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Haloi N, Huang S, Nichols AL, Fine EJ, Friesenhahn NJ, Marotta CB, Dougherty DA, Lindahl E, Howard RJ, Mayo SL, Lester HA. Interactive computational and experimental approaches improve the sensitivity of periplasmic binding protein-based nicotine biosensors for measurements in biofluids. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.01.16.524298. [PMID: 36712031 PMCID: PMC9882114 DOI: 10.1101/2023.01.16.524298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
We developed fluorescent protein sensors for nicotine with improved sensitivity. For iNicSnFR12 at pH 7.4, the proportionality constant for Δ F / F 0 vs [nicotine] (δ-slope, 2.7 μM-1) is 6.1-fold higher than the previously reported iNicSnFR3a. The activated state of iNicSnFR12 has a fluorescence quantum yield of at least 0.6. We measured similar dose-response relations for the nicotine-induced absorbance increase and fluorescence increase, suggesting that the absorbance increase leads to the fluorescence increase via the previously described nicotine-induced conformational change, the "candle snuffer" mechanism. Molecular dynamics (MD) simulations identified a binding pose for nicotine, previously indeterminate from experimental data. MD simulations also showed that Helix 4 of the periplasmic binding protein (PBP) domain appears tilted in iNicSnFR12 relative to iNicSnFR3a, likely altering allosteric network(s) that link the ligand binding site to the fluorophore. In thermal melt experiments, nicotine stabilized the PBP of the tested iNicSnFR variants. iNicSnFR12 resolved nicotine in diluted mouse and human serum at 100 nM, the peak [nicotine] that occurs during smoking or vaping, and possibly at the decreasing levels during intervals between sessions. NicSnFR12 was also partially activated by unidentified endogenous ligand(s) in biofluids. Improved iNicSnFR12 variants could become the molecular sensors in continuous nicotine monitors for animal and human biofluids.
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Affiliation(s)
- Nandan Haloi
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, 10044 Stockholm, Sweden
| | - Shan Huang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Aaron L Nichols
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Eve J Fine
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Nicholas J Friesenhahn
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Christopher B Marotta
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Erik Lindahl
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, 10044 Stockholm, Sweden
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - Stephen L Mayo
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena CA 91125 USA
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena CA 91125 USA
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Blumenfeld Z, Bera K, Castrén E, Lester HA. Antidepressants enter cells, organelles, and membranes. Neuropsychopharmacology 2024; 49:246-261. [PMID: 37783840 PMCID: PMC10700606 DOI: 10.1038/s41386-023-01725-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/28/2023] [Accepted: 08/28/2023] [Indexed: 10/04/2023]
Abstract
We begin by summarizing several examples of antidepressants whose therapeutic actions begin when they encounter their targets in the cytoplasm or in the lumen of an organelle. These actions contrast with the prevailing view that most neuropharmacological actions begin when drugs engage their therapeutic targets at extracellular binding sites of plasma membrane targets-ion channels, receptors, and transporters. We review the chemical, pharmacokinetic, and pharmacodynamic principles underlying the movements of drugs into subcellular compartments. We note the relationship between protonation-deprotonation events and membrane permeation of antidepressant drugs. The key properties relate to charge and hydrophobicity/lipid solubility, summarized by the parameters LogP, pKa, and LogDpH7.4. The classical metric, volume of distribution (Vd), is unusually large for some antidepressants and has both supracellular and subcellular components. A table gathers structures, LogP, PKa, LogDpH7.4, and Vd data and/or calculations for most antidepressants and antidepressant candidates. The subcellular components, which can now be measured in some cases, are dominated by membrane binding and by trapping in the lumen of acidic organelles. For common antidepressants, such as selective serotonin reuptake inhibitors (SSRIs) and serotonin/norepinephrine reuptake inhibitors (SNRIs), the target is assumed to be the eponymous reuptake transporter(s), although in fact the compartment of target engagement is unknown. We review special aspects of the pharmacokinetics of ketamine, ketamine metabolites, and other rapidly acting antidepressants (RAADs) including methoxetamine and scopolamine, psychedelics, and neurosteroids. Therefore, the reader can assess properties that markedly affect a drug's ability to enter or cross membranes-and therefore, to interact with target sites that face the cytoplasm, the lumen of organelles, or a membrane. In the current literature, mechanisms involving intracellular targets are termed "location-biased actions" or "inside-out pharmacology". Hopefully, these general terms will eventually acquire additional mechanistic details.
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Affiliation(s)
- Zack Blumenfeld
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Kallol Bera
- Department of Neurosciences and Howard Hughes Medical Institute, University of California at San Diego, La Jolla, CA, USA
| | - Eero Castrén
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA.
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Xi C, Diao J, Moon TS. Advances in ligand-specific biosensing for structurally similar molecules. Cell Syst 2023; 14:1024-1043. [PMID: 38128482 PMCID: PMC10751988 DOI: 10.1016/j.cels.2023.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 08/23/2023] [Accepted: 10/19/2023] [Indexed: 12/23/2023]
Abstract
The specificity of biological systems makes it possible to develop biosensors targeting specific metabolites, toxins, and pollutants in complex medical or environmental samples without interference from structurally similar compounds. For the last two decades, great efforts have been devoted to creating proteins or nucleic acids with novel properties through synthetic biology strategies. Beyond augmenting biocatalytic activity, expanding target substrate scopes, and enhancing enzymes' enantioselectivity and stability, an increasing research area is the enhancement of molecular specificity for genetically encoded biosensors. Here, we summarize recent advances in the development of highly specific biosensor systems and their essential applications. First, we describe the rational design principles required to create libraries containing potential mutants with less promiscuity or better specificity. Next, we review the emerging high-throughput screening techniques to engineer biosensing specificity for the desired target. Finally, we examine the computer-aided evaluation and prediction methods to facilitate the construction of ligand-specific biosensors.
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Affiliation(s)
- Chenggang Xi
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jinjin Diao
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Tae Seok Moon
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, MO, USA.
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Nichols AL, Blumenfeld Z, Luebbert L, Knox HJ, Muthusamy AK, Marvin JS, Kim CH, Grant SN, Walton DP, Cohen BN, Hammar R, Looger L, Artursson P, Dougherty DA, Lester HA. Selective Serotonin Reuptake Inhibitors within Cells: Temporal Resolution in Cytoplasm, Endoplasmic Reticulum, and Membrane. J Neurosci 2023; 43:2222-2241. [PMID: 36868853 PMCID: PMC10072302 DOI: 10.1523/jneurosci.1519-22.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/02/2022] [Accepted: 11/27/2022] [Indexed: 03/05/2023] Open
Abstract
Selective serotonin reuptake inhibitors (SSRIs) are the most prescribed treatment for individuals experiencing major depressive disorder. The therapeutic mechanisms that take place before, during, or after SSRIs bind the serotonin transporter (SERT) are poorly understood, partially because no studies exist on the cellular and subcellular pharmacokinetic properties of SSRIs in living cells. We studied escitalopram and fluoxetine using new intensity-based, drug-sensing fluorescent reporters targeted to the plasma membrane, cytoplasm, or endoplasmic reticulum (ER) of cultured neurons and mammalian cell lines. We also used chemical detection of drug within cells and phospholipid membranes. The drugs attain equilibrium in neuronal cytoplasm and ER at approximately the same concentration as the externally applied solution, with time constants of a few s (escitalopram) or 200-300 s (fluoxetine). Simultaneously, the drugs accumulate within lipid membranes by ≥18-fold (escitalopram) or 180-fold (fluoxetine), and possibly by much larger factors. Both drugs leave cytoplasm, lumen, and membranes just as quickly during washout. We synthesized membrane-impermeant quaternary amine derivatives of the two SSRIs. The quaternary derivatives are substantially excluded from membrane, cytoplasm, and ER for >2.4 h. They inhibit SERT transport-associated currents sixfold or 11-fold less potently than the SSRIs (escitalopram or fluoxetine derivative, respectively), providing useful probes for distinguishing compartmentalized SSRI effects. Although our measurements are orders of magnitude faster than the therapeutic lag of SSRIs, these data suggest that SSRI-SERT interactions within organelles or membranes may play roles during either the therapeutic effects or the antidepressant discontinuation syndrome.SIGNIFICANCE STATEMENT Selective serotonin reuptake inhibitors stabilize mood in several disorders. In general, these drugs bind to SERT, which clears serotonin from CNS and peripheral tissues. SERT ligands are effective and relatively safe; primary care practitioners often prescribe them. However, they have several side effects and require 2-6 weeks of continuous administration until they act effectively. How they work remains perplexing, contrasting with earlier assumptions that the therapeutic mechanism involves SERT inhibition followed by increased extracellular serotonin levels. This study establishes that two SERT ligands, fluoxetine and escitalopram, enter neurons within minutes, while simultaneously accumulating in many membranes. Such knowledge will motivate future research, hopefully revealing where and how SERT ligands engage their therapeutic target(s).
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Affiliation(s)
- Aaron L Nichols
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
| | - Zack Blumenfeld
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
- Keck School of Medicine, University of Southern California, Los Angeles, California 90007
| | - Laura Luebbert
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
- Institute of Biology, Leiden University, 2333 BE Leiden, The Netherlands
| | - Hailey J Knox
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91106
| | - Anand K Muthusamy
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91106
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Viginia 20147
| | - Charlene H Kim
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
| | - Stephen N Grant
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91106
| | - David P Walton
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91106
| | - Bruce N Cohen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
| | - Rebekkah Hammar
- Department of Pharmacy, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Loren Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Viginia 20147
| | - Per Artursson
- Department of Pharmacy, Uppsala University, SE-751 23 Uppsala, Sweden
- Science for Life Laboratory Drug Discovery and Development Platform and Uppsala University Drug Optimization and Pharmaceutical Profiling Platform, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91106
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91106
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Kroning KE, Wang W. Genetically encoded tools for in vivo G-protein-coupled receptor agonist detection at cellular resolution. Clin Transl Med 2022; 12:e1124. [PMID: 36446954 PMCID: PMC9708909 DOI: 10.1002/ctm2.1124] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/10/2022] [Accepted: 11/11/2022] [Indexed: 12/03/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are the most abundant receptor type in the human body and are responsible for regulating many physiological processes, such as sensation, cognition, muscle contraction and metabolism. Further, GPCRs are widely expressed in the brain where their agonists make up a large number of neurotransmitters and neuromodulators. Due to the importance of GPCRs in human physiology, genetically encoded sensors have been engineered to detect GPCR agonists at cellular resolution in vivo. These sensors can be placed into two main categories: those that offer real-time information on the signalling dynamics of GPCR agonists and those that integrate the GPCR agonist signal into a permanent, quantifiable mark that can be used to detect GPCR agonist localisation in a large brain area. In this review, we discuss the various designs of real-time and integration sensors, their advantages and limitations, and some in vivo applications. We also discuss the potential of using real-time and integrator sensors together to identify neuronal circuits affected by endogenous GPCR agonists and perform detailed characterisations of the spatiotemporal dynamics of GPCR agonist release in those circuits. By using these sensors together, the overall knowledge of GPCR-mediated signalling can be expanded.
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Affiliation(s)
- Kayla E. Kroning
- Life Sciences Institute, University of MichiganAnn ArborMichiganUSA
- Department of ChemistryUniversity of MichiganAnn ArborMichiganUSA
| | - Wenjing Wang
- Life Sciences Institute, University of MichiganAnn ArborMichiganUSA
- Department of ChemistryUniversity of MichiganAnn ArborMichiganUSA
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Beatty ZG, Muthusamy AK, Unger EK, Dougherty DA, Tian L, Looger LL, Shivange AV, Bera K, Lester HA, Nichols AL. Fluorescence Screens for Identifying Central Nervous System-Acting Drug-Biosensor Pairs for Subcellular and Supracellular Pharmacokinetics. Bio Protoc 2022; 12:e4551. [PMID: 36532688 PMCID: PMC9724018 DOI: 10.21769/bioprotoc.4551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/17/2022] [Accepted: 09/12/2022] [Indexed: 11/19/2022] Open
Abstract
Subcellular pharmacokinetic measurements have informed the study of central nervous system (CNS)-acting drug mechanisms. Recent investigations have been enhanced by the use of genetically encoded fluorescent biosensors for drugs of interest at the plasma membrane and in organelles. We describe screening and validation protocols for identifying hit pairs comprising a drug and biosensor, with each screen including 13-18 candidate biosensors and 44-84 candidate drugs. After a favorable hit pair is identified and validated via these protocols, the biosensor is then optimized, as described in other papers, for sensitivity and selectivity to the drug. We also show sample hit pair data that may lead to future intensity-based drug-sensing fluorescent reporters (iDrugSnFRs). These protocols will assist scientists to use fluorescence responses as criteria in identifying favorable fluorescent biosensor variants for CNS-acting drugs that presently have no corresponding biosensor partner. This protocol was validated in: eLife (2022), DOI: 10.7554/eLife.74648 Graphical abstract.
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Affiliation(s)
- Zoe G. Beatty
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA
| | - Anand K. Muthusamy
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, USA
| | - Elizabeth K. Unger
- Department of Biochemistry and Molecular Medicine and the Center for Neuroscience, University of California at Davis, Davis, USA
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, USA
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine and the Center for Neuroscience, University of California at Davis, Davis, USA
| | | | - Amol V. Shivange
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA
| | - Kallol Bera
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA
| | - Henry A. Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA
| | - Aaron L. Nichols
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, USA
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