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Chrestia JF, Turani O, Araujo NR, Hernando G, Esandi MDC, Bouzat C. Regulation of nicotinic acetylcholine receptors by post-translational modifications. Pharmacol Res 2023; 190:106712. [PMID: 36863428 DOI: 10.1016/j.phrs.2023.106712] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/21/2023] [Accepted: 02/24/2023] [Indexed: 03/04/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) comprise a family of pentameric ligand-gated ion channels widely distributed in the central and peripheric nervous system and in non-neuronal cells. nAChRs are involved in chemical synapses and are key actors in vital physiological processes throughout the animal kingdom. They mediate skeletal muscle contraction, autonomic responses, contribute to cognitive processes, and regulate behaviors. Dysregulation of nAChRs is associated with neurological, neurodegenerative, inflammatory and motor disorders. In spite of the great advances in the elucidation of nAChR structure and function, our knowledge about the impact of post-translational modifications (PTMs) on nAChR functional activity and cholinergic signaling has lagged behind. PTMs occur at different steps of protein life cycle, modulating in time and space protein folding, localization, function, and protein-protein interactions, and allow fine-tuned responses to changes in the environment. A large body of evidence demonstrates that PTMs regulate all levels of nAChR life cycle, with key roles in receptor expression, membrane stability and function. However, our knowledge is still limited, restricted to a few PTMs, and many important aspects remain largely unknown. There is thus a long way to go to decipher the association of aberrant PTMs with disorders of cholinergic signaling and to target PTM regulation for novel therapeutic interventions. In this review we provide a comprehensive overview of what is known about how different PTMs regulate nAChR.
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Affiliation(s)
- Juan Facundo Chrestia
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina
| | - Ornella Turani
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina
| | - Noelia Rodriguez Araujo
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina
| | - Guillermina Hernando
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina
| | - María Del Carmen Esandi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina
| | - Cecilia Bouzat
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina.
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2
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Speculation on How RIC-3 and Other Chaperones Facilitate α7 Nicotinic Receptor Folding and Assembly. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27144527. [PMID: 35889400 PMCID: PMC9318448 DOI: 10.3390/molecules27144527] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/07/2022] [Accepted: 07/09/2022] [Indexed: 11/17/2022]
Abstract
The process of how multimeric transmembrane proteins fold and assemble in the endoplasmic reticulum is not well understood. The alpha7 nicotinic receptor (α7 nAChR) is a good model for multimeric protein assembly since it has at least two independent and specialized chaperones: Resistance to Inhibitors of Cholinesterase 3 (RIC-3) and Nicotinic Acetylcholine Receptor Regulator (NACHO). Recent cryo-EM and NMR data revealed structural features of α7 nAChRs. A ser-ala-pro (SAP) motif precedes a structurally important but unique "latch" helix in α7 nAChRs. A sampling of α7 sequences suggests the SAP motif is conserved from C. elegans to humans, but the latch sequence is only conserved in vertebrates. How RIC-3 and NACHO facilitate receptor subunits folding into their final pentameric configuration is not known. The artificial intelligence program AlphaFold2 recently predicted structures for NACHO and RIC-3. NACHO is highly conserved in sequence and structure across species, but RIC-3 is not. This review ponders how different intrinsically disordered RIC-3 isoforms from C. elegans to humans interact with α7 nAChR subunits despite having little sequence homology across RIC-3 species. Two models from the literature about how RIC-3 assists α7 nAChR assembly are evaluated considering recent structural information about the receptor and its chaperones.
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3
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Korona D, Dirnberger B, Giachello CNG, Queiroz RML, Popovic R, Müller KH, Minde DP, Deery MJ, Johnson G, Firth LC, Earley FG, Russell S, Lilley KS. Drosophila nicotinic acetylcholine receptor subunits and their native interactions with insecticidal peptide toxins. eLife 2022; 11:74322. [PMID: 35575460 PMCID: PMC9110030 DOI: 10.7554/elife.74322] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 04/19/2022] [Indexed: 12/14/2022] Open
Abstract
Drosophila nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that represent a target for insecticides. Peptide neurotoxins are known to block nAChRs by binding to their target subunits, however, a better understanding of this mechanism is needed for effective insecticide design. To facilitate the analysis of nAChRs we used a CRISPR/Cas9 strategy to generate null alleles for all ten nAChR subunit genes in a common genetic background. We studied interactions of nAChR subunits with peptide neurotoxins by larval injections and styrene maleic acid lipid particles (SMALPs) pull-down assays. For the null alleles, we determined the effects of α-Bungarotoxin (α-Btx) and ω-Hexatoxin-Hv1a (Hv1a) administration, identifying potential receptor subunits implicated in the binding of these toxins. We employed pull-down assays to confirm α-Btx interactions with the Drosophila α5 (Dα5), Dα6, Dα7 subunits. Finally, we report the localisation of fluorescent tagged endogenous Dα6 during Drosophila CNS development. Taken together, this study elucidates native Drosophila nAChR subunit interactions with insecticidal peptide toxins and provides a resource for the in vivo analysis of insect nAChRs.
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Affiliation(s)
- Dagmara Korona
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Benedict Dirnberger
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, United Kingdom.,Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.,Syngenta, Jealott's Hill International Research Centre, Bracknell, United Kingdom
| | - Carlo N G Giachello
- Syngenta, Jealott's Hill International Research Centre, Bracknell, United Kingdom
| | - Rayner M L Queiroz
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Rebeka Popovic
- MRC Toxicology Unit, Gleeson Building, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
| | - Karin H Müller
- Cambridge Advanced Imaging Centre, Department of Physiology, Development and Neuroscience/Anatomy Building, University of Cambridge, Cambridge, United Kingdom
| | - David-Paul Minde
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Michael J Deery
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Glynnis Johnson
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Lucy C Firth
- Syngenta, Jealott's Hill International Research Centre, Bracknell, United Kingdom
| | - Fergus G Earley
- Syngenta, Jealott's Hill International Research Centre, Bracknell, United Kingdom
| | - Steven Russell
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Kathryn S Lilley
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
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Tillman TS, Choi Z, Xu Y, Tang P. Functional Tolerance to Cysteine Mutations in Human α7 Nicotinic Acetylcholine Receptors. ACS Chem Neurosci 2020; 11:242-247. [PMID: 31951367 DOI: 10.1021/acschemneuro.9b00647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (α7 nAChR) is involved in various intracellular signaling pathways that mediate addiction, chronic pain, and other diseases, but its intracellular domain structures remain undetermined. The presence of 17 native cysteines in α7 nAChR provides opportunities for extracting structural information through site-directed labeling of chemical probes in strategic locations, but it also creates uncertainties in channel function when those native cysteines must be mutated. Using site-directed mutagenesis and two-electrode voltage clamp electrophysiology measurements, we found that α7 nAChR's function was well tolerated for mutations of all 13 cysteines as long as two pairs of disulfide-bond cysteines remained in the extracellular domain. Furthermore, surface plasmon resonance measurements showed that the cysteine mutations did not affect α7 nAChR binding to the intracellular protein PICK1. The study suggests that a high native cysteine content does not necessarily preclude the use of single cysteine labeling for acquiring structural information on functional proteins.
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Affiliation(s)
- Tommy S. Tillman
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Zachary Choi
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Yan Xu
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Pei Tang
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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5
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Cardenas A, Elabd M, Lotfipour S. Specificity of a rodent alpha(α)6 nicotinic acetylcholine receptor subunit antibody. Psychopharmacology (Berl) 2020; 237:283-285. [PMID: 31786649 PMCID: PMC6954311 DOI: 10.1007/s00213-019-05413-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 11/21/2019] [Indexed: 10/25/2022]
Abstract
Alpha(α)6-containing nicotinic acetylcholine receptors (nAChRs) have been implicated in nicotine reward and reinforcement. To date, a commercially available, validated α6 nAChR subunit antibody has not been reported. To evaluate a commercially available neuronal α6 nAChR subunit antibody we performed quantitative western blots on protein from the ventral tegmental area of wild type Sprague Dawley rats. As a first approach to determine the specificity of the antibody, we used a control antigen to block the α6 antibody from binding. Next, we tested the antibody in brain tissue of wild type and α6 knockout (KO) C57BL/6J mice. The α6 antibody was present at a higher than expected molecular weight (63 versus 57 kDa) and the control antigen blocked the α6 antibody, suggesting specificity. However, when we genetically validated the antibody, bands were present in both α6 KO mice and C57BL/6J samples. Taken together, our study highlights the necessity to genetically validate antibodies when possible and we report that a commercially available α6 nAChR subunit antibody is non-specific.
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Affiliation(s)
- Anjelica Cardenas
- Department of Pharmacuetical Sciences, College of Health Sciences, University of California, Irvine, Irvine CA, USA
| | - Mina Elabd
- Biological Sciences, University of California, Irvine, Irvine CA, USA
| | - Shahrdad Lotfipour
- Department of Pharmacuetical Sciences, College of Health Sciences, University of California Irvine, Irvine, CA, USA. .,Department of Emergency Medicine, School of Medicine, University of California Irvine, Irvine, CA, 92697-4625, USA.
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6
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Kim YC, Lee SE, Kim SK, Jang HD, Hwang I, Jin S, Hong EB, Jang KS, Kim HS. Toll-like receptor mediated inflammation requires FASN-dependent MYD88 palmitoylation. Nat Chem Biol 2019; 15:907-916. [PMID: 31427815 DOI: 10.1038/s41589-019-0344-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 07/11/2019] [Indexed: 12/24/2022]
Abstract
Toll-like receptor (TLR)/myeloid differentiation primary response protein (MYD88) signaling aggravates sepsis by impairing neutrophil migration to infection sites. However, the role of intracellular fatty acids in TLR/MYD88 signaling is unclear. Here, inhibition of fatty acid synthase by C75 improved neutrophil chemotaxis and increased the survival of mice with sepsis in cecal ligation puncture and lipopolysaccharide-induced septic shock models. C75 specifically blocked TLR/MYD88 signaling in neutrophils. Treatment with GSK2194069 that targets a different domain of fatty acid synthase, did not block TLR signaling or MYD88 palmitoylation. De novo fatty acid synthesis and CD36-mediated exogenous fatty acid incorporation contributed to MYD88 palmitoylation. The binding of IRAK4 to the MYD88 intermediate domain and downstream signal activation required MYD88 palmitoylation at cysteine 113. MYD88 was palmitoylated by ZDHHC6, and ZDHHC6 knockdown decreased MYD88 palmitoylation and TLR/MYD88 activation upon lipopolysaccharide stimulus. Thus, intracellular saturated fatty acid-dependent palmitoylation of MYD88 by ZDHHC6 is a therapeutic target of sepsis.
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Affiliation(s)
- Young-Chan Kim
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea
| | - Sang Eun Lee
- Cardiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Somi K Kim
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea
| | - Hyun-Duk Jang
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea
| | - Injoo Hwang
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea
| | - Sooryeonhwa Jin
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea.,Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea
| | - Eun-Byeol Hong
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea.,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea
| | - Kyoung-Soon Jang
- Biomedical Omics Center, Korea Basic Science Institute, Cheongju, South Korea
| | - Hyo-Soo Kim
- Strategic Center of Cell & Bio Therapy, Seoul National University Hospital, Seoul, Korea. .,Korea Research-Driven Hospital, Seoul National University Hospital, Seoul, Korea. .,Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea. .,World Class University Program, Department of Molecular Medicine and Biopharmaceutical Sciences, Seoul National University, Seoul, Korea.
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7
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Palmitoylation as a Functional Regulator of Neurotransmitter Receptors. Neural Plast 2018; 2018:5701348. [PMID: 29849559 PMCID: PMC5903346 DOI: 10.1155/2018/5701348] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 01/29/2018] [Indexed: 12/11/2022] Open
Abstract
The majority of neuronal proteins involved in cellular signaling undergo different posttranslational modifications significantly affecting their functions. One of these modifications is a covalent attachment of a 16-C palmitic acid to one or more cysteine residues (S-palmitoylation) within the target protein. Palmitoylation is a reversible modification, and repeated cycles of palmitoylation/depalmitoylation might be critically involved in the regulation of multiple signaling processes. Palmitoylation also represents a common posttranslational modification of the neurotransmitter receptors, including G protein-coupled receptors (GPCRs) and ligand-gated ion channels (LICs). From the functional point of view, palmitoylation affects a wide span of neurotransmitter receptors activities including their trafficking, sorting, stability, residence lifetime at the cell surface, endocytosis, recycling, and synaptic clustering. This review summarizes the current knowledge on the palmitoylation of neurotransmitter receptors and its role in the regulation of receptors functions as well as in the control of different kinds of physiological and pathological behavior.
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Abstract
Voltage-gated sodium channels (VGSCs) are critical determinants of excitability. The properties of VGSCs are thought to be tightly controlled. However, VGSCs are also subjected to extensive modifications. Multiple posttranslational modifications that covalently modify VGSCs in neurons and muscle have been identified. These include, but are not limited to, phosphorylation, ubiquitination, palmitoylation, nitrosylation, glycosylation, and SUMOylation. Posttranslational modifications of VGSCs can have profound impact on cellular excitability, contributing to normal and abnormal physiology. Despite four decades of research, the complexity of VGSC modulation is still being determined. While some modifications have similar effects on the various VGSC isoforms, others have isoform-specific interactions. In addition, while much has been learned about how individual modifications can impact VGSC function, there is still more to be learned about how different modifications can interact. Here we review what is known about VGSC posttranslational modifications with a focus on the breadth and complexity of the regulatory mechanisms that impact VGSC properties.
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Affiliation(s)
- Zifan Pei
- Department of Biology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA.,Department of Pharmacology and Toxicology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Yanling Pan
- Medical Neuroscience Graduate Program, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Theodore R Cummins
- Department of Biology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA. .,Medical Neuroscience Graduate Program, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA.
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Borroni MV, Vallés AS, Barrantes FJ. The lipid habitats of neurotransmitter receptors in brain. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2662-2670. [PMID: 27424801 DOI: 10.1016/j.bbamem.2016.07.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 06/05/2016] [Accepted: 07/12/2016] [Indexed: 12/17/2022]
Abstract
Neurotransmitter receptors, the macromolecules specialized in decoding the chemical signals encrypted in the chemical signaling mechanism in the nervous system, occur either at the somatic cell surface of chemically excitable cells or at specialized subcellular structures, the synapses. Synapses have lipid compositions distinct from the rest of the cell membrane, suggesting that neurotransmitter receptors and their scaffolding and adaptor protein partners require specific lipid habitats for optimal operation. In this review we discuss some paradigmatic cases of neurotransmitter receptor-lipid interactions, highlighting the chemical nature of the intervening lipid species and providing examples of the receptor mechanisms affected by interaction with lipids. The focus is on the effects of cholesterol, glycerophospholipids and covalent fatty acid acylation on neurotransmitter receptors. We also briefly discuss the role of lipid phase states involving lateral heterogeneities of the host membrane known to modulate membrane transport, protein sorting and signaling. Modulation of neurotransmitter receptors by lipids occurs at multiple levels, affecting a wide span of activities including their trafficking, sorting, stability, residence lifetime at the cell surface, endocytosis, and recycling, among other important functional properties at the synapse.
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Affiliation(s)
- María Virginia Borroni
- Instituto de Tecnología en Polímeros y Nanotecnología (ITPN) Av. Las Heras 2214 C1127AAQ Buenos Aires Argentina
| | - Ana Sofía Vallés
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, B8000FWB Bahía Blanca, Argentina
| | - Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Biomedical Research Institute, UCA-CONICET, Faculty of Medical Sciences, Catholic University of Argentina, Av. Alicia Moreau de Justo 1600, C1107AFF Buenos Aires, Argentina.
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10
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Engidawork E, Aradska J, Lubec G. Neurotransmitter receptor complexes: methods for bioanalysis, their potentials and limitations. Rev Neurosci 2016; 27:111-33. [DOI: 10.1515/revneuro-2015-0034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 08/11/2015] [Indexed: 12/15/2022]
Abstract
AbstractNeurotransmitter receptors are key elements for brain function, but work so far has been focusing on the individual receptor subunits. It is, however, the receptor complexes that execute work rather than the subunits; of course, the multitude of possible combinations of the many receptors forming homomeric or heteromeric complexes is hampering studies. Moreover, not only receptors are observed in the complexes but also their corresponding protein kinases, phosphatases, and anchoring proteins, to name a few. Studying receptor complexes is still an analytical challenge. Thus far, no methods exist to unequivocally characterize or even quantify these assemblies. Major problems and limitations for the analysis exist, such as solubility, as the use of detergents is critical and may dissociate the receptor complexes as well as their separation in the native state. Gel-based techniques are able to separate and semiquantitatively quantify receptor complexes by subsequent immunochemical methods but do not allow the characterization of complex components. Immunoprecipitation methods are highly dependent on antibody availability and specificity, and the result of coimmunoprecipitation does not verify the direct physical interaction of proteins in the immunoprecipitate. Antibody shift assays are suitable to identify individual known proteins within a complex as are immunogold electron microscopic techniques and energy transfer technologies. Most techniques are simply showing the proximity of proteins rather than their physical interaction. Although fluorescence correlation spectroscopy is a promising technique, the use for quantification or comparing biological samples is limited. A lot of work remains to be done to provide tools for the characterization and quantification of receptor complexes in the brain.
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Affiliation(s)
| | - Jana Aradska
- 1Department of Pediatrics, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria
| | - Gert Lubec
- 3Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
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11
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Regulation of nicotinic acetylcholine receptors in Alzheimer׳s disease: a possible role of chaperones. Eur J Pharmacol 2015; 755:34-41. [PMID: 25771456 DOI: 10.1016/j.ejphar.2015.02.047] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 02/15/2015] [Accepted: 02/22/2015] [Indexed: 12/25/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) seem to play an integral role in the progress and/or prevention of Alzheimer׳s diseases (AD). Functional abnormalities and problems in biogenesis and trafficking of nAChRs are two major culprits in AD; on the other hand, chaperones modulate post-translational changes in nAChRs. Moreover, they indirectly regulate nAChRs by controlling AD-related proteins such as tau and amyloid beta (Aβ). In this review, we go through recent studies which are showing that chaperones modulate the expression of nAChRs in a subtype-specific manner and explain how AD progress is affected by nAChRs chaperoning.
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12
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Barrantes FJ. Cell-surface translational dynamics of nicotinic acetylcholine receptors. Front Synaptic Neurosci 2014; 6:25. [PMID: 25414663 PMCID: PMC4220116 DOI: 10.3389/fnsyn.2014.00025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 10/08/2014] [Indexed: 12/20/2022] Open
Abstract
Synapse efficacy heavily relies on the number of neurotransmitter receptors available at a given time. In addition to the equilibrium between the biosynthetic production, exocytic delivery and recycling of receptors on the one hand, and the endocytic internalization on the other, lateral diffusion and clustering of receptors at the cell membrane play key roles in determining the amount of active receptors at the synapse. Mobile receptors traffic between reservoir compartments and the synapse by thermally driven Brownian motion, and become immobilized at the peri-synaptic region or the synapse by: (a) clustering mediated by homotropic inter-molecular receptor–receptor associations; (b) heterotropic associations with non-receptor scaffolding proteins or the subjacent cytoskeletal meshwork, leading to diffusional “trapping,” and (c) protein-lipid interactions, particularly with the neutral lipid cholesterol. This review assesses the contribution of some of these mechanisms to the supramolecular organization and dynamics of the paradigm neurotransmitter receptor of muscle and neuronal cells -the nicotinic acetylcholine receptor (nAChR). Currently available information stemming from various complementary biophysical techniques commonly used to interrogate the dynamics of cell-surface components is critically discussed. The translational mobility of nAChRs at the cell surface differs between muscle and neuronal receptors in terms of diffusion coefficients and residence intervals at the synapse, which cover an ample range of time regimes. A peculiar feature of brain α7 nAChR is its ability to spend much of its time confined peri-synaptically, vicinal to glutamatergic (excitatory) and GABAergic (inhibitory) synapses. An important function of the α7 nAChR may thus be visiting the territories of other neurotransmitter receptors, differentially regulating the dynamic equilibrium between excitation and inhibition, depending on its residence time in each domain.
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Affiliation(s)
- Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Institute of Biomedical Research, Faculty of Medical Sciences, Pontifical Catholic University of Argentina-National Scientific and Technical Research Council Buenos Aires, Argentina
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13
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Abstract
Protein S-acylation, the reversible covalent fatty-acid modification of cysteine residues, has emerged as a dynamic posttranslational modification (PTM) that controls the diversity, life cycle, and physiological function of numerous ligand- and voltage-gated ion channels. S-acylation is enzymatically mediated by a diverse family of acyltransferases (zDHHCs) and is reversed by acylthioesterases. However, for most ion channels, the dynamics and subcellular localization at which S-acylation and deacylation cycles occur are not known. S-acylation can control the two fundamental determinants of ion channel function: (1) the number of channels resident in a membrane and (2) the activity of the channel at the membrane. It controls the former by regulating channel trafficking and the latter by controlling channel kinetics and modulation by other PTMs. Ion channel function may be modulated by S-acylation of both pore-forming and regulatory subunits as well as through control of adapter, signaling, and scaffolding proteins in ion channel complexes. Importantly, cross-talk of S-acylation with other PTMs of both cysteine residues by themselves and neighboring sites of phosphorylation is an emerging concept in the control of ion channel physiology. In this review, I discuss the fundamentals of protein S-acylation and the tools available to investigate ion channel S-acylation. The mechanisms and role of S-acylation in controlling diverse stages of the ion channel life cycle and its effect on ion channel function are highlighted. Finally, I discuss future goals and challenges for the field to understand both the mechanistic basis for S-acylation control of ion channels and the functional consequence and implications for understanding the physiological function of ion channel S-acylation in health and disease.
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Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD Scotland, UK
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14
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Filchakova O, McIntosh JM. Functional expression of human α9* nicotinic acetylcholine receptors in X. laevis oocytes is dependent on the α9 subunit 5' UTR. PLoS One 2013; 8:e64655. [PMID: 23717646 PMCID: PMC3661583 DOI: 10.1371/journal.pone.0064655] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/18/2013] [Indexed: 11/19/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing the α9 subunit are expressed in a wide variety of non-neuronal tissues ranging from immune cells to breast carcinomas. The α9 subunit is able to assemble into a functional homomeric nAChR and also co-assemble with the α10 subunit into functional heteromeric nAChRs. Despite the increasing awareness of the important roles of this subunit in vertebrates, the study of human α9-containing nAChRs has been severely limited by difficulties in its expression in heterologous systems. In Xenopus laevis oocytes, functional expression of human α9α10 nAChRs is very low compared to that of rat α9α10 nAChRs. When oocytes were co-injected with cRNA of α9 and α10 subunits of human versus those of rat, oocytes with the rat α9 human α10 combination had an ∼-fold higher level of acetylcholine-gated currents (IACh) than those with the human α9 rat α10 combination, suggesting difficulties with human α9 expression. When the ratio of injected human α9 cRNA to human α10 cRNA was increased from 1∶1 to 5∶1, IACh increased 36-fold (from 142±23 nA to 5171±748 nA). Functional expression of human α9-containing receptors in oocytes was markedly improved by appending the 5′-untranslated region of alfalfa mosaic virus RNA4 to the 5′-leader sequence of the α9 subunit cRNA. This increased the functional expression of homomeric human α9 receptors by 70-fold (from 7±1 nA to 475±158 nA) and of human α9α10 heteromeric receptors by 80-fold (from 113±62 nA to 9192±1137 nA). These findings indicate the importance of the composition of the 5′ untranslated leader sequence for expression of α9-containing nAChRs.
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Affiliation(s)
- Olena Filchakova
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, Utah, United States of America.
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Miwa JM, Lester HA, Walz A. Optimizing cholinergic tone through lynx modulators of nicotinic receptors: implications for plasticity and nicotine addiction. Physiology (Bethesda) 2012; 27:187-99. [PMID: 22875450 DOI: 10.1152/physiol.00002.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The cholinergic system underlies both adaptive (learning and memory) and nonadaptive (addiction and dependency) behavioral changes through its ability to shape and regulate plasticity. Protein modulators such as lynx family members can fine tune the activity of the cholinergic system and contribute to the graded response of the cholinergic system, stabilizing neural circuitry through direct interaction with nicotinic receptors. Release of this molecular brake can unmask cholinergic-dependent mechanisms in the brain. Lynx proteins have the potential to provide top-down control over plasticity mechanisms, including addictive propensity. If this is indeed the case, then, what regulates the regulator? Transcriptional changes of lynx genes in response to pharmacological, physiological, and pathological alterations are explored in this review.
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Affiliation(s)
- Julie M Miwa
- California Institute of Technology, Pasadena, California, USA.
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Amici SA, McKay SB, Wells GB, Robson JI, Nasir M, Ponath G, Anand R. A highly conserved cytoplasmic cysteine residue in the α4 nicotinic acetylcholine receptor is palmitoylated and regulates protein expression. J Biol Chem 2012; 287:23119-27. [PMID: 22593584 DOI: 10.1074/jbc.m111.328294] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptor (nAChR) cell surface expression levels are modulated during nicotine dependence and multiple disorders of the nervous system, but the mechanisms underlying nAChR trafficking remain unclear. To determine the role of cysteine residues, including their palmitoylation, on neuronal α4 nAChR subunit maturation and cell surface trafficking, the cysteines in the two intracellular regions of the receptor were replaced with serines using site-directed mutagenesis. Palmitoylation is a post-translational modification that regulates membrane receptor trafficking and function. Metabolic labeling with [(3)H]palmitate determined that the cysteine in the cytoplasmic loop between transmembrane domains 1 and 2 (M1-M2) is palmitoylated. When this cysteine is mutated to a serine, producing a depalmitoylated α4 nAChR, total protein expression decreases, but surface expression increases compared with wild-type α4 levels, as determined by Western blotting and enzyme-linked immunoassays, respectively. The cysteines in the M3-M4 cytoplasmic loop do not appear to be palmitoylated, but replacing all of the cysteines in the loop with serines increases total and cell surface expression. When all of the intracellular cysteines in both loops are mutated to serines, there is no change in total expression, but there is an increase in surface expression. Calcium accumulation assays and high affinity binding for [(3)H]epibatidine determined that all mutants retain functional activity. Thus, our results identify a novel palmitoylation site on cysteine 273 in the M1-M2 loop of the α4 nAChR and determine that cysteines in both intracellular loops are regulatory factors in total and cell surface protein expression of the α4β2 nAChR.
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Affiliation(s)
- Stephanie A Amici
- Department of Pharmacology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
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Ballesta JJ, del Pozo C, Castelló-Banyuls J, Faura CC. Selective down-regulation of α4β2 neuronal nicotinic acetylcholine receptors in the brain of uremic rats with cognitive impairment. Exp Neurol 2012; 236:28-33. [PMID: 22510484 DOI: 10.1016/j.expneurol.2012.03.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 01/31/2012] [Accepted: 03/29/2012] [Indexed: 01/02/2023]
Abstract
Cognitive impairment is common in patients with chronic kidney disease. Brain nicotinic acetylcholine receptors modulate cognitive functions, such as learning and memory. Pharmacological cholinergic enhancement is useful in patients with cognitive dysfunction. The major nicotinic acetylcholine receptor subtypes in the brain are heteromeric α4β2 and homomeric α7 receptors. To study the involvement of neuronal acetylcholine receptors in cognitive impairment in uremic rats, bilateral nephrectomy was performed. 24 weeks after nephrectomy, memory was assessed using the one trial step-down inhibitory avoidance test. Neuronal nicotinic acetylcholine receptors in the brain were studied by radioligand binding, immunoprecipitation, Western blot and sucrose gradient experiments. We demonstrated that rats with severe renal failure show disorders of short term memory. Long term memory was not altered in these rats. The number of functional α4β2 heteromeric neuronal nicotinic receptors was decreased in the brains of rats with severe renal failure. There was a significant correlation between the degree of renal impairment and the number of heteromeric nicotinic acetylcholine receptors in the brain. The down-regulation of functional α4β2 receptors in the brains of rats with severe renal failure was not due to a reduction of α4 or β2 subunit proteins. The number of α7 homomeric neuronal nicotinic acetylcholine receptors was not altered. These findings may have important clinical significance for the management of cognitive impairment in patients with chronic kidney disease.
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Affiliation(s)
- Juan J Ballesta
- Institute of Neurosciences, CSIC-Universidad Miguel Hernández, Avenida Ramon y Cajal, 03550 San Juan de Alicante, Spain.
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Brunzell DH, McIntosh JM. Alpha7 nicotinic acetylcholine receptors modulate motivation to self-administer nicotine: implications for smoking and schizophrenia. Neuropsychopharmacology 2012; 37:1134-43. [PMID: 22169946 PMCID: PMC3306875 DOI: 10.1038/npp.2011.299] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Individuals diagnosed with schizophrenia have an exceptionally high risk for tobacco dependence. Postmortem studies show that these individuals have significant reductions in α7 nicotinic acetylcholine receptors (nAChRs) in several brain areas. Decreased α7-mediated function might not only be linked to schizophrenia but also to increased tobacco consumption. The purpose of this study was to determine whether pharmacological blockade of α7 nAChRs would increase motivation of rats to intravenously self-administer nicotine (NIC) during a progressive ratio schedule of reinforcement (PR). Before PR, rats received local infusions of 0, 10, or 20 pmol of a selective α7 nAChR antagonist, α-conotoxin ArIB [V11L,V16D] (ArIB) into the nucleus accumbens (NAc) shell or the anterior cingulate cortex, brain areas that contribute to motivation for drug reward. We additionally sought to determine whether local infusion of 0, 10, or 40 nmol of a selective α7 nAChR agonist, PNU 282987, into these brain areas would decrease motivation for NIC use. Infusion of ArIB into the NAc shell and anterior cingulate cortex resulted in a significant increase in active lever pressing, breakpoints, and NIC intake, suggesting that a decrease in α7 nAChR function increases motivation to work for NIC. In contrast, PNU 282987 infusion resulted in reductions in these measures when administered into the NAc shell, but had no effect after administration into the anterior cingulate cortex. These data identify reduction of α7 nAChR function as a potential mechanism for elevated tobacco use in schizophrenia and also identify activation of α7 nAChRs as a potential strategy for tobacco cessation therapy.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
| | - J Michael McIntosh
- Department of Psychiatry, University of Utah, Salt Lake City, UT, USA,Department of Biology, University of Utah, Salt Lake City, UT, USA
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Nicotine-induced upregulation of native neuronal nicotinic receptors is caused by multiple mechanisms. J Neurosci 2012; 32:2227-38. [PMID: 22323734 DOI: 10.1523/jneurosci.5438-11.2012] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Nicotine causes changes in brain nicotinic acetylcholine receptors (nAChRs) during smoking that initiate addiction. Nicotine-induced upregulation is the long-lasting increase in nAChR radioligand binding sites in brain resulting from exposure. The mechanisms causing upregulation are not established. Many different mechanisms have been reported with the assumption that there is a single underlying cause. Using live rat cortical neurons, we examined for the first time how exposure and withdrawal of nicotine shape the kinetics of native α4β2-containing nAChR upregulation in real time. Upregulation kinetics demonstrates that at least two different mechanisms underlie this phenomenon. First, a transient upregulation occurs that rapidly reverses, faster than nAChR degradation, and corresponds to nAChR conformational changes as assayed by conformational-dependent, subunit-specific antibodies. Second, a long-lasting process occurs correlating with increases in nAChR numbers caused by decreased proteasomal subunit degradation. Previous radioligand binding measurements to brain tissue have measured the second process and largely missed the first. We conclude that nicotine-induced upregulation is composed of multiple processes occurring at different rates with different underlying causes.
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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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Liu S, Babcock MS, Bode J, Chang JS, Fischer HD, Garlick RL, Gill GS, Lund ET, Margolis BJ, Mathews WR, Rogers BN, Wolfe M, Groppi V, Baldwin ET. Affinity purification of a chimeric nicotinic acetylcholine receptor in the agonist and antagonist bound states. Protein Expr Purif 2011; 79:102-10. [DOI: 10.1016/j.pep.2011.05.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 05/19/2011] [Accepted: 05/26/2011] [Indexed: 10/18/2022]
Affiliation(s)
- Shenping Liu
- Pfizer Inc., Pfizer Global Research and Development, Groton, CT 06340, United States.
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Abstract
Protein S-palmitoylation, the reversible thioester linkage of a 16-carbon palmitate lipid to an intracellular cysteine residue, is rapidly emerging as a fundamental, dynamic, and widespread post-translational mechanism to control the properties and function of ligand- and voltage-gated ion channels. Palmitoylation controls multiple stages in the ion channel life cycle, from maturation to trafficking and regulation. An emerging concept is that palmitoylation is an important determinant of channel regulation by other signaling pathways. The elucidation of enzymes controlling palmitoylation and developments in proteomics tools now promise to revolutionize our understanding of this fundamental post-translational mechanism in regulating ion channel physiology.
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Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.
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Alkondon M, Pereira EFR, Eisenberg HM, Kajii Y, Schwarcz R, Albuquerque EX. Age dependency of inhibition of alpha7 nicotinic receptors and tonically active N-methyl-D-aspartate receptors by endogenously produced kynurenic acid in the brain. J Pharmacol Exp Ther 2011; 337:572-82. [PMID: 21270133 DOI: 10.1124/jpet.110.177386] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In the mouse hippocampus normal levels of kynurenic acid (KYNA), a neuroactive metabolite synthesized in astrocytes primarily by kynurenine aminotransferase II (KAT II)-catalyzed transamination of L-kynurenine, maintain a degree of tonic inhibition of α7 nicotinic acetylcholine receptors (nAChRs). The present in vitro study was designed to test the hypothesis that α7 nAChR activity decreases when endogenous production of KYNA increases. Incubation (2-7 h) of rat hippocampal slices with kynurenine (200 μM) resulted in continuous de novo synthesis of KYNA. Kynurenine conversion to KYNA was significantly decreased by the KAT II inhibitor (S)-(-)-9-(4-aminopiperazine-1-yl)-8-fluoro-3-methyl-6-oxo-2,3,5,6-tetrahydro-4H-1-oxa-3a-azaphenalene-5carboxylic acid (BFF122) (100 μM) and was more effective in slices from postweaned than preweaned rats. Incubation of slices from postweaned rats with kynurenine inhibited α7 nAChRs and extrasynaptic N-methyl-D-aspartate receptors (NMDARs) on CA1 stratum radiatum interneurons. These effects were attenuated by BFF122 and mimicked by exogenously applied KYNA (200 μM). Exposure of human cerebral cortical slices to kynurenine also inhibited α7 nAChRs. The α7 nAChR sensitivity to KYNA is age-dependent, because neither endogenously produced nor exogenously applied KYNA inhibited α7 nAChRs in slices from preweaned rats. In these slices, kynurenine-derived KYNA also failed to inhibit extrasynaptic NMDARs, which could, however, be inhibited by exogenously applied KYNA. In slices from preweaned and postweaned rats, glutamatergic synaptic currents were not affected by endogenously produced KYNA, but were inhibited by exogenously applied KYNA. These results suggest that in the mature brain α7 nAChRs and extrasynaptic NMDARs are in close apposition to KYNA release sites and, thereby, readily accessible to inhibition by endogenously produced KYNA.
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Affiliation(s)
- Manickavasagom Alkondon
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, 10 S. Pine St., Baltimore, MD 21201, USA
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