1
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Cnpy3 2xHA mice reveal neuronal expression of Cnpy3 in the brain. J Neurosci Methods 2023; 383:109730. [PMID: 36280087 DOI: 10.1016/j.jneumeth.2022.109730] [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: 08/09/2022] [Revised: 10/04/2022] [Accepted: 10/17/2022] [Indexed: 11/30/2022]
Abstract
BACKGROUND Identification of biallelic CNPY3 mutations in patients with epileptic encephalopathy and abnormal electroencephalography findings of Cnpy3 knock-out mice have indicated that the loss of CNPY3 function causes neurological disorders such as epilepsy. However, the basic property of CNPY3 in the brain remains unclear. NEW METHOD We generated C-terminal 2xHA-tag knock-in Cnpy3 mice by i-GONAD in vivo genome editing system to investigate the expression and function of Cnpy3 in the mouse brain. RESULTS 2xHA-tagged Cnpy3 was confirmed by immunoblot analysis using anti-HA and CNPY3 antibodies, although HA tagging caused the decreased Cnpy3 protein level. Immunohistochemical analysis of Cnpy32xHA knock-in mice showed that Cnpy3-2xHA was predominantly expressed in the neuron. In addition, Cnpy3 and Cnpy3-2xHA were both localized in the endoplasmic reticulum and synaptosome and showed age-dependent expression changes in the brain. COMPARISON WITH EXISTING METHODS Conventional Cnpy3 antibodies could not allow us to investigate the distribution of Cnpy3 expression in the brain, while HA-tagging revealed the expression of CNPY3 in neuronal cells. CONCLUSIONS Taken together, we demonstrated that Cnpy32xHA knock-in mice would be useful to further elucidate the property of Cnpy3 in brain function and neurological disorders.
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2
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Shin JH, Lanz M, Smolka MB, Dörr T. Characterization of an anti-FLAG antibody binding protein in V. cholerae. Biochem Biophys Res Commun 2020; 528:493-498. [PMID: 32505345 DOI: 10.1016/j.bbrc.2020.05.169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 05/24/2020] [Indexed: 11/30/2022]
Abstract
FLAG-tags are commonly used for protein abundance measurements and for identification of protein-protein interactions in living cells. We have observed that the cholera pathogen Vibrio cholerae encodes a FLAG-antibody-reactive protein and identified this protein as an outer membrane porin, Porin4, which contains a sequence very similar to the 3xFLAG epitope tag. We have demonstrated the binding affinity of the conserved peptide sequence (called Porin 4 tag) in Porin4 against monoclonal anti-FLAG M2 antibody. In addition, we created a porin4 deletion mutant, which can be used for background-less FLAG antibody detection experiments.
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Affiliation(s)
- Jung-Ho Shin
- Weill Institute for Cell and Molecular Biology, Cornell, University, Ithaca, NY, 14853, USA; Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
| | - Michael Lanz
- Weill Institute for Cell and Molecular Biology, Cornell, University, Ithaca, NY, 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Marcus B Smolka
- Weill Institute for Cell and Molecular Biology, Cornell, University, Ithaca, NY, 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell, University, Ithaca, NY, 14853, USA; Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA; Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY, 14853, USA.
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3
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Generating therapeutic monoclonal antibodies to complex multi-spanning membrane targets: Overcoming the antigen challenge and enabling discovery strategies. Methods 2020; 180:111-126. [PMID: 32422249 DOI: 10.1016/j.ymeth.2020.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/21/2020] [Accepted: 05/13/2020] [Indexed: 12/17/2022] Open
Abstract
Complex integral membrane proteins, which are embedded in the cell surface lipid bilayer by multiple transmembrane spanning helices, encompass families of proteins which are important target classes for drug discovery. These protein families include G protein-coupled receptors, ion channels and transporters. Although these proteins have typically been targeted by small molecule drugs and peptides, the high specificity of monoclonal antibodies offers a significant opportunity to selectively modulate these target proteins. However, it remains the case that isolation of antibodies with desired pharmacological function(s) has proven difficult due to technical challenges in preparing membrane protein antigens suitable to support antibody drug discovery. In this review recent progress in defining strategies for generation of membrane protein antigens is outlined. We also highlight antibody isolation strategies which have generated antibodies which bind the membrane protein and modulate the protein function.
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4
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Tabor GT, Park JM, Murphy JG, Hu JH, Hoffman DA. A novel bungarotoxin binding site-tagged construct reveals MAPK-dependent Kv4.2 trafficking. Mol Cell Neurosci 2019; 98:121-130. [PMID: 31212013 DOI: 10.1016/j.mcn.2019.06.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 06/11/2019] [Accepted: 06/13/2019] [Indexed: 02/07/2023] Open
Abstract
Kv4.2 voltage-gated K+ channel subunits, the primary source of the somatodendritic A-type K+ current in CA1 pyramidal neurons of the hippocampus, play important roles in regulating dendritic excitability and plasticity. To better study the trafficking and subcellular distribution of Kv4.2, we created and characterized a novel Kv4.2 construct encoding a bungarotoxin binding site in the extracellular S3-S4 linker region of the α-subunit. When expressed, this construct can be visualized in living cells after staining with rhodamine-conjugated bungarotoxin. We validated the utility of this construct by visualizing the spontaneous internalization and insertion of Kv4.2 in HEK 293T cells. We further report that Kv4.2 colocalized with several endosome markers in HEK 293T cells. In addition, Kv4.2 internalization is significantly impaired by mitogen-activated protein kinase (MAPK) inhibitors in transfected primary hippocampal neurons. Therefore, this newly developed BBS-Kv4.2 construct provides a novel and powerful tool for studying surface Kv4.2 channel localization and trafficking.
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Affiliation(s)
- G Travis Tabor
- Section on Molecular Neurophysiology & Biophysics, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, United States of America
| | - Jung M Park
- Section on Molecular Neurophysiology & Biophysics, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, United States of America
| | - Jonathan G Murphy
- Section on Molecular Neurophysiology & Biophysics, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, United States of America; National Institute of General Medical Sciences, NIH, Bethesda, MD 20892, United States of America
| | - Jia-Hua Hu
- Section on Molecular Neurophysiology & Biophysics, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, United States of America.
| | - Dax A Hoffman
- Section on Molecular Neurophysiology & Biophysics, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, United States of America.
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5
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Therapeutic Monoclonal Antibodies to Complex Membrane Protein Targets: Antigen Generation and Antibody Discovery Strategies. BioDrugs 2019; 32:339-355. [PMID: 29934752 DOI: 10.1007/s40259-018-0289-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cell surface membrane proteins comprise a wide array of structurally and functionally diverse proteins involved in a variety of important physiological and homeostatic processes. Complex integral membrane proteins, which are embedded in the lipid bilayer by multiple transmembrane-spanning helices, are represented by families of proteins that are important target classes for drug discovery. Such protein families include G-protein-coupled receptors, ion channels and transporters. Although these targets have typically been the domain of small-molecule drugs, the exquisite specificity of monoclonal antibodies offers a significant opportunity to selectively modulate these target proteins. Nevertheless, the isolation of antibodies with desired pharmacological functions has proved difficult because of technical challenges in preparing membrane protein antigens for antibody drug discovery. In this review, we describe recent progress in defining strategies for the generation of membrane protein antigens. We also describe antibody-isolation strategies that identify antibodies that bind the membrane protein and modulate protein function.
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6
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HiBiT-qIP, HiBiT-based quantitative immunoprecipitation, facilitates the determination of antibody affinity under immunoprecipitation conditions. Sci Rep 2019; 9:6895. [PMID: 31053795 PMCID: PMC6499798 DOI: 10.1038/s41598-019-43319-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 01/31/2019] [Indexed: 12/23/2022] Open
Abstract
The affinity of an antibody for its antigen serves as a critical parameter for antibody evaluation. The evaluation of antibody-antigen affinity is essential for a successful antibody-based assay, particularly immunoprecipitation (IP), due to its strict dependency on antibody performance. However, the determination of antibody affinity or its quantitative determinant, the dissociation constant (Kd), under IP conditions is difficult. In the current study, we used a NanoLuc-based HiBiT system to establish a HiBiT-based quantitative immunoprecipitation (HiBiT-qIP) assay for determining the Kd of antigen-antibody interactions in solution. The HiBiT-qIP method measures the amount of immunoprecipitated proteins tagged with HiBiT in a simple yet quantitative manner. We used this method to measure the Kd values of epitope tag-antibody interactions. To accomplish this, FLAG, HA, V5, PA and Ty1 epitope tags in their monomeric, dimeric or trimeric form were fused with glutathione S-transferase (GST) and the HiBiT peptide, and these tagged GST proteins were mixed with cognate monoclonal antibodies in IP buffer for the assessment of the apparent Kd values. This HiBiT-qIP assay showed a considerable variation in the Kd values among the examined antibody clones. Additionally, the use of epitope tags in multimeric form revealed a copy number-dependent increase in the apparent affinity.
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7
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Stawarski M, Justs KA, Hernandez RX, Macleod GT. The application of 'kisser' probes for resolving the distribution and microenvironment of membrane proteins in situ. J Neurogenet 2018; 32:236-245. [PMID: 30175639 DOI: 10.1080/01677063.2018.1503260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Membrane proteins play a lead role in the formation and function of synapses, but, despite revolutions in immunology and molecular genetics, limitations persist in our ability to investigate membrane proteins in the context of an intact synapse. Here, we introduce a simple but novel approach to resolving the distribution of endogenous membrane proteins in either live or fixed tissues. The technique involves transgenic expression of a protein with an extracellular tag, a generic transmembrane domain, and an intracellular terminus that mimics the intracellular anchoring motifs of the endogenous protein of interest. We provide three examples where these kisser probes can be used to answer questions regarding the synaptic distribution of endogenous proteins and their microenvironment that would be difficult to resolve by other contemporary means: (i) the live distribution of untagged proteins at the neuromuscular junction (Cacophony and Shaker), (ii) the relative distribution of an untagged protein (PMCA) in pre- versus post-synaptic membranes separated by only 20 nm across the cleft of a fixed synapse, and (iii) the live targeting of functional probes (chemical and protein fluorescent pH reporters) to membrane protein-defined subcellular domains.
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Affiliation(s)
- Michal Stawarski
- a Department of Biomedicine , University of Basel , Basel , Switzerland
| | - Karlis Anthony Justs
- b Wilkes Honors College , Florida Atlantic University, John D MacArthur Campus , Jupiter , FL, USA
| | - Roberto Xander Hernandez
- b Wilkes Honors College , Florida Atlantic University, John D MacArthur Campus , Jupiter , FL, USA
| | - Gregory Talisker Macleod
- b Wilkes Honors College , Florida Atlantic University, John D MacArthur Campus , Jupiter , FL, USA
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8
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Prechtel H, Hartmann S, Minge D, Bähring R. Somatodendritic surface expression of epitope-tagged and KChIP binding-deficient Kv4.2 channels in hippocampal neurons. PLoS One 2018; 13:e0191911. [PMID: 29385176 PMCID: PMC5792006 DOI: 10.1371/journal.pone.0191911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/12/2018] [Indexed: 11/19/2022] Open
Abstract
Kv4.2 channels mediate a subthreshold-activating somatodendritic A-type current (ISA) in hippocampal neurons. We examined the role of accessory Kv channel interacting protein (KChIP) binding in somatodendritic surface expression and activity-dependent decrease in the availability of Kv4.2 channels. For this purpose we transfected cultured hippocampal neurons with cDNA coding for Kv4.2 wild-type (wt) or KChIP binding-deficient Kv4.2 mutants. All channels were equipped with an externally accessible hemagglutinin (HA)-tag and an EGFP-tag, which was attached to the C-terminal end. Combined analyses of EGFP self-fluorescence, surface HA immunostaining and patch-clamp recordings demonstrated similar dendritic trafficking and functional surface expression for Kv4.2[wt]HA,EGFP and the KChIP binding-deficient Kv4.2[A14K]HA,EGFP. Coexpression of exogenous KChIP2 augmented the surface expression of Kv4.2[wt]HA,EGFP but not Kv4.2[A14K]HA,EGFP. Notably, activity-dependent decrease in availability was more pronounced in Kv4.2[wt]HA,EGFP + KChIP2 coexpressing than in Kv4.2[A14K]HA,EGFP + KChIP2 coexpressing neurons. Our results do not support the notion that accessory KChIP binding is a prerequisite for dendritic trafficking and functional surface expression of Kv4.2 channels, however, accessory KChIP binding may play a potential role in Kv4.2 modulation during intrinsic plasticity processes.
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Affiliation(s)
- Helena Prechtel
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Sven Hartmann
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Daniel Minge
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Robert Bähring
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
- * E-mail:
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9
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Friedel P, Ludwig A, Pellegrino C, Agez M, Jawhari A, Rivera C, Medina I. A Novel View on the Role of Intracellular Tails in Surface Delivery of the Potassium-Chloride Cotransporter KCC2. eNeuro 2017; 4:ENEURO.0055-17.2017. [PMID: 28785725 PMCID: PMC5520751 DOI: 10.1523/eneuro.0055-17.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 06/20/2017] [Accepted: 07/04/2017] [Indexed: 01/06/2023] Open
Abstract
A plethora of neurological disorders are associated with alterations in the expression and localization of potassium-chloride cotransporter type 2 (KCC2), making KCC2 a critical player in neuronal function and an attractive target for therapeutic treatment. The activity of KCC2 is determined primarily by the rates of its surface insertion and internalization. Currently the domains of KCC2 dictating its trafficking and endocytosis are unknown. Here, using live-cell immunolabeling and biotinylation of KCC2 proteins expressed in murine neuroblastoma N2a cells, human embryonic kidney 293 cells, or primary cultures of rat hippocampal neurons, we identified a novel role for the intracellular N and C termini in differentially regulating KCC2 surface expression. We report that the N terminus is required for KCC2 insertion into the plasma membrane, whereas the C terminus is critical for the membrane stability of KCC2. Our results provide novel insights into the structure-function role of specific KCC2 domains and open perspectives in exploring structural organization of this protein.
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Affiliation(s)
- Perrine Friedel
- INMED, Aix-Marseille University, INSERM, Marseille 13273, France
| | - Anastasia Ludwig
- Neuroscience Center, University of Helsinki, Helsinki 00100, Finland
| | | | | | | | - Claudio Rivera
- INMED, Aix-Marseille University, INSERM, Marseille 13273, France
- Neuroscience Center, University of Helsinki, Helsinki 00100, Finland
| | - Igor Medina
- INMED, Aix-Marseille University, INSERM, Marseille 13273, France
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10
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Discovery of functional monoclonal antibodies targeting G-protein-coupled receptors and ion channels. Biochem Soc Trans 2017; 44:831-7. [PMID: 27284048 DOI: 10.1042/bst20160028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 11/17/2022]
Abstract
The development of recombinant antibody therapeutics is a significant area of growth in the pharmaceutical industry with almost 50 approved monoclonal antibodies on the market in the US and Europe. Despite this growth, however, certain classes of important molecular targets have remained intractable to therapeutic antibodies due to complexity of the target molecules. These complex target molecules include G-protein-coupled receptors and ion channels which represent a large potential target class for therapeutic intervention with monoclonal antibodies. Although these targets have typically been addressed by small molecule approaches, the exquisite specificity of antibodies provides a significant opportunity to provide selective modulation of these target proteins. Given this opportunity, substantial effort has been applied to address the technical challenges of targeting these complex membrane proteins with monoclonal antibodies. In this review recent progress made in the strategies for discovery of functional monoclonal antibodies for these challenging membrane protein targets is addressed.
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11
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Kühn FJP, Kühn C, Winking M, Hoffmann DC, Lückhoff A. ADP-Ribose Activates the TRPM2 Channel from the Sea Anemone Nematostella vectensis Independently of the NUDT9H Domain. PLoS One 2016; 11:e0158060. [PMID: 27333281 PMCID: PMC4917252 DOI: 10.1371/journal.pone.0158060] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 06/09/2016] [Indexed: 01/10/2023] Open
Abstract
The human redox-sensitive Transient receptor potential melastatin type 2 (hTRPM2) channel contains the C-terminal Nudix hydrolase domain NUDT9H which most likely binds ADP-ribose. During oxidative stress, the intracellular release of ADP-ribose triggers the activation of hTRPM2. The TRPM2 orthologue from Nematostella vectensis (nv) is also stimulated by ADP-ribose but not by the oxidant hydrogen peroxide. For further clarification of the structure-function relationships of these two distantly related channel orthologues, we performed whole-cell as well as single channel patch-clamp recordings, Ca2+-imaging and Western blot analysis after heterologous expression of wild-type and mutated channels in HEK-293 cells. We demonstrate that the removal of the entire NUDT9H domain does not disturb the response of nvTRPM2 to ADP-ribose. The deletion, however, created channels that were activated by hydrogen peroxide, as did mutations within the NUDT9H domain of nvTRPM2 that presumably suppress its enzymatic function. The same findings were obtained with the nvTRPM2 channel when the NUDT9H domain was replaced by the corresponding sequences of the original hNUDT9 enzyme. Whenever the enzyme domain was mutated to presumably inactive variants, channel activation by hydrogen peroxide could be achieved. Moreover, we found strong evidences for ADPRase activity of the isolated NUDT9H domain of nvTRPM2 in co-expression experiments with the C-terminally truncated nvTRPM2 channel. Thus, there is a clear correlation between the loss of enzymatic activity and the capability of nvTRPM2 to respond to oxidative stress. In striking contrast, the channel function of the hTRPM2 orthologue, in particular its sensitivity to ADP-ribose, was abrogated by already small changes of the NUDT9H domain. These findings establish nvTRPM2 as a channel gated by ADP-ribose through a novel mechanism. We conclude that the endogenous NUDT9H domain does not directly affect ADP-ribose-dependent gating of the nvTRPM2 channel; instead it exerts an independent catalytic function which possibly controls the intracellular availability of ADP-ribose.
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Affiliation(s)
- Frank J. P. Kühn
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany
- * E-mail:
| | - Cornelia Kühn
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany
| | - Mathis Winking
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany
| | - Daniel C. Hoffmann
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany
| | - Andreas Lückhoff
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany
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12
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Development of therapeutic antibodies to G protein-coupled receptors and ion channels: Opportunities, challenges and their therapeutic potential in respiratory diseases. Pharmacol Ther 2016; 169:113-123. [PMID: 27153991 DOI: 10.1016/j.pharmthera.2016.04.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The development of recombinant antibody therapeutics continues to be a significant area of growth in the pharmaceutical industry with almost 50 approved monoclonal antibodies on the market in the US and Europe. Therapeutic drug targets such as soluble cytokines, growth factors and single transmembrane spanning receptors have been successfully targeted by recombinant monoclonal antibodies and the development of new product candidates continues. Despite this growth, however, certain classes of important disease targets have remained intractable to therapeutic antibodies due to the complexity of the target molecules. These complex target molecules include G protein-coupled receptors and ion channels which represent a large target class for therapeutic intervention with monoclonal antibodies. Although these targets have typically been addressed by small molecule approaches, the exquisite specificity of antibodies provides a significant opportunity to provide selective modulation of these important regulators of cell function. Given this opportunity, a significant effort has been applied to address the challenges of targeting these complex molecules and a number of targets are linked to the pathophysiology of respiratory diseases. In this review, we provide a summary of the importance of GPCRs and ion channels involved in respiratory disease and discuss advantages offered by antibodies as therapeutics at these targets. We highlight some recent GPCRs and ion channels linked to respiratory disease mechanisms and describe in detail recent progress made in the strategies for discovery of functional antibodies against challenging membrane protein targets such as GPCRs and ion channels.
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Wilkinson TCI, Gardener MJ, Williams WA. Discovery of Functional Antibodies Targeting Ion Channels. ACTA ACUST UNITED AC 2014; 20:454-67. [DOI: 10.1177/1087057114560698] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ion channels play critical roles in physiology and disease by modulation of cellular functions such as electrical excitability, secretion, cell migration, and gene transcription. Ion channels represent an important target class for drug discovery that has been largely addressed, to date, using small-molecule approaches. A significant opportunity exists to target these channels with antibodies and alternative formats of biologics. Antibodies display high specificity and affinity for their target antigen, and they have the potential to target ion channels very selectively. Nevertheless, isolating antibodies to this target class is challenging due to the difficulties in expression and purification of ion channels in a format suitable for antibody drug discovery in addition to the complexity of screening for function. In this article, we will review the current state of ion channel biologics discovery and the progress that has been made. We will also highlight the challenges in isolating functional antibodies to these targets and how these challenges may be addressed. Finally, we also illustrate successful approaches to isolating functional monoclonal antibodies targeting ion channels by way of a number of case studies drawn from recent publications.
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Affiliation(s)
| | | | - Wendy A. Williams
- Antibody Discovery and Protein Engineering, MedImmune, Cambridge, UK
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14
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Abstract
The paralytic agent (+)-saxitoxin (STX), most commonly associated with oceanic red tides and shellfish poisoning, is a potent inhibitor of electrical conduction in cells. Its nefarious effects result from inhibition of voltage-gated sodium channels (Na(V)s), the obligatory proteins responsible for the initiation and propagation of action potentials. In the annals of ion channel research, the identification and characterization of Na(V)s trace to the availability of STX and an allied guanidinium derivative, tetrodotoxin. The mystique of STX is expressed in both its function and form, as this uniquely compact dication boasts more heteroatoms than carbon centers. This Review highlights both the chemistry and chemical biology of this fascinating natural product, and offers a perspective as to how molecular design and synthesis may be used to explore Na(V) structure and function.
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Affiliation(s)
- Arun P Thottumkara
- Department of Chemistry, Stanford University, Stanford, CA 94305-5080 (USA)
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16
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Brown M, Stafford LJ, Onisk D, Joaquim T, Tobb A, Goldman L, Fancy D, Stave J, Chambers R. Snorkel: an epitope tagging system for measuring the surface expression of membrane proteins. PLoS One 2013; 8:e73255. [PMID: 24023844 PMCID: PMC3759426 DOI: 10.1371/journal.pone.0073255] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 07/17/2013] [Indexed: 02/01/2023] Open
Abstract
Tags are widely used to monitor a protein’s expression level, interactions, protein trafficking, and localization. Membrane proteins are often tagged in their extracellular domains to allow discrimination between protein in the plasma membrane from that in internal pools. Multipass membrane proteins offer special challenges for inserting a tag since the extracellular regions are often composed of small loops and thus inserting an epitope tag risks perturbing the structure, function, or location of the membrane protein. We have developed a novel tagging system called snorkel where a transmembrane domain followed by a tag is appended to the cytoplasmic C-terminus of the membrane protein. In this way the tag is displayed extracellularly, but structurally separate from the membrane protein. We have tested the snorkel tag system on a diverse panel of membrane proteins including GPCRs and ion channels and demonstrated that it reliably allows for monitoring of the surface expression.
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Affiliation(s)
| | | | - Dale Onisk
- SDIX, Newark, Delaware, United States of America
| | - Tony Joaquim
- SDIX, Newark, Delaware, United States of America
| | - Alhagie Tobb
- SDIX, Newark, Delaware, United States of America
| | | | - David Fancy
- SDIX, Newark, Delaware, United States of America
| | - James Stave
- SDIX, Newark, Delaware, United States of America
| | - Ross Chambers
- SDIX, Newark, Delaware, United States of America
- * E-mail:
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17
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Ondrus AE, Lee HLD, Iwanaga S, Parsons WH, Andresen BM, Moerner W, Bois JD. Fluorescent saxitoxins for live cell imaging of single voltage-gated sodium ion channels beyond the optical diffraction limit. CHEMISTRY & BIOLOGY 2012; 19:902-12. [PMID: 22840778 PMCID: PMC3731772 DOI: 10.1016/j.chembiol.2012.05.021] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 05/24/2012] [Accepted: 05/25/2012] [Indexed: 12/19/2022]
Abstract
A desire to better understand the role of voltage-gated sodium channels (Na(V)s) in signal conduction and their dysregulation in specific disease states motivates the development of high precision tools for their study. Nature has evolved a collection of small molecule agents, including the shellfish poison (+)-saxitoxin, that bind to the extracellular pore of select Na(V) isoforms. As described in this report, de novo chemical synthesis has enabled the preparation of fluorescently labeled derivatives of (+)-saxitoxin, STX-Cy5, and STX-DCDHF, which display reversible binding to Na(V)s in live cells. Electrophysiology and confocal fluorescence microscopy studies confirm that these STX-based dyes function as potent and selective Na(V) labels. The utility of these probes is underscored in single-molecule and super-resolution imaging experiments, which reveal Na(V) distributions well beyond the optical diffraction limit in subcellular features such as neuritic spines and filopodia.
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Affiliation(s)
- Alison E. Ondrus
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
| | - Hsiao-lu D. Lee
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
| | - Shigeki Iwanaga
- SYSMEX Corporation, Central Research Laboratories, 4-4-4, Takatsukadai, Nishi-ku, Kobe 651-2271, Japan
| | - William H. Parsons
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
| | - Brian M. Andresen
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
| | - W.E. Moerner
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
| | - J. Du Bois
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305-5080, USA
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Formation of N-type (Cav2.2) voltage-gated calcium channel membrane microdomains: Lipid raft association and clustering. Cell Calcium 2010; 48:183-94. [DOI: 10.1016/j.ceca.2010.08.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 08/12/2010] [Indexed: 12/29/2022]
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Park EJ, Kim BJ, Kim SH, Kim SY, Sung TS, Chae HG, Kim SJ, Kim J, Park HH, So I, Jeon JH. Altered biochemical properties of transient receptor potential vanilloid 6 calcium channel by peptide tags. Biol Pharm Bull 2010; 32:1790-4. [PMID: 19801845 DOI: 10.1248/bpb.32.1790] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ion channels are commonly expressed in recombinant forms with peptide tags, which facilitates their molecular and electrophysiological studies. However, peptide tags may alter ion channel properties. Here we describe the differential effect of peptide tags on the biochemical properties of transient receptor potential vanilloid 6 (TRPV6) channels. Yellow fluorescent protein (YFP)-tagged wild-type TRPV6 (YFP-TRPV6(WT)) showed much lower levels of aggregate-like bands in Western blots than those of Myc-TRPV6(WT). By contrast, the glycosylation level was higher with Myc-TRPV6(WT) than that with YFP-TRPV6(WT). We additionally demonstrate that peptide tags affect the protein integrity of TRPV6 channels. Myc-TRPV6(WT) was expressed as an intact channel, whereas the pore mutants Myc-TRPV6(D542A) and Myc-TRPV6(D542K) were observed to be partially fragmented. By contrast, all YFP-tagged channels were intact, although the YFP-tagged pore mutants were less glycosylated than YFP-TRPV6(WT). However, regardless of the peptide tag used, TRPV6(D542A) and TRPV6(D542K) electrophysiologically inhibited TRPV6(WT) which indicates that all pore mutants are equivalent electrophysiologically, not biochemically. Thus, our findings suggest that peptide tags can produce unintended biochemical changes of ion channels which highlight the necessity of careful biochemical evaluation to clarify the roles of ion channels.
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Affiliation(s)
- Eun-Jung Park
- Department of Physiology, Seoul National University College of Medicine, Korea
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20
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Abstract
Since the early 1980s, when the first transgenic mice were generated, thousands of genetically modified mouse lines have been created. Early on, Jaenisch established proof of principle, showing that viral integration into the mouse genome and germline transmission of those exogenous sequences were possible (Proc Natl Acad Sci USA 71:1250-1254, 1974). Gordon et al. (Proc Natl Acad Sci USA 77:7380-7384, 1980) and Brinster et al. (Cell 27:223-231, 1981) subsequently used cloned genes to create "transgenic constructs" in which the exogenous DNA was randomly inserted into different sites in the mouse genome, stably maintained, and transmitted through the germline to the progeny. The utility of the process quickly became apparent when a transgene carrying the metallothionein-1 (Mt-1) promoter linked to thymidine kinase was able to drive expression in the mouse liver when promoter activity was induced by administration of metals. In an attempt to find stronger and more reliable promoters, viral promoter elements from SV40 or cytomegalovirus were incorporated. However, while these promoters were able to drive high levels of expression, for many applications they proved to be too blunt an instrument as they drove ubiquitous expression in many, if not all cell types, making it very hard to discern organ-specific or cell-type-specific effects due to transgene expression. Thus the need to find cell-type-specific promoters that could reproducibly drive high levels of transgene expression in a particular cell type, e.g., cardiomyocyte, became apparent. One such example is the alpha myosin heavy-chain (MHC) promoter, which has been used extensively to drive transgene expression in a cardiomyocyte-specific manner in the mouse. This chapter, while not written as a typical methods section, will describe the necessary components of the alpha myosin promoter. In addition, common problems associated with transgenic mouse lines will be addressed.
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Affiliation(s)
- James Gulick
- Cincinnati Children's Hospital, University of Cincinnati, Cincinnati, OH, USA
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