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Cheng Q, Lamb P, Stevanovic K, Bernstein BJ, Fry SA, Cushman JD, Yakel JL. Differential signalling induced by α7 nicotinic acetylcholine receptors in hippocampal dentate gyrus in vitro and in vivo. J Physiol 2021; 599:4687-4704. [PMID: 34487349 DOI: 10.1113/jp280505] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 09/03/2021] [Indexed: 11/08/2022] Open
Abstract
The activation of α7 nicotinic acetylcholine receptors (nAChRs) has been shown to improve hippocampus-dependent learning and memory. α7 nAChRs are densely expressed among several different cell types in the hippocampus, with high Ca2+ permeability, although it is unclear if α7 nAChRs mobilize differential signalling mechanisms among distinct neuronal populations. To address this question, we compared α7 nAChR agonist-induced responses (i.e. calcium and cAMP changes) between granule cells and GABAergic neurons in the hippocampal dentate gyrus both in vitro and in vivo. In cultured organotypic hippocampal slices, we observed robust intracellular calcium and cAMP increases in dentate granule cells upon activation of α7 nAChRs. In contrast, GABAergic interneurons displayed little change in either calcium or cAMP concentration after α7 nAChR activation, even though they displayed much larger α7 nAChR current responses than those of dentate granule cells. We found that this was due to smaller α7 nAChR-induced Ca2+ rises in GABAergic interneurons. Thus, the regulation of the Ca2+ transients in different cell types resulted in differential subsequent intracellular signalling cascades and likely the ultimate outcome of α7 nAChR activation. Furthermore, we monitored neuronal activities of dentate granule cells and GABAergic interneurons in vivo via optic fibre photometry. We observed enhancement of neuronal activities after nicotine administration in dentate granule cells, but not in GABAergic neurons, which was absent in α7 nAChR-deficient granule cells. In summary, we reveal a mechanism for α7 nAChR-mediated increase of neuronal activity via cell type-specific intracellular signalling pathways. KEY POINTS: α7 nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the central nervous system and regulate a variety of brain functions including learning and memory. Understanding the cellular signalling mechanisms of their activations among different neuronal populations is important for delineating their actions in cognitive function, and developing effective treatment strategies for cognitive deficits. We report that α7 nAChR activation leads to Ca2+ and cAMP increases in granule cells (but not in GABAergic interneurons) in hippocampal dentate gyrus in vitro, a key region for pattern separation during learning. We also found that nicotine enhanced granule cell (but not in GABAergic interneurons) activity in an α7 nAChR-dependent manner via in vivo fibre photometry recording. Based on our findings, we propose that differential responses to α7 nAChR activation between granule cells and GABAergic interneurons is responsible for the increase of excitation by α7 nAChR agonists in hippocampal circuits synergistically.
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Affiliation(s)
- Qing Cheng
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA.,Biological/Biomedical Research Institute, North Carolina Central University, Durham, NC, USA
| | - Patricia Lamb
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
| | - Korey Stevanovic
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
| | - Briana J Bernstein
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
| | - Sydney A Fry
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
| | - Jesse D Cushman
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
| | - Jerrel L Yakel
- Neurobiology Laboratory, The National Institute of Environmental Health Sciences/National Institutes of Health, Durham, NC, USA
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Thiel G, Schmidt T, Rössler OG. Ca 2+ Microdomains, Calcineurin and the Regulation of Gene Transcription. Cells 2021; 10:cells10040875. [PMID: 33921430 PMCID: PMC8068893 DOI: 10.3390/cells10040875] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 12/18/2022] Open
Abstract
Ca2+ ions function as second messengers regulating many intracellular events, including neurotransmitter release, exocytosis, muscle contraction, metabolism and gene transcription. Cells of a multicellular organism express a variety of cell-surface receptors and channels that trigger an increase of the intracellular Ca2+ concentration upon stimulation. The elevated Ca2+ concentration is not uniformly distributed within the cytoplasm but is organized in subcellular microdomains with high and low concentrations of Ca2+ at different locations in the cell. Ca2+ ions are stored and released by intracellular organelles that change the concentration and distribution of Ca2+ ions. A major function of the rise in intracellular Ca2+ is the change of the genetic expression pattern of the cell via the activation of Ca2+-responsive transcription factors. It has been proposed that Ca2+-responsive transcription factors are differently affected by a rise in cytoplasmic versus nuclear Ca2+. Moreover, it has been suggested that the mode of entry determines whether an influx of Ca2+ leads to the stimulation of gene transcription. A rise in cytoplasmic Ca2+ induces an intracellular signaling cascade, involving the activation of the Ca2+/calmodulin-dependent protein phosphatase calcineurin and various protein kinases (protein kinase C, extracellular signal-regulated protein kinase, Ca2+/calmodulin-dependent protein kinases). In this review article, we discuss the concept of gene regulation via elevated Ca2+ concentration in the cytoplasm and the nucleus, the role of Ca2+ entry and the role of enzymes as signal transducers. We give particular emphasis to the regulation of gene transcription by calcineurin, linking protein dephosphorylation with Ca2+ signaling and gene expression.
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Papke RL, Lindstrom JM. Nicotinic acetylcholine receptors: Conventional and unconventional ligands and signaling. Neuropharmacology 2020; 168:108021. [PMID: 32146229 PMCID: PMC7610230 DOI: 10.1016/j.neuropharm.2020.108021] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/05/2020] [Accepted: 02/25/2020] [Indexed: 12/28/2022]
Abstract
Postsynaptic nAChRs in the peripheral nervous system are critical for neuromuscular and autonomic neurotransmission. Pre- and peri-synaptic nAChRs in the brain modulate neurotransmission and are responsible for the addictive effects of nicotine. Subtypes of nAChRs in lymphocytes and non-synaptic locations may modulate inflammation and other cellular functions. All AChRs that function as ligand-gated ion channels are formed from five homologous subunits organized to form a central cation channel whose opening is regulated by ACh bound at extracellular subunit interfaces. nAChR subtype subunit composition can range from α7 homomers to α4β2α6β2β3 heteromers. Subtypes differ in affinities for ACh and other agonists like nicotine and in efficiencies with which their channels are opened and desensitized. Subtypes also differ in affinities for antagonists and for positive and negative allosteric modulators. Some agonists are "silent" with respect to channel opening, and AChRs may be able to signal metabotropic pathways by releasing G-proteins independent of channel opening. Electrophysiological studies that can resolve single-channel openings and molecular genetic approaches have allowed characterization of the structures of ligand binding sites, the cation channel, and the linkages between them, as well as the organization of AChR subunits and their contributions to function. Crystallography and cryo-electron-microscopy are providing increasing insights into the structures and functions of AChRs. However, much remains to be learned about both AChR structure and function, the in vivo functional roles of some AChR subtypes, and the development of better pharmacological tools directed at AChRs to treat addiction, pain, inflammation, and other medically important issues. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL, 32610-0267, USA.
| | - Jon M Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Abstract
Human behavior can be controlled by physical or psychological dependencies associated with addiction. One of the most insidious addictions in our society is the use of tobacco products which contain nicotine. This addiction can be associated with specific receptors in the brain that respond to the natural neurotransmitter acetylcholine. These nicotinic acetylcholine receptors (nAChR) are ligand-gated ion channels formed by the assembly of one or multiple types of nAChR receptor subunits. In this paper, we review the structure and diversity of nAChR subunits and our understanding for how different nAChR subtypes play specific roles in the phenomenon of nicotine addiction. We focus on receptors containing β2 and/or α6 subunits and the special significance of α5-containing receptors. These subtypes all have roles in regulating dopamine-mediated neurotransmission in the mesolimbic reward pathways of the brain. We also discuss the unique roles of homomeric α7 nAChR in behavioral responses to nicotine and how our knowledge of nAChR functional diversity may help guide pharmacotherapeutic approaches for treating nicotine addiction. While nicotine addiction is a truly global problem, the use of areca nut (betel) products is also a serious addiction associated with public health issues across most of South Asia, impacting as many as 600 million people. We discuss how cholinergic receptors of the brain are also involved with areca addiction and the unique challenges for dealing with addiction to this substance.
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Gulsevin A, Papke RL, Horenstein N. In Silico Modeling of the α7 Nicotinic Acetylcholine Receptor: New Pharmacological Challenges Associated with Multiple Modes of Signaling. Mini Rev Med Chem 2020; 20:841-864. [PMID: 32000651 PMCID: PMC8719523 DOI: 10.2174/1389557520666200130105256] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022]
Abstract
The α7 nicotinic acetylcholine receptor is a homopentameric ion-channel of the Cys-loop superfamily characterized by its low probability of opening, high calcium permeability, and rapid desensitization. The α7 receptor has been targeted for the treatment of the cognitive symptoms of schizophrenia, depression, and Alzheimer's disease, but it is also involved in inflammatory modulation as a part of the cholinergic anti-inflammatory pathway. Despite its functional importance, in silico studies of the α7 receptor cannot produce a general model explaining the structural features of receptor activation, nor predict the mode of action for various ligand classes. Two particular problems in modeling the α7 nAChR are the absence of a high-resolution structure and the presence of five potentially nonequivalent orthosteric ligand binding sites. There is wide variability regarding the templates used for homology modeling, types of ligands investigated, simulation methods, and simulation times. However, a systematic survey focusing on the methodological similarities and differences in modeling α7 has not been done. In this work, we make a critical analysis of the modeling literature of α7 nAChR by comparing the findings of computational studies with each other and with experimental studies under the main topics of structural studies, ligand binding studies, and comparisons with other nAChR. In light of our findings, we also summarize current problems in the field and make suggestions for future studies concerning modeling of the α7 receptor.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610, United States
| | - Nicole Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
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6
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Calcineurin controls gene transcription following stimulation of a Gαq-coupled designer receptor. Exp Cell Res 2019; 383:111553. [DOI: 10.1016/j.yexcr.2019.111553] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/07/2019] [Accepted: 08/10/2019] [Indexed: 01/07/2023]
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7
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Dongsheng Z, Zhiguang F, Junfeng J, Zifan L, Li W. Cyclophilin A Aggravates Collagen-Induced Arthritis via Promoting Classically Activated Macrophages. Inflammation 2018; 40:1761-1772. [PMID: 28756520 DOI: 10.1007/s10753-017-0619-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Activated macrophages exhibiting diverse phenotypes and various functions contribute to the pathogenesis or amelioration of different diseases like cancer, inflammation, and infectious and autoimmune diseases. However, the mechanisms of macrophage polarization in inflamed joint and its effects on rheumatoid arthritis (RA) are still not clarified. This study is designed to explore the effects of cyclophilin A (CypA) on macrophage polarization and describe the underlying mechanisms. Collagen-induced arthritis (CIA) was employed to address the pro-arthritic effects of CypA. Flow cytometry was performed to investigate the populations of M1 and M2 macrophages in synovial tissues of the mice. Knockdown or overexpression of CypA macrophage cells was used to study the functions of CypA on macrophage polarization. Western blot was carried out to examine the potential signaling pathways. We found that CypA aggravated the severity of CIA in mice, as assessed by the increase of clinical score of inflammation, cartilage damage, and bone erosion. Moreover, the level of cytokines, such as IL-6, IL-1β, and IL-17, and the number of pro-inflammatory macrophages in synovial fluid were significantly elevated. In accordance with our observation, CypA dysregulation could actually influence the M1 macrophages polarization and pro-inflammatory cytokines production. Further mechanism study disclosed that CypA could regulate the transcriptional activity of NF-κB, the pivotal transcriptional factor regulating M1 polarization, dependent of its PPIase activity. Our findings provide evidence that PPIase CypA promoted macrophages polarization toward pro-inflammatory M1 phenotype via transcriptional activating NF-κB, thus leading to aggravated arthritis.
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Affiliation(s)
- Zhai Dongsheng
- State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, School of Pharmacy, Fourth Military Medical University, No. 169 West Changle Road, Xi'an, 710032, Shaanxi, People's Republic of China
| | - Fu Zhiguang
- Institute of Stomatology, General Hospital of Chinese PLA, Beijing, 10085, People's Republic of China
| | - Jia Junfeng
- Department of Clinical Immunology, State Key Discipline of Cell Biology, First Affiliated Hospital, Fourth Military Medical University, No. 15 West Changle Road, Xi'an, 710032, Shaanxi, People's Republic of China
| | - Lu Zifan
- State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, School of Pharmacy, Fourth Military Medical University, No. 169 West Changle Road, Xi'an, 710032, Shaanxi, People's Republic of China.
| | - Wang Li
- State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, School of Pharmacy, Fourth Military Medical University, No. 169 West Changle Road, Xi'an, 710032, Shaanxi, People's Republic of China.
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Xue C, Sowden MP, Berk BC. Extracellular and Intracellular Cyclophilin A, Native and Post-Translationally Modified, Show Diverse and Specific Pathological Roles in Diseases. Arterioscler Thromb Vasc Biol 2018; 38:986-993. [PMID: 29599134 DOI: 10.1161/atvbaha.117.310661] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Accepted: 03/20/2018] [Indexed: 01/13/2023]
Abstract
CypA (cyclophilin A) is a ubiquitous and highly conserved protein with peptidyl prolyl isomerase activity. Because of its highly abundant level in the cytoplasm, most studies have focused on the roles of CypA as an intracellular protein. However, emerging evidence suggests an important role for extracellular CypA in the pathogenesis of several diseases through receptor (CD147 or other)-mediated autocrine and paracrine signaling pathways. In this review, we will discuss the shared and unique pathological roles of extracellular and intracellular CypA in human cardiovascular diseases. In addition, the evolving role of post-translational modifications of CypA in the pathogenesis of disease is discussed. Finally, recent studies with drugs specific for extracellular CypA show its importance in disease pathogenesis in several animal models and make extracellular CypA a new therapeutic target.
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Affiliation(s)
- Chao Xue
- From the Department of Medicine, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, NY
| | - Mark P Sowden
- From the Department of Medicine, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, NY
| | - Bradford C Berk
- From the Department of Medicine, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, NY.
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Mulcahy MJ, Blattman SB, Barrantes FJ, Lukas RJ, Hawrot E. Resistance to Inhibitors of Cholinesterase 3 (Ric-3) Expression Promotes Selective Protein Associations with the Human α7-Nicotinic Acetylcholine Receptor Interactome. PLoS One 2015; 10:e0134409. [PMID: 26258666 PMCID: PMC4530945 DOI: 10.1371/journal.pone.0134409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/08/2015] [Indexed: 11/19/2022] Open
Abstract
The α7-nicotinic acetylcholine receptor (α7-nAChR) is a ligand-gated ion channel widely expressed in vertebrates and is associated with numerous physiological functions. As transmembrane ion channels, α7-nAChRs need to be expressed on the surface of the plasma membrane to function. The receptor has been reported to associate with proteins involved with receptor biogenesis, modulation of receptor properties, as well as intracellular signaling cascades and some of these associated proteins may affect surface expression of α7-nAChRs. The putative chaperone resistance to inhibitors of cholinesterase 3 (Ric-3) has been reported to interact with, and enhance the surface expression of, α7-nAChRs. In this study, we identified proteins that associate with α7-nAChRs when Ric-3 is expressed. Using α-bungarotoxin (α-bgtx), we isolated and compared α7-nAChR-associated proteins from two stably transfected, human tumor-derived cell lines: SH-EP1-hα7 expressing human α7-nAChRs and the same cell line further transfected to express Ric-3, SH-EP1-hα7-Ric-3. Mass spectrometric analysis of peptides identified thirty-nine proteins that are associated with α7-nAChRs only when Ric-3 was expressed. Significantly, and consistent with reports of Ric-3 function in the literature, several of the identified proteins are involved in biological processes that may affect nAChR surface expression such as post-translational processing of proteins, protein trafficking, and protein transport. Additionally, proteins affecting the cell cycle, the cytoskeleton, stress responses, as well as cyclic AMP- and inositol triphosphate-dependent signaling cascades were identified. These results illuminate how α-bgtx may be used to isolate and identify α7-nAChRs as well as how the expression of chaperones such as Ric-3 can influence proteins associating with α7-nAChRs. These associating proteins may alter activities of α7-nAChRs to expand their functionally-relevant repertoire as well as to affect biogenesis and membrane trafficking of α7-nAChRs.
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Affiliation(s)
- Matthew J. Mulcahy
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | - Sydney B. Blattman
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | - Francisco J. Barrantes
- Laboratory of Molecular Neurobiology, Institute of Biomedical Research, UCA-CONICET, Buenos Aires, Argentina
| | - Ronald J. Lukas
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona, United States of America
| | - Edward Hawrot
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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Ladani ST, Souffrant MG, Barman A, Hamelberg D. Computational perspective and evaluation of plausible catalytic mechanisms of peptidyl-prolyl cis-trans isomerases. Biochim Biophys Acta Gen Subj 2015; 1850:1994-2004. [PMID: 25585011 DOI: 10.1016/j.bbagen.2014.12.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 12/23/2014] [Accepted: 12/29/2014] [Indexed: 01/16/2023]
Abstract
BACKGROUND Peptidyl prolyl cis-trans isomerization of the protein backbone is involved in the regulation of many biological processes. Cis-trans isomerization is notoriously slow and is catalyzed by a family of cis-trans peptidyl prolyl isomerases (PPIases) that have been implicated in many diseases. A general consensus on how these enzymes speed up prolyl isomerization has not been reached after decades of both experimental and computational studies. SCOPE OF REVIEW Computational studies carried out to understand the catalytic mechanism of the prototypical FK506 binding protein 12, Cyclophilin A and peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1) are reviewed. A summary and an evaluation of the implications of the proposed mechanisms from computational studies are presented. MAJOR CONCLUSIONS The analysis of computational studies and evaluation of the proposed mechanisms provide a general consensus and a better understanding of PPIase catalysis. The speedup of the rate of peptidyl-prolyl isomerization by PPIases can be best described by a catalytic mechanism in which the substrate in transition state configuration is stabilized. The enzymes preferentially bind the transition state configuration of the substrate relative to the cis conformation, which in most cases is bound better than the trans conformation of the substrate. Stabilization of the transition state configuration of the substrate leads to a lower free energy barrier and a faster rate of isomerization when compared to the uncatalyzed isomerization reaction. GENERAL SIGNIFICANCE Fully understanding the catalytic mechanism of PPIases has broad implications for drug design, elucidation of the molecular basis of many diseases, protein engineering, and enzyme catalysis in general. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.
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Affiliation(s)
- Safieh Tork Ladani
- Department of Chemistry and the Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Michael G Souffrant
- Department of Chemistry and the Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Arghya Barman
- Department of Chemistry and the Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Donald Hamelberg
- Department of Chemistry and the Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-3965, USA.
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Nath PR, Isakov N. Insights into peptidyl-prolyl cis–trans isomerase structure and function in immunocytes. Immunol Lett 2015; 163:120-31. [DOI: 10.1016/j.imlet.2014.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 10/27/2014] [Accepted: 11/03/2014] [Indexed: 12/30/2022]
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12
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Tork Ladani S, Hamelberg D. Intricacies of interactions, dynamics and solvent effects in enzyme catalysis: a computational perspective on cyclophilin A. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.919498] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Cyclophilin A: a key player for human disease. Cell Death Dis 2013; 4:e888. [PMID: 24176846 PMCID: PMC3920964 DOI: 10.1038/cddis.2013.410] [Citation(s) in RCA: 296] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/10/2013] [Accepted: 09/11/2013] [Indexed: 01/23/2023]
Abstract
Cyclophilin A (CyPA) is a ubiquitously distributed protein belonging to the immunophilin family. CyPA has peptidyl prolyl cis-trans isomerase (PPIase) activity, which regulates protein folding and trafficking. Although CyPA was initially believed to function primarily as an intracellular protein, recent studies have revealed that it can be secreted by cells in response to inflammatory stimuli. Current research in animal models and humans has provided compelling evidences supporting the critical function of CyPA in several human diseases. This review discusses recently available data about CyPA in cardiovascular diseases, viral infections, neurodegeneration, cancer, rheumatoid arthritis, sepsis, asthma, periodontitis and aging. It is believed that further elucidations of the role of CyPA will provide a better understanding of the molecular mechanisms underlying these diseases and will help develop novel pharmacological therapies.
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Rahamimoff H, Elbaz B, Valitsky M, Khatib M, Eskin-Schwartz M, Elmaz D. Immunosuppressive Drugs, Immunophilins, and Functional Expression of NCX Isoforms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 961:275-87. [DOI: 10.1007/978-1-4614-4756-6_23] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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15
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Cohen-Kutner M, Yahalom Y, Trus M, Atlas D. Calcineurin Controls Voltage-Dependent-Inactivation (VDI) of the Normal and Timothy Cardiac Channels. Sci Rep 2012; 2:366. [PMID: 22511998 PMCID: PMC3328044 DOI: 10.1038/srep00366] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/22/2012] [Indexed: 12/25/2022] Open
Abstract
Ca2+-entry in the heart is tightly controlled by Cav1.2 inactivation, which involves Ca2+-dependent inactivation (CDI) and voltage-dependent inactivation (VDI) components. Timothy syndrome, a subtype-form of congenital long-QT syndrome, results from a nearly complete elimination of VDI by the G406R mutation in the α11.2 subunit of Cav1.2. Here, we show that a single (A1929P) or a double mutation (H1926A-H1927A) within the CaN-binding site at the human C-terminal tail of α11.2, accelerate the inactivation rate and enhances VDI of both wt and Timothy channels. These results identify the CaN-binding site as the long-sought VDI-regulatory motif of the cardiac channel. The substantial increase in VDI and the accelerated inactivation caused by the selective inhibitors of CaN, cyclosporine A and FK-506, which act at the same CaN-binding site, further support this conclusion. A reversal of enhanced-sympathetic tone by VDI-enhancing CaN inhibitors could be beneficial for improving Timothy syndrome complications such as long-QT and autism.
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Chaperoning α7 neuronal nicotinic acetylcholine receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:718-29. [PMID: 22040696 DOI: 10.1016/j.bbamem.2011.10.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2011] [Revised: 09/25/2011] [Accepted: 10/17/2011] [Indexed: 11/22/2022]
Abstract
The α7 subtype of nicotinic acetylcholine receptors (AChRs) is one of the most abundant members of the Cys-loop family of receptors present in the central nervous system. It participates in various physiological processes and has received much attention as a potential therapeutic target for a variety of pathologies. The importance of understanding the mechanisms controlling AChR assembly and cell-surface delivery lies in the fact that these two processes are key to determining the functional pool of receptors actively engaged in synaptic transmission. Here we review recent studies showing that RIC-3, a protein originally identified in the worm Caenorhabditis elegans, modulates the expression of α7 AChRs in a subtype-specific manner. Potentiation of AChR expression by post-transcriptional events is also critically assessed.
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Elbaz B, Valitsky M, Davidov G, Rahamimoff H. Cyclophilin A Is Involved in Functional Expression of the Na+−Ca2+ Exchanger NCX1. Biochemistry 2010; 49:7634-42. [DOI: 10.1021/bi1008722] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Benayahu Elbaz
- Department of Biochemistry and Molecular Biology, Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
| | - Michael Valitsky
- Department of Biochemistry and Molecular Biology, Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
| | - Geula Davidov
- Department of Biochemistry and Molecular Biology, Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
| | - Hannah Rahamimoff
- Department of Biochemistry and Molecular Biology, Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
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Acetylation regulates cyclophilin A catalysis, immunosuppression and HIV isomerization. Nat Chem Biol 2010; 6:331-7. [PMID: 20364129 PMCID: PMC3867001 DOI: 10.1038/nchembio.342] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 01/14/2010] [Indexed: 02/08/2023]
Abstract
The detailed characterization of endogenous proteins and use of non-natural amino acid engineering allows the identification and structural and functional analysis of a post-translational modification in regulating ligand binding and enzyme activity.![]() Cyclophilin A (CypA) is a ubiquitous cis–trans prolyl isomerase with key roles in immunity and viral infection. CypA suppresses T-cell activation through cyclosporine complexation and is required for effective HIV-1 replication in host cells. We show that CypA is acetylated in diverse human cell lines and use a synthetically evolved acetyllysyl-tRNA synthetase/tRNACUA pair to produce recombinant acetylated CypA in Escherichia coli. We determined atomic-resolution structures of acetylated CypA and its complexes with cyclosporine and HIV-1 capsid. Acetylation markedly inhibited CypA catalysis of cis to trans isomerization and stabilized cis rather than trans forms of the HIV-1 capsid. Furthermore, CypA acetylation antagonized the immunosuppressive effects of cyclosporine by inhibiting the sequential steps of cyclosporine binding and calcineurin inhibition. Our results reveal that acetylation regulates key functions of CypA in immunity and viral infection and provide a general set of mechanisms by which acetylation modulates interactions to regulate cell function.
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Barnes NM, Hales TG, Lummis SC, Peters JA. The 5-HT3 receptor--the relationship between structure and function. Neuropharmacology 2009; 56:273-84. [PMID: 18761359 PMCID: PMC6485434 DOI: 10.1016/j.neuropharm.2008.08.003] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/31/2008] [Accepted: 08/01/2008] [Indexed: 12/15/2022]
Abstract
The 5-hydroxytryptamine type-3 (5-HT3) receptor is a cation-selective ion channel of the Cys-loop superfamily. 5-HT3 receptor activation in the central and peripheral nervous systems evokes neuronal excitation and neurotransmitter release. Here, we review the relationship between the structure and the function of the 5-HT3 receptor. 5-HT3A and 5-HT3B subunits are well established components of 5-HT3 receptors but additional HTR3C, HTR3D and HTR3E genes expand the potential for molecular diversity within the family. Studies upon the relationship between subunit structure and the ionic selectivity and single channel conductances of 5-HT3 receptors have identified a novel domain (the intracellular MA-stretch) that contributes to ion permeation and selectivity. Conventional and unnatural amino acid mutagenesis of the extracellular domain of the receptor has revealed residues, within the principle (A-C) and complementary (D-F) loops, which are crucial to ligand binding. An area requiring much further investigation is the subunit composition of 5-HT3 receptors that are endogenous to neurones, and their regional expression within the central nervous system. We conclude by describing recent studies that have identified numerous HTR3A and HTR3B gene polymorphisms that impact upon 5-HT3 receptor function, or expression, and consider their relevance to (patho)physiology.
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Affiliation(s)
- Nicholas M. Barnes
- Cellular and Molecular Neuropharmacology Research Group, Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Tim G. Hales
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, USA
| | - Sarah C.R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - John A. Peters
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, The University of Dundee, Dundee DD1 9SY, UK
- Corresponding author. Tel.: +44 01382 660111x33117; fax: +44 01382 667120. E-mail address: (J.A. Peters)
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Millar NS, Harkness PC. Assembly and trafficking of nicotinic acetylcholine receptors (Review). Mol Membr Biol 2008; 25:279-92. [PMID: 18446614 DOI: 10.1080/09687680802035675] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are members of an extensive super-family of neurotransmitter-gated ion channels. In humans, nAChRs are expressed within the nervous system and at the neuromuscular junction and are important targets for pharmaceutical drug discovery. They are also the site of action for neuroactive pesticides in insects and other invertebrates. Nicotinic receptors are complex pentameric transmembrane proteins which are assembled from a large family of subunits; seventeen nAChR subunits (alpha1-alpha10, beta1-beta4, gamma, delta and epsilon) have been identified in vertebrate species. This review will discuss nAChR subunit diversity and factors influencing receptor assembly and trafficking.
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Affiliation(s)
- Neil S Millar
- Department of Pharmacology, University College London, London, UK.
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22
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Elbaz B, Alperovitch A, Gottesman MM, Kimchi-Sarfaty C, Rahamimoff H. Modulation of Na+-Ca2+Exchanger Expression by Immunosuppressive Drugs Is Isoform-Specific. Mol Pharmacol 2008; 73:1254-63. [DOI: 10.1124/mol.107.041582] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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23
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Rahamimoff H, Elbaz B, Alperovich A, Kimchi-Sarfaty C, Gottesman MM, Lichtenstein Y, Eskin-Shwartz M, Kasir J. Cyclosporin A-dependent downregulation of the Na+/Ca2+ exchanger expression. Ann N Y Acad Sci 2007; 1099:204-14. [PMID: 17446460 DOI: 10.1196/annals.1387.046] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cyclosporin A (CsA) is an immunosuppressive drug commonly given to transplant patients. Its application is accompanied by severe side effects related to calcium, among them hypertension and nephrotoxicity. The Na+/Ca2+ exchanger (NCX) is a major calcium regulator expressed in the surface membrane of all excitable and many nonexcitable tissues. Three genes, NCX1, NCX2, and NCX3 code for Na+/Ca2+ exchange activity. NCX1 gene products are the most abundant. We have shown previously that exposure of NCX1-transfected HEK 293 cells to CsA, leads to concentration-dependent reduction of Na+/Ca2+ exchange activity and surface expression, without a reduction in total cell-expressed NCX1 protein. We show now that the effect of CsA on NCX1 protein expression is not restricted to transfected cells overexpressing the NCX1 protein but exhibited also in cells expressing endogenously the NCX1 protein (L6, H9c2, and primary smooth muscle cells). Exposure of NCX2- and NCX3-transfected cells to CsA results also in reduction of Na+/Ca2+ exchange activity and surface expression, though the sensitivity to the drug was lower than in NCX1-transfected cells. Studying the molecular mechanism of CsA-NCX interaction suggests that cyclophilin (Cyp) is involved in NCX1 protein expression and its modulation by CsA. Deletion of 426 amino acids from the large cytoplasmic loop of the protein retains the CsA-dependent downregulation of the truncated NCX1 suggesting that CsA-Cyp-NCX interaction involves the remaining protein domains.
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Affiliation(s)
- H Rahamimoff
- Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, 91120 Israel.
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25
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Ahn HS, Kim SE, Choi BH, Choi JS, Kim MJ, Rhie DJ, Yoon SH, Jo YH, Kim MS, Sung KW, Kwon OJ, Hahn SJ. Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property. Am J Physiol Cell Physiol 2007; 292:C1714-22. [PMID: 17166943 DOI: 10.1152/ajpcell.00258.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The interaction of FK-506 with KV1.3, stably expressed in Chinese hamster ovary cells, was investigated with the whole cell patch-clamp technique. FK-506 inhibited KV1.3 in a reversible, concentration-dependent manner with an IC50of 5.6 μM. Rapamycin, another immunosuppressant, produced effects that were similar to those of FK-506 (IC50= 6.7 μM). Other calcineurin inhibitors (cypermethrin or calcineurin autoinhibitory peptide) alone had no effect on the amplitude or kinetics of KV1.3. In addition, the inhibitory action of FK-506 continued, even after the inhibition of calcineurin activity. The inhibition produced by FK-506 was voltage dependent, increasing in the voltage range for channel activation. At potentials positive to 0 mV (where maximal conductance is reached), however, no voltage-dependent inhibition was found. FK-506 exhibited a strong use-dependent inhibition of KV1.3. FK-506 shifted the steady-state inactivation curves of KV1.3 in the hyperpolarizing direction in a concentration-dependent manner. The apparent dissociation constant for FK-506 to inhibit KV1.3 in the inactivated state was estimated from the concentration-dependent shift in the steady-state inactivation curve and was calculated to be 0.37 μM. Moreover, the rate of recovery from inactivation of KV1.3 was decreased. In inside-out patches, FK-506 not only reduced the current amplitude but also accelerated the rate of inactivation during depolarization. FK-506 also inhibited KV1.5 and KV4.3 in a concentration-dependent manner with IC50of 4.6 and 53.9 μM, respectively. The present results indicate that FK-506 inhibits KV1.3 directly and that this effect is not mediated via the inhibition of the phosphatase activity of calcineurin.
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Affiliation(s)
- Hye Sook Ahn
- Department of Physiology, Collge of Medicine, Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, Korea
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26
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Rassadi S, Krishnaswamy A, Pié B, McConnell R, Jacob MH, Cooper E. A null mutation for the alpha3 nicotinic acetylcholine (ACh) receptor gene abolishes fast synaptic activity in sympathetic ganglia and reveals that ACh output from developing preganglionic terminals is regulated in an activity-dependent retrograde manner. J Neurosci 2006; 25:8555-66. [PMID: 16162937 PMCID: PMC6725660 DOI: 10.1523/jneurosci.1983-05.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In vertebrates, synaptic activity exerts an important influence on the formation of neural circuits, yet our understanding of its role in directing presynaptic and postsynaptic differentiation during synaptogenesis is incomplete. This study investigates how activity influences synaptic differentiation as synapses mature during early postnatal life. Specifically, we ask what happens to presynaptic terminals when synapses develop without functional postsynaptic receptors and without fast synaptic transmission. To address this issue, we investigated cholinergic nicotinic synapses in sympathetic ganglia of mice with a null mutation for the alpha3 nicotinic ACh receptor gene. Disrupting the alpha3 gene completely eliminates fast excitatory synaptic potentials on postganglionic sympathetic neurons, establishing a crucial role for alpha3-containing postsynaptic receptors in synaptic transmission. Interestingly, the preganglionic nerve terminals form morphologically normal synapses with sympathetic neurons, and these synapses persist without activity in postnatal animals. Surprisingly, when stimulating the preganglionic nerve at physiological rates, we discovered a significant decrease in ACh output from the presynaptic terminals in these alpha3(-/-) sympathetic ganglia. We show that this decrease in ACh output from the presynaptic terminals results, in part, from a lack of functional high-affinity choline transporters. We conclude the following: (1) fast synaptic transmission in mammalian SCG requires alpha3 expression; (2) in the absence of activity, the preganglionic nerve forms synapses that appear morphologically normal and persist for several weeks; and (3) to sustain transmitter release, developing presynaptic terminals require an activity-dependent retrograde signal.
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Affiliation(s)
- Siamak Rassadi
- Department of Physiology, McGill University, Montreal, Quebec, H3G 1Y6, Canada
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27
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Abstract
Cyclophilins (Enzyme Commission (EC) number 5.1.2.8) belong to a group of proteins that have peptidyl-prolyl cis-trans isomerase activity; such proteins are collectively known as immunophilins and also include the FK-506-binding proteins and the parvulins. Cyclophilins are found in all cells of all organisms studied, in both prokaryotes and eukaryotes; humans have a total of 16 cyclophilin proteins, Arabidopsis up to 29 and Saccharomyces 8. The first member of the cyclophilins to be identified in mammals, cyclophilin A, is the major cellular target for, and thus mediates the actions of, the immunosuppressive drug cyclosporin A. Cyclophilin A forms a ternary complex with cyclosporin A and the calcium-calmodulin-activated serine/threonine-specific protein phosphatase calcineurin; formation of this complex prevents calcineurin from regulating cytokine gene transcription. Recent studies have implicated a diverse array of additional cellular functions for cyclophilins, including roles as chaperones and in cell signaling.
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Affiliation(s)
- Ping Wang
- The Research Institute for Children, Children's Hospital, Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA 70118, USA.
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28
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Cheng A, McDonald NA, Connolly CN. Cell surface expression of 5-hydroxytryptamine type 3 receptors is promoted by RIC-3. J Biol Chem 2005; 280:22502-7. [PMID: 15809299 DOI: 10.1074/jbc.m414341200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
RIC-3 has been identified as a molecule essential for the recruitment of functional nicotinic acetylcholine receptors composed of alpha7, but it exhibits inhibitory effects on alpha4beta2 or alpha3beta4 receptors. In this study, we investigated the role of RIC-3 in the recruitment of 5-hydroxytryptamine type 3A (5-HT(3A)) receptors to the cell surface. Although RIC-3 is not essential for the surface transport of 5-HT(3A) receptors, we found that its presence enhances both receptor transport and function in a concentration-dependent manner. RIC-3 is localized to the endoplasmic reticulum, as evidenced by co-localization with the chaperone molecule, binding protein (BiP). RIC-3 is not detected at significant levels on the cell surface when expressed alone or in the presence of 5-HT(3A). RIC-3 and 5-HT(3A) show a low level interaction that is transient (<4 h). That RIC-3 can interact with an endoplasmic reticulum-retained 5-HT(3A) construct, combined with the transient interaction observed and lack of significant surface-expressed RIC-3, suggests that RIC-3 may play a role in 5-HT(3A) receptor folding, assembly, or transport to the cell surface.
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Affiliation(s)
- Aixin Cheng
- Department of Pharmacology & Neuroscience, Ninewells Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
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29
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Nicke A, Thurau H, Sadtler S, Rettinger J, Schmalzing G. Assembly of nicotinic α7 subunits inXenopusoocytes is partially blocked at the tetramer level. FEBS Lett 2004; 575:52-8. [PMID: 15388332 DOI: 10.1016/j.febslet.2004.08.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2004] [Revised: 08/11/2004] [Accepted: 08/12/2004] [Indexed: 10/26/2022]
Abstract
The assembly of nicotinic alpha1beta1gammadelta, alpha3beta4, and alpha7 receptors and 5-hydroxytryptamine 3A (5HT3A) receptors was comparatively evaluated in Xenopus oocytes by blue native PAGE analysis. While alpha1betagammadelta subunits, alpha3beta4 subunits, and 5HT3A subunits combined efficiently to pentamers, alpha7 subunits existed in various assembly states including trimers, tetramers, pentamers, and aggregates. Only alpha7 subunits that completed the assembly process to homopentamers acquired complex-type carbohydrates and appeared at the cell surface. We conclude that Xenopus oocytes have a limited capacity to guide the assembly of alpha7 subunits, but not 5HT3A subunits to homopentamers. Accordingly, ER retention of imperfectly assembled alpha7 subunits rather than inefficient routing of fully assembled alpha7 receptors to the cell surface limits surface expression levels of alpha7 nicotinic acetylcholine receptors.
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MESH Headings
- Animals
- Glycosylation
- Mutagenesis, Site-Directed
- Oocytes/physiology
- Patch-Clamp Techniques
- Polysaccharides/chemistry
- Protein Processing, Post-Translational
- Protein Structure, Quaternary
- Protein Subunits/chemistry
- Protein Subunits/genetics
- Protein Subunits/metabolism
- Rats
- Receptors, Nicotinic/chemistry
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/metabolism
- Receptors, Serotonin, 5-HT3/chemistry
- Receptors, Serotonin, 5-HT3/genetics
- Receptors, Serotonin, 5-HT3/metabolism
- Xenopus laevis
- alpha7 Nicotinic Acetylcholine Receptor
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Affiliation(s)
- Annette Nicke
- Department of Molecular Pharmacology, Medical School of the Technical University of Aachen, Wendlingweg 2, D-52074 Aachen, Germany
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30
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Steinmetz RD, Firla B, Steinhilber D. Inhibition of the functional expression of N-methyl-d-aspartate receptors in a stably transformed cell line by cyclosporin A. Biochem Pharmacol 2004; 68:563-71. [PMID: 15242822 DOI: 10.1016/j.bcp.2004.04.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 04/23/2004] [Indexed: 11/27/2022]
Abstract
The L(tk-) cell line L12-G10 stably transformed with the human N-methyl-D-aspartate (NMDA) receptor subunits NR1-1a/NR2A showed a Ca(2+)-dependent increase in cell death, loss of mitochondrial membrane potential, and ATP depletion after agonist stimulation. Treatment of the cells with cyclosporine A (CsA) for 4h reduced glutamate-induced cell death by 60% (IC(50) of 7.1microM). The immunophilin binding drug FK506 was not effective. Short preincubation with CsA for 10 min already decreased the glutamate-induced loss of mitochondrial membrane potential while the NMDA receptor function is not affected. However, pretreatment of the cells with CsA (30 microM) for 6h reduced membrane associated NR1-1a protein amount by approximately 85%, whereas mRNA expression remained unaffected. These results suggest, that the cytoprotective effect of CsA in L12-G10 cells is due to the inhibition of the permeability transition pore on the one hand and to the inhibition of the expression of functional NMDA receptors by an additional posttranscriptional mechanism on the other hand.
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Affiliation(s)
- Ralf Dirk Steinmetz
- Institute for Pharmaceutical Chemistry, University of Frankfurt, Marie-Curie-Strasse 9, D-60439 Frankfurt am Main, Germany
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31
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Arckens L, Van der Gucht E, Van den Bergh G, Massie A, Leysen I, Vandenbussche E, Eysel UT, Huybrechts R, Vandesande F. Differential display implicates cyclophilin A in adult cortical plasticity. Eur J Neurosci 2003; 18:61-75. [PMID: 12859338 DOI: 10.1046/j.1460-9568.2003.02726.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Removal of retinal input from a restricted region of adult cat visual cortex leads to a substantial reorganization of the retinotopy within the sensory-deprived cortical zone. Little is known about the molecular mechanisms underlying this reorganization. We used differential mRNA display (DDRT-PCR) to compare gene expression patterns between normal control and reorganizing visual cortex (area 17-18), 3 days after induction of central retinal lesions. Systematic screening revealed a decrease in the mRNA encoding cyclophilin A in lesion-affected cortex. In situ hybridization and competitive PCR confirmed the decreased cyclophilin A mRNA levels in reorganizing cortex and extended this finding to longer postlesion survival times as well. Western blotting and immunocytochemistry extended these data to the protein level. In situ hybridization and immunocytochemistry further demonstrated that cyclophilin A mRNA and protein are present in neurons. To exclude the possibility that differences in neuronal activity per se can induce alterations in cyclophilin A mRNA and protein expression, we analyzed cyclophilin A expression in the dorsal lateral geniculate nucleus (dLGN) of retinally lesioned cats and in area 17 and the dLGN of isolated hemisphere cats. In these control experiments cyclophilin A mRNA and protein were distributed as in normal control subjects indicating that the decreased cyclophilin A levels, as observed in sensory-deprived area 17 of retinal lesion cats, are not merely a reflection of changes in neuronal activity. Instead our findings identify cyclophilin A, classically considered a housekeeping gene, as a gene with a brain plasticity-related expression in the central nervous system.
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Affiliation(s)
- Lutgarde Arckens
- Laboratory of Neuroplasticity and Neuroproteomics, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium.
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Schroeder KM, Wu J, Zhao L, Lukas RJ. Regulation by cycloheximide and lowered temperature of cell-surface alpha7-nicotinic acetylcholine receptor expression on transfected SH-EP1 cells. J Neurochem 2003; 85:581-91. [PMID: 12694384 DOI: 10.1046/j.1471-4159.2003.01658.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Heterologous expression of functional, nicotinic acetylcholine receptors (nAChR) in mammalian cells has been difficult to achieve or optimize, even for nAChR containing only one kind of subunit. In this study, we determined effects of lowered temperature or of exposure to the protein synthesis inhibitor cycloheximide (CHX) on cell surface expression of homomeric alpha7-nAChR in transfected SH-EP1 human epithelial cells. We found that incubation of cells for 2 days at 25 degrees C or in the presence of 0.5-2 microg/mL of CHX caused approximately four- or approximately eight-fold increases, respectively, in surface binding sites for 125I-labeled alpha-bungarotoxin (I-Bgt). These increases were accompanied by increases in peak whole-cell current responses to nicotinic agonists. Either treatment lowered protein synthesis and cell proliferation, but experiments using puromycin indicated that a reduction in protein synthesis or cell proliferation per se was not sufficient to increase surface binding. I-Bgt binding to whole-cell membrane pools increased in response to either treatment, suggesting that the increase in surface binding was due, at least in part, to an increase in intracellular receptor levels. The cyclophilin inhibitor cyclosporin A reduced surface expression in untreated as well as CHX- or 25 degrees C-treated cells. The results suggest practical means for increasing cell surface and functional expression of alpha7-nAChR. Although these effects are not simply due to protein synthesis inhibition or reduced cell proliferation, they do involve an increase in intracellular receptor pool size.
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Affiliation(s)
- Katherine M Schroeder
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013, USA
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Tsuneki H, Salas R, Dani JA. Mouse muscle denervation increases expression of an alpha7 nicotinic receptor with unusual pharmacology. J Physiol 2003; 547:169-79. [PMID: 12562921 PMCID: PMC2342616 DOI: 10.1113/jphysiol.2002.036368] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Neuronal nicotinic alpha7 subunits have been found in chick and rat skeletal muscle during development and denervation. In the present study, reverse transcriptase-polymerase chain reaction was used to detect alpha7 subunit mRNA in denervated mouse muscle. To determine whether the alpha7 subunit forms functional nicotinic acetylcholine receptors (nAChRs) in muscle, choline was used to induce a membrane depolarization because choline has been considered a specific agonist of alpha7-containing (alpha7*) nAChRs. We found, however, that choline (3-10 mM) also weakly activates muscle nAChRs. After inhibiting muscle nAChRs with a specific muscle nAChR inhibitor, alpha-conotoxin GI (alphaCTxGI), choline was used to activate the alpha7* nAChRs on muscle selectively. Four weeks after denervation, rapid application of choline (10 mM) elicited a substantial depolarization in the presence of alphaCTxGI (0.1 microM). This component of the depolarization was never present in denervated muscles obtained from mutant mice lacking the alpha7 subunit (i.e. alpha7-null mice). The depolarization component that is resistant to alphaCTxGI was antagonized by pancuronium (3-10 microM) and by a 4-oxystilbene derivative (F3, 0.1-0.5 microM) at concentrations considered highly specific for alpha7* nAChRs. Another selective alpha7 antagonist, methyllycaconitine (0.05-5 microM), did not strongly inhibit this choline-induced depolarization. Furthermore, the choline-sensitive nAChRs showed little desensitization over 10 s of application with choline (10-30 mM). These results indicate that functional alpha7* nAChRs are significantly present on denervated muscle, and that these receptors display unusual functional and pharmacological characteristics.
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Affiliation(s)
- Hiroshi Tsuneki
- Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030-3498, USA
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34
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Wang N, Orr-Urtreger A, Korczyn AD. The role of neuronal nicotinic acetylcholine receptor subunits in autonomic ganglia: lessons from knockout mice. Prog Neurobiol 2002; 68:341-60. [PMID: 12531234 DOI: 10.1016/s0301-0082(02)00106-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChR), composed of 12 subunits (alpha2-alpha10, beta2-beta4), are expressed in autonomic ganglia, playing a central role in autonomic transmission. The repertoire of nicotinic subunits in autonomic ganglia includes alpha3, alpha5, alpha7, beta2 and beta4 subunits. In the last 10 years, heterologous expression studies have revealed much about the nature of neuronal nAChRs. However, there is only limited understanding of subunit actions in autonomic system. Functional deletions of subunit by gene knockout in animals could overcome these limitations. We review recent studies on nAChRs on autonomic ganglia for physiological and pharmacological properties and potential locations of the subunits.
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Affiliation(s)
- Ningshan Wang
- Department of Physiology and Pharmacology, Sackler Medical School, Tel Aviv University, Ramat Aviv, Israel
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35
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Guermonprez L, O'Regan S, Meunier FM, Morot-Gaudry-Talarmain Y. The neuronal choline transporter CHT1 is regulated by immunosuppressor-sensitive pathways. J Neurochem 2002; 82:874-84. [PMID: 12358793 DOI: 10.1046/j.1471-4159.2002.01044.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The immunosuppressor cyclosporin A inhibits the peptidyl-prolyl-cis/trans-isomerase activity of cyclophilins and the resulting complex inhibits the phosphatase activity of calcineurin. Both enzymes were detected in peripheral nerve endings isolated from the electric organ of Torpedo and shown to be affected by 10 micro m cyclosporin A. Among the cholinergic properties studied, choline uptake was specifically inhibited by cyclosporin A to a maximum of 40%. Cyclosporin A decreased the rate of choline transport but not the binding of the non-transportable choline analogue hemicholinium-3, indicating that the number of membrane transporters was not affected. Through the use of two other immunosuppressors, FK506, which also inhibits calcineurin, and rapamycin, which does not, two different mechanisms of choline uptake inhibition were uncovered. FK506 inhibited the rate of choline transport, whereas rapamycin diminished the affinity for choline. The Torpedo homologue of the high affinity choline transporter CHT1 was cloned and its activity was reconstituted in Xenopus oocytes. Choline uptake by oocytes expressing tCHT1 was inhibited by all three immunosuppressors and also by microinjection of the specific calcineurin autoinhibitory domain A457-481, indicating that the phosphatase calcineurin regulates CHT1 activity and could be the common target of cyclosporin and FK506. Rapamycin, which changed the affinity of the transporter, may have acted through an immunophilin on the isomerization of critical prolines that are found in the tCHT1 sequence.
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Affiliation(s)
- Lydie Guermonprez
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, Gif-sur-Yvette, France.
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Kimchi-Sarfaty C, Kasir J, Ambudkar SV, Rahamimoff H. Transport activity and surface expression of the Na+-Ca2+ exchanger NCX1 are inhibited by the immunosuppressive agent cyclosporin A and by the nonimmunosuppressive agent PSC833. J Biol Chem 2002; 277:2505-10. [PMID: 11700317 DOI: 10.1074/jbc.m109154200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyclosporin A (CsA) treatment of HEK 293 cells expressing the rat heart RHE-1 (NCX1.1, EMBL accession number ) or the rat brain RBE-2 (NCX1.5, GenBank(TM) accession number ) Na(+)-Ca(2+) exchanger inhibited their transport activity in a concentration-dependent manner. The inhibition was detectable at 2 microm CsA, and exposure of the cells to 20 microm CsA resulted in a decrease of the Na(+)-dependent Ca(2+) uptake to about 20% relative to that of untreated cells. Determination of the surface expression of the exchanger protein revealed a parallel concentration-dependent reduction in the amount of the immunoreactive protein. No reduction was detected in the amount of total immunoreactive exchanger protein in CsA-treated cells relative to untreated ones. Among the different drugs tested, only PSC833, an analog of cyclosporin D, mimicked the effects of CsA. Exposure of the transfected cells to the chemically related cyclosporin D and macrolide drugs (FK506 or rapamycin) had no effect on the transport activity or the surface expression of the Na(+)-Ca(2+) exchanger. Co-expression of the human multidrug transporter P-glycoprotein (of which both drugs are modulators) with the cloned Na(+)-Ca(2+) exchanger revealed that transport activity and surface expression of each transporter in the co-transfected system were similar to those of each transporter alone in both the presence and absence of CsA or PSC833. CsA and PSC833 inhibited the surface expression of the NCX1 protein but did not alter the surface expression of P-glycoprotein. Unlike some P-glycoprotein endoplasmic reticulum-retained mutants (Loo, T. W., and Clarke, D. M. (1997) J. Biol. Chem. 272, 709-712), CsA did not rescue RBE-2/F913-->Stop, an endoplasmic reticulum-retained function-competent mutant of the Na(+)-Ca(2+) exchanger (Kasir, J., Ren, X., Furman, I., and Rahamimoff, H. (1999) J. Biol. Chem. 274, 24873-24880) and did not induce its kinesis to the surface membrane, further demonstrating molecular differences between P-glycoprotein and NCX1 mutants for interaction with CsA.
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Affiliation(s)
- Chava Kimchi-Sarfaty
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA
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Deane CM, Lummis SC. The role and predicted propensity of conserved proline residues in the 5-HT3 receptor. J Biol Chem 2001; 276:37962-6. [PMID: 11495906 DOI: 10.1074/jbc.m104569200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
5-HT3 receptors possess a number of highly conserved proline residues. We changed each of these to alanine, expressed the mutants as homomeric 5-HT3A receptors in HEK293 cells, and analyzed them with radioligand binding, electrophysiology, and immunocytochemistry. Mutation of Pro56, Pro104, Pro123, and Pro170 resulted in ablation of radioligand binding, whereas mutation of Pro257 and Pro301 did not. Only the latter were expressed at the plasma membrane but were non-functional. Thus the former, which are in the N-terminal domain, may be involved in forming correct receptor structure, while those in the transmembrane region (Pro257 and Pro301) are necessary for the function of the protein. To explore the conformational preference (propensity) of these residues we examined the proportion of cis-prolines and the influence of adjacent residues in known protein structures. 4.7% of prolines in the protein data base were in the cis conformation, and the distribution of amino acids adjacent to cis-prolines was not randomly distributed. Comparison of the proportion of each amino acid residue adjacent to a cis-proline revealed that aromatic and bend-facilitating residues were favored while those with beta-branched chains were not. Thus five residues (Gly, Pro, Tyr, Trp, Phe) and three residues (Pro, Tyr, Phe) were found more frequently than expected before and after cis-prolines respectively, whereas five residues (Val, Ile, Leu, Asp, Thr) and two residues (Asp, Glu) were found less frequently. Of the 20 proline residues in the 5-HT3A receptor subunit only Pro170 has adjacent residues that are favorable. Mutating these to non-favorable residues resulted in ablation of ligand binding, whereas replacement with alternative favorable residues did not. We therefore propose that Pro170, which is part of the characteristic cys-loop found in this family of proteins, may be in the cis conformation.
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Affiliation(s)
- C M Deane
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA United Kingdom
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38
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Guo X, Dillman JF, Dawson VL, Dawson TM. Neuroimmunophilins: novel neuroprotective and neuroregenerative targets. Ann Neurol 2001; 50:6-16. [PMID: 11456311 DOI: 10.1002/ana.1030] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cyclosporin A (CsA) and FK506 (tacrolimus) are immunosuppresants that are widely used in organ transplantation. CsA is an 11-member cyclic peptide, whereas FK506 is a macrolide antibiotic. Recently, these powerful and useful compounds have become of great interest to neuroscientists for their unique neuroprotective and neuroregenerative effects. These drugs and nonimmunosuppressive analogs protect neurons from the effects of glutamate excitotoxicity, focal ischemia, and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic cell death. They also stimulate functional recovery of neurons in a variety of neurologic injury paradigms. These drugs exert their effects via immunophilins, the protein receptors for these agents. The immunophilin ligands show particular promise as a novel class of neuroprotective and neuroregenerative agents that have the potential to treat a variety of neurologic disorders.
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Affiliation(s)
- X Guo
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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39
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Cottet-Maire F, Avdonin PV, Roulet E, Buetler TM, Mermod N, Ruegg UT. Upregulation of vasopressin V1A receptor mRNA and protein in vascular smooth muscle cells following cyclosporin A treatment. Br J Pharmacol 2001; 132:909-17. [PMID: 11181432 PMCID: PMC1572618 DOI: 10.1038/sj.bjp.0703878] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The major side effects of the immunosuppressive drug cyclosporin A (CsA) are hypertension and nephrotoxicity. It is likely that both are caused by local vasoconstriction. 2. We have shown previously that 20 h treatment of rat vascular smooth muscle cells (VSMC) with therapeutically relevant CsA concentrations increased the cellular response to [Arg8]vasopressin (AVP) by increasing about 2 fold the number of vasopressin receptors. 3. Displacement experiments using a specific antagonist of the vasopressin V1A receptor (V1AR) showed that the vasopressin binding sites present in VSMC were exclusively receptors of the V1A subtype. 4. Receptor internalization studies revealed that CsA (10(-6) M) did not significantly alter AVP receptor trafficking. 5. V1AR mRNA was increased by CsA, as measured by quantitative polymerase chain reaction. Time-course studies indicated that the increase in mRNA preceded cell surface expression of the receptor, as measured by hormone binding. 6. A direct effect of CsA on the V1AR promoter was investigated using VSMC transfected with a V1AR promoter-luciferase reporter construct. Surprisingly, CsA did not increase, but rather slightly reduced V1AR promoter activity. This effect was independent of the cyclophilin-calcineurin pathway. 7. Measurement of V1AR mRNA decay in the presence of the transcription inhibitor actinomycin D revealed that CsA increased the half-life of V1AR mRNA about 2 fold. 8. In conclusion, CsA increased the response of VSMC to AVP by upregulating V1AR expression through stabilization of its mRNA. This could be a key mechanism in enhanced vascular responsiveness induced by CsA, causing both hypertension and, via renal vasoconstriction, reduced glomerular filtration.
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MESH Headings
- Animals
- Arginine Vasopressin/metabolism
- Cells, Cultured
- Cyclosporine/pharmacology
- Heterogeneous Nuclear Ribonucleoprotein D0
- Heterogeneous-Nuclear Ribonucleoprotein D
- Immunosuppressive Agents/pharmacology
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- RNA, Messenger/analysis
- RNA-Binding Proteins/physiology
- Rats
- Rats, Inbred WKY
- Receptors, Vasopressin/biosynthesis
- Receptors, Vasopressin/drug effects
- Receptors, Vasopressin/genetics
- Up-Regulation
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Affiliation(s)
- Florence Cottet-Maire
- Pharmacology Group, School of Pharmacy, University of Lausanne, BEP, 1015 Lausanne, Switzerland
| | - Pavel V Avdonin
- Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Emmanuelle Roulet
- Laboratory of Molecular Biotechnology, Centre of Biotechnology UNIL-EPFL, University of Lausanne, 1015 Lausanne, Switzerland
- Institute of Animal Biology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Timo M Buetler
- Pharmacology Group, School of Pharmacy, University of Lausanne, BEP, 1015 Lausanne, Switzerland
| | - Nicolas Mermod
- Laboratory of Molecular Biotechnology, Centre of Biotechnology UNIL-EPFL, University of Lausanne, 1015 Lausanne, Switzerland
- Institute of Animal Biology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Urs T Ruegg
- Pharmacology Group, School of Pharmacy, University of Lausanne, BEP, 1015 Lausanne, Switzerland
- Author for correspondence:
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40
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Tran TT, Dai W, Sarkar HK. Cyclosporin A inhibits creatine uptake by altering surface expression of the creatine transporter. J Biol Chem 2000; 275:35708-14. [PMID: 10964923 DOI: 10.1074/jbc.m005636200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The immunosuppressive drug cyclosporin A (CsA) inhibited the hCRT-1 cDNA-induced creatine uptake in Xenopus oocytes and the endogenous creatine uptake in cultured C(2)C(12) muscle cells in a dose- and time-dependent manner. FK506, another potent immunosuppressant, was unable to mimic the effect of CsA suggesting that the inhibitory effect of CsA was specific. To delineate the mechanism underlying, we investigated the effect of CsA on the K(m) and V(max) of creatine transport and also on the cell surface distribution of the creatine transporter. Although CsA treatment did not affect the K(m) (20-24 microm) for creatine, it significantly decreased the V(max) of creatine uptake in both oocytes and muscle cells. CsA treatment reduced the cell surface expression level of the creatine transporter in the muscle cells by approximately 60% without significantly altering its total expression level, and the reduction in the cell surface expression paralleled the decrease in creatine uptake. Taken together, our results suggest that CsA inhibited creatine uptake by altering the surface abundance of the creatine transporter. We propose that CsA impairs the targeting of the creatine transporter by inhibiting the function of an associated cyclophilin, resulting in an apparent loss in surface expression of the creatine transporter. Our results also suggest that prolonged exposure to CsA may result in chronically creatine-depleted muscle, which may be a cause for the development of CsA-associated clinical myopathies in organ transplant patients.
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Affiliation(s)
- T T Tran
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA
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41
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Shiraishi S, Yokoo H, Kobayashi H, Yanagita T, Uezono Y, Minami S, Takasaki M, Wada A. Post-translational reduction of cell surface expression of insulin receptors by cyclosporin A, FK506 and rapamycin in bovine adrenal chromaffin cells. Neurosci Lett 2000; 293:211-5. [PMID: 11036198 DOI: 10.1016/s0304-3940(00)01513-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Long-term (>/=3 h) treatment of cultured bovine adrenal chromaffin cells with cyclosporin A (CsA) decreased cell surface (125)I-insulin binding by 62% in a concentration (IC(50)=18 microM)- and time (t(1/2)=16 h)-dependent manner, but did not change the K(d) value. FK506 (1 microM) or rapamycin (3 microM) treatment reduced (125)I-insulin binding. Western blot analysis showed that CsA treatment decreased insulin receptor (IR) beta-subunit level (t(1/2)=15 h) in membrane fraction, but did not alter total cellular levels of IR precursor and IR beta-subunit. Internalization rate of cell surface IR measured by using brefeldin A, an inhibitor of vesicular exit from the trans-Golgi network, was comparable between non-treated and CsA-treated cells. Thus, CsA, FK506 and rapamycin inhibit peptidyl prolyl cis-trans isomerase activities of cyclophilin and FK506-binding protein, and down-regulate IR presumably by reducing cell surface externalization of IR.
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Affiliation(s)
- S Shiraishi
- Department of Pharmacology, Miyazaki Medical College, Kiyotake, 889-1692, Miyazaki, Japan
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42
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Costantini LC, Isacson O. Immunophilin ligands and GDNF enhance neurite branching or elongation from developing dopamine neurons in culture. Exp Neurol 2000; 164:60-70. [PMID: 10877916 DOI: 10.1006/exnr.2000.7417] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurotrophic effects of immunophilin ligands have been shown in animal models of peripheral and central nervous system insult. To investigate the specific growth-promoting effects of these compounds, we examined the effects of various immunophilin ligands on primary dopamine (DA) neurons in culture and compared these with a well-known DA trophic factor, glial cell line-derived neurotrophic factor (GDNF). In neuronal cultures from Embryonic Day 14 ventral mesencephalon, enhanced elongation of DA neurites was observed with immunophilin ligands, which inhibited the phosphatase activity of calcineurin (FK506 and cyclosporin A) when compared to vehicle-treated cultures. This elongation was also observed with GDNF, known to exert its trophic effects through phosphorylation-dependent pathways. In contrast, immunophilin ligands that do not inhibit calcineurin (rapamycin and V-10,367) increased branching of DA neurites, suggesting that elongation is dependent upon maintained phosphorylation while branching is not. In addition, both V-10,367 and rapamycin antagonized the elongation effects of FK506 and induced branching. The antagonism of elongation (and reappearance of branching) illustrates the intrinsic abilities of developing DA neurons to either elongate or branch, but not both. We show that the immunophilin FKBP12 (12-kDa FK506-binding protein) is expressed in ventral mesencephalic neuronal cultures and colocalizes with DA neurons. This work elucidates the specific growth-promoting effects by which GDNF and immunophilin ligands modify developmental growth processes of DA neurons, via their interactions with intracellular targets.
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Affiliation(s)
- L C Costantini
- Neuroregeneration Laboratory, Program in Neuroscience Harvard Medical School, McLean Hospital, Belmont, MA 02478, USA
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43
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Cuevas J, Roth AL, Berg DK. Two distinct classes of functional 7-containing nicotinic receptor on rat superior cervical ganglion neurons. J Physiol 2000; 525 Pt 3:735-46. [PMID: 10856125 PMCID: PMC2269972 DOI: 10.1111/j.1469-7793.2000.t01-1-00735.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) that bind alpha-bungarotoxin (alpha Bgt) were studied on isolated rat superior cervical ganglion (SCG) neurons using whole-cell patch clamp recording techniques. Rapid application of ACh onto the soma of voltage clamped neurons evoked a slowly desensitizing current that was reversibly blocked by alpha Bgt (50 nM). The toxin-sensitive current constituted on average about half of the peak whole-cell response evoked by ACh. Nanomolar concentrations of methyllycaconitine blocked the alpha Bgt-sensitive component of the ACh-evoked current as did intracellular dialysis with an anti-alpha 7 monoclonal antibody. The results indicate that the slowly reversible toxin-sensitive response elicited by ACh arises from activation of an unusual class of alpha 7-containing receptor (alpha 7-nAChR) similar to that reported previously for rat intracardiac ganglion neurons. A second class of functional alpha 7-nAChR was identified on some SCG neurons by using rapid application of choline to elicit responses. In these cases a biphasic response was obtained, which included a rapidly desensitizing component that was blocked by alpha Bgt in a pseudo-irreversible manner. The pharmacology and kinetics of the responses resembled those previously attributed to alpha 7-nAChRs in a number of other neuronal cell types. Experiments measuring the dissociation rate of 125I-labelled alpha Bgt from SCG neurons revealed two classes of toxin-binding site. The times for toxin dissociation were consistent with those required to reverse blockade of the two kinds of alpha Bgt-sensitive response. These results indicate that rat SCG neurons express two types of functional alpha 7-nAChR, differing in pharmacology, desensitization and reversibility of alpha Bgt blockade.
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Affiliation(s)
- J Cuevas
- Department of Pharmacology and Therapeutics, University of South Florida College of Medicine, Tampa, FL 33612-4799, USA
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44
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Sweileh W, Wenberg K, Xu J, Forsayeth J, Hardy S, Loring RH. Multistep expression and assembly of neuronal nicotinic receptors is both host-cell- and receptor-subtype-dependent. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 75:293-302. [PMID: 10686351 DOI: 10.1016/s0169-328x(99)00302-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We tested the hypothesis that the folding, assembly and insertion of neuronal nicotinic receptors are critically dependent on the host cell line. We used recombinant adenoviruses encoding either the rat alpha7, alpha4 or beta2 subunits in which expression of the subunit is controlled by a tetracycline-dependent promoter to screen five cell lines (GH4C1, SH-EP1, CV1, SN-56, and CHO-CAR). All five lines do not express detectable nicotinic receptor but do express receptor for human adenovirus, and all expressed mRNA for alpha7, alpha4 and beta2 subunits when infected with viruses. Each cell line expressed varying levels of alpha4beta2 receptors that bound [3H]cytisine, but only the GH4C1 and SH-EP1 cell lines expressed either surface or internal alpha7 receptors that bound [125I]alpha-bungarotoxin ([125I]alpha-BGT). All five cell lines expressed a 60 kDa protein immunoblotted by anti-alpha7 antibodies when infected with the alpha7 virus, presumably representing unassembled alpha7 subunits. In addition, GH4C1 cells expressed over 10-fold more surface alpha7 receptor than SH-EP1 cells, even though the total alpha7 receptor in the two cell lines was similar. Sedimentation experiments indicate that SH-EP1 cells only partially assemble alpha7 receptors compared with GH4C1 cells and control alpha7 from rat brain. These data suggest that not only is surface alpha7 receptor expression a multistep process, but that each step may involve cell-specific assembly factors.
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Affiliation(s)
- W Sweileh
- Department of Pharmaceutical Sciences, 211 Mugar, Northeastern University, 360 Huntington Avenue, Boston, MA, USA
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45
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Lyford LK, Rosenberg RL. Cell-free expression and functional reconstitution of homo-oligomeric alpha7 nicotinic acetylcholine receptors into planar lipid bilayers. J Biol Chem 1999; 274:25675-81. [PMID: 10464304 DOI: 10.1074/jbc.274.36.25675] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alpha7 nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel that modulates neurotransmitter release in the central nervous system. We show here that functional, homo-oligomeric alpha7 nAChRs can be synthesized in vitro with a rabbit reticulocyte lysate translation system supplemented with endoplasmic reticulum microsomes, reconstituted into planar lipid bilayers, and evaluated using single-channel recording techniques. Because wild-type alpha7 nAChRs desensitize rapidly, we used a nondesensitizing form of the alpha7 receptor with mutations in the second transmembrane domain (S2'T and L9'T) to record channel activity in the continuous presence of agonist. Endoglycosidase H treatment of microsomes containing nascent alpha7 S2'T/L9'T nAChRs indicated that the receptors were glycosylated. A proteinase K protection assay revealed a 36-kDa fragment in the ER lumen, consistent with a large extracellular domain predicted by most topological models, indicating that the protein was folded integrally through the ER membrane. alpha7 S2'T/L9'T receptors reconstituted into planar lipid bilayers had a unitary conductance of approximately 50 pS, were highly selective for monovalent cations over Cl(-), were nonselective between K(+) and Na(+), and were blocked by alpha-bungarotoxin. This is the first demonstration that a functional ligand-gated ion channel can be synthesized using an in vitro expression system.
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Affiliation(s)
- L K Lyford
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7365, USA
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46
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Abstract
Changes in the intracellular calcium concentration ([Ca2+]i) convey signals that are essential to the life and death of neurons. Ca(2+)-induced Ca(2+)-release (CICR), a process in which a modest elevation in [Ca2+]i is amplified by a secondary release of Ca2+ from stores within the cell, plays a prominent role in shaping neuronal [Ca2+]i signals. When CICR becomes regenerative, an explosive increase in [Ca2+]i generates a Ca2+ wave that spreads throughout the cell. A discrete threshold controls activation of this all-or-none behavior and cellular context adjusts the threshold. Thus, the store acts as a switch that determines whether a given pattern of electrical activity will produce a local or global Ca2+ signal. This gatekeeper function seems to control some forms of Ca(2+)-triggered plasticity in neurons.
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Affiliation(s)
- Y M Usachev
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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47
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Fischer U, Reinhardt S, Albuquerque EX, Maelicke A. Expression of functional alpha7 nicotinic acetylcholine receptor during mammalian muscle development and denervation. Eur J Neurosci 1999; 11:2856-64. [PMID: 10457182 DOI: 10.1046/j.1460-9568.1999.00703.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have studied, on the transcriptional, protein and functional level, the expression of alpha7 nicotinic acetylcholine receptors (nAChR) in the course of rat muscle development, denervation and renervation. At foetal day 13, alpha7 nAChR expression was observed in somites and developing muscles of the back, but not yet in migrating myoblasts. Two days later, concomitant with myoblast aggregation, the alpha7 isoform began to be expressed in isolated myoblasts, with the highest level of expression in the frontal zone of the migrating wave. On foetal day 18, a time when the myoblasts in the upper hindleg have fused, alpha7 nAChR expression was most prominent in the outer layer of muscle tissue. The highest level of expression was observed in the first postnatal week, when practically all muscle cells stained positively for alpha7 protein. During the following weeks, alpha7 nAChR expression slowly decreased and practically disappeared in adult hindleg muscle. Following chronic denervation of adult Soleus muscle fibres, expression of alpha7 nAChR returned within 2-4 weeks. Electrophysiological measurements showed that the alpha7 nAChR of chronically denervated soleus muscle fibres were functional and, in particular, that they could be activated by choline. The presence of the alpha7 nAChR in developing and denervated muscle suggests a role for this nicotinic receptor in neuronal pathfinding and/or endplate stabilization.
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Affiliation(s)
- U Fischer
- Laboratory of Molecular Neurobiology, Institute of Physiological Chemistry and Pathobiochemistry, Johannes-Gutenberg University Medical School, Mainz, Germany
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48
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Rakhilin S, Drisdel RC, Sagher D, McGehee DS, Vallejo Y, Green WN. alpha-bungarotoxin receptors contain alpha7 subunits in two different disulfide-bonded conformations. J Cell Biol 1999; 146:203-18. [PMID: 10402471 PMCID: PMC2199736 DOI: 10.1083/jcb.146.1.203] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Neuronal nicotinic alpha7 subunits assemble into cell-surface complexes that neither function nor bind alpha-bungarotoxin when expressed in tsA201 cells. Functional alpha-bungarotoxin receptors are expressed if the membrane-spanning and cytoplasmic domains of the alpha7 subunit are replaced by the homologous regions of the serotonin-3 receptor subunit. Bgt-binding surface receptors assembled from chimeric alpha7/serotonin-3 subunits contain subunits in two different conformations as shown by differences in redox state and other features of the subunits. In contrast, alpha7 subunit complexes in the same cell line contain subunits in a single conformation. The appearance of a second alpha7/serotonin-3 subunit conformation coincides with the formation of alpha-bungarotoxin-binding sites and intrasubunit disulfide bonding, apparently within the alpha7 domain of the alpha7/serotonin-3 chimera. In cell lines of neuronal origin that produce functional alpha7 receptors, alpha7 subunits undergo a conformational change similar to alpha7/serotonin-3 subunits. alpha7 subunits, thus, can fold and assemble by two different pathways. Subunits in a single conformation assemble into nonfunctional receptors, or subunits expressed in specialized cells undergo additional processing to produce functional, alpha-bungarotoxin-binding receptors with two alpha7 conformations. Our results suggest that alpha7 subunit diversity can be achieved postranslationally and is required for functional homomeric receptors.
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MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Bungarotoxins/metabolism
- Cell Line
- Chickens
- Disulfides/chemistry
- Disulfides/metabolism
- Ethylmaleimide/pharmacology
- Humans
- Membrane Proteins/biosynthesis
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Nicotine/pharmacology
- Oxidation-Reduction
- Patch-Clamp Techniques
- Protein Conformation/drug effects
- Protein Folding
- Protein Processing, Post-Translational
- Receptors, Nicotinic/biosynthesis
- Receptors, Nicotinic/chemistry
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/metabolism
- Receptors, Serotonin/biosynthesis
- Receptors, Serotonin/chemistry
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Receptors, Serotonin, 5-HT3
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/metabolism
- Transfection
- alpha7 Nicotinic Acetylcholine Receptor
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Affiliation(s)
| | | | | | - Daniel S. McGehee
- Department of Pharmacological and Physiological Sciences, Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois 60637
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49
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Abstract
A combination of mutagenesis, computer modeling and immunoreactivity has been used to develop a structural model of a segment of the glutamate receptor (GluR), termed GluR3B, which is bound by receptor-activating autoantibodies. In this model, the GluR3B epitope is located in a reverse hairpin loop that places key residues important for antibody recognition and receptor activation in a linear arrangement on the solvent-exposed surface. The conformation of the loop is stabilized by a hydrophobic core which is critical for functional integrity of the epitope. The proximity of the amino- and carboxy-terminal residues suggested that the GluR3B peptide could be cyclized without diminishing immunoreactivity through replacement of these residues with cysteines and formation of a disulfide bond. This prediction was confirmed experimentally since the cyclized peptide retained full immunoreactivity. The model provides insight into GluR subunit-specific functional diversity and the role of autoantibodies to this region in neurological disease.
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Affiliation(s)
- S McDonald
- The Burnham Institute, La Jolla CA 92037, USA
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50
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Mammalian nicotinic receptors with alpha7 subunits that slowly desensitize and rapidly recover from alpha-bungarotoxin blockade. J Neurosci 1999. [PMID: 9852571 DOI: 10.1523/jneurosci.18-24-10335.1998] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One of the most abundant nicotinic receptors in the nervous system is a species that contains the alpha7 gene product, rapidly desensitizes, and binds alpha-bungarotoxin with great affinity. The receptor has a high relative permeability to calcium and performs a variety of functions including presynaptic modulation of transmitter release and postsynaptic generation of synaptic currents. Fast excitatory transmission in mammalian intracardiac ganglia is mediated primarily by nicotinic receptors, and although intracardiac ganglion neurons express the alpha7 gene, no toxin-sensitive response has been detected previously in them. We report here that whole-cell patch-clamp recordings from freshly dissociated intracardiac ganglion neurons reveal a nicotinic response that desensitizes slowly and is blocked by alpha-bungarotoxin in a rapidly reversible manner. The only rat gene previously thought capable of forming such receptors was alpha9, but no evidence suggests that the alpha9 gene is expressed in neurons. We find that reverse transcription (RT)-PCR detects alpha7 but not alpha9 mRNA in the ganglia. In addition, the pharmacology of the nicotinic response is typical of alpha7-containing receptors but differs in several respects from that expected for alpha9. Binding experiments with immunotethered receptors identifies a ganglionic species that contains the alpha7 gene product. Moreover, intracellular perfusion of the cells with an anti-alpha7 monoclonal antibody specifically reduces the amplitude of the toxin-sensitive response. The results indicate that alpha7-containing receptors are responsible for the slowly desensitizing, toxin-reversible response and suggest that the receptors are modified in cell-specific ways to influence their functional properties.
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