1
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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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2
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Sternberg H, Buriakovsky E, Bloch D, Gutman O, Henis YI, Yalovsky S. Formation of self-organizing functionally distinct Rho of plants domains involves a reduced mobile population. PLANT PHYSIOLOGY 2021; 187:2485-2508. [PMID: 34618086 PMCID: PMC8644358 DOI: 10.1093/plphys/kiab385] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
Rho family proteins are central to the regulation of cell polarity in eukaryotes. Rho of Plants-Guanyl nucleotide Exchange Factor (ROPGEF) can form self-organizing polar domains following co-expression with an Rho of Plants (ROP) and an ROP GTPase-Activating Protein (ROPGAP). Localization of ROPs in these domains has not been demonstrated, and the mechanisms underlying domain formation and function are not well understood. Here we show that six different ROPs form self-organizing domains when co-expressed with ROPGEF3 and GAP1 in Nicotiana benthamiana or Arabidopsis (Arabidopsis thaliana). Domain formation was associated with ROP-ROPGEF3 association, reduced ROP mobility, as revealed by time-lapse imaging and Fluorescence Recovery After Photobleaching beam size analysis, and was independent of Rho GTP Dissociation Inhibitor mediated recycling. The domain formation depended on the ROPs' activation/inactivation cycles and interaction with anionic lipids via a C-terminal polybasic domain. Coexpression with the microtubule-associated protein ROP effector INTERACTOR OF CONSTITUTIVELY ACTIVE ROP 1 (ICR1) revealed differential function of the ROP domains in the ability to recruit ICR1. Taken together, the results reveal mechanisms underlying self-organizing ROP domain formation and function.
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Affiliation(s)
- Hasana Sternberg
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Ella Buriakovsky
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Daria Bloch
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Orit Gutman
- School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Yoav I Henis
- School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Shaul Yalovsky
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
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3
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Eroumé KS, Cavill R, Staňková K, de Boer J, Carlier A. Exploring the influence of cytosolic and membrane FAK activation on YAP/TAZ nuclear translocation. Biophys J 2021; 120:4360-4377. [PMID: 34509508 PMCID: PMC8553670 DOI: 10.1016/j.bpj.2021.09.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/16/2021] [Accepted: 09/07/2021] [Indexed: 11/12/2022] Open
Abstract
Membrane binding and unbinding dynamics play a crucial role in the biological activity of several nonintegral membrane proteins, which have to be recruited to the membrane to perform their functions. By localizing to the membrane, these proteins are able to induce downstream signal amplification in their respective signaling pathways. Here, we present a 3D computational approach using reaction-diffusion equations to investigate the relation between membrane localization of focal adhesion kinase (FAK), Ras homolog family member A (RhoA), and signal amplification of the YAP/TAZ signaling pathway. Our results show that the theoretical scenarios in which FAK is membrane bound yield robust and amplified YAP/TAZ nuclear translocation signals. Moreover, we predict that the amount of YAP/TAZ nuclear translocation increases with cell spreading, confirming the experimental findings in the literature. In summary, our in silico predictions show that when the cell membrane interaction area with the underlying substrate increases, for example, through cell spreading, this leads to more encounters between membrane-bound signaling partners and downstream signal amplification. Because membrane activation is a motif common to many signaling pathways, this study has important implications for understanding the design principles of signaling networks.
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Affiliation(s)
- Kerbaï Saïd Eroumé
- MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, the Netherlands
| | - Rachel Cavill
- Department of Data Science and Knowledge Engineering, Faculty of Science and Engineering, Maastricht University, Maastricht, the Netherlands
| | - Katerina Staňková
- Department of Data Science and Knowledge Engineering, Faculty of Science and Engineering, Maastricht University, Maastricht, the Netherlands
| | - Jan de Boer
- Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Aurélie Carlier
- MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, the Netherlands.
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4
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Parameter estimation in fluorescence recovery after photobleaching: quantitative analysis of protein binding reactions and diffusion. J Math Biol 2021; 83:1. [PMID: 34129100 PMCID: PMC8205911 DOI: 10.1007/s00285-021-01616-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 09/15/2020] [Accepted: 10/27/2020] [Indexed: 02/07/2023]
Abstract
Fluorescence recovery after photobleaching (FRAP) is a common experimental method for investigating rates of molecular redistribution in biological systems. Many mathematical models of FRAP have been developed, the purpose of which is usually the estimation of certain biological parameters such as the diffusivity and chemical reaction rates of a protein, this being accomplished by fitting the model to experimental data. In this article, we consider a two species reaction–diffusion FRAP model. Using asymptotic analysis, we derive new FRAP recovery curve approximation formulae, and formally re-derive existing ones. On the basis of these formulae, invoking the concept of Fisher information, we predict, in terms of biological and experimental parameters, sufficient conditions to ensure that the values all model parameters can be estimated from data. We verify our predictions with extensive computational simulations. We also use computational methods to investigate cases in which some or all biological parameters are theoretically inestimable. In these cases, we propose methods which can be used to extract the maximum possible amount of information from the FRAP data.
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5
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Karagöz Z, Rijns L, Dankers PY, van Griensven M, Carlier A. Towards understanding the messengers of extracellular space: Computational models of outside-in integrin reaction networks. Comput Struct Biotechnol J 2020; 19:303-314. [PMID: 33425258 PMCID: PMC7779863 DOI: 10.1016/j.csbj.2020.12.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 02/06/2023] Open
Abstract
The interactions between cells and their extracellular matrix (ECM) are critically important for homeostatic control of cell growth, proliferation, differentiation and apoptosis. Transmembrane integrin molecules facilitate the communication between ECM and the cell. Since the characterization of integrins in the late 1980s, there has been great advancement in understanding the function of integrins at different subcellular levels. However, the versatility in molecular pathways integrins are involved in, the high diversity in their interaction partners both outside and inside the cell as well as on the cell membrane and the short lifetime of events happening at the cell-ECM interface make it difficult to elucidate all the details regarding integrin function experimentally. To overcome the experimental challenges and advance the understanding of integrin biology, computational modeling tools have been used extensively. In this review, we summarize the computational models of integrin signaling while we explain the function of integrins at three main subcellular levels (outside the cell, cell membrane, cytosol). We also discuss how these computational modeling efforts can be helpful in other disciplines such as biomaterial design. As such, this review is a didactic modeling summary for biomaterial researchers interested in complementing their experimental work with computational tools or for seasoned computational scientists that would like to advance current in silico integrin models.
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Affiliation(s)
- Zeynep Karagöz
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Universiteitssingel 40, 6229 ER Maastricht, the Netherlands
| | - Laura Rijns
- Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, the Netherlands
| | - Patricia Y.W. Dankers
- Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, the Netherlands
| | - Martijn van Griensven
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Universiteitssingel 40, 6229 ER Maastricht, the Netherlands
| | - Aurélie Carlier
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Universiteitssingel 40, 6229 ER Maastricht, the Netherlands
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6
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Wist M, Meier L, Gutman O, Haas J, Endres S, Zhou Y, Rösler R, Wiese S, Stilgenbauer S, Hobeika E, Henis YI, Gierschik P, Walliser C. Noncatalytic Bruton's tyrosine kinase activates PLCγ 2 variants mediating ibrutinib resistance in human chronic lymphocytic leukemia cells. J Biol Chem 2020; 295:5717-5736. [PMID: 32184360 DOI: 10.1074/jbc.ra119.011946] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/26/2020] [Indexed: 12/25/2022] Open
Abstract
Treatment of patients with chronic lymphocytic leukemia (CLL) with inhibitors of Bruton's tyrosine kinase (BTK), such as ibrutinib, is limited by primary or secondary resistance to this drug. Examinations of CLL patients with late relapses while on ibrutinib, which inhibits BTK's catalytic activity, revealed several mutations in BTK, most frequently resulting in the C481S substitution, and disclosed many mutations in PLCG2, encoding phospholipase C-γ2 (PLCγ2). The PLCγ2 variants typically do not exhibit constitutive activity in cell-free systems, leading to the suggestion that in intact cells they are hypersensitive to Rac family small GTPases or to the upstream kinases spleen-associated tyrosine kinase (SYK) and Lck/Yes-related novel tyrosine kinase (LYN). The sensitivity of the PLCγ2 variants to BTK itself has remained unknown. Here, using genetically-modified DT40 B lymphocytes, along with various biochemical assays, including analysis of PLCγ2-mediated inositol phosphate formation, inositol phospholipid assessments, fluorescence recovery after photobleaching (FRAP) static laser microscopy, and determination of intracellular calcium ([Ca2+] i ), we show that various CLL-specific PLCγ2 variants such as PLCγ2S707Y are hyper-responsive to activated BTK, even in the absence of BTK's catalytic activity and independently of enhanced PLCγ2 phospholipid substrate supply. At high levels of B-cell receptor (BCR) activation, which may occur in individual CLL patients, catalytically-inactive BTK restored the ability of the BCR to mediate increases in [Ca2+] i Because catalytically-inactive BTK is insensitive to active-site BTK inhibitors, the mechanism involving the noncatalytic BTK uncovered here may contribute to preexisting reduced sensitivity or even primary resistance of CLL to these drugs.
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Affiliation(s)
- Martin Wist
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Laura Meier
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jennifer Haas
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sascha Endres
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yuan Zhou
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Reinhild Rösler
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sebastian Wiese
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, 89081 Ulm, Germany
| | - Elias Hobeika
- Institute of Immunology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Peter Gierschik
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
| | - Claudia Walliser
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
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7
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Röding M, Lacroix L, Krona A, Gebäck T, Lorén N. A Highly Accurate Pixel-Based FRAP Model Based on Spectral-Domain Numerical Methods. Biophys J 2019; 116:1348-1361. [PMID: 30878198 PMCID: PMC6451077 DOI: 10.1016/j.bpj.2019.02.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 02/05/2019] [Accepted: 02/25/2019] [Indexed: 01/09/2023] Open
Abstract
We introduce a new, to our knowledge, numerical model based on spectral methods for analysis of fluorescence recovery after photobleaching data. The model covers pure diffusion and diffusion and binding (reaction-diffusion) with immobile binding sites, as well as arbitrary bleach region shapes. Fitting of the model is supported using both conventional recovery-curve-based estimation and pixel-based estimation, in which all individual pixels in the data are utilized. The model explicitly accounts for multiple bleach frames, diffusion (and binding) during bleaching, and bleaching during imaging. To our knowledge, no other fluorescence recovery after photobleaching framework incorporates all these model features and estimation methods. We thoroughly validate the model by comparison to stochastic simulations of particle dynamics and find it to be highly accurate. We perform simulation studies to compare recovery-curve-based estimation and pixel-based estimation in realistic settings and show that pixel-based estimation is the better method for parameter estimation as well as for distinguishing pure diffusion from diffusion and binding. We show that accounting for multiple bleach frames is important and that the effect of neglecting this is qualitatively different for the two estimation methods. We perform a simple experimental validation showing that pixel-based estimation provides better agreement with literature values than recovery-curve-based estimation and that accounting for multiple bleach frames improves the result. Further, the software developed in this work is freely available online.
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Affiliation(s)
- Magnus Röding
- RISE Research Institutes of Sweden, Bioscience and Materials, Göteborg, Sweden.
| | - Leander Lacroix
- RISE Research Institutes of Sweden, Bioscience and Materials, Göteborg, Sweden
| | - Annika Krona
- RISE Research Institutes of Sweden, Bioscience and Materials, Göteborg, Sweden
| | - Tobias Gebäck
- Mathematical Sciences, Chalmers University of Technology, Göteborg, Sweden
| | - Niklas Lorén
- RISE Research Institutes of Sweden, Bioscience and Materials, Göteborg, Sweden; Department of Physics, Chalmers University of Technology, Göteborg, Sweden
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8
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Malacrida L, Hedde PN, Ranjit S, Cardarelli F, Gratton E. Visualization of barriers and obstacles to molecular diffusion in live cells by spatial pair-cross-correlation in two dimensions. BIOMEDICAL OPTICS EXPRESS 2018; 9:303-321. [PMID: 29359105 PMCID: PMC5772584 DOI: 10.1364/boe.9.000303] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 12/09/2017] [Accepted: 12/11/2017] [Indexed: 05/09/2023]
Abstract
Despite recent advances in optical super-resolution, we lack a method that can visualize the path followed by diffusing molecules in the cytoplasm or in the nucleus of cells. Fluorescence correlation spectroscopy (FCS) provides molecular dynamics at the single molecule level by averaging the behavior of many molecules over time at a single spot, thus achieving very good statistics but at only one point in the cell. Earlier image-based methods including raster-scan and spatiotemporal image correlation need spatial averaging over relatively large areas, thus compromising spatial resolution. Here, we use spatial pair-cross-correlation in two dimensions (2D-pCF) to obtain relatively high resolution images of molecular diffusion dynamics and transport in live cells. The 2D-pCF method measures the time for a particle to go from one location to another by cross-correlating the intensity fluctuations at specific points in an image. Hence, a visual map of the average path followed by molecules is created.
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Affiliation(s)
- Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
- Área de Investigación Respiratoria, Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay
- LM and PNH contributed equally to this work
| | - Per Niklas Hedde
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
- LM and PNH contributed equally to this work
| | - Suman Ranjit
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
| | - Francesco Cardarelli
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA
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9
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Imaging approaches for analysis of cholesterol distribution and dynamics in the plasma membrane. Chem Phys Lipids 2016; 199:106-135. [PMID: 27016337 DOI: 10.1016/j.chemphyslip.2016.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 03/04/2016] [Indexed: 11/21/2022]
Abstract
Cholesterol is an important lipid component of the plasma membrane (PM) of mammalian cells, where it is involved in control of many physiological processes, such as endocytosis, cell migration, cell signalling and surface ruffling. In an attempt to explain these functions of cholesterol, several models have been put forward about cholesterol's lateral and transbilayer organization in the PM. In this article, we review imaging techniques developed over the last two decades for assessing the distribution and dynamics of cholesterol in the PM of mammalian cells. Particular focus is on fluorescence techniques to study the lateral and inter-leaflet distribution of suitable cholesterol analogues in the PM of living cells. We describe also several methods for determining lateral cholesterol dynamics in the PM including fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), single particle tracking (SPT) and spot variation FCS coupled to stimulated emission depletion (STED) microscopy. For proper interpretation of such measurements, we provide some background in probe photophysics and diffusion phenomena occurring in cell membranes. In particular, we show the equivalence of the reaction-diffusion approach, as used in FRAP and FCS, and continuous time random walk (CTRW) models, as often invoked in SPT studies. We also discuss mass spectrometry (MS) based imaging of cholesterol in the PM of fixed cells and compare this method with fluorescence imaging of sterols. We conclude that evidence from many experimental techniques converges towards a model of a homogeneous distribution of cholesterol with largely free and unhindered diffusion in both leaflets of the PM.
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10
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Using FRAP or FRAPA to Visualize the Movement of Fluorescently Labeled Proteins or Cellular Organelles in Live Cultured Neurons Transformed with Adeno-Associated Viruses. Methods Mol Biol 2016; 1474:125-51. [PMID: 27515078 DOI: 10.1007/978-1-4939-6352-2_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fluorescence recovery after photobleaching (FRAP) and fluorescence redistribution after photoactivation (FRAPA) are complementary methods used to gauge the movement of proteins or sub-resolution organelles within cells. Using these methods we can determine the nature of the movement of labeled particles, whether it is random, constrained, or active, the coefficient of diffusion if applicable, binding and unbinding constants, and the direction of active transport. These two techniques have been extensively utilized to probe the cell biology of neurons. A practical outline of FRAP and FRAPA in cultured neurons is presented, including the preparation of the neurons and their infection with adeno-associated viral vectors. Considerations in planning such experiments are provided.
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11
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Abstract
Mechanical stimuli are known to be potent regulators of the form and function of cells and organisms. Although biological regulation has classically been understood in terms of principles from solution biochemistry, advancements in many fields have led to the development of a suite of techniques that are able to reveal the interplay between mechanical loading and changes in the biochemical properties of proteins in systems ranging from single molecules to living organisms. Here, we review these techniques and highlight the emergence of a new molecular-scale understanding of the mechanisms mediating the detection and response of cells to mechanical stimuli, a process termed mechanotransduction. Specifically, we focus on the role of subcellular adhesion structures in sensing the stiffness of the surrounding environment because this process is pertinent to applications in tissue engineering as well the onset of several mechanosensitive disease states, including cancer.
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Affiliation(s)
- Andrew S LaCroix
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708;
| | - Katheryn E Rothenberg
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708;
| | - Brenton D Hoffman
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708;
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12
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Filić V, Marinović M, Faix J, Weber I. The IQGAP-related protein DGAP1 mediates signaling to the actin cytoskeleton as an effector and a sequestrator of Rac1 GTPases. Cell Mol Life Sci 2014; 71:2775-85. [PMID: 24664433 PMCID: PMC11113302 DOI: 10.1007/s00018-014-1606-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/26/2014] [Accepted: 03/10/2014] [Indexed: 11/24/2022]
Abstract
Proteins are typically categorized into protein families based on their domain organization. Yet, evolutionarily unrelated proteins can also be grouped together according to their common functional roles. Sequestering proteins constitute one such functional class, acting as macromolecular buffers and serving as an intracellular reservoir ready to release large quantities of bound proteins or other molecules upon appropriate stimulation. Another functional protein class comprises effector proteins, which constitute essential components of many intracellular signal transduction pathways. For instance, effectors of small GTP-hydrolases are activated upon binding a GTP-bound GTPase and thereupon participate in downstream interactions. Here we describe a member of the IQGAP family of scaffolding proteins, DGAP1 from Dictyostelium, which unifies the roles of an effector and a sequestrator in regard to the small GTPase Rac1. Unlike classical effectors, which bind their activators transiently leading to short-lived signaling complexes, interaction between DGAP1 and Rac1-GTP is stable and induces formation of a complex with actin-bundling proteins cortexillins at the back end of the cell. An oppositely localized Rac1 effector, the Scar/WAVE complex, promotes actin polymerization at the cell front. Competition between DGAP1 and Scar/WAVE for the common activator Rac1-GTP might provide the basis for the oscillatory re-polarization typically seen in randomly migrating Dictyostelium cells. We discuss the consequences of the dual roles exerted by DGAP1 and Rac1 in the regulation of cell motility and polarity, and propose that similar signaling mechanisms may be of general importance in regulating spatiotemporal dynamics of the actin cytoskeleton by small GTPases.
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Affiliation(s)
- Vedrana Filić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | - Maja Marinović
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | - Jan Faix
- Hannover Medical School, Institute for Biophysical Chemistry, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Igor Weber
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
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13
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Solanko LM, Honigmann A, Midtiby HS, Lund FW, Brewer JR, Dekaris V, Bittman R, Eggeling C, Wüstner D. Membrane orientation and lateral diffusion of BODIPY-cholesterol as a function of probe structure. Biophys J 2014; 105:2082-92. [PMID: 24209853 DOI: 10.1016/j.bpj.2013.09.031] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/26/2013] [Accepted: 09/16/2013] [Indexed: 11/29/2022] Open
Abstract
Cholesterol tagged with the BODIPY fluorophore via the central difluoroboron moiety of the dye (B-Chol) is a promising probe for studying intracellular cholesterol dynamics. We synthesized a new BODIPY-cholesterol probe (B-P-Chol) with the fluorophore attached via one of its pyrrole rings to carbon-24 of cholesterol (B-P-Chol). Using two-photon fluorescence polarimetry in giant unilamellar vesicles and in the plasma membrane (PM) of living intact and actin-disrupted cells, we show that the BODIPY-groups in B-Chol and B-P-Chol are oriented perpendicular and almost parallel to the bilayer normal, respectively. B-Chol is in all three membrane systems much stronger oriented than B-P-Chol. Interestingly, we found that the lateral diffusion in the PM was two times slower for B-Chol than for B-P-Chol, although we found no difference in lateral diffusion in model membranes. Stimulated emission depletion microscopy, performed for the first time, to our knowledge, with fluorescent sterols, revealed that the difference in lateral diffusion of the BODIPY-cholesterol probes was not caused by anomalous subdiffusion, because diffusion of both analogs in the PM was free but not hindered. Our combined measurements show that the position and orientation of the BODIPY moiety in cholesterol analogs have a severe influence on lateral diffusion specifically in the PM of living cells.
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Affiliation(s)
- Lukasz M Solanko
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
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14
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Bielopolski N, Lam AD, Bar-On D, Sauer M, Stuenkel EL, Ashery U. Differential interaction of tomosyn with syntaxin and SNAP25 depends on domains in the WD40 β-propeller core and determines its inhibitory activity. J Biol Chem 2014; 289:17087-99. [PMID: 24782308 DOI: 10.1074/jbc.m113.515296] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal exocytosis depends on efficient formation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes and is regulated by tomosyn, a SNARE-binding protein. To gain new information about tomosyn's activity, we characterized its mobility and organization on the plasma membrane (PM) in relation to other SNARE proteins and inhibition of exocytosis. By using direct stochastic optical reconstruction microscopy (dSTORM), we found tomosyn to be organized in small clusters adjacent to syntaxin clusters. In addition, we show that tomosyn is present in both syntaxin-tomosyn complexes and syntaxin-SNAP25-tomosyn complexes. Tomosyn mutants that lack residues 537-578 or 897-917 from its β-propeller core diffused faster on the PM and exhibited reduced binding to SNAP25, suggesting that these mutants shift the equilibrium between tomosyn-syntaxin-SNAP25 complexes on the PM to tomosyn-syntaxin complexes. As these deletion mutants impose less inhibition on exocytosis, we suggest that tomosyn inhibition is mediated via tomosyn-syntaxin-SNAP25 complexes and not tomosyn-syntaxin complexes. These findings characterize, for the first time, tomosyn's dynamics at the PM and its relation to its inhibition of exocytosis.
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Affiliation(s)
- Noa Bielopolski
- From the Department of Neurobiology, Life Sciences Faculty, and
| | - Alice D Lam
- the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Dana Bar-On
- From the Department of Neurobiology, Life Sciences Faculty, and Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Markus Sauer
- the Department of Biotechnology and Biophysics, Julius Maximilians University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Edward L Stuenkel
- the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Uri Ashery
- From the Department of Neurobiology, Life Sciences Faculty, and Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel,
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15
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Weiss M. Crowding, Diffusion, and Biochemical Reactions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 307:383-417. [DOI: 10.1016/b978-0-12-800046-5.00011-4] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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16
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Weigert R, Porat-Shliom N, Amornphimoltham P. Imaging cell biology in live animals: ready for prime time. ACTA ACUST UNITED AC 2013; 201:969-79. [PMID: 23798727 PMCID: PMC3691462 DOI: 10.1083/jcb.201212130] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Time-lapse fluorescence microscopy is one of the main tools used to image subcellular structures in living cells. Yet for decades it has been applied primarily to in vitro model systems. Thanks to the most recent advancements in intravital microscopy, this approach has finally been extended to live rodents. This represents a major breakthrough that will provide unprecedented new opportunities to study mammalian cell biology in vivo and has already provided new insight in the fields of neurobiology, immunology, and cancer biology.
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Affiliation(s)
- Roberto Weigert
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
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17
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Lavelin I, Wolfenson H, Patla I, Henis YI, Medalia O, Volberg T, Livne A, Kam Z, Geiger B. Differential effect of actomyosin relaxation on the dynamic properties of focal adhesion proteins. PLoS One 2013; 8:e73549. [PMID: 24039980 PMCID: PMC3767655 DOI: 10.1371/journal.pone.0073549] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/22/2013] [Indexed: 12/21/2022] Open
Abstract
Treatment of cultured cells with inhibitors of actomyosin contractility induces rapid deterioration of stress fibers, and disassembly of the associated focal adhesions (FAs). In this study, we show that treatment with the Rho kinase inhibitor Y-27632, which blocks actomyosin contractility, induces disarray in the FA-associated actin bundles, followed by the differential dissociation of eight FA components from the adhesion sites. Live-cell microscopy indicated that the drug triggers rapid dissociation of VASP and zyxin from FAs (τ values of 7-8 min), followed by talin, paxillin and ILK (τ ~16 min), and then by FAK, vinculin and kindlin-2 (τ = 25-28 min). Examination of the molecular kinetics of the various FA constituents, using Fluorescence Recovery After Photobleaching (FRAP), in the absence of or following short-term treatment with the drug, revealed major changes in the kon and koff values of the different proteins tested, which are in close agreement with their differential dissociation rates from the adhesion sites. These findings indicate that mechanical, actomyosin-generated forces differentially regulate the molecular kinetics of individual FA-associated molecules, and thereby modulate FA composition and stability.
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Affiliation(s)
- Irena Lavelin
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Haguy Wolfenson
- Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel
| | - Israel Patla
- Department of Life Sciences and the National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be’er-Sheva, Israel
| | - Yoav I. Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel
| | - Ohad Medalia
- Department of Life Sciences and the National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be’er-Sheva, Israel
- Department of Biochemistry, University of Zurich, Zürich, Switzerland
| | - Tova Volberg
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Ariel Livne
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Zvi Kam
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Benjamin Geiger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
- * E-mail:
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18
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Abstract
Ras GTPases are important regulators of pathways controlling proliferation, differentiation and transformation. Three ubiquitously expressed almost identical Ras genes are not functionally redundant; this has been attributed to their distinctive trafficking and localization profiles. A palmitoylation cycle controls the correct compartmentalization of H-Ras and N-Ras. We review recent data that reveal how this cycle can be regulated by membrane organization to influence the spatiotemporal signalling of Ras.
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19
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Staras K, Mikulincer D, Gitler D. Monitoring and quantifying dynamic physiological processes in live neurons using fluorescence recovery after photobleaching. J Neurochem 2013; 126:213-22. [PMID: 23496032 DOI: 10.1111/jnc.12240] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 12/27/2022]
Abstract
The direct visualization of subcellular dynamic processes is often hampered by limitations in the resolving power achievable with conventional microscopy techniques. Fluorescence recovery after photobleaching has emerged as a highly informative approach to address this challenge, permitting the quantitative measurement of the movement of small organelles and proteins in living functioning cells, and offering detailed insights into fundamental cellular phenomena of physiological importance. In recent years, its implementation has benefited from the increasing availability of confocal microscopy systems and of powerful labeling techniques based on genetically encoded fluorescent proteins or other chemical markers. In this review, we present fluorescence recovery after photobleaching and related techniques in the context of contemporary neurobiological research and discuss quantitative and semi-quantitative approaches to their interpretation.
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Affiliation(s)
- Kevin Staras
- School of Life Sciences, University of Sussex, Brighton, UK
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20
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Mazza D, Abernathy A, Golob N, Morisaki T, McNally JG. A benchmark for chromatin binding measurements in live cells. Nucleic Acids Res 2012; 40:e119. [PMID: 22844090 PMCID: PMC3424588 DOI: 10.1093/nar/gks701] [Citation(s) in RCA: 214] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Live-cell measurement of protein binding to chromatin allows probing cellular biochemistry in physiological conditions, which are difficult to mimic in vitro. However, different studies have yielded widely discrepant predictions, and so it remains uncertain how to make the measurements accurately. To establish a benchmark we measured binding of the transcription factor p53 to chromatin by three approaches: fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS) and single-molecule tracking (SMT). Using new procedures to analyze the SMT data and to guide the FRAP and FCS analysis, we show how all three approaches yield similar estimates for both the fraction of p53 molecules bound to chromatin (only about 20%) and the residence time of these bound molecules (∼1.8 s). We also apply these procedures to mutants in p53 chromatin binding. Our results support the model that p53 locates specific sites by first binding at sequence-independent sites.
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Affiliation(s)
- Davide Mazza
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, 20892, Bethesda, MD, USA
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21
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Sanderson JM. Resolving the kinetics of lipid, protein and peptide diffusion in membranes. Mol Membr Biol 2012; 29:118-43. [DOI: 10.3109/09687688.2012.678018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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