology
- Transfection
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Affiliation(s)
- Zhihua Xie
- Division of Neurochemistry, New England Primate Research Center, Harvard Medical School, One Pine Hill Dr., Southborough, MA 01772, USA
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20
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Gao ZG, Duong HT, Sonin T, Kim SK, Van Rompaey P, Van Calenbergh S, Mamedova L, Kim HO, Kim MJ, Kim AY, Liang BT, Jeong LS, Jacobson KA. Orthogonal activation of the reengineered A3 adenosine receptor (neoceptor) using tailored nucleoside agonists. J Med Chem 2006; 49:2689-702. [PMID: 16640329 PMCID: PMC3471142 DOI: 10.1021/jm050968b] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
An alternative approach to overcome the inherent lack of specificity of conventional agonist therapy can be the reengineering of the GPCRs and their agonists. A reengineered receptor (neoceptor) could be selectively activated by a modified agonist, but not by the endogenous agonist. Assisted by rhodopsin-based molecular modeling, we pinpointed mutations of the A(3) adenosine receptor (AR) for selective affinity enhancement following complementary modifications of adenosine. Ribose modifications examined included, at 3': amino, aminomethyl, azido, guanidino, ureido; and at 5': uronamido, azidodeoxy. N(6)-Variations included 3-iodobenzyl, 5-chloro-2-methyloxybenzyl, and methyl. An N(6)-3-iodobenzyl-3'-ureido adenosine derivative 10 activated phospholipase C in COS-7 cells (EC(50) = 0.18 microM) or phospholipase D in chick primary cardiomyocytes, both mediated by a mutant (H272E), but not the wild-type, A(3)AR. The affinity enhancements for 10 and the corresponding 3'-acetamidomethyl analogue 6 were >100-fold and >20-fold, respectively. 10 concentration-dependently protected cardiomyocytes transfected with the neoceptor against hypoxia. Unlike 10, adenosine activated the wild-type A(3)AR (EC(50) of 1.0 microM), but had no effect on the H272E mutant A(3)AR (100 microM). Compound 10 was inactive at human A(1), A(2A), and A(2B)ARs. The orthogonal pair comprising an engineered receptor and a modified agonist should be useful for elucidating signaling pathways and could be therapeutically applied to diseases following organ-targeted delivery of the neoceptor gene.
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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, USA
| | - Heng T. Duong
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tatiana Sonin
- Department of Cardiology, University of Connecticut Health Center, Farmington, CT 06030-1601
| | - Soo-Kyung Kim
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Philippe Van Rompaey
- Laboratory for Medicinal Chemistry, Faculty of Pharmaceutical Sciences (FFW), Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry, Faculty of Pharmaceutical Sciences (FFW), Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium
| | - Liaman Mamedova
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hea Ok Kim
- Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, Korea
| | - Myong Jung Kim
- Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, Korea
| | - Ae Yil Kim
- Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, Korea
| | - Bruce T. Liang
- Department of Cardiology, University of Connecticut Health Center, Farmington, CT 06030-1601
| | - Lak Shin Jeong
- Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, Korea
| | - 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, USA
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