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Guo A, Wu Q, Yan X, Chen K, Liu Y, Liang D, Yang Y, Luo Q, Xiong M, Yu Y, Fei E, Chen F. Differential roles of lysosomal cholesterol transporters in the development of C. elegans NMJs. Life Sci Alliance 2024; 7:e202402584. [PMID: 39084875 PMCID: PMC11291935 DOI: 10.26508/lsa.202402584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 07/21/2024] [Accepted: 07/22/2024] [Indexed: 08/02/2024] Open
Abstract
Cholesterol homeostasis in neurons is critical for synapse formation and maintenance. Neurons with impaired cholesterol uptake undergo progressive synapse loss and eventual degeneration. To investigate the molecular mechanisms of neuronal cholesterol homeostasis and its role during synapse development, we studied motor neurons of Caenorhabditis elegans because these neurons rely on dietary cholesterol. Combining lipidomic analysis, we discovered that NCR-1, a lysosomal cholesterol transporter, promotes cholesterol absorption and synapse development. Loss of ncr-1 causes smaller synapses, and low cholesterol exacerbates the deficits. Moreover, NCR-1 deficiency hinders the increase in synapses under high cholesterol. Unexpectedly, NCR-2, the NCR-1 homolog, increases the use of cholesterol and sphingomyelins and impedes synapse formation. NCR-2 deficiency causes an increase in synapses regardless of cholesterol concentration. Inhibiting the degradation or synthesis of sphingomyelins can induce or suppress the synaptic phenotypes in ncr-2 mutants. Our findings indicate that neuronal cholesterol homeostasis is differentially controlled by two lysosomal cholesterol transporters and highlight the importance of neuronal cholesterol homeostasis in synapse development.
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Affiliation(s)
- Amin Guo
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Qi Wu
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Xin Yan
- https://ror.org/042v6xz23 School of Life Sciences, Nanchang University, Nanchang, China
| | - Kanghua Chen
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Yuxiang Liu
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Dingfa Liang
- https://ror.org/042v6xz23 Queen Mary School of Nanchang University, Jiangxi Medical College, Nanchang, China
| | - Yuxiao Yang
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Qunfeng Luo
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Mingtao Xiong
- https://ror.org/042v6xz23 Institute of Biomedical Innovation, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Yong Yu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, China
| | - Erkang Fei
- https://ror.org/042v6xz23 Institute of Biomedical Innovation, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Fei Chen
- https://ror.org/042v6xz23 School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China
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2
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Wüstner D, Egebjerg JM, Lauritsen L. Dynamic Mode Decomposition of Multiphoton and Stimulated Emission Depletion Microscopy Data for Analysis of Fluorescent Probes in Cellular Membranes. SENSORS (BASEL, SWITZERLAND) 2024; 24:2096. [PMID: 38610307 PMCID: PMC11013970 DOI: 10.3390/s24072096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/14/2024] [Accepted: 03/21/2024] [Indexed: 04/14/2024]
Abstract
An analysis of the membrane organization and intracellular trafficking of lipids often relies on multiphoton (MP) and super-resolution microscopy of fluorescent lipid probes. A disadvantage of particularly intrinsically fluorescent lipid probes, such as the cholesterol and ergosterol analogue, dehydroergosterol (DHE), is their low MP absorption cross-section, resulting in a low signal-to-noise ratio (SNR) in live-cell imaging. Stimulated emission depletion (STED) microscopy of membrane probes like Nile Red enables one to resolve membrane features beyond the diffraction limit but exposes the sample to a lot of excitation light and suffers from a low SNR and photobleaching. Here, dynamic mode decomposition (DMD) and its variant, higher-order DMD (HoDMD), are applied to efficiently reconstruct and denoise the MP and STED microscopy data of lipid probes, allowing for an improved visualization of the membranes in cells. HoDMD also allows us to decompose and reconstruct two-photon polarimetry images of TopFluor-cholesterol in model and cellular membranes. Finally, DMD is shown to not only reconstruct and denoise 3D-STED image stacks of Nile Red-labeled cells but also to predict unseen image frames, thereby allowing for interpolation images along the optical axis. This important feature of DMD can be used to reduce the number of image acquisitions, thereby minimizing the light exposure of biological samples without compromising image quality. Thus, DMD as a computational tool enables gentler live-cell imaging of fluorescent probes in cellular membranes by MP and STED microscopy.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark; (J.M.E.); (L.L.)
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3
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Pfrieger FW. The Niemann-Pick type diseases – A synopsis of inborn errors in sphingolipid and cholesterol metabolism. Prog Lipid Res 2023; 90:101225. [PMID: 37003582 DOI: 10.1016/j.plipres.2023.101225] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/27/2023] [Accepted: 03/27/2023] [Indexed: 04/03/2023]
Abstract
Disturbances of lipid homeostasis in cells provoke human diseases. The elucidation of the underlying mechanisms and the development of efficient therapies represent formidable challenges for biomedical research. Exemplary cases are two rare, autosomal recessive, and ultimately fatal lysosomal diseases historically named "Niemann-Pick" honoring the physicians, whose pioneering observations led to their discovery. Acid sphingomyelinase deficiency (ASMD) and Niemann-Pick type C disease (NPCD) are caused by specific variants of the sphingomyelin phosphodiesterase 1 (SMPD1) and NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2) genes that perturb homeostasis of two key membrane components, sphingomyelin and cholesterol, respectively. Patients with severe forms of these diseases present visceral and neurologic symptoms and succumb to premature death. This synopsis traces the tortuous discovery of the Niemann-Pick diseases, highlights important advances with respect to genetic culprits and cellular mechanisms, and exposes efforts to improve diagnosis and to explore new therapeutic approaches.
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4
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Wüstner D. Image segmentation and separation of spectrally similar dyes in fluorescence microscopy by dynamic mode decomposition of photobleaching kinetics. BMC Bioinformatics 2022; 23:334. [PMID: 35962314 PMCID: PMC9373304 DOI: 10.1186/s12859-022-04881-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 08/03/2022] [Indexed: 12/03/2022] Open
Abstract
Background Image segmentation in fluorescence microscopy is often based on spectral separation of fluorescent probes (color-based segmentation) or on significant intensity differences in individual image regions (intensity-based segmentation). These approaches fail, if dye fluorescence shows large spectral overlap with other employed probes or with strong cellular autofluorescence. Results Here, a novel model-free approach is presented which determines bleaching characteristics based on dynamic mode decomposition (DMD) and uses the inferred photobleaching kinetics to distinguish different probes or dye molecules from autofluorescence. DMD is a data-driven computational method for detecting and quantifying dynamic events in complex spatiotemporal data. Here, DMD is first used on synthetic image data and thereafter used to determine photobleaching characteristics of a fluorescent sterol probe, dehydroergosterol (DHE), compared to that of cellular autofluorescence in the nematode Caenorhabditis elegans. It is shown that decomposition of those dynamic modes allows for separating probe from autofluorescence without invoking a particular model for the bleaching process. In a second application, DMD of dye-specific photobleaching is used to separate two green-fluorescent dyes, an NBD-tagged sphingolipid and Alexa488-transferrin, thereby assigning them to different cellular compartments. Conclusions Data-based decomposition of dynamic modes can be employed to analyze spatially varying photobleaching of fluorescent probes in cells and tissues for spatial and temporal image segmentation, discrimination of probe from autofluorescence and image denoising. The new method should find wide application in analysis of dynamic fluorescence imaging data. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-022-04881-x.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology and Physics of Life Sciences (PhyLife) Center, University of Southern Denmark, Campusvej 55, DK-5230, Odense, Denmark.
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5
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Lazniewska J, Bader C, Hickey SM, Selemidis S, O'Leary J, Simpson PV, Stagni S, Plush SE, Massi M, Brooks D. Rhenium(I) conjugates as tools for tracking cholesterol in cells. Metallomics 2022; 14:6601455. [PMID: 35657681 PMCID: PMC9344854 DOI: 10.1093/mtomcs/mfac040] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/17/2022] [Indexed: 11/15/2022]
Abstract
Cholesterol is vital to control membrane integrity and fluidity, but is also a precursor to produce steroid hormones, bile acids, and vitamin D. Consequently, altered cholesterol biology has been linked to many diseases, including metabolic syndromes and cancer. Defining the intracellular pools of cholesterol and its trafficking within cells is essential to understand both normal cell physiology and mechanisms of pathogenesis. We have synthesized a new cholesterol mimic (ReTEGCholestanol), comprising a luminescent rhenium metal complex and a cholestanol targeting unit, linked using a tetraethylene glycol (TEG) spacer. ReTEGCholestanol demonstrated favourable imaging properties and improved water solubility when compared to a cholesterol derivative, and structurally related probes lacking the TEG linker. A non-malignant and three malignant prostate cell lines were used to characterize the uptake and intracellular distribution of ReTEGCholestanol. The ReTEGCholestanol complex was effectively internalized and mainly localized to late endosomes/lysosomes in non-malignant PNT1a cells, while in prostate cancer cells it also accumulated in early endosomes and multivesicular bodies, suggesting disturbed cholesterol biology in the malignant cells. The ReTEGCholestanol is a novel imaging agent for visualizing endosomal uptake and trafficking, which may be used to define cholesterol related biology including membrane integration and altered lipid trafficking/processing.
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Affiliation(s)
| | | | - Shane M Hickey
- UniSA Clinical and Health Sciences, University of South Australia, Adelaide, South Australia 5001, Australia
| | - Stavros Selemidis
- Department of Human Biosciences, RMIT University, Melbourne, Victoria 3000, Australia
| | - John O'Leary
- Discipline of Histopathology, University of Dublin Trinity College, Dublin 2, Ireland
| | - Peter V Simpson
- School of Molecular and Life Sciences - Curtin University, Bentley, Western Australia 6102, Australia
| | - Stefano Stagni
- Department of Industrial Chemistry Toso Montanari, University of Bologna, Via Zamboni, 33, Bologna I-40136, Italy
| | - Sally E Plush
- UniSA Clinical and Health Sciences, University of South Australia, Adelaide, South Australia 5001, Australia
| | - Massimiliano Massi
- School of Molecular and Life Sciences - Curtin University, Bentley, Western Australia 6102, Australia
| | - Doug Brooks
- Correspondence: School of Molecular and Life Sciences - Curtin University, Bentley, Western Australia 6102, Australia. Tel: +61-8-830-21229; E-mail:
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6
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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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7
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Understanding and Treating Niemann-Pick Type C Disease: Models Matter. Int J Mol Sci 2020; 21:ijms21238979. [PMID: 33256121 PMCID: PMC7730076 DOI: 10.3390/ijms21238979] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 02/06/2023] Open
Abstract
Biomedical research aims to understand the molecular mechanisms causing human diseases and to develop curative therapies. So far, these goals have been achieved for a small fraction of diseases, limiting factors being the availability, validity, and use of experimental models. Niemann–Pick type C (NPC) is a prime example for a disease that lacks a curative therapy despite substantial breakthroughs. This rare, fatal, and autosomal-recessive disorder is caused by defects in NPC1 or NPC2. These ubiquitously expressed proteins help cholesterol exit from the endosomal–lysosomal system. The dysfunction of either causes an aberrant accumulation of lipids with patients presenting a large range of disease onset, neurovisceral symptoms, and life span. Here, we note general aspects of experimental models, we describe the line-up used for NPC-related research and therapy development, and we provide an outlook on future topics.
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8
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Petersen D, Reinholdt P, Szomek M, Hansen SK, Poongavanam V, Dupont A, Heegaard CW, Krishnan K, Fujiwara H, Covey DF, Ory DS, Kongsted J, Wüstner D. Binding and intracellular transport of 25-hydroxycholesterol by Niemann-Pick C2 protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183063. [PMID: 31521631 DOI: 10.1016/j.bbamem.2019.183063] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 08/26/2019] [Accepted: 09/09/2019] [Indexed: 12/16/2022]
Abstract
Side-chain oxidized cholesterol derivatives, like 25-hydroxycholesterol (25-OH-Chol) are important regulators of cellular cholesterol homeostasis. How transport of oxysterols through the endo-lysosomal pathway contributes to their biological function is not clear. The Niemann-Pick C2 protein (NPC2) is a small lysosomal sterol transfer protein required for export of cholesterol from late endosomes and lysosomes (LE/LYSs). Here, we show that 25-hydroxy-cholestatrienol, (25-OH-CTL), an intrinsically fluorescent analogue of 25-OH-Chol, becomes trapped in LE/LYSs of NPC2-deficient fibroblasts, but can efflux from the cells even in the absence of NPC2 upon removal of the sterol source. Fluorescence recovery after photobleaching (FRAP) of 25-OH-CTL in endo-lysosomes was rapid and extensive and only partially dependent on NPC2 function. Using quenching of NPC2's intrinsic fluorescence, we show that 25-OH-Chol and 25-OH-CTL can bind to NPC2 though with lower affinity compared to cholesterol and its fluorescent analogues, cholestatrienol (CTL) and dehydroergosterol (DHE). This is confirmed by calculations of binding energies which additionally show that 25-OH-CTL can bind in two orientations to NPC2, in stark contrast to cholesterol and its analogues. We conclude that NPC2's affinity for all sterols is energetically favored over their self-aggregation in the lysosomal lumen. Lysosomal export of 25-OH-Chol is not strictly dependent on the NPC2 protein.
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Affiliation(s)
- Daniel Petersen
- Department of Biochemistry and Molecular Biology, DK-5230 Odense M, Denmark
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, DK-5230 Odense M, Denmark
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, DK-5230 Odense M, Denmark
| | | | | | - Alice Dupont
- Department of Biochemistry and Molecular Biology, DK-5230 Odense M, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus, C, Denmark
| | - Kathiresan Krishnan
- Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
| | - Hideji Fujiwara
- Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA; Taylor Family Institute for Innovative Psychiatric Research, Washington University, St. Louis, MO 63110, USA
| | - Daniel S Ory
- Department of Medicine, Washington University, St. Louis, MO 63110, USA
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, DK-5230 Odense M, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, DK-5230 Odense M, Denmark.
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9
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Borjihan Q, Yang J, Song Q, Gao L, Xu M, Gao T, Liu W, Li P, Li Q, Dong A. Povidone-iodine-functionalized fluorinated copolymers with dual-functional antibacterial and antifouling activities. Biomater Sci 2019; 7:3334-3347. [DOI: 10.1039/c9bm00583h] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Povidone-iodine-functionalized fluorinated polymer coatings with dual-functional antibacterial and antifouling activities should be very promising in practical biomedical applications.
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Affiliation(s)
- Qinggele Borjihan
- College of Chemistry and Chemical Engineering
- Inner Mongolia University
- Hohhot 010021
- People's Republic of China
| | - Jiebing Yang
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education
- School of Life Sciences
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Qing Song
- Xi'an Institute of Flexible Electronics & Xi'an Institute of Biomedical Materials and Engineering
- Northwestern Polytechnical University (NPU)
- Xi'an 710072
- China
| | - Lingling Gao
- Xi'an Institute of Flexible Electronics & Xi'an Institute of Biomedical Materials and Engineering
- Northwestern Polytechnical University (NPU)
- Xi'an 710072
- China
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM)
| | - Miao Xu
- Xi'an Institute of Flexible Electronics & Xi'an Institute of Biomedical Materials and Engineering
- Northwestern Polytechnical University (NPU)
- Xi'an 710072
- China
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM)
| | - Tianyi Gao
- College of Chemistry and Chemical Engineering
- Inner Mongolia University
- Hohhot 010021
- People's Republic of China
| | - Wenxin Liu
- College of Chemistry and Chemical Engineering
- Inner Mongolia University
- Hohhot 010021
- People's Republic of China
| | - Peng Li
- Xi'an Institute of Flexible Electronics & Xi'an Institute of Biomedical Materials and Engineering
- Northwestern Polytechnical University (NPU)
- Xi'an 710072
- China
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM)
| | - Quanshun Li
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education
- School of Life Sciences
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Alideertu Dong
- College of Chemistry and Chemical Engineering
- Inner Mongolia University
- Hohhot 010021
- People's Republic of China
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10
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Bonvicini A, Reinholdt P, Tognetti V, Joubert L, Wüstner D, Kongsted J. Rational design of novel fluorescent analogues of cholesterol: a “step-by-step” computational study. Phys Chem Chem Phys 2019; 21:15487-15503. [DOI: 10.1039/c9cp01902b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
State-of-the-art quantum chemical and molecular dynamics simulations are used as guidelines in design of novel fluorescent analogues of cholesterol.
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Affiliation(s)
- Andrea Bonvicini
- Normandy Univ. COBRA UMR 6014 & FR 3038
- Université de Rouen
- INSA Rouen
- CNRS
- 76821 Mont Saint Aignan
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy
- University of Southern Denmark
- Odense M
- Denmark
| | - Vincent Tognetti
- Normandy Univ. COBRA UMR 6014 & FR 3038
- Université de Rouen
- INSA Rouen
- CNRS
- 76821 Mont Saint Aignan
| | - Laurent Joubert
- Normandy Univ. COBRA UMR 6014 & FR 3038
- Université de Rouen
- INSA Rouen
- CNRS
- 76821 Mont Saint Aignan
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology
- University of Southern Denmark
- DK-5230 Odense
- Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy
- University of Southern Denmark
- Odense M
- Denmark
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11
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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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12
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Modzel M, Solanko KA, Szomek M, Hansen SK, Dupont A, Nåbo LJ, Kongsted J, Wüstner D. Live-cell imaging of new polyene sterols for improved analysis of intracellular cholesterol transport. J Microsc 2018. [PMID: 29516493 DOI: 10.1111/jmi.12691] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Analysis of intracellular cholesterol transport by fluorescence microscopy requires suitable fluorescent analogues of cholesterol. Most existing cholesterol analogues contain lipophilic dyes which can compromise the sterol properties in membranes. An alternative strategy is to introduce additional double bonds into the sterol ring system resulting in intrinsic fluorescence, while at the same time keeping the cholesterol-like properties of the analogues. Existing polyene sterols, such as dehydroergosterol (DHE) or cholestatrienol (CTL), however, contain only three double bonds and suffer from low brightness, significant photobleaching and excitation/emission in the ultraviolet region. Thus, special equipment is required to image such sterols. Here, we describe synthesis, characterization and intracellular imaging of new polyene sterols containing four conjugated double bonds in the sterol ring system. We show that such analogues have red-shifted excitation and emission by ∼20 nm compared to DHE or CTL. The red shift was even more pronounced when preventing keto-enol tautomer equilibration by protecting the 3'-hydroxy group with acetate. We show that the latter analogue can be imaged on a conventional wide field microscope with a DAPI/filipin filter cube. The new polyene sterols show reduced photobleaching compared to DHE or CTL allowing for improved deconvolution microscopy of sterol containing cellular membranes.
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Affiliation(s)
- M Modzel
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - K A Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - M Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - S K Hansen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - A Dupont
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - L J Nåbo
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense, Denmark
| | - J Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense, Denmark
| | - D Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
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13
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Solanko LM, Sullivan DP, Sere YY, Szomek M, Lunding A, Solanko KA, Pizovic A, Stanchev LD, Pomorski TG, Menon AK, Wüstner D. Ergosterol is mainly located in the cytoplasmic leaflet of the yeast plasma membrane. Traffic 2018; 19:198-214. [DOI: 10.1111/tra.12545] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 12/22/2017] [Accepted: 12/22/2017] [Indexed: 12/20/2022]
Affiliation(s)
- Lukasz M. Solanko
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
| | - David P. Sullivan
- Department of BiochemistryWeill Cornell Medical College New York, New York
| | - Yves Y. Sere
- Department of BiochemistryWeill Cornell Medical College New York, New York
| | - Maria Szomek
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
| | - Anita Lunding
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
| | - Katarzyna A. Solanko
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
| | - Azra Pizovic
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
| | - Lyubomir D. Stanchev
- Department of Plant and Environmental SciencesUniversity of Copenhagen Frederiksberg C Denmark
- Department of Molecular BiochemistryRuhr‐University Bochum Bochum Germany
| | - Thomas Günther Pomorski
- Department of Plant and Environmental SciencesUniversity of Copenhagen Frederiksberg C Denmark
- Department of Molecular BiochemistryRuhr‐University Bochum Bochum Germany
| | - Anant K. Menon
- Department of BiochemistryWeill Cornell Medical College New York, New York
| | - Daniel Wüstner
- Department of Biochemistry and Molecular BiologyUniversity of Southern Denmark Odense M Denmark
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14
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A Discontinuous Galerkin Model for Fluorescence Loss in Photobleaching. Sci Rep 2018; 8:1387. [PMID: 29362364 PMCID: PMC5780497 DOI: 10.1038/s41598-018-19159-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 12/21/2017] [Indexed: 11/09/2022] Open
Abstract
Fluorescence loss in photobleaching (FLIP) is a modern microscopy method for visualization of transport processes in living cells. This paper presents the simulation of FLIP sequences based on a calibrated reaction-diffusion system defined on segmented cell images. By the use of a discontinuous Galerkin method, the computational complexity is drastically reduced compared to continuous Galerkin methods. Using this approach on green fluorescent protein (GFP), we can determine its intracellular diffusion constant, the strength of localized hindrance to diffusion as well as the permeability of the nuclear membrane for GFP passage, directly from the FLIP image series. Thus, we present for the first time, to our knowledge, a quantitative computational FLIP method for inferring several molecular transport parameters in parallel from FLIP image data acquired at commercial microscope systems.
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15
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Dojčilović R, Pajović JD, Božanić DK, Bogdanović U, Vodnik VV, Dimitrijević-Branković S, Miljković MG, Kaščaková S, Réfrégiers M, Djoković V. Interaction of amino acid-functionalized silver nanoparticles and Candida albicans polymorphs: A deep-UV fluorescence imaging study. Colloids Surf B Biointerfaces 2017; 155:341-348. [PMID: 28454063 DOI: 10.1016/j.colsurfb.2017.04.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/29/2017] [Accepted: 04/19/2017] [Indexed: 01/01/2023]
Abstract
The interaction of the tryptophan functionalized Ag nanoparticles and live Candida albicans cells was studied by synchrotron excitation deep-ultraviolet (DUV) fluorescence imaging at the DISCO beamline of Synchrotron SOLEIL. DUV imaging showed that incubation of the fungus with functionalized nanoparticles results in significant increase in the fluorescence signal. The analysis of the images revealed that the interaction of the nanoparticles with (pseudo)hyphae polymorphs of the diploid fungus was less pronounced than in the case of yeast cells or budding spores. The changes in the intensity of the fluorescence signals of the cells after incubation were followed in [327-353nm] and [370-410nm] spectral ranges that correspond to the fluorescence of tryptophan in non-polar and polar environment, respectively. As a consequence of the environmental sensitivity of the silver-tryptophan fluorescent nanoprobe, we were able to determine the possible accumulation sites of the nanoparticles. The analysis of the intensity decay kinetics showed that the photobleaching effects were more pronounced in the case of the functionalized nanoparticle treated cells. The results of time-integrated emission in the mentioned spectral ranges suggested that the nanoparticles penetrate the cells, but that the majority of the nanoparticles attach to the cells' surfaces.
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Affiliation(s)
- Radovan Dojčilović
- Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia
| | - Jelena D Pajović
- Faculty of Physics, University of Belgrade, P. O. Box 368, 11001 Belgrade, Serbia; DISCO Beamline, Synchrotron SOLEIL, F-91192 Gif sur Yvette, France
| | - Dušan K Božanić
- Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia; DESIRS Beamline, Synchrotron SOLEIL, F-91192 Gif sur Yvette, France.
| | - Una Bogdanović
- Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia
| | - Vesna V Vodnik
- Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia
| | - Suzana Dimitrijević-Branković
- Department of Bioengineering and Biotechnology, Faculty of Technology & Metallurgy, University of Belgrade, Karnegija 4, 11120 Belgrade, Serbia
| | - Miona G Miljković
- Department of Bioengineering and Biotechnology, Faculty of Technology & Metallurgy, University of Belgrade, Karnegija 4, 11120 Belgrade, Serbia
| | - Slavka Kaščaková
- Inserm Unité 1193, F-94800 Villejuif, France; Univ. Paris-Sud XI, UMR-S1193, F-94800 Villejuif, France
| | | | - Vladimir Djoković
- Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia.
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16
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Andilla J, Jorand R, Olarte OE, Dufour AC, Cazales M, Montagner YLE, Ceolato R, Riviere N, Olivo-Marin JC, Loza-Alvarez P, Lorenzo C. Imaging tissue-mimic with light sheet microscopy: A comparative guideline. Sci Rep 2017; 7:44939. [PMID: 28322312 PMCID: PMC5381005 DOI: 10.1038/srep44939] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 02/16/2017] [Indexed: 01/04/2023] Open
Abstract
Tissue mimics (TMs) on the scale of several hundred microns provide a beneficial cell culture configuration for in vitro engineered tissue and are currently under the spotlight in tissue engineering and regenerative medicine. Due to the cell density and size, TMs are fairly inaccessible to optical observation and imaging within these samples remains challenging. Light Sheet Fluorescence Microscopy (LSFM)- an emerging and attractive technique for 3D optical sectioning of large samples- appears to be a particularly well-suited approach to deal with them. In this work, we compared the effectiveness of different light sheet illumination modalities reported in the literature to improve resolution and/or light exposure for complex 3D samples. In order to provide an acute and fair comparative assessment, we also developed a systematic, computerized benchmarking method. The outcomes of our experiment provide meaningful information for valid comparisons and arises the main differences between the modalities when imaging different types of TMs.
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Affiliation(s)
- Jordi Andilla
- ICFO-Institut de Ciences Fotonique, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels, Barcelona, Spain
| | | | - Omar E Olarte
- ICFO-Institut de Ciences Fotonique, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels, Barcelona, Spain
| | - Alexandre C Dufour
- Institut Pasteur BioImage Analysis Unit, F-75015, Paris, France.,CNRS, UMR-3691, F-75015 Paris, France
| | | | - Yoann L E Montagner
- Institut Pasteur BioImage Analysis Unit, F-75015, Paris, France.,CNRS, UMR-3691, F-75015 Paris, France
| | - Romain Ceolato
- Onera, The French Aerospace Lab, F-31100 Toulouse, France
| | | | | | - Pablo Loza-Alvarez
- ICFO-Institut de Ciences Fotonique, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels, Barcelona, Spain
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17
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Solanko KA, Modzel M, Solanko LM, Wüstner D. Fluorescent Sterols and Cholesteryl Esters as Probes for Intracellular Cholesterol Transport. Lipid Insights 2016; 8:95-114. [PMID: 27330304 PMCID: PMC4902042 DOI: 10.4137/lpi.s31617] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 04/04/2016] [Accepted: 04/07/2016] [Indexed: 12/20/2022] Open
Abstract
Cholesterol transport between cellular organelles comprised vesicular trafficking and nonvesicular exchange; these processes are often studied by quantitative fluorescence microscopy. A major challenge for using this approach is producing analogs of cholesterol with suitable brightness and structural and chemical properties comparable with those of cholesterol. This review surveys currently used fluorescent sterols with respect to their behavior in model membranes, their photophysical properties, as well as their transport and metabolism in cells. In the first part, several intrinsically fluorescent sterols, such as dehydroergosterol or cholestatrienol, are discussed. These polyene sterols (P-sterols) contain three conjugated double bonds in the steroid ring system, giving them slight fluorescence in ultraviolet light. We discuss the properties of P-sterols relative to cholesterol, outline their chemical synthesis, and explain how to image them in living cells and organisms. In particular, we show that P-sterol esters inserted into low-density lipoprotein can be tracked in the fibroblasts of Niemann–Pick disease using high-resolution deconvolution microscopy. We also describe fluorophore-tagged cholesterol probes, such as BODIPY-, NBD-, Dansyl-, or Pyrene-tagged cholesterol, and eventual esters of these analogs. Finally, we survey the latest developments in the synthesis and use of alkyne cholesterol analogs to be labeled with fluorophores by click chemistry and discuss the potential of all approaches for future applications.
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Affiliation(s)
- Katarzyna A Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| | - Maciej Modzel
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| | - Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
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18
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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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19
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Lencione D, Gehlen MH, Trujillo LN, Leitao RCF, Albuquerque RQ. The spatial distribution of the photostability of thionine in zeolite L nanochannels investigated by Photobleaching Lifetime Imaging Microscopy. Photochem Photobiol Sci 2016; 15:398-404. [DOI: 10.1039/c5pp00418g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PbLIM is used to investigate the photostability of thionine in zeolite L. The gradient in the spatial distribution of the photostability is ascribed to a non-homogeneous distribution of active oxygen in the channels after irradiation.
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Affiliation(s)
- Diego Lencione
- Instituto de Química de São Carlos
- Universidade de São Paulo
- 13566-590 São Carlos
- Brazil
| | - Marcelo H. Gehlen
- Instituto de Química de São Carlos
- Universidade de São Paulo
- 13566-590 São Carlos
- Brazil
| | - Loren N. Trujillo
- Instituto de Química de São Carlos
- Universidade de São Paulo
- 13566-590 São Carlos
- Brazil
| | - Renan C. F. Leitao
- Instituto de Química de São Carlos
- Universidade de São Paulo
- 13566-590 São Carlos
- Brazil
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20
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Nåbo LJ, List NH, Witzke S, Wüstner D, Khandelia H, Kongsted J. Design of new fluorescent cholesterol and ergosterol analogs: Insights from theory. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2188-99. [DOI: 10.1016/j.bbamem.2015.04.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/24/2015] [Accepted: 04/29/2015] [Indexed: 12/23/2022]
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21
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Mendenhall AR, Tedesco PM, Sands B, Johnson TE, Brent R. Single Cell Quantification of Reporter Gene Expression in Live Adult Caenorhabditis elegans Reveals Reproducible Cell-Specific Expression Patterns and Underlying Biological Variation. PLoS One 2015; 10:e0124289. [PMID: 25946008 PMCID: PMC4422670 DOI: 10.1371/journal.pone.0124289] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 03/07/2015] [Indexed: 11/22/2022] Open
Abstract
In multicellular organisms such as Caenorhabditis elegans, differences in complex phenotypes such as lifespan correlate with the level of expression of particular engineered reporter genes. In single celled organisms, quantitative understanding of responses to extracellular signals and of cell-to-cell variation in responses has depended on precise measurement of reporter gene expression. Here, we developed microscope-based methods to quantify reporter gene expression in cells of Caenorhabditis elegans with low measurement error. We then quantified expression in strains that carried different configurations of Phsp-16.2-fluorescent-protein reporters, in whole animals, and in all 20 cells of the intestine tissue, which is responsible for most of the fluorescent signal. Some animals bore more recently developed single copy Phsp-16.2 reporters integrated at defined chromosomal sites, others, “classical” multicopy reporter gene arrays integrated at random sites. At the level of whole animals, variation in gene expression was similar: strains with single copy reporters showed the same amount of animal-to-animal variation as strains with multicopy reporters. At the level of cells, in animals with single copy reporters, the pattern of expression in cells within the tissue was highly stereotyped. In animals with multicopy reporters, the cell-specific expression pattern was also stereotyped, but distinct, and somewhat more variable. Our methods are rapid and gentle enough to allow quantification of expression in the same cells of an animal at different times during adult life. They should allow investigators to use changes in reporter expression in single cells in tissues as quantitative phenotypes, and link those to molecular differences. Moreover, by diminishing measurement error, they should make possible dissection of the causes of the remaining, real, variation in expression. Understanding such variation should help reveal its contribution to differences in complex phenotypic outcomes in multicellular organisms.
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Affiliation(s)
- Alexander R. Mendenhall
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail: (RB); (ARM)
| | - Patricia M. Tedesco
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
| | - Bryan Sands
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Thomas E. Johnson
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
- Biofrontiers Institute, University of Colorado, Boulder, Colorado, United States of America
| | - Roger Brent
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail: (RB); (ARM)
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22
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Lee HJ, Zhang W, Zhang D, Yang Y, Liu B, Barker EL, Buhman KK, Slipchenko LV, Dai M, Cheng JX. Assessing cholesterol storage in live cells and C. elegans by stimulated Raman scattering imaging of phenyl-Diyne cholesterol. Sci Rep 2015; 5:7930. [PMID: 25608867 PMCID: PMC4302291 DOI: 10.1038/srep07930] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/22/2014] [Indexed: 02/07/2023] Open
Abstract
We report a cholesterol imaging method using rationally synthesized phenyl-diyne cholesterol (PhDY-Chol) and stimulated Raman scattering (SRS) microscope. The phenyl-diyne group is biologically inert and provides a Raman scattering cross section that is 88 times larger than the endogenous C = O stretching mode. SRS microscopy offers an imaging speed that is faster than spontaneous Raman microscopy by three orders of magnitude, and a detection sensitivity of 31 μM PhDY-Chol (~1,800 molecules in the excitation volume). Inside living CHO cells, PhDY-Chol mimics the behavior of cholesterol, including membrane incorporation and esterification. In a cellular model of Niemann-Pick type C disease, PhDY-Chol reflects the lysosomal accumulation of cholesterol, and shows relocation to lipid droplets after HPβCD treatment. In live C. elegans, PhDY-Chol mimics cholesterol uptake by intestinal cells and reflects cholesterol storage. Together, our work demonstrates an enabling platform for study of cholesterol storage and trafficking in living cells and vital organisms.
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Affiliation(s)
- Hyeon Jeong Lee
- Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, USA
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN, USA
| | - Wandi Zhang
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - Delong Zhang
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - Yang Yang
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - Bin Liu
- National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150080, China
| | - Eric L. Barker
- Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, USA
- Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
| | - Kimberly K. Buhman
- Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, USA
- Department of Nutrition Science, Purdue University, West Lafayette, IN, USA
| | | | - Mingji Dai
- Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, USA
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - Ji-Xin Cheng
- Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, USA
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
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23
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Wüstner D, Christensen T, Solanko LM, Sage D. Photobleaching kinetics and time-integrated emission of fluorescent probes in cellular membranes. Molecules 2014; 19:11096-130. [PMID: 25076144 PMCID: PMC6271172 DOI: 10.3390/molecules190811096] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 07/04/2014] [Accepted: 07/10/2014] [Indexed: 12/02/2022] Open
Abstract
Since the pioneering work of Hirschfeld, it is known that time-integrated emission (TiEm) of a fluorophore is independent of fluorescence quantum yield and illumination intensity. Practical implementation of this important result for determining exact probe distribution in living cells is often hampered by the presence of autofluorescence. Using kinetic modelling of photobleaching combined with pixel-wise bleach rate fitting of decay models with an updated plugin to the ImageJ program, it is shown that the TiEm of a fluorophore in living cells can be determined exactly from the product of bleaching amplitude and time constant. This applies to mono-exponential bleaching from the first excited singlet and/or triplet state and to multi-exponential combinations of such processes. The TiEm can be used to correct for illumination shading and background autofluorescence without the need for fluorescent test layers or separate imaging of non-stained cells. We apply the method to simulated images and to images of cells, whose membranes were labelled with fluorescent sterols and sphingolipids. Our bleaching model can be extended to include a probability density function (PDF) of intrinsic bleach rate constants with a memory kernel. This approach results in a time-dependent bleach rate coefficient and is exemplified for fluorescent sterols in restricted intracellular environments, like lipid droplets. We show that for small deviations from the classical exponential bleaching, the TiEm of decay functions with rate coefficients remains largely independent of fluorescence lifetime and illumination, and thereby represents a faithful measure of probe distribution.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Tanja Christensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Daniel Sage
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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24
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Pourmousa M, Róg T, Mikkeli R, Vattulainen L, Solanko LM, Wüstner D, List NH, Kongsted J, Karttunen M. Dehydroergosterol as an Analogue for Cholesterol: Why It Mimics Cholesterol So Well—or Does It? J Phys Chem B 2014; 118:7345-57. [DOI: 10.1021/jp406883k] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Mohsen Pourmousa
- Department
of Physics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
| | - Tomasz Róg
- Department
of Physics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
| | - Risto Mikkeli
- Department
of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Finland
| | - llpo Vattulainen
- Department
of Physics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
- MEMPHYS−Center
of Biomembrane Physics, Physics Department, University of Southern Denmark, Odense, Denmark
| | | | | | | | | | - Mikko Karttunen
- Department
of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo N2L 3G1, Ontario, Canada
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25
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VanDelinder V, Bachand GD. Photodamage and the Importance of Photoprotection in Biomolecular-Powered Device Applications. Anal Chem 2013; 86:721-8. [DOI: 10.1021/ac403187g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Virginia VanDelinder
- Center
for Integrated Nanotechnologies,
Sandia National Laboratories, Albuquerque, NM 87185, United States
| | - George D. Bachand
- Center
for Integrated Nanotechnologies,
Sandia National Laboratories, Albuquerque, NM 87185, United States
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26
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Urbančič I, Arsov Z, Ljubetič A, Biglino D, Strancar J. Bleaching-corrected fluorescence microspectroscopy with nanometer peak position resolution. OPTICS EXPRESS 2013; 21:25291-25306. [PMID: 24150370 DOI: 10.1364/oe.21.025291] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fluorescence microspectroscopy (FMS) with environmentally sensitive dyes provides information about local molecular surroundings at microscopic spatial resolution. Until recently, only probes exhibiting large spectral shifts due to local changes have been used. For filter-based experimental systems, where signal at different wavelengths is acquired sequentially, photostability has been required in addition. Herein, we systematically analyzed our spectral fitting models and bleaching correction algorithms which mitigate both limitations. We showed that careful analysis of data acquired by stochastic wavelength sampling enables nanometer spectral peak position resolution even for highly photosensitive fluorophores. To demonstrate how small spectral shifts and changes in bleaching rates can be exploited, we analyzed vesicles in different lipid phases. Our findings suggest that a wide range of dyes, commonly used in bulk spectrofluorimetry but largely avoided in microspectroscopy due to the above-mentioned restrictions, can be efficiently applied also in FMS.
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27
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Wüstner D, Solanko LM, Lund FW, Sage D, Schroll HJ, Lomholt MA. Quantitative fluorescence loss in photobleaching for analysis of protein transport and aggregation. BMC Bioinformatics 2012; 13:296. [PMID: 23148417 PMCID: PMC3557157 DOI: 10.1186/1471-2105-13-296] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 10/31/2012] [Indexed: 12/23/2022] Open
Abstract
Background Fluorescence loss in photobleaching (FLIP) is a widely used imaging technique, which provides information about protein dynamics in various cellular regions. In FLIP, a small cellular region is repeatedly illuminated by an intense laser pulse, while images are taken with reduced laser power with a time lag between the bleaches. Despite its popularity, tools are lacking for quantitative analysis of FLIP experiments. Typically, the user defines regions of interest (ROIs) for further analysis which is subjective and does not allow for comparing different cells and experimental settings. Results We present two complementary methods to detect and quantify protein transport and aggregation in living cells from FLIP image series. In the first approach, a stretched exponential (StrExp) function is fitted to fluorescence loss (FL) inside and outside the bleached region. We show by reaction–diffusion simulations, that the StrExp function can describe both, binding/barrier–limited and diffusion-limited FL kinetics. By pixel-wise regression of that function to FL kinetics of enhanced green fluorescent protein (eGFP), we determined in a user-unbiased manner from which cellular regions eGFP can be replenished in the bleached area. Spatial variation in the parameters calculated from the StrExp function allow for detecting diffusion barriers for eGFP in the nucleus and cytoplasm of living cells. Polyglutamine (polyQ) disease proteins like mutant huntingtin (mtHtt) can form large aggregates called inclusion bodies (IB’s). The second method combines single particle tracking with multi-compartment modelling of FL kinetics in moving IB’s to determine exchange rates of eGFP-tagged mtHtt protein (eGFP-mtHtt) between aggregates and the cytoplasm. This method is self-calibrating since it relates the FL inside and outside the bleached regions. It makes it therefore possible to compare release kinetics of eGFP-mtHtt between different cells and experiments. Conclusions We present two complementary methods for quantitative analysis of FLIP experiments in living cells. They provide spatial maps of exchange dynamics and absolute binding parameters of fluorescent molecules to moving intracellular entities, respectively. Our methods should be of great value for quantitative studies of intracellular transport.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, DK-5230, Denmark.
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28
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Valdes VJ, Athie A, Salinas LS, Navarro RE, Vaca L. CUP-1 is a novel protein involved in dietary cholesterol uptake in Caenorhabditis elegans. PLoS One 2012; 7:e33962. [PMID: 22479487 PMCID: PMC3313951 DOI: 10.1371/journal.pone.0033962] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 02/22/2012] [Indexed: 01/15/2023] Open
Abstract
Sterols transport and distribution are essential processes in all multicellular organisms. Survival of the nematode Caenorhabditis elegans depends on dietary absorption of sterols present in the environment. However the general mechanisms associated to sterol uptake in nematodes are poorly understood. In the present work we provide evidence showing that a previously uncharacterized transmembrane protein, designated Cholesterol Uptake Protein-1 (ChUP-1), [corrected] is involved in dietary cholesterol uptake in C. elegans. Animals lacking ChUP-1 [corrected] showed hypersensitivity to cholesterol limitation and were unable to uptake cholesterol. A ChUP-1-GFP [corrected] fusion protein colocalized with cholesterol-rich vesicles, endosomes and lysosomes as well as the plasma membrane. Additionally, by FRET imaging, a direct interaction was found between the cholesterol analog DHE and the transmembrane "cholesterol recognition/interaction amino acid consensus" (CRAC) motif present in C. elegans ChUP-1. [corrected]. In-silico analysis identified two mammalian homologues of ChUP-1. [corrected]. Most interestingly, CRAC motifs are conserved in mammalian ChUP-1 [corrected] homologous. Our results suggest a role of ChUP-1 [corrected] in cholesterol uptake in C. elegans and open up the possibility for the existence of a new class of proteins involved in sterol absorption in mammals.
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Affiliation(s)
| | | | | | - Rosa E. Navarro
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF, México
| | - Luis Vaca
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF, México
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Wiese M, Antebi A, Zheng H. Regulation of neuronal APL-1 expression by cholesterol starvation. PLoS One 2012; 7:e32038. [PMID: 22363792 PMCID: PMC3283687 DOI: 10.1371/journal.pone.0032038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 01/18/2012] [Indexed: 12/04/2022] Open
Abstract
Background Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of β-amyloid plaques composed primarily of the amyloid-β peptide, a cleavage product of amyloid precursor protein (APP). While mutations in APP lead to the development of Familial Alzheimer's Disease (FAD), sporadic AD has only one clear genetic modifier: the ε4 allele of the apolipoprotein E (ApoE) gene. Cholesterol starvation in Caenorhabditis elegans leads to molting and arrest phenotypes similar to loss-of-function mutants of the APP ortholog, apl-1 (amyloid precursor-like protein 1), and lrp-1 (lipoprotein receptor-related protein 1), suggesting a potential interaction between apl-1 and cholesterol metabolism. Methodology/Principal Findings Previously, we found that RNAi knock-down of apl-1 leads to aldicarb hypersensitivity, indicating a defect in synaptic function. Here we find the same defect is recapitulated during lrp-1 knock-down and by cholesterol starvation. A cholesterol-free diet or loss of lrp-1 directly affects APL-1 levels as both lead to loss of APL-1::GFP fluorescence in neurons. However, loss of cholesterol does not affect global transcription or protein levels as seen by qPCR and Western blot. Conclusions Our results show that cholesterol and lrp-1 are involved in the regulation of synaptic transmission, similar to apl-1. Both are able to modulate APL-1 protein levels in neurons, however cholesterol changes do not affect global apl-1 transcription or APL-1 protein indicating the changes are specific to neurons. Thus, regulation of synaptic transmission and molting by LRP-1 and cholesterol may be mediated by their ability to control APL-1 neuronal protein expression.
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Affiliation(s)
- Mary Wiese
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Adam Antebi
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Max Planck Institute for Biology of Ageing, Köln, Germany
- * E-mail: (AA); (HZ)
| | - Hui Zheng
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail: (AA); (HZ)
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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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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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Gimpl G, Gehrig-Burger K. Probes for studying cholesterol binding and cell biology. Steroids 2011; 76:216-31. [PMID: 21074546 DOI: 10.1016/j.steroids.2010.11.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 11/03/2010] [Accepted: 11/05/2010] [Indexed: 11/20/2022]
Abstract
Cholesterol is a multifunctional lipid in eukaryotic cells. It regulates the physical state of the phospholipid bilayer, is crucially involved in the formation of membrane microdomains, affects the activity of many membrane proteins, and is the precursor for steroid hormones and bile acids. Thus, cholesterol plays a profound role in the physiology and pathophysiology of eukaryotic cells. The cholesterol molecule has achieved evolutionary perfection to fulfill its different functions in membrane organization. Here, we review basic approaches to explore the interaction of cholesterol with proteins, with a particular focus on the high diversity of fluorescent and photoreactive cholesterol probes available today.
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Affiliation(s)
- Gerald Gimpl
- Institute of Pharmacy and Biochemistry, Department of Biochemistry, Johannes Gutenberg-University of Mainz, Mainz, Germany.
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Kohut P, Wüstner D, Hronska L, Kuchler K, Hapala I, Valachovic M. The role of ABC proteins Aus1p and Pdr11p in the uptake of external sterols in yeast: dehydroergosterol fluorescence study. Biochem Biophys Res Commun 2010; 404:233-8. [PMID: 21110944 DOI: 10.1016/j.bbrc.2010.11.099] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 11/22/2010] [Indexed: 12/22/2022]
Abstract
Uptake of external sterols in the yeast Saccharomyces cerevisiae is a multistep process limited to anaerobiosis or heme deficiency. It includes crossing the cell wall, insertion of sterol molecules into plasma membrane and their internalization and integration into intracellular membranes. We applied the fluorescent ergosterol analog dehydroergosterol (DHE) to monitor the initial steps of sterol uptake by three independent approaches: fluorescence spectroscopy, fluorescence microscopy and sterol quantification by HPLC. Using specific fluorescence characteristics of DHE we showed that the entry of sterol molecules into plasma membrane is not spontaneous but requires assistance of two ABC (ATP-binding cassette) pumps--Aus1p or Pdr11p. DHE taken up by uptake-competent hem1ΔAUS1PDR11 cells could be directly visualized by UV-sensitive wide field fluorescence microscopy. HPLC analysis of sterols revealed significant amounts of exogenous ergosterol and DHE (but not cholesterol) associated with uptake-deficient hem1Δaus1Δpdr11Δ cells. Fluorescent sterol associated with these cells did not show the characteristic emission spectrum of membrane-integrated DHE. The amount of cell-associated DHE was significantly reduced after enzymatic removal of the cell wall. Our results demonstrate that the yeast cell wall is actively involved in binding and uptake of ergosterol-like sterols.
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Affiliation(s)
- Peter Kohut
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji 90210, Slovak Republic
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