1
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Lauritsen L, Szomek M, Hornum M, Reinholdt P, Kongsted J, Nielsen P, Brewer JR, Wüstner D. Ratiometric fluorescence nanoscopy and lifetime imaging of novel Nile Red analogs for analysis of membrane packing in living cells. Sci Rep 2024; 14:13748. [PMID: 38877068 PMCID: PMC11178856 DOI: 10.1038/s41598-024-64180-8] [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: 12/18/2023] [Accepted: 06/05/2024] [Indexed: 06/16/2024] Open
Abstract
Subcellular membranes have complex lipid and protein compositions, which give rise to organelle-specific membrane packing, fluidity, and permeability. Due to its exquisite solvent sensitivity, the lipophilic fluorescence dye Nile Red has been used extensively to study membrane packing and polarity. Further improvement of Nile Red can be achieved by introducing electron-donating or withdrawing functional groups. Here, we compare the potential of derivatives of Nile Red with such functional substitutions for super-resolution fluorescence microscopy of lipid packing in model membranes and living cells. All studied Nile Red derivatives exhibit cholesterol-dependent fluorescence changes in model membranes, as shown by spectrally resolved stimulated emission depletion (STED) microscopy. STED imaging of Nile Red probes in cells reveals lower membrane packing in fibroblasts from healthy subjects compared to those from patients suffering from Niemann Pick type C1 (NPC1) disease, a lysosomal storage disorder with accumulation of cholesterol and sphingolipids in late endosomes and lysosomes. We also find small but consistent changes in the fluorescence lifetime of the Nile Red derivatives in NPC1 cells, suggesting altered hydrogen-bonding capacity in their membranes. All Nile Red derivatives are essentially non-fluorescent in water but increase their brightness in membranes, allowing for their use in MINFLUX single molecule tracking experiments. Our study uncovers the potential of Nile Red probes with functional substitutions for nanoscopic membrane imaging.
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Affiliation(s)
- Line Lauritsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Mick Hornum
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Poul Nielsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Jonathan R Brewer
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
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2
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Szomek M, Akkerman V, Lauritsen L, Walther HL, Juhl AD, Thaysen K, Egebjerg JM, Covey DF, Lehmann M, Wessig P, Foster AJ, Poolman B, Werner S, Schneider G, Müller P, Wüstner D. Ergosterol promotes aggregation of natamycin in the yeast plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184350. [PMID: 38806103 DOI: 10.1016/j.bbamem.2024.184350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 05/11/2024] [Accepted: 05/24/2024] [Indexed: 05/30/2024]
Abstract
Polyene macrolides are antifungal substances, which interact with cells in a sterol-dependent manner. While being widely used, their mode of action is poorly understood. Here, we employ ultraviolet-sensitive (UV) microscopy to show that the antifungal polyene natamycin binds to the yeast plasma membrane (PM) and causes permeation of propidium iodide into cells. Right before membrane permeability became compromised, we observed clustering of natamycin in the PM that was independent of PM protein domains. Aggregation of natamycin was paralleled by cell deformation and membrane blebbing as revealed by soft X-ray microscopy. Substituting ergosterol for cholesterol decreased natamycin binding and caused a reduced clustering of natamycin in the PM. Blocking of ergosterol synthesis necessitates sterol import via the ABC transporters Aus1/Pdr11 to ensure natamycin binding. Quantitative imaging of dehydroergosterol (DHE) and cholestatrienol (CTL), two analogues of ergosterol and cholesterol, respectively, revealed a largely homogeneous lateral sterol distribution in the PM, ruling out that natamycin binds to pre-assembled sterol domains. Depletion of sphingolipids using myriocin increased natamycin binding to yeast cells, likely by increasing the ergosterol fraction in the outer PM leaflet. Importantly, binding and membrane aggregation of natamycin was paralleled by a decrease of the dipole potential in the PM, and this effect was enhanced in the presence of myriocin. We conclude that ergosterol promotes binding and aggregation of natamycin in the yeast PM, which can be synergistically enhanced by inhibitors of sphingolipid synthesis.
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Affiliation(s)
- Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Vibeke Akkerman
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Line Lauritsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Hanna-Loisa Walther
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Alice Dupont Juhl
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Katja Thaysen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Jacob Marcus Egebjerg
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Douglas F Covey
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA; Taylor Family Institute for Innovative Psychiatric Research, USA
| | - Max Lehmann
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany
| | - Pablo Wessig
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany
| | - Alexander J Foster
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 Groningen, the Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 Groningen, the Netherlands
| | - Stephan Werner
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - Gerd Schneider
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - Peter Müller
- Department of Biology, Humboldt University Berlin, Invalidenstr. 43, D-10115 Berlin, Germany
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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3
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Akkerman V, Scheidt HA, Reinholdt P, Bashawat M, Szomek M, Lehmann M, Wessig P, Covey DF, Kongsted J, Müller P, Wüstner D. Natamycin interferes with ergosterol-dependent lipid phases in model membranes. BBA ADVANCES 2023; 4:100102. [PMID: 37691996 PMCID: PMC10482743 DOI: 10.1016/j.bbadva.2023.100102] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023] Open
Abstract
Natamycin is an antifungal polyene macrolide that is used as a food preservative but also to treat fungal keratitis and other yeast infections. In contrast to other polyene antimycotics, natamycin does not form ion pores in the plasma membrane, but its mode of action is poorly understood. Using nuclear magnetic resonance (NMR) spectroscopy of deuterated sterols, we find that natamycin slows the mobility of ergosterol and cholesterol in liquid-ordered (Lo) membranes to a similar extent. This is supported by molecular dynamics (MD) simulations, which additionally reveal a strong impact of natamycin dimers on sterol dynamics and water permeability. Interference with sterol-dependent lipid packing is also reflected in a natamycin-mediated increase in membrane accessibility for dithionite, particularly in bilayers containing ergosterol. NMR experiments with deuterated sphingomyelin (SM) in sterol-containing membranes reveal that natamycin reduces phase separation and increases lipid exchange in bilayers with ergosterol. In ternary lipid mixtures containing monounsaturated phosphatidylcholine, saturated SM, and either ergosterol or cholesterol, natamycin interferes with phase separation into Lo and liquid-disordered (Ld) domains, as shown by NMR spectroscopy. Employing the intrinsic fluorescence of natamycin in ultraviolet-sensitive microscopy, we can visualize the binding of natamycin to giant unilamellar vesicles (GUVs) and find that it has the highest affinity for the Lo phase in GUVs containing ergosterol. Our results suggest that natamycin specifically interacts with the sterol-induced ordered phase, in which it disrupts lipid packing and increases solvent accessibility. This property is particularly pronounced in ergosterol containing membranes, which could underlie the selective antifungal activity of natamycin.
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Affiliation(s)
- Vibeke Akkerman
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Holger A. Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107, Leipzig, Germany
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Mohammad Bashawat
- Department of Biology, Humboldt University Berlin, Invalidenstr. 43, D-10115, Berlin, Germany
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Max Lehmann
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam, Germany
| | - Pablo Wessig
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam, Germany
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University, St. Louis, MO, 63110, USA
- Taylor Family Institute for Innovative Psychiatric Research, St. Louis, Missouri, USA
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Peter Müller
- Department of Biology, Humboldt University Berlin, Invalidenstr. 43, D-10115, Berlin, Germany
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
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4
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Juhl AD, Lund FW, Jensen MLV, Szomek M, Heegaard CW, Guttmann P, Werner S, McNally J, Schneider G, Kapishnikov S, Wüstner D. Niemann Pick C2 protein enables cholesterol transfer from endo-lysosomes to the plasma membrane for efflux by shedding of extracellular vesicles. Chem Phys Lipids 2021; 235:105047. [PMID: 33422548 DOI: 10.1016/j.chemphyslip.2020.105047] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/28/2020] [Indexed: 10/22/2022]
Abstract
The Niemann-Pick C2 protein (NPC2) is a sterol transfer protein in the lumen of late endosomes and lysosomes (LE/LYSs). Absence of functional NPC2 leads to endo-lysosomal buildup of cholesterol and other lipids. How NPC2's known capacity to transport cholesterol between model membranes is linked to its function in living cells is not known. Using quantitative live-cell imaging combined with modeling of the efflux kinetics, we show that NPC2-deficient human fibroblasts can export the cholesterol analog dehydroergosterol (DHE) from LE/LYSs. Internalized NPC2 accelerated sterol efflux extensively, accompanied by reallocation of LE/LYSs containing fluorescent NPC2 and DHE to the cell periphery. Using quantitative fluorescence loss in photobleaching of TopFluor-cholesterol (TF-Chol), we estimate a residence time for a rapidly exchanging sterol pool in LE/LYSs localized in close proximity to the plasma membrane (PM), of less than one min and observed non-vesicular sterol exchange between LE/LYSs and the PM. Excess sterol was released from the PM by shedding of cholesterol-rich vesicles. The ultrastructure of such vesicles was analyzed by combined fluorescence and cryo soft X-ray tomography (SXT), revealing that they can contain lysosomal cargo and intraluminal vesicles. Treating cells with apoprotein A1 and with nuclear receptor liver X-receptor (LXR) agonists to upregulate expression of ABC transporters enhanced cholesterol efflux from the PM, at least partly by accelerating vesicle release. We conclude that NPC2 inside LE/LYSs facilitates non-vesicular sterol exchange with the PM for subsequent sterol efflux to acceptor proteins and for shedding of sterol-rich vesicles from the cell surface.
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Affiliation(s)
- Alice Dupont Juhl
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Frederik W Lund
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Maria Louise V Jensen
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, University of Aarhus, DK-8000, Aarhus C, Denmark
| | - Peter Guttmann
- Department X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Stephan Werner
- Department X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - James McNally
- Department X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Gerd Schneider
- Department X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Sergey Kapishnikov
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230, Odense M, Denmark.
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5
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Abstract
During the capturing of the time-lapse sequence of fluorescently labeled samples, fluorescence intensity exhibits decays. This phenomenon is known as 'photobleaching' and is a widely known problem in imaging in life sciences. The photobleaching can be attenuated by tuning the imaging set-up, but when such adjustments only partially work, the image sequence can be corrected for the loss of intensity in order to precisely segment the target structure or to quantify true intensity dynamics. We implemented an ImageJ plugin that allows the user to compensate for the photobleaching to estimate the non-bleaching condition with choice of three different algorithms: simple ratio, exponential fitting, and histogram matching methods. The histogram matching method is a novel algorithm for photobleaching correction. This article presents details and characteristics of each algorithm based on application to actual image sequences.
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Affiliation(s)
- Kota Miura
- Nikon Imaging Center, University of Heidelberg, Heidelberg, 69120, Germany.,Centre for Molecular and Cellular Imaging, EMBL, Heidelberg, 69117, Germany
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6
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Winkler MBL, Kidmose RT, Szomek M, Thaysen K, Rawson S, Muench SP, Wüstner D, Pedersen BP. Structural Insight into Eukaryotic Sterol Transport through Niemann-Pick Type C Proteins. Cell 2019; 179:485-497.e18. [PMID: 31543266 DOI: 10.1016/j.cell.2019.08.038] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/05/2019] [Accepted: 08/21/2019] [Indexed: 12/24/2022]
Abstract
Niemann-Pick type C (NPC) proteins are essential for sterol homeostasis, believed to drive sterol integration into the lysosomal membrane before redistribution to other cellular membranes. Here, using a combination of crystallography, cryo-electron microscopy, and biochemical and in vivo studies on the Saccharomyces cerevisiae NPC system (NCR1 and NPC2), we present a framework for sterol membrane integration. Sterols are transferred between hydrophobic pockets of vacuolar NPC2 and membrane-protein NCR1. NCR1 has its N-terminal domain (NTD) positioned to deliver a sterol to a tunnel connecting NTD to the luminal membrane leaflet 50 Å away. A sterol is caught inside this tunnel during transport, and a proton-relay network of charged residues in the transmembrane region is linked to this tunnel supporting a proton-driven transport mechanism. We propose a model for sterol integration that clarifies the role of NPC proteins in this essential eukaryotic pathway and that rationalizes mutations in patients with Niemann-Pick disease type C.
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Affiliation(s)
- Mikael B L Winkler
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, Aarhus C 8000, Denmark
| | - Rune T Kidmose
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, Aarhus C 8000, Denmark
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M 5230, Denmark
| | - Katja Thaysen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M 5230, Denmark
| | - Shaun Rawson
- School of Biomedical Sciences and The Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Stephen P Muench
- School of Biomedical Sciences and The Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M 5230, Denmark
| | - Bjørn Panyella Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, Aarhus C 8000, Denmark; Aarhus Institute of Advanced Studies, Aarhus University, Høegh-Guldbergs Gade 6B, Aarhus C 8000, Denmark.
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7
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Berzina Z, Solanko LM, Mehadi AS, Jensen MLV, Lund FW, Modzel M, Szomek M, Solanko KA, Dupont A, Nielsen GK, Heegaard CW, Ejsing CS, Wüstner D. Niemann-Pick C2 protein regulates sterol transport between plasma membrane and late endosomes in human fibroblasts. Chem Phys Lipids 2018; 213:48-61. [PMID: 29580834 DOI: 10.1016/j.chemphyslip.2018.03.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 03/13/2018] [Accepted: 03/15/2018] [Indexed: 11/28/2022]
Abstract
Niemann-Pick disease type C2 is a lipid storage disorder in which mutations in the NPC2 protein cause accumulation of lipoprotein-derived cholesterol in late endosomes and lysosomes (LE/LYSs). Whether cholesterol delivered by other means to NPC2 deficient cells also accumulates in LE/LYSs is currently unknown. We show that the close cholesterol analog dehydroergosterol (DHE), when delivered to the plasma membrane (PM) accumulates in LE/LYSs of human fibroblasts lacking functional NPC2. We measured two different time scales of sterol diffusion; while DHE rich LE/LYSs moved by slow anomalous diffusion in disease cells (D ∼ 4.6∙10-4 μm2/sec; α∼0.76), a small pool of sterol could exchange rapidly with D ∼ 3 μm2/s between LE/LYSs, as shown by fluorescence recovery after photobleaching (FRAP). By quantitative lipid mass spectrometry we found that esterification of 13C-labeled cholesterol but not of DHE is reduced 10-fold in disease fibroblasts compared to control cells. Internalized NPC2 rescued the sterol storage phenotype and strongly expanded the dynamic sterol pool seen in FRAP experiments. Together, our study shows that cholesterol esterification and trafficking of sterols between the PM and LE/LYSs depends on a functional NPC2 protein. NPC2 likely acts inside LE/LYSs from where it increases non-vesicular sterol exchange with other organelles.
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Affiliation(s)
- Zane Berzina
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark; Orphazyme ApS, Ole Maales Vej 3, 2200 Copenhagen N, Denmark
| | - Ahmed S Mehadi
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Maria Louise V Jensen
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Frederik W Lund
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Maciej Modzel
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Katarzyna A Solanko
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Alice Dupont
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Gitte Krogh Nielsen
- Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark
| | - Christer S Ejsing
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, DK-5230 Odense M, Denmark.
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8
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Modzel M, Lund FW, Wüstner D. Synthesis and Live-Cell Imaging of Fluorescent Sterols for Analysis of Intracellular Cholesterol Transport. Methods Mol Biol 2017; 1583:111-140. [PMID: 28205171 DOI: 10.1007/978-1-4939-6875-6_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Cellular cholesterol homeostasis relies on precise control of the sterol content of organelle membranes. Obtaining insight into cholesterol trafficking pathways and kinetics by live-cell imaging relies on two conditions. First, one needs to develop suitable analogs that resemble cholesterol as closely as possible with respect to their biophysical and biochemical properties. Second, the cholesterol analogs should have good fluorescence properties. This interferes, however, often with the first requirement, such that the imaging instrumentation must be optimized to collect photons from suboptimal fluorophores, but good cholesterol mimics, such as the intrinsically fluorescent sterols, cholestatrienol (CTL) or dehydroergosterol (DHE). CTL differs from cholesterol only in having two additional double bonds in the ring system, which is why it is slightly fluorescent in the ultraviolet (UV). In the first part of this protocol, we describe how to synthesize and image CTL in living cells relative to caveolin, a structural component of caveolae. In the second part, we explain in detail how to perform time-lapse experiments of commercially available BODIPY-tagged cholesterol (TopFluor-cholesterol®; TF-Chol) in comparison to DHE. Finally, using two-photon time-lapse imaging data of TF-Chol, we demonstrate how to use our imaging toolbox SpatTrack for tracking sterol rich vesicles in living cells over time.
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Affiliation(s)
- Maciej Modzel
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, 5230, Denmark
| | - Frederik W Lund
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, 5230, Denmark.,Department of Biochemistry, Weill Medical College of Cornell University, New York, NY, 10065, USA
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, 5230, Denmark.
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9
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Imaging approaches for analysis of cholesterol distribution and dynamics in the plasma membrane. Chem Phys Lipids 2016; 199:106-135. [PMID: 27016337 DOI: 10.1016/j.chemphyslip.2016.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 03/04/2016] [Indexed: 11/21/2022]
Abstract
Cholesterol is an important lipid component of the plasma membrane (PM) of mammalian cells, where it is involved in control of many physiological processes, such as endocytosis, cell migration, cell signalling and surface ruffling. In an attempt to explain these functions of cholesterol, several models have been put forward about cholesterol's lateral and transbilayer organization in the PM. In this article, we review imaging techniques developed over the last two decades for assessing the distribution and dynamics of cholesterol in the PM of mammalian cells. Particular focus is on fluorescence techniques to study the lateral and inter-leaflet distribution of suitable cholesterol analogues in the PM of living cells. We describe also several methods for determining lateral cholesterol dynamics in the PM including fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), single particle tracking (SPT) and spot variation FCS coupled to stimulated emission depletion (STED) microscopy. For proper interpretation of such measurements, we provide some background in probe photophysics and diffusion phenomena occurring in cell membranes. In particular, we show the equivalence of the reaction-diffusion approach, as used in FRAP and FCS, and continuous time random walk (CTRW) models, as often invoked in SPT studies. We also discuss mass spectrometry (MS) based imaging of cholesterol in the PM of fixed cells and compare this method with fluorescence imaging of sterols. We conclude that evidence from many experimental techniques converges towards a model of a homogeneous distribution of cholesterol with largely free and unhindered diffusion in both leaflets of the PM.
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10
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Wüstner D, Lund FW, Röhrl C, Stangl H. Potential of BODIPY-cholesterol for analysis of cholesterol transport and diffusion in living cells. Chem Phys Lipids 2016; 194:12-28. [DOI: 10.1016/j.chemphyslip.2015.08.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 08/07/2015] [Accepted: 08/12/2015] [Indexed: 01/04/2023]
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11
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LUND F, WÜSTNER D. A comparison of single particle tracking and temporal image correlation spectroscopy for quantitative analysis of endosome motility. J Microsc 2013; 252:169-88. [DOI: 10.1111/jmi.12080] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 02/08/2013] [Indexed: 11/27/2022]
Affiliation(s)
- F.W. LUND
- Department of Biochemistry and Molecular Biology, University of Southern Denmark; DK-5230 Odense M Denmark
| | - D. WÜSTNER
- Department of Biochemistry and Molecular Biology, University of Southern Denmark; DK-5230 Odense M Denmark
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12
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Abstract
Cholesterol plays an important role in determining the biophysical properties of biological membranes, and its concentration is tightly controlled by homeostatic processes. The intracellular transport of cholesterol among organelles is a key part of the homeostatic mechanism, but sterol transport processes are not well understood. Fluorescence microscopy is a valuable tool for studying intracellular transport processes, but this method can be challenging for lipid molecules because addition of a fluorophore may alter the properties of the molecule greatly. We discuss the use of fluorescent molecules that can bind to cholesterol to reveal its distribution in cells. We also discuss the use of intrinsically fluorescent sterols that closely mimic cholesterol, as well as some minimally modified fluorophore-labeled sterols. Methods for imaging these sterols by conventional fluorescence microscopy and by multiphoton microscopy are described. Some label-free methods for imaging cholesterol itself are also discussed briefly.
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13
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Wüstner D, Sage D. Multicolor bleach-rate imaging enlightens in vivo sterol transport. Commun Integr Biol 2011; 3:370-3. [PMID: 20798830 DOI: 10.4161/cib.3.4.11972] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 03/29/2010] [Indexed: 12/30/2022] Open
Abstract
Elucidation of in vivo cholesterol transport and its aberrations in cardiovascular diseases requires suitable model organisms and the development of appropriate monitoring technology. We recently presented a new approach to visualize transport of the intrinsically fluorescent sterol, dehydroergosterol (DHE) in the genetically tractable model organism Caenorhabditis elegans (C. elegans). DHE is structurally very similar to cholesterol and ergosterol, two sterols used by the sterol-auxotroph nematode. We developed a new computational method measuring fluorophore bleaching kinetics at every pixel position, which can be used as a fingerprint to distinguish rapidly bleaching DHE from slowly bleaching autofluorescence in the animals. Here, we introduce multicolor bleach-rate sterol imaging. By this method, we demonstrate that some DHE is targeted to a population of basolateral recycling endosomes (RE) labelled with GFP-tagged RME-1 (GFP-RME-1) in the intestine of both, wild-type nematodes and mutant animals lacking intestinal gut granules (glo1-mutants). DHE-enriched intestinal organelles of glo1-mutants were decorated with GFPrme8, a marker for early endosomes. No co-localization was found with a lysosomal marker, GFP-LMP1. Our new methods hold great promise for further studies on endosomal sterol transport in C. elegans.
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Wüstner D, Brewer JR, Bagatolli L, Sage D. Potential of ultraviolet wide-field imaging and multiphoton microscopy for analysis of dehydroergosterol in cellular membranes. Microsc Res Tech 2011; 74:92-108. [PMID: 21181715 DOI: 10.1002/jemt.20878] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Dehydroergosterol (DHE) is an intrinsically fluorescent sterol with absorption/emission in the ultraviolet (UV) region and biophysical properties similar to those of cholesterol. We compared the potential of UV-sensitive low-light-level wide-field (UV-WF) imaging with that of multiphoton (MP) excitation microscopy to monitor DHE in living cells. Significantly reduced photobleaching in MP microscopy of DHE enabled us to acquire three-dimensional z-stacks of DHE-stained cells and to obtain high-resolution maps of DHE in surface ruffles, nanotubes, and the apical membrane of epithelial cells. We found that the lateral resolution of MP microscopy is ∼1.5-fold higher than that of UV-WF deconvolution microscopy, allowing for improved spatiotemporal analysis of plasma membrane sterol distribution. Surface intensity patterns of DHE with a diameter of 0.2 μm persisting over several minutes could be resolved by MP time-lapse microscopy. Diffusion coefficients of 0.25-μm-diameter endocytic vesicles containing DHE were determined by MP spatiotemporal image correlation spectroscopy. The requirement of extremely high laser power for visualization of DHE by MP microscopy made this method less potent for multicolor applications with organelle markers like green fluorescent protein-tagged proteins. The signal-to-noise ratio obtainable by UV-WF imaging could be significantly improved by pixelwise bleach rate fitting and calculation of an amplitude image from the decay model and by frame averaging after pixelwise bleaching correction of the image stacks. We conclude that UV-WF imaging and MP microscopy of DHE provide complementary information regarding membrane distribution and intracellular targeting of sterols.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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Quantitative assessment of sterol traffic in living cells by dual labeling with dehydroergosterol and BODIPY-cholesterol. Chem Phys Lipids 2011; 164:221-35. [DOI: 10.1016/j.chemphyslip.2011.01.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 01/14/2011] [Accepted: 01/24/2011] [Indexed: 11/18/2022]
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Wüstner D, Landt Larsen A, Faergeman NJ, Brewer JR, Sage D. Selective Visualization of Fluorescent Sterols in Caenorhabditis elegans by Bleach-Rate-Based Image Segmentation. Traffic 2010; 11:440-54. [DOI: 10.1111/j.1600-0854.2010.01040.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Weinigel M, Kellner AL, Price JH. Exploration of chromatic aberration for multiplanar imaging: proof of concept with implications for fast, efficient autofocus. Cytometry A 2009; 75:999-1006. [PMID: 19760744 DOI: 10.1002/cyto.a.20788] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Image-based autofocus determines focus directly from the specimen (as opposed to reflective surface positioning with an offset), but sequential acquisition of a stack of images to measure resolution/sharpness and find best focus is slower than reflective positioning. Simultaneous imaging of multiple focal planes, which is also useful for 3D imaging of live cells, is faster but requires complicated optics. With color CCD cameras and white light sources commonly available, we asked if axial chromatic aberration can be utilized to acquire multiple focal planes simultaneously, and if it can be controlled through a range sufficient for practical use. For proof of concept, we theoretically and experimentally explored the focal differences between three narrow wavelength bands on a 3-chip color CCD camera with and without glass inserts of various thicknesses and dispersions. Ray tracing yielded changes in foci of 0.65-0.9 microm upon insertion of 12.5-mm thick glass samples for green (G, 522 nm) vs. blue (B, 462 nm) and green vs. red (G-R, 604 nm). On a microscope: (1) With no glass inserts, the differences in foci were 2.15 microm (G-B) and 0.43 microm (G-R); (2) With glass inserts, the maximum change in foci for G vs. B was 0.44 microm and for G vs. R was 0.26 microm; and (3) An 11.3 mm thick N-BK7 glass insert shifted the foci 0.9 microm (R), 0.6 microm (G), and 0.35 microm (B), such that the B and R foci were farther apart (2.1 microm vs. 1.7 microm) and the R and G foci were closer together (0.25 microm vs. 0.45 microm). The slopes of the differences in foci were dependent on thickness, index of refraction, and dispersion. The measured differences in foci are comparable to the axial steps of 0.1-0.24 microm commonly used for autofocus, and focal plane separation can be altered by inserting optical elements of various dispersions and thicknesses. By enabling acquisition of multiple, axially offset images simultaneously, chromatic aberration, normally an imaging pariah, creates a possible mechanism for efficient multiplanar imaging of multiple spectral bands from white light illumination.
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Affiliation(s)
- Martin Weinigel
- Signal Transduction Program, Cancer Center, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
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Garvik O, Benediktson P, Simonsen AC, Ipsen JH, Wüstner D. The fluorescent cholesterol analog dehydroergosterol induces liquid-ordered domains in model membranes. Chem Phys Lipids 2009; 159:114-8. [DOI: 10.1016/j.chemphyslip.2009.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Revised: 03/13/2009] [Accepted: 03/19/2009] [Indexed: 01/01/2023]
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Spatiotemporal analysis of endocytosis and membrane distribution of fluorescent sterols in living cells. Histochem Cell Biol 2008; 130:891-908. [DOI: 10.1007/s00418-008-0488-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/30/2008] [Indexed: 01/04/2023]
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