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Fenz SF, Smith AS, Monzel C. Measuring the Invisible: Determining the Size of Growing Nanodomains Using the "Inverse FCS". Biophys J 2017; 112:2245-2246. [PMID: 28591596 DOI: 10.1016/j.bpj.2017.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 04/03/2017] [Accepted: 04/05/2017] [Indexed: 11/25/2022] Open
Affiliation(s)
- Susanne F Fenz
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany.
| | - Ana-Sunčana Smith
- PULS Group, Institut für Theoretische Physik and the Excellence Cluster: Engineering of Advanced Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; Institute Ruđer Bošković, Division of Physical Chemistry, Zagreb, Croatia
| | - Cornelia Monzel
- Laboratoire Physico-Chimie, Institut Curie, CNRS UMR168, Paris-Science Lettres, Université Pierre et Marie Curie-Paris 6, Paris, France
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Glogger M, Subota I, Pezzarossa A, Denecke AL, Carrington M, Fenz SF, Engstler M. Facilitating trypanosome imaging. Exp Parasitol 2017; 180:13-18. [PMID: 28363776 PMCID: PMC5540225 DOI: 10.1016/j.exppara.2017.03.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/08/2017] [Accepted: 03/25/2017] [Indexed: 11/30/2022]
Abstract
Research on trypanosomes as a model organism has provided a substantial contribution to a detailed understanding of basic cellular processes within the last few years. At the same time, major advances in super-resolution microscopy have been achieved, facilitating the resolution of biological structures in living cells at a scale of a few nm. However, the motility of trypanosomes has prevented access to high resolution microscopy of live cells. Here, we present a hydrogel based on poly(ethylene glycol) functionalized with either norbornene or thiol moieties for UV induced thiol-ene crosslinking for the embedding and imaging of live trypanosomes. The resulting gel exhibits low autofluorescence properties, immobilizes the cells efficiently on the nanometer scale and is compatible with cell viability for up to one hour at 24 °C. We applied super-resolution imaging to the inner plasma membrane leaflet using lipid-anchored eYFP as a probe. We find specific domains within the membrane where the fluorescence either accumulates or appears diluted rather than being homogenously distributed. Based on a Ripley's analysis, the size of the domains was determined to be raccumulated=170±5 nm and rdilute>115±15 nm. We hypothesize that this structuring of the membrane is associated with the underlying cytoskeleton. Super-resolution imaging of motile cells becomes feasible using hydrogel embedding. The cytosolic leaflet of the plasma membrane of T. brucei is structured. Lipid-anchored eYFP preferentially localizes to domains of r = (170 ± 5) nm. Lipid-anchored eYFP appears diluted in domains of r > (115 ± 15) nm.
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Affiliation(s)
- Marius Glogger
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Ines Subota
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Anna Pezzarossa
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Anna-Lena Denecke
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB21QW, UK
| | - Susanne F Fenz
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany.
| | - Markus Engstler
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany.
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Hartel AJW, Glogger M, Jones NG, Abuillan W, Batram C, Hermann A, Fenz SF, Tanaka M, Engstler M. N-glycosylation enables high lateral mobility of GPI-anchored proteins at a molecular crowding threshold. Nat Commun 2016; 7:12870. [PMID: 27641538 PMCID: PMC5031801 DOI: 10.1038/ncomms12870] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/09/2016] [Indexed: 01/17/2023] Open
Abstract
The protein density in biological membranes can be extraordinarily high, but the impact of molecular crowding on the diffusion of membrane proteins has not been studied systematically in a natural system. The diversity of the membrane proteome of most cells may preclude systematic studies. African trypanosomes, however, feature a uniform surface coat that is dominated by a single type of variant surface glycoprotein (VSG). Here we study the density-dependence of the diffusion of different glycosylphosphatidylinositol-anchored VSG-types on living cells and in artificial membranes. Our results suggest that a specific molecular crowding threshold (MCT) limits diffusion and hence affects protein function. Obstacles in the form of heterologous proteins compromise the diffusion coefficient and the MCT. The trypanosome VSG-coat operates very close to its MCT. Importantly, our experiments show that N-linked glycans act as molecular insulators that reduce retarding intermolecular interactions allowing membrane proteins to function correctly even when densely packed.
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Affiliation(s)
- Andreas J. W. Hartel
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Marius Glogger
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Nicola G. Jones
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Wasim Abuillan
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
| | - Christopher Batram
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Anne Hermann
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Susanne F. Fenz
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Motomu Tanaka
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
- Institute for Integrated Cell-Material Science (WPI iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Markus Engstler
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
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Beletkaia E, Fenz SF, Pomp W, Snaar-Jagalska BE, Hogendoorn PW, Schmidt T. CXCR4 signaling is controlled by immobilization at the plasma membrane. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2016; 1863:607-16. [DOI: 10.1016/j.bbamcr.2015.12.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 12/23/2015] [Accepted: 12/29/2015] [Indexed: 12/14/2022]
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Sachse R, Dondapati SK, Fenz SF, Schmidt T, Kubick S. Membrane protein synthesis in cell-free systems: From bio-mimetic systems to bio-membranes. FEBS Lett 2014; 588:2774-81. [DOI: 10.1016/j.febslet.2014.06.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 05/30/2014] [Accepted: 06/02/2014] [Indexed: 01/28/2023]
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Fenz SF, Sachse R, Schmidt T, Kubick S. Cell-free synthesis of membrane proteins: tailored cell models out of microsomes. Biochim Biophys Acta 2013; 1838:1382-8. [PMID: 24370776 DOI: 10.1016/j.bbamem.2013.12.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/27/2013] [Accepted: 12/16/2013] [Indexed: 10/25/2022]
Abstract
Incorporation of proteins in biomimetic giant unilamellar vesicles (GUVs) is one of the hallmarks towards cell models in which we strive to obtain a better mechanistic understanding of the manifold cellular processes. The reconstruction of transmembrane proteins, like receptors or channels, into GUVs is a special challenge. This procedure is essential to make these proteins accessible to further functional investigation. Here we describe a strategy combining two approaches: cell-free eukaryotic protein expression for protein integration and GUV formation to prepare biomimetic cell models. The cell-free protein expression system in this study is based on insect lysates, which provide endoplasmic reticulum derived vesicles named microsomes. It enables signal-induced translocation and posttranslational modification of de novo synthesized membrane proteins. Combining these microsomes with synthetic lipids within the electroswelling process allowed for the rapid generation of giant proteo-liposomes of up to 50 μm in diameter. We incorporated various fluorescent protein-labeled membrane proteins into GUVs (the prenylated membrane anchor CAAX, the heparin-binding epithelial growth factor like factor Hb-EGF, the endothelin receptor ETB, the chemokine receptor CXCR4) and thus presented insect microsomes as functional modules for proteo-GUV formation. Single-molecule fluorescence microscopy was applied to detect and further characterize the proteins in the GUV membrane. To extend the options in the tailoring cell models toolbox, we synthesized two different membrane proteins sequentially in the same microsome. Additionally, we introduced biotinylated lipids to specifically immobilize proteo-GUVs on streptavidin-coated surfaces. We envision this achievement as an important first step toward systematic protein studies on technical surfaces.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands
| | - Rita Sachse
- Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany
| | - Thomas Schmidt
- Leiden Institute of Physics, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands
| | - Stefan Kubick
- Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany.
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Beletkaia E, Fenz SF, Snaar-Jagalska E, Hogendoorn P, Schmidt T. Understanding the Molecular Mechanism of Gradient Sensing. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
Tremendous progress has been made in recent years in understanding the working of the living cell, including its micro-anatomy, signalling networks, and regulation of genes. However, an understanding of cellular phenomena using fundamental laws starting from first principles is still very far away. Part of the reason is that a cell is an active and exquisitely complex system where every part is linked to the other. Thus, it is difficult or even impossible to design experiments that selectively and exclusively probe a chosen aspect of the cell. Various kinds of idealised systems and cell models have been used to circumvent this problem. An important example is a giant unilamellar vesicle (GUV, also called giant liposome), which provides a cell-sized confined volume to study biochemical reactions as well as self-assembly processes that occur on the membrane. The GUV membrane can be designed suitably to present selected, correctly-oriented cell-membrane proteins, whose mobility is confined to two dimensions. Here, we present recent advances in GUV design and the use of GUVs as cell models that enable quantitative testing leading to insight into the working of real cells. We briefly recapitulate important classical concepts in membrane biophysics emphasising the advantages and limitations of GUVs. We then present results obtained over the last decades using GUVs, choosing the formation of membrane domains and cell adhesion as examples for in-depth treatment. Insight into cell adhesion obtained using micro-interferometry is treated in detail. We conclude by summarising the open questions and possible future directions.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics: Physics of Life Processes, Leiden University, The Netherlands
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Fenz SF, Sachse R, Kubick S, Schmidt T. How to Tailor Giant Proteoliposomes. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Affiliation(s)
- Susanne F Fenz
- Institute of Complex Systems 7: Biomechanics Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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Fenz SF, Verheul C, Snaar-Jagalska E, Schmidt T. CXCR4-SDF1 Mediated Chemotaxis - from Tissue to the Single-Molecule Level. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
We present an improved analysis of reflection interference contrast microscopy (RICM) images, recorded to investigate model membrane systems that mimic cell adhesion. The model systems were giant unilamellar vesicles (GUV) adhering via specific ligand-receptor interactions to supported lipid bilayers (SLB) or to patterns of receptors. Conventional RICM and dual-wavelength RICM (DW-RICM) were applied to measure absolute optical distances between the biomembranes and planar substrates. We developed algorithms for a straightforward implementation of an automated, time-resolved reconstruction of the membrane conformations from RICM/DW-RICM images, taking into account all the interfaces in the system and blurring of the data due to camera noise. Finally, we demonstrate the validity and usefulness of this new approach by analyzing the topography and fluctuations of a bound membrane in the steady state and its dynamic adaptation to osmotic pressure changes. These measurements clearly show that macroscopic membrane flow through tightly adhered area is possible in our system.
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Affiliation(s)
- Cornelia Monzel
- Institute of Bio- and Nanosystems 4 (IBN 4), Research Centre Jülich, Wilhelm-Johnen-Strasse, 52425 Jülich, Germany
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Fenz SF, Merkel R, Sengupta K. Inter-Membrane Adhesion Mediated by Mobile Linkers: Effect of Receptor Shortage. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.4258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Abstract
We present a biomimetic model system for cell-cell adhesion consisting of a giant unilamellar vesicle (GUV) adhering via specific ligand-receptor interactions to a supported lipid bilayer (SLB). The modification of in-plane diffusion of tracer lipids and receptors in the SLB membrane due to adhesion to the GUV is reported. Adhesion was mediated by either biotin-neutravidin (an avidin analogue) or the extracellular domains of the cell adhesion molecule E-cadherin (Ecad). In the strong interaction (biotin-avidin) case, binding of soluble receptors to the SLB alone led to reduced diffusion of tracer lipids. From theoretical considerations, this could be attributed partially to introduction of obstacles and partially to viscous effects. Further specific binding of a GUV membrane caused additional slowing down of tracers (up to 15%) and immobilization of receptors, and led to accumulation of receptors in the adhesion zone until full coverage was achieved. The intermembrane distance was measured to be 7 nm from microinterferometry (RICM). We show that a crowding effect due to the accumulated receptors alone is not sufficient to account for the slowing downan additional friction from the membrane also plays a role. In the weak binding case (Ecad), the intermembrane distance was about 50 nm, corresponding to partial overlap of the Ecad domains. No significant change in diffusion of tracer lipids was observed upon either protein binding or subsequent vesicle binding. The former was probably due to very small effective size of the obstacles introduced into the bilayer by Ecad binding, whereas the latter was due to the fact that, with such high intermembrane distance, the resulting friction is negligible. We conclude that the effect of intermembrane adhesion on diffusion depends strongly on the choice of the receptors.
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Affiliation(s)
- Susanne F Fenz
- Institute of Bio- and Nanosystems (IBN), Research Centre Julich, 52425 Julich, Germany
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