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Philipp N, Gratton E, Estrada LC. Measuring protein-membrane interaction through radial fluorescence correlation in 2 dimensions. Methods Appl Fluoresc 2023; 11:045009. [PMID: 37586380 DOI: 10.1088/2050-6120/acf118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/16/2023] [Indexed: 08/18/2023]
Abstract
The cell membrane has a fundamental role in the cell life cycle but there's still much to be learned about its heterogeneous structure, regulation, and protein interaction. Additionally, the protein-membrane interaction is often overlooked when studying specific protein dynamics. In this work, we present a new tool for a better understanding of protein dynamics and membrane function using live cells and fast non-invasive techniques without the need for individual particle tracking. To this end, we used the 2D-pair correlation function (2D-pCF) to study protein interactions across cellular membranes. We performed numerical simulations and confocal experiments using a GAP-mEGFP fusion construct known to interact with the plasmatic membrane. Our results demonstrate that based on a quantitative correlation analysis as the 2D pair correlation of the signal intensities, is possible to characterize protein-membrane interactions in live systems and real-time. Combining experimental and numerical results this work presents a new powerful approach to the study of the dynamic protein-membrane interaction.
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Affiliation(s)
- N Philipp
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Física. Buenos Aires, Argentina
- CONICET-Universidad de Buenos Aires, Instituto de Física de Buenos Aires (IFIBA). Buenos Aires, Argentina
| | - E Gratton
- Department of Biomedical Engineering, University of California, Irvine, CA, United States of America
| | - L C Estrada
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Física. Buenos Aires, Argentina
- CONICET-Universidad de Buenos Aires, Instituto de Física de Buenos Aires (IFIBA). Buenos Aires, Argentina
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2
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Dynamic Mode Decomposition of Fluorescence Loss in Photobleaching Microscopy Data for Model-Free Analysis of Protein Transport and Aggregation in Living Cells. SENSORS 2022; 22:s22134731. [PMID: 35808232 PMCID: PMC9269098 DOI: 10.3390/s22134731] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 06/16/2022] [Accepted: 06/20/2022] [Indexed: 02/05/2023]
Abstract
The phase separation and aggregation of proteins are hallmarks of many neurodegenerative diseases. These processes can be studied in living cells using fluorescent protein constructs and quantitative live-cell imaging techniques, such as fluorescence recovery after photobleaching (FRAP) or the related fluorescence loss in photobleaching (FLIP). While the acquisition of FLIP images is straightforward on most commercial confocal microscope systems, the analysis and computational modeling of such data is challenging. Here, a novel model-free method is presented, which resolves complex spatiotemporal fluorescence-loss kinetics based on dynamic-mode decomposition (DMD) of FLIP live-cell image sequences. It is shown that the DMD of synthetic and experimental FLIP image series (DMD-FLIP) allows for the unequivocal discrimination of subcellular compartments, such as nuclei, cytoplasm, and protein condensates based on their differing transport and therefore fluorescence loss kinetics. By decomposing fluorescence-loss kinetics into distinct dynamic modes, DMD-FLIP will enable researchers to study protein dynamics at each time scale individually. Furthermore, it is shown that DMD-FLIP is very efficient in denoising confocal time series data. Thus, DMD-FLIP is an easy-to-use method for the model-free detection of barriers to protein diffusion, of phase-separated protein assemblies, and of insoluble protein aggregates. It should, therefore, find wide application in the analysis of protein transport and aggregation, in particular in relation to neurodegenerative diseases and the formation of protein condensates in living cells.
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3
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Solano A, Lou J, Scipioni L, Gratton E, Hinde E. Radial pair correlation of molecular brightness fluctuations maps protein diffusion as a function of oligomeric state within live-cell nuclear architecture. Biophys J 2022; 121:2152-2167. [PMID: 35490296 PMCID: PMC9247470 DOI: 10.1016/j.bpj.2022.04.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 11/16/2021] [Accepted: 04/26/2022] [Indexed: 11/22/2022] Open
Abstract
Nuclear proteins can modulate their DNA binding activity and the exploration volume available during DNA target search by self-associating into higher-order oligomers. Directly tracking this process in the nucleoplasm of a living cell is, however, a complex task. Thus, here we present a microscopy method based on radial pair correlation of molecular brightness fluctuations (radial pCOMB) that can extract the mobility of a fluorescently tagged nuclear protein as a function of its oligomeric state and spatiotemporally map the anisotropy of this parameter with respect to nuclear architecture. By simply performing a rapid frame scan acquisition, radial pCOMB has the capacity to detect, within each pixel, protein oligomer formation and the size-dependent obstruction nuclear architecture imparts on this complex's transport across sub-micrometer distances. From application of radial pCOMB to an oligomeric transcription factor and DNA repair protein, we demonstrate that homo-oligomer formation differentially regulates chromatin accessibility and interaction with the DNA template.
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Affiliation(s)
- Ashleigh Solano
- School of Physics, University of Melbourne; Department of Biochemistry and Pharmacology, University of Melbourne
| | - Jieqiong Lou
- School of Physics, University of Melbourne; Department of Biochemistry and Pharmacology, University of Melbourne
| | - Lorenzo Scipioni
- Department of Biomedical Engineering, University of California, Irvine
| | - Enrico Gratton
- Department of Biomedical Engineering, University of California, Irvine.
| | - Elizabeth Hinde
- School of Physics, University of Melbourne; Department of Biochemistry and Pharmacology, University of Melbourne.
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4
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Fluorescence Fluctuation Spectroscopy enables quantification of potassium channel subunit dynamics and stoichiometry. Sci Rep 2021; 11:10719. [PMID: 34021177 PMCID: PMC8140153 DOI: 10.1038/s41598-021-90002-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 04/15/2021] [Indexed: 11/08/2022] Open
Abstract
Voltage-gated potassium (Kv) channels are a family of membrane proteins that facilitate K+ ion diffusion across the plasma membrane, regulating both resting and action potentials. Kv channels comprise four pore-forming α subunits, each with a voltage sensing domain, and they are regulated by interaction with β subunits such as those belonging to the KCNE family. Here we conducted a comprehensive biophysical characterization of stoichiometry and protein diffusion across the plasma membrane of the epithelial KCNQ1-KCNE2 complex, combining total internal reflection fluorescence (TIRF) microscopy and a series of complementary Fluorescence Fluctuation Spectroscopy (FFS) techniques. Using this approach, we found that KCNQ1-KCNE2 has a predominant 4:4 stoichiometry, while non-bound KCNE2 subunits are mostly present as dimers in the plasma membrane. At the same time, we identified unique spatio-temporal diffusion modalities and nano-environment organization for each channel subunit. These findings improve our understanding of KCNQ1-KCNE2 channel function and suggest strategies for elucidating the subunit stoichiometry and forces directing localization and diffusion of ion channel complexes in general.
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5
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Malacrida L, Hedde PN, Torrado B, Gratton E. Barriers to Diffusion in Cells: Visualization of Membraneless Particles in the Nucleus. BIOPHYSICIST (ROCKVILLE, MD.) 2020; 1:9. [PMID: 35415463 PMCID: PMC9000293 DOI: 10.35459/tbp.2019.000111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transient barriers are fundamental to cell supramolecular organization and assembly. Discontinuities between spaces can be generated by a physical barrier but also by thermodynamic barriers achieved by phase separation of molecules. However, because of the transient nature and the lack of a visible barrier, the existence of phase separation is difficult to demonstrate experimentally. We describe an approach based on the 2-dimensional pair correlation function (2D-pCF) analysis of the spatial connectivity in a cell. The educational aim of the article is to present both a model suitable for explaining diffusion barrier measurements to a broad range of courses and examples of biological situations. If there are no barriers to diffusion, particles could diffuse equally in all directions. In this situation the pair correlation function introduced in this article is independent of the direction and is uniform in all directions. However, in the presence of obstacles, the shape of the 2D-pCF is distorted to reflect how the obstacle position and orientation change the flow of molecules. In the example shown in this article, measurements of diffusion of enhanced green fluorescent protein moving in live cells show the lack of connectivity at the nucleolus surface for shorter distances. We also observe a gradual increase in the connectivity for longer distances or times, presumably because of molecular trajectories around the nucleolus.
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Affiliation(s)
- Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
- Unidad de Microscopia Avanzada y Bifotónica, Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo, Uruguay
| | - Per Niklas Hedde
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
| | - Belen Torrado
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
- Laboratory of Human Molecular Genetics, Institut Pasteur de Montevideo, Uruguay
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
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6
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Back to the Future: Genetically Encoded Fluorescent Proteins as Inert Tracers of the Intracellular Environment. Int J Mol Sci 2020; 21:ijms21114164. [PMID: 32545175 PMCID: PMC7312867 DOI: 10.3390/ijms21114164] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/09/2020] [Accepted: 06/09/2020] [Indexed: 01/08/2023] Open
Abstract
Over the past decades, the discovery and development of genetically encoded fluorescent proteins (FPs) has brought a revolution into our ability to study biologic phenomena directly within living matter. First, FPs enabled fluorescence-labeling of a variety of molecules of interest to study their localization, interactions and dynamic behavior at various scales-from cells to whole organisms/animals. Then, rationally engineered FP-based sensors facilitated the measurement of physicochemical parameters of living matter-especially at the intracellular level, such as ion concentration, temperature, viscosity, pressure, etc. In addition, FPs were exploited as inert tracers of the intracellular environment in which they are expressed. This oft-neglected role is made possible by two distinctive features of FPs: (i) the quite null, unspecific interactions of their characteristic β-barrel structure with the molecular components of the cellular environment; and (ii) their compatibility with the use of time-resolved fluorescence-based optical microscopy techniques. This review seeks to highlight the potential of such unique combinations of properties and report on the most significative and original applications (and related advancements of knowledge) produced to date. It is envisioned that the use of FPs as inert tracers of living matter structural organization holds a potential for several lines of further development in the next future, discussed in the last section of the review, which in turn can lead to new breakthroughs in bioimaging.
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7
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Single-molecule displacement mapping unveils nanoscale heterogeneities in intracellular diffusivity. Nat Methods 2020; 17:524-530. [PMID: 32203387 PMCID: PMC7205592 DOI: 10.1038/s41592-020-0793-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 02/14/2020] [Indexed: 11/08/2022]
Abstract
Intracellular diffusion underlies vital cellular processes. However, it remains difficult to elucidate how an unbound protein diffuses inside the cell with good spatial resolution and sensitivity. Here we introduce single-molecule displacement/diffusivity mapping (SMdM), a super-resolution strategy that enables the nanoscale mapping of intracellular diffusivity through local statistics of the instantaneous displacements of freely diffusing single molecules. We thus show that the diffusion of an average-sized protein in the mammalian cytoplasm and nucleus is spatially heterogeneous at the nanoscale, and that variations in local diffusivity correlate with the ultrastructure of the actin cytoskeleton and the organization of the genome, respectively. SMdM of differently charged proteins further unveils that the possession of positive, but not negative, net charges drastically impedes diffusion, and that the rate is determined by the specific subcellular environments. We thus unveil rich heterogeneities and charge effects in intracellular diffusion at the nanoscale.
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8
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Fluorescence fluctuation spectroscopy: an invaluable microscopy tool for uncovering the biophysical rules for navigating the nuclear landscape. Biochem Soc Trans 2019; 47:1117-1129. [DOI: 10.1042/bst20180604] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 11/17/2022]
Abstract
Abstract
Nuclear architecture is fundamental to the manner by which molecules traverse the nucleus. The nucleoplasm is a crowded environment where dynamic rearrangements in local chromatin compaction locally redefine the space accessible toward nuclear protein diffusion. Here, we review a suite of methods based on fluorescence fluctuation spectroscopy (FFS) and how they have been employed to interrogate chromatin organization, as well as the impact this structural framework has on nuclear protein target search. From first focusing on a set of studies that apply FFS to an inert fluorescent tracer diffusing inside the nucleus of a living cell, we demonstrate the capacity of this technology to measure the accessibility of the nucleoplasm. Then with a baseline understanding of the exploration volume available to nuclear proteins during target search, we review direct applications of FFS to fluorescently labeled transcription factors (TFs). FFS can detect changes in TF mobility due to DNA binding, as well as the formation of TF complexes via changes in brightness due to oligomerization. Collectively, we find that FFS-based methods can uncover how nuclear proteins in general navigate the nuclear landscape.
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9
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Phasor histone FLIM-FRET microscopy quantifies spatiotemporal rearrangement of chromatin architecture during the DNA damage response. Proc Natl Acad Sci U S A 2019; 116:7323-7332. [PMID: 30918123 PMCID: PMC6462080 DOI: 10.1073/pnas.1814965116] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To investigate how chromatin architecture is spatiotemporally organized at a double-strand break (DSB) repair locus, we established a biophysical method to quantify chromatin compaction at the nucleosome level during the DNA damage response (DDR). The method is based on phasor image-correlation spectroscopy of histone fluorescence lifetime imaging microscopy (FLIM)-Förster resonance energy transfer (FRET) microscopy data acquired in live cells coexpressing H2B-eGFP and H2B-mCherry. This multiplexed approach generates spatiotemporal maps of nuclear-wide chromatin compaction that, when coupled with laser microirradiation-induced DSBs, quantify the size, stability, and spacing between compact chromatin foci throughout the DDR. Using this technology, we identify that ataxia-telangiectasia mutated (ATM) and RNF8 regulate rapid chromatin decompaction at DSBs and formation of compact chromatin foci surrounding the repair locus. This chromatin architecture serves to demarcate the repair locus from the surrounding nuclear environment and modulate 53BP1 mobility.
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10
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Scipioni L, Lanzanó L, Diaspro A, Gratton E. Comprehensive correlation analysis for super-resolution dynamic fingerprinting of cellular compartments using the Zeiss Airyscan detector. Nat Commun 2018; 9:5120. [PMID: 30504919 PMCID: PMC6269422 DOI: 10.1038/s41467-018-07513-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/29/2018] [Indexed: 11/08/2022] Open
Abstract
The availability of the Airyscan detector in the Zeiss LSM 880 has made possible the development of a new concept in fluctuation correlation spectroscopy using super-resolution. The Airyscan unit acquires data simultaneously on 32 detectors arranged in a hexagonal array. This detector opens up the possibility to use fluctuation methods based on time correlation at single points or at a number of points simultaneously, as well as methods based on spatial correlation in the area covered by the detector. Given the frame rate of this detector, millions of frames can be acquired in seconds, providing a robust statistical basis for fluctuation data. We apply the comprehensive analysis to the molecular fluctuations of free GFP diffusing in live cells at different subcellular compartments to show that at the nanoscale different cell environments can be distinguished by the comprehensive fluctuation analysis.
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Affiliation(s)
- L Scipioni
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA
| | - L Lanzanó
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - A Diaspro
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
- Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - E Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA.
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11
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Schneider F, Waithe D, Galiani S, Bernardino de la Serna J, Sezgin E, Eggeling C. Nanoscale Spatiotemporal Diffusion Modes Measured by Simultaneous Confocal and Stimulated Emission Depletion Nanoscopy Imaging. NANO LETTERS 2018; 18:4233-4240. [PMID: 29893574 PMCID: PMC6047073 DOI: 10.1021/acs.nanolett.8b01190] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 06/05/2018] [Indexed: 05/25/2023]
Abstract
The diffusion dynamics in the cellular plasma membrane provide crucial insights into molecular interactions, organization, and bioactivity. Beam-scanning fluorescence correlation spectroscopy combined with super-resolution stimulated emission depletion nanoscopy (scanning STED-FCS) measures such dynamics with high spatial and temporal resolution. It reveals nanoscale diffusion characteristics by measuring the molecular diffusion in conventional confocal mode and super-resolved STED mode sequentially for each pixel along the scanned line. However, to directly link the spatial and the temporal information, a method that simultaneously measures the diffusion in confocal and STED modes is needed. Here, to overcome this problem, we establish an advanced STED-FCS measurement method, line interleaved excitation scanning STED-FCS (LIESS-FCS), that discloses the molecular diffusion modes at different spatial positions with a single measurement. It relies on fast beam-scanning along a line with alternating laser illumination that yields, for each pixel, the apparent diffusion coefficients for two different observation spot sizes (conventional confocal and super-resolved STED). We demonstrate the potential of the LIESS-FCS approach with simulations and experiments on lipid diffusion in model and live cell plasma membranes. We also apply LIESS-FCS to investigate the spatiotemporal organization of glycosylphosphatidylinositol-anchored proteins in the plasma membrane of live cells, which, interestingly, show multiple diffusion modes at different spatial positions.
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Affiliation(s)
- Falk Schneider
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
| | - Dominic Waithe
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
| | - Silvia Galiani
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
| | - Jorge Bernardino de la Serna
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
- Research
Complex at Harwell, Central Laser Facility, Rutherford Appleton Laboratory
Science, Technology Facilities Council, Harwell-Oxford, Didcot OX11 0FA, United Kingdom
| | - Erdinc Sezgin
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
| | - Christian Eggeling
- MRC
Human Immunology Unit and Wolfson Imaging Centre Oxford Weatherall Institute
of Molecular Medicine, University of Oxford, Headley Way Oxford, OX3 9DS United
Kingdom
- Institute
of Applied Optics, Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743 Jena, Germany
- Leibniz
Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
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12
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Malacrida L, Rao E, Gratton E. Comparison between iMSD and 2D-pCF analysis for molecular motion studies on in vivo cells: The case of the epidermal growth factor receptor. Methods 2018; 140-141:74-84. [PMID: 29501424 DOI: 10.1016/j.ymeth.2018.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 01/16/2018] [Accepted: 01/22/2018] [Indexed: 11/20/2022] Open
Abstract
Image correlation analysis has evolved to become a valuable method of analysis of the diffusional motion of molecules in every points of a live cell. Here we compare the iMSD and the 2D-pCF approaches that provide complementary information. The iMSD method provides the law of diffusion and it requires spatial averaging over a small region of the cell. The 2D-pCF does not require spatial averaging and it gives information about obstacles for diffusion at pixel resolution. We show the analysis of the same set of data by the two methods to emphasize that both methods could be needed to have a comprehensive understanding of the molecular diffusional flow in a live cell.
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Affiliation(s)
- Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA; Área de Investigación Respiratoria, Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay
| | - Estella Rao
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA; Dipartimento di Fisica e Chimica, Università di Palermo, Italy
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA.
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13
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Viral highway to nucleus exposed by image correlation analyses. Sci Rep 2018; 8:1152. [PMID: 29348472 PMCID: PMC5773500 DOI: 10.1038/s41598-018-19582-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 01/04/2018] [Indexed: 01/26/2023] Open
Abstract
Parvoviral genome translocation from the plasma membrane into the nucleus is a coordinated multistep process mediated by capsid proteins. We used fast confocal microscopy line scan imaging combined with image correlation methods including auto-, pair- and cross-correlation, and number and brightness analysis, to study the parvovirus entry pathway at the single-particle level in living cells. Our results show that the endosome-associated movement of virus particles fluctuates from fast to slow. Fast transit of single cytoplasmic capsids to the nuclear envelope is followed by slow movement of capsids and fast diffusion of capsid fragments in the nucleoplasm. The unique combination of image analyses allowed us to follow the fate of intracellular single virus particles and their interactions with importin β revealing previously unknown dynamics of the entry pathway.
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14
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Malacrida L, Hedde PN, Ranjit S, Cardarelli F, Gratton E. Visualization of barriers and obstacles to molecular diffusion in live cells by spatial pair-cross-correlation in two dimensions. BIOMEDICAL OPTICS EXPRESS 2018; 9:303-321. [PMID: 29359105 PMCID: PMC5772584 DOI: 10.1364/boe.9.000303] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 12/09/2017] [Accepted: 12/11/2017] [Indexed: 05/09/2023]
Abstract
Despite recent advances in optical super-resolution, we lack a method that can visualize the path followed by diffusing molecules in the cytoplasm or in the nucleus of cells. Fluorescence correlation spectroscopy (FCS) provides molecular dynamics at the single molecule level by averaging the behavior of many molecules over time at a single spot, thus achieving very good statistics but at only one point in the cell. Earlier image-based methods including raster-scan and spatiotemporal image correlation need spatial averaging over relatively large areas, thus compromising spatial resolution. Here, we use spatial pair-cross-correlation in two dimensions (2D-pCF) to obtain relatively high resolution images of molecular diffusion dynamics and transport in live cells. The 2D-pCF method measures the time for a particle to go from one location to another by cross-correlating the intensity fluctuations at specific points in an image. Hence, a visual map of the average path followed by molecules is created.
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Affiliation(s)
- Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
- Área de Investigación Respiratoria, Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay
- LM and PNH contributed equally to this work
| | - Per Niklas Hedde
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
- LM and PNH contributed equally to this work
| | - Suman Ranjit
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
| | - Francesco Cardarelli
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
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15
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Charalambous C, Muñoz-Gil G, Celi A, Garcia-Parajo MF, Lewenstein M, Manzo C, García-March MA. Nonergodic subdiffusion from transient interactions with heterogeneous partners. Phys Rev E 2017; 95:032403. [PMID: 28415278 DOI: 10.1103/physreve.95.032403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 06/07/2023]
Abstract
Spatiotemporal disorder has been recently associated to the occurrence of anomalous nonergodic diffusion of molecular components in biological systems, but the underlying microscopic mechanism is still unclear. We introduce a model in which a particle performs continuous Brownian motion with changes of diffusion coefficients induced by transient molecular interactions with diffusive binding partners. In spite of the exponential distribution of waiting times, the model shows subdiffusion and nonergodicity similar to the heavy-tailed continuous time random walk. The dependence of these properties on the density of binding partners is analyzed and discussed. Our work provides an experimentally testable microscopic model to investigate the nature of nonergodicity in disordered media.
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Affiliation(s)
- C Charalambous
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
| | - G Muñoz-Gil
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
| | - A Celi
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
| | - M F Garcia-Parajo
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
- ICREA - Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - M Lewenstein
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
- ICREA - Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - C Manzo
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
- Universitat de Vic - Universitat Central de Catalunya (UVic-UCC), C. de la Laura, 13, 08500 Vic, Spain
| | - M A García-March
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
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Gaus K. Biologists Wanted: New Fluorescence Fluctuation Tools for Cell Biology. Biophys J 2016; 111:677-678. [PMID: 27558711 DOI: 10.1016/j.bpj.2016.07.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 07/07/2016] [Accepted: 07/11/2016] [Indexed: 11/28/2022] Open
Affiliation(s)
- Katharina Gaus
- European Molecular Biology Laboratory Australia Node in Single Molecule Science, School of Medical Sciences, Sydney, Australia; Australian Research Council Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, Australia.
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