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Talbi N, Fokkens L, Audran C, Petit‐Houdenot Y, Pouzet C, Blaise F, Gay EJ, Rouxel T, Balesdent M, Rep M, Fudal I. The neighbouring genes AvrLm10A and AvrLm10B are part of a large multigene family of cooperating effector genes conserved in Dothideomycetes and Sordariomycetes. MOLECULAR PLANT PATHOLOGY 2023; 24:914-931. [PMID: 37128172 PMCID: PMC10346447 DOI: 10.1111/mpp.13338] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 03/22/2023] [Accepted: 03/26/2023] [Indexed: 05/03/2023]
Abstract
Fungal effectors (small-secreted proteins) have long been considered as species or even subpopulation-specific. The increasing availability of high-quality fungal genomes and annotations has allowed the identification of trans-species or trans-genera families of effectors. Two avirulence effectors, AvrLm10A and AvrLm10B, of Leptosphaeria maculans, the fungus causing stem canker of oilseed rape, are members of such a large family of effectors. AvrLm10A and AvrLm10B are neighbouring genes, organized in divergent transcriptional orientation. Sequence searches within the L. maculans genome showed that AvrLm10A/AvrLm10B belong to a multigene family comprising five pairs of genes with a similar tail-to-tail organization. The two genes, in a pair, always had the same expression pattern and two expression profiles were distinguished, associated with the biotrophic colonization of cotyledons and/or petioles and stems. Of the two protein pairs further investigated, AvrLm10A_like1/AvrLm10B_like1 and AvrLm10A_like2/AvrLm10B_like2, the second one had the ability to physically interact, similarly to what was previously described for the AvrLm10A/AvrLm10B pair, and cross-interactions were also detected for two pairs. AvrLm10A homologues were identified in more than 30 Dothideomycete and Sordariomycete plant-pathogenic fungi. One of them, SIX5, is an effector from Fusarium oxysporum f. sp. lycopersici physically interacting with the avirulence effector Avr2. We found that AvrLm10A/SIX5 homologues were associated with at least eight distinct putative effector families, suggesting that AvrLm10A/SIX5 is able to cooperate with different effectors. These results point to a general role of the AvrLm10A/SIX5 proteins as "cooperating proteins", able to interact with diverse families of effectors whose encoding gene is co-regulated with the neighbouring AvrLm10A homologue.
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Affiliation(s)
- Nacera Talbi
- BIOGER, INRAEUniversité Paris‐SaclayPalaiseauFrance
| | - Like Fokkens
- Molecular Plant PathologyUniversity of AmsterdamAmsterdamNetherlands
- Present address:
Laboratory of PhytopathologyWageningen University and ResearchWageningenNetherlands
| | - Corinne Audran
- UMR LIPMEUniversité de Toulouse, INRAE, CNRSCastanet‐TolosanFrance
| | | | - Cécile Pouzet
- FRAIB‐TRI Imaging Platform Facilities, FR AIBUniversité de Toulouse, CNRSCastanet‐TolosanFrance
| | | | - Elise J. Gay
- BIOGER, INRAEUniversité Paris‐SaclayPalaiseauFrance
| | | | | | - Martijn Rep
- Molecular Plant PathologyUniversity of AmsterdamAmsterdamNetherlands
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Comprehensive Investigation of Parameters Influencing Fluorescence Lifetime Imaging Microscopy in Frequency- and Time-Domain Illustrated by Phasor Plot Analysis. Int J Mol Sci 2022; 23:ijms232415885. [PMID: 36555522 PMCID: PMC9781030 DOI: 10.3390/ijms232415885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022] Open
Abstract
Having access to fluorescence lifetime, researchers can reveal in-depth details about the microenvironment as well as the physico-chemical state of the molecule under investigation. However, the high number of influencing factors might be an explanation for the strongly deviating values of fluorescent lifetimes for the same fluorophore reported in the literature. This could be the reason for the impression that inconsistent results are obtained depending on which detection and excitation scheme is used. To clarify this controversy, the two most common techniques for measuring fluorescence lifetimes in the time-domain and in the frequency-domain were implemented in one single microscopy setup and applied to a variety of fluorophores under different environmental conditions such as pH-value, temperature, solvent polarity, etc., along with distinct state forms that depend, for example, on the concentration. From a vast amount of measurement results, both setup- and sample-dependent parameters were extracted and represented using a single display form, the phasor-plot. The measurements showed consistent results between the two techniques and revealed which of the tested parameters has the strongest influence on the fluorescence lifetime. In addition, quantitative guidance as to which technique is most suitable for which research task and how to perform the experiment properly to obtain consistent fluorescence lifetimes is discussed.
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Valdez S, Robertson M, Qiang Z. Fluorescence Resonance Energy Transfer Measurements in Polymer Science: A Review. Macromol Rapid Commun 2022; 43:e2200421. [PMID: 35689335 DOI: 10.1002/marc.202200421] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 06/06/2022] [Indexed: 12/27/2022]
Abstract
Fluorescence resonance energy transfer (FRET) is a non-invasive characterization method for studying molecular structures and dynamics, providing high spatial resolution at nanometer scale. Over the past decades, FRET-based measurements are developed and widely implemented in synthetic polymer systems for understanding and detecting a variety of nanoscale phenomena, enabling significant advances in polymer science. In this review, the basic principles of fluorescence and FRET are briefly discussed. Several representative research areas are highlighted, where FRET spectroscopy and imaging can be employed to reveal polymer morphology and kinetics. These examples include understanding polymer micelle formation and stability, detecting guest molecule release from polymer host, characterizing supramolecular assembly, imaging composite interfaces, and determining polymer chain conformations and their diffusion kinetics. Finally, a perspective on the opportunities of FRET-based measurements is provided for further allowing their greater contributions in this exciting area.
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Affiliation(s)
- Sara Valdez
- School of Polymer Science and Engineering, University of Southern Mississippi, Hattiesburg, MS, 39406, USA
| | - Mark Robertson
- School of Polymer Science and Engineering, University of Southern Mississippi, Hattiesburg, MS, 39406, USA
| | - Zhe Qiang
- School of Polymer Science and Engineering, University of Southern Mississippi, Hattiesburg, MS, 39406, USA
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4
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Héliot L, Leray A. Simple phasor-based deep neural network for fluorescence lifetime imaging microscopy. Sci Rep 2021; 11:23858. [PMID: 34903737 PMCID: PMC8668934 DOI: 10.1038/s41598-021-03060-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 11/23/2021] [Indexed: 12/29/2022] Open
Abstract
Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to probe the molecular environment of fluorophores. The analysis of FLIM images is usually performed with time consuming fitting methods. For accelerating this analysis, sophisticated deep learning architectures based on convolutional neural networks have been developed for restrained lifetime ranges but they require long training time. In this work, we present a simple neural network formed only with fully connected layers able to analyze fluorescence lifetime images. It is based on the reduction of high dimensional fluorescence intensity temporal decays into four parameters which are the phasor coordinates, the mean and amplitude-weighted lifetimes. This network called Phasor-Net has been applied for a time domain FLIM system excited with an 80 MHz laser repetition frequency, with negligible jitter and afterpulsing. Due to the restricted time interval of 12.5 ns, the training range of the lifetimes was limited between 0.2 and 3.0 ns; and the total photon number was lower than 106, as encountered in live cell imaging. From simulated biexponential decays, we demonstrate that Phasor-Net is more precise and less biased than standard fitting methods. We demonstrate also that this simple architecture gives almost comparable performance than those obtained from more sophisticated networks but with a faster training process (15 min instead of 30 min). We finally apply successfully our method to determine biexponential decays parameters for FLIM experiments in living cells expressing EGFP linked to mCherry and fused to a plasma membrane protein.
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Affiliation(s)
- Laurent Héliot
- PhLAM Laboratoire de Physique Des Lasers, Atomes Et Molécules, UMR 8523, CNRS, University of Lille, Lille, France.
| | - Aymeric Leray
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303, CNRS, Université de Bourgogne Franche-Comté, Dijon, France.
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High-speed compressed-sensing fluorescence lifetime imaging microscopy of live cells. Proc Natl Acad Sci U S A 2021; 118:2004176118. [PMID: 33431663 DOI: 10.1073/pnas.2004176118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We present high-resolution, high-speed fluorescence lifetime imaging microscopy (FLIM) of live cells based on a compressed sensing scheme. By leveraging the compressibility of biological scenes in a specific domain, we simultaneously record the time-lapse fluorescence decay upon pulsed laser excitation within a large field of view. The resultant system, referred to as compressed FLIM, can acquire a widefield fluorescence lifetime image within a single camera exposure, eliminating the motion artifact and minimizing the photobleaching and phototoxicity. The imaging speed, limited only by the readout speed of the camera, is up to 100 Hz. We demonstrated the utility of compressed FLIM in imaging various transient dynamics at the microscopic scale.
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Liput DJ, Nguyen TA, Augustin SM, Lee JO, Vogel SS. A Guide to Fluorescence Lifetime Microscopy and Förster's Resonance Energy Transfer in Neuroscience. CURRENT PROTOCOLS IN NEUROSCIENCE 2020; 94:e108. [PMID: 33232577 PMCID: PMC8274369 DOI: 10.1002/cpns.108] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Fluorescence lifetime microscopy (FLIM) and Förster's resonance energy transfer (FRET) are advanced optical tools that neuroscientists can employ to interrogate the structure and function of complex biological systems in vitro and in vivo using light. In neurobiology they are primarily used to study protein-protein interactions, to study conformational changes in protein complexes, and to monitor genetically encoded FRET-based biosensors. These methods are ideally suited to optically monitor changes in neurons that are triggered optogenetically. Utilization of this technique by neuroscientists has been limited, since a broad understanding of FLIM and FRET requires familiarity with the interactions of light and matter on a quantum mechanical level, and because the ultra-fast instrumentation used to measure fluorescent lifetimes and resonance energy transfer are more at home in a physics lab than in a biology lab. In this overview, we aim to help neuroscientists overcome these obstacles and thus feel more comfortable with the FLIM-FRET method. Our goal is to aid researchers in the neuroscience community to achieve a better understanding of the fundamentals of FLIM-FRET and encourage them to fully leverage its powerful ability as a research tool. Published 2020. U.S. Government.
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Affiliation(s)
- Daniel J. Liput
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
- Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
| | - Tuan A. Nguyen
- Laboratory of Biophotonics and Quantum Biology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
| | - Shana M. Augustin
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
| | - Jeong Oen Lee
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
| | - Steven S. Vogel
- Laboratory of Biophotonics and Quantum Biology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland
- Corresponding author:
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Deng Q, Zhu Z, Shu X. Auto-Phase-Locked Time-Resolved Luminescence Detection: Principles, Applications, and Prospects. Front Chem 2020; 8:562. [PMID: 32695750 PMCID: PMC7339960 DOI: 10.3389/fchem.2020.00562] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/02/2020] [Indexed: 11/23/2022] Open
Abstract
Time-resolved luminescence measurement is a useful technique which can eliminate the background signals from scattering and short-lived autofluorescence. However, the relative instruments always require pulsed excitation sources and high-speed detectors. Moreover, the excitation and detecting shutter should be precisely synchronized by electronic phase matching circuitry, leading to expensiveness and high-complexity. To make time-resolved luminescence instruments simple and cheap, the automatic synchronization method was developed by using a mechanical chopper acted as both of the pulse generator and detection shutter. Therefore, the excitation and detection can be synchronized and locked automatically as the optical paths fixed. In this paper, we first introduced the time-resolved luminescence measurements and review the progress and current state of this field. Then, we discussed low-cost time-resolved techniques, especially chopper-based time-resolved luminescence detections. After that, we focused on auto-phase-locked method and some of its meaningful applications, such as time-gated luminescence imaging, spectrometer, and luminescence lifetime detection. Finally, we concluded with a brief outlook for auto-phase-locked time-resolved luminescence detection systems.
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Affiliation(s)
| | - Zece Zhu
- Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China
| | - Xuewen Shu
- Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China
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Hirmiz N, Tsikouras A, Osterlund EJ, Richards M, Andrews DW, Fang Q. Cross-talk reduction in a multiplexed synchroscan streak camera with simultaneous calibration. OPTICS EXPRESS 2019; 27:22602-22614. [PMID: 31510548 DOI: 10.1364/oe.27.022602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 07/14/2019] [Indexed: 06/10/2023]
Abstract
The streak camera is a picosecond resolution photodetector with parallel input capability; however, the degree of multiplexing is limited by crosstalk and temporal uncertainty in the sweeping field. We introduced a fixed time delay between adjacent fibers to reduce crosstalk in the synchroscan mode. The fixed delay and a tunable electronic delay between the input pulse and the synchroscan unit allows robust separation modes between the streaks, while spatial and temporal nonlinearities can be calibrated in. The efficacy of the design is demonstrated through a 100-fold multiplexed confocal fluorescence lifetime imaging microscope in live cells.
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Petit-Houdenot Y, Degrave A, Meyer M, Blaise F, Ollivier B, Marais CL, Jauneau A, Audran C, Rivas S, Veneault-Fourrey C, Brun H, Rouxel T, Fudal I, Balesdent MH. A two genes - for - one gene interaction between Leptosphaeria maculans and Brassica napus. THE NEW PHYTOLOGIST 2019; 223:397-411. [PMID: 30802965 DOI: 10.1111/nph.15762] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 02/18/2019] [Indexed: 05/26/2023]
Abstract
Interactions between Leptosphaeria maculans, causal agent of stem canker of oilseed rape, and its Brassica hosts are models of choice to explore the multiplicity of 'gene-for-gene' complementarities and how they diversified to increased complexity in the course of plant-pathogen co-evolution. Here, we support this postulate by investigating the AvrLm10 avirulence that induces a resistance response when recognized by the Brassica nigra resistance gene Rlm10. Using genome-assisted map-based cloning, we identified and cloned two AvrLm10 candidates as two genes in opposite transcriptional orientation located in a subtelomeric repeat-rich region of the genome. The AvrLm10 genes encode small secreted proteins and show expression profiles in planta similar to those of all L. maculans avirulence genes identified so far. Complementation and silencing assays indicated that both genes are necessary to trigger Rlm10 resistance. Three assays for protein-protein interactions showed that the two AvrLm10 proteins interact physically in vitro and in planta. Some avirulence genes are recognized by two distinct resistance genes and some avirulence genes hide the recognition specificities of another. Our L. maculans model illustrates an additional case where two genes located in opposite transcriptional orientation are necessary to induce resistance. Interestingly, orthologues exist for both L. maculans genes in other phytopathogenic species, with a similar genome organization, which may point to an important conserved effector function linked to heterodimerization of the two proteins.
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Affiliation(s)
- Yohann Petit-Houdenot
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Alexandre Degrave
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Michel Meyer
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Françoise Blaise
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Bénédicte Ollivier
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Claire-Line Marais
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Alain Jauneau
- Plateforme Imagerie, Pôle de Biotechnologie Végétale, Fédération de Recherche 3450, Castanet-Tolosan, F-31326, France
| | - Corinne Audran
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, F-31326, France
| | - Susana Rivas
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, F-31326, France
| | - Claire Veneault-Fourrey
- Laboratoire d'Excellence ARBRE, Centre INRA-Lorraine, INRA, UMR 1136, INRA-Université de Lorraine Interactions Arbres/Microorganismes, Champenoux, F-54280, France
- Laboratoire d'Excellence ARBRE, Faculté des Sciences et Technologies, UMR 1136 INRA-Université de Lorraine Interactions Arbres/Microorganismes, Université de Lorraine, Vandoeuvre les Nancy, F-54506, France
| | | | - Thierry Rouxel
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Isabelle Fudal
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
| | - Marie-Hélène Balesdent
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, Avenue Lucien Brétignières, BP 01, Thiverval-Grignon, F-78850, France
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Ramanujan VK. Rapid Assessment of Mitochondrial Complex I Activity and Metabolic Phenotyping of Breast Cancer Cells by NAD(p)H Cytometry. Cytometry A 2018; 95:101-109. [PMID: 30536579 DOI: 10.1002/cyto.a.23681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 09/11/2018] [Accepted: 10/30/2018] [Indexed: 11/10/2022]
Abstract
Cancer cells are known to display a variety of metabolic reprogramming strategies to fulfill their own growth and proliferative agenda. With the advent of high resolution imaging strategies, metabolomics techniques, and so forth, there is an increasing appreciation of critical role that tumor cell metabolism plays in the overall breast cancer (BC) growth. In this report, we demonstrate a sensitive, flow-cytometry-based assay for rapidly assessing the metabolic phenotypes in isolated suspensions of breast cancer cells. By measuring the temporal variation of NAD(p)H signals in unlabeled, living cancer cells, and by measuring mitochondrial membrane potential {Δψm } in fluorescently labeled cells, we demonstrate that these signals can reliably distinguish the metabolic phenotype of human breast cancer cells and can track the cellular sensitivity to drug candidates. We further show the utility of this metabolic ratio {Δψm /NAD(p)H} in monitoring mitochondrial functional improvement as well as metabolic heterogeneity in primary murine tumor cells isolated from tumor biopsies. Together, these results demonstrate a novel possibility for rapid metabolic functional screening applications as well as a metabolic phenotyping tool for determining drug sensitivity in living cancer cells. © 2018 International Society for Advancement of Cytometry.
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Affiliation(s)
- V Krishnan Ramanujan
- Metabolic Photonics Laboratory, Departments of Surgery and Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Los Angeles, California, 90048
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Camborde L, Jauneau A, Brière C, Deslandes L, Dumas B, Gaulin E. Detection of nucleic acid-protein interactions in plant leaves using fluorescence lifetime imaging microscopy. Nat Protoc 2017; 12:1933-1950. [PMID: 28837131 DOI: 10.1038/nprot.2017.076] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
DNA-binding proteins (DNA-BPs) and RNA-binding proteins (RNA-BPs) have critical roles in living cells in all kingdoms of life. Various experimental approaches exist for the study of nucleic acid-protein interactions in vitro and in vivo, but the detection of such interactions at the subcellular level remains challenging. Here we describe how to detect nucleic acid-protein interactions in plant leaves by using a fluorescence resonance energy transfer (FRET) approach coupled to fluorescence lifetime imaging microscopy (FLIM). Proteins of interest (POI) are tagged with a GFP and transiently expressed in plant cells to serve as donor fluorophore. After sample fixation and cell wall permeabilization, leaves are treated with Sytox Orange, a nucleic acid dye that can function as a FRET acceptor. Upon close association of the GFP-tagged POI with Sytox-Orange-stained nucleic acids, a substantial decrease of the GFP lifetime due to FRET between the donor and the acceptor can be monitored. Treatment with RNase before FRET-FLIM measurements allows determination of whether the POI associates with DNA and/or RNA. A step-by-step protocol is provided for sample preparation, data acquisition and analysis. We describe how to calibrate the equipment and include a tutorial explaining the use of the FLIM software. To illustrate our approach, we provide experimental procedures to detect the interaction between plant DNA and two proteins (the AeCRN13 effector from the oomycete Aphanomyces euteiches and the AtWRKY22 defensive transcription factor from Arabidopsis). This protocol allows the detection of protein-nucleic acid interactions in plant cells and can be completed in <2 d.
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Affiliation(s)
- Laurent Camborde
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS-Université Toulouse, Castanet-Tolosan, France
| | - Alain Jauneau
- CNRS, Plateforme Imagerie-Microscopie, Fédération de Recherche FR3450, Castanet-Tolosan, France
| | - Christian Brière
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS-Université Toulouse, Castanet-Tolosan, France
| | - Laurent Deslandes
- LIPM, Université de Toulouse, INRA, CNRS-Université Toulouse, Castanet-Tolosan, France
| | - Bernard Dumas
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS-Université Toulouse, Castanet-Tolosan, France
| | - Elodie Gaulin
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS-Université Toulouse, Castanet-Tolosan, France
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Serrano I, Buscaill P, Audran C, Pouzet C, Jauneau A, Rivas S. A non canonical subtilase attenuates the transcriptional activation of defence responses in Arabidopsis thaliana. eLife 2016; 5. [PMID: 27685353 DOI: 10.7554/elife.19755.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 09/28/2016] [Indexed: 05/20/2023] Open
Abstract
Proteases play crucial physiological functions in all organisms by controlling the lifetime of proteins. Here, we identified an atypical protease of the subtilase family [SBT5.2(b)] that attenuates the transcriptional activation of plant defence independently of its protease activity. The SBT5.2 gene produces two distinct transcripts encoding a canonical secreted subtilase [SBT5.2(a)] and an intracellular protein [SBT5.2(b)]. Concomitant to SBT5.2(a) downregulation, SBT5.2(b) expression is induced after bacterial inoculation. SBT5.2(b) localizes to endosomes where it interacts with and retains the defence-related transcription factor MYB30. Nuclear exclusion of MYB30 results in its reduced transcriptional activation and, thus, suppressed resistance. sbt5.2 mutants, with abolished SBT5.2(a) and SBT5.2(b) expression, display enhanced defence that is suppressed in a myb30 mutant background. Moreover, overexpression of SBT5.2(b), but not SBT5.2(a), in sbt5.2 plants reverts the phenotypes displayed by sbt5.2 mutants. Overall, we uncover a regulatory mode of the transcriptional activation of defence responses previously undescribed in eukaryotes.
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Affiliation(s)
- Irene Serrano
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Pierre Buscaill
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Corinne Audran
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Cécile Pouzet
- Fédération de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, Castanet-Tolosan, France
| | - Alain Jauneau
- Fédération de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, Castanet-Tolosan, France
| | - Susana Rivas
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
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Serrano I, Buscaill P, Audran C, Pouzet C, Jauneau A, Rivas S. A non canonical subtilase attenuates the transcriptional activation of defence responses in Arabidopsis thaliana. eLife 2016; 5. [PMID: 27685353 PMCID: PMC5074803 DOI: 10.7554/elife.19755] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 09/28/2016] [Indexed: 01/06/2023] Open
Abstract
Proteases play crucial physiological functions in all organisms by controlling the lifetime of proteins. Here, we identified an atypical protease of the subtilase family [SBT5.2(b)] that attenuates the transcriptional activation of plant defence independently of its protease activity. The SBT5.2 gene produces two distinct transcripts encoding a canonical secreted subtilase [SBT5.2(a)] and an intracellular protein [SBT5.2(b)]. Concomitant to SBT5.2(a) downregulation, SBT5.2(b) expression is induced after bacterial inoculation. SBT5.2(b) localizes to endosomes where it interacts with and retains the defence-related transcription factor MYB30. Nuclear exclusion of MYB30 results in its reduced transcriptional activation and, thus, suppressed resistance. sbt5.2 mutants, with abolished SBT5.2(a) and SBT5.2(b) expression, display enhanced defence that is suppressed in a myb30 mutant background. Moreover, overexpression of SBT5.2(b), but not SBT5.2(a), in sbt5.2 plants reverts the phenotypes displayed by sbt5.2 mutants. Overall, we uncover a regulatory mode of the transcriptional activation of defence responses previously undescribed in eukaryotes. DOI:http://dx.doi.org/10.7554/eLife.19755.001 Like animals, plants have evolved numerous ways to protect themselves from disease. When a plant detects an invading microbe, it massively changes which genes it expresses to establish a defensive response. This is possible thanks to the action of a type of protein, named transcription factors, which are able to bind to DNA in the cell nucleus and regulate gene expression. However, triggering such a response comes at a cost, and so plants must keep their defensive response in check such that they can allocate resources in a balanced way. In the model plant Arabidopsis, a protein named MYB30 is one transcription factor that is able to promote disease resistance. Previous research identified some proteins that can reduce the activity of this transcription factor to avoid triggering a response when it is not needed, for example, when no infectious microbes are present. However, it was likely that other proteins were also involved in the process. Now, Serrano et al. report that an enzyme called SBT5.2 is an additional negative regulator of MYB30 activity. SBT5.2 belongs to a family of protein-degrading enzymes called subtilases, which are typically localized outside cells. As such, it was unclear how SBT5.2 could interact and regulate a transcription factor that is found inside the nucleus of plant cells. Nevertheless, Serrano et al. found that the gene that encodes SBT5.2 actually gives rise to two distinct proteins. The first is a classical subtilase that is indeed located outside of the cell, and so cannot interact with MYB30 and does not affect its activity. The second protein is an atypical subtilase that localises to bubble-like compartments called vesicles within the cell and is able to highjack MYB30 on its way to the nucleus. When the atypical subtilase interacts with MYB30 at vesicles, it stops MYB30 from entering the nucleus. As a result, MYB30 cannot bind to the DNA nor activate its target genes. This means that the defensive response that normally depends on MYB30 is weakened. The work of Serrano et al. uncovers a new way to regulate the expression of defence-related genes. Further unravelling the molecular mechanisms involved in the fine-tuning of gene expression represents a challenging task for future research. DOI:http://dx.doi.org/10.7554/eLife.19755.002
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Affiliation(s)
- Irene Serrano
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Pierre Buscaill
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Corinne Audran
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Cécile Pouzet
- Fédération de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, Castanet-Tolosan, France
| | - Alain Jauneau
- Fédération de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, Castanet-Tolosan, France
| | - Susana Rivas
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
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Ramirez-Garcés D, Camborde L, Pel MJC, Jauneau A, Martinez Y, Néant I, Leclerc C, Moreau M, Dumas B, Gaulin E. CRN13 candidate effectors from plant and animal eukaryotic pathogens are DNA-binding proteins which trigger host DNA damage response. THE NEW PHYTOLOGIST 2016; 210:602-17. [PMID: 26700936 DOI: 10.1111/nph.13774] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 10/21/2015] [Indexed: 05/20/2023]
Abstract
To successfully colonize their host, pathogens produce effectors that can interfere with host cellular processes. Here we investigated the function of CRN13 candidate effectors produced by plant pathogenic oomycetes and detected in the genome of the amphibian pathogenic chytrid fungus Batrachochytrium dendrobatidis (BdCRN13). When expressed in Nicotiana, AeCRN13, from the legume root pathogen Aphanomyces euteiches, increases the susceptibility of the leaves to the oomycete Phytophthora capsici. When transiently expressed in amphibians or plant cells, AeCRN13 and BdCRN13 localize to the cell nuclei, triggering aberrant cell development and eventually causing cell death. Using Förster resonance energy transfer experiments in plant cells, we showed that both CRN13s interact with nuclear DNA and trigger plant DNA damage response (DDR). Mutating key amino acid residues in a predicted HNH-like endonuclease motif abolished the interaction of AeCRN13 with DNA, the induction of DDR and the enhancement of Nicotiana susceptibility to P. capsici. Finally, H2AX phosphorylation, a marker of DNA damage, and enhanced expression of genes involved in the DDR were observed in A. euteiches-infected Medicago truncatula roots. These results show that CRN13 from plant and animal eukaryotic pathogens promotes host susceptibility by targeting nuclear DNA and inducing DDR.
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Affiliation(s)
- Diana Ramirez-Garcés
- Laboratoire de Recherche en Sciences Végétales, UPS, Université Toulouse 3, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
- Laboratoire de Recherche en Sciences Végétales, CNRS, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
| | - Laurent Camborde
- Laboratoire de Recherche en Sciences Végétales, UPS, Université Toulouse 3, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
- Laboratoire de Recherche en Sciences Végétales, CNRS, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
| | - Michiel J C Pel
- Laboratoire de Recherche en Sciences Végétales, UPS, Université Toulouse 3, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
- Laboratoire de Recherche en Sciences Végétales, CNRS, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
| | - Alain Jauneau
- CNRS, Plateforme Imagerie-Microscopie Plateforme Imagerie-Microscopie, F-31326, Castanet-Tolosan, France
| | - Yves Martinez
- CNRS, Plateforme Imagerie-Microscopie Plateforme Imagerie-Microscopie, F-31326, Castanet-Tolosan, France
| | - Isabelle Néant
- Centre de Biologie du Développement, Université Toulouse 3, Toulouse, F31062, France
- CNRS UMR5547, Toulouse, F31062, France
| | - Catherine Leclerc
- Centre de Biologie du Développement, Université Toulouse 3, Toulouse, F31062, France
- CNRS UMR5547, Toulouse, F31062, France
| | - Marc Moreau
- Centre de Biologie du Développement, Université Toulouse 3, Toulouse, F31062, France
- CNRS UMR5547, Toulouse, F31062, France
| | - Bernard Dumas
- Laboratoire de Recherche en Sciences Végétales, UPS, Université Toulouse 3, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
- Laboratoire de Recherche en Sciences Végétales, CNRS, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
| | - Elodie Gaulin
- Laboratoire de Recherche en Sciences Végétales, UPS, Université Toulouse 3, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
- Laboratoire de Recherche en Sciences Végétales, CNRS, 24 chemin de Borde Rouge, BP42617, Auzeville, F-31326, Castanet-Tolosan, France
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15
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Regulatory Proteolysis in Arabidopsis-Pathogen Interactions. Int J Mol Sci 2015; 16:23177-94. [PMID: 26404238 PMCID: PMC4632692 DOI: 10.3390/ijms161023177] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Revised: 09/07/2015] [Accepted: 09/15/2015] [Indexed: 11/16/2022] Open
Abstract
Approximately two and a half percent of protein coding genes in Arabidopsis encode enzymes with known or putative proteolytic activity. Proteases possess not only common housekeeping functions by recycling nonfunctional proteins. By irreversibly cleaving other proteins, they regulate crucial developmental processes and control responses to environmental changes. Regulatory proteolysis is also indispensable in interactions between plants and their microbial pathogens. Proteolytic cleavage is simultaneously used both by plant cells, to recognize and inactivate invading pathogens, and by microbes, to overcome the immune system of the plant and successfully colonize host cells. In this review, we present available results on the group of proteases in the model plant Arabidopsis thaliana whose functions in microbial pathogenesis were confirmed. Pathogen-derived proteolytic factors are also discussed when they are involved in the cleavage of host metabolites. Considering the wealth of review papers available in the field of the ubiquitin-26S proteasome system results on the ubiquitin cascade are not presented. Arabidopsis and its pathogens are conferred with abundant sets of proteases. This review compiles a list of those that are apparently involved in an interaction between the plant and its pathogens, also presenting their molecular partners when available.
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17
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Abstract
Optical imaging assays, especially fluorescence molecular assays, are minimally invasive if not completely noninvasive, and thus an ideal technique to be applied to live specimens. These fluorescence imaging assays are a powerful tool in biomedical sciences as they allow the study of a wide range of molecular and physiological events occurring in biological systems. Furthermore, optical imaging assays bridge the gap between the in vitro cell-based analysis of subcellular processes and in vivo study of disease mechanisms in small animal models. In particular, the application of Förster resonance energy transfer (FRET) and fluorescence lifetime imaging (FLIM), well-known techniques widely used in microscopy, to the optical imaging assay toolbox, will have a significant impact in the molecular study of protein-protein interactions during cancer progression. This review article describes the application of FLIM-FRET to the field of optical imaging and addresses their various applications, both current and potential, to anti-cancer drug delivery and cancer research.
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Affiliation(s)
- Shilpi Rajoria
- Albany Medical College, The Center for Cardiovascular Sciences, Albany, NY, 12208
| | - Lingling Zhao
- Rensselaer Polytechnic Institute, Biomedical imaging Center and Department of Biomedical Engineering, Troy, NY 12180
| | - Xavier Intes
- Rensselaer Polytechnic Institute, Biomedical imaging Center and Department of Biomedical Engineering, Troy, NY 12180
| | - Margarida Barroso
- Albany Medical College, The Center for Cardiovascular Sciences, Albany, NY, 12208
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18
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Sun Y, Periasamy A. Localizing protein-protein interactions in living cells using fluorescence lifetime imaging microscopy. Methods Mol Biol 2015; 1251:83-107. [PMID: 25391796 DOI: 10.1007/978-1-4939-2080-8_6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In the past decade, advances in fluorescence lifetime imaging have extensively applied in the life sciences, from fundamental biological investigations to advanced clinical diagnosis. Fluorescence lifetime imaging microscopy (FLIM) is now routinely used in the biological sciences to monitor dynamic signaling events inside living cells, e.g., Protein-Protein interactions. In this chapter, we describe the calibration of both time-correlated single-photon counting (TCSPC) and frequency domain (FD) FLIM systems and the acquisition and analysis of FLIM-FRET data for investigating Protein-Protein interactions in living cells.
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Affiliation(s)
- Yuansheng Sun
- W.M. Keck Center for Cellular Imaging, Biology, University of Virginia, B005 Physical and Life Sciences Building, White Head Road, Charlottesville, VA, 22904, USA
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19
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Schoberer J, Liebminger E, Vavra U, Veit C, Castilho A, Dicker M, Maresch D, Altmann F, Hawes C, Botchway SW, Strasser R. The transmembrane domain of N -acetylglucosaminyltransferase I is the key determinant for its Golgi subcompartmentation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 80:809-22. [PMID: 25230686 PMCID: PMC4282539 DOI: 10.1111/tpj.12671] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 08/28/2014] [Accepted: 09/11/2014] [Indexed: 05/18/2023]
Abstract
Golgi-resident type-II membrane proteins are asymmetrically distributed across the Golgi stack. The intrinsic features of the protein that determine its subcompartment-specific concentration are still largely unknown. Here, we used a series of chimeric proteins to investigate the contribution of the cytoplasmic, transmembrane and stem region of Nicotiana benthamiana N-acetylglucosaminyltransferase I (GnTI) for its cis/medial-Golgi localization and for protein-protein interaction in the Golgi. The individual GnTI protein domains were replaced with those from the well-known trans-Golgi enzyme α2,6-sialyltransferase (ST) and transiently expressed in Nicotiana benthamiana. Using co-localization analysis and N-glycan profiling, we show that the transmembrane domain of GnTI is the major determinant for its cis/medial-Golgi localization. By contrast, the stem region of GnTI contributes predominately to homomeric and heteromeric protein complex formation. Importantly, in transgenic Arabidopsis thaliana, a chimeric GnTI variant with altered sub-Golgi localization was not able to complement the GnTI-dependent glycosylation defect. Our results suggest that sequence-specific features in the transmembrane domain of GnTI account for its steady-state distribution in the cis/medial-Golgi in plants, which is a prerequisite for efficient N-glycan processing in vivo.
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Affiliation(s)
- Jennifer Schoberer
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Eva Liebminger
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Ulrike Vavra
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Christiane Veit
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Alexandra Castilho
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Martina Dicker
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Daniel Maresch
- Department of Chemistry, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Friedrich Altmann
- Department of Chemistry, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
| | - Chris Hawes
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes UniversityHeadington, Oxford, OX3 0BP, UK
| | - Stanley W Botchway
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton LaboratoryHarwell-Oxford, Didcot, OX11 0QX, UK
| | - Richard Strasser
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life SciencesMuthgasse 18, Vienna, 1190, Austria
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20
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Becker W, Shcheslavkiy V, Frere S, Slutsky I. Spatially resolved recording of transient fluorescence-lifetime effects by line-scanning TCSPC. Microsc Res Tech 2014; 77:216-24. [DOI: 10.1002/jemt.22331] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 12/18/2013] [Accepted: 12/18/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Wolfgang Becker
- Becker & Hickl GmbH; Nahmitzer Damm 30; 12277 Berlin Germany
| | | | - Samuel Frere
- Sackler Faculty of Medicine, Department Physiology and Pharmacology; Sagol School of Neuroscience, Tel Aviv University; Tel Aviv 69978 Israel
| | - Inna Slutsky
- Sackler Faculty of Medicine, Department Physiology and Pharmacology; Sagol School of Neuroscience, Tel Aviv University; Tel Aviv 69978 Israel
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21
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Ramanujan VK. Metabolic imaging in multiple time scales. Methods 2013; 66:222-9. [PMID: 24013043 DOI: 10.1016/j.ymeth.2013.08.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/13/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022] Open
Abstract
We report here a novel combination of time-resolved imaging methods for probing mitochondrial metabolism in multiple time scales at the level of single cells. By exploiting a mitochondrial membrane potential reporter fluorescence we demonstrate the single cell metabolic dynamics in time scales ranging from microseconds to seconds to minutes in response to glucose metabolism and mitochondrial perturbations in real time. Our results show that in comparison with normal human mammary epithelial cells, the breast cancer cells display significant alterations in metabolic responses at all measured time scales by single cell kinetics, fluorescence recovery after photobleaching and by scaling analysis of time-series data obtained from mitochondrial fluorescence fluctuations. Furthermore scaling analysis of time-series data in living cells with distinct mitochondrial dysfunction also revealed significant metabolic differences thereby suggesting the broader applicability (e.g. in mitochondrial myopathies and other metabolic disorders) of the proposed strategies beyond the scope of cancer metabolism. We discuss the scope of these findings in the context of developing portable, real-time metabolic measurement systems that can find applications in preclinical and clinical diagnostics.
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Affiliation(s)
- V Krishnan Ramanujan
- Metabolic Photonics Laboratory, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Suite D6067, Los Angeles, CA 90048, USA; Department of Surgery, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048, USA; Department of Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048, USA; Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048, USA.
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22
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Leray A, Padilla-Parra S, Roul J, Héliot L, Tramier M. Spatio-Temporal Quantification of FRET in living cells by fast time-domain FLIM: a comparative study of non-fitting methods [corrected]. PLoS One 2013; 8:e69335. [PMID: 23874948 PMCID: PMC3715500 DOI: 10.1371/journal.pone.0069335] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 06/09/2013] [Indexed: 11/30/2022] Open
Abstract
Förster Resonance Energy Transfer (FRET) measured with Fluorescence Lifetime Imaging Microscopy (FLIM) is a powerful technique to investigate spatio-temporal regulation of protein-protein interactions in living cells. When using standard fitting methods to analyze time domain FLIM, the correct estimation of the FRET parameters requires a high number of photons and therefore long acquisition times which are incompatible with the observation of dynamic protein-protein interactions. Recently, non-fitting strategies have been developed for the analysis of FLIM images: the polar plot or "phasor" and the minimal fraction of interacting donor mfD . We propose here a novel non-fitting strategy based on the calculation of moments. We then compare the performance of these three methods when shortening the acquisition time: either by reducing the number of counted photons N or the number of temporal channels Nch , which is particularly adapted for the original fast-FLIM prototype presented in this work that employs the time gated approach. Based on theoretical calculations, Monte Carlo simulations and experimental data, we determine the domain of validity of each method. We thus demonstrate that the polar approach remains accurate for a large range of conditions (low N, Nch or small fractions of interacting donor fD ). The validity domain of the moments method is more restricted (not applicable when fD <0.25 or when Nch = 4) but it is more precise than the polar approach. We also demonstrate that the mfD is robust in all conditions and it is the most precise strategy; although it does not strictly provide the fraction of interacting donor. We show using the fast-FLIM prototype (with an acquisition rate up to 1 Hz) that these non-fitting strategies are very powerful for on-line analysis on a standard computer and thus for quantifying automatically the spatio-temporal activation of Rac-GTPase in living cells by FRET.
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Affiliation(s)
- Aymeric Leray
- Institut de Recherche Interdisciplinaire, USR 3078 CNRS, Université de Lille-Nord de France, Biophotonique Cellulaire Fonctionnelle, Villeneuve d'Ascq, France.
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23
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Sun Y, Rombola C, Jyothikumar V, Periasamy A. Förster resonance energy transfer microscopy and spectroscopy for localizing protein-protein interactions in living cells. Cytometry A 2013; 83:780-93. [PMID: 23813736 DOI: 10.1002/cyto.a.22321] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 04/08/2013] [Accepted: 05/23/2013] [Indexed: 12/15/2022]
Abstract
The fundamental theory of Förster resonance energy transfer (FRET) was established in the 1940s. Its great power was only realized in the past 20 years after different techniques were developed and applied to biological experiments. This success was made possible by the availability of suitable fluorescent probes, advanced optics, detectors, microscopy instrumentation, and analytical tools. Combined with state-of-the-art microscopy and spectroscopy, FRET imaging allows scientists to study a variety of phenomena that produce changes in molecular proximity, thereby leading to many significant findings in the life sciences. In this review, we outline various FRET imaging techniques and their strengths and limitations; we also provide a biological model to demonstrate how to investigate protein-protein interactions in living cells using both intensity- and fluorescence lifetime-based FRET microscopy methods.
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Affiliation(s)
- Yuansheng Sun
- The W.M. Keck Center for Cellular Imaging (KCCI), Department of Biology, Physical and Life Sciences Building, University of Virginia, Charlottesville, Virginia
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24
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Rinnenthal JL, Börnchen C, Radbruch H, Andresen V, Mossakowski A, Siffrin V, Seelemann T, Spiecker H, Moll I, Herz J, Hauser AE, Zipp F, Behne MJ, Niesner R. Parallelized TCSPC for dynamic intravital fluorescence lifetime imaging: quantifying neuronal dysfunction in neuroinflammation. PLoS One 2013; 8:e60100. [PMID: 23613717 PMCID: PMC3629055 DOI: 10.1371/journal.pone.0060100] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 02/22/2013] [Indexed: 01/27/2023] Open
Abstract
Two-photon laser-scanning microscopy has revolutionized our view on vital processes by revealing motility and interaction patterns of various cell subsets in hardly accessible organs (e.g. brain) in living animals. However, current technology is still insufficient to elucidate the mechanisms of organ dysfunction as a prerequisite for developing new therapeutic strategies, since it renders only sparse information about the molecular basis of cellular response within tissues in health and disease. In the context of imaging, Förster resonant energy transfer (FRET) is one of the most adequate tools to probe molecular mechanisms of cell function. As a calibration-free technique, fluorescence lifetime imaging (FLIM) is superior for quantifying FRET in vivo. Currently, its main limitation is the acquisition speed in the context of deep-tissue 3D and 4D imaging. Here we present a parallelized time-correlated single-photon counting point detector (p-TCSPC) (i) for dynamic single-beam scanning FLIM of large 3D areas on the range of hundreds of milliseconds relevant in the context of immune-induced pathologies as well as (ii) for ultrafast 2D FLIM in the range of tens of milliseconds, a scale relevant for cell physiology. We demonstrate its power in dynamic deep-tissue intravital imaging, as compared to multi-beam scanning time-gated FLIM suitable for fast data acquisition and compared to highly sensitive single-channel TCSPC adequate to detect low fluorescence signals. Using p-TCSPC, 256×256 pixel FLIM maps (300×300 µm(2)) are acquired within 468 ms while 131×131 pixel FLIM maps (75×75 µm(2)) can be acquired every 82 ms in 115 µm depth in the spinal cord of CerTN L15 mice. The CerTN L15 mice express a FRET-based Ca-biosensor in certain neuronal subsets. Our new technology allows us to perform time-lapse 3D intravital FLIM (4D FLIM) in the brain stem of CerTN L15 mice affected by experimental autoimmune encephalomyelitis and, thereby, to truly quantify neuronal dysfunction in neuroinflammation.
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Affiliation(s)
- Jan Leo Rinnenthal
- German Rheumatism Research Center, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
| | - Christian Börnchen
- Department of Dermatology and Venerology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Helena Radbruch
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
| | | | - Agata Mossakowski
- German Rheumatism Research Center, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
| | - Volker Siffrin
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
- Neurology Department, Johannes Gutenberg University Mainz, Mainz, Germany
| | | | | | - Ingrid Moll
- Department of Dermatology and Venerology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Josephine Herz
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
| | - Anja E. Hauser
- German Rheumatism Research Center, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
| | - Frauke Zipp
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
- Neurology Department, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Martin J. Behne
- Department of Dermatology and Venerology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Raluca Niesner
- German Rheumatism Research Center, Berlin, Germany
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
- Charité – University of Medicine, Berlin, Germany
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25
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Cesari S, Thilliez G, Ribot C, Chalvon V, Michel C, Jauneau A, Rivas S, Alaux L, Kanzaki H, Okuyama Y, Morel JB, Fournier E, Tharreau D, Terauchi R, Kroj T. The rice resistance protein pair RGA4/RGA5 recognizes the Magnaporthe oryzae effectors AVR-Pia and AVR1-CO39 by direct binding. THE PLANT CELL 2013; 25:1463-81. [PMID: 23548743 PMCID: PMC3663280 DOI: 10.1105/tpc.112.107201] [Citation(s) in RCA: 332] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Resistance (R) proteins recognize pathogen avirulence (Avr) proteins by direct or indirect binding and are multidomain proteins generally carrying a nucleotide binding (NB) and a leucine-rich repeat (LRR) domain. Two NB-LRR protein-coding genes from rice (Oryza sativa), RGA4 and RGA5, were found to be required for the recognition of the Magnaporthe oryzae effector AVR1-CO39. RGA4 and RGA5 also mediate recognition of the unrelated M. oryzae effector AVR-Pia, indicating that the corresponding R proteins possess dual recognition specificity. For RGA5, two alternative transcripts, RGA5-A and RGA5-B, were identified. Genetic analysis showed that only RGA5-A confers resistance, while RGA5-B is inactive. Yeast two-hybrid, coimmunoprecipitation, and fluorescence resonance energy transfer-fluorescence lifetime imaging experiments revealed direct binding of AVR-Pia and AVR1-CO39 to RGA5-A, providing evidence for the recognition of multiple Avr proteins by direct binding to a single R protein. Direct binding seems to be required for resistance as an inactive AVR-Pia allele did not bind RGA5-A. A small Avr interaction domain with homology to the Avr recognition domain in the rice R protein Pik-1 was identified in the C terminus of RGA5-A. This reveals a mode of Avr protein recognition through direct binding to a novel, non-LRR interaction domain.
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Affiliation(s)
- Stella Cesari
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Gaëtan Thilliez
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Cécile Ribot
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Véronique Chalvon
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Corinne Michel
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Alain Jauneau
- CNRS, Plateforme Imagerie-Microscopie, Fédération de Recherche FR3450, 31326 Castanet-Tolosan, France
| | - Susana Rivas
- INRA, UMR 441 Laboratoire des Interactions Plantes-Microorganismes, F-31326 Castanet-Tolosan, France
- CNRS, UMR 2594 Laboratoire des Interactions Plantes-Microorganismes, F-31326 Castanet-Tolosan, France
| | - Ludovic Alaux
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Hiroyuki Kanzaki
- Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003, Japan
| | - Yudai Okuyama
- Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003, Japan
| | - Jean-Benoit Morel
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Elisabeth Fournier
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Didier Tharreau
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
| | - Ryohei Terauchi
- Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003, Japan
| | - Thomas Kroj
- INRA, UMR 385 Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- CIRAD, UMR Biologie et Génétique des Interactions Plante-Parasite, F-34398 Montpellier, France
- Address correspondence to
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Schoberer J, Liebminger E, Botchway SW, Strasser R, Hawes C. Time-resolved fluorescence imaging reveals differential interactions of N-glycan processing enzymes across the Golgi stack in planta. PLANT PHYSIOLOGY 2013; 161:1737-54. [PMID: 23400704 PMCID: PMC3613452 DOI: 10.1104/pp.112.210757] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 02/10/2013] [Indexed: 05/18/2023]
Abstract
N-Glycan processing is one of the most important cellular protein modifications in plants and as such is essential for plant development and defense mechanisms. The accuracy of Golgi-located processing steps is governed by the strict intra-Golgi localization of sequentially acting glycosidases and glycosyltransferases. Their differential distribution goes hand in hand with the compartmentalization of the Golgi stack into cis-, medial-, and trans-cisternae, which separate early from late processing steps. The mechanisms that direct differential enzyme concentration are still unknown, but the formation of multienzyme complexes is considered a feasible Golgi protein localization strategy. In this study, we used two-photon excitation-Förster resonance energy transfer-fluorescence lifetime imaging microscopy to determine the interaction of N-glycan processing enzymes with differential intra-Golgi locations. Following the coexpression of fluorescent protein-tagged amino-terminal Golgi-targeting sequences (cytoplasmic-transmembrane-stem [CTS] region) of enzyme pairs in leaves of tobacco (Nicotiana spp.), we observed that all tested cis- and medial-Golgi enzymes, namely Arabidopsis (Arabidopsis thaliana) Golgi α-mannosidase I, Nicotiana tabacum β1,2-N-acetylglucosaminyltransferase I, Arabidopsis Golgi α-mannosidase II (GMII), and Arabidopsis β1,2-xylosyltransferase, form homodimers and heterodimers, whereas among the late-acting enzymes Arabidopsis β1,3-galactosyltransferase1 (GALT1), Arabidopsis α1,4-fucosyltransferase, and Rattus norvegicus α2,6-sialyltransferase (a nonplant Golgi marker), only GALT1 and medial-Golgi GMII were found to form a heterodimer. Furthermore, the efficiency of energy transfer indicating the formation of interactions decreased considerably in a cis-to-trans fashion. The comparative fluorescence lifetime imaging of several full-length cis- and medial-Golgi enzymes and their respective catalytic domain-deleted CTS clones further suggested that the formation of protein-protein interactions can occur through their amino-terminal CTS region.
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Affiliation(s)
| | - Eva Liebminger
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria (J.S., E.L., R.S.)
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Headington, Oxford OX3 0BP, United Kingdom (J.S., C.H.); and
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot OX11 0QX, United Kingdom (S.W.B.)
| | - Stanley W. Botchway
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria (J.S., E.L., R.S.)
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Headington, Oxford OX3 0BP, United Kingdom (J.S., C.H.); and
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot OX11 0QX, United Kingdom (S.W.B.)
| | - Richard Strasser
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria (J.S., E.L., R.S.)
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Headington, Oxford OX3 0BP, United Kingdom (J.S., C.H.); and
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot OX11 0QX, United Kingdom (S.W.B.)
| | - Chris Hawes
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria (J.S., E.L., R.S.)
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Headington, Oxford OX3 0BP, United Kingdom (J.S., C.H.); and
- Research Complex at Harwell, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot OX11 0QX, United Kingdom (S.W.B.)
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Abstract
BACKGROUND One of the major hurdles in studying diabetes pathophysiology is the lack of adequate methodology that allows for direct and real-time determination of glucose transport and metabolism in cells and tissues. In this article, we present a new methodology that adopts frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) to visualize and quantify the dynamics of intracellular glucose within living cells using a biosensor protein based on fluorescence resonance energy transfer (FRET). METHOD The biosensor protein was developed by fusing a FRET pair, an AcGFP1 donor and a mCherry acceptor to N- and C- termini of a mutant glucose-binding protein (GBP), respectively. The probe was expressed and biosynthesized inside the cells, offering continuous monitoring of glucose dynamics in real time through fluorescence lifetime imaging microscopy (FLIM) measurement. RESULTS We transfected the deoxyribonucleic acid of the AcGFP1-GBP-mCherry sensor into murine myoblast cells, C2C12, and continuously monitored the changes in intracellular glucose concentrations in response to the variation in extracellular glucose, from which we determined glucose uptake and clearance rates. The distribution of intracellular glucose concentration was also characterized. We detected a high glucose concentration in a region close to the cell membrane and a low glucose concentration in a region close to the nucleus. The monoexponential decay of AcGFP1 was distinguished using FD-FLIM. CONCLUSIONS This work enables continuous glucose monitoring (CGM) within living cells using FD-FLIM and a biosensor protein. The sensor protein developed offers a new means for quantitatively analyzing glucose homeostasis at the cellular level. Data accumulated from these studies will help increase our understanding of the pathology of diabetes.
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Affiliation(s)
| | - Sha Jin
- Department of Biomedical Engineering, College of Engineering, University of Arkansas, Fayetteville, Arkansas
| | - Kaiming Ye
- Department of Biomedical Engineering, College of Engineering, University of Arkansas, Fayetteville, Arkansas
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28
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Affiliation(s)
- Francisco Zaera
- Department of Chemistry, University of California, Riverside, California 92521, United States
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Tsikouras A, Ning J, Ng S, Berman R, Andrews DW, Fang Q. Streak camera crosstalk reduction using a multiple delay optical fiber bundle. OPTICS LETTERS 2012; 37:250-2. [PMID: 22854483 DOI: 10.1364/ol.37.000250] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The streak camera is one of the fastest photodetection systems, while its capability of multiplexing is particularly attractive to many applications requiring parallel data acquisition. The degree of multiplexing in a streak camera is limited by the crosstalk between input channels. We developed a technique that introducing a fixed time delay between adjacent fiber channels in a customized two-dimensional to one-dimensional fiber array to significantly reduce crosstalk both at the sample plane and at the input of a streak camera. A prototype system has been developed that supports 100 input channels, and its performance in fluorescence microscopy is demonstrated.
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Affiliation(s)
- Anthony Tsikouras
- Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada
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30
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Biener E, Charlier M, Ramanujan VK, Daniel N, Eisenberg A, Bjørbaek C, Herman B, Gertler A, Djiane J. Quantitative FRET imaging of leptin receptor oligomerization kinetics in single cells. Biol Cell 2012; 97:905-19. [PMID: 15771593 DOI: 10.1042/bc20040511] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION Leptin, an adipocyte-secreted hormone, signals through activation of its membrane-embedded receptor (LEPR). To study the leptin-induced events occurring in short (LEPRa) and long (LEPRb) LEPRs in the cell membrane, by FRET (fluorescence resonance energy transfer) methodology, the respective receptors, tagged at their C-terminal with CFP (cyan fluorescent protein) or YFP (yellow fluorescent protein), were prepared. RESULTS The constructs encoding mLEPRa (mouse LEPRa)-YFP and mLEPRa-CFP, mLEPRb-YFP and mLEPRb-CFP were tested for biological activity in transiently transfected CHO cells (Chinese-hamster ovary cells) and HEK-293T cells (human embryonic kidney 293 T cells) for activation of STAT3 (signal transduction and activators of transcription 3)-mediated LUC (luciferase) activity and binding of radiolabelled leptin. All four constructs were biologically active and were as potent as their untagged counterparts. The localization pattern of the fused protein appeared to be confined almost entirely to the cell membrane. The leptin-dependent interaction between various types of receptors in fixed cells were studied by measuring FRET, using fluorescence lifetime imaging microscopy and acceptor photobleaching methods. CONCLUSIONS Both methods yielded similar results, indicating that (1) leptin receptors expressed in the cell membrane exist mostly as preformed LEPRa/LEPRa or LEPRb/LEPRb homo-oligomers but not as LEPRb/LEPRa hetero-oligomers; (2) the appearance of transient leptin-induced FRET in cells transfected with LEPRb/LEPRb reflects both a conformational change that leads to closer interaction in the cytosolic part and a higher FRET signal, as well as de novo homo-oligomerization; (3) in LEPRa/LEPRa, exposure to leptin does not lead to any increase in FRET signalling as the proximity of CFP and YFP fluorophores in space already gives maximal FRET efficiency of the preoligomerized receptors.
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Affiliation(s)
- Eva Biener
- The Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
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31
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Heidrich K, Wirthmueller L, Tasset C, Pouzet C, Deslandes L, Parker JE. Arabidopsis EDS1 connects pathogen effector recognition to cell compartment-specific immune responses. Science 2011; 334:1401-4. [PMID: 22158818 DOI: 10.1126/science.1211641] [Citation(s) in RCA: 260] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Pathogen effectors are intercepted by plant intracellular nucleotide binding-leucine-rich repeat (NB-LRR) receptors. However, processes linking receptor activation to downstream defenses remain obscure. Nucleo-cytoplasmic basal resistance regulator EDS1 (ENHANCED DISEASE SUSCEPTIBILITY1) is indispensible for immunity mediated by TIR (Toll-interleukin-1 receptor)-NB-LRR receptors. We show that Arabidopsis EDS1 molecularly connects TIR-NB-LRR disease resistance protein RPS4 recognition of bacterial effector AvrRps4 to defense pathways. RPS4-EDS1 and AvrRps4-EDS1 complexes are detected inside nuclei of living tobacco cells after transient coexpression and in Arabidopsis soluble leaf extracts after resistance activation. Forced AvrRps4 localization to the host cytoplasm or nucleus reveals cell compartment-specific RPS4-EDS1 defense branches. Although nuclear processes restrict bacterial growth, programmed cell death and transcriptional resistance reinforcement require nucleo-cytoplasmic coordination. Thus, EDS1 behaves as an effector target and activated TIR-NB-LRR signal transducer for defenses across cell compartments.
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Affiliation(s)
- Katharina Heidrich
- Max-Planck Institute for Plant Breeding Research, Department of Plant-Microbe Interactions, D-50829 Cologne, Germany
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32
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Niesner RA, Hauser AE. Recent advances in dynamic intravital multi-photon microscopy. Cytometry A 2011; 79:789-98. [DOI: 10.1002/cyto.a.21140] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 08/11/2011] [Accepted: 08/13/2011] [Indexed: 01/09/2023]
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Sun Y, Day RN, Periasamy A. Investigating protein-protein interactions in living cells using fluorescence lifetime imaging microscopy. Nat Protoc 2011; 6:1324-40. [PMID: 21886099 PMCID: PMC3169422 DOI: 10.1038/nprot.2011.364] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fluorescence lifetime imaging microscopy (FLIM) is now routinely used for dynamic measurements of signaling events inside living cells, including detection of protein-protein interactions. An understanding of the basic physics of fluorescence lifetime measurements is required to use this technique. In this protocol, we describe both the time-correlated single photon counting and the frequency-domain methods for FLIM data acquisition and analysis. We describe calibration of both FLIM systems, and demonstrate how they are used to measure the quenched donor fluorescence lifetime that results from Förster resonance energy transfer (FRET). We then show how the FLIM-FRET methods are used to detect the dimerization of the transcription factor CCAAT/enhancer binding protein-α in live mouse pituitary cell nuclei. Notably, the factors required for accurate determination and reproducibility of lifetime measurements are described. With either method, the entire protocol including specimen preparation, imaging and data analysis takes ∼2 d.
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Affiliation(s)
- Yuansheng Sun
- W.M. Keck Center for Cellular Imaging, Department of Biology, University of Virginia, Charlottesville, Virginia, USA
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CDC25B associates with a centrin 2-containing complex and is involved in maintaining centrosome integrity. Biol Cell 2011; 103:55-68. [PMID: 21091437 PMCID: PMC3025493 DOI: 10.1042/bc20100111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Background information. CDC25 (cell division cycle 25) phosphatases function as activators of CDK (cyclin-dependent kinase)–cyclin complexes to regulate progression through the CDC. We have recently identified a pool of CDC25B at the centrosome of interphase cells that plays a role in regulating centrosome numbers. Results. In the present study, we demonstrate that CDC25B forms a close association with Ctn (centrin) proteins at the centrosome. This interaction involves both N- and C-terminal regions of CDC25B and requires CDC25B binding to its CDK–cyclin substrates. However, the interaction is not dependent on the enzyme activity of CDC25B. Although CDC25B appears to bind indirectly to Ctn2, this association is pertinent to CDC25B localization at the centrosome. We further demonstrate that CDC25B plays a role in maintaining the overall integrity of the centrosome, by regulating the centrosome levels of multiple centrosome proteins, including that of Ctn2. Conclusions. Our results therefore suggest that CDC25B associates with a Ctn2-containing multiprotein complex in the cytoplasm, which targets it to the centrosome, where it plays a role in maintaining the centrosome levels of Ctn2 and a number of other centrosome components.
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35
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Abstract
Ligand binding to cell membrane receptors sets off a series of protein interactions that convey the nuances of ligand identity to the cell interior. The information may be encoded in conformational changes, the interaction kinetics and, in the case of multichain immunoreceptors, by chain rearrangements. The signals may be modulated by dynamic compartmentalization of the cell membrane, cellular architecture, motility, and activation-all of which are difficult to reconstitute for studies of receptor signaling in vitro. In this paper, we will discuss how protein interactions in general and receptor signaling in particular can be studied in living cells by different fluorescence imaging techniques. Particularly versatile are methods that exploit Förster resonance energy transfer (FRET), which is exquisitely sensitive to the nanometer-range proximity and orientation between fluorophores. Fluorescence correlation microscopy (FCM) can provide complementary information about the stoichiometry and diffusion kinetics of large complexes, while bimolecular fluorescence complementation (BiFC) and other complementation techniques can capture transient interactions. A continuing challenge is extracting from the imaging data the quantitative information that is necessary to verify different models of signal transduction.
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Affiliation(s)
- Tomasz Zal
- Department of Immunology, University of Texas, MD Anderson Cancer Center, Houston TX, USA
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36
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Perochon A, Dieterle S, Pouzet C, Aldon D, Galaud JP, Ranty B. Interaction of a plant pseudo-response regulator with a calmodulin-like protein. Biochem Biophys Res Commun 2010; 398:747-51. [PMID: 20627089 DOI: 10.1016/j.bbrc.2010.07.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2010] [Accepted: 07/08/2010] [Indexed: 01/26/2023]
Abstract
Calmodulin (CaM) plays a crucial role in the regulation of diverse cellular processes by modulating the activities of numerous target proteins. Plants possess an extended CaM family including numerous CaM-like proteins (CMLs), most of which appear to be unique to plants. We previously demonstrated a role for CML9 in abiotic stress tolerance and seed germination in Arabidopsis thaliana. We report here the isolation of PRR2, a pseudo-response regulator as a CML9 interacting protein by screening an expression library prepared from Arabidopsis seedlings with CML9 as bait in a yeast two-hybrid system. PRR2 is similar to the response regulators of the two-component system, but lacks the invariant residue required for phosphorylation by which response regulators switch their output response, suggesting the existence of alternative regulatory mechanisms. PRR2 was found to bind CML9 and closely related CMLs but not a canonical CaM. Mapping analyses indicate that an almost complete form of PRR2 is required for interaction with CML9, suggesting a recognition mode different from the classical CaM-target peptide complex. PRR2 contains several features that are typical of transcription factors, including a GARP DNA recognition domain, a Pro-rich region and a Golden C-terminal box. PRR2 and CML9 as fusion proteins with fluorescent tags co-localized in the nucleus of plant cells, and their interaction in the nuclear compartment was validated in planta by using a fluorophore-tagged protein interaction assay. These findings suggest that binding of PRR2 to CML9 may be an important mechanism to modulate the physiological role of this transcription factor in plants.
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Affiliation(s)
- Alexandre Perochon
- UMR 5546 CNRS/Université Toulouse 3, Pole de Biotechnologie végétale, BP 42617 Auzeville, 31326 Castanet-Tolosan cedex, France
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37
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Affiliation(s)
- Mikhail Y. Berezin
- Department of Radiology, Washington University School of Medicine, 4525 Scott Ave, St. Louis, USA, Tel. 314-747-0701, 314-362-8599, fax 314-747-5191
| | - Samuel Achilefu
- Department of Radiology, Washington University School of Medicine, 4525 Scott Ave, St. Louis, USA, Tel. 314-747-0701, 314-362-8599, fax 314-747-5191
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Selective detection of NADPH oxidase in polymorphonuclear cells by means of NAD(P)H-based fluorescence lifetime imaging. JOURNAL OF BIOPHYSICS 2008; 2008:602639. [PMID: 20107577 PMCID: PMC2809359 DOI: 10.1155/2008/602639] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 09/02/2008] [Indexed: 11/18/2022]
Abstract
NADPH oxidase (NOX2) is a multisubunit membrane-bound enzyme complex that, upon assembly in activated cells,
catalyses the reduction of free oxygen to its superoxide anion, which further leads to reactive oxygen species (ROS) that are
toxic to invading pathogens, for example, the fungus Aspergillus fumigatus. Polymorphonuclear cells (PMNs) employ both
nonoxidative and oxidative mechanisms to clear this fungus from the lung. The oxidative mechanisms mainly depend on the
proper assembly and function of NOX2. We identified for the first time the NAD(P)H-dependent enzymes involved in such
oxidative mechanisms by means of biexponential NAD(P)H-fluorescence lifetime imaging (FLIM). A specific fluorescence
lifetime of 3670±140 picoseconds as compared to 1870 picoseconds for NAD(P)H bound to mitochondrial enzymes could be
associated with NADPH bound to oxidative enzymes in activated PMNs. Due to its predominance in PMNs and due to the
use of selective activators and inhibitors, we strongly believe that this specific lifetime mainly originates from NOX2. Our
experiments also revealed the high site specificity of the NOX2 assembly and, thus, of the ROS production as well as the
dynamic nature of these phenomena. On the example of NADPH oxidase, we demonstrate the potential of NAD(P)H-based
FLIM in selectively investigating enzymes during their cellular function.
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Ramshesh VK, Lemasters JJ. Pinhole shifting lifetime imaging microscopy. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:064001. [PMID: 19123648 PMCID: PMC2743888 DOI: 10.1117/1.3027503] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Lifetime imaging microscopy is a powerful tool to probe biological phenomena independent of luminescence intensity and fluorophore concentration. We describe time-resolved imaging of long-lifetime luminescence with an unmodified commercial laser scanning confocal/multiphoton microscope. The principle of the measurement is displacement of the detection pinhole to collect delayed luminescence from a position lagging the rasting laser beam. As proof of principle, luminescence from microspheres containing europium (Eu(3+)), a red emitting probe, was compared to that of short-lifetime green-fluorescing microspheres and/or fluorescein and rhodamine in solution. Using 720-nm two-photon excitation and a pinhole diameter of 1 Airy unit, the short-lifetime fluorescence of fluorescein, rhodamine and green microspheres disappeared much more rapidly than the long-lifetime phosphorescence of Eu(3+) microspheres as the pinhole was repositioned in the lagging direction. In contrast, repositioning of the pinhole in the leading and orthogonal directions caused equal loss of short- and long-lifetime luminescence. From measurements at different lag pinhole positions, a lifetime of 270 micros was estimated for the Eu(3+) microspheres, consistent with independent measurements. This simple adaptation is the basis for quantitative 3-D lifetime imaging microscopy.
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Affiliation(s)
- Venkat K Ramshesh
- Medical University of South Carolina, Center for Cell Death, Injury and Regeneration and Hollings Cancer Center, Charleston, South Carolina 29425, USA
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40
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Bernoux M, Timmers T, Jauneau A, Brière C, de Wit PJGM, Marco Y, Deslandes L. RD19, an Arabidopsis cysteine protease required for RRS1-R-mediated resistance, is relocalized to the nucleus by the Ralstonia solanacearum PopP2 effector. THE PLANT CELL 2008; 20:2252-64. [PMID: 18708476 PMCID: PMC2553607 DOI: 10.1105/tpc.108.058685] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 07/18/2008] [Accepted: 07/31/2008] [Indexed: 05/18/2023]
Abstract
Bacterial wilt, a disease impacting cultivated crops worldwide, is caused by the pathogenic bacterium Ralstonia solanacearum. PopP2 (for Pseudomonas outer protein P2) is an R. solanacearum type III effector that belongs to the YopJ/AvrRxv protein family and interacts with the Arabidopsis thaliana RESISTANT TO RALSTONIA SOLANACEARUM 1-R (RRS1-R) resistance protein. RRS1-R contains the Toll/Interleukin1 receptor-nucleotide binding site-Leu-rich repeat domains found in several cytoplasmic R proteins and a C-terminal WRKY DNA binding domain. In this study, we identified the Arabidopsis Cys protease RESPONSIVE TO DEHYDRATION19 (RD19) as being a PopP2-interacting protein whose expression is induced during infection by R. solanacearum. An Arabidopsis rd19 mutant in an RRS1-R genetic background is compromised in resistance to the bacterium, indicating that RD19 is required for RRS1-R-mediated resistance. RD19 normally localizes in mobile vacuole-associated compartments and, upon coexpression with PopP2, is specifically relocalized to the plant nucleus, where the two proteins physically interact. No direct physical interaction between RRS1-R and RD19 in the presence of PopP2 was detected in the nucleus as determined by Förster resonance energy transfer. We propose that RD19 associates with PopP2 to form a nuclear complex that is required for activation of the RRS1-R-mediated resistance response.
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Affiliation(s)
- Maud Bernoux
- Laboratoire des Interactions Plantes Microorganismes, Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique 2594/441, F-31320 Castanet-Tolosan, France
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41
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Nakabayashi T, Nagao I, Kinjo M, Aoki Y, Tanaka M, Ohta N. Stress-induced environmental changes in a single cell as revealed by fluorescence lifetime imaging. Photochem Photobiol Sci 2008; 7:671-4. [PMID: 18528550 DOI: 10.1039/b805032e] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fluorescence lifetime image of HeLa cells expressing an enhanced green fluorescent protein (EGFP)-fusion protein changes under stress, which allows noninvasive determination of the status of individual cells.
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Affiliation(s)
- Takakazu Nakabayashi
- Research Institute for Electronic Science, Hokkaido University, Sapporo, 060-0812, Japan
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Nakabayashi T, Wang HP, Kinjo M, Ohta N. Application of fluorescence lifetime imaging of enhanced green fluorescent protein to intracellular pH measurements. Photochem Photobiol Sci 2008; 7:668-70. [PMID: 18528549 DOI: 10.1039/b800391b] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have shown that the intracellular pH of a single HeLa cell expressing the enhanced green fluorescent protein (EGFP) can be imaged using the fluorescence lifetime of EGFP, which can be interpreted in terms of the pH-dependent ionic equilibrium of the p-hydroxybenzylidene-imidazolidinone structure of the chromophore of EGFP.
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Affiliation(s)
- Takakazu Nakabayashi
- Research Institute for Electronic Science, Hokkaido University, Sapporo, 060-0812, Japan
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43
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Zal T. Visualization of protein interactions in living cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 640:183-97. [PMID: 19065792 PMCID: PMC5788009 DOI: 10.1007/978-0-387-09789-3_14] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Ligand binding to cell membrane receptors sets off a series of protein interactions that convey the nuances ofligand identity to the cell interior. The information may be encoded in conformational changes, the interaction kinetics and, in the case of multichain immunoreceptors, by chain rearrangements. The signals may be modulated by dynamic compartmentalization of the cell membrane, cellular architecture, motility, and activation--all of which are difficult to reconstitute for studies of receptor signaling in vitro. In this chapter, we will discuss how protein interactions in general and receptor signaling in particular can be studied in living cells by different fluorescence imaging techniques. Particularly versatile are methods that exploit Förster resonance energy transfer (FRET), which is exquisitely sensitive to the nanometer-range proximity and orientation between fluorophores. Fluorescence correlation microscopy (FCM) can provide complementary information about the stoichiometry and diffusion kinetics of large complexes, while bimolecular fluorescence complementation (BiFC) and other complementation techniques can capture transient interactions. A continuing challenge is extracting from the imaging data the quantitative information that is necessary to verify different models of signal transduction.
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Affiliation(s)
- Tomasz Zal
- Department of Immunology, University of Texas, MD Anderson Cancer Center, Unit 902, 7455 Fannin, Houston TX, USA.
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Rizzo MA, Springer G, Segawa K, Zipfel WR, Piston DW. Optimization of pairings and detection conditions for measurement of FRET between cyan and yellow fluorescent proteins. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2006; 12:238-54. [PMID: 17481360 DOI: 10.1017/s1431927606060235] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 10/26/2005] [Indexed: 05/05/2023]
Abstract
Detection of Förster resonance energy transfer (FRET) between cyan and yellow fluorescent proteins is a key method for quantifying dynamic processes inside living cells. To compare the different cyan and yellow fluorescent proteins, FRET efficiencies were measured for a set of the possible donor:acceptor pairs. FRET between monomeric Cerulean and Venus is more efficient than the ECFP:EYFP pair and has a 10% greater Förster distance. We also compared several live cell microscopy methods for measuring FRET. The greatest contrast for changes in intramolecular FRET is obtained using a combination of ratiometric and spectral imaging. However, this method is not appropriate for establishing the presence of FRET without extra controls. Accurate FRET efficiencies are obtained by fluorescence lifetime imaging microscopy, but these measurements are difficult to collect and analyze. Acceptor photobleaching is a common and simple method for measuring FRET efficiencies. However, when applied to cyan to yellow fluorescent protein FRET, this method becomes prone to an artifact that leads to overestimation of FRET efficiency and false positive signals. FRET was also detected by measuring the acceptor fluorescence anisotropy. Although difficult to quantify, this method is exceptional for screening purposes, because it provides high contrast for discriminating FRET.
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Affiliation(s)
- Mark A Rizzo
- University of Maryland School of Medicine, Baltimore, MD 21201, USA
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45
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Breusegem SY, Levi M, Barry NP. Fluorescence Correlation Spectroscopy and Fluorescence Lifetime Imaging Microscopy. ACTA ACUST UNITED AC 2006; 103:e41-9. [PMID: 16543763 DOI: 10.1159/000090615] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
With few and commercially available add-ons, both confocal and full-field fluorescence microscopes can be adapted to provide more information on the biological sample of interest. In this review we discuss the possibilities offered by two additional functionalities to fluorescence microscopes, fluorescence correlation spectroscopy (FCS) and fluorescence lifetime imaging mi croscopy (FLIM). FCS measurements at a single point in a sample allow kinetic and diffusion properties of fluorescently labeled molecules to be determined, as well as their concentration and aggregation state. Data from multiple points of the sample can be acquired using scanning-FCS, image correlation spectroscopy, and raster image correlation spectroscopy. These techniques cover phenomena with characteristic durations from sub-microsecond to second time scales. The power of FLIM lies in the fact that the measured fluorescent lifetime of a fluorophore is sensitive to the molecular environment of that fluorophore. FLIM is a robust means to quantify Forster resonance energy transfer and thus determine protein-protein interactions or protein conformational changes. In addition, FLIM is very valuable for functional imaging of ion concentrations in cells and tissues as it can be applied in heterogeneously labeled samples. In summary, FCS and FLIM allow information to be gathered beyond localization, including diffusional mobility, protein clustering and interactions, and molecular environment.
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Affiliation(s)
- Sophia Y Breusegem
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Health Sciences Center, Denver, Colo 80262, USA
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46
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Thaler C, Koushik SV, Blank PS, Vogel SS. Quantitative multiphoton spectral imaging and its use for measuring resonance energy transfer. Biophys J 2005; 89:2736-49. [PMID: 16040744 PMCID: PMC1366774 DOI: 10.1529/biophysj.105.061853] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 07/07/2005] [Indexed: 11/18/2022] Open
Abstract
Protein labeling with green fluorescent protein derivatives has become an invaluable tool in cell biology. Protein quantification, however, is difficult when cells express constructs with overlapping fluorescent emissions. Under these conditions, signal separation using emission filters is inherently inefficient. Spectral imaging solves this problem by recording emission spectra directly. Unfortunately, linear unmixing, the algorithm used for quantifying individual fluorophores from emission spectra, fails when resonance energy transfer (RET) is present. We therefore sought to develop an unmixing algorithm that incorporates RET. An equation for spectral emission incorporating RET was derived and an assay based on this formalism, spectral RET (sRET), was developed. Standards with defined RET efficiencies and with known Cerulean/Venus ratios were constructed and used to test sRET. We demonstrate that sRET analysis is a comprehensive, photon-efficient method for imaging RET efficiencies and accurately determines donor and acceptor concentrations in living cells.
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Affiliation(s)
- Christopher Thaler
- National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA
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Abstract
Nonlinear microscopy, a general term that embraces any microscopy technique based on nonlinear optics, is further establishing itself as an important tool in neurobiology. Recent advances in labels, labeling techniques, and the use of native or genetically encoded contrast agents have bolstered the capacity of nonlinear microscopes to image the structure and function of not just single cells but of entire networks of cells. Along with novel strategies to image over exceptionally long durations and with increased depth penetration in living brains, these advances are opening new opportunities in neurobiology that were previously unavailable.
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Affiliation(s)
- Jerome Mertz
- Boston University, Department of Biomedical Engineering, 44 Cummington Street, Boston, Massachusetts 02215, USA.
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Abstract
Förster (or fluorescence) resonance energy transfer (FRET) and fluorescence lifetime imaging (FLIM) have moved center stage and are increasingly forming part of multifaceted imaging approaches. They are complementary methodologies that can be applied to advanced quantitative analyses. The widening application of FRET and FLIM has been driven by the availability of suitable fluorophores, increasingly sophisticated microscopy systems, methodologies to correct spectral bleed-through, and the ease with which FRET can be combined with other techniques. FRET and FLIM have recently found use in several applications: in the analysis of protein-protein interactions with high spatial and temporal specificity (e.g. clustering), in the study of conformational changes, in the analysis of binding sequences, and in applications such as high-throughput screening.
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Affiliation(s)
- Horst Wallrabe
- Keck Center for Cellular Imaging, Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, Virginia 22904, USA
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RAMANUJAN VKRISHNAN, ZHANG JIANHUA, CENTONZE VICTORIAE, HERMAN BRIAN. Streak Fluorescence Lifetime Imaging Microscopy: A Novel Technology for Quantitative FRET Imaging. Mol Imaging 2005. [DOI: 10.1016/b978-019517720-6.50021-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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50
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Pelet S, Previte MJR, Laiho LH, So PTC. A fast global fitting algorithm for fluorescence lifetime imaging microscopy based on image segmentation. Biophys J 2004; 87:2807-17. [PMID: 15454472 PMCID: PMC1304699 DOI: 10.1529/biophysj.104.045492] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 07/16/2004] [Indexed: 11/18/2022] Open
Abstract
Global fitting algorithms have been shown to improve effectively the accuracy and precision of the analysis of fluorescence lifetime imaging microscopy data. Global analysis performs better than unconstrained data fitting when prior information exists, such as the spatial invariance of the lifetimes of individual fluorescent species. The highly coupled nature of global analysis often results in a significantly slower convergence of the data fitting algorithm as compared with unconstrained analysis. Convergence speed can be greatly accelerated by providing appropriate initial guesses. Realizing that the image morphology often correlates with fluorophore distribution, a global fitting algorithm has been developed to assign initial guesses throughout an image based on a segmentation analysis. This algorithm was tested on both simulated data sets and time-domain lifetime measurements. We have successfully measured fluorophore distribution in fibroblasts stained with Hoechst and calcein. This method further allows second harmonic generation from collagen and elastin autofluorescence to be differentiated in fluorescence lifetime imaging microscopy images of ex vivo human skin. On our experimental measurement, this algorithm increased convergence speed by over two orders of magnitude and achieved significantly better fits.
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Affiliation(s)
- S Pelet
- Department of Mechanical Engineering and Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
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