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Bellec M, Chen R, Dhayni J, Trullo A, Avinens D, Karaki H, Mazzarda F, Lenden-Hasse H, Favard C, Lehmann R, Bertrand E, Lagha M, Dufourt J. Boosting the toolbox for live imaging of translation. RNA (NEW YORK, N.Y.) 2024; 30:1374-1394. [PMID: 39060168 PMCID: PMC11404453 DOI: 10.1261/rna.080140.124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2024] [Accepted: 06/30/2024] [Indexed: 07/28/2024]
Abstract
Live imaging of translation based on tag recognition by a single-chain antibody is a powerful technique to assess translation regulation in living cells. However, this approach is challenging and requires optimization in terms of expression level and detection sensitivity of the system, especially in a multicellular organism. Here, we improved existing fluorescent tools and developed new ones to image and quantify nascent translation in the living Drosophila embryo and in mammalian cells. We tested and characterized five different green fluorescent protein variants fused to the single-chain fragment variable (scFv) and uncovered photobleaching, aggregation, and intensity disparities. Using different strengths of germline and somatic drivers, we determined that the availability of the scFv is critical in order to detect translation throughout development. We introduced a new translation imaging method based on a nanobody/tag system named ALFA-array, allowing the sensitive and simultaneous detection of the translation of several distinct mRNA species. Finally, we developed a largely improved RNA imaging system based on an MCP-tdStaygold fusion.
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Affiliation(s)
- Maëlle Bellec
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, 34293 Montpellier, France
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Ruoyu Chen
- Vilcek Institute of Graduate Studies, NYU School of Medicine, New York 10016, USA
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Jana Dhayni
- Institut de Génétique Humaine, University of Montpellier, CNRS, 34396 Montpellier, France
| | - Antonello Trullo
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, 34293 Montpellier, France
| | - Damien Avinens
- Institut de Recherche en Infectiologie de Montpellier, CNRS UMR 9004, University of Montpellier, Montpellier, 34293 Cedex 5, France
| | - Hussein Karaki
- Institut de Génétique Humaine, University of Montpellier, CNRS, 34396 Montpellier, France
| | - Flavia Mazzarda
- Institut de Génétique Humaine, University of Montpellier, CNRS, 34396 Montpellier, France
| | - Helene Lenden-Hasse
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, 34293 Montpellier, France
| | - Cyril Favard
- Institut de Recherche en Infectiologie de Montpellier, CNRS UMR 9004, University of Montpellier, Montpellier, 34293 Cedex 5, France
| | - Ruth Lehmann
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Edouard Bertrand
- Institut de Génétique Humaine, University of Montpellier, CNRS, 34396 Montpellier, France
| | - Mounia Lagha
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, 34293 Montpellier, France
| | - Jeremy Dufourt
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, 34293 Montpellier, France
- Institut de Recherche en Infectiologie de Montpellier, CNRS UMR 9004, University of Montpellier, Montpellier, 34293 Cedex 5, France
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2
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Douvdevany G, Erlich I, Haimovich-Caspi L, Mashiah T, Prondzynski M, Pricolo MR, Alegre-Cebollada J, Linke WA, Carrier L, Kehat I. Imaging of Existing and Newly Translated Proteins Elucidates Mechanisms of Sarcomere Turnover. Circ Res 2024; 135:474-487. [PMID: 38962864 DOI: 10.1161/circresaha.123.323819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 06/28/2024] [Indexed: 07/05/2024]
Abstract
BACKGROUND How the sarcomeric complex is continuously turned over in long-living cardiomyocytes is unclear. According to the prevailing model of sarcomere maintenance, sarcomeres are maintained by cytoplasmic soluble protein pools with free recycling between pools and sarcomeres. METHODS We imaged and quantified the turnover of expressed and endogenous sarcomeric proteins, including the giant protein titin, in cardiomyocytes in culture and in vivo, at the single cell and at the single sarcomere level using pulse-chase labeling of Halo-tagged proteins with covalent ligands. RESULTS We disprove the prevailing protein pool model and instead show an ordered mechanism in which only newly translated proteins enter the sarcomeric complex while older ones are removed and degraded. We also show that degradation is independent of protein age and that proteolytic extraction is a rate-limiting step in the turnover. We show that replacement of sarcomeric proteins occurs at a similar rate within cells and across the heart and is slower in adult cells. CONCLUSIONS Our findings establish a unidirectional replacement model for cardiac sarcomeres subunit replacement and identify their turnover principles.
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Affiliation(s)
- Guy Douvdevany
- The Rappaport Family Institute and the Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel (G.D., I.E., L.H.-C., T.M., I.K.)
| | - Itai Erlich
- The Rappaport Family Institute and the Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel (G.D., I.E., L.H.-C., T.M., I.K.)
| | - Lilac Haimovich-Caspi
- The Rappaport Family Institute and the Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel (G.D., I.E., L.H.-C., T.M., I.K.)
| | - Tomer Mashiah
- The Rappaport Family Institute and the Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel (G.D., I.E., L.H.-C., T.M., I.K.)
| | - Maksymilian Prondzynski
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Germany (M.P., L.C.)
- German Centre for Cardiovascular Research, partner site Hamburg/Kiel/Lübeck, Germany (M.P., L.C.)
- Now with Department of Cardiology, Boston Children's Hospital, Harvard Medical School, Boston, MA (M.P.)
| | - Maria Rosaria Pricolo
- Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (M.R.P., J.A.-C.)
| | | | - Wolfgang A Linke
- Institute of Physiology II, University of Munster, Germany (W.A.L.)
| | - Lucie Carrier
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Germany (M.P., L.C.)
- German Centre for Cardiovascular Research, partner site Hamburg/Kiel/Lübeck, Germany (M.P., L.C.)
| | - Izhak Kehat
- The Rappaport Family Institute and the Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel (G.D., I.E., L.H.-C., T.M., I.K.)
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3
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Xu M, Wang H, Tian X, Li B, Wang S, Zhao X, He H. Opsin-Free Activation of Bmp Receptors by a Femtosecond Laser. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2308072. [PMID: 38239021 PMCID: PMC10933676 DOI: 10.1002/advs.202308072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 12/13/2023] [Indexed: 03/14/2024]
Abstract
Bone morphogenetic protein (BMP) signaling plays a vital role in differentiation, organogenesis, and various cell processes. As a member of TGF-β superfamily, the BMP initiation usually accompanies crosstalk with other signaling pathways and simultaneously activates some of them. It is quite challenging to solely initiate an individual pathway. In this study, an opsin-free optical method to specifically activate BMP receptors (BMPR) and subsequent pSmad1/5/8 cascades by a single-time scan of a tightly-focused femtosecond laser in the near infrared range is reported. Via transient two-photon excitation to intrinsic local flavins near the cell membrane, the photoactivation drives conformational changes of preformed BMPR complexes to enable their bonding and phosphorylation of the GS domain in BMPR-I by BMPR-II. The pSmad1/5/8 signaling is initiated by this method, while p38 and pSmad2 are rarely perturbed. Based on a microscopic system, primary adipose-derived stem cells in an area of 420 × 420 µm2 are photoactivated by a single-time laser scanning for 1.5 s and exhibit pSmad1/5/8 upregulation and osteoblastic differentiation after 21 days. Hence, an opsin-free, specific, and noninvasive optical method to initiate BMP signaling, easily accomplished by a two-photon microscope system is reported.
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Affiliation(s)
- Manjun Xu
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
| | - Haipeng Wang
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
| | - Xiaoying Tian
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
| | - Bingyi Li
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
| | - Shaoyang Wang
- School of Biomedical EngineeringHainan UniversityHaikou570228China
| | - Xiaohui Zhao
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
| | - Hao He
- School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai200031China
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4
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Shao Y, Shu X, Lu Y, Zhu W, Li R, Fu H, Li C, Sun W, Li Z, Zhang Y, Cao X, Ye X, Ajiboye E, Zhao B, Zhang L, Wu H, Feng XH, Yang B, Lu H. A chaperone-like function of FUS ensures TAZ condensate dynamics and transcriptional activation. Nat Cell Biol 2024; 26:86-99. [PMID: 38172614 DOI: 10.1038/s41556-023-01309-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 11/09/2023] [Indexed: 01/05/2024]
Abstract
The Hippo pathway has important roles in organ development, tissue homeostasis and tumour growth. Its downstream effector TAZ is a transcriptional coactivator that promotes target gene expression through the formation of biomolecular condensates. However, the mechanisms that regulate the biophysical properties of TAZ condensates to enable Hippo signalling are not well understood. Here using chemical crosslinking combined with an unbiased proteomics approach, we show that FUS associates with TAZ condensates and exerts a chaperone-like effect to maintain their proper liquidity and robust transcriptional activity. Mechanistically, the low complexity sequence domain of FUS targets the coiled-coil domain of TAZ in a phosphorylation-regulated manner, which ensures the liquidity and dynamicity of TAZ condensates. In cells lacking FUS, TAZ condensates transition into gel-like or solid-like assembles with immobilized TAZ, which leads to reduced expression of target genes and inhibition of pro-tumorigenic activity. Thus, our findings identify a chaperone-like function of FUS in Hippo regulation and demonstrate that appropriate biophysical properties of transcriptional condensates are essential for gene activation.
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Affiliation(s)
- Yangqing Shao
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xin Shu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
| | - Yi Lu
- Tongji University Cancer Center, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Wenxuan Zhu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Ran Li
- The Eighth Affiliated Hospital, Sun Yat-Sen University, Shenzhen, China
| | - Huanyi Fu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Chengyu Li
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Wei Sun
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
| | - Zhuo Li
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Yitong Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xiaolei Cao
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xifu Ye
- Tongji University Cancer Center, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Emmanuel Ajiboye
- Department of Chemistry and Biochemistry, Wichita State University, Wichita, KS, USA
| | - Bin Zhao
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
- The MOE Key Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Center for Life Sciences, Shaoxing Institute, Zhejiang University, Shaoxing, China
| | - Long Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
- The MOE Key Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Haifan Wu
- Department of Chemistry and Biochemistry, Wichita State University, Wichita, KS, USA
| | - Xin-Hua Feng
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
- The MOE Key Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
- Center for Life Sciences, Shaoxing Institute, Zhejiang University, Shaoxing, China
| | - Bing Yang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China.
- Cancer Center, Zhejiang University, Hangzhou, China.
| | - Huasong Lu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China.
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5
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Zou CX, Ma ZH, Jiang ZD, Pan ZQ, Xu DD, Suo F, Shao GC, Dong MQ, Du LL. The ortholog of human REEP1-4 is required for autophagosomal enclosure of ER-phagy/nucleophagy cargos in fission yeast. PLoS Biol 2023; 21:e3002372. [PMID: 37939137 PMCID: PMC10659188 DOI: 10.1371/journal.pbio.3002372] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 11/20/2023] [Accepted: 10/10/2023] [Indexed: 11/10/2023] Open
Abstract
Selective macroautophagy of the endoplasmic reticulum (ER) and the nucleus, known as ER-phagy and nucleophagy, respectively, are processes whose mechanisms remain inadequately understood. Through an imaging-based screen, we find that in the fission yeast Schizosaccharomyces pombe, Yep1 (also known as Hva22 or Rop1), the ortholog of human REEP1-4, is essential for ER-phagy and nucleophagy but not for bulk autophagy. In the absence of Yep1, the initial phase of ER-phagy and nucleophagy proceeds normally, with the ER-phagy/nucleophagy receptor Epr1 coassembling with Atg8. However, ER-phagy/nucleophagy cargos fail to reach the vacuole. Instead, nucleus- and cortical-ER-derived membrane structures not enclosed within autophagosomes accumulate in the cytoplasm. Intriguingly, the outer membranes of nucleus-derived structures remain continuous with the nuclear envelope-ER network, suggesting a possible outer membrane fission defect during cargo separation from source compartments. We find that the ER-phagy role of Yep1 relies on its abilities to self-interact and shape membranes and requires its C-terminal amphipathic helices. Moreover, we show that human REEP1-4 and budding yeast Atg40 can functionally substitute for Yep1 in ER-phagy, and Atg40 is a divergent ortholog of Yep1 and REEP1-4. Our findings uncover an unexpected mechanism governing the autophagosomal enclosure of ER-phagy/nucleophagy cargos and shed new light on the functions and evolution of REEP family proteins.
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Affiliation(s)
- Chen-Xi Zou
- National Institute of Biological Sciences, Beijing, China
- College of Life Sciences, Beijing Normal University, Beijing, China
| | - Zhu-Hui Ma
- National Institute of Biological Sciences, Beijing, China
| | - Zhao-Di Jiang
- National Institute of Biological Sciences, Beijing, China
| | - Zhao-Qian Pan
- National Institute of Biological Sciences, Beijing, China
| | - Dan-Dan Xu
- National Institute of Biological Sciences, Beijing, China
| | - Fang Suo
- National Institute of Biological Sciences, Beijing, China
| | - Guang-Can Shao
- National Institute of Biological Sciences, Beijing, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences, Beijing, China
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
| | - Li-Lin Du
- National Institute of Biological Sciences, Beijing, China
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
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6
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Kenworthy AK. What's past is prologue: FRAP keeps delivering 50 years later. Biophys J 2023; 122:3577-3586. [PMID: 37218127 PMCID: PMC10541474 DOI: 10.1016/j.bpj.2023.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/03/2023] [Accepted: 05/11/2023] [Indexed: 05/24/2023] Open
Abstract
Fluorescence recovery after photobleaching (FRAP) has emerged as one of the most widely utilized techniques to quantify binding and diffusion kinetics of biomolecules in biophysics. Since its inception in the mid-1970s, FRAP has been used to address an enormous array of questions including the characteristic features of lipid rafts, how cells regulate the viscosity of their cytoplasm, and the dynamics of biomolecules inside condensates formed by liquid-liquid phase separation. In this perspective, I briefly summarize the history of the field and discuss why FRAP has proven to be so incredibly versatile and popular. Next, I provide an overview of the extensive body of knowledge that has emerged on best practices for quantitative FRAP data analysis, followed by some recent examples of biological lessons learned using this powerful approach. Finally, I touch on new directions and opportunities for biophysicists to contribute to the continued development of this still-relevant research tool.
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Affiliation(s)
- Anne K Kenworthy
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia.
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7
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Cai N, Lai ACK, Liao K, Corridon PR, Graves DJ, Chan V. Recent Advances in Fluorescence Recovery after Photobleaching for Decoupling Transport and Kinetics of Biomacromolecules in Cellular Physiology. Polymers (Basel) 2022; 14:1913. [PMID: 35567083 PMCID: PMC9105003 DOI: 10.3390/polym14091913] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/27/2022] [Accepted: 04/29/2022] [Indexed: 12/16/2022] Open
Abstract
Among the new molecular tools available to scientists and engineers, some of the most useful include fluorescently tagged biomolecules. Tools, such as green fluorescence protein (GFP), have been applied to perform semi-quantitative studies on biological signal transduction and cellular structural dynamics involved in the physiology of healthy and disease states. Such studies focus on drug pharmacokinetics, receptor-mediated endocytosis, nuclear mechanobiology, viral infections, and cancer metastasis. In 1976, fluorescence recovery after photobleaching (FRAP), which involves the monitoring of fluorescence emission recovery within a photobleached spot, was developed. FRAP allowed investigators to probe two-dimensional (2D) diffusion of fluorescently-labelled biomolecules. Since then, FRAP has been refined through the advancements of optics, charged-coupled-device (CCD) cameras, confocal microscopes, and molecular probes. FRAP is now a highly quantitative tool used for transport and kinetic studies in the cytosol, organelles, and membrane of a cell. In this work, the authors intend to provide a review of recent advances in FRAP. The authors include epifluorescence spot FRAP, total internal reflection (TIR)/FRAP, and confocal microscope-based FRAP. The underlying mathematical models are also described. Finally, our understanding of coupled transport and kinetics as determined by FRAP will be discussed and the potential for future advances suggested.
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Affiliation(s)
- Ning Cai
- Wuhan Institute of Technology, School of Chemical Engineering and Pharmacy, Wuhan 430073, China;
| | - Alvin Chi-Keung Lai
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong 999077, China;
| | - Kin Liao
- Department of Aerospace Engineering, Khalifa University of Science and Technology, Abu Dhabi P.O. Box 127788, United Arab Emirates;
| | - Peter R. Corridon
- Department of Physiology and Immunology, Khalifa University of Science and Technology, Abu Dhabi P.O. Box 127788, United Arab Emirates;
- Healthcare Engineering Innovation Center, Khalifa University of Science and Technology, Abu Dhabi P.O. Box 127788, United Arab Emirates
- Center for Biotechnology, Khalifa University of Science and Technology, Abu Dhabi P.O. Box 127788, United Arab Emirates
| | - David J. Graves
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA;
| | - Vincent Chan
- Department of Biomedical Engineering, Khalifa University of Science and Technology, Abu Dhabi P.O. Box 127788, United Arab Emirates
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Subcellular Dynamics of a Conserved Bacterial Polar Scaffold Protein. Genes (Basel) 2022; 13:genes13020278. [PMID: 35205323 PMCID: PMC8872289 DOI: 10.3390/genes13020278] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/27/2022] [Accepted: 01/28/2022] [Indexed: 02/05/2023] Open
Abstract
In order to survive, bacterial cells rely on precise spatiotemporal organization and coordination of essential processes such as cell growth, chromosome segregation, and cell division. Given the general lack of organelles, most bacteria are forced to depend on alternative localization mechanisms, such as, for example, geometrical cues. DivIVA proteins are widely distributed in mainly Gram-positive bacteria and were shown to bind the membrane, typically in regions of strong negative curvature, such as the cell poles and division septa. Here, they have been shown to be involved in a multitude of processes: from apical cell growth and chromosome segregation in actinobacteria to sporulation and inhibition of division re-initiation in firmicutes. Structural analyses revealed that DivIVA proteins can form oligomeric assemblies that constitute a scaffold for recruitment of other proteins. However, it remained unclear whether interaction with partner proteins influences DivIVA dynamics. Using structured illumination microscopy (SIM), single-particle tracking (SPT) microscopy, and fluorescent recovery after photobleaching (FRAP) experiments, we show that DivIVA from Corynebacterium glutamicum is mobilized by its binding partner ParB. In contrast, we show that the interaction between Bacillus subtilis DivIVA and its partner protein MinJ reduces DivIVA mobility. Furthermore, we show that the loss of the rod-shape leads to an increase in DivIVA dynamics in both organisms. Taken together, our study reveals the modulation of the polar scaffold protein by protein interactors and cell morphology. We reason that this leads to a very simple, yet robust way for actinobacteria to maintain polar growth and their rod-shape. In B. subtilis, however, the DivIVA protein is tailored towards a more dynamic function that allows quick relocalization from poles to septa upon division.
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9
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Warrington SJ, Strutt H, Strutt D. Use of Fluorescence Recovery After Photobleaching (FRAP) to Measure In Vivo Dynamics of Cell Junction-Associated Polarity Proteins. Methods Mol Biol 2022; 2438:1-30. [PMID: 35147932 DOI: 10.1007/978-1-0716-2035-9_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Here, we present a detailed protocol for fluorescence recovery after photobleaching (FRAP) to measure the dynamics of junctional populations of proteins in living tissue. Specifically, we describe how to perform FRAP in Drosophila pupal wings on fluorescently tagged core planar polarity proteins, which exhibit relatively slow junctional turnover. We provide a step-by-step practical guide to performing FRAP, and list a series of controls and optimizations to do before conducting a FRAP experiment. Finally, we describe how to present the FRAP data for publication.
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Affiliation(s)
| | - Helen Strutt
- School of Biosciences, University of Sheffield, Sheffield, UK
| | - David Strutt
- School of Biosciences, University of Sheffield, Sheffield, UK.
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10
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Greig J, Bulgakova NA. Fluorescence Recovery After Photobleaching to Study the Dynamics of Membrane-Bound Proteins In Vivo Using the Drosophila Embryo. Methods Mol Biol 2021; 2179:145-159. [PMID: 32939719 DOI: 10.1007/978-1-0716-0779-4_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The epithelial-to-mesenchymal transition is a highly dynamic cell process and tools such as fluorescence recovery after photobleaching (FRAP), which allow the study of rapid protein dynamics, enable the following of this process in vivo. This technique uses a short intense pulse of photons to disrupt the fluorescence of a tagged protein in a region of a sample. The fluorescent signal intensity after this bleaching is then recorded and the signal recovery used to provide an indicator of the dynamics of the protein of interest. This technique can be applied to any fluorescently tagged protein, but membrane-bound proteins present an interesting challenge as they are spatially confined and subject to specialized cellular trafficking. Several methods of analysis can be applied which can disentangle these various processes and enable the extraction of information from the recovery curves. Here we describe this technique when applied to the quantification of the plasma membrane-bound E-cadherin protein in vivo using the epidermis of the late embryo of Drosophila melanogaster (Drosophila) as an example of this technique.
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Affiliation(s)
- Joshua Greig
- Department of Biomedical Science and Bateson Centre, The University of Sheffield, Sheffield, UK
| | - Natalia A Bulgakova
- Department of Biomedical Science and Bateson Centre, The University of Sheffield, Sheffield, UK.
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11
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Kaňa R, Steinbach G, Sobotka R, Vámosi G, Komenda J. Fast Diffusion of the Unassembled PetC1-GFP Protein in the Cyanobacterial Thylakoid Membrane. Life (Basel) 2020; 11:life11010015. [PMID: 33383642 PMCID: PMC7823997 DOI: 10.3390/life11010015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 12/17/2020] [Accepted: 12/20/2020] [Indexed: 01/08/2023] Open
Abstract
Biological membranes were originally described as a fluid mosaic with uniform distribution of proteins and lipids. Later, heterogeneous membrane areas were found in many membrane systems including cyanobacterial thylakoids. In fact, cyanobacterial pigment-protein complexes (photosystems, phycobilisomes) form a heterogeneous mosaic of thylakoid membrane microdomains (MDs) restricting protein mobility. The trafficking of membrane proteins is one of the key factors for long-term survival under stress conditions, for instance during exposure to photoinhibitory light conditions. However, the mobility of unbound 'free' proteins in thylakoid membrane is poorly characterized. In this work, we assessed the maximal diffusional ability of a small, unbound thylakoid membrane protein by semi-single molecule FCS (fluorescence correlation spectroscopy) method in the cyanobacterium Synechocystis sp. PCC6803. We utilized a GFP-tagged variant of the cytochrome b6f subunit PetC1 (PetC1-GFP), which was not assembled in the b6f complex due to the presence of the tag. Subsequent FCS measurements have identified a very fast diffusion of the PetC1-GFP protein in the thylakoid membrane (D = 0.14 - 2.95 µm2s-1). This means that the mobility of PetC1-GFP was comparable with that of free lipids and was 50-500 times higher in comparison to the mobility of proteins (e.g., IsiA, LHCII-light-harvesting complexes of PSII) naturally associated with larger thylakoid membrane complexes like photosystems. Our results thus demonstrate the ability of free thylakoid-membrane proteins to move very fast, revealing the crucial role of protein-protein interactions in the mobility restrictions for large thylakoid protein complexes.
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Affiliation(s)
- Radek Kaňa
- Center ALGATECH, Institute of Microbiology of the Czech Academy of Sciences, 37901 Třeboň, Czech Republic; (R.S.); (J.K.)
- Correspondence:
| | - Gábor Steinbach
- Institute of Biophysics, Biological Research Center, 6726 Szeged, Hungary;
| | - Roman Sobotka
- Center ALGATECH, Institute of Microbiology of the Czech Academy of Sciences, 37901 Třeboň, Czech Republic; (R.S.); (J.K.)
| | - György Vámosi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
| | - Josef Komenda
- Center ALGATECH, Institute of Microbiology of the Czech Academy of Sciences, 37901 Třeboň, Czech Republic; (R.S.); (J.K.)
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12
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Zhang X, Mariano CF, Ando Y, Shen K. Bioengineering tools for probing intracellular events in T lymphocytes. WIREs Mech Dis 2020; 13:e1510. [PMID: 33073545 DOI: 10.1002/wsbm.1510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 11/11/2022]
Abstract
T lymphocytes are the central coordinator and executor of many immune functions. The activation and function of T lymphocytes are mediated through the engagement of cell surface receptors and regulated by a myriad of intracellular signaling network. Bioengineering tools, including imaging modalities and fluorescent probes, have been developed and employed to elucidate the cellular events throughout the functional lifespan of T cells. A better understanding of these events can broaden our knowledge in the immune systems biology, as well as accelerate the development of effective diagnostics and immunotherapies. Here we review the commonly used and recently developed techniques and probes for monitoring T lymphocyte intracellular events, following the order of intracellular events in T cells from activation, signaling, metabolism to apoptosis. The techniques introduced here can be broadly applied to other immune cells and cell systems. This article is categorized under: Immune System Diseases > Molecular and Cellular Physiology Immune System Diseases > Biomedical Engineering Infectious Diseases > Biomedical Engineering.
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Affiliation(s)
- Xinyuan Zhang
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Chelsea F Mariano
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Yuta Ando
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
| | - Keyue Shen
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA.,Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California, USA.,USC Stem Cell, University of Southern California, Los Angeles, California, USA
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13
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Cadar AG, Feaster TK, Bersell KR, Wang L, Hong T, Balsamo JA, Zhang Z, Chun YW, Nam YJ, Gotthardt M, Knollmann BC, Roden DM, Lim CC, Hong CC. Real-time visualization of titin dynamics reveals extensive reversible photobleaching in human induced pluripotent stem cell-derived cardiomyocytes. Am J Physiol Cell Physiol 2020; 318:C163-C173. [PMID: 31747312 PMCID: PMC6985833 DOI: 10.1152/ajpcell.00107.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 11/08/2019] [Accepted: 11/08/2019] [Indexed: 12/17/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) has been useful in delineating cardiac myofilament biology, and innovations in fluorophore chemistry have expanded the array of microscopic assays used. However, one assumption in FRAP is the irreversible photobleaching of fluorescent proteins after laser excitation. Here we demonstrate reversible photobleaching regarding the photoconvertible fluorescent protein mEos3.2. We used CRISPR/Cas9 genome editing in human induced pluripotent stem cells (hiPSCs) to knock-in mEos3.2 into the COOH terminus of titin to visualize sarcomeric titin incorporation and turnover. Upon cardiac induction, the titin-mEos3.2 fusion protein is expressed and integrated in the sarcomeres of hiPSC-derived cardiomyocytes (CMs). STORM imaging shows M-band clustered regions of bound titin-mEos3.2 with few soluble titin-mEos3.2 molecules. FRAP revealed a baseline titin-mEos3.2 fluorescence recovery of 68% and half-life of ~1.2 h, suggesting a rapid exchange of sarcomeric titin with soluble titin. However, paraformaldehyde-fixed and permeabilized titin-mEos3.2 hiPSC-CMs surprisingly revealed a 55% fluorescence recovery. Whole cell FRAP analysis in paraformaldehyde-fixed, cycloheximide-treated, and untreated titin-mEos3.2 hiPSC-CMs displayed no significant differences in fluorescence recovery. FRAP in fixed HEK 293T expressing cytosolic mEos3.2 demonstrates a 58% fluorescence recovery. These data suggest that titin-mEos3.2 is subject to reversible photobleaching following FRAP. Using a mouse titin-eGFP model, we demonstrate that no reversible photobleaching occurs. Our results reveal that reversible photobleaching accounts for the majority of titin recovery in the titin-mEos3.2 hiPSC-CM model and should warrant as a caution in the extrapolation of reliable FRAP data from specific fluorescent proteins in long-term cell imaging.
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Affiliation(s)
- Adrian G Cadar
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Tromondae K Feaster
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Kevin R Bersell
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Lili Wang
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - TingTing Hong
- Smidt Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
| | - Joseph A Balsamo
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Zhentao Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Young Wook Chun
- Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Young-Jae Nam
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Björn C Knollmann
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Dan M Roden
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Chee C Lim
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Charles C Hong
- Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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14
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Femia MR, Evans RM, Zhang J, Sun X, Lebegue CJ, Roggero VR, Allison LA. Mediator subunit MED1 modulates intranuclear dynamics of the thyroid hormone receptor. J Cell Biochem 2019; 121:2909-2926. [PMID: 31692077 DOI: 10.1002/jcb.29532] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 10/10/2019] [Indexed: 12/26/2022]
Abstract
The thyroid hormone receptors (TRs) mediate thyroid hormone (T3 )-dependent gene expression. The nuclear import and export signals that direct TR shuttling are well characterized, but little is known about factors modulating nuclear retention. We used fluorescence-based nucleocytoplasmic scoring and fluorescence recovery after photobleaching in transfected cells to investigate whether Mediator subunits MED1 and MED13 play a role in nuclear retention of TR. When MED1 was overexpressed, there was a striking shift towards a greater nuclear localization of TRβ1 and the oncoprotein v-ErbA, subtypes with cytosolic populations at steady-state, and TRβ1 intranuclear mobility was reduced. For TRα1, there was no observable change in its predominantly nuclear distribution pattern or mobility. Consistent with a role for MED1 in nuclear retention, the cytosolic TRα1 and TRβ1 population were significantly greater in MED1-/- cells, compared with MED1+/+ cells. Exposure to T3 and epidermal growth factor, which induces MED1 phosphorylation, also altered TR intranuclear dynamics. Overexpression of miR-208a, which downregulates MED13, led to a more cytosolic distribution of nuclear-localized TRα1; however, overexpression of MED13 had no effect on TRβ1 localization. The known binding site of MED1 overlaps with a transactivation domain and nuclear export signal in helix 12 of TR's ligand-binding domain (LBD). Coimmunoprecipitation assays demonstrated that TR's LBD interacts directly with exportins 5 and 7, suggesting that binding of exportins and MED1 to TR may be mutually exclusive. Collectively, our data provide evidence that MED1 promotes nuclear retention of TR, and highlight the dual functionality of helix 12 in TR transactivation and nuclear export.
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Affiliation(s)
- Matthew R Femia
- Department of Biology, William and Mary, Williamsburg, Viginia
| | | | - Jibo Zhang
- Department of Biology, William and Mary, Williamsburg, Viginia
| | - Xiaopeng Sun
- Department of Biology, William and Mary, Williamsburg, Viginia
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15
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Boeri L, Albani D, Raimondi MT, Jacchetti E. Mechanical regulation of nucleocytoplasmic translocation in mesenchymal stem cells: characterization and methods for investigation. Biophys Rev 2019; 11:817-831. [PMID: 31628607 PMCID: PMC6815268 DOI: 10.1007/s12551-019-00594-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 09/03/2019] [Indexed: 02/07/2023] Open
Abstract
Mesenchymal stem cells (MSCs) have immune-modulatory and tissue-regenerative properties that make them a suitable and promising tool for cell-based therapy application. Since the bio-chemo-mechanical environment influences MSC fate and behavior, the understanding of the mechanosensors involved in the transduction of mechanical inputs into chemical signals could be pivotal. In this context, the nuclear pore complex is a molecular machinery that is believed to have a key role in force transmission and in nucleocytoplasmic shuttling regulation. To fully understand the nuclear pore complex role and the nucleocytoplasmic transport dynamics, recent advancements in fluorescence microscopy provided the possibility to study passive and facilitated nuclear transports also in mechanically stimulated cell culture conditions. Here, we review the current available methods for the investigation of nucleocytoplasmic shuttling, including photo-perturbation-based approaches, fluorescence correlation spectroscopy, and single-particle tracking techniques. For each method, we analyze the advantages, disadvantages, and technical limitations. Finally, we summarize the recent knowledge on mechanical regulation of nucleocytoplasmic translocation in MSC, the relevant progresses made so far, and the future perspectives in the field.
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Affiliation(s)
- Lucia Boeri
- Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20123, Milan, Italy
| | - Diego Albani
- Department of Neuroscience, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy
| | - Manuela Teresa Raimondi
- Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20123, Milan, Italy
| | - Emanuela Jacchetti
- Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20123, Milan, Italy.
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16
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Abstract
Fluorescence recovery after photobleaching (FRAP) is an important tool used by cell biologists to study the diffusion and binding kinetics of vesicles, proteins, and other molecules in the cytoplasm, nucleus, or cell membrane. Although many FRAP models have been developed over the past decades, the influence of the complex boundaries of 3D cellular geometries on the recovery curves, in conjunction with regions of interest and optical effects (imaging, photobleaching, photoswitching, and scanning), has not been well studied. Here, we developed a 3D computational model of the FRAP process that incorporates particle diffusion, cell boundary effects, and the optical properties of the scanning confocal microscope, and validated this model using the tip-growing cells of Physcomitrella patens. We then show how these cell boundary and optical effects confound the interpretation of FRAP recovery curves, including the number of dynamic states of a given fluorophore, in a wide range of cellular geometries-both in two and three dimensions-namely nuclei, filopodia, and lamellipodia of mammalian cells, and in cell types such as the budding yeast, Saccharomyces pombe, and tip-growing plant cells. We explored the performance of existing analytical and algorithmic FRAP models in these various cellular geometries, and determined that the VCell VirtualFRAP tool provides the best accuracy to measure diffusion coefficients. Our computational model is not limited only to these cells types, but can easily be extended to other cellular geometries via the graphical Java-based application we also provide. This particle-based simulation-called the Digital Confocal Microscopy Suite or DCMS-can also perform fluorescence dynamics assays, such as number and brightness, fluorescence correlation spectroscopy, and raster image correlation spectroscopy, and could help shape the way these techniques are interpreted.
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17
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Li Y, Merkel CD, Zeng X, Heier JA, Cantrell PS, Sun M, Stolz DB, Watkins SC, Yates NA, Kwiatkowski AV. The N-cadherin interactome in primary cardiomyocytes as defined using quantitative proximity proteomics. J Cell Sci 2019; 132:jcs.221606. [PMID: 30630894 PMCID: PMC6382013 DOI: 10.1242/jcs.221606] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 12/24/2018] [Indexed: 12/11/2022] Open
Abstract
The junctional complexes that couple cardiomyocytes must transmit the mechanical forces of contraction while maintaining adhesive homeostasis. The adherens junction (AJ) connects the actomyosin networks of neighboring cardiomyocytes and is required for proper heart function. Yet little is known about the molecular composition of the cardiomyocyte AJ or how it is organized to function under mechanical load. Here, we define the architecture, dynamics and proteome of the cardiomyocyte AJ. Mouse neonatal cardiomyocytes assemble stable AJs along intercellular contacts with organizational and structural hallmarks similar to mature contacts. We combine quantitative mass spectrometry with proximity labeling to identify the N-cadherin (CDH2) interactome. We define over 350 proteins in this interactome, nearly 200 of which are unique to CDH2 and not part of the E-cadherin (CDH1) interactome. CDH2-specific interactors comprise primarily adaptor and adhesion proteins that promote junction specialization. Our results provide novel insight into the cardiomyocyte AJ and offer a proteomic atlas for defining the molecular complexes that regulate cardiomyocyte intercellular adhesion. This article has an associated First Person interview with the first authors of the paper.
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Affiliation(s)
- Yang Li
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Chelsea D Merkel
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Xuemei Zeng
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Jonathon A Heier
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Pamela S Cantrell
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Mai Sun
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Donna B Stolz
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Nathan A Yates
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA.,University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Adam V Kwiatkowski
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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18
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Morisaki T, Stasevich TJ. Quantifying Single mRNA Translation Kinetics in Living Cells. Cold Spring Harb Perspect Biol 2018; 10:a032078. [PMID: 30385605 PMCID: PMC6211384 DOI: 10.1101/cshperspect.a032078] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
One of the last hurdles to quantifying the full central dogma of molecular biology in living cells with single-molecule resolution has been the imaging of single messenger RNA (mRNA) translation. Here we describe how recent advances in protein tagging and imaging technologies are being used to precisely visualize and quantify the synthesis of nascent polypeptide chains from single mRNA in living cells. We focus on recent applications of repeat-epitope tags and describe how they enable quantification of single mRNA ribosomal densities, translation initiation and elongation rates, and translation site mobility and higher-order structure. Together with complementary live-cell assays to monitor translation using fast-maturing fluorophores and mRNA-binding protein knockoff, single-molecule studies are beginning to uncover striking and unexpected heterogeneity in gene expression at the level of translation.
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Affiliation(s)
- Tatsuya Morisaki
- Institute of Genome Architecture and Function and Department of Biochemistry & Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Timothy J Stasevich
- Institute of Genome Architecture and Function and Department of Biochemistry & Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
- Cell Biology Unit, Institute of Innovative Research, Tokyo Institute of Technology, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
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19
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Glazachev YI, Orlova DY, Řezníčková P, Bártová E. Effective scheme of photolysis of GFP in live cell as revealed with confocal fluorescence microscopy. Phys Biol 2018; 15:036008. [PMID: 29493532 DOI: 10.1088/1478-3975/aab31e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We proposed an effective kinetics scheme of photolysis of green fluorescent protein (GFP) observed in live cells with a commercial confocal fluorescence microscope. We investigated the photolysis of GFP-tagged heterochromatin protein, HP1β-GFP, in live nucleus with the pulse position modulation approach, which has several advantages over the classical pump-and-probe method. At the basis of the proposed scheme lies a process of photoswitching from the native fluorescence state to the intermediate fluorescence state, which has a lower fluorescence yield and recovers back to native state in the dark. This kinetics scheme includes four effective parameters (photoswitching, reverse switching, photodegradation rate constants, and relative brightness of the intermediate state) and covers the time scale from dozens of milliseconds to minutes of the experimental fluorescence kinetics. Additionally, the applicability of the scheme was demonstrated in the cases of continuous irradiation and the classical pump-and-probe approach using numerical calculations and analytical solutions. An interesting finding of experimental data analysis was that the overall photodegradation of GFP proceeds dominantly from the intermediate state, and demonstrated approximately the second-order reaction versus irradiation power. As a practical example, the proposed scheme elucidates the artifacts of fluorescence recovery after the photobleaching method, and allows us to propose some suggestions on how to diminish them.
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Affiliation(s)
- Yu I Glazachev
- Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian academy of Science, Novosibirsk 630090, Russia. Author to whom any correspondence should be addressed
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20
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Bibeau JP, Kingsley JL, Furt F, Tüzel E, Vidali L. F-Actin Mediated Focusing of Vesicles at the Cell Tip Is Essential for Polarized Growth. PLANT PHYSIOLOGY 2018; 176:352-363. [PMID: 28972078 PMCID: PMC5761772 DOI: 10.1104/pp.17.00753] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 09/26/2017] [Indexed: 05/18/2023]
Abstract
F-actin has been shown to be essential for tip growth in an array of plant models, including Physcomitrella patens One hypothesis is that diffusion can transport secretory vesicles, while actin plays a regulatory role during secretion. Alternatively, it is possible that actin-based transport is necessary to overcome vesicle transport limitations to sustain secretion. Therefore, a quantitative analysis of diffusion, secretion kinetics, and cell geometry is necessary to clarify the role of actin in polarized growth. Using fluorescence recovery after photobleaching analysis, we first show that secretory vesicles move toward and accumulate at the tip in an actin-dependent manner. We then depolymerized F-actin to decouple vesicle diffusion from actin-mediated transport and measured the diffusion coefficient and concentration of vesicles. Using these values, we constructed a theoretical diffusion-based model for growth, demonstrating that with fast-enough vesicle fusion kinetics, diffusion could support normal cell growth rates. We further refined our model to explore how experimentally extrapolated vesicle fusion kinetics and the size of the secretion zone limit diffusion-based growth. This model predicts that diffusion-mediated growth is dependent on the size of the region of exocytosis at the tip and that diffusion-based growth would be significantly slower than normal cell growth. To further explore the size of the secretion zone, we used a cell wall degradation enzyme cocktail and determined that the secretion zone is smaller than 6 μm in diameter at the tip. Taken together, our results highlight the requirement for active transport in polarized growth and provide important insight into vesicle secretion during tip growth.
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Affiliation(s)
- Jeffrey P Bibeau
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - James L Kingsley
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Fabienne Furt
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Erkan Tüzel
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
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21
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Macháň R, Foo YH, Wohland T. On the Equivalence of FCS and FRAP: Simultaneous Lipid Membrane Measurements. Biophys J 2017; 111:152-61. [PMID: 27410743 DOI: 10.1016/j.bpj.2016.06.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 06/02/2016] [Accepted: 06/02/2016] [Indexed: 10/21/2022] Open
Abstract
Fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP) are widely used methods to determine diffusion coefficients. However, they often do not yield the same results. With the advent of camera-based imaging FCS, which measures the diffusion coefficient in each pixel of an image, and proper bleaching corrections, it is now possible to measure the diffusion coefficient by FRAP and FCS in the exact same images. We thus performed simultaneous FCS and FRAP measurements on supported lipid bilayers and live cell membranes to test how far the two methods differ in their results and whether the methodological differences, in particular the high bleach intensity in FRAP, the bleach corrections, and the fitting procedures in the two methods explain observed differences. Overall, we find that the FRAP bleach intensity does not measurably influence the diffusion in the samples, but that bleach correction and fitting introduce large uncertainties in FRAP. We confirm our results by simulations.
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Affiliation(s)
- Radek Macháň
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
| | - Yong Hwee Foo
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore; Department of Chemistry, National University of Singapore, Singapore.
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22
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Zhang J, Roggero VR, Allison LA. Nuclear Import and Export of the Thyroid Hormone Receptor. VITAMINS AND HORMONES 2017; 106:45-66. [PMID: 29407444 DOI: 10.1016/bs.vh.2017.04.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The thyroid hormone receptors, TRα1 and TRβ1, are members of the nuclear receptor superfamily that forms one of the most abundant classes of transcription factors in multicellular organisms. Although primarily localized to the nucleus, TRα1 and TRβ1 shuttle rapidly between the nucleus and cytoplasm. The fine balance between nuclear import and export of TRs has emerged as a critical control point for modulating thyroid hormone-responsive gene expression. Mutagenesis studies have defined two nuclear localization signal (NLS) motifs that direct nuclear import of TRα1: NLS-1 in the hinge domain and NLS-2 in the N-terminal A/B domain. Three nuclear export signal (NES) motifs reside in the ligand-binding domain. A combined approach of shRNA-mediated knockdown and coimmunoprecipitation assays revealed that nuclear entry of TRα1 is facilitated by importin 7, likely through interactions with NLS-2, and importin β1 and the adapter importin α1 interacting with both NLS-1 and NLS-2. Interestingly, TRβ1 lacks NLS-2 and nuclear import depends solely on the importin α1/β1 heterodimer. Heterokaryon and fluorescence recovery after photobleaching shuttling assays identified multiple exportins that play a role in nuclear export of TRα1, including CRM1 (exportin 1), and exportins 4, 5, and 7. Even single amino acid changes in TRs dramatically alter their intracellular distribution patterns. We conclude that mutations within NLS and NES motifs affect nuclear shuttling activity, and propose that TR mislocalization contributes to the development of some types of cancer and Resistance to Thyroid Hormone syndrome.
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Affiliation(s)
- Jibo Zhang
- College of William and Mary, Williamsburg, VA, United States
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23
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Zhao ZW, White MD, Bissiere S, Levi V, Plachta N. Quantitative imaging of mammalian transcriptional dynamics: from single cells to whole embryos. BMC Biol 2016; 14:115. [PMID: 28010727 PMCID: PMC5180410 DOI: 10.1186/s12915-016-0331-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Probing dynamic processes occurring within the cell nucleus at the quantitative level has long been a challenge in mammalian biology. Advances in bio-imaging techniques over the past decade have enabled us to directly visualize nuclear processes in situ with unprecedented spatial and temporal resolution and single-molecule sensitivity. Here, using transcription as our primary focus, we survey recent imaging studies that specifically emphasize the quantitative understanding of nuclear dynamics in both time and space. These analyses not only inform on previously hidden physical parameters and mechanistic details, but also reveal a hierarchical organizational landscape for coordinating a wide range of transcriptional processes shared by mammalian systems of varying complexity, from single cells to whole embryos.
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Affiliation(s)
- Ziqing W Zhao
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Melanie D White
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Stephanie Bissiere
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Valeria Levi
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Conicet, Buenos Aires, C1428EHA, Argentina
| | - Nicolas Plachta
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore.
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24
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Toro-Nahuelpan M, Müller FD, Klumpp S, Plitzko JM, Bramkamp M, Schüler D. Segregation of prokaryotic magnetosomes organelles is driven by treadmilling of a dynamic actin-like MamK filament. BMC Biol 2016; 14:88. [PMID: 27733152 PMCID: PMC5059902 DOI: 10.1186/s12915-016-0290-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 07/29/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The navigation of magnetotactic bacteria relies on specific intracellular organelles, the magnetosomes, which are membrane-enclosed crystals of magnetite aligned into a linear chain. The magnetosome chain acts as a cellular compass, aligning the cells in the geomagnetic field in order to search for suitable environmental conditions in chemically stratified water columns and sediments. During cytokinesis, magnetosome chains have to be properly positioned, cleaved and separated in order to be evenly passed into daughter cells. In Magnetospirillum gryphiswaldense, the assembly of the magnetosome chain is controlled by the actin-like MamK, which polymerizes into cytoskeletal filaments that are connected to magnetosomes through the acidic MamJ protein. MamK filaments were speculated to recruit the magnetosome chain to cellular division sites, thus ensuring equal organelle inheritance. However, the underlying mechanism of magnetic organelle segregation has remained largely unknown. RESULTS Here, we performed in vivo time-lapse fluorescence imaging to directly track the intracellular movement and dynamics of magnetosome chains as well as photokinetic and ultrastructural analyses of the actin-like cytoskeletal MamK filament. We show that magnetosome chains undergo rapid intracellular repositioning from the new poles towards midcell into the newborn daughter cells, and the driving force for magnetosomes movement is likely provided by the pole-to-midcell treadmilling growth of MamK filaments. We further discovered that splitting and equipartitioning of magnetosome chains occurs with unexpectedly high accuracy, which depends directly on the dynamics of MamK filaments. CONCLUSION We propose a novel mechanism for prokaryotic organelle segregation that, similar to the type-II bacterial partitioning system of plasmids, relies on the action of cytomotive actin-like filaments together with specific connectors, which transport the magnetosome cargo in a fashion reminiscent of eukaryotic actin-organelle transport and segregation mechanisms.
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Affiliation(s)
- Mauricio Toro-Nahuelpan
- Department of Microbiology, University of Bayreuth, 95447, Bayreuth, Germany.,Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Planegg-Martinsried, Germany
| | - Frank D Müller
- Department of Microbiology, University of Bayreuth, 95447, Bayreuth, Germany
| | - Stefan Klumpp
- Department Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany.,Institute for Nonlinear Dynamics, Georg August University Göttingen, Göttingen, Germany
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Planegg-Martinsried, Germany
| | - Marc Bramkamp
- Department of Biology I, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Dirk Schüler
- Department of Microbiology, University of Bayreuth, 95447, Bayreuth, Germany.
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25
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Morisaki T, Lyon K, DeLuca KF, DeLuca JG, English BP, Zhang Z, Lavis LD, Grimm JB, Viswanathan S, Looger LL, Lionnet T, Stasevich TJ. Real-time quantification of single RNA translation dynamics in living cells. Science 2016; 352:1425-9. [PMID: 27313040 DOI: 10.1126/science.aaf0899] [Citation(s) in RCA: 246] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 04/28/2016] [Indexed: 12/14/2022]
Abstract
Although messenger RNA (mRNA) translation is a fundamental biological process, it has never been imaged in real time in vivo with single-molecule precision. To achieve this, we developed nascent chain tracking (NCT), a technique that uses multi-epitope tags and antibody-based fluorescent probes to quantify protein synthesis dynamics at the single-mRNA level. NCT reveals an elongation rate of ~10 amino acids per second, with initiation occurring stochastically every ~30 seconds. Polysomes contain ~1 ribosome every 200 to 900 nucleotides and are globular rather than elongated in shape. By developing multicolor probes, we showed that most polysomes act independently; however, a small fraction (~5%) form complexes in which two distinct mRNAs can be translated simultaneously. The sensitivity and versatility of NCT make it a powerful new tool for quantifying mRNA translation kinetics.
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Affiliation(s)
- Tatsuya Morisaki
- Department of Biochemistry and Molecular Biology and Institute for Genome Architecture and Function, Colorado State University, Fort Collins, CO, USA
| | - Kenneth Lyon
- Department of Biochemistry and Molecular Biology and Institute for Genome Architecture and Function, Colorado State University, Fort Collins, CO, USA
| | - Keith F DeLuca
- Department of Biochemistry and Molecular Biology and Institute for Genome Architecture and Function, Colorado State University, Fort Collins, CO, USA
| | - Jennifer G DeLuca
- Department of Biochemistry and Molecular Biology and Institute for Genome Architecture and Function, Colorado State University, Fort Collins, CO, USA
| | - Brian P English
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Zhengjian Zhang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jonathan B Grimm
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Sarada Viswanathan
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Timothee Lionnet
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Timothy J Stasevich
- Department of Biochemistry and Molecular Biology and Institute for Genome Architecture and Function, Colorado State University, Fort Collins, CO, USA
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26
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Bajanca F, Gonzalez-Perez V, Gillespie SJ, Beley C, Garcia L, Theveneau E, Sear RP, Hughes SM. In vivo dynamics of skeletal muscle Dystrophin in zebrafish embryos revealed by improved FRAP analysis. eLife 2015; 4. [PMID: 26459831 PMCID: PMC4601390 DOI: 10.7554/elife.06541] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 09/10/2015] [Indexed: 12/30/2022] Open
Abstract
Dystrophin forms an essential link between sarcolemma and cytoskeleton, perturbation of which causes muscular dystrophy. We analysed Dystrophin binding dynamics in vivo for the first time. Within maturing fibres of host zebrafish embryos, our analysis reveals a pool of diffusible Dystrophin and complexes bound at the fibre membrane. Combining modelling, an improved FRAP methodology and direct semi-quantitative analysis of bleaching suggests the existence of two membrane-bound Dystrophin populations with widely differing bound lifetimes: a stable, tightly bound pool, and a dynamic bound pool with high turnover rate that exchanges with the cytoplasmic pool. The three populations were found consistently in human and zebrafish Dystrophins overexpressed in wild-type or dmd(ta222a/ta222a) zebrafish embryos, which lack Dystrophin, and in Gt(dmd-Citrine)(ct90a) that express endogenously-driven tagged zebrafish Dystrophin. These results lead to a new model for Dystrophin membrane association in developing muscle, and highlight our methodology as a valuable strategy for in vivo analysis of complex protein dynamics.
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Affiliation(s)
- Fernanda Bajanca
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.,CNRS and Université Paul Sabatier, Toulouse, France
| | | | - Sean J Gillespie
- Department of Physics, University of Surrey, Guildford, United Kingdom
| | - Cyriaque Beley
- Université Versailles Saint-Quentin, Montigny-le-Bretonneux, France.,Laboratoire International Associé-Biologie appliquée aux handicaps neuromusculaires, Centre Scientifique de Monaco, Monaco, Monaco
| | - Luis Garcia
- Université Versailles Saint-Quentin, Montigny-le-Bretonneux, France.,Laboratoire International Associé-Biologie appliquée aux handicaps neuromusculaires, Centre Scientifique de Monaco, Monaco, Monaco
| | | | - Richard P Sear
- Department of Physics, University of Surrey, Guildford, United Kingdom
| | - Simon M Hughes
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom
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27
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Fluorescence recovery after photobleaching in material and life sciences: putting theory into practice. Q Rev Biophys 2015; 48:323-87. [PMID: 26314367 DOI: 10.1017/s0033583515000013] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
AbstractFluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure–interaction–diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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28
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De Los Santos C, Chang CW, Mycek MA, Cardullo RA. FRAP, FLIM, and FRET: Detection and analysis of cellular dynamics on a molecular scale using fluorescence microscopy. Mol Reprod Dev 2015; 82:587-604. [PMID: 26010322 PMCID: PMC4515154 DOI: 10.1002/mrd.22501] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 05/01/2015] [Indexed: 01/01/2023]
Abstract
The combination of fluorescent-probe technology plus modern optical microscopes allows investigators to monitor dynamic events in living cells with exquisite temporal and spatial resolution. Fluorescence recovery after photobleaching (FRAP), for example, has long been used to monitor molecular dynamics both within cells and on cellular surfaces. Although bound by the diffraction limit imposed on all optical microscopes, the combination of digital cameras and the application of fluorescence intensity information on large-pixel arrays have allowed such dynamic information to be monitored and quantified. Fluorescence lifetime imaging microscopy (FLIM), on the other hand, utilizes the information from an ensemble of fluorophores to probe changes in the local environment. Using either fluorescence-intensity or lifetime approaches, fluorescence resonance energy transfer (FRET) microscopy provides information about molecular interactions, with Ångstrom resolution. In this review, we summarize the theoretical framework underlying these methods and illustrate their utility in addressing important problems in reproductive and developmental systems.
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Affiliation(s)
- Carla De Los Santos
- Departments of Biology and Bioengineering, University of California, Riverside, Riverside, CA 92501
| | - Ching-Wei Chang
- Department of Bioengineering, University of California, Berkeley 94720
| | - Mary-Ann Mycek
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Richard A. Cardullo
- Departments of Biology and Bioengineering, University of California, Riverside, Riverside, CA 92501
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29
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Kang M, Andreani M, Kenworthy AK. Validation of Normalizations, Scaling, and Photofading Corrections for FRAP Data Analysis. PLoS One 2015; 10:e0127966. [PMID: 26017223 PMCID: PMC4446327 DOI: 10.1371/journal.pone.0127966] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 04/22/2015] [Indexed: 01/14/2023] Open
Abstract
Fluorescence Recovery After Photobleaching (FRAP) has been a versatile tool to study transport and reaction kinetics in live cells. Since the fluorescence data generated by fluorescence microscopy are in a relative scale, a wide variety of scalings and normalizations are used in quantitative FRAP analysis. Scaling and normalization are often required to account for inherent properties of diffusing biomolecules of interest or photochemical properties of the fluorescent tag such as mobile fraction or photofading during image acquisition. In some cases, scaling and normalization are also used for computational simplicity. However, to our best knowledge, the validity of those various forms of scaling and normalization has not been studied in a rigorous manner. In this study, we investigate the validity of various scalings and normalizations that have appeared in the literature to calculate mobile fractions and correct for photofading and assess their consistency with FRAP equations. As a test case, we consider linear or affine scaling of normal or anomalous diffusion FRAP equations in combination with scaling for immobile fractions. We also consider exponential scaling of either FRAP equations or FRAP data to correct for photofading. Using a combination of theoretical and experimental approaches, we show that compatible scaling schemes should be applied in the correct sequential order; otherwise, erroneous results may be obtained. We propose a hierarchical workflow to carry out FRAP data analysis and discuss the broader implications of our findings for FRAP data analysis using a variety of kinetic models.
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Affiliation(s)
- Minchul Kang
- School of Science, Technology & Engineering Management, St. Thomas University, Miami Gardens, Florida, USA
- * E-mail:
| | - Manuel Andreani
- School of Science, Technology & Engineering Management, St. Thomas University, Miami Gardens, Florida, USA
| | - Anne K. Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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30
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Rosa S, Ntoukakis V, Ohmido N, Pendle A, Abranches R, Shaw P. Cell differentiation and development in Arabidopsis are associated with changes in histone dynamics at the single-cell level. THE PLANT CELL 2014; 26:4821-33. [PMID: 25549670 PMCID: PMC4311217 DOI: 10.1105/tpc.114.133793] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The mechanism whereby the same genome can give rise to different cell types with different gene expression profiles is a fundamental problem in biology. Chromatin organization and dynamics have been shown to vary with altered gene expression in different cultured animal cell types, but there is little evidence yet from whole organisms linking chromatin dynamics with development. Here, we used both fluorescence recovery after photobleaching and two-photon photoactivation to show that in stem cells from Arabidopsis thaliana roots the mobility of the core histone H2B, as judged by exchange dynamics, is lower than in the surrounding cells of the meristem. However, as cells progress from meristematic to fully differentiated, core histones again become less mobile and more strongly bound to chromatin. We show that these transitions are largely mediated by changes in histone acetylation. We further show that altering histone acetylation levels, either in a mutant or by drug treatment, alters both the histone mobility and markers of development and differentiation. We propose that plant stem cells have relatively inactive chromatin, but they keep the potential to divide and differentiate into more dynamic states, and that these states are at least in part determined by histone acetylation levels.
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Affiliation(s)
- Stefanie Rosa
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom Plant Cell Biology Laboratory, Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras 2781-901, Portugal
| | - Vardis Ntoukakis
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Nobuko Ohmido
- Graduate School of Human Development and Environment, Kobe University, Kobe 657-8501, Japan
| | - Ali Pendle
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Rita Abranches
- Plant Cell Biology Laboratory, Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras 2781-901, Portugal
| | - Peter Shaw
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
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31
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Stasevich TJ, Hayashi-Takanaka Y, Sato Y, Maehara K, Ohkawa Y, Sakata-Sogawa K, Tokunaga M, Nagase T, Nozaki N, McNally JG, Kimura H. Regulation of RNA polymerase II activation by histone acetylation in single living cells. Nature 2014; 516:272-5. [PMID: 25252976 DOI: 10.1038/nature13714] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 07/25/2014] [Indexed: 12/31/2022]
Abstract
In eukaryotic cells, post-translational histone modifications have an important role in gene regulation. Starting with early work on histone acetylation, a variety of residue-specific modifications have now been linked to RNA polymerase II (RNAP2) activity, but it remains unclear if these markers are active regulators of transcription or just passive byproducts. This is because studies have traditionally relied on fixed cell populations, meaning temporal resolution is limited to minutes at best, and correlated factors may not actually be present in the same cell at the same time. Complementary approaches are therefore needed to probe the dynamic interplay of histone modifications and RNAP2 with higher temporal resolution in single living cells. Here we address this problem by developing a system to track residue-specific histone modifications and RNAP2 phosphorylation in living cells by fluorescence microscopy. This increases temporal resolution to the tens-of-seconds range. Our single-cell analysis reveals histone H3 lysine-27 acetylation at a gene locus can alter downstream transcription kinetics by as much as 50%, affecting two temporally separate events. First acetylation enhances the search kinetics of transcriptional activators, and later the acetylation accelerates the transition of RNAP2 from initiation to elongation. Signatures of the latter can be found genome-wide using chromatin immunoprecipitation followed by sequencing. We argue that this regulation leads to a robust and potentially tunable transcriptional response.
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Affiliation(s)
- Timothy J Stasevich
- 1] Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan [2] Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA [3] Transcription Imaging Consortium, Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA
| | - Yoko Hayashi-Takanaka
- 1] Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan [2] Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Kawaguchi, Saitama, 332-0012, Japan [3] Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Yuko Sato
- 1] Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan [2] Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Kazumitsu Maehara
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka, 812-8582, Japan
| | - Yasuyuki Ohkawa
- 1] Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Kawaguchi, Saitama, 332-0012, Japan [2] Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka, 812-8582, Japan
| | - Kumiko Sakata-Sogawa
- 1] Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan [2] RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, 230-0045, Japan
| | - Makio Tokunaga
- 1] Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan [2] RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, 230-0045, Japan
| | - Takahiro Nagase
- Department of Biotechnology Research, Kazusa DNA Research Institute, Chiba, 292-0818, Japan
| | | | - James G McNally
- 1] Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA [2] Institute for Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Berlin, 14109, Germany
| | - Hiroshi Kimura
- 1] Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan [2] Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Kawaguchi, Saitama, 332-0012, Japan [3] Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
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32
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Morisaki T, McNally JG. Photoswitching-free FRAP analysis with a genetically encoded fluorescent tag. PLoS One 2014; 9:e107730. [PMID: 25233348 PMCID: PMC4169462 DOI: 10.1371/journal.pone.0107730] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 08/14/2014] [Indexed: 11/18/2022] Open
Abstract
Fluorescence recovery after photobleaching (FRAP) is a widely used imaging technique for measuring protein dynamics in live cells that has provided many important biological insights. Although FRAP presumes that the conversion of a fluorophore from a bright to a dark state is irreversible, GFP as well as other genetically encoded fluorescent proteins now in common use can also exhibit a reversible conversion known as photoswitching. Various studies have shown how photoswitching can cause at least four different artifacts in FRAP, leading to false conclusions about various biological phenomena, including the erroneous identification of anomalous diffusion or the overestimation of the freely diffusible fraction of a cellular protein. Unfortunately, identifying and then correcting these artifacts is difficult. Here we report a new characteristic of an organic fluorophore tetramethylrhodamine bound to the HaloTag protein (TMR-HaloTag), which like GFP can be genetically encoded, but which directly and simply overcomes the artifacts caused by photoswitching in FRAP. We show that TMR exhibits virtually no photoswitching in live cells under typical imaging conditions for FRAP. We also demonstrate that TMR eliminates all of the four reported photoswitching artifacts in FRAP. Finally, we apply this photoswitching-free FRAP with TMR to show that the chromatin decondensation following UV irradiation does not involve loss of nucleosomes from the damaged DNA. In sum, we demonstrate that the TMR Halo label provides a genetically encoded fluorescent tag very well suited for accurate FRAP experiments.
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Affiliation(s)
- Tatsuya Morisaki
- Fluorescence Imaging Group, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - James G. McNally
- Fluorescence Imaging Group, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
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33
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Schuster E, Hermansson AM, Ohgren C, Rudemo M, Lorén N. Interactions and diffusion in fine-stranded β-lactoglobulin gels determined via FRAP and binding. Biophys J 2014; 106:253-62. [PMID: 24411257 DOI: 10.1016/j.bpj.2013.11.2959] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/31/2013] [Accepted: 11/14/2013] [Indexed: 11/28/2022] Open
Abstract
The effects of electrostatic interactions and obstruction by the microstructure on probe diffusion were determined in positively charged hydrogels. Probe diffusion in fine-stranded gels and solutions of β-lactoglobulin at pH 3.5 was determined using fluorescence recovery after photobleaching (FRAP) and binding, which is widely used in biophysics. The microstructures of the β-lactoglobulin gels were characterized using transmission electron microscopy. The effects of probe size and charge (negatively charged Na2-fluorescein (376Da) and weakly anionic 70kDa FITC-dextran), probe concentration (50 to 200 ppm), and β-lactoglobulin concentration (9% to 12% w/w) on the diffusion properties and the electrostatic interaction between the negatively charged probes and the positively charged gels or solutions were evaluated. The results show that the diffusion of negatively charged Na2-fluorescein is strongly influenced by electrostatic interactions in the positively charged β-lactoglobulin systems. A linear relationship between the pseudo-on binding rate constant and the β-lactoglobulin concentration for three different probe concentrations was found. This validates an important assumption of existing biophysical FRAP and binding models, namely that the pseudo-on binding rate constant equals the product of the molecular binding rate constant and the concentration of the free binding sites. Indicators were established to clarify whether FRAP data should be analyzed using a binding-diffusion model or an obstruction-diffusion model.
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Affiliation(s)
- Erich Schuster
- Department of Structure and Material Design, Swedish Institute for Food and Biotechnology, SIK, Göteborg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, Göteborg, Sweden
| | - Anne-Marie Hermansson
- Department of Structure and Material Design, Swedish Institute for Food and Biotechnology, SIK, Göteborg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, Göteborg, Sweden; Department of Applied Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden
| | - Camilla Ohgren
- Department of Structure and Material Design, Swedish Institute for Food and Biotechnology, SIK, Göteborg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, Göteborg, Sweden
| | - Mats Rudemo
- SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, Göteborg, Sweden; Mathematical Sciences, Chalmers University of Technology, and the University of Gothenburg, Göteborg, Sweden
| | - Niklas Lorén
- Department of Structure and Material Design, Swedish Institute for Food and Biotechnology, SIK, Göteborg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, Göteborg, Sweden.
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34
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Wüstner D, Christensen T, Solanko LM, Sage D. Photobleaching kinetics and time-integrated emission of fluorescent probes in cellular membranes. Molecules 2014; 19:11096-130. [PMID: 25076144 PMCID: PMC6271172 DOI: 10.3390/molecules190811096] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 07/04/2014] [Accepted: 07/10/2014] [Indexed: 12/02/2022] Open
Abstract
Since the pioneering work of Hirschfeld, it is known that time-integrated emission (TiEm) of a fluorophore is independent of fluorescence quantum yield and illumination intensity. Practical implementation of this important result for determining exact probe distribution in living cells is often hampered by the presence of autofluorescence. Using kinetic modelling of photobleaching combined with pixel-wise bleach rate fitting of decay models with an updated plugin to the ImageJ program, it is shown that the TiEm of a fluorophore in living cells can be determined exactly from the product of bleaching amplitude and time constant. This applies to mono-exponential bleaching from the first excited singlet and/or triplet state and to multi-exponential combinations of such processes. The TiEm can be used to correct for illumination shading and background autofluorescence without the need for fluorescent test layers or separate imaging of non-stained cells. We apply the method to simulated images and to images of cells, whose membranes were labelled with fluorescent sterols and sphingolipids. Our bleaching model can be extended to include a probability density function (PDF) of intrinsic bleach rate constants with a memory kernel. This approach results in a time-dependent bleach rate coefficient and is exemplified for fluorescent sterols in restricted intracellular environments, like lipid droplets. We show that for small deviations from the classical exponential bleaching, the TiEm of decay functions with rate coefficients remains largely independent of fluorescence lifetime and illumination, and thereby represents a faithful measure of probe distribution.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Tanja Christensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Daniel Sage
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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35
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Abstract
Parkinson's disease and dementia with Lewy bodies are associated with abnormal neuronal aggregation of α-synuclein. However, the mechanisms of aggregation and their relationship to disease are poorly understood. We developed an in vivo multiphoton imaging paradigm to study α-synuclein aggregation in mouse cortex with subcellular resolution. We used a green fluorescent protein-tagged human α-synuclein mouse line that has moderate overexpression levels mimicking human disease. Fluorescence recovery after photobleaching (FRAP) of labeled protein demonstrated that somatic α-synuclein existed primarily in an unbound, soluble pool. In contrast, α-synuclein in presynaptic terminals was in at least three different pools: (1) as unbound, soluble protein; (2) bound to presynaptic vesicles; and (3) as microaggregates. Serial imaging of microaggregates over 1 week demonstrated a heterogeneous population with differing α-synuclein exchange rates. The microaggregate species were resistant to proteinase K, phosphorylated at serine-129, oxidized, and associated with a decrease in the presynaptic vesicle protein synapsin and glutamate immunogold labeling. Multiphoton FRAP provided the specific binding constants for α-synuclein's binding to synaptic vesicles and its effective diffusion coefficient in the soma and axon, setting the stage for future studies targeting synuclein modifications and their effects. Our in vivo results suggest that, under moderate overexpression conditions, α-synuclein aggregates are selectively found in presynaptic terminals.
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Vandenbunder B, Fourré N, Leray A, Mueller F, Völkel P, Angrand PO, Héliot L. PRC1 components exhibit different binding kinetics in Polycomb bodies. Biol Cell 2014; 106:111-25. [PMID: 24460908 DOI: 10.1111/boc.201300077] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 01/21/2014] [Indexed: 11/29/2022]
Abstract
BACKGROUND INFORMATION Polycomb group (PcG) proteins keep the memory of cell identity by maintaining the repression of numerous target genes. They accumulate into nuclear foci called Polycomb bodies, which function in Drosophila cells as silencing compartments where PcG target genes convene. PcG proteins also exert their activities elsewhere in the nucleoplasm. In mammalian cells, the dynamic organisation and function of Polycomb bodies remain to be determined. RESULTS Fluorescently tagged PcG proteins CBXs and their partners BMI1 and RING1 form foci of different sizes and intensities in human U2OS cells. Fluorescence recovery after photobleaching (FRAP) analysis reveals that PcG dynamics outside foci is governed by diffusion as complexes and transient binding. In sharp contrast, recovery curves inside foci are substantially slower and exhibit large variability. The slow binding component amplitudes correlate with the intensities and sizes of these foci, suggesting that foci contained varying numbers of binding sites. CBX4-green fluorescent protein (GFP) foci were more stable than CBX8-GFP foci; yet the presence of CBX4 or CBX8-GFP in the same focus had a minor impact on BMI1 and RING1 recovery kinetics. CONCLUSION We propose that FRAP recovery curves provide information about PcG binding to their target genes outside foci and about PcG spreading onto chromatin inside foci.
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Affiliation(s)
- Bernard Vandenbunder
- Biophotonique Cellulaire Fonctionnelle, Interdisciplinary Research Institute, Université Lille 1 - CNRS USR 3078, Parc de la Haute Borne, Villeneuve d'Ascq, 59658, France
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37
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Biomolecular dynamics and binding studies in the living cell. Phys Life Rev 2014; 11:1-30. [DOI: 10.1016/j.plrev.2013.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 11/20/2013] [Indexed: 11/22/2022]
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Rino J, Martin RM, Carvalho T, Carmo-Fonseca M. Imaging dynamic interactions between spliceosomal proteins and pre-mRNA in living cells. Methods 2014; 65:359-66. [PMID: 23969316 DOI: 10.1016/j.ymeth.2013.08.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 08/07/2013] [Accepted: 08/08/2013] [Indexed: 11/22/2022] Open
Abstract
The ability to observe protein dynamics in living cells is critical for the mechanistic understanding of highly flexible biological processes such as pre-mRNA splicing by the spliceosome. Splicing relies on intricate RNA and protein networks that are repeatedly rearranged during spliceosome assembly. Here we describe a method based on fluorescence microscopy that has been used by our and other laboratories to study interaction of spliceosomal proteins with nascent pre-mRNA in living cells. The method involves co-expressing in mammalian cells the target pre-mRNA labeled with one color, and the spliceosomal protein tagged with another color. The diffusion coefficient of the protein as well as its association and dissociation rates with the pre-mRNA are estimated by fluorescence recovery after photobleaching (FRAP) or photoactivation.
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Affiliation(s)
- José Rino
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Robert M Martin
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Teresa Carvalho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal.
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Van Royen ME, van Cappellen WA, Geverts B, Schmidt T, Houtsmuller AB, Schaaf MJM. Androgen receptor complexes probe DNA for recognition sequences by short random interactions. J Cell Sci 2014; 127:1406-16. [PMID: 24481814 DOI: 10.1242/jcs.135228] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Owing to the tremendous progress in microscopic imaging of fluorescently labeled proteins in living cells, the insight into the highly dynamic behavior of transcription factors has rapidly increased over the past decade. However, a consistent quantitative scheme of their action is still lacking. Using the androgen receptor (AR) as a model system, we combined three different fluorescence microscopy assays: single-molecule microscopy, photobleaching and correlation spectroscopy, to provide a quantitative model of the action of this transcription factor. This approach enabled us to distinguish two types of AR-DNA binding: very brief interactions, in the order of a few hundred milliseconds, and hormone-induced longer-lasting interactions, with a characteristic binding time of several seconds. In addition, freely mobile ARs were slowed down in the presence of hormone, suggesting the formation of large AR-co-regulator complexes in the nucleoplasm upon hormone activation. Our data suggest a model in which mobile hormone-induced complexes of transcription factors and co-regulators probe DNA by briefly binding at random sites, only forming relatively stable transcription initiation complexes when bound to specific recognition sequences.
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40
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Kaňa R. Mobility of photosynthetic proteins. PHOTOSYNTHESIS RESEARCH 2013; 116:465-79. [PMID: 23955784 DOI: 10.1007/s11120-013-9898-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 07/18/2013] [Indexed: 05/03/2023]
Abstract
The mobility of photosynthetic proteins represents an important factor that affects light-energy conversion in photosynthesis. The specific feature of photosynthetic proteins mobility can be currently measured in vivo using advanced microscopic methods, such as fluorescence recovery after photobleaching which allows the direct observation of photosynthetic proteins mobility on a single cell level. The heterogeneous organization of thylakoid membrane proteins results in heterogeneity in protein mobility. The thylakoid membrane contains both, protein-crowded compartments with immobile proteins and fluid areas (less crowded by proteins), allowing restricted diffusion of proteins. This heterogeneity represents an optimal balance as protein crowding is necessary for efficient light-energy conversion, and protein mobility plays an important role in the regulation of photosynthesis. The mobility is required for an optimal light-harvesting process (e.g., during state transitions), and also for transport of proteins during their synthesis or repair. Protein crowding is then a key limiting factor of thylakoid membrane protein mobility; the less thylakoid membranes are crowded by proteins, the higher protein mobility is observed. Mobility of photosynthetic proteins outside the thylakoid membrane (lumen and stroma/cytosol) is less understood. Cyanobacterial phycobilisomes attached to the stromal side of the thylakoid can move relatively fast. Therefore, it seems that stroma with their active enzymes of the Calvin-Benson cycle, are a more fluid compartment in comparison to the rather rigid thylakoid lumen. In conclusion, photosynthetic protein diffusion is generally slower in comparison to similarly sized proteins from other eukaryotic membranes or organelles. Mobility of photosynthetic proteins resembles restricted protein diffusion in bacteria, and has been rationalized by high protein crowding similar to that of thylakoids.
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Affiliation(s)
- Radek Kaňa
- Department of photothrophic microorganisms - Algatech, Institute of Microbiology, Academy of Sciences of the Czech Republic, Opatovický mlýn, 379 81, Třeboň, Czech Republic,
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Mueller F, Stasevich TJ, Mazza D, McNally JG. Quantifying transcription factor kinetics: at work or at play? Crit Rev Biochem Mol Biol 2013; 48:492-514. [PMID: 24025032 DOI: 10.3109/10409238.2013.833891] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Transcription factors (TFs) interact dynamically in vivo with chromatin binding sites. Here we summarize and compare the four different techniques that are currently used to measure these kinetics in live cells, namely fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), single molecule tracking (SMT) and competition ChIP (CC). We highlight the principles underlying each of these approaches as well as their advantages and disadvantages. A comparison of data from each of these techniques raises an important question: do measured transcription kinetics reflect biologically functional interactions at specific sites (i.e. working TFs) or do they reflect non-specific interactions (i.e. playing TFs)? To help resolve this dilemma we discuss five key unresolved biological questions related to the functionality of transient and prolonged binding events at both specific promoter response elements as well as non-specific sites. In support of functionality, we review data suggesting that TF residence times are tightly regulated, and that this regulation modulates transcriptional output at single genes. We argue that in addition to this site-specific regulatory role, TF residence times also determine the fraction of promoter targets occupied within a cell thereby impacting the functional status of cellular gene networks. Thus, TF residence times are key parameters that could influence transcription in multiple ways.
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Affiliation(s)
- Florian Mueller
- Institut Pasteur, Computational Imaging and Modeling Unit, CNRS , Paris , France
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Single-molecule imaging of transcription factor binding to DNA in live mammalian cells. Nat Methods 2013; 10:421-6. [PMID: 23524394 PMCID: PMC3664538 DOI: 10.1038/nmeth.2411] [Citation(s) in RCA: 344] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 02/26/2013] [Indexed: 02/07/2023]
Abstract
Imaging single fluorescent proteins in living mammalian cells is challenged by out-of-focus fluorescence excitation. To reduce out-of-focus fluorescence we developed reflected light-sheet microscopy (RLSM), a fluorescence microscopy method allowing selective plane illumination throughout the nuclei of living mammalian cells. A thin light sheet parallel to the imaging plane and close to the sample surface is generated by reflecting an elliptical laser beam incident from the top by 90° with a small mirror. The thin light sheet allows for an increased signal-to-background ratio superior to that in previous illumination schemes and enables imaging of single fluorescent proteins with up to 100-Hz time resolution. We demonstrated the single-molecule sensitivity of RLSM by measuring the DNA-bound fraction of glucocorticoid receptor (GR) and determining the residence times on DNA of various oligomerization states and mutants of GR and estrogen receptor-α (ER), which permitted us to resolve different modes of DNA binding of GR. We demonstrated two-color single-molecule imaging by observing the spatiotemporal colocalization of two different protein pairs. Our single-molecule measurements and statistical analysis revealed dynamic properties of transcription factors.
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Day CA, Kraft LJ, Kang M, Kenworthy AK. Analysis of protein and lipid dynamics using confocal fluorescence recovery after photobleaching (FRAP). ACTA ACUST UNITED AC 2013; Chapter 2:Unit2.19. [PMID: 23042527 DOI: 10.1002/0471142956.cy0219s62] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) is a powerful, versatile, and widely accessible tool to monitor molecular dynamics in living cells that can be performed using modern confocal microscopes. Although the basic principles of FRAP are simple, quantitative FRAP analysis requires careful experimental design, data collection, and analysis. In this unit, we discuss the theoretical basis for confocal FRAP, followed by step-by-step protocols for FRAP data acquisition using a laser-scanning confocal microscope for (1) measuring the diffusion of a membrane protein, (2) measuring the diffusion of a soluble protein, and (3) analysis of intracellular trafficking. Finally, data analysis procedures are discussed, and an equation for determining the diffusion coefficient of a molecular species undergoing pure diffusion is presented.
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Affiliation(s)
- Charles A Day
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
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44
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Daddysman MK, Fecko CJ. Revisiting point FRAP to quantitatively characterize anomalous diffusion in live cells. J Phys Chem B 2013; 117:1241-51. [PMID: 23311513 DOI: 10.1021/jp310348s] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) is widely used to interrogate diffusion and binding of proteins in live cells. Herein, we apply two-photon excited FRAP with a diffraction limited bleaching and observation volume to study anomalous diffusion of unconjugated green fluorescence protein (GFP) in vitro and in cells. Experiments performed on dilute solutions of GFP reveal that reversible fluorophore bleaching can be mistakenly interpreted as anomalous diffusion. We derive a reaction-diffusion FRAP model that includes reversible photobleaching, and demonstrate that it properly accounts for these photophysics. We then apply this model to investigate the diffusion of GFP in HeLa cells and polytene cells of Drosophila larval salivary glands. GFP exhibits anomalous diffusion in the cytoplasm of both cell types and in HeLa nuclei. Polytene nuclei contain optically resolvable chromosomes, permitting FRAP experiments that focus separately on chromosomal or interchrosomal regions. We find that GFP exhibits anomalous diffusion in chromosomal regions but diffuses normally in regions devoid of chromatin. This observation indicates that obstructed transport through chromatin and not crowding by macromolecules is a source of anomalous diffusion in polytene nuclei. This behavior is likely true in other cells, so it will be important to account for this type of transport physics and for reversible photobleaching to properly interpret future FRAP experiments on DNA-binding proteins.
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Affiliation(s)
- Matthew K Daddysman
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA
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Erdel F, Rippe K. Quantifying transient binding of ISWI chromatin remodelers in living cells by pixel-wise photobleaching profile evolution analysis. Proc Natl Acad Sci U S A 2012; 109:E3221-30. [PMID: 23129662 PMCID: PMC3511136 DOI: 10.1073/pnas.1209579109] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Interactions between nuclear proteins and chromatin frequently occur on the time scale of seconds and below. These transient binding events are important for the fast identification of target sites as concluded from our previous analysis of the human chromatin remodelers Snf2H and Snf2L from the imitation switch (ISWI) family. Both ATP-driven molecular motor proteins are able to translocate nucleosomes along the DNA and appear to exert this activity only on a small number of nucleosomes to which they bind more tightly. For mechanistic studies, one needs to distinguish such translocation reactions or other long-lived interactions associated with conformational changes and/or ATP hydrolysis from nonproductive chromatin sampling during target search. These processes can be separated by measuring the duration of nucleosome binding with subsecond time resolution. To reach this goal, we have developed a fluorescence bleaching technique termed pixel-wise photobleaching profile evolution analysis (3PEA). It exploits the inherent time structure of confocal microscopy images and yields millisecond resolution. 3PEA represents a generally applicable approach to quantitate transient chromatin interactions in the 2- to 500-ms time regime within only ∼1 s needed for a measurement. The green autofluorescent protein (GFP)-tagged Snf2H and Snf2L and the inactive Snf2L+13 splice variant were studied by 3PEA in comparison to the isolated GFP or red autofluorescent protein and a GFP pentamer. Our results reveal that the residence time for transient chromatin binding of Snf2H and Snf2L is <2 ms, and strongly support the view that ISWI-type remodelers are only rarely active in unperturbed cells during G1 phase.
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Affiliation(s)
- Fabian Erdel
- Research Group Genome Organization and Function, Deutsches Krebsforschungszentrum (DKFZ) and BioQuant, 69120 Heidelberg, Germany
| | - Karsten Rippe
- Research Group Genome Organization and Function, Deutsches Krebsforschungszentrum (DKFZ) and BioQuant, 69120 Heidelberg, Germany
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