1
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Codding SJ, Trudeau MC. Photoinhibition of the hERG potassium channel PAS domain by ultraviolet light speeds channel closing. Biophys J 2024; 123:2392-2405. [PMID: 38796698 DOI: 10.1016/j.bpj.2024.05.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 04/30/2024] [Accepted: 05/22/2024] [Indexed: 05/28/2024] Open
Abstract
hERG potassium channels are critical for cardiac excitability. hERG channels have a Per-Arnt-Sim (PAS) domain at their N-terminus, and here, we examined the mechanism for PAS domain regulation of channel opening and closing (gating). We used TAG codon suppression to incorporate the noncanonical amino acid 4-benzoyl-L-phenylalanine (BZF), which is capable of forming covalent cross-links after photoactivation by ultraviolet (UV) light, at three locations (G47, F48, and E50) in the PAS domain. We found that hERG-G47BZF channels had faster closing (deactivation) when irradiated in the open state (at 0 mV) but showed no measurable changes when irradiated in the closed state (at -100 mV). hERG-F48BZF channels had slower activation, faster deactivation, and a marked rightward shift in the voltage dependence of activation when irradiated in the open (at 0 mV) or closed (at -100 mV) state. hERG-E50BZF channels had no measurable changes when irradiated in the open state (at 0 mV) but had slower activation, faster deactivation, and a rightward shift in the voltage dependence of activation when irradiated in the closed state (at -100mV), indicating that hERG-E50BZF had a state-dependent difference in UV photoactivation, which we interpret to mean that PAS underwent molecular motions between the open and closed states. Moreover, we propose that UV-dependent biophysical changes in hERG-G47BZF, F48BZF, and E50BZF were the direct result of photochemical cross-linking that reduced dynamic motions in the PAS domain and broadly stabilized the closed state relative to the open state of the channel.
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Affiliation(s)
- Sara J Codding
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Matthew C Trudeau
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.
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2
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Söllner J, Derler I. Genetic code expansion, an emerging tool in the Ca 2+ ion channel field. J Physiol 2024; 602:3297-3313. [PMID: 38695316 DOI: 10.1113/jp285840] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 04/15/2024] [Indexed: 07/17/2024] Open
Abstract
Various methods for characterizing binding forces as well as for monitoring and remote control of ion channels are still emerging. A recent innovation is the direct incorporation of unnatural amino acids (UAAs) with corresponding biophysical or biochemical properties, which are integrated using genetic code expansion technology. Minimal changes to natural amino acids, which are achieved by chemical synthesis of corresponding UAAs, are valuable tools to provide insight into the contributions of physicochemical properties of side chains in binding events. To gain unique control over the conformational changes or function of ion channels, a series of light-sensitive, chemically reactive and posttranslationally modified UAAs have been developed and utilized. Here, we present the existing UAA tools, their mode of action, their potential and limitations as well as their previous applications to Ca2+-permeable ion channels.
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Affiliation(s)
- Julia Söllner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
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3
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Codding SJ, Trudeau MC. Photo-crosslinking hERG channels causes a U.V.-driven, state-dependent disruption of kinetics and voltage dependence of activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.09.574834. [PMID: 38260338 PMCID: PMC10802430 DOI: 10.1101/2024.01.09.574834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Human ether-à-go-go related gene (hERG) voltage-activated potassium channels are critical for cardiac excitability. Characteristic slow closing (deactivation) in hERG is regulated by direct interaction between the N-terminal Per-Arnt-Sim (PAS) domain and the C-terminal cyclic nucleotide binding homology domain (CNBHD). We aim to understand how the PAS domain that is distal to the pore rearranges during gating to allosterically regulate the channel pore (and ion flux). To achieve this, we utilized the non-canonical amino acid 4-Benzoyl-L-phenylalanine (BZF) which is a photo-activatable cross-linkable probe, that when irradiated with ultraviolet (U.V.) light forms a double radical capable of forming covalent cross-links with C-H bond-containing groups, enabling selective and potent U.V.-driven photoinactivation of ion channel dynamics. Here we incorporate BZF directly into the hERG potassium channel PAS domain at three locations (G47, F48, and E50) using TAG codon suppression technology. hERG channels with BZF incorporated into the PAS domain (hERG-BZF) showed a significant change in the biophysical properties of the channel. hERG-G47BZF activated slowly when irradiated in the closed state (-100mV) but deactivated quickly when irradiated in both the open (0mV) and closed state. hERG-F48BZF channels showed a state independent and U.V. dose-dependent change in channel activation (slowing down) and channel deactivation (speeding up), as well as a marked change (right-shift) in the voltage-dependence of conductance. When irradiated at -100 mV hERG-E50BZF showed a state dependent and U.V. dose-dependent change in a channel activation (slowing down) and deactivation (speeding up) of channel deactivation, as well as a marked change (right-shift) in the voltage-dependence of conductance that occurred only when the channel was irradiated in the closed state (-100mV). This approach demonstrated that direct photo-crosslinking of the PAS domain in hERG channels causes a measurable change in biophysical parameters and more broadly stabilized the closed state of the channel. We propose that altered channel gating is as a direct result of reduced dynamic motions in the PAS domain of hERG due to photo-chemical crosslinking.
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Affiliation(s)
- Sara J Codding
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Matthew C Trudeau
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
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4
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Majumdar C, Walker JA, Francis MB, Schepartz A, Cate JHD. Aminobenzoic Acid Derivatives Obstruct Induced Fit in the Catalytic Center of the Ribosome. ACS CENTRAL SCIENCE 2023; 9:1160-1169. [PMID: 37396857 PMCID: PMC10311655 DOI: 10.1021/acscentsci.3c00153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Indexed: 07/04/2023]
Abstract
The Escherichia coli (E. coli) ribosome can incorporate a variety of non-l-α-amino acid monomers into polypeptide chains in vitro but with poor efficiency. Although these monomers span a diverse set of compounds, there exists no high-resolution structural information regarding their positioning within the catalytic center of the ribosome, the peptidyl transferase center (PTC). Thus, details regarding the mechanism of amide bond formation and the structural basis for differences and defects in incorporation efficiency remain unknown. Within a set of three aminobenzoic acid derivatives-3-aminopyridine-4-carboxylic acid (Apy), ortho-aminobenzoic acid (oABZ), and meta-aminobenzoic acid (mABZ)-the ribosome incorporates Apy into polypeptide chains with the highest efficiency, followed by oABZ and then mABZ, a trend that does not track with the nucleophilicity of the reactive amines. Here, we report high-resolution cryo-EM structures of the ribosome with each of these three aminobenzoic acid derivatives charged on tRNA bound in the aminoacyl-tRNA site (A-site). The structures reveal how the aromatic ring of each monomer sterically blocks the positioning of nucleotide U2506, thereby preventing rearrangement of nucleotide U2585 and the resulting induced fit in the PTC required for efficient amide bond formation. They also reveal disruptions to the bound water network that is believed to facilitate formation and breakdown of the tetrahedral intermediate. Together, the cryo-EM structures reported here provide a mechanistic rationale for differences in reactivity of aminobenzoic acid derivatives relative to l-α-amino acids and each other and identify stereochemical constraints on the size and geometry of non-monomers that can be accepted efficiently by wild-type ribosomes.
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Affiliation(s)
- Chandrima Majumdar
- Department
of Molecular and Cell Biology, University
of California, Berkeley, California 94720, United States
| | - Joshua A. Walker
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Matthew B. Francis
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Molecular
Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alanna Schepartz
- Department
of Molecular and Cell Biology, University
of California, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Molecular
Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Chan
Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Jamie H. D. Cate
- Department
of Molecular and Cell Biology, University
of California, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Molecular
Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Innovative
Genomics Institute, University of California, Berkeley, California 94720, United States
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5
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Mala P, Saraogi I. Enhanced Codon-Anticodon Interaction at In-Frame UAG Stop Codon Improves the Efficiency of Non-Natural Amino Acid Mutagenesis. ACS Chem Biol 2022; 17:1051-1060. [PMID: 35532803 DOI: 10.1021/acschembio.1c00782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The introduction of non-natural amino acids into proteins through the stop codon readthrough methodology has been used to design proteins for diverse applications. However, this method suffers from low yields of the modified protein, as the suppressor tRNA that recognizes the stop codon is unable to compete effectively with release factor 1 (RF1), which terminates translation. We reasoned that a suppressor tRNA with improved interaction with the UAG stop codon on the mRNA will be able to compete more effectively with RF1. To test this idea, we inserted two 2,6-diaminopurine (D) units in the tRNA anticodon stem loop, including one at the third position of the tRNA anticodon. The modified suppressor tRNA could potentially form additional H-bonds between the N2-exocyclic amine of D and the C2 carbonyl group of uracil, thereby enhancing mRNA-tRNA interaction and/or altering tRNA conformation. The stronger interaction at the codon-anticodon interface resulted in improved UAG decoding efficiency and a higher yield of the modified protein containing a non-natural amino acid at multiple sites. Our findings are consistent with the importance of hydrogen bonding and tRNA conformation at the tRNA-mRNA duplex interface during in-frame UAG suppression, which improves protein translation at multiple UAG stop sites. This work provides valuable inputs toward improved non-natural amino acid mutagenesis for creating designer proteins.
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Affiliation(s)
- Purnima Mala
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
| | - Ishu Saraogi
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
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6
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Perez JG, Carlson ED, Weisser O, Kofman C, Seki K, Des Soye BJ, Karim AS, Jewett MC. Improving genomically recoded Escherichia coli to produce proteins containing non-canonical amino acids. Biotechnol J 2022; 17:e2100330. [PMID: 34894206 DOI: 10.1002/biot.202100330] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 12/08/2021] [Accepted: 12/09/2021] [Indexed: 12/12/2022]
Abstract
A genomically recoded Escherichia coli strain that lacks all amber codons and release factor 1 (C321.∆A) enables efficient genetic encoding of chemically diverse non-canonical amino acids (ncAAs) into proteins. While C321.∆A has opened new opportunities in chemical and synthetic biology, this strain has not been optimized for protein production, limiting its utility in widespread industrial and academic applications. To address this limitation, the construction of a series of genomically recoded organisms that are optimized for cellular protein production is described. It is demonstrated that the functional deactivation of nucleases (e.g., rne, endA) and proteases (e.g., lon) increases production of wild-type superfolder green fluorescent protein (sfGFP) and sfGFP containing two ncAAs up to ≈5-fold. Additionally, a genomic IPTG-inducible T7 RNA polymerase (T7RNAP) cassette into these strains is introduced. Using an optimized platform, the ability to introduce two identical N6 -(propargyloxycarbonyl)-L -Lysine residues site specifically into sfGFP with a 17-fold improvement in production relative to the parent strain is demonstrated. The authors envision that their library of organisms will provide the community with multiple options for increased expression of proteins with new and diverse chemistries.
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Affiliation(s)
- Jessica G Perez
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Erik D Carlson
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Oliver Weisser
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Camila Kofman
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Kosuke Seki
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Benjamin J Des Soye
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Ashty S Karim
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Michael C Jewett
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois, USA
- Simpson Querrey Institute, Northwestern University, Chicago, Illinois, USA
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7
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Cairns-Gibson DF, Cockroft SL. Functionalised nanopores: chemical and biological modifications. Chem Sci 2022; 13:1869-1882. [PMID: 35308845 PMCID: PMC8848921 DOI: 10.1039/d1sc05766a] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/22/2021] [Indexed: 12/11/2022] Open
Abstract
Nanopore technology has established itself as a powerful tool for single-molecule studies. By analysing changes in the ion current flowing through a single transmembrane channel, a wealth of molecular information can be elucidated. Early studies utilised nanopore technology for sensing applications, and subsequent developments have diversified its remit. Nanopores can be synthetic, solid-state, or biological in origin, but recent work has seen these boundaries blurred as hybrid functionalised pores emerge. The modification of existing pores and the construction of novel synthetic pores has been an enticing goal for creating systems with tailored properties and functionality. Here, we explore chemically functionalised biological pores and the bio-inspired functionalisation of solid-state pores, highlighting how the convergence of these domains provides enhanced functionality. The convergence of chemistry, biology, and solid-state approaches enables the construction hybrid nanopores with enhanced single-molecule applications.![]()
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Affiliation(s)
- Dominic F. Cairns-Gibson
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Scott L. Cockroft
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK
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8
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Machado JH, Ting R, Lin JY, Rodriguez EA. A self-labeling protein based on the small ultra-red fluorescent protein, smURFP. RSC Chem Biol 2021; 2:1221-1226. [PMID: 34458834 PMCID: PMC8341759 DOI: 10.1039/d1cb00127b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 06/24/2021] [Indexed: 12/25/2022] Open
Abstract
Self-labeling proteins have revolutionized super-resolution and sensor imaging. Tags recognize a bioorthogonal substrate for covalent attachment. We show the small Ultra-Red Fluorescent Protein (smURFP) is a self-labeling protein. The substrate is fluorogenic, fluoresces when attached, and quenches fluorescent cargo. The smURFP-tag has novel properties for tool development.
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Affiliation(s)
- John-Hanson Machado
- Department of Chemistry, The George Washington University Washington DC 20052 USA
| | - Richard Ting
- Department of Radiology, Molecular Imaging Innovations Institute (MI3), Weill Cornell Medicine New York NY 10065 USA
- Antelope Surgical, Biolabs@NYULangone New York NY 10014 USA
| | - John Y Lin
- Tasmanian School of Medicine, University of Tasmania Hobart Tasmania 7000 Australia
| | - Erik A Rodriguez
- Department of Chemistry, The George Washington University Washington DC 20052 USA
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9
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Abstract
Genetic code expansion is one of the most powerful technologies in protein engineering. In addition to the 20 canonical amino acids, the expanded genetic code is supplemented by unnatural amino acids, which have artificial side chains that can be introduced into target proteins in vitro and in vivo. A wide range of chemical groups have been incorporated co-translationally into proteins in single cells and multicellular organisms by using genetic code expansion. Incorporated unnatural amino acids have been used for novel structure-function relationship studies, bioorthogonal labelling of proteins in cellulo for microscopy and in vivo for tissue-specific proteomics, the introduction of post-translational modifications and optical control of protein function, to name a few examples. In this Minireview, the development of genetic code expansion technology is briefly introduced, then its applications in neurobiology are discussed, with a focus on studies using mammalian cells and mice as model organisms.
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Affiliation(s)
- Ivana Nikić‐Spiegel
- Werner Reichardt Centre for Integrative NeuroscienceUniversity of TübingenOtfried-Müller-Strasse 2572076TübingenGermany
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10
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Müller D, Trucks S, Schwalbe H, Hengesbach M. Genetic Code Expansion Facilitates Position-Selective Modification of Nucleic Acids and Proteins. Chempluschem 2020; 85:1233-1243. [PMID: 32515171 DOI: 10.1002/cplu.202000150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/11/2020] [Indexed: 12/12/2022]
Abstract
Transcription and translation obey to the genetic code of four nucleobases and 21 amino acids evolved over billions of years. Both these processes have been engineered to facilitate the use of non-natural building blocks in both nucleic acids and proteins, enabling researchers with a decent toolbox for structural and functional analyses. Here, we review the most common approaches for how labeling of both nucleic acids as well as proteins in a site-selective fashion with either modifiable building blocks or spectroscopic probes can be facilitated by genetic code expansion. We emphasize methodological approaches and how these can be adapted for specific modifications, both during as well as after biomolecule synthesis. These modifications can facilitate, for example, a number of different spectroscopic analysis techniques and can under specific circumstances even be used in combination.
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Affiliation(s)
- Diana Müller
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Sven Trucks
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Martin Hengesbach
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
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11
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Paoletti P, Ellis-Davies GCR, Mourot A. Optical control of neuronal ion channels and receptors. Nat Rev Neurosci 2020; 20:514-532. [PMID: 31289380 DOI: 10.1038/s41583-019-0197-2] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Light-controllable tools provide powerful means to manipulate and interrogate brain function with relatively low invasiveness and high spatiotemporal precision. Although optogenetic approaches permit neuronal excitation or inhibition at the network level, other technologies, such as optopharmacology (also known as photopharmacology) have emerged that provide molecular-level control by endowing light sensitivity to endogenous biomolecules. In this Review, we discuss the challenges and opportunities of photocontrolling native neuronal signalling pathways, focusing on ion channels and neurotransmitter receptors. We describe existing strategies for rendering receptors and channels light sensitive and provide an overview of the neuroscientific insights gained from such approaches. At the crossroads of chemistry, protein engineering and neuroscience, optopharmacology offers great potential for understanding the molecular basis of brain function and behaviour, with promises for future therapeutics.
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Affiliation(s)
- Pierre Paoletti
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France.
| | | | - Alexandre Mourot
- Neuroscience Paris Seine-Institut de Biologie Paris Seine (NPS-IBPS), CNRS, INSERM, Sorbonne Université, Paris, France.
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12
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Genetically Encoding Unnatural Amino Acids in Neurons In Vitro and in the Embryonic Mouse Brain for Optical Control of Neuronal Proteins. Methods Mol Biol 2018; 1728:263-277. [PMID: 29405004 DOI: 10.1007/978-1-4939-7574-7_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
Deciphering neuronal networks governing specific brain functions is a longstanding mission in neuroscience, yet global manipulation of protein functions pharmacologically or genetically lacks sufficient specificity to reveal a neuronal protein's function in a particular neuron or a circuitry. Photostimulation presents a great venue for researchers to control neuronal proteins with high temporal and spatial resolution. Recently, an approach to optically control the function of a neuronal protein directly in neurons has been demonstrated using genetically encoded light-sensitive Unnatural amino acids (Uaas). Here, we describe procedures for genetically incorporating Uaas into target neuronal proteins in neurons in vitro and in embryonic mouse brain. As an example, a photocaged Uaa was incorporated into an inwardly rectifying potassium channel Kir2.1 to render Kir2.1 photo-activatable. This method has the potential to be generally applied to many neuronal proteins to achieve optical regulation of different processes in brains. Uaas with other properties can be similarly incorporated into neuronal proteins in neurons for various applications.
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13
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Huang S, Feng L, An G, Zhang X, Zhao Z, Han R, Lei F, Zhang Y, Luo A, Jing X, Zhao L, Gu S, Zhao X, Zhang L. Ribosome display and selection of single-chain variable fragments effectively inhibit growth and progression of microspheres in vitro and in vivo. Cancer Sci 2018; 109:1503-1512. [PMID: 29575477 PMCID: PMC5980252 DOI: 10.1111/cas.13574] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 12/14/2022] Open
Abstract
Distinguishing the surface markers of cancer stem cells (CSCs) is a useful method for early diagnosis and treatment of tumors, as CSCs may participate in tumorigenesis and metastasis by migrating into the circulatory system. However, the potential targets of CSCs are expressed at low levels in the natural state and are always changing. Thus, dynamic screening has been reported to be an effective measure for exploring CSC markers. In recent years, diverse single-chain variable fragments (scFvs) have been widely used in immunotherapy. In this study, we determined that the scFvs, screened using RD, had a high affinity to microspheres and could inhibit their progression. We also observed that the selected scFvs underwent evolution in vitro, and antitumor-associated proteins were successfully expressed. Combined with chemotherapy, the scFvs had a synergistic effect on the inhibition of the microspheres' progression in vitro and in vivo, which could be ascribed to their high affinity for stem-like cells and the inhibition of the microspheres' collective behaviors. In addition, proteins inhibiting CD44+ /CD24+ and MAPK were involved. Our data indicated that dynamic screening of the scFvs in a natural state was of great significance in the inhibition of the microspheres in vitro and in vivo.
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Affiliation(s)
- Shangke Huang
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Lu Feng
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Gaili An
- Department of Clinical Oncology, Shaanxi Provincial People's Hospital, Xi'an, China
| | - Xiaojin Zhang
- Department of The Medical School of Shaoxing University, Shaoxing, China
| | - Zixuan Zhao
- Elite Property Management Ltd., Saskatoon, SK, Canada
| | - Rui Han
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Fuxi Lei
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yujiao Zhang
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Anqi Luo
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Jing
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Lin Zhao
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Shanzhi Gu
- College of Forensic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Xinhan Zhao
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Lingxiao Zhang
- Department of Medical Oncology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
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14
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Klippenstein V, Mony L, Paoletti P. Probing Ion Channel Structure and Function Using Light-Sensitive Amino Acids. Trends Biochem Sci 2018; 43:436-451. [PMID: 29650383 DOI: 10.1016/j.tibs.2018.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 02/25/2018] [Accepted: 02/27/2018] [Indexed: 12/13/2022]
Abstract
Approaches to remotely control and monitor ion channel operation with light are expanding rapidly in the biophysics and neuroscience fields. A recent development directly introduces light sensitivity into proteins by utilizing photosensitive unnatural amino acids (UAAs) incorporated using the genetic code expansion technique. The introduction of UAAs results in unique molecular level control and, when combined with the maximal spatiotemporal resolution and poor invasiveness of light, enables direct manipulation and interrogation of ion channel functionality. Here, we review the diverse applications of light-sensitive UAAs in two superfamilies of ion channels (voltage- and ligand-gated ion channels; VGICs and LGICs) and summarize existing UAA tools, their mode of action, potential, caveats, and technical considerations to their use in illuminating ion channel structure and function.
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Affiliation(s)
- Viktoria Klippenstein
- Institut de Biologie de I'ENS (IBENS), CNRS UMR8197, INSERM U1024, Ecole Normale Supérieure, Université PSL, 46 rue d'Ulm, 75005 Paris, France; These authors contributed equally to this work
| | - Laetitia Mony
- Institut de Biologie de I'ENS (IBENS), CNRS UMR8197, INSERM U1024, Ecole Normale Supérieure, Université PSL, 46 rue d'Ulm, 75005 Paris, France; These authors contributed equally to this work
| | - Pierre Paoletti
- Institut de Biologie de I'ENS (IBENS), CNRS UMR8197, INSERM U1024, Ecole Normale Supérieure, Université PSL, 46 rue d'Ulm, 75005 Paris, France.
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15
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Macdonald LC, Kim RY, Kurata HT, Fedida D. Probing the molecular basis of hERG drug block with unnatural amino acids. Sci Rep 2018; 8:289. [PMID: 29321549 PMCID: PMC5762913 DOI: 10.1038/s41598-017-18448-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/11/2017] [Indexed: 11/30/2022] Open
Abstract
Repolarization of the cardiac action potential is primarily mediated by two voltage-dependent potassium currents: IKr and IKs. The voltage-gated potassium channel that gives rise to IKr, Kv11.1 (hERG), is uniquely susceptible to high-affinity block by a wide range of drug classes. Pore residues Tyr652 and Phe656 are critical to potent drug interaction with hERG. It is considered that the molecular basis of this broad-spectrum drug block phenomenon occurs through interactions specific to the aromatic nature of the side chains at Tyr652 and Phe656. In this study, we used nonsense suppression to incorporate singly and doubly fluorinated phenylalanine residues at Tyr652 and Phe656 to assess cation-π interactions in hERG terfenadine, quinidine, and dofetilide block. Incorporation of these unnatural amino acids was achieved with minimal alteration to channel activation or inactivation gating. Our assessment of terfenadine, quinidine, and dofetilide block did not reveal evidence of a cation-π interaction at either aromatic residue, but, interestingly, shows that certain fluoro-Phe substitutions at position 652 result in weaker drug potency.
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Affiliation(s)
- Logan C Macdonald
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Robin Y Kim
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Harley T Kurata
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
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16
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Park SH, Kwon JS, Lee BS, Park JH, Lee BK, Yun JH, Lee BY, Kim JH, Min BH, Yoo TH, Kim MS. BMP2-modified injectable hydrogel for osteogenic differentiation of human periodontal ligament stem cells. Sci Rep 2017; 7:6603. [PMID: 28747761 PMCID: PMC5529463 DOI: 10.1038/s41598-017-06911-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 06/19/2017] [Indexed: 12/22/2022] Open
Abstract
This is the first report on the development of a covalently bone morphogenetic protein-2 (BMP2)-immobilized hydrogel that is suitable for osteogenic differentiation of human periodontal ligament stem cells (hPLSCs). O-propargyl-tyrosine (OpgY) was site-specifically incorporated into BMP2 to prepare BMP2-OpgY with an alkyne group. The engineered BMP2-OpgY exhibited osteogenic characteristics after in vitro osteogenic differentiation of hPLSCs, indicating the osteogenic ability of BMP2-OpgY. A methoxy polyethylene glycol-(polycaprolactone-(N3)) block copolymer (MC-N3) was prepared as an injectable in situ-forming hydrogel. BMP2 covalently immobilized on an MC hydrogel (MC-BMP2) was prepared quantitatively by a simple biorthogonal reaction between alkyne groups on BMP2-OpgY and azide groups on MC-N3 via a Cu(I)-catalyzed click reaction. The hPLSCs-loaded MC-BMP2 formed a hydrogel almost immediately upon injection into animals. In vivo osteogenic differentiation of hPLSCs in the MC-BMP2 formulation was confirmed by histological staining and gene expression analyses. Histological staining of hPLSC-loaded MC-BMP2 implants showed evidence of mineralized calcium deposits, whereas hPLSC-loaded MC-Cl or BMP2-OpgY mixed with MC-Cl, implants showed no mineral deposits. Additionally, MC-BMP2 induced higher levels of osteogenic gene expression in hPLSCs than in other groups. In conclusion, BMP2-OpgY covalently immobilized on MC-BMP2 induced osteogenic differentiation of hPLSCs as a noninvasive method for bone tissue engineering.
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Affiliation(s)
- Seung Hun Park
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Jin Seon Kwon
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Byeong Sung Lee
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Ji Hoon Park
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Bo Keun Lee
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Jeong-Ho Yun
- Department of Periodontology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju, 561-712, Korea
| | - Bun Yeoul Lee
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Jae Ho Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Byoung Hyun Min
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea
| | - Tae Hyeon Yoo
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea.
| | - Moon Suk Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, 443-749, Korea.
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17
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Nair RN, Rosnow JJ, Murphree TA, Bowden ME, Lindemann SR, Wright AT. De novo synthesis of alkyne substituted tryptophans as chemical probes for protein profiling studies. Org Chem Front 2017; 4:495-499. [PMID: 28944064 PMCID: PMC5607013 DOI: 10.1039/c6qo00819d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
De novo synthesis of alkynalted tryptophan moieties as chemical probes for protein profilling studies, via an unexpected synthesis of Michael acceptor 12 is reported. Friedel Craft's alkylation of 12 and alkyne substituted indoles gave alkynalated tryptophan moieties, which perform as chemical probe by incorporating into actively translating Escherichia coli cells, whereby the alkyne moiety enables multimodal analyses through click chemistry mediated attachment of reporting groups.
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Affiliation(s)
- R N Nair
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland. WA
- R. N. Nair. Current address - David Geffen School of Medicine, Department of Psychiatry and Behavorial Sciences, University of California, Los Angeles
| | - J J Rosnow
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland. WA
| | - T A Murphree
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland. WA
| | - M E Bowden
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland. WA
| | - S R Lindemann
- S. R. Lindemann. Current address - Department of Food Science, Purdue University, West Lafayette, IN
| | - A T Wright
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland. WA
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18
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Zhu X, Shinohara H, Miyatake R, Hohsaka T. Novel biosensor system model based on fluorescence quenching by a fluorescent streptavidin and carbazole-labeled biotin. J Mol Recognit 2016; 29:485-91. [DOI: 10.1002/jmr.2548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/18/2016] [Accepted: 04/06/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Xianwei Zhu
- Innovation Research Centre of Acupuncture Combined with Medicine; Shaanxi University of Chinese Medicine; Xi'an-Xianyang New Ecomic Zone Shaanxi Province 712046 China
| | - Hiroaki Shinohara
- Graduate School of Science and Engineering for Research; University of Toyama; 3190 Gofuku Toyama 930-8555 Japan
| | - Ryuta Miyatake
- Graduate School of Science and Engineering for Research; University of Toyama; 3190 Gofuku Toyama 930-8555 Japan
| | - Takahiro Hohsaka
- School of Materials Science; Japan Advanced Institute of Science and Technology; 1-1 Asahidai Nomi Ishikawa 923-1292 Japan
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19
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Kang JY, Kawaguchi D, Wang L. Optical Control of a Neuronal Protein Using a Genetically Encoded Unnatural Amino Acid in Neurons. J Vis Exp 2016:e53818. [PMID: 27078635 DOI: 10.3791/53818] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Photostimulation is a noninvasive way to control biological events with excellent spatial and temporal resolution. New methods are desired to photo-regulate endogenous proteins expressed in their native environment. Here, we present an approach to optically control the function of a neuronal protein directly in neurons using a genetically encoded unnatural amino acid (Uaa). By using an orthogonal tRNA/aminoacyl-tRNA synthetase pair to suppress the amber codon, a photo-reactive Uaa 4,5-dimethoxy-2-nitrobenzyl-cysteine (Cmn) is site-specifically incorporated in the pore of a neuronal protein Kir2.1, an inwardly rectifying potassium channel. The bulky Cmn physically blocks the channel pore, rendering Kir2.1 non-conducting. Light illumination instantaneously converts Cmn into a smaller natural amino acid Cys, activating Kir2.1 channel function. We express these photo-inducible inwardly rectifying potassium (PIRK) channels in rat hippocampal primary neurons, and demonstrate that light-activation of PIRK ceases the neuronal firing due to the outflux of K(+) current through the activated Kir2.1 channels. Using in utero electroporation, we also express PIRK in the embryonic mouse neocortex in vivo, showing the light-activation of PIRK in neocortical neurons. Genetically encoding Uaa imposes no restrictions on target protein type or cellular location, and a family of photoreactive Uaas is available for modulating different natural amino acid residues. This technique thus has the potential to be generally applied to many neuronal proteins to achieve optical regulation of different processes in brains. The current protocol presents an accessible procedure for intricate Uaa incorporation in neurons in vitro and in vivo to achieve photo control of neuronal protein activity on the molecular level.
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Affiliation(s)
- Ji-Yong Kang
- Department of Neuroscience, School of Medicine, Tufts University
| | - Daichi Kawaguchi
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies
| | - Lei Wang
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California, San Francisco;
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20
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Zhu W, Varga Z, Silva JR. Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:3-17. [PMID: 26724572 DOI: 10.1016/j.pbiomolbio.2015.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/11/2015] [Accepted: 12/16/2015] [Indexed: 01/04/2023]
Abstract
Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models.
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Affiliation(s)
- Wandi Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Zoltan Varga
- MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Debrecen, Hungary
| | - Jonathan R Silva
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA.
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21
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Kim RY, Yau MC, Galpin JD, Seebohm G, Ahern CA, Pless SA, Kurata HT. Atomic basis for therapeutic activation of neuronal potassium channels. Nat Commun 2015; 6:8116. [PMID: 26333338 PMCID: PMC4561856 DOI: 10.1038/ncomms9116] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 07/21/2015] [Indexed: 12/25/2022] Open
Abstract
Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2–5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific chemical interactions required for retigabine action. Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp. Supporting this model, substitution with fluorinated Trp analogues, with increased H-bonding propensity, strengthens retigabine potency. In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators. These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators. The antiepileptic drug retigabine potentiates neuronal KCNQ potassium channels. Here, the authors use a combination of unnatural amino acid mutagenesis and electrophysiology to show that retigabine acts by hydrogen bonding with a tryptophan indole nitrogen in the channel pore.
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Affiliation(s)
- Robin Y Kim
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - Michael C Yau
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - Jason D Galpin
- Department of Molecular Physiology and Biophysics, University of Iowa, 285 Newton Road, Iowa City, Iowa 52242, USA
| | - Guiscard Seebohm
- Department of Cardiovascular Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1 (Gebäude D3), D-48149 Münster, Germany
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, 285 Newton Road, Iowa City, Iowa 52242, USA
| | - Stephan A Pless
- Department of Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark
| | - Harley T Kurata
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
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22
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Zhang RS, Wright JD, Pless SA, Nunez JJ, Kim RY, Li JBW, Yang R, Ahern CA, Kurata HT. A Conserved Residue Cluster That Governs Kinetics of ATP-dependent Gating of Kir6.2 Potassium Channels. J Biol Chem 2015; 290:15450-15461. [PMID: 25934393 DOI: 10.1074/jbc.m114.631960] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Indexed: 12/13/2022] Open
Abstract
ATP-sensitive potassium (KATP) channels are heteromultimeric complexes of an inwardly rectifying Kir channel (Kir6.x) and sulfonylurea receptors. Their regulation by intracellular ATP and ADP generates electrical signals in response to changes in cellular metabolism. We investigated channel elements that control the kinetics of ATP-dependent regulation of KATP (Kir6.2 + SUR1) channels using rapid concentration jumps. WT Kir6.2 channels re-open after rapid washout of ATP with a time constant of ∼60 ms. Extending similar kinetic measurements to numerous mutants revealed fairly modest effects on gating kinetics despite significant changes in ATP sensitivity and open probability. However, we identified a pair of highly conserved neighboring amino acids (Trp-68 and Lys-170) that control the rate of channel opening and inhibition in response to ATP. Paradoxically, mutations of Trp-68 or Lys-170 markedly slow the kinetics of channel opening (500 and 700 ms for W68L and K170N, respectively), while increasing channel open probability. Examining the functional effects of these residues using φ value analysis revealed a steep negative slope. This finding implies that these residues play a role in lowering the transition state energy barrier between open and closed channel states. Using unnatural amino acid incorporation, we demonstrate the requirement for a planar amino acid at Kir6.2 position 68 for normal channel gating, which is potentially necessary to localize the ϵ-amine of Lys-170 in the phosphatidylinositol 4,5-bisphosphate-binding site. Overall, our findings identify a discrete pair of highly conserved residues with an essential role for controlling gating kinetics of Kir channels.
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Affiliation(s)
- Roger S Zhang
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Jordan D Wright
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Stephan A Pless
- Department of Drug Design and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - John-Jose Nunez
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Robin Y Kim
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Jenny B W Li
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Runying Yang
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52246
| | - Harley T Kurata
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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23
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Pless SA, Kim RY, Ahern CA, Kurata HT. Atom-by-atom engineering of voltage-gated ion channels: magnified insights into function and pharmacology. J Physiol 2015; 593:2627-34. [PMID: 25640301 DOI: 10.1113/jphysiol.2014.287714] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/26/2015] [Indexed: 12/12/2022] Open
Abstract
Unnatural amino acid incorporation into ion channels has proven to be a valuable approach to interrogate detailed hypotheses arising from atomic resolution structures. In this short review, we provide a brief overview of some of the basic principles and methods for incorporation of unnatural amino acids into proteins. We also review insights into the function and pharmacology of voltage-gated ion channels that have emerged from unnatural amino acid mutagenesis approaches.
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Affiliation(s)
- Stephan A Pless
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Robin Y Kim
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | | | - Harley T Kurata
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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24
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Subramanyam P, Colecraft HM. Ion channel engineering: perspectives and strategies. J Mol Biol 2014; 427:190-204. [PMID: 25205552 DOI: 10.1016/j.jmb.2014.09.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 09/01/2014] [Indexed: 01/19/2023]
Abstract
Ion channels facilitate the passive movement of ions down an electrochemical gradient and across lipid bilayers in cells. This phenomenon is essential for life and underlies many critical homeostatic processes in cells. Ion channels are diverse and differ with respect to how they open and close (gating) and to their ionic conductance/selectivity (permeation). Fundamental understanding of ion channel structure-function mechanisms, their physiological roles, how their dysfunction leads to disease, their utility as biosensors, and development of novel molecules to modulate their activity are important and active research frontiers. In this review, we focus on ion channel engineering approaches that have been applied to investigate these aspects of ion channel function, with a major emphasis on voltage-gated ion channels.
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Affiliation(s)
- Prakash Subramanyam
- Department of Physiology and Cellular Biophysics, Columbia University, NY, 10032, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, NY, 10032, USA.
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25
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Dougherty DA, Van Arnam EB. In vivo incorporation of non-canonical amino acids by using the chemical aminoacylation strategy: a broadly applicable mechanistic tool. Chembiochem 2014; 15:1710-20. [PMID: 24990307 DOI: 10.1002/cbic.201402080] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Indexed: 01/05/2023]
Abstract
We describe a strategy for incorporating non-canonical amino acids site-specifically into proteins expressed in living cells, involving organic synthesis to chemically aminoacylate a suppressor tRNA, protein expression in Xenopus oocytes, and monitoring protein function, primarily by electrophysiology. With this protocol, a very wide range of non-canonical amino acids can be employed, allowing both systematic structure-function studies and the incorporation of reactive functionalities. Here, we present an overview of the methodology and examples meant to illustrate the versatility and power of the method as a tool for investigating protein structure and function.
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Affiliation(s)
- Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (USA).
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26
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Fluorescence enhancement of fluorescent unnatural streptavidin by binding of a biotin analogue with spacer tail and its application to biotin sensing. ScientificWorldJournal 2014; 2014:165369. [PMID: 24790550 PMCID: PMC3980882 DOI: 10.1155/2014/165369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 12/23/2013] [Indexed: 11/24/2022] Open
Abstract
We designed a novel molecular biosensing system for the detection of biotin, an important vitamin by the combination of fluorescent unnatural streptavidin with a commercialized biotin-(AC5)2-hydrazide. A fluorescent unnatural amino acid, BODIPY-FL-aminophenylalanine (BFLAF), was position-specifically incorporated into Trp120 of streptavidin by four-base codon method. Fluorescence of the Trp120BFLAF mutant streptavidin was enhanced by the addition of biotin-(AC5)2-hydrazide with the concentration dependent, whereas fluorescence enhancement was not observed at all by the addition of natural biotin. It was considered that the spacer tail of biotin-(AC5)2-hydrazide may disturb the fluorescence quenching of the Trp120BFLAF by Trp79 and Trp108 of the neighbor subunit. Therefore, biotin sensing was carried out by the competitive binding reaction of biotin-(AC5)2-hydrazide and natural biotin to the fluorescent mutant streptavidin. The fluorescence intensity decreased by increasing free biotin concentration. The result suggested that molecular biosensor for small ligand could be successfully designed by the pair of fluorescent mutant binding protein and ligand analogue.
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27
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An amino acid depleted cell-free protein synthesis system for the incorporation of non-canonical amino acid analogs into proteins. J Biotechnol 2014; 178:12-22. [DOI: 10.1016/j.jbiotec.2014.02.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 02/08/2014] [Accepted: 02/14/2014] [Indexed: 11/19/2022]
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28
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Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces. Proc Natl Acad Sci U S A 2014; 111:6081-6. [PMID: 24715733 DOI: 10.1073/pnas.1318808111] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo-cross-linker p-azido-L-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion.
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29
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Abstract
Ionotropic glutamate receptors (iGluRs) are ubiquitous in the mammalian brain, and the AMPA-subtype is essential for fast, glutamate-activated postsynaptic currents. We incorporated photoactive crosslinkers into AMPA receptors using genetically encoded unnatural amino acid mutagenesis in a mammalian cell line. Receptors rescued by incorporation of unnatural amino acids, including p-benzoyl-l-phenylalanine (BzF, also known as Bpa), had largely similar properties to wild-type channels and were expressed at similar levels. BzF incorporation at subunit interfaces afforded photocrosslinking of subunits, as assessed by biochemical experiments. In electrophysiological recordings, BzF incorporation allowed selective and potent UV-driven photoinactivation of both homomeric (GluA2) and heteromeric (GluA2:GluA1) AMPA receptors. State dependence of trapping at two sites in the lower lobe of the ligand binding domain is consistent with deformation of these domains as well as intersubunit rearrangements during AMPA receptor desensitization.
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30
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Kang JY, Kawaguchi D, Coin I, Xiang Z, O'Leary DDM, Slesinger PA, Wang L. In vivo expression of a light-activatable potassium channel using unnatural amino acids. Neuron 2014; 80:358-70. [PMID: 24139041 DOI: 10.1016/j.neuron.2013.08.016] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/09/2013] [Indexed: 01/28/2023]
Abstract
Optical control of protein function provides excellent spatial-temporal resolution for studying proteins in situ. Although light-sensitive exogenous proteins and ligands have been used to manipulate neuronal activity, a method for optical control of neuronal proteins using unnatural amino acids (Uaa) in vivo is lacking. Here, we describe the genetic incorporation of a photoreactive Uaa into the pore of an inwardly rectifying potassium channel Kir2.1. The Uaa occluded the pore, rendering the channel nonconducting, and, on brief light illumination, was released to permit outward K(+) current. Expression of this photoinducible inwardly rectifying potassium (PIRK) channel in rat hippocampal neurons created a light-activatable PIRK switch for suppressing neuronal firing. We also expanded the genetic code of mammals to express PIRK channels in embryonic mouse neocortex in vivo and demonstrated a light-activated PIRK current in cortical neurons. These principles could be generally expanded to other proteins expressed in the brain to enable optical regulation.
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Affiliation(s)
- Ji-Yong Kang
- The Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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31
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Lin-Moshier Y, Marchant JS. The Xenopus oocyte: a single-cell model for studying Ca2+ signaling. Cold Spring Harb Protoc 2013; 2013:2013/3/pdb.top066308. [PMID: 23457336 DOI: 10.1101/pdb.top066308] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the four decades since the Xenopus oocyte was first demonstrated to have the capacity to translate exogenous mRNAs, this system has been exploited for many different experimental purposes. Typically, the oocyte is used either as a "biological test tube" for heterologous expression of proteins without any particular cell biological insight or, alternatively, it is used for applications where cell biology is paramount, such as investigations of the cellular adaptations that power early development. In this article, we discuss the utility of the Xenopus oocyte for studying Ca(2+) signaling in both these contexts.
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Affiliation(s)
- Yaping Lin-Moshier
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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32
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Naganathan S, Ye S, Sakmar TP, Huber T. Site-specific epitope tagging of G protein-coupled receptors by bioorthogonal modification of a genetically encoded unnatural amino acid. Biochemistry 2013; 52:1028-36. [PMID: 23317030 DOI: 10.1021/bi301292h] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We developed a general strategy for labeling expressed membrane proteins with a peptide epitope tag and detecting the tagged proteins in native cellular membranes. First, we genetically encoded the unnatural amino acid p-azido-L-phenylalanine (azF) at various specific sites in a G protein-coupled receptor (GPCR), C-C chemokine receptor 5 (CCR5). The reactive azido moiety facilitates Staudinger ligation to a triarylphosphine-conjugated FLAG peptide. We then developed a whole-cell-based enzyme-linked immunosorbent assay approach to detect the modified azF-CCR5 using anti-FLAG mAb. We optimized conditions to achieve labeling and detection of low-abundance GPCRs in live cells. We also performed an accessibility screen to identify azF positions on CCR5 amenable to labeling. Finally, we demonstrate a preparative strategy for obtaining pure bioorthogonally modified GPCRs suitable for single-molecule detection fluorescence experiments. This peptide epitope tagging strategy, which employs genetic encoding and bioorthogonal labeling of azF in live cells, should be useful for studying biogenesis of polytopic membrane proteins and GPCR signaling mechanisms.
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Affiliation(s)
- Saranga Naganathan
- Laboratory of Chemical Biology and Signal Transduction, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
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33
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Niu W, Guo J. Expanding the chemistry of fluorescent protein biosensors through genetic incorporation of unnatural amino acids. MOLECULAR BIOSYSTEMS 2013; 9:2961-70. [DOI: 10.1039/c3mb70204a] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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34
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Abstract
Ion channels, as membrane proteins, are the sensors of the cell. They act as the first line of communication with the world beyond the plasma membrane and transduce changes in the external and internal environments into unique electrical signals to shape the responses of excitable cells. Because of their importance in cellular communication, ion channels have been intensively studied at the structural and functional levels. Here, we summarize the diverse approaches, including molecular and cellular, chemical, optical, biophysical, and computational, used to probe the structural and functional rearrangements that occur during channel activation (or sensitization), inactivation (or desensitization), and various forms of modulation. The emerging insights into the structure and function of ion channels by multidisciplinary approaches allow the development of new pharmacotherapies as well as new tools useful in controlling cellular activity.
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Affiliation(s)
- Wei-Guang Li
- Neuroscience Division, Department of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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35
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Genetically encoded libraries of nonstandard peptides. J Nucleic Acids 2012; 2012:713510. [PMID: 23097693 PMCID: PMC3477784 DOI: 10.1155/2012/713510] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 08/12/2012] [Indexed: 11/17/2022] Open
Abstract
The presence of a nonproteinogenic moiety in a nonstandard peptide often improves the biological properties of the peptide. Non-standard peptide libraries are therefore used to obtain valuable molecules for biological, therapeutic, and diagnostic applications. Highly diverse non-standard peptide libraries can be generated by chemically or enzymatically modifying standard peptide libraries synthesized by the ribosomal machinery, using posttranslational modifications. Alternatively, strategies for encoding non-proteinogenic amino acids into the genetic code have been developed for the direct ribosomal synthesis of non-standard peptide libraries. In the strategies for genetic code expansion, non-proteinogenic amino acids are assigned to the nonsense codons or 4-base codons in order to add these amino acids to the universal genetic code. In contrast, in the strategies for genetic code reprogramming, some proteinogenic amino acids are erased from the genetic code and non-proteinogenic amino acids are reassigned to the blank codons. Here, we discuss the generation of genetically encoded non-standard peptide libraries using these strategies and also review recent applications of these libraries to the selection of functional non-standard peptides.
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36
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Shokri A, Abedin A, Fattahi A, Kass SR. Effect of Hydrogen Bonds on pKa Values: Importance of Networking. J Am Chem Soc 2012; 134:10646-50. [DOI: 10.1021/ja3037349] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alireza Shokri
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455,
United States
| | - Azardokht Abedin
- Department
of Chemistry, Sharif University of Technology, Tehran, Iran
| | - Alireza Fattahi
- Department
of Chemistry, Sharif University of Technology, Tehran, Iran
| | - Steven R. Kass
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455,
United States
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37
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Yamaguchi A, Hohsaka T. Synthesis of Novel BRET/FRET Protein Probes Containing Light-Emitting Proteins and Fluorescent Nonnatural Amino Acids. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2012. [DOI: 10.1246/bcsj.20110368] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Atsushi Yamaguchi
- School of Materials Science, Japan Advanced Institute of Science and Technology
| | - Takahiro Hohsaka
- School of Materials Science, Japan Advanced Institute of Science and Technology
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38
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39
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Wang K, Schmied WH, Chin JW. Reprogramming the genetic code: from triplet to quadruplet codes. Angew Chem Int Ed Engl 2012; 51:2288-97. [PMID: 22262408 DOI: 10.1002/anie.201105016] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Indexed: 11/10/2022]
Abstract
The genetic code of cells is near-universally triplet, and since many ribosomal mutations are lethal, changing the cellular ribosome to read nontriplet codes is challenging. Herein we review work on the incorporation of unnatural amino acids into proteins in response to quadruplet codons, and the creation of an orthogonal translation system in the cell that uses an evolved orthogonal ribosome to efficiently direct the incorporation of unnatural amino acids in response to quadruplet codons. Using this system multiple distinct unnatural amino acids have been incorporated and used to genetically program emergent properties into recombinant proteins. Extension of approaches to incorporate multiple unnatural amino acids may allow the combinatorial biosynthesis of materials and therapeutics, and drive investigations into whether life with additional genetically encoded polymers can evolve to perform functions that natural biological systems cannot.
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Affiliation(s)
- Kaihang Wang
- Medical Research Council Laboratory of Molecular Biology, Hills Rd, Cambridge, CB2 0QH UK
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40
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Wang K, Schmied WH, Chin JW. Die Umprogrammierung des genetischen Codes: vom Triplett- zum Quadruplettcode. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201105016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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41
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Two amino acid residues contribute to a cation-π binding interaction in the binding site of an insect GABA receptor. J Neurosci 2011; 31:12371-6. [PMID: 21865479 DOI: 10.1523/jneurosci.1610-11.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Cys-loop receptor binding sites characteristically possess an "aromatic box," where several aromatic amino acid residues surround the bound ligand. A cation-π interaction between one of these residues and the natural agonist is common, although the residue type and location are not conserved. Even in the closely related vertebrate GABA(A) and GABA(C) receptors, residues in distinct locations perform this role: in GABA(A) receptors, a Tyr residue in loop A forms a cation-π interaction with GABA, while in GABA(C) receptors it is a loop B residue. GABA-activated Cys-loop receptors also exist in invertebrates, where they have distinct pharmacologies and are the target of a range of pesticides. Here we examine the location of GABA in an insect binding site by incorporating a series of fluorinated Phe derivatives into the receptor binding pocket using unnatural amino acid mutagenesis, and evaluating the resulting receptors when expressed in Xenopus oocytes. A homology model suggests that two aromatic residues (in loops B and C) are positioned such that they could contribute to a cation-π interaction with the primary ammonium of GABA, and the data reveal a clear correlation between the GABA EC(50) and the cation-π binding ability both at Phe206 (loop B) and Tyr254 (loop C), demonstrating for the first time the contribution of two aromatic residues to a cation-π interaction in a Cys-loop receptor.
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42
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Blum AP, Gleitsman KR, Lester HA, Dougherty DA. Evidence for an extended hydrogen bond network in the binding site of the nicotinic receptor: role of the vicinal disulfide of the alpha1 subunit. J Biol Chem 2011; 286:32251-8. [PMID: 21757705 DOI: 10.1074/jbc.m111.254235] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The defining feature of the α subunits of the family of nicotinic acetylcholine receptors is a vicinal disulfide between Cys-192 and Cys-193. Although this structure has played a pivotal role in a number of pioneering studies of nicotinic receptors, its functional role in native receptors remains uncertain. Using mutant cycle analysis and unnatural residue mutagenesis, including backbone mutagenesis of the peptide bond of the vicinal disulfide, we have established the presence of a network of hydrogen bonds that extends from that peptide NH, across a β turn to another backbone hydrogen bond, and then across the subunit interface to the side chain of a functionally important Asp residue in the non-α subunit. We propose that the role of the vicinal disulfide is to distort the β turn and thereby properly position a backbone NH for intersubunit hydrogen bonding to the key Asp.
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Affiliation(s)
- Angela P Blum
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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43
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Pless SA, Hanek AP, Price KL, Lynch JW, Lester HA, Dougherty DA, Lummis SCR. A cation-π interaction at a phenylalanine residue in the glycine receptor binding site is conserved for different agonists. Mol Pharmacol 2011; 79:742-8. [PMID: 21266487 DOI: 10.1124/mol.110.069583] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cation-π interactions have been demonstrated to play a major role in agonist-binding in Cys-loop receptors. However, neither the aromatic amino acid contributing to this interaction nor its location is conserved among Cys-loop receptors. Likewise, it is not clear how many different agonists of a given receptor form a cation-π interaction or, if they do, whether it is with the same aromatic amino acid as the major physiological agonist. We demonstrated previously that Phe159 in the glycine receptor (GlyR) α1 subunit forms a strong cation-π interaction with the principal agonist, glycine. In the current study, we investigated whether the lower efficacy agonists of the human GlyR β-alanine and taurine also form cation-π interactions with Phe159. By incorporating a series of unnatural amino acids, we found cation-π interactions between Phe159 and the amino groups of β-alanine and taurine. The strengths of these interactions were significantly weaker than for glycine. Modeling studies suggest that β-alanine and taurine are orientated subtly differently in the binding pocket, with their amino groups further from Phe159 than that of glycine. These data therefore show that similar agonists can have similar but not identical orientations and interactions in the binding pocket and provide a possible explanation for the lower potencies of β-alanine and taurine.
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Affiliation(s)
- Stephan A Pless
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
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44
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Small photoactivatable molecules for controlled fluorescence activation in living cells. Bioorg Med Chem 2010; 19:1023-9. [PMID: 20675143 DOI: 10.1016/j.bmc.2010.07.011] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 07/01/2010] [Accepted: 07/07/2010] [Indexed: 11/23/2022]
Abstract
The search for chemical probes which allow a controlled fluorescence activation in living cells represent a major challenge in chemical biology. To be useful, such probes have to be specifically targeted to cellular proteins allowing thereof the analysis of dynamic aspects of this protein in its cellular environment. The present paper describes different methods which have been developed to control cellular fluorescence activation emphasizing the photochemical activation methods known to be orthogonal to most cellular components and, in addition, allowing a spatio-temporal controlled triggering of the fluorescent signal.
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45
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46
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Abstract
The ability to selectively conduct K(+) ions is central to the function of K(+) channels. Selection for K(+) and rejection of Na(+) takes place in a conserved structural element referred to as the selectivity filter. The selectivity filter consists of four K(+)-specific ion binding sites that are created using predominantly the backbone carbonyl oxygen atoms. Due to the involvement of the protein backbone, experimental manipulation of the ion binding sites in the selectivity filter is not possible using traditional site directed mutagenesis. The limited suitability of the site-directed mutagenesis for studies on the selectivity filter has motivated the development of a semisynthesis approach, which enables the use of chemical synthesis to manipulate the selectivity filter. In this chapter, we describe the protocols that are presently used in our laboratory for the semisynthesis of the bacterial K(+) channel, KcsA. We show the introduction of a spectroscopic probe into the KcsA channel using semisynthesis. We also review previous applications of semisynthesis in investigations of K(+) channels. While the protocols described in this chapter are for the KcsA K(+) channel, we anticipate that similar protocols will also be applicable for the semisynthesis of other integral membrane proteins.
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Affiliation(s)
- Alexander G Komarov
- Program in Chemical Biology, Department of Physiology and Pharmacology, Oregon Health and Sciences University, Portland, Oregon, USA
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47
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Specht A, Bolze F, Omran Z, Nicoud JF, Goeldner M. Photochemical tools to study dynamic biological processes. HFSP JOURNAL 2009; 3:255-64. [PMID: 20119482 PMCID: PMC2799987 DOI: 10.2976/1.3132954] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 04/21/2009] [Indexed: 11/19/2022]
Abstract
Light-responsive biologically active compounds offer the possibility to study the dynamics of biological processes. Phototriggers and photoswitches have been designed, providing the capability to rapidly cause the initiation of wide range of dynamic biological phenomena. We will discuss, in this article, recent developments in the field of light-triggered chemical tools, specially how two-photon excitation, "caged" fluorophores, and the photoregulation of protein activities in combination with time-resolved x-ray techniques should break new grounds in the understanding of dynamic biological processes.
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Affiliation(s)
- Alexandre Specht
- Laboratoire de Conception et Application de Molécules Bioactives, Faculté de Pharmacie, UMR 7199, Université de Strasbourg-CNRS, 74 route du Rhin, F-67401 Illkirch-Graffenstaden Cedex, France
| | - Frédéric Bolze
- Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, UMR 7213, Université de Strasbourg-CNRS, 74 route du Rhin, F-67401 Illkirch-Graffenstaden Cedex, France
| | - Ziad Omran
- Laboratoire de Conception et Application de Molécules Bioactives, Faculté de Pharmacie, UMR 7199, Université de Strasbourg-CNRS, 74 route du Rhin, F-67401 Illkirch-Graffenstaden Cedex, France
| | - Jean-François Nicoud
- Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, UMR 7213, Université de Strasbourg-CNRS, 74 route du Rhin, F-67401 Illkirch-Graffenstaden Cedex, France
| | - Maurice Goeldner
- Laboratoire de Conception et Application de Molécules Bioactives, Faculté de Pharmacie, UMR 7199, Université de Strasbourg-CNRS, 74 route du Rhin, F-67401 Illkirch-Graffenstaden Cedex, France
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48
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Triggle DJ. The chemist as astronaut: Searching for biologically useful space in the chemical universe. Biochem Pharmacol 2009; 78:217-23. [DOI: 10.1016/j.bcp.2009.02.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 02/19/2009] [Accepted: 02/19/2009] [Indexed: 12/21/2022]
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49
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Wang Q, Parrish AR, Wang L. Expanding the genetic code for biological studies. CHEMISTRY & BIOLOGY 2009; 16:323-36. [PMID: 19318213 PMCID: PMC2696486 DOI: 10.1016/j.chembiol.2009.03.001] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 02/25/2009] [Accepted: 03/03/2009] [Indexed: 11/15/2022]
Abstract
Using an orthogonal tRNA-synthetase pair, unnatural amino acids can be genetically encoded with high efficiency and fidelity, and over 40 unnatural amino acids have been site-specifically incorporated into proteins in Escherichia coli, yeast, or mammalian cells. Novel chemical or physical properties embodied in these amino acids enable new means for tailored manipulation of proteins. This review summarizes the methodology and recent progress in expanding this technology to eukaryotic cells. Applications of genetically encoded unnatural amino acids are highlighted with reports on labeling and modifying proteins, probing protein structure and function, identifying and regulating protein activity, and generating proteins with new properties. Genetic incorporation of unnatural amino acids provides a powerful method for investigating a wide variety of biological processes both in vitro and in vivo.
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Affiliation(s)
- Qian Wang
- The Jack H. Skirball Center for Chemical Biology & Proteomics, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Angela R. Parrish
- The Jack H. Skirball Center for Chemical Biology & Proteomics, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Lei Wang
- The Jack H. Skirball Center for Chemical Biology & Proteomics, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
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50
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Abstract
Voltage-clamp techniques are typically used to study the plasma membrane proteins, such as ion channels and transporters that control bioelectrical signals. Many of these proteins have been cloned and can now be studied as potential targets for drug development. The two approaches most commonly used for heterologous expression of cloned ion channels and transporters involve either transfection of the genes into small cells grown in tissue culture or the injection of the genetic material into larger cells. The standard large cells used for the expression of cloned cDNA or synthetic RNA are the egg progenitor cells (oocytes) of the African frog, Xenopus laevis. Until recently, cellular electrophysiology was performed manually by a single operator, one cell at a time. However, methods of high throughput electrophysiology have been developed which are automated and permit data acquisition and analysis from multiple cells in parallel. These methods are breaking a bottleneck in drug discovery, useful in some cases for primary screening as well as for thorough characterization of new drugs. Increasing throughput of high-quality functional data greatly augments the efficiency of academic research and pharmaceutical drug development. Some examples of studies that benefit most from high throughput electrophysiology include pharmaceutical screening of targeted compound libraries, secondary screening of identified compounds for subtype selectivity, screening mutants of ligand-gated channels for changes in receptor function, scanning mutagenesis of protein segments, and mutant-cycle analysis. We describe here the main features and potential applications of OpusXpress, an efficient commercially available system for automated recording from Xenopus oocytes. We show some types of data that have been gathered by this system and review realized and potential applications.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida, USA.
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