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Gotti C, Clementi F, Zoli M. Auxiliary protein and chaperone regulation of neuronal nicotinic receptor subtype expression and function. Pharmacol Res 2024; 200:107067. [PMID: 38218358 DOI: 10.1016/j.phrs.2024.107067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 01/06/2024] [Accepted: 01/08/2024] [Indexed: 01/15/2024]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) are a family of pentameric, ligand-gated ion channels that are located on the surface of neurons and non-neuronal cells and have multiple physiological and pathophysiological functions. In order to reach the cell surface, many nAChR subtypes require the help of chaperone and/or auxiliary/accessory proteins for their assembly, trafficking, pharmacological modulation, and normal functioning in vivo. The use of powerful genome-wide cDNA screening has led to the identification and characterisation of the molecules and mechanisms that participate in the assembly and trafficking of receptor subtypes, including chaperone and auxiliary or accessory proteins. The aim of this review is to describe the latest findings concerning nAChR chaperones and auxiliary proteins and pharmacological chaperones, and how some of them control receptor biogenesis or regulate channel activation and pharmacology. Some auxiliary proteins are subtype selective, some regulate various subtypes, and some not only modulate nAChRs but also target other receptors and signalling pathways. We also discuss how changes in auxiliary proteins may be involved in nAChR dysfunctions.
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Affiliation(s)
- Cecilia Gotti
- CNR, Institute of Neuroscience, Milan, Italy; NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Italy.
| | - Francesco Clementi
- CNR, Institute of Neuroscience, Milan, Italy; Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy
| | - Michele Zoli
- Department of Biomedical, Metabolic and Neural Sciences, Center for Neuroscience and Neurotechnology (CfNN), University of Modena and Reggio Emilia, Modena, Italy
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Lee SS, Chang Y, Rigotti NA, Singer DE, Levy DE, Tyndale RF, Davis EM, Freiberg MS, King S, Wells QS, Tindle HA. Can Treatment Support Mitigate Nicotine Metabolism-Based Disparities in Smoking Abstinence? Secondary Analysis of the Helping HAND 4 Trial. Nicotine Tob Res 2023; 25:1575-1584. [PMID: 37209421 PMCID: PMC10439488 DOI: 10.1093/ntr/ntad079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 04/23/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
INTRODUCTION The nicotine metabolite ratio (NMR), a biomarker of CYP2A6-mediated nicotine metabolism, predicts the efficacy of nicotine replacement therapy (NRT), with fast metabolizers benefiting less than slow metabolizers. Whether treatment support to optimize NRT use (henceforth "treatment support") modifies this pharmacogenetic relationship is unknown. METHODS Hospitalized adult daily smokers were assigned to one of two post-discharge smoking cessation interventions offering NRT and counseling: (1) Transitional Tobacco Care Management, which delivered enhanced treatment support via free combination NRT at discharge and automated counseling, and (2) a quitline-based approach representing usual care (UC). The primary outcome was biochemically verified 7-day point prevalence abstinence 6 months after discharge. Secondary outcomes were the use of NRT and counseling during the 3-month intervention period. Logistic regression models tested for interactions between NMR and intervention, controlling for sex, race, alcohol use, and BMI. RESULTS Participants (N = 321) were classified as slow (n = 80) or fast (n = 241) metabolizers relative to the first quartile of NMR (0.012-0.219 vs. 0.221-3.455, respectively). Under UC, fast (vs. slow) metabolizers had lower odds of abstinence at 6 months (aOR 0.35, 95% CI 0.13-0.95) and similar odds of NRT and counseling use. Compared to UC, enhanced treatment support increased abstinence (aOR 2.13, 95% CI 0.98-4.64) and use of combination NRT (aOR 4.62, 95% CI 2.57-8.31) in fast metabolizers, while reducing abstinence in slow metabolizers (aOR 0.21, 95% CI 0.05-0.87; NMR-by-intervention interaction p = .004). CONCLUSIONS Treatment support increased abstinence and optimal use of NRT among fast nicotine metabolizers, thereby mitigating the gap in abstinence between fast and slow metabolizers. IMPLICATIONS In this secondary analysis of two smoking cessation interventions for recently hospitalized smokers, fast nicotine metabolizers quit at lower rates than slow metabolizers, but providing fast metabolizers with enhanced treatment support doubled the odds of quitting in this group and mitigated the disparity in abstinence between fast and slow metabolizers. If validated, these findings could lead to personalized approaches to smoking cessation treatment that improve outcomes by targeting treatment support to those who need it most.
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Affiliation(s)
- Scott S Lee
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Yuchiao Chang
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Nancy A Rigotti
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Daniel E Singer
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Douglas E Levy
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Rachel F Tyndale
- Departments of Psychiatry, and Pharmacology and Toxicology, University of Toronto and Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Esa M Davis
- Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Matthew S Freiberg
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Stephen King
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Quinn S Wells
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Hilary A Tindle
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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Precision treatment with nicotine in autosomal dominant sleep-related hypermotor epilepsy (ADSHE): An observational study of clinical outcome and serum cotinine levels in 17 patients. Epilepsy Res 2021; 178:106792. [PMID: 34763266 DOI: 10.1016/j.eplepsyres.2021.106792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/20/2021] [Accepted: 10/15/2021] [Indexed: 11/24/2022]
Abstract
PURPOSE To report the clinical outcome of nicotine exposure in patients with autosomal dominant sleep-related hypermotor epilepsy (ADSHE), along with serum concentrations of the major nicotine metabolite cotinine. METHODS We recruited 17 ADSHE patients with CHRNA4 mutations (12 with p.S280F and 5 with p.L291 dup). Clinical characteristics were collected from hospital records. A telephone interview was performed on the use and seizure-reducing effect of nicotine applying a six-point rating scale from "none" to very good". Serum concentrations of cotinine were measured in 14 nicotine users. RESULTS All patients but one had ever used nicotine. Nine had used snuff; seven were current users. Eleven had used transdermal nicotine; nine were current users. Seven reported long-lasting seizure control, all used nicotine, four transdermal nicotine and three snuff. In 78% of patients using continuous transdermal nicotine, the effect was rated as good or very good. Cotinine concentrations were 453 ± 196 (mean ± SD) nmol/l in seven patients using transdermal nicotine only vs. 1241 ± 494 nmol/l in seven using other forms of nicotine. No correlation with seizure control was found. Three patients experienced improvement with transdermal delivery compared to snuff. CONCLUSION This is the hitherto largest observational study supporting a favorable effect of nicotine in this specific seizure disorder. Better seizure control from transdermal nicotine compared to only day-time consumption suggests benefit from exposure throughout the night. According to current clinical experience, patients with uncontrolled ADSHE harboring relevant mutations should be offered precision treatment with transdermal nicotine.
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Tan X, Vrana K, Ding ZM. Cotinine: Pharmacologically Active Metabolite of Nicotine and Neural Mechanisms for Its Actions. Front Behav Neurosci 2021; 15:758252. [PMID: 34744656 PMCID: PMC8568040 DOI: 10.3389/fnbeh.2021.758252] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/27/2021] [Indexed: 11/17/2022] Open
Abstract
Tobacco use disorder continues to be a leading public health issue and cause of premature death in the United States. Nicotine is considered as the major tobacco alkaloid causing addiction through its actions on nicotinic acetylcholine receptors (nAChRs). Current pharmacotherapies targeting nicotine's effects produce only modest effectiveness in promoting cessation, highlighting the critical need for a better understanding of mechanisms of nicotine addiction to inform future treatments. There is growing interest in identifying potential contributions of non-nicotine components to tobacco reinforcement. Cotinine is a minor alkaloid, but the major metabolite of nicotine that can act as a weak agonist of nAChRs. Accumulating evidence indicates that cotinine produces diverse effects and may contribute to effects of nicotine. In this review, we summarize findings implicating cotinine as a neuroactive metabolite of nicotine and discuss available evidence regarding potential mechanisms underlying its effects. Preclinical findings reveal that cotinine crosses the blood brain barrier and interacts with both nAChRs and non-nAChRs in the nervous system, and produces neuropharmacological and behavioral effects. Clinical studies suggest that cotinine is psychoactive in humans. However, reviewing evidence regarding mechanisms underlying effects of cotinine provides a mixed picture with a lack of consensus. Therefore, more research is warranted in order to provide better insight into the actions of cotinine and its contribution to tobacco addiction.
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Affiliation(s)
- Xiaoying Tan
- Department of Anesthesiology & Perioperative Medicine, and Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Kent Vrana
- Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Zheng-Ming Ding
- Department of Anesthesiology & Perioperative Medicine, and Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, United States
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Iarkov A, Mendoza C, Echeverria V. Cholinergic Receptor Modulation as a Target for Preventing Dementia in Parkinson's Disease. Front Neurosci 2021; 15:665820. [PMID: 34616271 PMCID: PMC8488354 DOI: 10.3389/fnins.2021.665820] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 08/26/2021] [Indexed: 12/20/2022] Open
Abstract
Parkinson’s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) in the midbrain resulting in progressive impairment in cognitive and motor abilities. The physiological and molecular mechanisms triggering dopaminergic neuronal loss are not entirely defined. PD occurrence is associated with various genetic and environmental factors causing inflammation and mitochondrial dysfunction in the brain, leading to oxidative stress, proteinopathy, and reduced viability of dopaminergic neurons. Oxidative stress affects the conformation and function of ions, proteins, and lipids, provoking mitochondrial DNA (mtDNA) mutation and dysfunction. The disruption of protein homeostasis induces the aggregation of alpha-synuclein (α-SYN) and parkin and a deficit in proteasome degradation. Also, oxidative stress affects dopamine release by activating ATP-sensitive potassium channels. The cholinergic system is essential in modulating the striatal cells regulating cognitive and motor functions. Several muscarinic acetylcholine receptors (mAChR) and nicotinic acetylcholine receptors (nAChRs) are expressed in the striatum. The nAChRs signaling reduces neuroinflammation and facilitates neuronal survival, neurotransmitter release, and synaptic plasticity. Since there is a deficit in the nAChRs in PD, inhibiting nAChRs loss in the striatum may help prevent dopaminergic neurons loss in the striatum and its pathological consequences. The nAChRs can also stimulate other brain cells supporting cognitive and motor functions. This review discusses the cholinergic system as a therapeutic target of cotinine to prevent cognitive symptoms and transition to dementia in PD.
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Affiliation(s)
- Alexandre Iarkov
- Laboratorio de Neurobiología, Facultad de Ciencias de la Salud, Universidad San Sebastián, Concepción, Chile
| | - Cristhian Mendoza
- Laboratorio de Neurobiología, Facultad de Ciencias de la Salud, Universidad San Sebastián, Concepción, Chile
| | - Valentina Echeverria
- Laboratorio de Neurobiología, Facultad de Ciencias de la Salud, Universidad San Sebastián, Concepción, Chile.,Research & Development Service, Bay Pines VA Healthcare System, Bay Pines, FL, United States
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Mazzaferro S, Whiteman ST, Alcaino C, Beyder A, Sine SM. NACHO and 14-3-3 promote expression of distinct subunit stoichiometries of the α4β2 acetylcholine receptor. Cell Mol Life Sci 2021; 78:1565-1575. [PMID: 32676916 PMCID: PMC7854996 DOI: 10.1007/s00018-020-03592-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 06/19/2020] [Accepted: 07/01/2020] [Indexed: 02/07/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) belong to the superfamily of pentameric ligand-gated ion channels, and in neuronal tissues, are assembled from various types of α- and β-subunits. Furthermore, the subunits α4 and β2 assemble in two predominant stoichiometric forms, (α4)2(β2)3 and (α4)3(β2)2, forming receptors with dramatically different sensitivity to agonists and allosteric modulators. However, mechanisms by which the two stoichiometric forms are regulated are not known. Here, using heterologous expression in mammalian cells, single-channel patch-clamp electrophysiology, and calcium imaging, we show that the ER-resident protein NACHO selectively promotes the expression of the (α4)2(β2)3 stoichiometry, whereas the cytosolic molecular chaperone 14-3-3η selectively promotes the expression of the (α4)3(β2)2 stoichiometry. Thus, NACHO and 14-3-3η are potential physiological regulators of subunit stoichiometry, and are potential drug targets for re-balancing the stoichiometry in pathological conditions involving α4β2 nAChRs such as nicotine dependence and epilepsy.
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Affiliation(s)
- Simone Mazzaferro
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
| | - Sara T Whiteman
- Enteric Neuroscience Program (ENSP), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, 55905, USA.
| | - Constanza Alcaino
- Enteric Neuroscience Program (ENSP), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Arthur Beyder
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
- Enteric Neuroscience Program (ENSP), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
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Lin SX, Curtis MA, Sperry J. Pyridine alkaloids with activity in the central nervous system. Bioorg Med Chem 2020; 28:115820. [PMID: 33120080 PMCID: PMC7561606 DOI: 10.1016/j.bmc.2020.115820] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/27/2020] [Accepted: 10/05/2020] [Indexed: 12/29/2022]
Abstract
This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.
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Affiliation(s)
- Simon X Lin
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Maurice A Curtis
- Centre for Brain Research, University of Auckland, Auckland, New Zealand; Department of Anatomy and Medical Imaging, University of Auckland, Auckland, New Zealand
| | - Jonathan Sperry
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand.
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E-cigarette aerosols containing nicotine modulate nicotinic acetylcholine receptors and astroglial glutamate transporters in mesocorticolimbic brain regions of chronically exposed mice. Chem Biol Interact 2020; 333:109308. [PMID: 33242460 DOI: 10.1016/j.cbi.2020.109308] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/09/2020] [Accepted: 10/28/2020] [Indexed: 12/30/2022]
Abstract
Nicotine exposure increases the release of glutamate in part through stimulatory effects on pre-synaptic nicotinic acetylcholine receptors (nAChRs). To assess the impact of chronic electronic (e)-cigarette use on these drug dependence pathways, we exposed C57BL/6 mice to three types of inhalant exposures for 3 months; 1) e-cigarette aerosol generated from liquids containing nicotine (ECN), 2) e-cigarette aerosol generated from liquids containing vehicle chemicals without nicotine (Veh), and 3) air only (AC). We investigated the effects of daily e-cigarette exposure on protein levels of α7 nAChR and α4/β2 nAChR, gene expression and protein levels of astroglial glutamate transporters, including glutamate transporter-1 (GLT-1) and cystine/glutamate antiporter (xCT), in the frontal cortex (FC), striatum (STR) and hippocampus (HIP). We found that chronic inhalation of ECN increased α4/β2 nAChR in all brain regions, and increased α7 nAChR expression in the FC and STR. The total GLT-1 relative mRNA and protein expression were decreased in the STR. Moreover, GLT-1 isoforms (GLT-1a and GLT-1b) were downregulated in the STR in ECN group. However, inhalation of e-cigarette aerosol downregulated xCT expression in STR and HIP compared to AC and Veh groups. ECN group had increased brain-derived neurotrophic factor in the STR compared to control groups. Finally, mass spectrometry detected high concentrations of the nicotine metabolite, cotinine, in the FC and STR in ECN group. This work demonstrates that chronic inhalation of nicotine within e-cigarette aerosols significantly alters the expression of nAChRs and astroglial glutamate transporters in specific mesocorticolimbic brain regions.
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Boiangiu RS, Mihasan M, Gorgan DL, Stache BA, Petre BA, Hritcu L. Cotinine and 6-Hydroxy-L-Nicotine Reverses Memory Deficits and Reduces Oxidative Stress in Aβ 25-35-Induced Rat Model of Alzheimer's Disease. Antioxidants (Basel) 2020; 9:E768. [PMID: 32824768 PMCID: PMC7465470 DOI: 10.3390/antiox9080768] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 08/08/2020] [Accepted: 08/13/2020] [Indexed: 12/15/2022] Open
Abstract
The nicotinic derivatives, cotinine (COT), and 6-hydroxy-L-nicotine (6HLN), showed promising cognitive-improving effects without exhibiting the nicotine's side-effects. Here, we investigated the impact of COT and 6HLN on memory impairment and the oxidative stress in the Aβ25-35-induced rat model of Alzheimer's disease (AD). COT and 6HLN were chronically administered to Aβ25-35-treated rats, and their memory performances were assessed using in vivo tasks (Y-maze, novel object recognition, and radial arm maze). By using in silico tools, we attempted to associate the behavioral outcomes with the calculated binding potential of these nicotinic compounds in the allosteric sites of α7 and α4β2 subtypes of the nicotinic acetylcholine receptors (nAChRs). The oxidative status and acetylcholinesterase (AChE) activity were determined from the hippocampal tissues. RT-qPCR assessed bdnf, arc, and il-1β mRNA levels. Our data revealed that COT and 6HLN could bind to α7 and α4β2 nAChRs with similar or even higher affinity than nicotine. Consequently, the treatment exhibited a pro-cognitive, antioxidant, and anti-AChE profile in the Aβ25-35-induced rat model of AD. Finally, RT-qPCR analysis revealed that COT and 6HLN positively modulated the bdnf, arc, and il-1β genes expression. Therefore, these nicotinic derivatives that act on the cholinergic system might represent a promising choice to ameliorate AD conditions.
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Affiliation(s)
- Razvan Stefan Boiangiu
- Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania; (R.S.B.); (M.M.); (D.L.G.); (B.A.S.)
| | - Marius Mihasan
- Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania; (R.S.B.); (M.M.); (D.L.G.); (B.A.S.)
| | - Dragos Lucian Gorgan
- Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania; (R.S.B.); (M.M.); (D.L.G.); (B.A.S.)
| | - Bogdan Alexandru Stache
- Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania; (R.S.B.); (M.M.); (D.L.G.); (B.A.S.)
- Center for Fundamental Research and Experimental Development in Translation Medicine—TRANSCEND, Regional Institute of Oncology, 700483 Iasi, Romania;
| | - Brindusa Alina Petre
- Center for Fundamental Research and Experimental Development in Translation Medicine—TRANSCEND, Regional Institute of Oncology, 700483 Iasi, Romania;
- Department of Chemistry, Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania
| | - Lucian Hritcu
- Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, 700506 Iasi, Romania; (R.S.B.); (M.M.); (D.L.G.); (B.A.S.)
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Bavan S, Kim CH, Henderson BJ, Lester HA. Chronic Menthol Does Not Change Stoichiometry or Functional Plasma Membrane Levels of Mouse α3 β4-Containing Nicotinic Acetylcholine Receptors. Mol Pharmacol 2019; 95:398-407. [PMID: 30670481 PMCID: PMC6399576 DOI: 10.1124/mol.118.114769] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/12/2019] [Indexed: 11/22/2022] Open
Abstract
Heteromeric α3β4 nicotinic acetylcholine (ACh) receptors (nAChRs) are pentameric ligand-gated cation channels that include at least two α3 and two β4 subunits. They have functions in peripheral tissue and peripheral and central nervous systems. We examined the effects of chronic treatment with menthol, a major flavor additive in tobacco cigarettes and electronic nicotine delivery systems, on mouse α3β4 nAChRs transiently transfected into neuroblastoma-2a cells. Chronic menthol treatment at 500 nM, near the estimated menthol concentration in the brain following cigarette smoking, altered neither the [ACh]-response relationship nor Zn2+ sensitivity of ACh-evoked currents, suggesting that menthol does not change α3β4 nAChR subunit stoichiometry. Chronic menthol treatment failed to change the current density (peak current amplitude/cell capacitance) of 100 μM ACh-evoked currents. Chronic menthol treatment accelerated desensitization of 100 and 200 μM ACh-evoked currents. Chronic nicotine treatment (250 μM) decreased ACh-induced currents, and we found no additional effect of including chronic menthol. These data contrast with previously reported, marked effects of chronic menthol on β2* nAChRs studied in the same expression system. Mechanistically, the data support the emerging interpretation that both chronic menthol and chronic nicotine act on nAChRs in the early exocytotic pathway, and that this pathway does not present a rate-limiting step to the export of α3β4 nAChRs; these nAChRs include endoplasmic reticulum (ER) export motifs but not ER retention motifs. Previous reports show that smoking mentholated cigarettes enhances tobacco addiction; but our results show that this effect is unlikely to arise via menthol actions on α3β4 nAChRs.
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Affiliation(s)
- Selvan Bavan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California (S.B., C.H.K., H.A.L.); and Department of Biomedical Sciences, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (B.J.H.)
| | - Charlene H Kim
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California (S.B., C.H.K., H.A.L.); and Department of Biomedical Sciences, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (B.J.H.)
| | - Brandon J Henderson
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California (S.B., C.H.K., H.A.L.); and Department of Biomedical Sciences, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (B.J.H.)
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California (S.B., C.H.K., H.A.L.); and Department of Biomedical Sciences, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (B.J.H.)
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Majdi A, Kamari F, Sadigh-Eteghad S, Gjedde A. Molecular Insights Into Memory-Enhancing Metabolites of Nicotine in Brain: A Systematic Review. Front Neurosci 2019; 12:1002. [PMID: 30697142 PMCID: PMC6341027 DOI: 10.3389/fnins.2018.01002] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 12/12/2018] [Indexed: 01/25/2023] Open
Abstract
Background: The alleged procognitive effects of nicotine and its metabolites in brain are controversial. Objective: Here, we review the pharmacologically active metabolites of nicotine in brain and their effects on neuronal mechanisms involving two main cognitive domains, i.e., learning and memory. Methods: We searched Embase, Medline via PubMed, Scopus, and Web of Science databases for entries no later than May 2018, and restricted the search to articles about nicotine metabolites and cognitive behavior or cognitive mechanisms. Results: The initial search yielded 425 articles, of which 17 were eligible for inclusion after application of exclusion criteria. Of these, 13 were experimental, two were clinical, and two were conference papers. Conclusions: The results revealed three pharmacologically active biotransformations of nicotine in the brain, including cotinine, norcotinine, and nornicotine, among which cotinine and nornicotine both had a procognitive impact without adverse effects. The observed effect was significant only for cotinine.
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Affiliation(s)
- Alireza Majdi
- Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Farzin Kamari
- Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Saeed Sadigh-Eteghad
- Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Albert Gjedde
- Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
- Department of Clinical Research, University of Southern Denmark, Odense, Denmark
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States
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Moonschi FH, Fox-Loe AM, Fu X, Richards CI. Mammalian Cell-derived Vesicles for the Isolation of Organelle Specific Transmembrane Proteins to Conduct Single Molecule Studies. Bio Protoc 2018; 8:e2825. [PMID: 30406159 DOI: 10.21769/bioprotoc.2825] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cell-derived vesicles facilitate the isolation of transmembrane proteins in their physiological membrane maintaining their structural and functional integrity. These vesicles can be generated from different cellular organelles producing, housing, or transporting the proteins. Combined with single-molecule imaging, isolated organelle specific vesicles can be employed to study the trafficking and assembly of the embedded proteins. Here we present a method for organelle specific single molecule imaging via isolation of ER and plasma membrane vesicles from HEK293T cells by employing OptiPrep gradients and nitrogen cavitation. The isolation was validated through Western blotting, and the isolated vesicles were used to perform single molecule studies of oligomeric receptor assembly.
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Affiliation(s)
- Faruk H Moonschi
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Ashley M Fox-Loe
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Xu Fu
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Chris I Richards
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
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Qian J, Mummalaneni S, Larsen J, Grider JR, Spielman AI, Özdener MH, Lyall V. Nicotinic acetylcholine receptor (CHRN) expression and function in cultured human adult fungiform (HBO) taste cells. PLoS One 2018. [PMID: 29513745 PMCID: PMC5841828 DOI: 10.1371/journal.pone.0194089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In rodents, CHRNs are involved in bitter taste transduction of nicotine and ethanol. Currently, it is not clear if CHRNs are expressed in human taste cells and if they play a role in transducing the bitter taste of nicotine and ethanol or in the synthesis and release of neurohumoral peptides. Accordingly, we investigated the expression and functional role of CHRNs in HBO cells. Using molecular techniques, we demonstrate that a subset of HBO cells express CHRNs that also co-express TRPM5, T1R3 or T2R38. Exposing HBO cells to nicotine or ethanol acutely or to nicotine chronically induced a differential increase in the expression of CHRN mRNA and protein in a dose- and time-dependent manner. Acutely exposing HBO cells to a mixture containing nicotine plus ethanol induced a smaller increase in CHRN mRNAs relative to nicotine or ethanol treatment alone. A subset of HBO cells responded to nicotine, acetylcholine and ATP with a transient increase in [Ca2+]i. Nicotine effects on [Ca2+]i were mecamylamine sensitive. Brain-derived neurotrophic factor (BDNF) protein was detected in HBO cells using ELISA. Acute nicotine exposure decreased BDNF in HBO cells and increased BDNF release in the medium. CHRNs were also detected in HEK293 cells by RT-PCR. Unlike HBO cells, CHRNs were localized in most of HEK293 cells and majority of HEK293 cells responded to nicotine and ethanol stimulation with a transient increase in [Ca2+]i. BDNF levels in HEK293 cells were significantly higher than in HBO cells but the nicotine induced release of BDNF in the media was a fraction of the BDNF cellular content. We conclude that CHRNs are expressed in TRPM5 positive HBO cells. CHRN mRNA expression is modulated by exposure to nicotine and ethanol in a dose- and time-dependent manner. Nicotine induces the synthesis and release of BDNF in HBO cells.
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Affiliation(s)
- Jie Qian
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
| | - Shobha Mummalaneni
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
| | - James Larsen
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
| | - John R. Grider
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
| | | | | | - Vijay Lyall
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
- * E-mail:
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Rego Campello H, Gallagher T. C(5) Site-Selective Functionalization of (S)-Cotinine. J Org Chem 2018; 83:516-520. [PMID: 29207240 DOI: 10.1021/acs.joc.7b02704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
(S)-(-)-Cotinine 2 undergoes direct and site-selective iridium-catalyzed borylation to provide boronate ester 3 and bromide 4 which offer flexible entry to a range of C(5)-substituted cotinine variants.
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Affiliation(s)
- Hugo Rego Campello
- School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom
| | - Timothy Gallagher
- School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom
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15
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Fox-Loe AM, Moonschi FH, Richards CI. Organelle-specific single-molecule imaging of α4β2 nicotinic receptors reveals the effect of nicotine on receptor assembly and cell-surface trafficking. J Biol Chem 2017; 292:21159-21169. [PMID: 29074617 DOI: 10.1074/jbc.m117.801431] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 10/20/2017] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) assemble in the endoplasmic reticulum (ER) and traffic to the cell surface as pentamers composed of α and β subunits. Many nAChR subtypes can assemble with varying subunit ratios, giving rise to multiple stoichiometries exhibiting different subcellular localization and functional properties. In addition to the endogenous neurotransmitter acetylcholine, nicotine also binds and activates nAChRs and influences their trafficking and expression on the cell surface. Currently, no available technique can specifically elucidate the stoichiometry of nAChRs in the ER versus those in the plasma membrane. Here, we report a method involving single-molecule fluorescence measurements to determine the structural properties of these membrane proteins after isolation in nanoscale vesicles derived from specific organelles. These cell-derived nanovesicles allowed us to separate single membrane receptors while maintaining them in their physiological environment. Sorting the vesicles according to the organelle of origin enabled us to determine localized differences in receptor structural properties, structural influence on transport between organelles, and changes in receptor assembly within intracellular organelles. These organelle-specific nanovesicles revealed that one structural isoform of the α4β2 nAChR was preferentially trafficked to the cell surface. Moreover, nicotine altered nAChR assembly in the ER, resulting in increased production of the receptor isoform that traffics more efficiently to the cell surface. We conclude that the combined effects of the increased assembly of one nAChR stoichiometry and its preferential trafficking likely drive the up-regulation of nAChRs on the cell surface upon nicotine exposure.
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Affiliation(s)
- Ashley M Fox-Loe
- From the Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506
| | - Faruk H Moonschi
- From the Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506
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16
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Martin WE, Ge N, Srijanto BR, Furnish E, Collier CP, Trinkle CA, Richards CI. Real-Time Sensing of Single-Ligand Delivery with Nanoaperture-Integrated Microfluidic Devices. ACS OMEGA 2017; 2:3858-3867. [PMID: 28782052 PMCID: PMC5537690 DOI: 10.1021/acsomega.7b00934] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 07/11/2017] [Indexed: 05/28/2023]
Abstract
The measurement of biological events on the surface of live cells at the single-molecule level is complicated by several factors including high protein densities that are incompatible with single-molecule imaging, cellular autofluorescence, and protein mobility on the cell surface. Here, we fabricated a device composed of an array of nanoscale apertures coupled with a microfluidic delivery system to quantify single-ligand interactions with proteins on the cell surface. We cultured live cells directly on the device and isolated individual epidermal growth factor receptors (EGFRs) in the apertures while delivering fluorescently labeled epidermal growth factor. We observed single ligands binding to EGFRs, allowing us to quantify the ligand turnover in real time. These results demonstrate that this nanoaperture-coupled microfluidic device allows for the spatial isolation of individual membrane proteins while maintaining them in their cellular environment, providing the capability to monitor single-ligand binding events while maintaining receptors in their physiological environment. These methods should be applicable to a wide range of membrane proteins.
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Affiliation(s)
- W. Elliott Martin
- Department
of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506, United States
| | - Ning Ge
- Department
of Mechanical Engineering, University of
Kentucky, 151 Ralph G.
Anderson Building, Lexington, Kentucky 40506, United
States
| | - Bernadeta R. Srijanto
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge Tennessee 37831, United States
| | - Emily Furnish
- Department
of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506, United States
| | - C. Patrick Collier
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge Tennessee 37831, United States
| | - Christine A. Trinkle
- Department
of Mechanical Engineering, University of
Kentucky, 151 Ralph G.
Anderson Building, Lexington, Kentucky 40506, United
States
| | - Christopher I. Richards
- Department
of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506, United States
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Govind AP, Vallejo YF, Stolz JR, Yan JZ, Swanson GT, Green WN. Selective and regulated trapping of nicotinic receptor weak base ligands and relevance to smoking cessation. eLife 2017; 6. [PMID: 28718768 PMCID: PMC5546804 DOI: 10.7554/elife.25651] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 07/03/2017] [Indexed: 01/11/2023] Open
Abstract
To better understand smoking cessation, we examined the actions of varenicline (Chantix) during long-term nicotine exposure. Varenicline reduced nicotine upregulation of α4β2-type nicotinic receptors (α4β2Rs) in live cells and neurons, but not for membrane preparations. Effects on upregulation depended on intracellular pH homeostasis and were not observed if acidic pH in intracellular compartments was neutralized. Varenicline was trapped as a weak base in acidic compartments and slowly released, blocking 125I-epibatidine binding and desensitizing α4β2Rs. Epibatidine itself was trapped; 125I-epibatidine slow release from acidic vesicles was directly measured and required the presence of α4β2Rs. Nicotine exposure increased epibatidine trapping by increasing the numbers of acidic vesicles containing α4β2Rs. We conclude that varenicline as a smoking cessation agent differs from nicotine through trapping in α4β2R-containing acidic vesicles that is selective and nicotine-regulated. Our results provide a new paradigm for how smoking cessation occurs and suggest how more effective smoking cessation reagents can be designed. DOI:http://dx.doi.org/10.7554/eLife.25651.001 Tobacco continues to be widely used worldwide, primarily via cigarette smoking, and is a leading cause of preventable deaths. Stopping smoking is difficult because the nicotine in tobacco is highly addictive, and so several drugs have been developed to help people break their addiction. Varenicline (also known by the trade name Chantix) is a commonly prescribed anti-smoking drug, but it is not fully understood how it works. Nicotine affects the brain by binding to proteins called nicotinic acetylcholine receptors (nAChRs) that sit on the surface of neurons. This binding releases a number of chemical signals, including some that produce feelings of pleasure. Over time, the receptors become less sensitive to nicotine and produce more “high-affinity” binding sites for nicotine to bind to. This adaptation is one reason why stopping smoking can produce strong feelings of withdrawal. Previously, varenicline was thought to partially activate nAChRs, preventing nicotine from binding to the receptors. However, this can only explain how varenicline counteracts the rapid-acting effects of nicotine, not nicotine’s longer-term effects. Furthermore, it was not known how nAChR signaling responds to long-term exposure to a combination of both drugs (as occurs when people try to quit smoking with the aid of varenicline). Now, Govind et al. reveal how varenicline reverses the effect of long-term nicotine exposure on nAChR signaling. Both varenicline and nicotine accumulate in acidic compartments – called vesicles – inside cells, where they become charged and less able to move through the cell membrane. When the vesicles also contain high-affinity nAChRs, varenicline becomes trapped inside them and is only slowly released. By contrast, nicotine is not trapped because it exits the vesicles more rapidly. Long-term exposure to nicotine greatly increased the number of vesicles that contained high-affinity nAChRs, thereby trapping more varenicline. One consequence of trapping varenicline was that the activity of the nAChRs on the surface of the neuron was diminished, apparently through the slow release of the trapped varenicline from the acidic vesicles. This slow release causes the receptors to enter a “desensitized” state in which they do not signal. Understanding how varenicline counteracts the long-term effects of nicotine on nAChR signaling will help us to design more effective anti-smoking drugs. Govind et al. also found that compounds similar to varenicline become trapped in vesicles, but it is not clear how the degree of trapping of a compound correlates with how effectively it combats nicotine addiction. The results may also help us to understand and treat addictions to other drugs of abuse, such as opioids, amphetamines and cocaine, which have chemical properties that mean they might also be selectively trapped in acidic vesicles. DOI:http://dx.doi.org/10.7554/eLife.25651.002
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Affiliation(s)
- Anitha P Govind
- Department of Neurobiology, University of Chicago, Chicago, United States
| | - Yolanda F Vallejo
- National Institute of Dental and Craniofacial Research at the National Institutes of Health, , United States
| | - Jacob R Stolz
- Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Evanston, United States
| | - Jing-Zhi Yan
- Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Evanston, United States
| | - Geoffrey T Swanson
- Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Evanston, United States
| | - William N Green
- Department of Neurobiology, University of Chicago, Chicago, United States.,Marine Biological Laboratory, Woods Hole, United States
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Crespi A, Colombo SF, Gotti C. Proteins and chemical chaperones involved in neuronal nicotinic receptor expression and function: an update. Br J Pharmacol 2017; 175:1869-1879. [PMID: 28294298 DOI: 10.1111/bph.13777] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/26/2017] [Accepted: 03/04/2017] [Indexed: 01/03/2023] Open
Abstract
Neuronal nicotinic ACh receptors (nAChRs) are a family of ACh-gated cation channels, and their homeostasis or proteostasis is essential for the correct physiology of the central and peripheral nervous systems. The proteostasis network regulates the folding, assembly, degradation and trafficking of nAChRs in order to ensure their efficient and functional expression at the cell surface. However, as nAChRs are multi-subunit, multi-span, integral membrane proteins, the folding and assembly is a very inefficient process, and only a small proportion of subunits can form functional pentamers. Moreover, the efficiency of assembly and trafficking varies widely depending on the nAChR subtypes and the cell type in which they are expressed. A detailed understanding of the mechanisms that regulate the functional expression of nAChRs in neurons and non-neuronal cells is therefore important. The purpose of this short review is to describe more recent findings concerning the chaperone proteins and target-specific and target-nonspecific pharmacological chaperones that modulate the expression of nAChR subtypes, and the possible mechanisms that underlie the dynamic changes of cell surface nAChRs. LINKED ARTICLES This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.
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Fox-Loe AM, Henderson BJ, Richards CI. Utilizing pHluorin-tagged Receptors to Monitor Subcellular Localization and Trafficking. J Vis Exp 2017:55466. [PMID: 28362418 PMCID: PMC5409030 DOI: 10.3791/55466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Understanding membrane protein trafficking, assembly, and expression requires an approach that differentiates between those residing in intracellular organelles and those localized on the plasma membrane. Traditional fluorescence-based measurements lack the capability to distinguish membrane proteins residing in different organelles. Cutting edge methodologies transcend traditional methods by coupling pH-sensitive fluorophores with total internal reflection fluorescence microscopy (TIRFM). TIRF illumination excites the sample up to approximately 150 nm from the glass-sample interface, thus decreasing background, increasing the signal to noise ratio, and enhancing resolution. The excitation volume in TIRFM encompasses the plasma membrane and nearby organelles such as the peripheral ER. Superecliptic pHluorin (SEP) is a pH sensitive version of GFP. Genetically encoding SEP into the extracellular domain of a membrane protein of interest positions the fluorophore on the luminal side of the ER and in the extracellular region of the cell. SEP is fluorescent when the pH is greater than 6, but remains in an off state at lower pH values. Therefore, receptors tagged with SEP fluoresce when residing in the endoplasmic reticulum (ER) or upon insertion in the plasma membrane (PM) but not when confined to a trafficking vesicle or other organelles such as the Golgi. The extracellular pH can be adjusted to dictate the fluorescence of receptors on the plasma membrane. The difference in fluorescence between TIRF images at neutral and acidic extracellular pH for the same cell corresponds to a relative number of receptors on the plasma membrane. This allows a simultaneous measurement of intracellular and plasma membrane resident receptors. Single vesicle insertion events can also be measured when the extracellular pH is neutral, corresponding to a low pH trafficking vesicle fusing with the plasma membrane and transitioning into a fluorescent state. This versatile technique can be exploited to study localization, expression, and trafficking of membrane proteins.
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Nicotine-Induced Effects on Nicotinic Acetylcholine Receptors (nAChRs), Ca2+ and Brain-Derived Neurotrophic Factor (BDNF) in STC-1 Cells. PLoS One 2016; 11:e0166565. [PMID: 27846263 PMCID: PMC5112875 DOI: 10.1371/journal.pone.0166565] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 10/30/2016] [Indexed: 02/06/2023] Open
Abstract
In addition to the T2R bitter taste receptors, neuronal nicotinic acetylcholine receptors (nAChRs) have recently been shown to be involved in the bitter taste transduction of nicotine, acetylcholine and ethanol. However, at present it is not clear if nAChRs are expressed in enteroendocrine cells other than beta cells of the pancreas and enterochromaffin cells, and if they play a role in the synthesis and release of neurohumoral peptides. Accordingly, we investigated the expression and functional role of nAChRs in enteroendocrine STC-1 cells. Our studies using RT-PCR, qRT-PCR, immunohistochemical and Western blotting techniques demonstrate that STC-1 cells express several α and β nAChR subunits. Exposing STC-1 cells to nicotine acutely (24h) or chronically (4 days) induced a differential increase in the expression of nAChR subunit mRNA and protein in a dose- and time-dependent fashion. Mecamylamine, a non-selective antagonist of nAChRs, inhibited the nicotine-induced increase in mRNA expression of nAChRs. Exposing STC-1 cells to nicotine increased intracellular Ca2+ in a dose-dependent manner that was inhibited in the presence of mecamylamine or dihydro-β-erythroidine, a α4β2 nAChR antagonist. Brain-derived neurotrophic factor (BDNF) mRNA and protein were detected in STC-1 cells using RT-PCR, specific BDNF antibody, and enzyme-linked immunosorbent assay. Acute nicotine exposure (30 min) decreased the cellular content of BDNF in STC-1 cells. The nicotine-induced decrease in BDNF was inhibited in the presence of mecamylamine. We also detected α3 and β4 mRNA in intestinal mucosal cells and α3 protein expression in intestinal enteroendocrine cells. We conclude that STC-1 cells and intestinal enteroendocrine cells express nAChRs. In STC-1 cells nAChR expression is modulated by exposure to nicotine in a dose- and time-dependent manner. Nicotine interacts with nAChRs and inhibits BDNF expression in STC-1 cells.
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Fox-Loe AM, Dwoskin LP, Richards CI. Nicotinic Acetylcholine Receptors as Targets for Tobacco Cessation Therapeutics: Cutting-Edge Methodologies to Understand Receptor Assembly and Trafficking. NEUROMETHODS 2016; 117:119-132. [PMID: 28025590 DOI: 10.1007/978-1-4939-3768-4_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Tobacco dependence is a chronic relapsing disorder and nicotine, the primary alkaloid in tobacco, acts at nicotinic receptors to stimulate dopamine release in brain, which is responsible for the reinforcing properties of nicotine, leading to addiction. Although the majority of tobacco users express the desire to quit, only a small percentage of those attempting to quit are successful using the currently available pharmacotherapies. Nicotine upregulates the number of specific nicotinic receptors on the neuronal cell surface. An increase in receptor trafficking or preferential stoichiometric assembly of receptor subunits involves changes in assembly, endoplasmic reticulum export, vesicle transport, decreased degradation, desensitization, enhanced maturation of functional pentamers, and pharmacological chaperoning. Understanding these changes on a mechanistic level is important to the development of nicotinic receptors as drug targets. For this reason, cutting-edge methodologies are being developed and employed to pinpoint distinct changes in localization, assembly, export, vesicle trafficking, and stoichiometry in order to further understand the physiology of these receptors and to evaluate the action of novel therapeutics for smoking cessation.
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Fu YL, Wang YJ, Mu TW. Proteostasis Maintenance of Cys-Loop Receptors. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:1-23. [DOI: 10.1016/bs.apcsb.2015.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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