1
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Kunzmann P, Krumbach JH, Saponaro A, Moroni A, Thiel G, Hamacher K. Anisotropic Network Analysis of Open/Closed HCN4 Channel Advocates Asymmetric Subunit Cooperativity in cAMP Modulation of Gating. J Chem Inf Model 2024; 64:4727-4738. [PMID: 38830626 DOI: 10.1021/acs.jcim.4c00360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are opened in an allosteric manner by membrane hyperpolarization and cyclic nucleotides such as cAMP. Because of conflicting reports from experimental studies on whether cAMP binding to the four available binding sites in the channel tetramer operates cooperatively in gating, we employ here a computational approach as a promising route to examine ligand-induced conformational changes after binding to individual sites. By combining an elastic network model (ENM) with linear response theory (LRT) for modeling the apo-holo transition of the cyclic nucleotide-binding domain (CNBD) in HCN channels, we observe a distinct pattern of cooperativity matching the "positive-negative-positive" cooperativity reported from functional studies. This cooperativity pattern is highly conserved among HCN subtypes (HCN4, HCN1), but only to a lesser extent visible in structurally related channels, which are only gated by voltage (KAT1) or cyclic nucleotides (TAX4). This suggests an inherent cooperativity between subunits in HCN channels as part of a ligand-triggered gating mechanism in these channels.
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Affiliation(s)
- Patrick Kunzmann
- Department of Biology, Computational Biology & Simulation, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
| | - Jan H Krumbach
- Department of Biology, Computational Biology & Simulation, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
| | - Andrea Saponaro
- Department of Pharmacology and Biomolecular Sciences, University of Milano, via Balzaretti 9, 20133 Milano, Italy
| | - Anna Moroni
- Department of Biosciences, Ion Channel Biophysics, University of Milan, via Celoria 26, 20133 Milan, Italy
| | - Gerhard Thiel
- Department of Biology, Membrane Biophysics, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
- Centre for Synthetic Biology, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
| | - Kay Hamacher
- Department of Biology, Computational Biology & Simulation, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
- Centre for Synthetic Biology, TU Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
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2
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Yadav N, Thelma BK. Deletion induced splicing in RIC3 drives nicotinic acetylcholine receptor regulation with implications for endoplasmic reticulum stress in human astrocytes. Glia 2023; 71:1217-1232. [PMID: 36602087 DOI: 10.1002/glia.24333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/25/2022] [Accepted: 12/22/2022] [Indexed: 01/06/2023]
Abstract
Nicotinic acetylcholine receptor (nAChR) dysregulation in astrocytes is reported in neurodegenerative disorders. Modulation of nAChRs through agonists confers protection to astrocytes from stress but regulation of chaperones involved in proteostasis with pathological implications is unclear. Resistance to inhibitors of cholinesterase 3 (RIC3), a potential chaperone of nAChRs is poorly studied in humans. We characterized RIC3 in astrocytes derived from an isogenic wild-type and Cas9 edited "del" human iPSC line harboring a 25 bp homozygous deletion in exon2. Altered RIC3 transcript ratio due to deletion induced splicing and an unexpected gain of α7nAChR expression were observed in "del" astrocytes. Transcriptome analysis showed higher expression of neurotransmitter/G-protein coupled receptors mediated by cAMP and calcium/calmodulin-dependent kinase signaling with increased cytokines/glutamate secretion. Functional implications examined using tunicamycin induced ER stress in wild-type astrocyte stress model showed cell cycle arrest, RIC3 upregulation, reduction in α7nAChR membrane levels but increased α4nAChR membrane expression. Conversely, tunicamycin-treated "del" astrocytes showed a comparatively higher α4nAChR membrane expression and upsurged cAMP signaling. Furthermore, reduced expression of stress markers CHOP, phospho-PERK and lowered XBP1 splicing in western blot and qPCR, validated by proteome-based pathway analysis indicated lowered disease severity. Findings indicate (i) a complex RNA regulatory mechanism via exonic deletion induced splicing; (ii) RIC-3 as a disordered protein having contrasting effects on co-expressed nAChR subtypes under basal/stress conditions; and (iii) RIC3 as a potential drug target against ER stress in astrocytes for neurodegenerative/nicotine-related brain disorders. Cellular rescue mechanism through deletion induced exon skipping may encourage ASO-based therapies for tauopathies.
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Affiliation(s)
- Navneesh Yadav
- Department of Genetics, University of Delhi South Campus, New Delhi, India
| | - B K Thelma
- Department of Genetics, University of Delhi South Campus, New Delhi, India
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3
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Zhao L, Mühleisen TW, Pelzer DI, Burger B, Beins EC, Forstner AJ, Herms S, Hoffmann P, Amunts K, Palomero-Gallagher N, Cichon S. Relationships between neurotransmitter receptor densities and expression levels of their corresponding genes in the human hippocampus. Neuroimage 2023; 273:120095. [PMID: 37030412 PMCID: PMC10167541 DOI: 10.1016/j.neuroimage.2023.120095] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 03/02/2023] [Accepted: 04/05/2023] [Indexed: 04/08/2023] Open
Abstract
Neurotransmitter receptors are key molecules in signal transmission, their alterations are associated with brain dysfunction. Relationships between receptors and their corresponding genes are poorly understood, especially in humans. We combined in vitro receptor autoradiography and RNA sequencing to quantify, in the same tissue samples (7 subjects), the densities of 14 receptors and expression levels of their corresponding 43 genes in the Cornu Ammonis (CA) and dentate gyrus (DG) of human hippocampus. Significant differences in receptor densities between both structures were found only for metabotropic receptors, whereas significant differences in RNA expression levels mostly pertained ionotropic receptors. Receptor fingerprints of CA and DG differ in shapes but have similar sizes; the opposite holds true for their "RNA fingerprints", which represent the expression levels of multiple genes in a single area. In addition, the correlation coefficients between receptor densities and corresponding gene expression levels vary widely and the mean correlation strength was weak-to-moderate. Our results suggest that receptor densities are not only controlled by corresponding RNA expression levels, but also by multiple regionally specific post-translational factors.
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4
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Askland KD, Strong D, Wright MN, Moore JH. The Translational Machine: A novel machine-learning approach to illuminate complex genetic architectures. Genet Epidemiol 2021; 45:485-536. [PMID: 33942369 DOI: 10.1002/gepi.22383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/05/2021] [Accepted: 03/23/2021] [Indexed: 11/08/2022]
Abstract
The Translational Machine (TM) is a machine learning (ML)-based analytic pipeline that translates genotypic/variant call data into biologically contextualized features that richly characterize complex variant architectures and permit greater interpretability and biological replication. It also reduces potentially confounding effects of population substructure on outcome prediction. The TM consists of three main components. First, replicable but flexible feature engineering procedures translate genome-scale data into biologically informative features that appropriately contextualize simple variant calls/genotypes within biological and functional contexts. Second, model-free, nonparametric ML-based feature filtering procedures empirically reduce dimensionality and noise of both original genotype calls and engineered features. Third, a powerful ML algorithm for feature selection is used to differentiate risk variant contributions across variant frequency and functional prediction spectra. The TM simultaneously evaluates potential contributions of variants operative under polygenic and heterogeneous models of genetic architecture. Our TM enables integration of biological information (e.g., genomic annotations) within conceptual frameworks akin to geneset-/pathways-based and collapsing methods, but overcomes some of these methods' limitations. The full TM pipeline is executed in R. Our approach and initial findings from its application to a whole-exome schizophrenia case-control data set are presented. These TM procedures extend the findings of the primary investigation and yield novel results.
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Affiliation(s)
- Kathleen D Askland
- Waypoint Centre for Mental Health Care Penetanguishene, University of Toronto, Toronto, Ontario, Canada
| | - David Strong
- Department of Family Medicine and Public Health, University of California San Diego, San Diego, California, USA
| | - Marvin N Wright
- Department Biometry and Data Management, Leibniz Institute for Prevention Research and Epidemiology - BIPS GmbH, Germany
| | - Jason H Moore
- Department of Biostatistics, Epidemiology, & Informatics, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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5
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Annaert W, Kaether C. Bring it back, bring it back, don't take it away from me - the sorting receptor RER1. J Cell Sci 2020; 133:133/17/jcs231423. [PMID: 32873699 DOI: 10.1242/jcs.231423] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The quote "bring it back, bring it back, don't take it away from me" from Queen's Love of my life describes the function of the sorting receptor RER1, a 23 kDa protein with four transmembrane domains (TMDs) that localizes to the intermediate compartment and the cis-Golgi. From there it returns escaped proteins that are not supposed to leave the endoplasmic reticulum (ER) back to it. Unique about RER1 is its ability to recognize its ligands through binding motifs in TMDs. Among its substrates are ER-resident proteins, as well as unassembled subunits of multimeric complexes that are retrieved back into the ER, this way guarding the full assembly of their respective complexes. The basic mechanisms for RER1-dependent retrieval have been already elucidated some years ago in yeast. More recently, several important cargoes of RER1 have been described in mammalian cells, and the in vivo role of RER1 is being unveiled by using mouse models. In this Review, we give an overview of the cell biology of RER1 in different models, discuss its controversial role in the brain and provide an outlook on future directions for RER1 research.
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Affiliation(s)
- Wim Annaert
- VIB Center for Brain and Disease Research & KU Leuven, Department of Neurosciences, Gasthuisberg, B-3000 Leuven, Belgium
| | - Christoph Kaether
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, 07745 Jena, Germany
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6
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Schwenk J, Fakler B. Building of AMPA‐type glutamate receptors in the endoplasmic reticulum and its implication for excitatory neurotransmission. J Physiol 2020; 599:2639-2653. [DOI: 10.1113/jp279025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 07/21/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Jochen Schwenk
- Institute of Physiology, Faculty of Medicine University of Freiburg Hermann‐Herder‐Str. 7 Freiburg 79104 Germany
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine University of Freiburg Hermann‐Herder‐Str. 7 Freiburg 79104 Germany
- Signalling Research Centres BIOSS and CIBSS Schänzlestr. 18 Freiburg 79104 Germany
- Center for Basics in NeuroModulation Breisacherstr. 4 Freiburg 79106 Germany
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7
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Jain AR, Britton ZT, Markwalter CE, Robinson AS. Improved ligand-binding- and signaling-competent human NK2R yields in yeast using a chimera with the rat NK2R C-terminus enable NK2R-G protein signaling platform. Protein Eng Des Sel 2020; 32:459-469. [PMID: 32400863 DOI: 10.1093/protein/gzaa009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 03/09/2020] [Accepted: 04/16/2020] [Indexed: 02/07/2023] Open
Abstract
The tachykinin 2 receptor (NK2R) plays critical roles in gastrointestinal, respiratory and mental disorders and is a well-recognized target for therapeutic intervention. To date, therapeutics targeting NK2R have failed to meet regulatory agency approval due in large part to the limited characterization of the receptor-ligand interaction and downstream signaling. Herein, we report a protein engineering strategy to improve ligand-binding- and signaling-competent human NK2R that enables a yeast-based NK2R signaling platform by creating chimeras utilizing sequences from rat NK2R. We demonstrate that NK2R chimeras incorporating the rat NK2R C-terminus exhibited improved ligand-binding yields and downstream signaling in engineered yeast strains and mammalian cells, where observed yields were better than 4-fold over wild type. This work builds on our previous studies that suggest exchanging the C-termini of related and well-expressed family members may be a general protein engineering strategy to overcome limitations to ligand-binding and signaling-competent G protein-coupled receptor yields in yeast. We expect these efforts to result in NK2R drug candidates with better characterized signaling properties.
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Affiliation(s)
- Abhinav R Jain
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA
| | - Zachary T Britton
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,AstraZeneca, Antibody Discovery and Protein Engineering, Gaithersburg, MD 20878, USA
| | - Chester E Markwalter
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Anne S Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA.,Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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8
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An ER Assembly Line of AMPA-Receptors Controls Excitatory Neurotransmission and Its Plasticity. Neuron 2019; 104:680-692.e9. [DOI: 10.1016/j.neuron.2019.08.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 06/28/2019] [Accepted: 08/20/2019] [Indexed: 11/15/2022]
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9
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The glycine hinge of transmembrane segment 2 modulates the subcellular localization and gating properties in TREK channels. Biochem Biophys Res Commun 2017; 490:1125-1131. [DOI: 10.1016/j.bbrc.2017.06.200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 06/30/2017] [Indexed: 01/09/2023]
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10
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Findeisen F, Campiglio M, Jo H, Abderemane-Ali F, Rumpf CH, Pope L, Rossen ND, Flucher BE, DeGrado WF, Minor DL. Stapled Voltage-Gated Calcium Channel (Ca V) α-Interaction Domain (AID) Peptides Act As Selective Protein-Protein Interaction Inhibitors of Ca V Function. ACS Chem Neurosci 2017; 8:1313-1326. [PMID: 28278376 PMCID: PMC5481814 DOI: 10.1021/acschemneuro.6b00454] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
![]()
For many voltage-gated
ion channels (VGICs), creation of a properly functioning ion channel
requires the formation of specific protein–protein interactions
between the transmembrane pore-forming subunits and cystoplasmic accessory
subunits. Despite the importance of such protein–protein interactions
in VGIC function and assembly, their potential as sites for VGIC modulator
development has been largely overlooked. Here, we develop meta-xylyl (m-xylyl) stapled peptides that
target a prototypic VGIC high affinity protein–protein interaction,
the interaction between the voltage-gated calcium channel (CaV) pore-forming subunit α-interaction domain (AID) and
cytoplasmic β-subunit (CaVβ). We show using
circular dichroism spectroscopy, X-ray crystallography, and isothermal
titration calorimetry that the m-xylyl staples enhance
AID helix formation are structurally compatible with native-like AID:CaVβ interactions and reduce the entropic penalty associated
with AID binding to CaVβ. Importantly, electrophysiological
studies reveal that stapled AID peptides act as effective inhibitors
of the CaVα1:CaVβ interaction
that modulate CaV function in an CaVβ
isoform-selective manner. Together, our studies provide a proof-of-concept
demonstration of the use of protein–protein interaction inhibitors
to control VGIC function and point to strategies for improved AID-based
CaV modulator design.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Daniel L. Minor
- Molecular Biophysics & Integrated Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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11
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Cho CH, Lee YS, Kim E, Hwang EM, Park JY. Physiological functions of the TRPM4 channels via protein interactions. BMB Rep 2015; 48:1-5. [PMID: 25441424 PMCID: PMC4345635 DOI: 10.5483/bmbrep.2015.48.1.252] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Indexed: 11/23/2022] Open
Abstract
Transient Receptor Potential, Melastatin-related, member 4 (TRPM4) channels are Ca2+-activated Ca2+-impermeable cation channels. These channels are expressed in various types of mammalian tissues including the brain and are implicated in many diverse physiological and pathophysiological conditions. In the past several years, the trafficking processes and regulatory mechanism of these channels and their interacting proteins have been uncovered. Here in this minireview, we summarize the current understanding of the trafficking mechanism of TRPM4 channels on the plasma membrane as well as heteromeric complex formation via protein interactions. We also describe physiological implications of protein-TRPM4 interactions and suggest TRPM4 channels as therapeutic targets in many related diseases. [BMB Reports 2015; 48(1): 1-5]
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Affiliation(s)
- Chang-Hoon Cho
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703, Korea
| | - Young-Sun Lee
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791; Department of Physiology, Institute of Health Science and Medical Research Center for Neural Dysfunction, Gyeongsang National University School of Medicine, Jinju 660-751, Korea
| | - Eunju Kim
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703; Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791; Neuroscience Program, University of Science and Technology (UST), Daejeon 305-350, Korea
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703, Korea
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12
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Garcia-Elias A, Berna-Erro A, Rubio-Moscardo F, Pardo-Pastor C, Mrkonjić S, Sepúlveda RV, Vicente R, González-Nilo F, Valverde MA. Interaction between the Linker, Pre-S1, and TRP Domains Determines Folding, Assembly, and Trafficking of TRPV Channels. Structure 2015; 23:1404-1413. [PMID: 26146187 DOI: 10.1016/j.str.2015.05.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 05/14/2015] [Accepted: 05/25/2015] [Indexed: 11/26/2022]
Abstract
Functional transient receptor potential (TRP) channels result from the assembly of four subunits. Here, we show an interaction between the pre-S1, TRP, and the ankyrin repeat domain (ARD)-S1 linker domains of TRPV1 and TRPV4 that is essential for proper channel assembly. Neutralization of TRPV4 pre-S1 K462 resulted in protein retention in the ER, defective glycosylation and trafficking, and unresponsiveness to TRPV4-activating stimuli. Similar results were obtained with the equivalent mutation in TRPV1 pre-S1. Molecular dynamics simulations revealed that TRPV4-K462 generated an alternating hydrogen network with E745 (TRP box) and D425 (pre-S1 linker), and that K462Q mutation affected subunit folding. Consistently, single TRPV4-E745A or TRPV4-D425A mutations moderately affected TRPV4 biogenesis while double TRPV4-D425A/E745A mutation resumed the TRPV4-K462Q phenotype. Thus, the interaction between pre-S1, TRP, and linker domains is mandatory to generate a structural conformation that allows the contacts between adjacent subunits to promote correct assembly and trafficking to the plasma membrane.
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Affiliation(s)
- Anna Garcia-Elias
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Alejandro Berna-Erro
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Fanny Rubio-Moscardo
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Carlos Pardo-Pastor
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Sanela Mrkonjić
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Romina V Sepúlveda
- Universidad Andrés Bello, Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Av. República 239, Santiago 8320000, Chile; Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile
| | - Rubén Vicente
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain
| | - Fernando González-Nilo
- Universidad Andrés Bello, Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Av. República 239, Santiago 8320000, Chile; Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile
| | - Miguel A Valverde
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona 08003, Spain.
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13
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The role of protein-protein interactions in the intracellular traffic of the potassium channels TASK-1 and TASK-3. Pflugers Arch 2015; 467:1105-20. [PMID: 25559843 DOI: 10.1007/s00424-014-1672-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
Abstract
The intracellular transport of membrane proteins is controlled by trafficking signals: Short peptide motifs that mediate the contact with COPI, COPII or various clathrin-associated coat proteins. In addition, many membrane proteins interact with accessory proteins that are involved in the sorting of these proteins to different intracellular compartments. In the K2P channels, TASK-1 and TASK-3, the influence of protein-protein interactions on sorting decisions has been studied in some detail. Both TASK paralogues interact with the adaptor protein 14-3-3; TASK-1 interacts, in addition, with the adaptor protein p11 (S100A10) and the endosomal SNARE protein syntaxin-8. The role of these interacting proteins in controlling the intracellular traffic of the channels and the underlying molecular mechanisms are summarised in this review. In the case of 14-3-3, the interacting protein masks a retention signal in the C-terminus of the channel; in the case of p11, the interacting protein carries a retention signal that localises the channel to the endoplasmic reticulum; and in the case of syntaxin-8, the interacting protein carries an endocytosis signal that complements an endocytosis signal of the channel. These examples illustrate some of the mechanisms by which interacting proteins may determine the itinerary of a membrane protein within a cell and suggest that the intracellular traffic of membrane proteins may be adapted to the specific functions of that protein by multiple protein-protein interactions.
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14
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Bagriantsev SN, Chatelain FC, Clark KA, Alagem N, Reuveny E, Minor DL. Tethered protein display identifies a novel Kir3.2 (GIRK2) regulator from protein scaffold libraries. ACS Chem Neurosci 2014; 5:812-22. [PMID: 25028803 PMCID: PMC4176385 DOI: 10.1021/cn5000698] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
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Use of randomized peptide libraries
to evolve molecules with new
functions provides a means for developing novel regulators of protein
activity. Despite the demonstrated power of such approaches for soluble
targets, application of this strategy to membrane systems, such as
ion channels, remains challenging. Here, we have combined libraries
of a tethered protein scaffold with functional selection in yeast
to develop a novel activator of the G-protein-coupled mammalian inwardly
rectifying potassium channel Kir3.2 (GIRK2). We show that the novel
regulator, denoted N5, increases Kir3.2 (GIRK2) basal activity by
inhibiting clearance of the channel from the cellular surface rather
than affecting the core biophysical properties of the channel. These
studies establish the tethered protein display strategy as a means
to create new channel modulators and highlight the power of approaches
that couple randomized libraries with direct selections for functional
effects. Our results further underscore the possibility for the development
of modulators that influence channel function by altering cell surface
expression densities rather than by direct action on channel biophysical
parameters. The use of tethered library selection strategies coupled
with functional selection bypasses the need for a purified target
and is likely to be applicable to a range of membrane protein systems.
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Affiliation(s)
| | | | | | - Noga Alagem
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eitan Reuveny
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Daniel L. Minor
- Physical
Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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15
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Isacoff EY, Jan LY, Minor DL. Conduits of life's spark: a perspective on ion channel research since the birth of neuron. Neuron 2013; 80:658-74. [PMID: 24183018 DOI: 10.1016/j.neuron.2013.10.040] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Heartbeats, muscle twitches, and lightning-fast thoughts are all manifestations of bioelectricity and rely on the activity of a class of membrane proteins known as ion channels. The basic function of an ion channel can be distilled into, "The hole opens. Ions go through. The hole closes." Studies of the fundamental mechanisms by which this process happens and the consequences of such activity in the setting of excitable cells remains the central focus of much of the field. One might wonder after so many years of detailed poking at such a seemingly simple process, is there anything left to learn?
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Affiliation(s)
- Ehud Y Isacoff
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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16
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Li S, Nai Q, Lipina TV, Roder JC, Liu F. α7nAchR/NMDAR coupling affects NMDAR function and object recognition. Mol Brain 2013; 6:58. [PMID: 24360204 PMCID: PMC3878138 DOI: 10.1186/1756-6606-6-58] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/12/2013] [Indexed: 02/03/2023] Open
Abstract
The α7 nicotinic acetylcholine receptor (nAchR) and NMDA glutamate receptor (NMDAR) are both ligand-gated ion channels permeable to Ca2+ and Na+. Previous studies have demonstrated functional modulation of NMDARs by nAchRs, although the molecular mechanism remains largely unknown. We have previously reported that α7nAchR forms a protein complex with the NMDAR through a protein-protein interaction. We also developed an interfering peptide that is able to disrupt the α7nAchR-NMDAR complex and blocks cue-induced reinstatement of nicotine-seeking in rat models of relapse. In the present study, we investigated whether the α7nAchR-NMDAR interaction is responsible for the functional modulation of NMDAR by α7nAchR using both electrophysiological and behavioral tests. We have found that activation of α7nAchR upregulates NMDAR-mediated whole cell currents and LTP of mEPSC in cultured hippocampal neurons, which can be abolished by the interfering peptide that disrupts the α7nAchR-NMDAR interaction. Moreover, administration of the interfering peptide in mice impairs novel object recognition but not Morris water maze performance. Our results suggest that α7nAchR/NMDAR coupling may selectively affect some aspects of learning and memory.
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Affiliation(s)
| | | | | | | | - Fang Liu
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
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Adomaviciene A, Smith KJ, Garnett H, Tammaro P. Putative pore-loops of TMEM16/anoctamin channels affect channel density in cell membranes. J Physiol 2013; 591:3487-505. [PMID: 23613533 DOI: 10.1113/jphysiol.2013.251660] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The recently identified TMEM16/anoctamin protein family includes Ca(2+)-activated anion channels (TMEM16A, TMEM16B), a cation channel (TMEM16F) and proteins with unclear function. TMEM16 channels consist of eight putative transmembrane domains (TMs) with TM5-TM6 flanking a re-entrant loop thought to form the pore. In TMEM16A this region has also been suggested to contain residues involved in Ca(2+) binding. The role of the putative pore-loop of TMEM16 channels was investigated using a chimeric approach. Heterologous expression of either TMEM16A or TMEM16B resulted in whole-cell anion currents with very similar conduction properties but distinct kinetics and degrees of sensitivity to Ca(2+). Furthermore, whole-cell currents mediated by TMEM16A channels were ∼six times larger than TMEM16B-mediated currents. Replacement of the putative pore-loop of TMEM16A with that of TMEM16B (TMEM16A-B channels) reduced the currents by ∼six-fold, while the opposite modification (TMEM16B-A channels) produced a ∼six-fold increase in the currents. Unexpectedly, these changes were not secondary to variations in channel gating by Ca(2+) or voltage, nor were they due to changes in single-channel conductance. Instead, they depended on the number of functional channels present on the plasma membrane. Generation of additional, smaller chimeras within the putative pore-loop of TMEM16A and TMEM16B led to the identification of a region containing a non-canonical trafficking motif. Chimeras composed of the putative pore-loop of TMEM16F transplanted into the TMEM16A protein scaffold did not conduct anions or cations. These data suggest that the putative pore-loop does not form a complete, transferable pore domain. Furthermore, our data reveal an unexpected role for the putative pore-loop of TMEM16A and TMEM16B channels in the control of the whole-cell Ca(2+)-activated Cl(-) conductance.
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Affiliation(s)
- Aiste Adomaviciene
- Faculty of Life Sciences, The University of Manchester, 46 Grafton Street, Manchester M13 9NT, UK
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18
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Abstract
A thermodynamic approach to studying allosterically regulated ion channels such as the large-conductance voltage- and Ca(2+)-dependent (BK) channel is presented, drawing from principles originally introduced to describe linkage phenomena in hemoglobin. In this paper, linkage between a principal channel component and secondary elements is derived from a four-state thermodynamic cycle. One set of parallel legs in the cycle describes the "work function," or the free energy required to activate the principal component. The second are "lever operations" activating linked elements. The experimental embodiment of this linkage cycle is a plot of work function versus secondary force, whose asymptotes are a function of the parameters (displacements and interaction energies) of an allosteric network. Two essential work functions play a role in evaluating data from voltage-clamp experiments. The first is the conductance Hill energy W(H)([g]), which is a "local" work function for pore activation, and is defined as kT times the Hill transform of the conductance (G-V) curve. The second is the electrical capacitance energy W(C)([q]), representing "global" gating charge displacement, and is equal to the product of total gating charge per channel times the first moment (V(M)) of normalized capacitance (slope of Q-V curve). Plots of W(H)([g]) and W(C)([q]) versus voltage and Ca(2+) potential can be used to measure thermodynamic parameters in a model-independent fashion of the core gating constituents (pore, voltage-sensor, and Ca(2+)-binding domain) of BK channel. The method is easily generalized for use in studying other allosterically regulated ion channels. The feasibility of performing linkage analysis from patch-clamp data were explored by simulating gating and ionic currents of a 17-particle model BK channel in response to a slow voltage ramp, which yielded interaction energies deviating from their given values in the range of 1.3 to 7.2%.
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Lester HA, Miwa JM, Srinivasan R. Psychiatric drugs bind to classical targets within early exocytotic pathways: therapeutic effects. Biol Psychiatry 2012; 72:907-15. [PMID: 22771239 PMCID: PMC6167061 DOI: 10.1016/j.biopsych.2012.05.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 04/23/2012] [Accepted: 05/21/2012] [Indexed: 11/17/2022]
Abstract
The classical targets for antipsychotic and antidepressant drugs are G protein-coupled receptors and neurotransmitter transporters, respectively. Full therapeutic actions of these drugs require several weeks. We show how therapeutic effects may eventually accrue after existing therapeutic ligands bind to these classical targets, not on the plasma membrane but rather within endoplasmic reticulum (ER) and cis-Golgi. Consequences of such binding may include pharmacological chaperoning: the nascent drug targets are stabilized against degradation and can therefore exit the ER more readily. Another effect may be matchmaking: heterodimers and homodimers of the target form and can more readily exit the ER. Summarizing recent data for nicotinic receptors, we explain how such effects could lead to reduced ER stress and to a decreased unfolded protein response, including changes in gene activation and protein synthesis. In effects not directly related to cellular stress, escorting would allow increased ER exit and trafficking of known associated proteins, as well as other proteins such as growth factors and their receptors, producing both cell-autonomous and non-cell-autonomous effects. Axonal transport of relevant proteins may underlie the several weeks required for full therapy. In contrast, the antidepressant effects of ketamine and other N-methyl-D-aspartate receptor ligands, which occur within <2 hours, could arise from dendritically localized intracellular binding, followed by chaperoning, matchmaking, escorting, and reduced ER stress. Thus, the effects of intracellular binding extend beyond proteostasis of the targets themselves and involve pathways distinct from ion channel and G protein activation. We propose experimental tests and note pathophysiological correlates.
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Affiliation(s)
- Henry A Lester
- Division of Biology, California Institute of Technology, Pasadena, California.
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Tanabe C, Maeda T, Zou K, Liu J, Liu S, Nakajima T, Komano H. The ubiquitin ligase synoviolin up-regulates amyloid β production by targeting a negative regulator of γ-secretase, Rer1, for degradation. J Biol Chem 2012; 287:44203-11. [PMID: 23129766 DOI: 10.1074/jbc.m112.365296] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alzheimer's disease is characterized by the deposition of Aβ, which is generated from the amyloid precursor protein through its cleavage by β- and γ-secretases. The γ-secretase complex component nicastrin (NCT) plays significant roles in the assembly and proper trafficking of the γ-secretase complex and in the recognition of amyloid precursor protein. NCT is incorporated into the γ-secretase complex in the endoplasmic reticulum (ER) and glycosylated in the Golgi. In contrast, unassembled NCT is retrieved or retained in the ER by the protein Retention in endoplasmic reticulum 1 (Rer1). We reported previously that synoviolin (Syvn), an E3 ubiquitin ligase, degrades NCT and affects the generation of Aβ. Here, we examined in more detail the effect of Syvn on the generation of Aβ. We found that overexpression of a dominant negative form of Syvn (C307A mutant) and a Syvn-RNAi decreased the generation of Aβ. These results indicate that the ubiquitin ligase activity of Syvn up-regulates the generation of Aβ. We hypothesized, therefore, that Syvn regulates the assembly or localization of the γ-secretase complex by ubiquitinating Rer1, resulting in its subsequent degradation. Our findings that the level of Rer1 was increased in Syvn knockout fibroblasts because of inhibition of its degradation support this hypothesis. Moreover, we found that Rer1 interacts with Syvn in the ER, is ubiquitinated by Syvn, and is then degraded via the proteasome or lysosomal pathways. Finally, we showed that localization of mature NCT to the plasma membrane as well as γ-secretase complex levels are decreased in fibroblasts of Syvn knockout mice. Thus, it is likely that Syvn regulates the assembly of the γ-secretase complex via the degradation of Rer1, which results in the generation of Aβ.
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Affiliation(s)
- Chiaki Tanabe
- Department of Neuroscience, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Shiwa, Iwate 028-3694, Japan
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21
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Larisch N, Schulze C, Galione A, Dietrich P. An N-Terminal Dileucine Motif Directs Two-Pore Channels to the Tonoplast of Plant Cells. Traffic 2012; 13:1012-22. [DOI: 10.1111/j.1600-0854.2012.01366.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 04/06/2012] [Accepted: 04/10/2012] [Indexed: 12/23/2022]
Affiliation(s)
- Nina Larisch
- Department Biology; Friedrich-Alexander-Universität Erlangen-Nürnberg, Molecular Plant Physiology and Erlangen Center of Plant Science; Staudtstrasse 5; 91058; Erlangen; Germany
| | - Christina Schulze
- Department Biology; Friedrich-Alexander-Universität Erlangen-Nürnberg, Molecular Plant Physiology and Erlangen Center of Plant Science; Staudtstrasse 5; 91058; Erlangen; Germany
| | - Antony Galione
- Department of Pharmacology; Oxford University; Oxford; OX1 3QT; UK
| | - Petra Dietrich
- Department Biology; Friedrich-Alexander-Universität Erlangen-Nürnberg, Molecular Plant Physiology and Erlangen Center of Plant Science; Staudtstrasse 5; 91058; Erlangen; Germany
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22
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Devaraneni PK, Devereaux JJ, Valiyaveetil FI. In vitro folding of KvAP, a voltage-gated K+ channel. Biochemistry 2011; 50:10442-50. [PMID: 22044112 DOI: 10.1021/bi2012965] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this contribution, we report in vitro folding of the archaebacterial voltage-gated K(+) channel, K(v)AP. We show that in vitro folding of the K(v)AP channel from the extensively unfolded state requires lipid vesicles and that the refolded channel is biochemically and functionally similar to the native channel. The in vitro folding process is slow at room temperature, and the folding yield depends on the composition of the lipid bilayer. The major factor influencing refolding is temperature, and almost quantitative refolding of the K(v)AP channel is observed at 80 °C. To differentiate between insertion into the bilayer and folding within the bilayer, we developed a cysteine protection assay. Using this assay, we demonstrate that insertion of the unfolded protein into the bilayer is relatively fast at room temperature and independent of lipid composition, suggesting that temperature and bilayer composition influence folding within the bilayer. Further, we demonstrate that in vitro folding provides an effective method for obtaining high yields of the native channel. Our studies suggest that the K(v)AP channel provides a good model system for investigating the folding of a multidomain integral membrane protein.
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Affiliation(s)
- Prasanna K Devaraneni
- The Program in Chemical Biology, Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon 97239, United States
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23
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Fassler M, Li X, Kaether C. Polar transmembrane-based amino acids in presenilin 1 are involved in endoplasmic reticulum localization, Pen2 protein binding, and γ-secretase complex stabilization. J Biol Chem 2011; 286:38390-38396. [PMID: 21914807 PMCID: PMC3207410 DOI: 10.1074/jbc.m111.252429] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 09/02/2011] [Indexed: 11/06/2022] Open
Abstract
γ-Secretase is composed of the four membrane proteins presenilin, nicastrin, Pen2, and Aph1. These four proteins assemble in a coordinated and regulated manner into a high molecular weight complex. The subunits constitute a total of 19 transmembrane domains (TMD), with many carrying important amino acids involved in catalytic activity, interaction with other subunits, or in ER retention/retrieval of unassembled subunits. We here focus on TMD4 of presenilin 1 (PS1) and show that a number of polar amino acids are critical for γ-secretase assembly and function. An asparagine, a threonine, and an aspartate form a polar interface important for endoplasmic reticulum retention/retrieval. A single asparagine in TMD4 of PS1 is involved in a protein-protein interaction by binding to another asparagine in Pen2. Intriguingly, a charged aspartate in TMD4 is critical for γ-secretase activity, most likely by stabilizing the newly formed complex.
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Affiliation(s)
- Matthias Fassler
- Leibniz Institut für Altersforschung-Fritz Lipmann Institut, 07743 Jena, Germany
| | - Xiaolin Li
- Leibniz Institut für Altersforschung-Fritz Lipmann Institut, 07743 Jena, Germany
| | - Christoph Kaether
- Leibniz Institut für Altersforschung-Fritz Lipmann Institut, 07743 Jena, Germany.
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24
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González-González IM, Konopacki FA, Rocca DL, Doherty AJ, Jaafari N, Wilkinson KA, Henley JM. Kainate receptor trafficking. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/wmts.23] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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25
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Rossmann M, Sukumaran M, Penn AC, Veprintsev DB, Babu MM, Greger IH. Subunit-selective N-terminal domain associations organize the formation of AMPA receptor heteromers. EMBO J 2011; 30:959-71. [PMID: 21317873 DOI: 10.1038/emboj.2011.16] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 01/10/2011] [Indexed: 02/02/2023] Open
Abstract
The assembly of AMPA-type glutamate receptors (AMPARs) into distinct ion channel tetramers ultimately governs the nature of information transfer at excitatory synapses. How cells regulate the formation of diverse homo- and heteromeric AMPARs is unknown. Using a sensitive biophysical approach, we show that the extracellular, membrane-distal AMPAR N-terminal domains (NTDs) orchestrate selective routes of heteromeric assembly via a surprisingly wide spectrum of subunit-specific association affinities. Heteromerization is dominant, occurs at the level of the dimer, and results in a preferential incorporation of the functionally critical GluA2 subunit. Using a combination of structure-guided mutagenesis and electrophysiology, we further map evolutionarily variable hotspots in the NTD dimer interface, which modulate heteromerization capacity. This 'flexibility' of the NTD not only explains why heteromers predominate but also how GluA2-lacking, Ca(2+)-permeable homomers could form, which are induced under specific physiological and pathological conditions. Our findings reveal that distinct NTD properties set the stage for the biogenesis of functionally diverse pools of homo- and heteromeric AMPAR tetramers.
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Affiliation(s)
- Maxim Rossmann
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK
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26
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Waschk DEJ, Fabian A, Budde T, Schwab A. Dual-color quantum dot detection of a heterotetrameric potassium channel (hKCa3.1). Am J Physiol Cell Physiol 2011; 300:C843-9. [PMID: 21228320 DOI: 10.1152/ajpcell.00053.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Potassium channels play a key role in establishing the cell membrane potential and are expressed ubiquitously. Today, more than 70 mammalian K(+) channel genes are known. The diversity of K(+) channels is further increased by the fact that different K(+) channel family members may assemble to form heterotetramers. We present a method based on fluorescence microscopy to determine the subunit composition of a tetrameric K(+) channel. We generated artificial "heteromers" of the K(+) channel hK(Ca)3.1 by coexpressing two differently tagged hK(Ca)3.1 constructs containing either an extracellular hemagglutinin (HA) or an intracellular V5 epitope. hK(Ca)3.1 channel subunits were detected in the plasma membrane of MDCK-F cells or HEK293 cells by labeling the extra- and intracellular epitopes with differently colored quantum dots (QDs). As previously shown for the extracellular part of hK(Ca)3.1 channels, its intracellular domain can also bind only one QD label at a time. When both channel subunits were coexpressed, 27.5 ± 1.8% and 24.9 ± 2.1% were homotetramers consisting of HA- and V5-tagged subunits, respectively. 47.6 ± 3.2% of the channels were heteromeric and composed of both subunits. The frequency distribution of HA- and V5-tagged homo- and heteromeric hK(Ca)3.1 channels is reminiscent of the binomial distribution (a + b)(2) = a(2) + 2ab + b(2). Along these lines, our findings are consistent with the notion that hK(Ca)3.1 channels are assembled from two homomeric dimers and not randomly from four independent subunits. We anticipate that our technique will be applicable to other heteromeric membrane proteins, too.
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Sheridan JT, Worthington EN, Yu K, Gabriel SE, Hartzell HC, Tarran R. Characterization of the oligomeric structure of the Ca(2+)-activated Cl- channel Ano1/TMEM16A. J Biol Chem 2010; 286:1381-8. [PMID: 21056985 DOI: 10.1074/jbc.m110.174847] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the Anoctamin (Ano)/TMEM16A family have recently been identified as essential subunits of the Ca(2+)-activated chloride channel (CaCC). For example, Ano1 is highly expressed in multiple tissues including airway epithelia, where it acts as an apical conduit for transepithelial Cl(-) secretion and helps regulate lung liquid homeostasis and mucus clearance. However, little is known about the oligomerization of this protein in the plasma membrane. Thus, utilizing mCherry- and eGFP-tagged Ano1 constructs, we conducted biochemical and Förster resonance energy transfer (FRET)-based experiments to determine the quaternary structure of Ano1. FRET and co-immunoprecipitation studies revealed that tagged Ano1 subunits directly associated before they reached the plasma membrane. This association was not altered by changes in cytosolic Ca(2+), suggesting that this is a fixed interaction. To determine the oligomeric structure of Ano1, we performed chemical cross-linking, non-denaturing PAGE, and electromobility shift assays, which revealed that Ano1 exists as a dimer. These data are the first to probe the quaternary structure of Ano1. Understanding the oligomeric nature of Ano1 is an essential step in the development of therapeutic drugs that could be useful in the treatment of cystic fibrosis.
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Affiliation(s)
- John T Sheridan
- Department of Cell and Molecular Physiology, University of North Carolina, North Carolina, Chapel Hill 27599, USA
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28
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Mathie A, Rees KA, El Hachmane MF, Veale EL. Trafficking of neuronal two pore domain potassium channels. Curr Neuropharmacol 2010; 8:276-86. [PMID: 21358977 PMCID: PMC3001220 DOI: 10.2174/157015910792246146] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 01/18/2010] [Accepted: 01/18/2010] [Indexed: 01/05/2023] Open
Abstract
The activity of two pore domain potassium (K2P) channels regulates neuronal excitability and cell firing. Post-translational regulation of K2P channel trafficking to the membrane controls the number of functional channels at the neuronal membrane affecting the functional properties of neurons. In this review, we describe the general features of K channel trafficking from the endoplasmic reticulum (ER) to the plasma membrane via the Golgi apparatus then focus on established regulatory mechanisms for K2P channel trafficking. We describe the regulation of trafficking of TASK channels from the ER or their retention within the ER and consider the competing hypotheses for the roles of the chaperone proteins 14-3-3, COP1 and p11 in these processes and where these proteins bind to TASK channels. We also describe the localisation of TREK channels to particular regions of the neuronal membrane and the involvement of the TREK channel binding partners AKAP150 and Mtap2 in this localisation. We describe the roles of other K2P channel binding partners including Arf6, EFA6 and SUMO for TWIK1 channels and Vpu for TASK1 channels. Finally, we consider the potential importance of K2P channel trafficking in a number of disease states such as neuropathic pain and cancer and the protection of neurons from ischemic damage. We suggest that a better understanding of the mechanisms and regulations that underpin the trafficking of K2P channels to the plasma membrane and to localised regions therein may considerably enhance the probability of future therapeutic advances in these areas.
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Affiliation(s)
- Alistair Mathie
- Medway School of Pharmacy, Universities of Kent and Greenwich at Medway, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK
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29
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Araud T, Wonnacott S, Bertrand D. Associated proteins: The universal toolbox controlling ligand gated ion channel function. Biochem Pharmacol 2010; 80:160-9. [PMID: 20346921 DOI: 10.1016/j.bcp.2010.03.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 03/02/2010] [Accepted: 03/15/2010] [Indexed: 02/06/2023]
Abstract
Ligand gated ion channels are integral multimeric membrane proteins that can detect with high sensitivity the presence of a specific transmitter in the extracellular space and transduce this signal into an ion flux. While these receptors are widely expressed in the nervous system, their expression is not limited to neurons or their postsynaptic targets but extends to non-neuronal cells where they participate in many physiological responses. Cells have developed complex regulatory mechanisms allowing for the precise control and modulation of ligand gated ion channels. In this overview the roles of accessory subunits and associated proteins in these regulatory mechanisms are reviewed and their relevance illustrated by examples at different ligand gated ion channel types, with emphasis on nicotinic acetylcholine receptors. Dysfunction of ligand gated ion channels can result in neuromuscular, neurological or psychiatric disorders. A better understanding of the precise function of associated proteins and how they impact on ligand gated ion channels will provide new therapeutic opportunities for clinical intervention.
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30
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MLC1 trafficking and membrane expression in astrocytes: Role of caveolin-1 and phosphorylation. Neurobiol Dis 2010; 37:581-95. [DOI: 10.1016/j.nbd.2009.11.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 10/23/2009] [Accepted: 11/12/2009] [Indexed: 12/19/2022] Open
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31
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Fassler M, Zocher M, Klare S, de la Fuente AG, Scheuermann J, Capell A, Haass C, Valkova C, Veerappan A, Schneider D, Kaether C. Masking of transmembrane-based retention signals controls ER export of gamma-secretase. Traffic 2009; 11:250-8. [PMID: 19958468 DOI: 10.1111/j.1600-0854.2009.01014.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
gamma-Secretase is critically involved in the Notch pathway and in Alzheimer's disease. The four subunits of gamma-secretase assemble in the endoplasmic reticulum (ER) and unassembled subunits are retained/retrieved to the ER by specific signals. We here describe a novel ER-retention/retrieval signal in the transmembrane domain (TMD) 4 of presenilin 1, a subunit of gamma-secretase. TMD4 also is essential for complex formation, conferring a dual role for this domain. Likewise, TMD1 of Pen2 is bifunctional as well. It carries an ER-retention/retrieval signal and is important for complex assembly by binding to TMD4. The two TMDs directly interact with each other and mask their respective ER-retention/retrieval signals, allowing surface transport of reporter proteins. Our data suggest a model how assembly of Pen2 into the nascent gamma-secretase complex could mask TMD-based ER-retention/retrieval signals to allow plasma membrane transport of fully assembled gamma-secretase.
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Affiliation(s)
- Matthias Fassler
- Leibniz Institut für Altersforschung-Fritz Lipmann Institut, 07743 Jena, Germany
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32
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Saheki Y, Bargmann CI. Presynaptic CaV2 calcium channel traffic requires CALF-1 and the alpha(2)delta subunit UNC-36. Nat Neurosci 2009; 12:1257-65. [PMID: 19718034 PMCID: PMC2805665 DOI: 10.1038/nn.2383] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Accepted: 07/09/2009] [Indexed: 12/18/2022]
Abstract
Presynaptic voltage-gated calcium channels provide calcium for synaptic vesicle exocytosis. We show here that a green fluorescent protein-tagged alpha(1) subunit of the Caenorhabditis elegans CaV2 channel, UNC-2, is localized to presynaptic active zones of sensory and motor neurons. Synaptic localization of CaV2 requires the alpha(2)delta subunit UNC-36 and CALF-1 (Calcium Channel Localization Factor-1), a neuronal transmembrane protein that localizes to the endoplasmic reticulum. In calf-1 mutants, UNC-2 is retained in the endoplasmic reticulum, but other active-zone components and synaptic vesicles are delivered to synapses. Acute induction of calf-1 mobilizes preexisting UNC-2 for delivery to synapses, consistent with a direct trafficking role. The alpha(2)delta subunit UNC-36 is likewise required for exit of UNC-2 from endoplasmic reticulum but has additional functions. Genetic and cell biological interactions suggest that CALF-1 couples intracellular traffic to functional maturation of CaV2 presynaptic calcium channels.
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Affiliation(s)
- Yasunori Saheki
- Howard Hughes Medical Institute and Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York, USA
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33
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Mikosch M, Käberich K, Homann U. ER export of KAT1 is correlated to the number of acidic residues within a triacidic motif. Traffic 2009; 10:1481-7. [PMID: 19659502 DOI: 10.1111/j.1600-0854.2009.00962.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
For a number of ion channels, including the potassium (K(+)) inward rectifying channel from Arabidopsis thaliana (KAT1), diacidic endoplasmic reticulum (ER) export motifs have been identified. These motifs consist of two acidic amino acids (aspartate (D) and/or glutamate (E)) separated by any amino acid. To specify the role of single acidic amino acids for efficiency of ER export, we analysed a sequence of KAT1 that included the originally identified diacidic ER export motif (DxE) plus an additional D just upstream of the diacidic motif. Analysis of single, double and triple mutations of the acidic amino acids of the DxDxE motif revealed a gradual reduction of ER export depending on the number of mutated acidic residues. The amount of reduction in ER export was not related to the position, but only to the number of mutated acidic amino acids. These results show that a triacidic motif is essential for efficient ER export of KAT1. Function of the triacidic motif probably involves cooperative binding to Sec24.
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Affiliation(s)
- Melanie Mikosch
- Institute of Botany, Technische Universität Darmstadt, Darmstadt, Germany
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Dopico AM, Lovinger DM. Acute alcohol action and desensitization of ligand-gated ion channels. Pharmacol Rev 2009; 61:98-114. [PMID: 19270242 DOI: 10.1124/pr.108.000430] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ethanol exerts its biological actions through multiple receptors, including ion channels. Ion channels that are sensitive to pharmacologically relevant ethanol concentrations constitute a heterogeneous set, including structurally unrelated proteins solely sharing the property that their gating is regulated by a ligand(s). Receptor desensitization is almost universal among these channels, and its modulation by ethanol may be a crucial aspect of alcohol pharmacology and effects in the body. We review the evidence documenting interactions between ethanol and ionotropic receptor desensitization, and the contribution of this interaction to overall ethanol action on channel function. In some cases, such as type 3 serotonin, nicotinic acetylcholine, GABA-A, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors, ethanol actions on apparent desensitization play a significant role in acute drug action on receptor function. In a few cases, mutagenesis helped to identify different areas within a receptor protein that differentially sense n-alcohols, resulting in differential modulation of receptor desensitization. However, desensitization of a receptor is linked to a variety of biochemical processes that may alter protein conformation, such as the lipid microenvironment, post-translational channel modification, and channel subunit composition, the relative contribution of these processes to ethanol interactions with channel desensitization remains unclear. Understanding interactions between ethanol and ionotropic receptor desensitization may help to explain different ethanol actions 1) when ethanol is evaluated in vitro on cloned channel proteins, 2) under physiological or pathological conditions or in distinct cell domains with modified ligand concentration and/or receptor conformation. Finally, receptor desensitization is likely to participate in molecular and, possibly, behavioral tolerance to ethanol, which is thought to contribute to the risk of alcoholism.
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Affiliation(s)
- Alex M Dopico
- Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163-0001, USA.
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Congenital long QT syndrome caused by the F275S KCNQ1 mutation: mechanism of impaired channel function. Biochem Biophys Res Commun 2009; 380:127-31. [PMID: 19167356 DOI: 10.1016/j.bbrc.2009.01.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Accepted: 01/13/2009] [Indexed: 01/22/2023]
Abstract
Congenital long QT syndrome is characterized by a prolongation of ventricular repolarization and recurrent episodes of life-threatening ventricular tachyarrhythmias, often leading to sudden death. We previously identified a missense mutation F275S located within the S5 transmembrane domain of the KCNQ1 ion channel in a Chinese family with long QT syndrome. We used oocyte expression of the KCNQ1 polypeptide to study the effects of the F275S mutation on channel properties. Expression of the F275 mutant, or co-expression with the wild-type S275 polypeptide, significantly decreased channel current amplitudes. Moreover, the F275S substitution decreased the rates of channel activation and deactivation. In transfected HEK293 cells fluorescence microscopy revealed that the F275S mutation perturbed the subcelluar localization of the ion channel. These results indicate that the F275S KCNQ1 mutation leads to impaired polypeptide trafficking that in turn leads to reduction of channel ion currents and altered gating kinetics.
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Mutant Prion Protein Expression Causes Motor and Memory Deficits and Abnormal Sleep Patterns in a Transgenic Mouse Model. Neuron 2008; 60:598-609. [DOI: 10.1016/j.neuron.2008.09.008] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 07/22/2008] [Accepted: 09/04/2008] [Indexed: 11/18/2022]
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Penn AC, Williams SR, Greger IH. Gating motions underlie AMPA receptor secretion from the endoplasmic reticulum. EMBO J 2008; 27:3056-68. [PMID: 18923416 DOI: 10.1038/emboj.2008.222] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Accepted: 09/29/2008] [Indexed: 12/13/2022] Open
Abstract
Ion channel biogenesis involves an intricate interplay between subunit folding and assembly. Channel stoichiometries vary and give rise to diverse functions, which impacts on neuronal signalling. AMPA glutamate receptor (AMPAR) assembly is modulated by RNA processing. Here, we provide mechanistic insight into this process. First, we show that a single alternatively spliced residue within the ligand-binding domain alters AMPAR secretion from the ER. Local contacts differ between Leu758 of the GluR2-flop splice form as compared with the flip-specific Val758, which is transmitted globally to alter resensitization kinetics. Detailed biochemical and functional analysis of mutants suggest that AMPARs sample the gating cascade prior to ER export. Irreversibly locking the receptor within various states of the cascade severely attenuates ER transit. Alternative RNA processing by contrast, shifts equilibria between transition states reversibly and thereby modulates secretion kinetics. These data reveal how RNA processing tunes AMPAR biogenesis, and imply that gating transitions in the ER determine iGluR secretory traffic.
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Affiliation(s)
- Andrew C Penn
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK
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