1
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Adler J, Bernhem K, Parmryd I. Membrane topography and the overestimation of protein clustering in single molecule localisation microscopy - identification and correction. Commun Biol 2024; 7:791. [PMID: 38951588 PMCID: PMC11217499 DOI: 10.1038/s42003-024-06472-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 06/19/2024] [Indexed: 07/03/2024] Open
Abstract
According to single-molecule localisation microscopy almost all plasma membrane proteins are clustered. We demonstrate that clusters can arise from variations in membrane topography where the local density of a randomly distributed membrane molecule to a degree matches the variations in the local amount of membrane. Further, we demonstrate that this false clustering can be differentiated from genuine clustering by using a membrane marker to report on local variations in the amount of membrane. In dual colour live cell single molecule localisation microscopy using the membrane probe DiI alongside either the transferrin receptor or the GPI-anchored protein CD59, we found that pair correlation analysis reported both proteins and DiI as being clustered, as did its derivative pair correlation-photoactivation localisation microscopy and nearest neighbour analyses. After converting the localisations into images and using the DiI image to factor out topography variations, no CD59 clusters were visible, suggesting that the clustering reported by the other methods is an artefact. However, the TfR clusters persisted after topography variations were factored out. We demonstrate that membrane topography variations can make membrane molecules appear clustered and present a straightforward remedy suitable as the first step in the cluster analysis pipeline.
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Affiliation(s)
- Jeremy Adler
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Kristoffer Bernhem
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Ingela Parmryd
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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2
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Pandey G, Budhathoki A, Spille JH. Characterizing Properties of Biomolecular Condensates Below the Diffraction Limit In Vivo. Methods Mol Biol 2023; 2563:425-445. [PMID: 36227487 DOI: 10.1007/978-1-0716-2663-4_22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Fluorescence microscopy assays enable the investigation of endogenous biomolecular condensates directly in their cellular context. With appropriate experimental designs, these assays yield quantitative information on condensate material properties and inform on biophysical mechanisms of condensate formation. Single-molecule super-resolution and tracking experiments grant access to the smallest condensates and early condensation stages not resolved by conventional imaging approaches. Here, we discuss considerations for using single-molecule assays to extract quantitative information about biomolecular condensates directly in their cellular context.
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Affiliation(s)
- Ganesh Pandey
- Department of Physics, University of Illinois at Chicago, Chicago, IL, USA
| | - Alisha Budhathoki
- Department of Physics, University of Illinois at Chicago, Chicago, IL, USA
| | - Jan-Hendrik Spille
- Department of Physics, University of Illinois at Chicago, Chicago, IL, USA.
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3
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Milstein JN, Nino DF, Zhou X, Gradinaru CC. Single-molecule counting applied to the study of GPCR oligomerization. Biophys J 2022; 121:3175-3187. [PMID: 35927960 PMCID: PMC9463696 DOI: 10.1016/j.bpj.2022.07.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/29/2022] [Accepted: 07/28/2022] [Indexed: 11/24/2022] Open
Abstract
Single-molecule counting techniques enable a precise determination of the intracellular abundance and stoichiometry of proteins and macromolecular complexes. These details are often challenging to quantitatively assess yet are essential for our understanding of cellular function. Consider G-protein-coupled receptors-an expansive class of transmembrane signaling proteins that participate in many vital physiological functions making them a popular target for drug development. While early evidence for the role of oligomerization in receptor signaling came from ensemble biochemical and biophysical assays, innovations in single-molecule measurements are now driving a paradigm shift in our understanding of its relevance. Here, we review recent developments in single-molecule counting with a focus on photobleaching step counting and the emerging technique of quantitative single-molecule localization microscopy-with a particular emphasis on the potential for these techniques to advance our understanding of the role of oligomerization in G-protein-coupled receptor signaling.
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Affiliation(s)
- Joshua N Milstein
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada.
| | - Daniel F Nino
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Xiaohan Zhou
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Claudiu C Gradinaru
- Department of Physics, University of Toronto, Toronto, Ontario, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada.
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4
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Vanslembrouck B, Chen JH, Larabell C, van Hengel J. Microscopic Visualization of Cell-Cell Adhesion Complexes at Micro and Nanoscale. Front Cell Dev Biol 2022; 10:819534. [PMID: 35517500 PMCID: PMC9065677 DOI: 10.3389/fcell.2022.819534] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 03/21/2022] [Indexed: 12/25/2022] Open
Abstract
Considerable progress has been made in our knowledge of the morphological and functional varieties of anchoring junctions. Cell-cell adhesion contacts consist of discrete junctional structures responsible for the mechanical coupling of cytoskeletons and allow the transmission of mechanical signals across the cell collective. The three main adhesion complexes are adherens junctions, tight junctions, and desmosomes. Microscopy has played a fundamental role in understanding these adhesion complexes on different levels in both physiological and pathological conditions. In this review, we discuss the main light and electron microscopy techniques used to unravel the structure and composition of the three cell-cell contacts in epithelial and endothelial cells. It functions as a guide to pick the appropriate imaging technique(s) for the adhesion complexes of interest. We also point out the latest techniques that have emerged. At the end, we discuss the problems investigators encounter during their cell-cell adhesion research using microscopic techniques.
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Affiliation(s)
- Bieke Vanslembrouck
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Department of Anatomy, University of San Francisco, San Francisco, CA, United States
- *Correspondence: Bieke Vanslembrouck, ; Jolanda van Hengel,
| | - Jian-hua Chen
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Department of Anatomy, University of San Francisco, San Francisco, CA, United States
| | - Carolyn Larabell
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Department of Anatomy, University of San Francisco, San Francisco, CA, United States
| | - Jolanda van Hengel
- Medical Cell Biology Research Group, Department of Human Structure and Repair, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
- *Correspondence: Bieke Vanslembrouck, ; Jolanda van Hengel,
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5
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Li A, Zhang X, Singla J, White K, Loconte V, Hu C, Zhang C, Li S, Li W, Francis JP, Wang C, Sali A, Sun L, He X, Stevens RC. Auto-segmentation and time-dependent systematic analysis of mesoscale cellular structure in β-cells during insulin secretion. PLoS One 2022; 17:e0265567. [PMID: 35324950 PMCID: PMC8947144 DOI: 10.1371/journal.pone.0265567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 03/03/2022] [Indexed: 02/07/2023] Open
Abstract
The mesoscale description of the subcellular organization informs about cellular mechanisms in disease state. However, applications of soft X-ray tomography (SXT), an important approach for characterizing organelle organization, are limited by labor-intensive manual segmentation. Here we report a pipeline for automated segmentation and systematic analysis of SXT tomograms. Our approach combines semantic and first-applied instance segmentation to produce separate organelle masks with high Dice and Recall indexes, followed by analysis of organelle localization based on the radial distribution function. We demonstrated this technique by investigating the organization of INS-1E pancreatic β-cell organization under different treatments at multiple time points. Consistent with a previous analysis of a similar dataset, our results revealed the impact of glucose stimulation on the localization and molecular density of insulin vesicles and mitochondria. This pipeline can be extended to SXT tomograms of any cell type to shed light on the subcellular rearrangements under different drug treatments.
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Affiliation(s)
- Angdi Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiangyi Zhang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jitin Singla
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Kate White
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Valentina Loconte
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Chuanyang Hu
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Chuyu Zhang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Shuailin Li
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Weimin Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - John Paul Francis
- Department of Computer Science, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA, United States of America
| | - Chenxi Wang
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Andrej Sali
- California Institute for Quantitative Biosciences, Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, United States of America
| | - Liping Sun
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xuming He
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
- Shanghai Engineering Research Center of Intelligent Vision and Imaging, Shanghai, China
| | - Raymond C. Stevens
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
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6
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Reiche MA, Aaron JS, Boehm U, DeSantis MC, Hobson CM, Khuon S, Lee RM, Chew TL. When light meets biology - how the specimen affects quantitative microscopy. J Cell Sci 2022; 135:274812. [PMID: 35319069 DOI: 10.1242/jcs.259656] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Fluorescence microscopy images should not be treated as perfect representations of biology. Many factors within the biospecimen itself can drastically affect quantitative microscopy data. Whereas some sample-specific considerations, such as photobleaching and autofluorescence, are more commonly discussed, a holistic discussion of sample-related issues (which includes less-routine topics such as quenching, scattering and biological anisotropy) is required to appropriately guide life scientists through the subtleties inherent to bioimaging. Here, we consider how the interplay between light and a sample can cause common experimental pitfalls and unanticipated errors when drawing biological conclusions. Although some of these discrepancies can be minimized or controlled for, others require more pragmatic considerations when interpreting image data. Ultimately, the power lies in the hands of the experimenter. The goal of this Review is therefore to survey how biological samples can skew quantification and interpretation of microscopy data. Furthermore, we offer a perspective on how to manage many of these potential pitfalls.
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Affiliation(s)
- Michael A Reiche
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Jesse S Aaron
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Ulrike Boehm
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Michael C DeSantis
- Light Microscopy Facility, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147,USA
| | - Chad M Hobson
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Satya Khuon
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA.,Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Rachel M Lee
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA.,Light Microscopy Facility, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147,USA
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7
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Hsiao YT, Tsai CN, Chen TH, Hsieh CL. Label-Free Dynamic Imaging of Chromatin in Live Cell Nuclei by High-Speed Scattering-Based Interference Microscopy. ACS NANO 2022; 16:2774-2788. [PMID: 34967599 DOI: 10.1021/acsnano.1c09748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Chromatin is a DNA-protein complex that is densely packed in the cell nucleus. The nanoscale chromatin compaction plays critical roles in the modulation of cell nuclear processes. However, little is known about the spatiotemporal dynamics of chromatin compaction states because it remains difficult to quantitatively measure the chromatin compaction level in live cells. Here, we demonstrate a strategy, referenced as DYNAMICS imaging, for mapping chromatin organization in live cell nuclei by analyzing the dynamic scattering signal of molecular fluctuations. Highly sensitive optical interference microscopy, coherent brightfield (COBRI) microscopy, is implemented to detect the linear scattering of unlabeled chromatin at a high speed. A theoretical model is established to determine the local chromatin density from the statistical fluctuation of the measured scattering signal. DYNAMICS imaging allows us to reconstruct a speckle-free nucleus map that is highly correlated to the fluorescence chromatin image. Moreover, together with calibration based on nanoparticle colloids, we show that the DYNAMICS signal is sensitive to the chromatin compaction level at the nanoscale. We confirm the effectiveness of DYNAMICS imaging in detecting the condensation and decondensation of chromatin induced by chemical drug treatments. Importantly, the stable scattering signal supports a continuous observation of the chromatin condensation and decondensation processes for more than 1 h. Using this technique, we detect transient and nanoscopic chromatin condensation events occurring on a time scale of a few seconds. Label-free DYNAMICS imaging offers the opportunity to investigate chromatin conformational dynamics and to explore their significance in various gene activities.
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Affiliation(s)
- Yi-Teng Hsiao
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, 1 Roosevelt Road Section 4, Taipei 10617, Taiwan
| | - Chia-Ni Tsai
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, 1 Roosevelt Road Section 4, Taipei 10617, Taiwan
| | - Te-Hsin Chen
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, 1 Roosevelt Road Section 4, Taipei 10617, Taiwan
| | - Chia-Lung Hsieh
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, 1 Roosevelt Road Section 4, Taipei 10617, Taiwan
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8
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Bond C, Santiago-Ruiz AN, Tang Q, Lakadamyali M. Technological advances in super-resolution microscopy to study cellular processes. Mol Cell 2022; 82:315-332. [PMID: 35063099 PMCID: PMC8852216 DOI: 10.1016/j.molcel.2021.12.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 01/22/2023]
Abstract
Since its initial demonstration in 2000, far-field super-resolution light microscopy has undergone tremendous technological developments. In parallel, these developments have opened a new window into visualizing the inner life of cells at unprecedented levels of detail. Here, we review the technical details behind the most common implementations of super-resolution microscopy and highlight some of the recent, promising advances in this field.
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Affiliation(s)
- Charles Bond
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Adriana N Santiago-Ruiz
- Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Qing Tang
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Melike Lakadamyali
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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9
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Prokop S, Ábrányi-Balogh P, Barti B, Vámosi M, Zöldi M, Barna L, Urbán GM, Tóth AD, Dudok B, Egyed A, Deng H, Leggio GM, Hunyady L, van der Stelt M, Keserű GM, Katona I. PharmacoSTORM nanoscale pharmacology reveals cariprazine binding on Islands of Calleja granule cells. Nat Commun 2021; 12:6505. [PMID: 34764251 PMCID: PMC8586358 DOI: 10.1038/s41467-021-26757-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 09/30/2021] [Indexed: 12/25/2022] Open
Abstract
Immunolabeling and autoradiography have traditionally been applied as the methods-of-choice to visualize and collect molecular information about physiological and pathological processes. Here, we introduce PharmacoSTORM super-resolution imaging that combines the complementary advantages of these approaches and enables cell-type- and compartment-specific nanoscale molecular measurements. We exploited rational chemical design for fluorophore-tagged high-affinity receptor ligands and an enzyme inhibitor; and demonstrated broad PharmacoSTORM applicability for three protein classes and for cariprazine, a clinically approved antipsychotic and antidepressant drug. Because the neurobiological substrate of cariprazine has remained elusive, we took advantage of PharmacoSTORM to provide in vivo evidence that cariprazine predominantly binds to D3 dopamine receptors on Islands of Calleja granule cell axons but avoids dopaminergic terminals. These findings show that PharmacoSTORM helps to quantify drug-target interaction sites at the nanoscale level in a cell-type- and subcellular context-dependent manner and within complex tissue preparations. Moreover, the results highlight the underappreciated neuropsychiatric significance of the Islands of Calleja in the ventral forebrain.
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Affiliation(s)
- Susanne Prokop
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
- School of Ph.D. Studies, Semmelweis University, Budapest, Hungary
| | - Péter Ábrányi-Balogh
- Medicinal Chemistry Research Group, Research Centre for Natural Sciences, Budapest, Hungary
| | - Benjámin Barti
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
- School of Ph.D. Studies, Semmelweis University, Budapest, Hungary
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Márton Vámosi
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Miklós Zöldi
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
- School of Ph.D. Studies, Semmelweis University, Budapest, Hungary
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - László Barna
- Nikon Center of Excellence for Neuronal Imaging, Institute of Experimental Medicine, Budapest, Hungary
| | - Gabriella M Urbán
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - András Dávid Tóth
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - Barna Dudok
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
- Department of Neurosurgery, Stanford University, Stanford, CA, USA
| | - Attila Egyed
- Medicinal Chemistry Research Group, Research Centre for Natural Sciences, Budapest, Hungary
| | - Hui Deng
- Department of Molecular Physiology, Leiden Institute of Chemistry, Leiden University & Oncode Institute, Leiden, the Netherlands
| | - Gian Marco Leggio
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, Catania, Italy
| | - László Hunyady
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - Mario van der Stelt
- Department of Molecular Physiology, Leiden Institute of Chemistry, Leiden University & Oncode Institute, Leiden, the Netherlands
| | - György M Keserű
- Medicinal Chemistry Research Group, Research Centre for Natural Sciences, Budapest, Hungary
| | - István Katona
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary.
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.
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10
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Abstract
Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron-glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.
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Affiliation(s)
- Christian Werner
- Department of Biotechnology & Biophysics, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology & Biophysics, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Christian Geis
- Section Translational Neuroimmunology, Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
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11
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Nienhaus K, Nienhaus GU. Fluorescent proteins of the EosFP clade: intriguing marker tools with multiple photoactivation modes for advanced microscopy. RSC Chem Biol 2021; 2:796-814. [PMID: 34458811 PMCID: PMC8341165 DOI: 10.1039/d1cb00014d] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/27/2021] [Indexed: 02/04/2023] Open
Abstract
Optical fluorescence microscopy has taken center stage in the exploration of biological structure and dynamics, especially on live specimens, and super-resolution imaging methods continue to deliver exciting new insights into the molecular foundations of life. Progress in the field, however, crucially hinges on advances in fluorescent marker technology. Among these, fluorescent proteins (FPs) of the GFP family are advantageous because they are genetically encodable, so that live cells, tissues or organisms can produce these markers all by themselves. A subclass of them, photoactivatable FPs, allow for control of their fluorescence emission by light irradiation, enabling pulse-chase imaging and super-resolution microscopy. In this review, we discuss FP variants of the EosFP clade that have been optimized by amino acid sequence modification to serve as markers for various imaging techniques. In general, two different modes of photoactivation are found, reversible photoswitching between a fluorescent and a nonfluorescent state and irreversible green-to red photoconversion. First, we describe their basic structural and optical properties. We then summarize recent research aimed at elucidating the photochemical processes underlying photoactivation. Finally, we briefly introduce various advanced imaging methods facilitated by specific EosFP variants, and show some exciting sample applications.
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Affiliation(s)
- Karin Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology 76049 Karlsruhe Germany
| | - Gerd Ulrich Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology 76049 Karlsruhe Germany
- Institute of Nanotechnology, Karlsruhe Institute of Technology 76021 Karlsruhe Germany
- Institute of Biological and Chemical Systems, Karlsruhe Institute of Technology 76021 Karlsruhe Germany
- Department of Physics, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
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12
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Tau forms oligomeric complexes on microtubules that are distinct from tau aggregates. Proc Natl Acad Sci U S A 2021; 118:2021461118. [PMID: 33952699 DOI: 10.1073/pnas.2021461118] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Tau is a microtubule-associated protein, which promotes neuronal microtubule assembly and stability. Accumulation of tau into insoluble aggregates known as neurofibrillary tangles (NFTs) is a pathological hallmark of several neurodegenerative diseases. The current hypothesis is that small, soluble oligomeric tau species preceding NFT formation cause toxicity. However, thus far, visualizing the spatial distribution of tau monomers and oligomers inside cells under physiological or pathological conditions has not been possible. Here, using single-molecule localization microscopy, we show that tau forms small oligomers on microtubules ex vivo. These oligomers are distinct from those found in cells exhibiting tau aggregation and could be precursors of aggregated tau in pathology. Furthermore, using an unsupervised shape classification algorithm that we developed, we show that different tau phosphorylation states are associated with distinct tau aggregate species. Our work elucidates tau's nanoscale composition under nonaggregated and aggregated conditions ex vivo.
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13
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Super-Resolution Imaging of Homologous Recombination Repair at Collapsed Replication Forks. Methods Mol Biol 2021; 2153:355-363. [PMID: 32840791 DOI: 10.1007/978-1-0716-0644-5_24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Single-molecule super-resolution microscopy (SRM) combines single-molecule detection with spatial resolutions tenfold improved over conventional confocal microscopy. These two key advantages make it possible to visualize individual DNA replication and damage events within the cellular context of fixed cells. This in turn engenders the ability to decipher variations between individual replicative and damage species within a single nucleus, elucidating different subpopulations of stress and repair events. Here, we describe the protocol for combining SRM with novel labeling and damage assays to characterize DNA double-strand break (DSB) induction at stressed replication forks (RFs) and subsequent repair by homologous recombination (HR). These assays enable spatiotemporal mapping of DNA damage response and repair proteins to establish their in vivo function and interactions, as well as detailed characterization of specific dysfunctions in HR caused by drugs or mutations of interest.
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15
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Salvage SC, Rees JS, McStea A, Hirsch M, Wang L, Tynan CJ, Reed MW, Irons JR, Butler R, Thompson AJ, Martin-Fernandez ML, Huang CL, Jackson AP. Supramolecular clustering of the cardiac sodium channel Nav1.5 in HEK293F cells, with and without the auxiliary β3-subunit. FASEB J 2020; 34:3537-3553. [PMID: 31950564 PMCID: PMC7079131 DOI: 10.1096/fj.201701473rr] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 09/30/2019] [Accepted: 10/08/2019] [Indexed: 01/24/2023]
Abstract
Voltage-gated sodium channels comprise an ion-selective α-subunit and one or more associated β-subunits. The β3-subunit (encoded by the SCN3B gene) is an important physiological regulator of the heart-specific sodium channel, Nav1.5. We have previously shown that when expressed alone in HEK293F cells, the full-length β3-subunit forms trimers in the plasma membrane. We extend this result with biochemical assays and use the proximity ligation assay (PLA) to identify oligomeric β3-subunits, not just at the plasma membrane, but throughout the secretory pathway. We then investigate the corresponding clustering properties of the α-subunit and the effects upon these of the β3-subunits. The oligomeric status of the Nav1.5 α-subunit in vivo, with or without the β3-subunit, has not been previously investigated. Using super-resolution fluorescence imaging, we show that under conditions typically used in electrophysiological studies, the Nav1.5 α-subunit assembles on the plasma membrane of HEK293F cells into spatially localized clusters rather than individual and randomly dispersed molecules. Quantitative analysis indicates that the β3-subunit is not required for this clustering but β3 does significantly change the distribution of cluster sizes and nearest-neighbor distances between Nav1.5 α-subunits. However, when assayed by PLA, the β3-subunit increases the number of PLA-positive signals generated by anti-(Nav1.5 α-subunit) antibodies, mainly at the plasma membrane. Since PLA can be sensitive to the orientation of proteins within a cluster, we suggest that the β3-subunit introduces a significant change in the relative alignment of individual Nav1.5 α-subunits, but the clustering itself depends on other factors. We also show that these structural and higher-order changes induced by the β3-subunit do not alter the degree of electrophysiological gating cooperativity between Nav1.5 α-subunits. Our data provide new insights into the role of the β3-subunit and the supramolecular organization of sodium channels, in an important model cell system that is widely used to study Nav channel behavior.
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Affiliation(s)
| | | | - Alexandra McStea
- Central Laser FacilityResearch Complex at HarwellScience and Technology Facilities CouncilRutherford Appleton LaboratoryOxfordUK
| | - Michael Hirsch
- Central Laser FacilityResearch Complex at HarwellScience and Technology Facilities CouncilRutherford Appleton LaboratoryOxfordUK
| | - Lin Wang
- Central Laser FacilityResearch Complex at HarwellScience and Technology Facilities CouncilRutherford Appleton LaboratoryOxfordUK
| | - Christopher J. Tynan
- Central Laser FacilityResearch Complex at HarwellScience and Technology Facilities CouncilRutherford Appleton LaboratoryOxfordUK
| | - Matthew W. Reed
- Department of Nuclear PhysicsResearch School of Physics and EngineeringAustralian National UniversityCanberrraACTAustralia
| | | | - Richard Butler
- Wellcome Trust/Cancer Research UK Gurdon InstituteUniversity of CambridgeCambridgeUK
| | | | - Marisa L. Martin-Fernandez
- Central Laser FacilityResearch Complex at HarwellScience and Technology Facilities CouncilRutherford Appleton LaboratoryOxfordUK
| | - Christopher L.‐H. Huang
- Deparment of BiochemistryUniversity of CambridgeCambridgeUK
- Department of Physiology, Development and NeuroscienceUniversity of CambridgeCambridgeUK
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16
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Chen JH, Blanpied TA, Tang AH. Quantification of trans-synaptic protein alignment: A data analysis case for single-molecule localization microscopy. Methods 2019; 174:72-80. [PMID: 31325491 DOI: 10.1016/j.ymeth.2019.07.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 06/14/2019] [Accepted: 07/16/2019] [Indexed: 12/13/2022] Open
Abstract
Nanoscale distribution of proteins and their relative positioning within a defined subcellular region are key to their physiological functions. Thanks to the super-resolution imaging methods, especially single-molecule localization microscopy (SMLM), mapping the three-dimensional distribution of multiple proteins has been easier and more efficient than ever. Nevertheless, in spite of the many tools available for efficient localization detection and image rendering, it has been a challenge to quantitatively analyze the 3D distribution and relative positioning of proteins in these SMLM data. Here, using heterogeneously distributed synaptic proteins as examples, we describe in detail a series of analytical methods including detection of nanoscale density clusters, quantification of the trans-synaptic alignment between these protein densities, and automatic en face projection and averaging. These analyses were performed within customized Matlab routines and we make the full scripts available. The concepts behind these analytical methods and the scripts can be adapted for quantitative analysis of spatial organization of other macromolecular complexes.
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Affiliation(s)
- Jia-Hui Chen
- CAS Key Laboratory of Brain Function and Disease and Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China
| | - Thomas A Blanpied
- Program in Neuroscience and Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Ai-Hui Tang
- CAS Key Laboratory of Brain Function and Disease and Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China.
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17
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Liu H, Ye Z, Wang X, Wei L, Xiao L. Molecular and living cell dynamic assays with optical microscopy imaging techniques. Analyst 2019; 144:859-871. [PMID: 30444498 DOI: 10.1039/c8an01420e] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Generally, the message elucidated by the conventional analytical methods overlooks the heterogeneity of single objects, where the behavior of individual molecules is shielded. With the advent of optical microscopy imaging techniques, it is possible to identify, visualize and track individual molecules or nanoparticles under a biological environment with high temporal and spatial resolution. In this work, we summarize the commonly adopted optical microscopy techniques for bio-analytical assays in living cells, including total internal reflection fluorescence microscopy (TIRFM), super-resolution optical microscopy (SRM), and dark-field optical microscopy (DFM). The basic principles of these methods and some recent interesting applications in molecular detection and single-particle tracking are introduced. Moreover, the development in high-dimensional optical microscopy to achieve three-dimensional (3-D) as well as sub-diffraction localization and tracking of biomolecules is also highlighted.
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Affiliation(s)
- Hua Liu
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, College of Chemistry, Nankai University, Tianjin, 300071, China.
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18
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Quantifying Protein Copy Number in Super Resolution Using an Imaging-Invariant Calibration. Biophys J 2019; 116:2195-2203. [PMID: 31103226 DOI: 10.1016/j.bpj.2019.04.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 04/20/2019] [Accepted: 04/25/2019] [Indexed: 01/28/2023] Open
Abstract
The use of super-resolution microscopy in recent years has revealed that proteins often form small assemblies inside cells and are organized in nanoclusters. However, determining the copy number of proteins within these nanoclusters constitutes a major challenge because of unknown labeling stoichiometries and complex fluorophore photophysics. We previously developed a DNA-origami-based calibration approach to extract protein copy number from super-resolution images. However, the applicability of this approach is limited by the fact that the calibration is dependent on the specific labeling and imaging conditions used in each experiment. Hence, the calibration must be repeated for each experimental condition, which is a formidable task. Here, using cells stably expressing dynein intermediate chain fused to green fluorescent protein (HeLa IC74 cells) as a reference sample, we demonstrate that the DNA-origami-based calibration data we previously generated can be extended to super-resolution images taken under different experimental conditions, enabling the quantification of any green-fluorescent-protein-fused protein of interest. To do so, we first quantified the copy number of dynein motors within nanoclusters in the cytosol and along the microtubules. Interestingly, this quantification showed that dynein motors form assemblies consisting of more than one motor, especially along microtubules. This quantification enabled us to use the HeLa IC74 cells as a reference sample to calibrate and quantify protein copy number independently of labeling and imaging conditions, dramatically improving the versatility and applicability of our approach.
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19
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Liew ATF, Foo YH, Gao Y, Zangoui P, Singh MK, Gulvady R, Kenney LJ. Single cell, super-resolution imaging reveals an acid pH-dependent conformational switch in SsrB regulates SPI-2. eLife 2019; 8:e45311. [PMID: 31033442 PMCID: PMC6557628 DOI: 10.7554/elife.45311] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/28/2019] [Indexed: 12/29/2022] Open
Abstract
After Salmonella is phagocytosed, it resides in an acidic vacuole. Its cytoplasm acidifies to pH 5.6; acidification activates pathogenicity island 2 (SPI-2). SPI-2 encodes a type three secretion system whose effectors modify the vacuole, driving endosomal tubulation. Using super-resolution imaging in single bacterial cells, we show that low pH induces expression of the SPI-2 SsrA/B signaling system. Single particle tracking, atomic force microscopy, and single molecule unzipping assays identified pH-dependent stimulation of DNA binding by SsrB. A so-called phosphomimetic form (D56E) was unable to bind to DNA in live cells. Acid-dependent DNA binding was not intrinsic to regulators, as PhoP and OmpR binding was not pH-sensitive. The low level of SPI-2 injectisomes observed in single cells is not due to fluctuating SsrB levels. This work highlights the surprising role that acid pH plays in virulence and intracellular lifestyles of Salmonella; modifying acid survival pathways represents a target for inhibiting Salmonella.
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Affiliation(s)
- Andrew Tze Fui Liew
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Yong Hwee Foo
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Yunfeng Gao
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Parisa Zangoui
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | | | - Ranjit Gulvady
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Linda J Kenney
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
- Biochemistry and Molecular BiologyUniversity of Texas Medical BranchGalvestonUnited States
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20
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Post RAJ, van der Zwaag D, Bet G, Wijnands SPW, Albertazzi L, Meijer EW, van der Hofstad RW. A stochastic view on surface inhomogeneity of nanoparticles. Nat Commun 2019; 10:1663. [PMID: 30971686 PMCID: PMC6458121 DOI: 10.1038/s41467-019-09595-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 03/19/2019] [Indexed: 01/16/2023] Open
Abstract
The interactions between and with nanostructures can only be fully understood when the functional group distribution on their surfaces can be quantified accurately. Here we apply a combination of direct stochastic optical reconstruction microscopy (dSTORM) imaging and probabilistic modelling to analyse molecular distributions on spherical nanoparticles. The properties of individual fluorophores are assessed and incorporated into a model for the dSTORM imaging process. Using this tailored model, overcounting artefacts are greatly reduced and the locations of dye labels can be accurately estimated, revealing their spatial distribution. We show that standard chemical protocols for dye attachment lead to inhomogeneous functionalization in the case of ubiquitous polystyrene nanoparticles. Moreover, we demonstrate that stochastic fluctuations result in large variability of the local group density between particles. These results cast doubt on the uniform surface coverage commonly assumed in the creation of amorphous functional nanoparticles and expose a striking difference between the average population and individual nanoparticle coverage.
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Affiliation(s)
- R A J Post
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - D van der Zwaag
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- DSM Coating Resins, P.O. Box 123, 5145 PE, Waalwijk, The Netherlands
| | - G Bet
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Mathematics and Computer Science 'Ulisse Dini', University of Florence, 50134, Florence, Italy
| | - S P W Wijnands
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - L Albertazzi
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and Technology, 08028, Barcelona, Spain
| | - E W Meijer
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
- Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
| | - R W van der Hofstad
- Institute of Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
- Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
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21
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Persson H, Potrzebowski W, Potrzebowska K, Svensson LM. Spatial mapping of affinity changes for the integrin LFA-1 during cell migration using clusters identified based on local density. JOURNAL OF BIOPHOTONICS 2019; 12:e201800080. [PMID: 30267470 DOI: 10.1002/jbio.201800080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 09/18/2018] [Indexed: 06/08/2023]
Abstract
Localization microscopy methods like Stochastic Optical Reconstruction Microscopy (STORM) are very well suited for exploring clustering of proteins, as the data inherently provide a list of molecular coordinates. Here we use state-of-art cluster analysis algorithms (DBSCAN) to explore the clustering behaviour of different affinity forms of the integrin LFA-1. It has been suggested that LFA-1 may form clusters, in order to increase the avidity to ICAM-1. However, this hypothesis still seems to be controversial. In this study, we found, variations in clustering behaviour among the different affinity forms of LFA-1 in migrating T-cells. We found that panLFA-1 is located in clusters throughout the polarised cell on ICAM-1, with an increased density of molecules and clusters in the mid area and rear of the cell, whereas the intermediate and high affinity form of LFA-1 showed an increased number in the mid area of a migrating cell and the high affinity form of LFA-1 in the front and rear. Together, these data suggest that, in addition to LFA-1 conformation, protein clustering might play a role in controlling cell-substrate adhesion on ICAM-1.By applying the cluster analysis algorithm DBSCAN to localization microscopy data, integrin clusters could be identified and different cluster parameters could be quantified.
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Affiliation(s)
- Henrik Persson
- Section of Immunology, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | | | - Katarzyna Potrzebowska
- Section of Immunology, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Lena M Svensson
- Section of Immunology, Department of Experimental Medical Science, Lund University, Lund, Sweden
- The School of Medical Sciences, Örebro University, Örebro, Sweden
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22
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Padmanabhan P, Bademosi AT, Kasula R, Lauwers E, Verstreken P, Meunier FA. Need for speed: Super-resolving the dynamic nanoclustering of syntaxin-1 at exocytic fusion sites. Neuropharmacology 2019; 169:107554. [PMID: 30826343 DOI: 10.1016/j.neuropharm.2019.02.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 02/21/2019] [Accepted: 02/27/2019] [Indexed: 01/08/2023]
Abstract
Communication between cells relies on regulated exocytosis, a multi-step process that involves the docking, priming and fusion of vesicles with the plasma membrane, culminating in the release of neurotransmitters and hormones. Key proteins and lipids involved in exocytosis are subjected to Brownian movement and constantly switch between distinct motion states which are governed by short-lived molecular interactions. Critical biochemical reactions between exocytic proteins that occur in the confinement of nanodomains underpin the precise sequence of priming steps which leads to the fusion of vesicles. The advent of super-resolution microscopy techniques has provided the means to visualize individual molecules on the plasma membrane with high spatiotemporal resolution in live cells. These techniques are revealing a highly dynamic nature of the nanoscale organization of the exocytic machinery. In this review, we focus on soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) syntaxin-1, which mediates vesicular fusion. Syntaxin-1 is highly mobile at the plasma membrane, and its inherent speed allows fast assembly and disassembly of syntaxin-1 nanoclusters which are associated with exocytosis. We reflect on recent studies which have revealed the mechanisms regulating syntaxin-1 nanoclustering on the plasma membrane and draw inferences on the effect of synaptic activity, phosphoinositides, N-ethylmaleimide-sensitive factor (NSF), α-soluble NSF attachment protein (α-SNAP) and SNARE complex assembly on the dynamic nanoscale organization of syntaxin-1. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Pranesh Padmanabhan
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Adekunle T Bademosi
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Ravikiran Kasula
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Elsa Lauwers
- VIB-KU Leuven Center for Brain & Disease Research, 3000 Leuven, Belgium; Department of Neurosciences and Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - Patrik Verstreken
- VIB-KU Leuven Center for Brain & Disease Research, 3000 Leuven, Belgium; Department of Neurosciences and Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia.
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23
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Gomes de Castro MA, Wildhagen H, Sograte-Idrissi S, Hitzing C, Binder M, Trepel M, Engels N, Opazo F. Differential organization of tonic and chronic B cell antigen receptors in the plasma membrane. Nat Commun 2019; 10:820. [PMID: 30778055 PMCID: PMC6379438 DOI: 10.1038/s41467-019-08677-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 01/24/2019] [Indexed: 11/09/2022] Open
Abstract
Stimulation of the B cell antigen receptor (BCR) triggers signaling pathways that promote the differentiation of B cells into plasma cells. Despite the pivotal function of BCR in B cell activation, the organization of the BCR on the surface of resting and antigen-activated B cells remains unclear. Here we show, using STED super-resolution microscopy, that IgM-containing BCRs exist predominantly as monomers and dimers in the plasma membrane of resting B cells, but form higher oligomeric clusters upon stimulation. By contrast, a chronic lymphocytic leukemia-derived BCR forms dimers and oligomers in the absence of a stimulus, but a single amino acid exchange reverts its organization to monomers in unstimulated B cells. Our super-resolution microscopy approach for quantitatively analyzing cell surface proteins may thus help reveal the nanoscale organization of immunoreceptors in various cell types.
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MESH Headings
- B-Lymphocytes/metabolism
- Burkitt Lymphoma/pathology
- Cell Line, Tumor
- Cell Membrane/metabolism
- Humans
- Immunoglobulin Fab Fragments/genetics
- Immunoglobulin Fab Fragments/metabolism
- Immunoglobulin M/metabolism
- Leukemia, Lymphocytic, Chronic, B-Cell/metabolism
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- Microscopy, Fluorescence/methods
- Protein Multimerization
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
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Affiliation(s)
- Maria Angela Gomes de Castro
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Hanna Wildhagen
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Shama Sograte-Idrissi
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, von-Siebold-Straße 3a, 37075, Göttingen, Germany
| | - Christoffer Hitzing
- Institute of Cellular and Molecular Immunology, University Medical Center Göttingen, Humboldtallee 34, 37073, Göttingen, Germany
| | - Mascha Binder
- Department of Oncology and Hematology, BMT with section Pneumology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany
| | - Martin Trepel
- Department of Oncology and Hematology, BMT with section Pneumology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany
- Department of Hematology and Oncology, Augsburg Medical Center, Stenglinstr. 2, 86156, Augsburg, Germany
| | - Niklas Engels
- Institute of Cellular and Molecular Immunology, University Medical Center Göttingen, Humboldtallee 34, 37073, Göttingen, Germany.
| | - Felipe Opazo
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
- Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, von-Siebold-Straße 3a, 37075, Göttingen, Germany.
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24
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Abstract
Super-resolution microscopy (SRM) can provide a window on the nanoscale events of virus replication. Here we describe a protocol for imaging hepatitis C virus-infected cells using localization SRM. We provide details on sample preparation, immunostaining, data collection, and super-resolution image reconstruction. We have made all efforts to generalize the protocol to make it accessible to all budding super-resolution microscopists.
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25
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Delcanale P, Miret-Ontiveros B, Arista-Romero M, Pujals S, Albertazzi L. Nanoscale Mapping Functional Sites on Nanoparticles by Points Accumulation for Imaging in Nanoscale Topography (PAINT). ACS NANO 2018; 12:7629-7637. [PMID: 30048592 DOI: 10.1021/acsnano.7b09063] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The ability of nanoparticles to selectively recognize a molecular target constitutes the key toward nanomedicine applications such as drug delivery and diagnostics. The activity of such devices is mediated by the presence of multiple copies of functional molecules on the nanostructure surface. Therefore, understanding the number and the distribution of nanoparticle functional groups is of utmost importance for the rational design of effective materials. Analytical methods are available, but to obtain quantitative information at the level of single particles and single functional sites, i. e., going beyond the ensemble, remains highly challenging. Here we introduce the use of an optical nanoscopy technique, DNA points accumulation for imaging in nanoscale topography (DNA-PAINT), to address this issue. Combining subdiffraction spatial resolution with molecular selectivity and sensitivity, DNA-PAINT provides both geometrical and functional information at the level of a single nanostructure. We show how DNA-PAINT can be used to image and quantify relevant functional proteins such as antibodies and streptavidin on nanoparticles and microparticles with nanometric accuracy in 3D and multiple colors. The generality and the applicability of our method without the need for fluorescent labeling hold great promise for the robust quantitative nanocharacterization of functional nanomaterials.
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Affiliation(s)
- Pietro Delcanale
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology , Baldiri Reixac 15-21 , 08028 Barcelona , Spain
| | - Bernat Miret-Ontiveros
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology , Baldiri Reixac 15-21 , 08028 Barcelona , Spain
| | - Maria Arista-Romero
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology , Baldiri Reixac 15-21 , 08028 Barcelona , Spain
| | - Silvia Pujals
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology , Baldiri Reixac 15-21 , 08028 Barcelona , Spain
| | - Lorenzo Albertazzi
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology , Baldiri Reixac 15-21 , 08028 Barcelona , Spain
- Department of Biomedical Engineering and Institute for Complex Molecular Systems (ICMS) , Eindhoven University of Technology , 5612AZ Eindhoven , The Netherlands
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26
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Bernhem K, Blom H, Brismar H. Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imaging. PLoS One 2018; 13:e0195825. [PMID: 29694368 PMCID: PMC5918999 DOI: 10.1371/journal.pone.0195825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 03/30/2018] [Indexed: 01/19/2023] Open
Abstract
Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the use of STORM and PALM microscopy to quantitatively monitor endogenous and exogenous protein expression. Through incorporation of an N-terminal hemagglutinin epitope to a mMaple3 fused Na,K-ATPase (α1 isoform), we analyze the spatial and quantitative changes of plasma membrane Na,K-ATPase localization during competitive transient expression. Quantification of plasma membrane protein density revealed a time dependent increase of Na,K-ATPase, but no increase in size of protein clusters. Results show that after 41h transfection, the total plasma membrane density of Na,K-ATPase increased by 63% while the endogenous contribution was reduced by 16%.
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Affiliation(s)
- Kristoffer Bernhem
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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27
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Grußmayer KS, Herten DP. Time-resolved molecule counting by photon statistics across the visible spectrum. Phys Chem Chem Phys 2018; 19:8962-8969. [PMID: 28300271 DOI: 10.1039/c7cp00363c] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In the past few years quantification of fluorescently labeled (bio-) molecules has become of increasing importance and several approaches have been developed to address this task. Counting by photon statistics measures the distribution of multiple photon detection events that carry information about the number and brightness of independently emitting fluorophores. The method enables absolute and non-destructive quantification, with the quality of estimates critically depending on the ability to accurately measure said photon statistics. Here, we present a combination of simulations and experiments that relate fundamental properties of fluorophores, i.e. their molecular brightness and photostability, to important experimental conditions, i.e. excitation power and acquisition time. Thereby, experimental settings and analysis parameters can be quantitatively evaluated, making counting by photon statistics a robust method for absolute counting of the number of emitters in a diffraction limited observation volume. We show that the time-resolution of counting varies with the fluorophore brightness and can be as fast as 10-100 ms. At the same time, the range of suitable fluorophores can be easily assessed. We evaluated the brightness and photostability of 16 organic dyes across the visible spectrum, providing information crucial for a range of single-molecule spectroscopy applications. This opens up exciting possibilities to analyze absolute stoichiometries in dynamic multi-component complexes.
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Affiliation(s)
- K S Grußmayer
- Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.
| | - D-P Herten
- Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.
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Bartle EI, Rao TC, Urner TM, Mattheyses AL. Bridging the gap: Super-resolution microscopy of epithelial cell junctions. Tissue Barriers 2018; 6:e1404189. [PMID: 29420122 PMCID: PMC5823550 DOI: 10.1080/21688370.2017.1404189] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/26/2017] [Accepted: 10/30/2017] [Indexed: 02/02/2023] Open
Abstract
Cell junctions are critical for cell adhesion and communication in epithelial tissues. It is evident that the cellular distribution, size, and architecture of cell junctions play a vital role in regulating function. These details of junction architecture have been challenging to elucidate in part due to the complexity and size of cell junctions. A major challenge in understanding these features is attaining high resolution spatial information with molecular specificity. Fluorescence microscopy allows localization of specific proteins to junctions, but with a resolution on the same scale as junction size, rendering internal protein organization unobtainable. Super-resolution microscopy provides a bridge between fluorescence microscopy and nanoscale approaches, utilizing fluorescent tags to reveal protein organization below the resolution limit. Here we provide a brief introduction to super-resolution microscopy and discuss novel findings into the organization, structure and function of epithelial cell junctions.
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Affiliation(s)
- Emily I. Bartle
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tejeshwar C. Rao
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tara M. Urner
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Alexa L. Mattheyses
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
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29
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Joensuu M, Martínez-Mármol R, Padmanabhan P, Glass NR, Durisic N, Pelekanos M, Mollazade M, Balistreri G, Amor R, Cooper-White JJ, Goodhill GJ, Meunier FA. Visualizing endocytic recycling and trafficking in live neurons by subdiffractional tracking of internalized molecules. Nat Protoc 2017; 12:2590-2622. [PMID: 29189775 DOI: 10.1038/nprot.2017.116] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Our understanding of endocytic pathway dynamics is restricted by the diffraction limit of light microscopy. Although super-resolution techniques can overcome this issue, highly crowded cellular environments, such as nerve terminals, can also dramatically limit the tracking of multiple endocytic vesicles such as synaptic vesicles (SVs), which in turn restricts the analytical dissection of their discrete diffusional and transport states. We recently introduced a pulse-chase technique for subdiffractional tracking of internalized molecules (sdTIM) that allows the visualization of fluorescently tagged molecules trapped in individual signaling endosomes and SVs in presynapses or axons with 30- to 50-nm localization precision. We originally developed this approach for tracking single molecules of botulinum neurotoxin type A, which undergoes activity-dependent internalization and retrograde transport in autophagosomes. This method was then adapted to localize the signaling endosomes containing cholera toxin subunit-B that undergo retrograde transport in axons and to track SVs in the crowded environment of hippocampal presynapses. We describe (i) the construction of a custom-made microfluidic device that enables control over neuronal orientation; (ii) the 3D printing of a perfusion system for sdTIM experiments performed on glass-bottom dishes; (iii) the dissection, culturing and transfection of hippocampal neurons in microfluidic devices; and (iv) guidance on how to perform the pulse-chase experiments and data analysis. In addition, we describe the use of single-molecule-tracking analytical tools to reveal the average and the heterogeneous single-molecule mobility behaviors. We also discuss alternative reagents and equipment that can, in principle, be used for sdTIM experiments and describe how to adapt sdTIM to image nanocluster formation and/or tubulation in early endosomes during sorting events. The procedures described in this protocol take ∼1 week.
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Affiliation(s)
- Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia.,Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Ramon Martínez-Mármol
- Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Pranesh Padmanabhan
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Nick R Glass
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Queensland, Australia
| | - Nela Durisic
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Matthew Pelekanos
- Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Mahdie Mollazade
- Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Giuseppe Balistreri
- Division of General Microbiology, Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Rumelo Amor
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Justin J Cooper-White
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Queensland, Australia.,Division of General Microbiology, Department of Biosciences, University of Helsinki, Helsinki, Finland.,School of Chemical Engineering, The University of Queensland, Brisbane, Queensland, Australia.,Materials Science and Engineering Division, CSIRO, Clayton, Victoria, Australia.,UQ Centre for Stem Cell Ageing and Regenerative Engineering, The University of Queensland, Brisbane, Queensland, Australia
| | - Geoffrey J Goodhill
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia.,School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
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30
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Thédié D, Berardozzi R, Adam V, Bourgeois D. Photoswitching of Green mEos2 by Intense 561 nm Light Perturbs Efficient Green-to-Red Photoconversion in Localization Microscopy. J Phys Chem Lett 2017; 8:4424-4430. [PMID: 28850784 DOI: 10.1021/acs.jpclett.7b01701] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Green-to-red photoconvertible fluorescent proteins (PCFPs) such as mEos2 and its derivatives are widely used in PhotoActivated Localization Microscopy (PALM). However, the complex photophysics of these genetically encoded markers complicates the quantitative analysis of PALM data. Here, we show that intense 561 nm light (∼1 kW/cm2) typically used to localize single red molecules considerably affects the green-state photophysics of mEos2 by populating at least two reversible dark states. These dark states retard green-to-red photoconversion through a shelving effect, although one of them is rapidly depopulated by 405 nm light illumination. Multiple mEos2 switching and irreversible photobleaching is thus induced by yellow/green and violet photons before green-to-red photoconversion occurs, contributing to explain the apparent limited signaling efficiency of this PCFP. Our data reveals that the photophysics of PCFPs of anthozoan origin is substantially more complex than previously thought, and suggests that intense 561 nm laser light should be used with care, notably for quantitative or fast PALM approaches.
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Affiliation(s)
- Daniel Thédié
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Romain Berardozzi
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Virgile Adam
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Dominique Bourgeois
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
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31
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Runa S, Lakadamyali M, Kemp ML, Payne CK. TiO 2 Nanoparticle-Induced Oxidation of the Plasma Membrane: Importance of the Protein Corona. J Phys Chem B 2017; 121:8619-8625. [PMID: 28844138 DOI: 10.1021/acs.jpcb.7b04208] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Titanium dioxide (TiO2) nanoparticles, used as pigments and photocatalysts, are widely present in modern society. Inhalation or ingestion of these nanoparticles can lead to cellular-level interactions. We examined the very first step in this cellular interaction, the effect of TiO2 nanoparticles on the lipids of the plasma membrane. Within 12 h of TiO2 nanoparticle exposure, the lipids of the plasma membrane were oxidized, determined with a malondialdehyde assay. Lipid peroxidation was inhibited by surface passivation of the TiO2 nanoparticles, incubation with an antioxidant (Trolox), and the presence of serum proteins in solution. Subsequent experiments determined that serum proteins adsorbed on the surface of the TiO2 nanoparticles, forming a protein corona, inhibit lipid peroxidation. Super-resolution fluorescence microscopy showed that these serum proteins were clustered on the nanoparticle surface. These protein clusters slow lipid peroxidation, but by 24 h, the level of lipid peroxidation is similar, independent of the protein corona or free serum proteins. Additionally, over 24 h, this corona of proteins was displaced from the nanoparticle surface by free proteins in solution. Overall, these experiments provide the first mechanistic investigation of plasma membrane oxidation by TiO2 nanoparticles, in the absence of UV light and as a function of the protein corona, approximating a physiological environment.
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Affiliation(s)
| | - Melike Lakadamyali
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona, Spain
| | - Melissa L Kemp
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States
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32
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Molecular Counting with Localization Microscopy: A Bayesian Estimate Based on Fluorophore Statistics. Biophys J 2017; 112:1777-1785. [PMID: 28494949 DOI: 10.1016/j.bpj.2017.03.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 03/16/2017] [Accepted: 03/23/2017] [Indexed: 12/15/2022] Open
Abstract
Superresolved localization microscopy has the potential to serve as an accurate, single-cell technique for counting the abundance of intracellular molecules. However, the stochastic blinking of single fluorophores can introduce large uncertainties into the final count. Here we provide a theoretical foundation for applying superresolved localization microscopy to the problem of molecular counting based on the distribution of blinking events from a single fluorophore. We also show that by redundantly tagging single molecules with multiple, blinking fluorophores, the accuracy of the technique can be enhanced by harnessing the central limit theorem. The coefficient of variation then, for the number of molecules M estimated from a given number of blinks B, scales like ∼1/Nl, where Nl is the mean number of labels on a target. As an example, we apply our theory to the challenging problem of quantifying the cell-to-cell variability of plasmid copy number in bacteria.
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33
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von Diezmann A, Shechtman Y, Moerner WE. Three-Dimensional Localization of Single Molecules for Super-Resolution Imaging and Single-Particle Tracking. Chem Rev 2017; 117:7244-7275. [PMID: 28151646 PMCID: PMC5471132 DOI: 10.1021/acs.chemrev.6b00629] [Citation(s) in RCA: 260] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Single-molecule super-resolution fluorescence microscopy and single-particle tracking are two imaging modalities that illuminate the properties of cells and materials on spatial scales down to tens of nanometers or with dynamical information about nanoscale particle motion in the millisecond range, respectively. These methods generally use wide-field microscopes and two-dimensional camera detectors to localize molecules to much higher precision than the diffraction limit. Given the limited total photons available from each single-molecule label, both modalities require careful mathematical analysis and image processing. Much more information can be obtained about the system under study by extending to three-dimensional (3D) single-molecule localization: without this capability, visualization of structures or motions extending in the axial direction can easily be missed or confused, compromising scientific understanding. A variety of methods for obtaining both 3D super-resolution images and 3D tracking information have been devised, each with their own strengths and weaknesses. These include imaging of multiple focal planes, point-spread-function engineering, and interferometric detection. These methods may be compared based on their ability to provide accurate and precise position information on single-molecule emitters with limited photons. To successfully apply and further develop these methods, it is essential to consider many practical concerns, including the effects of optical aberrations, field dependence in the imaging system, fluorophore labeling density, and registration between different color channels. Selected examples of 3D super-resolution imaging and tracking are described for illustration from a variety of biological contexts and with a variety of methods, demonstrating the power of 3D localization for understanding complex systems.
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Affiliation(s)
| | - Yoav Shechtman
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - W. E. Moerner
- Department of Chemistry, Stanford University, Stanford, CA 94305
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34
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Tools and limitations to study the molecular composition of synapses by fluorescence microscopy. Biochem J 2017; 473:3385-3399. [PMID: 27729584 DOI: 10.1042/bcj20160366] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 06/23/2016] [Indexed: 01/21/2023]
Abstract
The synapse is densely packed with proteins involved in various highly regulated processes. Synaptic protein copy numbers and their stoichiometric distribution have a drastic influence on neuronal integrity and function. Therefore, the molecular analysis of synapses is a key element to understand their architecture and function. The overall structure of the synapse has been revealed with an exquisite amount of details by electron microscopy. However, the molecular composition and the localization of proteins are more easily addressed with fluorescence imaging, especially with the improved resolution achieved by super-resolution microscopy techniques. Notably, the fast improvement of imaging instruments has not been reflected in the optimization of biological sample preparation. During recent years, large efforts have been made to generate affinity probes smaller than conventional antibodies adapted for fluorescent super-resolution imaging. In this review, we briefly discuss the current views on synaptic organization and necessary key technologies to progress in the understanding of synaptic physiology. We also highlight the challenges faced by current fluorescent super-resolution methods, and we describe the prerequisites for an ideal study of synaptic organization.
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35
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Ferguson S, Steyer AM, Mayhew TM, Schwab Y, Lucocq JM. Quantifying Golgi structure using EM: combining volume-SEM and stereology for higher throughput. Histochem Cell Biol 2017; 147:653-669. [PMID: 28429122 PMCID: PMC5429891 DOI: 10.1007/s00418-017-1564-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2017] [Indexed: 12/28/2022]
Abstract
Investigating organelles such as the Golgi complex depends increasingly on high-throughput quantitative morphological analyses from multiple experimental or genetic conditions. Light microscopy (LM) has been an effective tool for screening but fails to reveal fine details of Golgi structures such as vesicles, tubules and cisternae. Electron microscopy (EM) has sufficient resolution but traditional transmission EM (TEM) methods are slow and inefficient. Newer volume scanning EM (volume-SEM) methods now have the potential to speed up 3D analysis by automated sectioning and imaging. However, they produce large arrays of sections and/or images, which require labour-intensive 3D reconstruction for quantitation on limited cell numbers. Here, we show that the information storage, digital waste and workload involved in using volume-SEM can be reduced substantially using sampling-based stereology. Using the Golgi as an example, we describe how Golgi populations can be sensed quantitatively using single random slices and how accurate quantitative structural data on Golgi organelles of individual cells can be obtained using only 5–10 sections/images taken from a volume-SEM series (thereby sensing population parameters and cell–cell variability). The approach will be useful in techniques such as correlative LM and EM (CLEM) where small samples of cells are treated and where there may be variable responses. For Golgi study, we outline a series of stereological estimators that are suited to these analyses and suggest workflows, which have the potential to enhance the speed and relevance of data acquisition in volume-SEM.
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Affiliation(s)
- Sophie Ferguson
- Structural Cell Biology Group, School of Medicine, University of St Andrews, North Haugh, Fife, KY16 9TF, Scotland, UK
| | - Anna M Steyer
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Terry M Mayhew
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Yannick Schwab
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - John Milton Lucocq
- Structural Cell Biology Group, School of Medicine, University of St Andrews, North Haugh, Fife, KY16 9TF, Scotland, UK.
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Abstract
Super-resolution fluorescence imaging by photoactivation or photoswitching of single fluorophores and position determination (single-molecule localization microscopy, SMLM) provides microscopic images with subdiffraction spatial resolution. This technology has enabled new insights into how proteins are organized in a cellular context, with a spatial resolution approaching virtually the molecular level. A unique strength of SMLM is that it delivers molecule-resolved information, along with super-resolved images of cellular structures. This allows quantitative access to cellular structures, for example, how proteins are distributed and organized and how they interact with other biomolecules. Ultimately, it is even possible to determine protein numbers in cells and the number of subunits in a protein complex. SMLM thus has the potential to pave the way toward a better understanding of how cells function at the molecular level. In this review, we describe how SMLM has contributed new knowledge in eukaryotic biology, and we specifically focus on quantitative biological data extracted from SMLM images.
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Affiliation(s)
- Markus Sauer
- Department of Biotechnology & Biophysics, Julius-Maximilian-University of Würzburg , 97074 Würzburg, Germany
| | - Mike Heilemann
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt , 60438 Frankfurt, Germany
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37
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Lambert TJ, Waters JC. Navigating challenges in the application of superresolution microscopy. J Cell Biol 2017; 216:53-63. [PMID: 27920217 PMCID: PMC5223610 DOI: 10.1083/jcb.201610011] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 11/15/2016] [Accepted: 11/18/2016] [Indexed: 11/22/2022] Open
Abstract
In 2014, the Nobel Prize in Chemistry was awarded to three scientists who have made groundbreaking contributions to the field of superresolution (SR) microscopy (SRM). The first commercial SR microscope came to market a decade earlier, and many other commercial options have followed. As commercialization has lowered the barrier to using SRM and the awarding of the Nobel Prize has drawn attention to these methods, biologists have begun adopting SRM to address a wide range of questions in many types of specimens. There is no shortage of reviews on the fundamental principles of SRM and the remarkable achievements made with these methods. We approach SRM from another direction: we focus on the current practical limitations and compromises that must be made when designing an SRM experiment. We provide information and resources to help biologists navigate through common pitfalls in SRM specimen preparation and optimization of image acquisition as well as errors and artifacts that may compromise the reproducibility of SRM data.
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Affiliation(s)
- Talley J Lambert
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Jennifer C Waters
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
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38
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Munro ML, Jayasinghe I, Wang Q, Quick A, Wang W, Baddeley D, Wehrens XHT, Soeller C. Junctophilin-2 in the nanoscale organisation and functional signalling of ryanodine receptor clusters in cardiomyocytes. J Cell Sci 2016; 129:4388-4398. [PMID: 27802169 PMCID: PMC5201013 DOI: 10.1242/jcs.196873] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/14/2016] [Indexed: 11/20/2022] Open
Abstract
Signalling nanodomains requiring close contact between the plasma membrane and internal compartments, known as 'junctions', are fast communication hubs within excitable cells such as neurones and muscle. Here, we have examined two transgenic murine models probing the role of junctophilin-2, a membrane-tethering protein crucial for the formation and molecular organisation of sub-microscopic junctions in ventricular muscle cells of the heart. Quantitative single-molecule localisation microscopy showed that junctions in animals producing above-normal levels of junctophilin-2 were enlarged, allowing the re-organisation of the primary functional protein within it, the ryanodine receptor (RyR; in this paper, we use RyR to refer to the myocardial isoform RyR2). Although this change was associated with much enlarged RyR clusters that, due to their size, should be more excitable, functionally it caused a mild inhibition in the Ca2+ signalling output of the junctions (Ca2+ sparks). Analysis of the single-molecule densities of both RyR and junctophilin-2 revealed an ∼3-fold increase in the junctophilin-2 to RyR ratio. This molecular rearrangement is compatible with direct inhibition of RyR opening by junctophilin-2 to intrinsically stabilise the Ca2+ signalling properties of the junction and thus the contractile function of the cell.
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Affiliation(s)
- Michelle L Munro
- Department of Physiology, School of Medical Sciences, University of Auckland, 1023, New Zealand
| | - Izzy Jayasinghe
- School of Physics, University of Exeter, Exeter EX4 4QL, UK
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Qiongling Wang
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Ann Quick
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Wei Wang
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - David Baddeley
- Department of Cell Biology, Yale University, New Haven, CT 06520, USA
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Christian Soeller
- Department of Physiology, School of Medical Sciences, University of Auckland, 1023, New Zealand
- School of Physics, University of Exeter, Exeter EX4 4QL, UK
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39
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Laine RF, Kaminski Schierle GS, van de Linde S, Kaminski CF. From single-molecule spectroscopy to super-resolution imaging of the neuron: a review. Methods Appl Fluoresc 2016; 4:022004. [PMID: 28809165 PMCID: PMC5390958 DOI: 10.1088/2050-6120/4/2/022004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 05/09/2016] [Accepted: 05/19/2016] [Indexed: 12/03/2022]
Abstract
For more than 20 years, single-molecule spectroscopy has been providing invaluable insights into nature at the molecular level. The field has received a powerful boost with the development of the technique into super-resolution imaging methods, ca. 10 years ago, which overcome the limitations imposed by optical diffraction. Today, single molecule super-resolution imaging is routinely used in the study of macromolecular function and structure in the cell. Concomitantly, computational methods have been developed that provide information on numbers and positions of molecules at the nanometer-scale. In this overview, we outline the technical developments that have led to the emergence of localization microscopy techniques from single-molecule spectroscopy. We then provide a comprehensive review on the application of the technique in the field of neuroscience research.
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Affiliation(s)
- Romain F Laine
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
| | - Gabriele S Kaminski Schierle
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
| | - Sebastian van de Linde
- Department of Biotechnology and Biophysics, Julius-Maximilians-University, Am Hubland, D-97074 Würzburg, Germany
| | - Clemens F Kaminski
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
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40
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Sydor AM, Czymmek KJ, Puchner EM, Mennella V. Super-Resolution Microscopy: From Single Molecules to Supramolecular Assemblies. Trends Cell Biol 2015; 25:730-748. [DOI: 10.1016/j.tcb.2015.10.004] [Citation(s) in RCA: 185] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 10/03/2015] [Accepted: 10/05/2015] [Indexed: 11/25/2022]
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41
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Ziomkiewicz I, Sporring J, Pomorski TG, Schulz A. Novel approach to measure the size of plasma-membrane nanodomains in single molecule localization microscopy. Cytometry A 2015; 87:868-77. [PMID: 26109552 DOI: 10.1002/cyto.a.22708] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 05/14/2015] [Accepted: 05/26/2015] [Indexed: 01/20/2023]
Abstract
Many membrane proteins are not evenly distributed over the plasma membrane, but gathered in domains assumed to have a particular lipid composition. Using single molecule localization microscopy (SMLM) we have immunolocalized a glycosylphosphatidylinositol (GPI)-anchor protein that labels nanodomains in a specialized plant cell type, and compared the suitability of three methods to estimate their size. As conventional methods full width at half maximum (FWHM) and the full diameter (FWMin) of domains were used. A boundary detection method of the domain area (DA) was performed in order to take irregular shapes into account. In order to compare the influence of the chosen measurement methods, we have developed a MatLab program that allows for automated analysis of domain sizes from multiple SMLM images and provides the statistics of three key features of domains: FWHM and FWMin along their long and short axes as well as the DA, derived from the molecular density. Domains formed by the GPI-anchor protein are approximating elliptical shapes. Direct and indirect immunolabeling resulted in a statistically significant difference in apparent domain size, reflecting the fact that the secondary antibody molecules extend the uncertainty along the nanodomain border. FWMin values along the long and short axis give good estimates of regular, geometrically centred domain shapes, while the DA value matches regular as well as irregular shapes best, as derived from computer-generated, irregular point clusters.
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Affiliation(s)
- Iwona Ziomkiewicz
- Department of Plant and Environmental Sciences, University of Copenhagen, Denmark
| | - Jon Sporring
- Department of Computer Science, University of Copenhagen, Denmark
| | | | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Denmark
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Ras-GTP dimers activate the Mitogen-Activated Protein Kinase (MAPK) pathway. Proc Natl Acad Sci U S A 2015; 112:7996-8001. [PMID: 26080442 DOI: 10.1073/pnas.1509123112] [Citation(s) in RCA: 211] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rat sarcoma (Ras) GTPases regulate cell proliferation and survival through effector pathways including Raf-MAPK, and are the most frequently mutated genes in human cancer. Although it is well established that Ras activity requires binding to both GTP and the membrane, details of how Ras operates on the cell membrane to activate its effectors remain elusive. Efforts to target mutant Ras in human cancers to therapeutic benefit have also been largely unsuccessful. Here we show that Ras-GTP forms dimers to activate MAPK. We used quantitative photoactivated localization microscopy (PALM) to analyze the nanoscale spatial organization of PAmCherry1-tagged KRas 4B (hereafter referred to KRas) on the cell membrane under various signaling conditions. We found that at endogenous expression levels KRas forms dimers, and KRas(G12D), a mutant that constitutively binds GTP, activates MAPK. Overexpression of KRas leads to formation of higher order Ras nanoclusters. Conversely, at lower expression levels, KRas(G12D) is monomeric and activates MAPK only when artificially dimerized. Moreover, dimerization and signaling of KRas are both dependent on an intact CAAX (C, cysteine; A, aliphatic; X, any amino acid) motif that is also known to mediate membrane localization. These results reveal a new, dimerization-dependent signaling mechanism of Ras, and suggest Ras dimers as a potential therapeutic target in mutant Ras-driven tumors.
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Mennella V, Hanna R, Kim M. Subdiffraction resolution microscopy methods for analyzing centrosomes organization. Methods Cell Biol 2015; 129:129-152. [PMID: 26175437 DOI: 10.1016/bs.mcb.2015.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In this chapter, we describe the current methods of examining the structure of centrosomes by fluorescence subdiffraction microscopy. By using recently developed microscopy techniques, centrosomal proteins can now be examined in cells with a resolution of only a few nanometers, a level of molecular detail beyond the reach of traditional cell biology methods as confocal and widefield microscopy. We emphasize imaging by three-dimensional structured illumination microscopy, stochastic optical reconstruction microscopy, and quantitative approaches to image data analysis.
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Affiliation(s)
- Vito Mennella
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada; Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada; Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
| | - Rachel Hanna
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada; Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - Moshe Kim
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada; Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
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Ricci MA, Manzo C, García-Parajo MF, Lakadamyali M, Cosma MP. Chromatin fibers are formed by heterogeneous groups of nucleosomes in vivo. Cell 2015; 160:1145-58. [PMID: 25768910 DOI: 10.1016/j.cell.2015.01.054] [Citation(s) in RCA: 437] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 10/10/2014] [Accepted: 01/16/2015] [Indexed: 11/19/2022]
Abstract
Nucleosomes help structure chromosomes by compacting DNA into fibers. To gain insight into how nucleosomes are arranged in vivo, we combined quantitative super-resolution nanoscopy with computer simulations to visualize and count nucleosomes along the chromatin fiber in single nuclei. Nucleosomes assembled in heterogeneous groups of varying sizes, here termed "clutches," and these were interspersed with nucleosome-depleted regions. The median number of nucleosomes inside clutches and their compaction defined as nucleosome density were cell-type-specific. Ground-state pluripotent stem cells had, on average, less dense clutches containing fewer nucleosomes and clutch size strongly correlated with the pluripotency potential of induced pluripotent stem cells. RNA polymerase II preferentially associated with the smallest clutches while linker histone H1 and heterochromatin were enriched in the largest ones. Our results reveal how the chromatin fiber is formed at nanoscale level and link chromatin fiber architecture to stem cell state.
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Affiliation(s)
- Maria Aurelia Ricci
- Centre for Genomic Regulation (CRG), Dr Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Dr Aiguader 88, 08003 Barcelona, Spain
| | - Carlo Manzo
- ICFO, Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain
| | - María Filomena García-Parajo
- ICFO, Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - Melike Lakadamyali
- ICFO, Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain.
| | - Maria Pia Cosma
- Centre for Genomic Regulation (CRG), Dr Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Dr Aiguader 88, 08003 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain.
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Foo YH, Gao Y, Zhang H, Kenney LJ. Cytoplasmic sensing by the inner membrane histidine kinase EnvZ. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 118:119-29. [PMID: 25937465 DOI: 10.1016/j.pbiomolbio.2015.04.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 04/21/2015] [Accepted: 04/22/2015] [Indexed: 12/22/2022]
Abstract
Two-component regulatory systems drive signal transduction in bacteria. The simplest of these employs a membrane sensor kinase and a cytoplasmic response regulator. Environmental sensing is typically coupled to gene regulation. The histidine kinase EnvZ and its cognate response regulator OmpR regulate expression of outer membrane proteins (porins) in response to osmotic stress. We used hydrogen:deuterium exchange mass spectrometry to identify conformational changes in the cytoplasmic domain of EnvZ (EnvZc) that were associated with osmosensing. The osmosensor localized to a seventeen amino acid region of the four-helix bundle of the cytoplasmic domain and flanked the His(243) autophosphorylation site. High osmolality increased autophosphorylation of His(243), suggesting that these two events were linked. The transmembrane domains were not required for osmosensing, but mutants in the transmembrane domains altered EnvZ activity. A photoactivatable fusion protein composed of EnvZc fused to the fluorophore mEos2 (EnvZc-mEos2) was as capable as EnvZc in supporting OmpR-dependent ompF and ompC transcription. Over-expression of EnvZc reduced activity, indicating that the EnvZ/OmpR system is not robust. Our results support a model in which osmolytes stabilize helix one in the four-helix bundle of EnvZ by increased hydrogen bonding of the peptide backbone, increasing autophosphorylation and downstream signaling. The likelihood that additional histidine kinases use similar cytoplasmic sensing mechanisms is discussed.
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Affiliation(s)
- Yong Hwee Foo
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Yunfeng Gao
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Hongfang Zhang
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Linda J Kenney
- Mechanobiology Institute, National University of Singapore, Singapore; Jesse Brown Veterans Affairs Medical Center, Chicago, USA; University of Illinois-Chicago, USA.
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Lakadamyali M, Cosma MP. Advanced microscopy methods for visualizing chromatin structure. FEBS Lett 2015; 589:3023-30. [PMID: 25896023 DOI: 10.1016/j.febslet.2015.04.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 03/30/2015] [Accepted: 04/01/2015] [Indexed: 12/29/2022]
Abstract
In the recent years it has become clear that our genome is not randomly organized and its architecture is tightly linked to its function. While genomic studies have given much insight into genome organization, they mostly rely on averaging over large populations of cells, are not compatible with living cells and have limited resolution. For studying genome organization in single living cells, microscopy is indispensable. In addition, the visualization of biological structures helps to understand their function. Up to now, fluorescence microscopy has allowed us to probe the larger scale organization of chromosome territories in the micron length scales, however, the smaller length scales remained invisible due to the diffraction limited spatial resolution of fluorescence microscopy. Thanks to the advent of super-resolution microscopy methods, we are finally starting to be able to probe the nanoscale organization of chromatin in vivo and these methods have the potential to greatly advance our knowledge about chromatin structure and function relationship.
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Affiliation(s)
- Melike Lakadamyali
- ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Barcelona, Spain.
| | - Maria Pia Cosma
- Centre for Genomic Regulation (CRG), Dr. Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluis Companys 23, 08010 Barcelona, Spain.
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Johnson E, Seiradake E, Jones EY, Davis I, Grünewald K, Kaufmann R. Correlative in-resin super-resolution and electron microscopy using standard fluorescent proteins. Sci Rep 2015; 5:9583. [PMID: 25823571 PMCID: PMC4379466 DOI: 10.1038/srep09583] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 03/05/2015] [Indexed: 11/15/2022] Open
Abstract
We introduce a method for correlative in-resin super-resolution fluorescence and electron microscopy (EM) of biological structures in mammalian culture cells. Cryo-fixed resin embedded samples offer superior structural preservation, performing in-resin super-resolution, however, remains a challenge. We identified key aspects of the sample preparation procedure of high pressure freezing, freeze substitution and resin embedding that are critical for preserving fluorescence and photo-switching of standard fluorescent proteins, such as mGFP, mVenus and mRuby2. This enabled us to combine single molecule localization microscopy with transmission electron microscopy imaging of standard fluorescent proteins in cryo-fixed resin embedded cells. We achieved a structural resolution of 40-50 nm (~17 nm average single molecule localization accuracy) in the fluorescence images without the use of chemical fixation or special fluorophores. Using this approach enabled the correlation of fluorescently labeled structures to the ultrastructure in the same cell at the nanometer level and superior structural preservation.
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Affiliation(s)
- Errin Johnson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
| | - Elena Seiradake
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - E. Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Kay Grünewald
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - Rainer Kaufmann
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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Schubert V, Weisshart K. Abundance and distribution of RNA polymerase II in Arabidopsis interphase nuclei. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1687-98. [PMID: 25740920 PMCID: PMC4357323 DOI: 10.1093/jxb/erv091] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
RNA polymerase II (RNAPII) is responsible for the transcription of most eukaryotic protein-coding genes. Analysing the topological distribution and quantification of RNAPII can contribute to understanding its function in interphase nuclei. Previously it was shown that RNAPII molecules in plant nuclei form reticulate structures within euchromatin of differentiated Arabidopsis thaliana nuclei rather than being organized in distinct 'transcription factories' as observed in mammalian nuclei. Immunosignal intensity measurements based on specific antibody labelling in maximum intensity projections of image stacks acquired by structured illumination microscopy (SIM) suggested a relative proportional increase of RNAPII in endopolyploid plant nuclei. Here, photoactivated localization microscopy (PALM) was applied to determine the absolute number and distribution of active and inactive RNAPII molecules in differentiated A. thaliana nuclei. The proportional increase of RNAPII during endopolyploidization is confirmed, but it is also shown that PALM measurements are more reliable than those based on SIM in terms of quantification. The single molecule localization results show that, although RNAPII molecules are globally dispersed within plant euchromatin, they also aggregate within smaller distances as described for mammalian transcription factories.
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Affiliation(s)
- Veit Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, D-06466 Stadt Seeland, Germany
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Fornasiero EF, Opazo F. Super-resolution imaging for cell biologists: concepts, applications, current challenges and developments. Bioessays 2015; 37:436-51. [PMID: 25581819 DOI: 10.1002/bies.201400170] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The recent 2014 Nobel Prize in chemistry honored an era of discoveries and technical advancements in the field of super-resolution microscopy. However, the applications of diffraction-unlimited imaging in biology have a long road ahead and persistently engage scientists with new challenges. Some of the bottlenecks that restrain the dissemination of super-resolution techniques are tangible, and include the limited performance of affinity probes and the yet not capillary diffusion of imaging setups. Likewise, super-resolution microscopy has introduced new paradigms in the design of projects that require imaging with nanometer-resolution and in the interpretation of biological images. Besides structural or morphological characterization, super-resolution imaging is quickly expanding towards interaction mapping, multiple target detection and live imaging. Here we review the recent progress of biologists employing super-resolution imaging, some pitfalls, implications and new trends, with the purpose of animating the field and spurring future developments.
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Affiliation(s)
- Eugenio F Fornasiero
- STED Microscopy Group, European Neuroscience Institute, Göttingen, Germany; Department of Neuro- and Sensory-physiology, University of Göttingen, Göttingen, Germany
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50
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Fricke F, Dietz MS, Heilemann M. Single-Molecule Methods to Study Membrane Receptor Oligomerization. Chemphyschem 2014; 16:713-21. [DOI: 10.1002/cphc.201402765] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Indexed: 11/06/2022]
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