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McColman S, Shkalla K, Sidhu P, Liang J, Osman S, Kovacs N, Bokhari Z, Forjaz Marques AC, Li Y, Lin Q, Zhang H, Cramb DT. SARS-CoV-2 virus-like-particles via liposomal reconstitution of spike glycoproteins. NANOSCALE ADVANCES 2023; 5:4167-4181. [PMID: 37560413 PMCID: PMC10408587 DOI: 10.1039/d3na00190c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 07/14/2023] [Indexed: 08/11/2023]
Abstract
The SARS-CoV-2 virus, implicated in the COVID-19 pandemic, recognizes and binds host cells using its spike glycoprotein through an angiotensin converting enzyme 2 (ACE-2) receptor-mediated pathway. Recent research suggests that spatial distributions of the spike protein may influence viral interactions with target cells and immune systems. The goal of this study has been to develop a liposome-based virus-like particle (VLP) by reconstituting the SARS-CoV-2 spike glycoprotein within a synthetic nanoparticle membrane, aiming to eventually establish tunability in spike protein presentation on the nanoparticle surface. Here we report on first steps to this goal, wherein liposomal SARS-CoV-2 VLPs were successfully produced via detergent mediated spike protein reconstitution. The resultant VLPs are shown to successfully co-localize in vitro with the ACE-2 receptor on lung epithelial cell surfaces, followed by internalization into these cells. These VLPs are the first step toward the overall goal of this research which is to form an understanding of the relationship between spike protein surface density and cell-level immune response, eventually toward creating better vaccines and anti-viral therapeutics.
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Affiliation(s)
- Sarah McColman
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Klaidi Shkalla
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Pavleen Sidhu
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Jady Liang
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Department of Physiology, University of Toronto Toronto ON Canada
| | - Selena Osman
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Norbert Kovacs
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Zainab Bokhari
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
| | - Ana Carolina Forjaz Marques
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Faculdade de Ciências Farmacêuticas, Seção Técnica de Graduação, Universidade Estadual Paulista Araraquara SP Brazil
| | - Yuchong Li
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Department of Physiology, University of Toronto Toronto ON Canada
- The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University Guangzhou Guangdong China
| | - Qiwen Lin
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Department of Physiology, University of Toronto Toronto ON Canada
- The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University Guangzhou Guangdong China
| | - Haibo Zhang
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Department of Physiology, University of Toronto Toronto ON Canada
- The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University Guangzhou Guangdong China
- Departments of Anaesthesia and Physiology, Interdepartmental Division of Critical Care Medicine, University of Toronto Toronto ON Canada
| | - David T Cramb
- Department of Chemistry and Biology, Faculty of Science, Toronto Metropolitan University Toronto ON Canada
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Unity Health Toronto Toronto ON Canada
- Department of Chemistry, Faculty of Science, University of Calgary Calgary AB Canada
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2
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Veit S, Paweletz LC, Günther Pomorski T. Determination of membrane protein orientation upon liposomal reconstitution down to the single vesicle level. Biol Chem 2023; 404:647-661. [PMID: 36857289 DOI: 10.1515/hsz-2022-0325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 02/07/2023] [Indexed: 03/02/2023]
Abstract
Reconstitution of membrane proteins into liposomal membranes represents a key technique in enabling functional analysis under well-defined conditions. In this review, we provide a brief introduction to selected methods that have been developed to determine membrane protein orientation after reconstitution in liposomes, including approaches based on proteolytic digestion with proteases, site-specific labeling, fluorescence quenching and activity assays. In addition, we briefly highlight new strategies based on single vesicle analysis to address the problem of sample heterogeneity.
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Affiliation(s)
- Sarina Veit
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
| | - Laura Charlotte Paweletz
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark
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3
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Zhou J, Ren Y, Nie Y, Jin C, Park J, Zhang JXJ. Dual fluorescent hollow silica nanofibers for in situ pH monitoring using an optical fiber. NANOSCALE ADVANCES 2023; 5:2180-2189. [PMID: 37056611 PMCID: PMC10089112 DOI: 10.1039/d2na00943a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 01/15/2023] [Indexed: 06/19/2023]
Abstract
This study reports a sensitive and robust pH sensor based on dual fluorescent doped hollow silica nanofibers (hSNFs) for in situ and real-time pH monitoring. Fluorescein isothiocyanate (FITC) and tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate (Ru(BPY)3) were chosen as a pH sensitive dye and reference dye, respectively. hSNFs were synthesized using a two-step method in a reverse micelle system and were shown to have an average length of 6.20 μm and average diameter of 410 nm. The peak intensity ratio of FITC/Ru(BPY)3 was used to calibrate to solution pH changes. An optical-fiber-based fluorescence detection system was developed that enabled feasible and highly efficient near-field fluorescence detection. The developed system enables fully automated fluorescence detection, where components including the light source, detector, and data acquisition unit are all controlled by a computer. The results show that the developed pH sensor works in a linear range of pH 4.0-9.0 with a fast response time of less than 10 s and minimal sample volume of 50 μL, and can be stored under dark conditions for one month without failure. In addition, the as-prepared hSNF-based pH sensors also have excellent long-term durability. Experimental results from ratiometric sensing confirm the high feasibility, accuracy, stability and simplicity of the dual fluorescent hSNF sensors for the detection of pH in real samples.
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Affiliation(s)
- Junhu Zhou
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
| | - Yundong Ren
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
| | - Yuan Nie
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
| | - Congran Jin
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
| | - Jiyoon Park
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
| | - John X J Zhang
- Thayer School of Engineering, Dartmouth College Hanover 03755 NH USA +1 603 646 9024 +1 603 646 8787
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4
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Biophysical quantification of unitary solute and solvent permeabilities to enable translation to membrane science. J Memb Sci 2022. [DOI: 10.1016/j.memsci.2022.121308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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TAT-RHIM: a more complex issue than expected. Biochem J 2022; 479:259-272. [PMID: 35015082 PMCID: PMC8883498 DOI: 10.1042/bcj20210677] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 11/17/2022]
Abstract
Murine cytomegalovirus protein M45 contains a RIP homotypic interaction motif (RHIM) that is sufficient to confer protection of infected cells against necroptotic cell death. Mechanistically, the N-terminal region of M45 drives rapid self-assembly into homo-oligomeric amyloid fibrils, and interacts with the endogenous RHIM domains of receptor-interacting protein kinases (RIPK) 1, RIPK3, Z-DNA binding protein 1, and TIR domain-containing adaptor-inducing interferon-β. Remarkably, all four mammalian proteins harbouring such a RHIM domain are key components of inflammatory signalling and regulated cell death processes. Immunogenic cell death by regulated necrosis causes extensive tissue damage in a wide range of diseases, including ischemia reperfusion injury, myocardial infarction, sepsis, stroke and organ transplantation. To harness the cell death suppression properties of M45 protein in a therapeutically usable manner, we developed a synthetic peptide encompassing only the RHIM domain of M45. To trigger delivery of RHIM into target cells, we fused the transactivator protein transduction domain of human immunodeficiency virus 1 to the N-terminus of the peptide. The fused peptide could efficiently penetrate eukaryotic cells, but unexpectedly it killed all tested cancer cell lines and primary cells irrespective of species without further stimulus through a necrosis-like cell death. Typical inhibitors of different forms of regulated cell death cannot impede this process, which appears to involve a direct disruption of biomembranes. Nevertheless, our finding has potential clinical relevance; reliable induction of a necrotic form of cell death distinct from all known forms of regulated cell death may offer a novel therapeutic approach to combat resistant tumour cells.
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Islam MS, Gaston JP, Baker MAB. Fluorescence Approaches for Characterizing Ion Channels in Synthetic Bilayers. MEMBRANES 2021; 11:857. [PMID: 34832086 PMCID: PMC8619978 DOI: 10.3390/membranes11110857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 10/25/2021] [Accepted: 10/28/2021] [Indexed: 12/12/2022]
Abstract
Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins into model lipid membranes. Such simpler, in vitro, systems offer the advantage of control over the membrane and protein composition and the lipid environment. Rhodopsin and rhodopsin-like ion channels are widely studied due to their light-interacting properties and are a natural candidate for investigation with fluorescence methods. Here we review techniques for synthesizing liposomes and for reconstituting membrane proteins into lipid bilayers. We then summarize fluorescence assays which can be used to verify the functionality of reconstituted membrane proteins in synthetic liposomes.
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Affiliation(s)
- Md. Sirajul Islam
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
| | - James P. Gaston
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
| | - Matthew A. B. Baker
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
- CSIRO Synthetic Biology Future Science Platform, GPO Box 2583, Brisbane, QLD 4001, Australia
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7
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Current problems and future avenues in proteoliposome research. Biochem Soc Trans 2021; 48:1473-1492. [PMID: 32830854 DOI: 10.1042/bst20190966] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/10/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022]
Abstract
Membrane proteins (MPs) are the gatekeepers between different biological compartments separated by lipid bilayers. Being receptors, channels, transporters, or primary pumps, they fulfill a wide variety of cellular functions and their importance is reflected in the increasing number of drugs that target MPs. Functional studies of MPs within a native cellular context, however, is difficult due to the innate complexity of the densely packed membranes. Over the past decades, detergent-based extraction and purification of MPs and their reconstitution into lipid mimetic systems has been a very powerful tool to simplify the experimental system. In this review, we focus on proteoliposomes that have become an indispensable experimental system for enzymes with a vectorial function, including many of the here described energy transducing MPs. We first address long standing questions on the difficulty of successful reconstitution and controlled orientation of MPs into liposomes. A special emphasis is given on coreconstitution of several MPs into the same bilayer. Second, we discuss recent progress in the development of fluorescent dyes that offer sensitive detection with high temporal resolution. Finally, we briefly cover the use of giant unilamellar vesicles for the investigation of complex enzymatic cascades, a very promising experimental tool considering our increasing knowledge of the interplay of different cellular components.
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Hugentobler KG, Heinrich D, Berg J, Heberle J, Brzezinski P, Schlesinger R, Block S. Lipid Composition Affects the Efficiency in the Functional Reconstitution of the Cytochrome c Oxidase. Int J Mol Sci 2020; 21:ijms21196981. [PMID: 32977390 PMCID: PMC7583929 DOI: 10.3390/ijms21196981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/15/2020] [Accepted: 09/18/2020] [Indexed: 11/16/2022] Open
Abstract
The transmembrane protein cytochrome c oxidase (CcO) is the terminal oxidase in the respiratory chain of many aerobic organisms and catalyzes the reduction of dioxygen to water. This process maintains an electrochemical proton gradient across the membrane hosting the oxidase. CcO is a well-established model enzyme in bioenergetics to study the proton-coupled electron transfer reactions and protonation dynamics involved in these processes. Its catalytic mechanism is subject to ongoing intense research. Previous research, however, was mainly focused on the turnover of oxygen and electrons in CcO, while studies reporting proton turnover rates of CcO, that is the rate of proton uptake by the enzyme, are scarce. Here, we reconstitute CcO from R. sphaeroides into liposomes containing a pH sensitive dye and probe changes of the pH value inside single proteoliposomes using fluorescence microscopy. CcO proton turnover rates are quantified at the single-enzyme level. In addition, we recorded the distribution of the number of functionally reconstituted CcOs across the proteoliposome population. Studies are performed using proteoliposomes made of native lipid sources, such as a crude extract of soybean lipids and the polar lipid extract of E. coli, as well as purified lipid fractions, such as phosphatidylcholine extracted from soybean lipids. It is shown that these lipid compositions have only minor effects on the CcO proton turnover rate, but can have a strong impact on the reconstitution efficiency of functionally active CcOs. In particular, our experiments indicate that efficient functional reconstitution of CcO is strongly promoted by the addition of anionic lipids like phosphatidylglycerol and cardiolipin.
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Affiliation(s)
- Katharina Gloria Hugentobler
- Institute of Chemistry and Biochemistry, Emmy-Noether Group “Bionanointerfaces”, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany;
| | - Dorothea Heinrich
- Department of Physics, Genetic Biophysics, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany; (D.H.); (R.S.)
| | - Johan Berg
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden; (J.B.); (P.B.)
| | - Joachim Heberle
- Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany;
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden; (J.B.); (P.B.)
| | - Ramona Schlesinger
- Department of Physics, Genetic Biophysics, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany; (D.H.); (R.S.)
| | - Stephan Block
- Institute of Chemistry and Biochemistry, Emmy-Noether Group “Bionanointerfaces”, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany;
- Correspondence:
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9
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Dolder N, von Ballmoos C. Bifunctional DNA Duplexes Permit Efficient Incorporation of pH Probes into Liposomes. Chembiochem 2020; 21:2219-2224. [PMID: 32181556 DOI: 10.1002/cbic.202000146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Indexed: 11/10/2022]
Abstract
Enzyme-mediated proton transport across biological membranes is critical for many vital cellular processes. pH-sensitive fluorescent dyes are an indispensable tool for investigating the molecular mechanism of proton-translocating enzymes. Here, we present a novel strategy to entrap pH-sensitive probes in the lumen of liposomes that has several advantages over the use of soluble or lipid-coupled probes. In our approach, the pH sensor is linked to a DNA oligomer with a sequence complementary to a second oligomer modified with a lipophilic moiety that anchors the DNA conjugate to the inner and outer leaflets of the lipid bilayer. The use of DNA as a scaffold allows subsequent selective enzymatic removal of the probe in the outer bilayer leaflet. The method shows a high yield of insertion and is compatible with reconstitution of membrane proteins by different methods. The usefulness of the conjugate for time-resolved proton pumping measurements was demonstrated by using two large membrane protein complexes.
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Affiliation(s)
- Nicolas Dolder
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Christoph von Ballmoos
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
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10
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Sibold J, Tewaag VE, Vagedes T, Mey I, Steinem C. Phase separation in pore-spanning membranes induced by differences in surface adhesion. Phys Chem Chem Phys 2020; 22:9308-9315. [DOI: 10.1039/d0cp00335b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A porous scaffold providing different adhesion energies alters the behaviour of coexisting phases in lipid membranes considerably.
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Affiliation(s)
- Jeremias Sibold
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Vera E. Tewaag
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Thomas Vagedes
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Ingo Mey
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
- Max Planck Institute for Dynamics and Self-Organization
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11
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Kühnel RM, Grifell-Junyent M, Jørgensen IL, Kemmer GC, Schiller J, Palmgren M, Justesen BH, Günther Pomorski T. Short-chain lipid-conjugated pH sensors for imaging of transporter activities in reconstituted systems and living cells. Analyst 2019; 144:3030-3037. [PMID: 30901016 DOI: 10.1039/c8an02161a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The design of ion sensors has gained importance for the study of ion dynamics in cells, with fluorescent proton nanosensors attracting particular interest because of their applicability in monitoring pH gradients in biological microcompartments and reconstituted membrane systems. In this work, we describe the improved synthesis, photophysical properties and applications of pH sensors based on amine-reactive pHrodo esters and short-chain lipid derivatives of phosphoethanolamine. The major features of these novel probes include strong fluorescence under acidic conditions, efficient partitioning into membranes, and extractability by back exchange to albumin. These features allow for the selective labeling of the inner liposomal leaflet in reconstituted membrane systems for studying proton pumping activities in a quantitative fashion, as demonstrated by assaying the activity of a plant plasma membrane H+-ATPase. Furthermore, the short-chain lipid-conjugated pH sensors enable the monitoring of pH changes from neutral to acidic conditions in the endocytic pathway of living cells. Collectively, our results demonstrate the applicability of short-chain lipid-conjugated sensors for in vivo and in vitro studies and thus pave the way for the design of lipid-conjugated sensors selective to other biologically relevant ions, e.g. calcium and sodium.
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Affiliation(s)
- Ronja Marie Kühnel
- Faculty of Chemistry and Biochemistry, Department of Molecular Biochemistry, Ruhr University Bochum, Universitätstrasse 150, D-44780 Bochum, Germany.
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12
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Gerdes B, Rixen RM, Kramer K, Forbrig E, Hildebrandt P, Steinem C. Quantification of Hv1-induced proton translocation by a lipid-coupled Oregon Green 488-based assay. Anal Bioanal Chem 2018; 410:6497-6505. [PMID: 30027319 DOI: 10.1007/s00216-018-1248-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 06/22/2018] [Accepted: 07/05/2018] [Indexed: 10/28/2022]
Abstract
Passive proton translocation across membranes through proton channels is generally measured with assays that allow a qualitative detection of the H+-transfer. However, if a quantitative and time-resolved analysis is required, new methods have to be developed. Here, we report on the quantification of pH changes induced by the voltage-dependent proton channel Hv1 using the commercially available pH-sensitive fluorophore Oregon Green 488-DHPE (OG488-DHPE). We successfully expressed and isolated Hv1 from Escherichia coli and reconstituted the protein in large unilamellar vesicles. Reconstitution was verified by surface enhanced infrared absorption (SEIRA) spectroscopy and proton activity was measured by a standard 9-amino-6-chloro-2-methoxyacridine assay. The quantitative OG488-DHPE assay demonstrated that the proton translocation rate of reconstituted Hv1 is much smaller than those reported in cellular systems. The OG488-DHPE assay further enabled us to quantify the KD-value of the Hv1-inhibitor 2-guanidinobenzimidazole, which matches well with that found in cellular experiments. Our results clearly demonstrate the applicability of the developed in vitro assay to measure proton translocation in a quantitative fashion; the assay allows to screen for new inhibitors and to determine their characteristic parameters. Graphical abstract ᅟ.
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Affiliation(s)
- Benjamin Gerdes
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Rebecca M Rixen
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Kristina Kramer
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Enrico Forbrig
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin, Germany
| | - Claudia Steinem
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany. .,Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 11, 37077, Göttingen, Germany.
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