51
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Abstract
Nowadays, live fluorescent microscopes allow us to study the dynamics of cellular processes in living cells with high spatial and temporal resolution. Since the implementation of this methodology to the field of clathrin-mediated endocytosis (CME), this approach has revolutionized our molecular understanding of clathrin-driven cellular uptake. Conventional live cell microscopy approaches are used to determine the precise functions of specific proteins or lipids in orchestrating CME. Here, we will describe, in depth, the procedure to investigate the contribution of membrane tension in regulating clathrin-dependent endocytosis. We will explain two alternative methods to manipulate membrane tension while performing live fluorescence microscopy: cellular swelling through osmotic shock and cellular stretching of cells grown on stretchable silicon inserts.
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52
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Lorenz-Guertin JM, Wilcox MR, Zhang M, Larsen MB, Pilli J, Schmidt BF, Bruchez MP, Johnson JW, Waggoner AS, Watkins SC, Jacob TC. A versatile optical tool for studying synaptic GABA A receptor trafficking. J Cell Sci 2017; 130:3933-3945. [PMID: 29025969 DOI: 10.1242/jcs.205286] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 09/26/2017] [Indexed: 12/26/2022] Open
Abstract
Live-cell imaging methods can provide critical real-time receptor trafficking measurements. Here, we describe an optical tool to study synaptic γ-aminobutyric acid (GABA) type A receptor (GABAAR) dynamics through adaptable fluorescent-tracking capabilities. A fluorogen-activating peptide (FAP) was genetically inserted into a GABAAR γ2 subunit tagged with pH-sensitive green fluorescent protein (γ2pHFAP). The FAP selectively binds and activates Malachite Green (MG) dyes that are otherwise non-fluorescent in solution. γ2pHFAP GABAARs are expressed at the cell surface in transfected cortical neurons, form synaptic clusters and do not perturb neuronal development. Electrophysiological studies show γ2pHFAP GABAARs respond to GABA and exhibit positive modulation upon stimulation with the benzodiazepine diazepam. Imaging studies using γ2pHFAP-transfected neurons and MG dyes show time-dependent receptor accumulation into intracellular vesicles, revealing constitutive endosomal and lysosomal trafficking. Simultaneous analysis of synaptic, surface and lysosomal receptors using the γ2pHFAP-MG dye approach reveals enhanced GABAAR turnover following a bicucculine-induced seizure paradigm, a finding not detected by standard surface receptor measurements. To our knowledge, this is the first application of the FAP-MG dye system in neurons, demonstrating the versatility to study nearly all phases of GABAAR trafficking.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Madeleine R Wilcox
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Ming Zhang
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Mads B Larsen
- Department of Cell Biology, Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jyotsna Pilli
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Brigitte F Schmidt
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Marcel P Bruchez
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Jon W Johnson
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Alan S Waggoner
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Simon C Watkins
- Department of Cell Biology, Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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53
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Yeh YH(J, Lin CM, Chen TT. Human IGF-I Eb-peptide induces cell attachment and lamellipodia outspread of metastatic breast carcinoma cells (MDA-MB-231). Exp Cell Res 2017; 358:199-208. [DOI: 10.1016/j.yexcr.2017.06.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/18/2017] [Accepted: 06/22/2017] [Indexed: 11/29/2022]
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54
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Flat clathrin lattices are dynamic actin-controlled hubs for clathrin-mediated endocytosis and signalling of specific receptors. Nat Commun 2017; 8:16068. [PMID: 28703125 PMCID: PMC5511353 DOI: 10.1038/ncomms16068] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 05/18/2017] [Indexed: 11/09/2022] Open
Abstract
Clathrin lattices at the plasma membrane coat both invaginated and flat regions forming clathrin-coated pits and clathrin plaques, respectively. The function and regulation of clathrin-coated pits in endocytosis are well understood but clathrin plaques remain enigmatic nanodomains. Here we use super-resolution microscopy, molecular genetics and cell biology to show that clathrin plaques contain the machinery for clathrin-mediated endocytosis and cell adhesion, and associate with both clathrin-coated pits and filamentous actin. We also find that actin polymerization promoted by N-WASP through the Arp2/3 complex is crucial for the regulation of plaques but not pits. Clathrin plaques oppose cell migration and undergo actin- and N-WASP-dependent disassembly upon activation of LPA receptor 1, but not EGF receptor. Most importantly, plaque disassembly correlates with the endocytosis of LPA receptor 1 and down-modulation of AKT activity. Thus, clathrin plaques serve as dynamic actin-controlled hubs for clathrin-mediated endocytosis and signalling that exhibit receptor specificity.
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55
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Li N, Zhao R, Sun Y, Ye Z, He K, Fang X. Single-molecule imaging and tracking of molecular dynamics in living cells. Natl Sci Rev 2017. [DOI: 10.1093/nsr/nww055] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Abstract
Unlike the ensemble-averaging measurements, the single-molecule imaging and tracking (SMIT) in living cells provides the real-time quantitative information about the locations, kinetics, dynamics and interactions of individual molecules in their native environments with high spatiotemporal resolution and minimal perturbation. The past decade has witnessed a transforming development in the methods of SMIT with living cells, including fluorescent probes, labeling strategies, fluorescence microscopy, and detection and tracking algorithms. In this review, we will discuss these aspects with a particular focus on their recent advancements. We will then describe representative single-molecule studies to illustrate how the single-molecule approaches can be applied to monitor biomolecular interaction/reaction dynamics, and extract the molecular mechanistic information for different cellular systems.
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Affiliation(s)
- Nan Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rong Zhao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yahong Sun
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zi Ye
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kangmin He
- Department of Cell Biology, Harvard Medical School, and Cellular and Molecular Medicine Program, Boston Children's Hospital, Boston, MA 02115, USA
| | - Xiaohong Fang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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56
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Masuda S, Yanase Y, Usukura E, Ryuzaki S, Wang P, Okamoto K, Kuboki T, Kidoaki S, Tamada K. High-resolution imaging of a cell-attached nanointerface using a gold-nanoparticle two-dimensional sheet. Sci Rep 2017. [PMID: 28623338 PMCID: PMC5473937 DOI: 10.1038/s41598-017-04000-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
This paper proposes a simple, effective, non-scanning method for the visualization of a cell-attached nanointerface. The method uses localized surface plasmon resonance (LSPR) excited homogeneously on a two-dimensional (2D) self-assembled gold-nanoparticle sheet. The LSPR of the gold-nanoparticle sheet provides high-contrast interfacial images due to the confined light within a region a few tens of nanometers from the particles and the enhancement of fluorescence. Test experiments on rat basophilic leukemia (RBL-2H3) cells with fluorescence-labeled actin filaments revealed high axial and lateral resolution even under a regular epifluorescence microscope, which produced higher quality images than those captured under a total internal reflection fluorescence (TIRF) microscope. This non-scanning-type, high-resolution imaging method will be an effective tool for monitoring interfacial phenomena that exhibit relatively rapid reaction kinetics in various cellular and molecular dynamics.
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Affiliation(s)
- Shihomi Masuda
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Yuhki Yanase
- Graduate School of Biomedical & Health Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima City Hiroshima, 734-8553, Japan
| | - Eiji Usukura
- Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Sou Ryuzaki
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Pangpang Wang
- Education Center for Global Leaders in Molecular Systems for Devices, Kyushu University, Fukuoka, 819-0395, Japan
| | - Koichi Okamoto
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Thasaneeya Kuboki
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Satoru Kidoaki
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Kaoru Tamada
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
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57
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Irajizad E, Walani N, Veatch SL, Liu AP, Agrawal A. Clathrin polymerization exhibits high mechano-geometric sensitivity. SOFT MATTER 2017; 13:1455-1462. [PMID: 28124714 PMCID: PMC5452080 DOI: 10.1039/c6sm02623k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
How tension modulates cellular transport has become a topic of interest in the recent past. However, the effect of tension on clathrin assembly and vesicle growth remains less understood. Here, we use the classical Helfrich theory to predict the energetic cost that clathrin is required to pay to remodel the membrane at different stages of vesicle formation. Our study reveals that this energetic cost is highly sensitive to not only the tension in the membrane but also to the instantaneous geometry of the membrane during shape evolution. Our study predicts a sharp reduction in clathrin coat size in the intermediate tension regime (0.01-0.1 mN m-1). Remarkably, the natural propensity of the membrane to undergo bending beyond the Ω shape causes a significant decrease in the energy needed from clathrin to drive vesicle growth. Our studies in mammalian cells confirm a reduction in clathrin coat size in an increased tension environment. In addition, our findings suggest that the two apparently distinct clathrin assembly modes, namely coated pits and coated plaques, observed in experimental investigations might be a consequence of varied tensions in the plasma membrane. Overall, the mechano-geometric sensitivity revealed in this study might also be at play during the polymerization of other membrane remodeling proteins.
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Affiliation(s)
- Ehsan Irajizad
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA
| | - Nikhil Walani
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, MI, USA
| | - Allen P Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Ashutosh Agrawal
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA.
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58
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Abstract
Lipids and nucleic acids (NAs) can hierarchically self-organize into a variety of nanostructures of increasingly complex geometries such as the 1D lamellar, 2D hexagonal, and 3D bicontinuous cubic phases. The diversity and complexity of those lipid-NA assemblies are interesting from a fundamental perspective as well as being relevant to the performance in gene delivery and gene silencing applications. The finding that not only the chemical make of the lipid-NA constructs, but their actual supramolecular organization, affects their gene transfection and silencing efficiencies has inspired physicists, chemists, and engineers to this field of research. At the moment it remains an open question how exactly the different lipid-NA structures interact with cells and organelles in order to output an optimal response. This article reviews our current understanding of the structures of different lipid-NA complexes and the corresponding cellular interaction mechanisms. The recent advances in designing optimal lipid-based NA carriers will be introduced with an emphasis on the structure-function relations.
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Affiliation(s)
- Minjee Kang
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Hojun Kim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Cecilia Leal
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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59
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Gahl RF, Dwivedi P, Tjandra N. Bcl-2 proteins bid and bax form a network to permeabilize the mitochondria at the onset of apoptosis. Cell Death Dis 2016; 7:e2424. [PMID: 27763642 PMCID: PMC5133987 DOI: 10.1038/cddis.2016.320] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 08/23/2016] [Accepted: 09/05/2016] [Indexed: 12/23/2022]
Abstract
The most critical step in the initiation of apoptosis is the activation of the Bcl-2 family of proteins to oligomerize and permeabilize the outer-mitochondrial membrane (OMM). As this step results in the irreversible release of factors that enhance cellular degradation, it is the point of no return in programmed cell death and would be an ideal therapeutic target. However, the arrangement of the Bcl-2 proteins in the OMM during permeabilization still remains unknown. It is also unclear whether the Bcl-2 protein, Bid, directly participates in the formation of the oligomers in live cells, even though it is cleaved and translocates to the OMM at the initiation of apoptosis. Therefore, we utilized confocal microscopy to measure Förster resonance energy transfer (FRET) efficiencies in live cells to determine the conformation(s) and intermolecular contacts of Bid within these Bcl-2 oligomers. We found that Bid adopts an extended conformation, which appears to be critical for its association with the mitochondrial membrane. This conformation is also important for intermolecular contacts within the Bid oligomer. More importantly for the first time, direct intermolecular contacts between Bid and Bax were observed, thereby, confirming Bid as a key component of these oligomers. Furthermore, the observed FRET efficiencies allowed us to propose an oligomeric arrangement of Bid, Bax, and possibly other members of the Bcl-2 family of proteins that form a self-propagating network that permeabilizes the OMM.
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Affiliation(s)
- Robert F Gahl
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda 20892, MD, USA
| | - Pallavi Dwivedi
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda 20892, MD, USA
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda 20892, MD, USA
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60
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Klaus CJS, Raghunathan K, DiBenedetto E, Kenworthy AK. Analysis of diffusion in curved surfaces and its application to tubular membranes. Mol Biol Cell 2016; 27:3937-3946. [PMID: 27733625 PMCID: PMC5170615 DOI: 10.1091/mbc.e16-06-0445] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 09/08/2016] [Accepted: 10/04/2016] [Indexed: 11/11/2022] Open
Abstract
Diffusion of particles in curved surfaces is inherently complex compared with diffusion in a flat membrane, owing to the nonplanarity of the surface. The consequence of such nonplanar geometry on diffusion is poorly understood but is highly relevant in the case of cell membranes, which often adopt complex geometries. To address this question, we developed a new finite element approach to model diffusion on curved membrane surfaces based on solutions to Fick's law of diffusion and used this to study the effects of geometry on the entry of surface-bound particles into tubules by diffusion. We show that variations in tubule radius and length can distinctly alter diffusion gradients in tubules over biologically relevant timescales. In addition, we show that tubular structures tend to retain concentration gradients for a longer time compared with a comparable flat surface. These findings indicate that sorting of particles along the surfaces of tubules can arise simply as a geometric consequence of the curvature without any specific contribution from the membrane environment. Our studies provide a framework for modeling diffusion in curved surfaces and suggest that biological regulation can emerge purely from membrane geometry.
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Affiliation(s)
| | - Krishnan Raghunathan
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232
| | | | - Anne K Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232 .,Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
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61
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Tinevez JY, Perry N, Schindelin J, Hoopes GM, Reynolds GD, Laplantine E, Bednarek SY, Shorte SL, Eliceiri KW. TrackMate: An open and extensible platform for single-particle tracking. Methods 2016; 115:80-90. [PMID: 27713081 DOI: 10.1016/j.ymeth.2016.09.016] [Citation(s) in RCA: 1724] [Impact Index Per Article: 215.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 09/29/2016] [Accepted: 09/30/2016] [Indexed: 01/12/2023] Open
Abstract
We present TrackMate, an open source Fiji plugin for the automated, semi-automated, and manual tracking of single-particles. It offers a versatile and modular solution that works out of the box for end users, through a simple and intuitive user interface. It is also easily scriptable and adaptable, operating equally well on 1D over time, 2D over time, 3D over time, or other single and multi-channel image variants. TrackMate provides several visualization and analysis tools that aid in assessing the relevance of results. The utility of TrackMate is further enhanced through its ability to be readily customized to meet specific tracking problems. TrackMate is an extensible platform where developers can easily write their own detection, particle linking, visualization or analysis algorithms within the TrackMate environment. This evolving framework provides researchers with the opportunity to quickly develop and optimize new algorithms based on existing TrackMate modules without the need of having to write de novo user interfaces, including visualization, analysis and exporting tools. The current capabilities of TrackMate are presented in the context of three different biological problems. First, we perform Caenorhabditis-elegans lineage analysis to assess how light-induced damage during imaging impairs its early development. Our TrackMate-based lineage analysis indicates the lack of a cell-specific light-sensitive mechanism. Second, we investigate the recruitment of NEMO (NF-κB essential modulator) clusters in fibroblasts after stimulation by the cytokine IL-1 and show that photodamage can generate artifacts in the shape of TrackMate characterized movements that confuse motility analysis. Finally, we validate the use of TrackMate for quantitative lifetime analysis of clathrin-mediated endocytosis in plant cells.
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Affiliation(s)
| | - Nick Perry
- Imagopole, Citech, Institut Pasteur, 75724 Paris, France
| | - Johannes Schindelin
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Genevieve M Hoopes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Gregory D Reynolds
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Emmanuel Laplantine
- Laboratory of Signaling and Pathogenesis, Centre National de la Recherche Scientifique, UMR 3691, Institut Pasteur, 75724 Paris, France
| | - Sebastian Y Bednarek
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | - Kevin W Eliceiri
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI 53706, USA; Morgridge Institute for Research, Madison, WI 53719, USA
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62
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Lampe M, Vassilopoulos S, Merrifield C. Clathrin coated pits, plaques and adhesion. J Struct Biol 2016; 196:48-56. [DOI: 10.1016/j.jsb.2016.07.009] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/11/2016] [Accepted: 07/13/2016] [Indexed: 11/27/2022]
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63
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Aguet F, Upadhyayula S, Gaudin R, Chou YY, Cocucci E, He K, Chen BC, Mosaliganti K, Pasham M, Skillern W, Legant WR, Liu TL, Findlay G, Marino E, Danuser G, Megason S, Betzig E, Kirchhausen T. Membrane dynamics of dividing cells imaged by lattice light-sheet microscopy. Mol Biol Cell 2016; 27:3418-3435. [PMID: 27535432 PMCID: PMC5221578 DOI: 10.1091/mbc.e16-03-0164] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 08/03/2016] [Indexed: 12/02/2022] Open
Abstract
Lattice light-sheet microscopy is used to examine two problems in membrane dynamics—molecular events in clathrin-coated pit formation and changes in cell shape during cell division. This methodology sets a new standard for imaging membrane dynamics in single cells and multicellular assemblies. Membrane remodeling is an essential part of transferring components to and from the cell surface and membrane-bound organelles and for changes in cell shape, which are particularly critical during cell division. Earlier analyses, based on classical optical live-cell imaging and mostly restricted by technical necessity to the attached bottom surface, showed persistent formation of endocytic clathrin pits and vesicles during mitosis. Taking advantage of the resolution, speed, and noninvasive illumination of the newly developed lattice light-sheet fluorescence microscope, we reexamined their assembly dynamics over the entire cell surface and found that clathrin pits form at a lower rate during late mitosis. Full-cell imaging measurements of cell surface area and volume throughout the cell cycle of single cells in culture and in zebrafish embryos showed that the total surface increased rapidly during the transition from telophase to cytokinesis, whereas cell volume increased slightly in metaphase and was relatively constant during cytokinesis. These applications demonstrate the advantage of lattice light-sheet microscopy and enable a new standard for imaging membrane dynamics in single cells and multicellular assemblies.
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Affiliation(s)
- François Aguet
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Srigokul Upadhyayula
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Raphaël Gaudin
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Yi-Ying Chou
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Emanuele Cocucci
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Kangmin He
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Bi-Chang Chen
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | | | - Mithun Pasham
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Wesley Skillern
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Wesley R Legant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Tsung-Li Liu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Greg Findlay
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Eric Marino
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Gaudenz Danuser
- Lyda Hill Department of Bioinformatics, UT Southwestern Medical Center, Dallas, TX 75390
| | - Sean Megason
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Tom Kirchhausen
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115 .,Departments of Cell Biology and Pediatrics, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
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64
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Zumthor JP, Cernikova L, Rout S, Kaech A, Faso C, Hehl AB. Static Clathrin Assemblies at the Peripheral Vacuole-Plasma Membrane Interface of the Parasitic Protozoan Giardia lamblia. PLoS Pathog 2016; 12:e1005756. [PMID: 27438602 PMCID: PMC4954726 DOI: 10.1371/journal.ppat.1005756] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/18/2016] [Indexed: 11/19/2022] Open
Abstract
Giardia lamblia is a parasitic protozoan that infects a wide range of vertebrate hosts including humans. Trophozoites are non-invasive but associate tightly with the enterocyte surface of the small intestine. This narrow ecological specialization entailed extensive morphological and functional adaptations during host-parasite co-evolution, including a distinctly polarized array of endocytic organelles termed peripheral vacuoles (PVs), which are confined to the dorsal cortical region exposed to the gut lumen and are in close proximity to the plasma membrane (PM). Here, we investigated the molecular consequences of these adaptations on the Giardia endocytic machinery and membrane coat complexes. Despite the absence of canonical clathrin coated vesicles in electron microscopy, Giardia possesses conserved PV-associated clathrin heavy chain (GlCHC), dynamin-related protein (GlDRP), and assembly polypeptide complex 2 (AP2) subunits, suggesting a novel function for GlCHC and its adaptors. We found that, in contrast to GFP-tagged AP2 subunits and DRP, CHC::GFP reporters have no detectable turnover in living cells, indicating fundamental differences in recruitment to the membrane and disassembly compared to previously characterized clathrin coats. Histochemical localization in electron tomography showed that these long-lived GlCHC assemblies localized at distinctive approximations between the plasma and PV membrane. A detailed protein interactome of GlCHC revealed all of the conserved factors in addition to novel or highly diverged proteins, including a putative clathrin light chain and lipid-binding proteins. Taken together, our data provide strong evidence for giardial CHC as a component of highly stable assemblies at PV-PM junctions that likely have a central role in organizing continuities between the PM and PV membranes for controlled sampling of the fluid environment. This suggests a novel function for CHC in Giardia and the extent of molecular remodeling of endocytosis in this species. In canonical clathrin mediated endocytosis (CME) models, the concerted action of ca. 50 proteins mediates the uptake of extracellular components. The key player in this process is clathrin which coats transport intermediates called clathrin coated vesicles (CCV). The intestinal parasite Giardia lamblia has undergone extensive remodeling during colonization of the mammalian duodenum. Here, we report on unique features of this parasite’s endocytic system, consisting of fixed peripheral vacuoles (PV) in close proximity to the exposed plasma membrane (PM), with no discernible CCVs. Using state-of-the-art imaging strategies, we show that the surface of Giardia trophozoites is pock-marked with PM invaginations reaching to the underlying PV membrane. Co-immunoprecipitation and analysis of protein dynamics reveal that, in line with the absence of CCVs, giardial clathrin assemblies have no dynamic behavior. CHC still remains associated to AP2 and dynamin, both conserved dynamic CME components, and to a newly identified putative clathrin light chain. The emerging model calls for giardial clathrin organized into static cores surrounded by dynamic interaction partners, and most likely involved in the regulation of fusion between the PM and the PVs in a “kiss-and-flush”-like mechanism. This suggests that Giardia harbors a conceptually novel function for clathrin in endocytosis, which might be a consequence of host-parasite co-evolution.
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Affiliation(s)
| | - Lenka Cernikova
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
| | - Samuel Rout
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Carmen Faso
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
- * E-mail: (CF); (ABH)
| | - Adrian B. Hehl
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
- * E-mail: (CF); (ABH)
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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-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] [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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66
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Banerjee A, Berezhkovskii A, Nossal R. Kinetics of cellular uptake of viruses and nanoparticles via clathrin-mediated endocytosis. Phys Biol 2016; 13:016005. [PMID: 26871680 PMCID: PMC6748044 DOI: 10.1088/1478-3975/13/1/016005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Several viruses exploit clathrin-mediated endocytosis to gain entry into host cells. This process is also used extensively in biomedical applications to deliver nanoparticles (NPs) to diseased cells. The internalization of these nano-objects is controlled by the assembly of a clathrin-containing protein coat on the cytoplasmic side of the plasma membrane, which drives the invagination of the membrane and the formation of a cargo-containing endocytic vesicle. Current theoretical models of receptor-mediated endocytosis of viruses and NPs do not explicitly take coat assembly into consideration. In this paper we study cellular uptake of viruses and NPs with a focus on coat assembly. We characterize the internalization process by the mean time between the binding of a particle to the membrane and its entry into the cell. Using a coarse-grained model which maps the stochastic dynamics of coat formation onto a one-dimensional random walk, we derive an analytical formula for this quantity. A study of the dependence of the mean internalization time on NP size shows that there is an upper bound above which this time becomes extremely large, and an optimal size at which it attains a minimum. Our estimates of these sizes compare well with experimental data. We also study the sensitivity of the obtained results on coat parameters to identify factors which significantly affect the internalization kinetics.
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Affiliation(s)
- Anand Banerjee
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health, and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexander Berezhkovskii
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ralph Nossal
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health, and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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67
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Ybe JA. Novel clathrin activity: developments in health and disease. Biomol Concepts 2015; 5:175-82. [PMID: 25372751 DOI: 10.1515/bmc-2013-0040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 02/18/2014] [Indexed: 12/21/2022] Open
Abstract
Clathrin self-assembles into a coat around vesicles filled with cargo such as nutrients, hormones, and proteins destined for degradation. Recent developments indicate clathrin is not a specialist, but is involved in different processes relevant to health and disease. Clathrin is used to strengthen centrosomes and mitotic spindles essential for chromosome segregation in cell division. In Wnt signaling, clathrin is a component of signalosomes on the plasma membrane needed to produce functional Wnt receptors. In glucose metabolism, a muscle-specific isoform, CHC22 clathrin, is key to the formation of storage compartments for GLUT4 receptor, and CHC22 dysfunction has been tied to type 2 diabetes. The activity of clathrin to self-assemble and to work with huntingtin-interacting proteins to organize actin is exploited by Listeria and enteropathic Escherichia coli in their infection pathways. Finally, there is an important connection between clathrin and human malignancies. Clathrin is argued to help transactivate tumor suppressor p53 that controls specific genes in DNA repair and apoptosis. However, this is debatable because trimeric clathrin must be made monomeric. To get insight on how the clathrin structure could be converted, the crystal structure of the trimerization domain is used in the development of the detrimerization switch hypothesis. This novel hypothesis will be relevant if connections continue to be found between CHC17 and p53 anti-cancer activity in the nucleus.
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68
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Crupi MJF, Yoganathan P, Bone LN, Lian E, Fetz A, Antonescu CN, Mulligan LM. Distinct Temporal Regulation of RET Isoform Internalization: Roles of Clathrin and AP2. Traffic 2015; 16:1155-73. [DOI: 10.1111/tra.12315] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 08/19/2015] [Accepted: 08/19/2015] [Indexed: 01/08/2023]
Affiliation(s)
- Mathieu J. F. Crupi
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Pathology & Molecular Medicine; Queen's University; Kingston Ontario K7L 3N6 Canada
| | - Piriya Yoganathan
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Pathology & Molecular Medicine; Queen's University; Kingston Ontario K7L 3N6 Canada
| | - Leslie N. Bone
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B 2K3 Canada
| | - Eric Lian
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Pathology & Molecular Medicine; Queen's University; Kingston Ontario K7L 3N6 Canada
| | - Andrew Fetz
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Pathology & Molecular Medicine; Queen's University; Kingston Ontario K7L 3N6 Canada
| | - Costin N. Antonescu
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B 2K3 Canada
| | - Lois M. Mulligan
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Pathology & Molecular Medicine; Queen's University; Kingston Ontario K7L 3N6 Canada
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69
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Molecular dynamics at the endocytic portal and regulations of endocytic and recycling traffics. Eur J Cell Biol 2015; 94:235-48. [DOI: 10.1016/j.ejcb.2015.04.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 04/02/2015] [Accepted: 04/08/2015] [Indexed: 02/01/2023] Open
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Hazan-Halevy I, Rosenblum D, Weinstein S, Bairey O, Raanani P, Peer D. Cell-specific uptake of mantle cell lymphoma-derived exosomes by malignant and non-malignant B-lymphocytes. Cancer Lett 2015; 364:59-69. [PMID: 25933830 DOI: 10.1016/j.canlet.2015.04.026] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 04/22/2015] [Accepted: 04/23/2015] [Indexed: 12/14/2022]
Abstract
Mantle cell lymphoma (MCL) is an aggressive and incurable mature B cell neoplasm. The current treatments are based on chemotherapeutics and new class of drugs (e.g. Ibrutinib(®)), which in most cases ends with tumor resistance and relapse. Therefore, further development of novel therapeutic modalities is needed. Exosomes are natural extracellular vesicles, which play an important role in intercellular communication. The specificity of exosome uptake by different target cells remains unknown. In this study, we observed that MCL exosomes are taken up rapidly and preferentially by MCL cells. Only a minor fraction of exosomes was internalized into T-cell leukemia and bone marrow stroma cell lines, when these cells were co-cultured with MCL cells. Moreover, MCL patients' exosomes were taken up by both healthy and patients' B-lymphocytes with no apparent internalization to T lymphocytes and NK cells. Exosome internalization was not inhibited by specific siRNA against caveolin1 and clathrin but was found to be mediated by a cholesterol-dependent pathway. These findings demonstrate natural specificity of exosomes to B-lymphocytes and ultimately might be used for therapeutic intervention in B cells malignancies.
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Affiliation(s)
- Inbal Hazan-Halevy
- Laboratory of NanoMedicine, Department of Cell Research & Immunology, Department of Materials Science and Engineering, Tel Aviv University, Tel Aviv 69978, Israel; Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Daniel Rosenblum
- Laboratory of NanoMedicine, Department of Cell Research & Immunology, Department of Materials Science and Engineering, Tel Aviv University, Tel Aviv 69978, Israel; Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shiri Weinstein
- Laboratory of NanoMedicine, Department of Cell Research & Immunology, Department of Materials Science and Engineering, Tel Aviv University, Tel Aviv 69978, Israel; Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Osnat Bairey
- Institute of Hematology, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel
| | - Pia Raanani
- Institute of Hematology, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel
| | - Dan Peer
- Laboratory of NanoMedicine, Department of Cell Research & Immunology, Department of Materials Science and Engineering, Tel Aviv University, Tel Aviv 69978, Israel; Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel.
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71
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Kural C, Akatay AA, Gaudin R, Chen BC, Legant WR, Betzig E, Kirchhausen T. Asymmetric formation of coated pits on dorsal and ventral surfaces at the leading edges of motile cells and on protrusions of immobile cells. Mol Biol Cell 2015; 26:2044-53. [PMID: 25851602 PMCID: PMC4472015 DOI: 10.1091/mbc.e15-01-0055] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/02/2015] [Indexed: 01/19/2023] Open
Abstract
Clathrin/AP2-coated vesicles are the principal endocytic carriers originating at the plasma membrane. In the experiments reported here, we used spinning-disk confocal and lattice light-sheet microscopy to study the assembly dynamics of coated pits on the dorsal and ventral membranes of migrating U373 glioblastoma cells stably expressing AP2 tagged with enhanced green fluorescence (AP2-EGFP) and on lateral protrusions from immobile SUM159 breast carcinoma cells, gene-edited to express AP2-EGFP. On U373 cells, coated pits initiated on the dorsal membrane at the front of the lamellipodium and at the approximate boundary between the lamellipodium and lamella and continued to grow as they were swept back toward the cell body; coated pits were absent from the corresponding ventral membrane. We observed a similar dorsal/ventral asymmetry on membrane protrusions from SUM159 cells. Stationary coated pits formed and budded on the remainder of the dorsal and ventral surfaces of both types of cells. These observations support a previously proposed model that invokes net membrane deposition at the leading edge due to an imbalance between the endocytic and exocytic membrane flow at the front of a migrating cell.
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Affiliation(s)
- Comert Kural
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115 Department of Physics, The Ohio State University, Columbus, OH 43210
| | - Ahmet Ata Akatay
- Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210
| | - Raphaël Gaudin
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115
| | - Bi-Chang Chen
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Wesley R Legant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Tom Kirchhausen
- Department of Cell Biology, Harvard Medical School, and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115 Department of Pediatrics, Harvard Medical School, Boston, MA 02115
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72
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Schifferer M, Feng S, Stein F, Tischer C, Schultz C. Reversible chemical dimerizer-induced recovery of PIP2 levels moves clathrin to the plasma membrane. Bioorg Med Chem 2015; 23:2862-7. [PMID: 25840797 DOI: 10.1016/j.bmc.2015.03.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/16/2015] [Accepted: 03/18/2015] [Indexed: 12/24/2022]
Abstract
Chemical dimerizers are powerful non-invasive tools for bringing molecules together inside intact cells. We recently introduced a rapidly reversible chemical dimerizer system which enables transient translocation of enzymes to and from the plasma membrane (PM). Here we have applied this system to transiently activate phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown at the PM via translocation of phosphoinositide 5-phosphatase (5Ptase). We found that the PIP2 sensor phospholipase C-δ PH domain (PLCδ-PH) is released from the PM upon addition of the reversible chemical dimerizer rCD1. By outcompeting rCD1, rapid release of the 5Ptase from the PM is followed by PIP2 recovery. This permits the observation of the PIP2-dependent clathrin assembly at the PM.
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Affiliation(s)
- Martina Schifferer
- European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Suihan Feng
- European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Frank Stein
- European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Christian Tischer
- European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Carsten Schultz
- European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany.
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73
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Picco A, Mund M, Ries J, Nédélec F, Kaksonen M. Visualizing the functional architecture of the endocytic machinery. eLife 2015; 4. [PMID: 25675087 PMCID: PMC4357291 DOI: 10.7554/elife.04535] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 02/10/2015] [Indexed: 01/08/2023] Open
Abstract
Clathrin-mediated endocytosis is an essential process that forms vesicles from the plasma membrane. Although most of the protein components of the endocytic protein machinery have been thoroughly characterized, their organization at the endocytic site is poorly understood. We developed a fluorescence microscopy method to track the average positions of yeast endocytic proteins in relation to each other with a time precision below 1 s and with a spatial precision of ∼10 nm. With these data, integrated with shapes of endocytic membrane intermediates and with superresolution imaging, we could visualize the dynamic architecture of the endocytic machinery. We showed how different coat proteins are distributed within the coat structure and how the assembly dynamics of N-BAR proteins relate to membrane shape changes. Moreover, we found that the region of actin polymerization is located at the base of the endocytic invagination, with the growing ends of filaments pointing toward the plasma membrane. DOI:http://dx.doi.org/10.7554/eLife.04535.001 Cells take up proteins and other useful material (called cargo) from their external environment through a process known as endocytosis. To start with, the cargo accumulates in a patch on the surface of the cell. On the inner side of the cell's membrane, a protein called clathrin gathers around the patch of cargo. Clathrin molecules and many other proteins bind together to make a lattice-like coat that causes the membrane to curve inwards and form a pocket that contains the cargo. This continues until the cargo is completely surrounded by membrane and eventually forms a bubble-like structure, or ‘vesicle’, that moves into the cell. More than 50 other proteins are involved in the endocytosis. These proteins arrive at the site of endocytosis in a particular order, complete their tasks and then move away to be used in further rounds of endocytosis. It is not clear how these proteins are organized to complete these steps because it is technically difficult to track the movements of many proteins at the same time. Here, Picco et al. developed a new fluorescence microscopy method that enabled them to track the positions of many of the proteins involved in endocytosis in yeast cells in real time. The experiments revealed when the proteins arrived at the site of endocytosis and how they assembled in relation to the membrane. For example, a group of proteins called N-BAR proteins formed an extended lattice covering the sides of the pocket that forms as the membrane curves inwards. To transform the flat membrane into a vesicle, a network of filaments made of a protein called actin needs to form at the site of endocytosis. The new method shows that the actin filaments grow in a small region at the base of the developing vesicle. By combining different types of microscopy data, Picco et al. were able to build a comprehensive model describing when the proteins involved in endocytosis move and assemble. The next challenge will be to understand the physics behind the molecular machine composed of these many proteins and the cell membrane. DOI:http://dx.doi.org/10.7554/eLife.04535.002
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Affiliation(s)
- Andrea Picco
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Markus Mund
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jonas Ries
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - François Nédélec
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Marko Kaksonen
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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74
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Simunovic M, Bassereau P. Reshaping biological membranes in endocytosis: crossing the configurational space of membrane-protein interactions. Biol Chem 2015; 395:275-83. [PMID: 24353142 DOI: 10.1515/hsz-2013-0242] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 12/16/2013] [Indexed: 11/15/2022]
Abstract
Lipid membranes are highly dynamic. Over several decades, physicists and biologists have uncovered a number of ways they can change the shape of membranes or alter their phase behavior. In cells, the intricate action of membrane proteins drives these processes. Considering the highly complex ways proteins interact with biological membranes, molecular mechanisms of membrane remodeling still remain unclear. When studying membrane remodeling phenomena, researchers often observe different results, leading them to disparate conclusions on the physiological course of such processes. Here we discuss how combining research methodologies and various experimental conditions contributes to the understanding of the entire phase space of membrane-protein interactions. Using the example of clathrin-mediated endocytosis we try to distinguish the question 'how can proteins remodel the membrane?' from 'how do proteins remodel the membrane in the cell?' In particular, we consider how altering physical parameters may affect the way membrane is remodeled. Uncovering the full range of physical conditions under which membrane phenomena take place is key in understanding the way cells take advantage of membrane properties in carrying out their vital tasks.
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75
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Ishikawa Y, Maeda M, Pasham M, Aguet F, Tacheva-Grigorova SK, Masuda T, Yi H, Lee SU, Xu J, Teruya-Feldstein J, Ericsson M, Mullally A, Heuser J, Kirchhausen T, Maeda T. Role of the clathrin adaptor PICALM in normal hematopoiesis and polycythemia vera pathophysiology. Haematologica 2014; 100:439-51. [PMID: 25552701 DOI: 10.3324/haematol.2014.119537] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Clathrin-dependent endocytosis is an essential cellular process shared by all cell types. Despite this, precisely how endocytosis is regulated in a cell-type-specific manner and how this key pathway functions physiologically or pathophysiologically remain largely unknown. PICALM, which encodes the clathrin adaptor protein PICALM, was originally identified as a component of the CALM/AF10 leukemia oncogene. Here we show, by employing a series of conditional Picalm knockout mice, that PICALM critically regulates transferrin uptake in erythroid cells by functioning as a cell-type-specific regulator of transferrin receptor endocytosis. While transferrin receptor is essential for the development of all hematopoietic lineages, Picalm was dispensable for myeloid and B-lymphoid development. Furthermore, global Picalm inactivation in adult mice did not cause gross defects in mouse fitness, except for anemia and a coat color change. Freeze-etch electron microscopy of primary erythroblasts and live-cell imaging of murine embryonic fibroblasts revealed that Picalm function is required for efficient clathrin coat maturation. We showed that the PICALM PIP2 binding domain is necessary for transferrin receptor endocytosis in erythroblasts and absolutely essential for erythroid development from mouse hematopoietic stem/progenitor cells in an erythroid culture system. We further showed that Picalm deletion entirely abrogated the disease phenotype in a Jak2(V617F) knock-in murine model of polycythemia vera. Our findings provide new insights into the regulation of cell-type-specific transferrin receptor endocytosis in vivo. They also suggest a new strategy to block cellular uptake of transferrin-bound iron, with therapeutic potential for disorders characterized by inappropriate red blood cell production, such as polycythemia vera.
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Affiliation(s)
- Yuichi Ishikawa
- Division of Hematopoietic Stem Cell and Leukemia Research, Beckman Research Institute of the City of Hope, Duarte, CA, USA Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA Department of Hematology and Oncology, Nagoya University Graduate School of Medicine, Japan
| | - Manami Maeda
- Division of Hematopoietic Stem Cell and Leukemia Research, Beckman Research Institute of the City of Hope, Duarte, CA, USA Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Mithun Pasham
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA Department of Pediatrics Harvard Medical School, Boston, MA, USA Program in Cellular & Molecular Medicine, Boston Children's Hospital, MA, USA
| | - Francois Aguet
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Silvia K Tacheva-Grigorova
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA Department of Pediatrics Harvard Medical School, Boston, MA, USA Program in Cellular & Molecular Medicine, Boston Children's Hospital, MA, USA
| | - Takeshi Masuda
- Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Hai Yi
- Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA Department of Hematology, General Hospital of Chengdu Military Region, Chengdu, China
| | - Sung-Uk Lee
- Division of Hematopoietic Stem Cell and Leukemia Research, Beckman Research Institute of the City of Hope, Duarte, CA, USA Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Jian Xu
- Children's Research Institute, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Julie Teruya-Feldstein
- Department of Pathology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Maria Ericsson
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Ann Mullally
- Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - John Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Tom Kirchhausen
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA Department of Pediatrics Harvard Medical School, Boston, MA, USA Program in Cellular & Molecular Medicine, Boston Children's Hospital, MA, USA
| | - Takahiro Maeda
- Division of Hematopoietic Stem Cell and Leukemia Research, Beckman Research Institute of the City of Hope, Duarte, CA, USA Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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76
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Merrifield CJ, Kaksonen M. Endocytic accessory factors and regulation of clathrin-mediated endocytosis. Cold Spring Harb Perspect Biol 2014; 6:a016733. [PMID: 25280766 DOI: 10.1101/cshperspect.a016733] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Up to 60 different proteins are recruited to the site of clathrin-mediated endocytosis in an ordered sequence. These accessory proteins have roles during all the different stages of clathrin-mediated endocytosis. First, they participate in the initiation of the endocytic event, thereby determining when and where endocytic vesicles are made; later they are involved in the maturation of the clathrin coat, recruitment of specific cargo molecules, bending of the membrane, and finally in scission and uncoating of the nascent vesicle. In addition, many of the accessory components are involved in regulating and coupling the actin cytoskeleton to the endocytic membrane. We will discuss the different accessory components and their various roles. Most of the data comes from studies performed with cultured mammalian cells or yeast cells. The process of endocytosis is well conserved between these different organisms, but there are also many interesting differences that may shed light on the mechanistic principles of endocytosis.
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Affiliation(s)
- Christien J Merrifield
- Laboratoire d'Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique UPR3082, 91198 Gif-sur-Yvette, France
| | - Marko Kaksonen
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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77
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Cohen M, Kitsberg D, Tsytkin S, Shulman M, Aroeti B, Nahmias Y. Live imaging of GLUT2 glucose-dependent trafficking and its inhibition in polarized epithelial cysts. Open Biol 2014; 4:140091. [PMID: 25056286 PMCID: PMC4118605 DOI: 10.1098/rsob.140091] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 07/02/2014] [Indexed: 01/20/2023] Open
Abstract
GLUT2 is a facilitative glucose transporter, expressed in polarized epithelial cells of the liver, intestine, kidney and pancreas, where it plays a critical role in glucose homeostasis. Together with SGLT1/2, it mediates glucose absorption in metabolic epithelial tissues, where it can be translocated apically upon high glucose exposure. To track the subcellular localization and dynamics of GLUT2, we created an mCherry-hGLUT2 fusion protein and expressed it in multicellular kidney cysts, a major site of glucose reabsorption. Live imaging of GLUT2 enabled us to avoid the artefactual localization of GLUT2 in fixed cells and to confirm the apical GLUT2 model. Live cell imaging showed a rapid 15 ± 3 min PKC-dependent basal-to-apical translocation of GLUT2 in response to glucose stimulation and a fourfold slower basolateral translocation under starvation. These results mark the physiological importance of responding quickly to rising glucose levels. Importantly, we show that phloretin, an apple polyphenol, inhibits GLUT2 translocation in both directions, suggesting that it exerts its effect by PKC inhibition. Subcellular localization studies demonstrated that GLUT2 is endocytosed through a caveolae-dependent mechanism, and that it is at least partly recovered in Rab11A-positive recycling endosome. Our work illuminates GLUT2 dynamics, providing a platform for drug development for diabetes and hyperglycaemia.
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Affiliation(s)
- Merav Cohen
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel Alexander Grass Center for Bioengineering, Benin School of Computer Science and Engineering, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Daniel Kitsberg
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel Alexander Grass Center for Bioengineering, Benin School of Computer Science and Engineering, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Sabina Tsytkin
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Maria Shulman
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel Alexander Grass Center for Bioengineering, Benin School of Computer Science and Engineering, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Benjamin Aroeti
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yaakov Nahmias
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel Alexander Grass Center for Bioengineering, Benin School of Computer Science and Engineering, Hebrew University of Jerusalem, Jerusalem, Israel
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78
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Gitrowski C, Al-Jubory AR, Handy RD. Uptake of different crystal structures of TiO2 nanoparticles by Caco-2 intestinal cells. Toxicol Lett 2014; 226:264-76. [DOI: 10.1016/j.toxlet.2014.02.014] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 02/12/2014] [Accepted: 02/17/2014] [Indexed: 12/29/2022]
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79
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Foret L. Shape and energy of a membrane bud induced by protein coats or viral protein assembly. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2014; 37:42. [PMID: 24859281 DOI: 10.1140/epje/i2014-14042-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/26/2014] [Accepted: 04/28/2014] [Indexed: 06/03/2023]
Abstract
Intracellular transport vesicles and enveloped virus production is mediated by the polymerization of proteins that form bi-dimensional curved and rigid structures, or "coats", on a membrane. Using the classical framework of fluid membrane elasticity, we compute numerically the shape and the mechanical energy of the membrane deformation induced by a coat at different stage of growth. We furthermore derive analytical approximate expressions for the membrane shape and energy. They are found to be very accurate when compared to numerical calculations. These analytical expressions should be useful when building a relevant model of coat polymerization kinetics. We also discuss some consequences of the membrane energy features on the coat assembly process, showing that at high tension a kinetically arrested state of incomplete assembly could exist.
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Affiliation(s)
- Lionel Foret
- Laboratoire de Physique Statistique, Ecole Normale Supérieure, Université Pierre et Marie Curie, CNRS, 24 rue Lhomond, 75005, Paris, France,
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80
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Kirchhausen T, Owen D, Harrison SC. Molecular structure, function, and dynamics of clathrin-mediated membrane traffic. Cold Spring Harb Perspect Biol 2014; 6:a016725. [PMID: 24789820 DOI: 10.1101/cshperspect.a016725] [Citation(s) in RCA: 317] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Clathrin is a molecular scaffold for vesicular uptake of cargo at the plasma membrane, where its assembly into cage-like lattices underlies the clathrin-coated pits of classical endocytosis. This review describes the structures of clathrin, major cargo adaptors, and other proteins that participate in forming a clathrin-coated pit, loading its contents, pinching off the membrane as a lattice-enclosed vesicle, and recycling the components. It integrates as much of the structural information as possible at the time of writing into a sketch of the principal steps in coated-pit and coated-vesicle formation.
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Affiliation(s)
- Tom Kirchhausen
- Department of Cell Biology, Harvard Medical School/PCMM, Boston, Massachusetts 02115
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81
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Liang L, Shen H, De Camilli P, Duncan JS. A novel multiple hypothesis based particle tracking method for clathrin mediated endocytosis analysis using fluorescence microscopy. IEEE TRANSACTIONS ON IMAGE PROCESSING : A PUBLICATION OF THE IEEE SIGNAL PROCESSING SOCIETY 2014; 23:1844-57. [PMID: 24808351 PMCID: PMC4373089 DOI: 10.1109/tip.2014.2303633] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In order to quantitatively analyze biological images and study underlying mechanisms of the cellular and subcellular processes, it is often required to track a large number of particles involved in these processes. Manual tracking can be performed by the biologists, but the workload is very heavy. In this paper, we present an automatic particle tracking method for analyzing an essential subcellular process, namely clathrin mediated endocytosis. The framework of the tracking method is an extension of the classical multiple hypothesis tracking (MHT), and it is designed to manage trajectories, solve data association problems, and handle pseudo-splitting/merging events. In the extended MHT framework, particle tracking becomes evaluating two types of hypotheses. The first one is the trajectory-related hypothesis, to test whether a recovered trajectory is correct, and the second one is the observation-related hypothesis, to test whether an observation from an image belongs to a real particle. Here, an observation refers to a detected particle and its feature vector. To detect the particles in 2D fluorescence images taken using total internal reflection microscopy, the images are segmented into regions, and the features of the particles are obtained by fitting Gaussian mixture models into each of the image regions. Specific models are developed according to the properties of the particles. The proposed tracking method is demonstrated on synthetic data under different scenarios and applied to real data.
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Affiliation(s)
- Liang Liang
- Department of Electrical Engineering, Yale University, New Haven, CT 06511 USA
| | - Hongying Shen
- Department of Cell Biology, Yale University, New Haven, CT 06511 USA
| | - Pietro De Camilli
- Department of Cell Biology, Yale University, New Haven, CT 06511 USA
| | - James S. Duncan
- Department of Electrical Engineering, Biomedical Engineering and Diagnostic Radiology, Yale University, New Haven, CT 06511 USA
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82
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Cordella N, Lampo TJ, Mehraeen S, Spakowitz AJ. Membrane fluctuations destabilize clathrin protein lattice order. Biophys J 2014; 106:1476-88. [PMID: 24703309 PMCID: PMC3976529 DOI: 10.1016/j.bpj.2013.11.4505] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 11/15/2013] [Accepted: 11/19/2013] [Indexed: 10/25/2022] Open
Abstract
We develop a theoretical model of a clathrin protein lattice on a flexible cell membrane. The clathrin subunit is modeled as a three-legged pinwheel with elastic deformation modes and intersubunit binding interactions. The pinwheels are constrained to lie on the surface of an elastic sheet that opposes bending deformation and is subjected to tension. Through Monte Carlo simulations, we predict the equilibrium phase behavior of clathrin lattices at various levels of tension. High membrane tensions, which correspond to suppressed membrane fluctuations, tend to stabilize large, flat crystalline structures similar to plaques that have been observed in vivo on cell membranes that are adhered to rigid surfaces. Low tensions, on the other hand, give rise to disordered, defect-ridden lattices that behave in a fluidlike manner. The principles of two-dimensional melting theory are applied to our model system to further clarify how high tensions can stabilize crystalline order on flexible membranes. These results demonstrate the importance of environmental physical cues in dictating the collective behavior of self-assembled protein structures.
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Affiliation(s)
- Nicholas Cordella
- Chemical Engineering, Stanford University, Stanford, California; Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California
| | - Thomas J Lampo
- Chemical Engineering, Stanford University, Stanford, California
| | | | - Andrew J Spakowitz
- Chemical Engineering, Stanford University, Stanford, California; Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California; Biophysics Program, Stanford University, Stanford, California.
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83
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Kalli AC, Morgan G, Sansom MSP. Interactions of the auxilin-1 PTEN-like domain with model membranes result in nanoclustering of phosphatidyl inositol phosphates. Biophys J 2014; 105:137-45. [PMID: 23823232 DOI: 10.1016/j.bpj.2013.05.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 11/18/2022] Open
Abstract
Auxilin-1 is a neuron-specific membrane-binding protein involved in a late stage of clathrin-mediated endocytosis. It recruits Hsc70, thus initiating uncoating of the clathrin-coated vesicles. Interactions of auxilin-1 with the vesicle membrane are crucial for this function and are mediated via an N-terminal PTEN-like domain. We have used multiscale molecular dynamics simulations to probe the interactions of the auxilin-1 PTEN-like domain with lipid bilayers containing differing phospholipid composition, including bilayers containing phosphatidyl inositol phosphates. Our results suggest a novel, to our knowledge, model for the auxilin/membrane encounter and subsequent interactions. Negatively charged lipids (especially PIP2) enhance binding of auxilin to lipid bilayers and facilitate its correct orientation relative to the membrane. Mutations in three basic residues (R301E/R307E/K311E) of the C2 subdomain of the PTEN-like domain perturbed its interaction with the bilayer, changing its orientation. The interaction of membrane-bound auxilin-1 PTEN-like domain with negatively charged lipid headgroups results in nanoclustering of PIP2 molecules in the adjacent bilayer leaflet.
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Affiliation(s)
- Antreas C Kalli
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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84
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Grossier JP, Xouri G, Goud B, Schauer K. Cell adhesion defines the topology of endocytosis and signaling. EMBO J 2013; 33:35-45. [PMID: 24366944 DOI: 10.1002/embj.201385284] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Preferred sites of endocytosis have been observed in various cell types, but whether they occur randomly or are linked to cellular cues is debated. Here, we quantified the sites of endocytosis of transferrin (Tfn) and epidermal growth factor (EGF) in cells whose adhesion geometry was defined by micropatterns. 3D probabilistic density maps revealed that Tfn was enriched in adhesive sites during uptake, whereas EGF endocytosis was restricted to the dorsal cellular surface. This spatial separation was not due to distributions of corresponding receptors but was regulated by uptake mechanisms. Asymmetric uptake of Tfn resulted from the enrichment of clathrin and adaptor protein 2 at adhesive areas. Asymmetry in EGF uptake was strongly dependent on the actin cytoskeleton and led to asymmetry in EGF receptor activation. Mild alteration of actin dynamics abolished asymmetry in EGF uptake and decreased EGF-induced downstream signaling, suggesting that cellular adhesion cues influence signal propagation. We propose that restriction of endocytosis at distinct sites allows cells to sense their environment in an "outside-in" mechanism.
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Affiliation(s)
- Jean-Philippe Grossier
- Molecular Mechanisms of Intracellular Transport, Unité Mixte de Recherche 144 Centre National de la Recherche Scientifique Institut Curie, Paris, France
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85
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Quantifying the dynamic interactions between a clathrin-coated pit and cargo molecules. Proc Natl Acad Sci U S A 2013; 110:E4591-600. [PMID: 24218552 DOI: 10.1073/pnas.1315202110] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clathrin-mediated endocytosis takes place through the recruitment of cargo molecules into a growing clathrin-coated pit (CCP). Despite the importance of this process to all mammalian cells, little is yet known about the interaction dynamics between cargo and CCPs. These interactions are difficult to study because CCPs display a large degree of lifetime heterogeneity and the interactions with cargo molecules are time dependent. We use single-molecule total internal reflection fluorescence microscopy, in combination with automatic detection and tracking algorithms, to directly visualize the recruitment of individual voltage-gated potassium channels into forming CCPs in living cells. We observe association and dissociation of individual channels with a CCP and, occasionally, their internalization. Contrary to widespread ideas, cargo often escapes from a pit before abortive CCP termination or endocytic vesicle production. Thus, the binding times of cargo molecules associating to CCPs are much shorter than the overall endocytic process. By measuring tens of thousands of capturing events, we build the distribution of capture times and the times that cargo remains confined to a CCP. An analytical stochastic model is developed and compared with the measured distributions. Due to the dynamic nature of the pit, the model is non-Markovian and it displays long-tail power law statistics. The measured distributions and model predictions are in excellent agreement over more than five orders of magnitude. Our findings identify one source of the large heterogeneities in CCP dynamics and provide a mechanism for the anomalous diffusion of proteins in the plasma membrane.
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86
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Han HM, Bouchet-Marquis C, Huebinger J, Grabenbauer M. Golgi apparatus analyzed by cryo-electron microscopy. Histochem Cell Biol 2013; 140:369-81. [PMID: 23954988 PMCID: PMC3787787 DOI: 10.1007/s00418-013-1136-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/03/2013] [Indexed: 11/28/2022]
Abstract
In 1898, the Golgi apparatus was discovered by light microscopy, and since the 1950s, the ultrastructure composition is known by electron microscopic investigation. The complex three-dimensional morphology fascinated researchers and was sometimes even the driving force to develop novel visualization techniques. However, the highly dynamic membrane systems of Golgi apparatus are delicate and prone to fixation artifacts. Therefore, the understanding of Golgi morphology and its function has been improved significantly with the development of better preparation methods. Nowadays, cryo-fixation is the method of choice to arrest instantly all dynamic and physiological processes inside cells, tissues, and small organisms. Embedded in amorphous ice, such samples can be further processed by freeze substitution or directly analyzed in their fully hydrated state by cryo-electron microscopy and tomography. Even though the overall morphology of vitrified Golgi stacks is comparable to well-prepared and resin-embedded samples, previously unknown structural details can be observed solely based on their native density. At this point, any further improvement of sample preparation would gain novel insights, perhaps not in terms of general morphology, but on fine structural details of this dynamic organelle.
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Affiliation(s)
- Hong-Mei Han
- Department of Systemic Cell Biology, Max-Planck-Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Cedric Bouchet-Marquis
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder, CO USA
- FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, OR 97124 USA
| | - Jan Huebinger
- Department of Systemic Cell Biology, Max-Planck-Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Markus Grabenbauer
- Institute of Anatomy and Cell Biology, Heidelberg University, INF 307, 69120 Heidelberg, Germany
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87
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James NG, Digman MA, Ross JA, Barylko B, Wang L, Li J, Chen Y, Mueller JD, Gratton E, Albanesi JP, Jameson DM. A mutation associated with centronuclear myopathy enhances the size and stability of dynamin 2 complexes in cells. Biochim Biophys Acta Gen Subj 2013; 1840:315-21. [PMID: 24016602 DOI: 10.1016/j.bbagen.2013.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/31/2013] [Accepted: 09/03/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Dynamin 2 (Dyn2) is a ~100kDa GTPase that assembles around the necks of nascent endocytic and Golgi vesicles and catalyzes membrane scission. Mutations in Dyn2 that cause centronuclear myopathy (CNM) have been shown to stabilize Dyn2 polymers against GTP-dependent disassembly in vitro. Precisely timed regulation of assembly and disassembly is believed to be critical for Dyn2 function in membrane vesiculation, and the CNM mutations interfere with this regulation by shifting the equilibrium toward the assembled state. METHODS In this study we use two fluorescence fluctuation spectroscopy (FFS) approaches to show that a CNM mutant form of Dyn2 also has a greater propensity to self-assemble in the cytosol and on the plasma membrane of living cells. RESULTS Results obtained using brightness analysis indicate that unassembled wild-type Dyn2 is predominantly tetrameric in the cytosol, although different oligomeric species are observed, depending on the concentration of expressed protein. In contrast, an R369W mutant identified in CNM patients forms higher-order oligomers at concentrations above 1μM. Investigation of Dyn2-R369W by Total Internal Reflection Fluorescence (TIRF) FFS reveals that this mutant forms larger and more stable clathrin-containing structures on the plasma membrane than wild-type Dyn2. CONCLUSIONS AND GENERAL SIGNIFICANCE These observations may explain defects in membrane trafficking reported in CNM patient cells and in heterologous systems expressing CNM-associated Dyn2 mutants.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, HI 96813, USA
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88
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Watanabe S, Liu Q, Davis MW, Hollopeter G, Thomas N, Jorgensen NB, Jorgensen EM. Ultrafast endocytosis at Caenorhabditis elegans neuromuscular junctions. eLife 2013; 2:e00723. [PMID: 24015355 PMCID: PMC3762212 DOI: 10.7554/elife.00723] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 07/12/2013] [Indexed: 11/13/2022] Open
Abstract
Synaptic vesicles can be released at extremely high rates, which places an extraordinary demand on the recycling machinery. Previous ultrastructural studies of vesicle recycling were conducted in dissected preparations using an intense stimulation to maximize the probability of release. Here, a single light stimulus was applied to motor neurons in intact Caenorhabditis elegans nematodes expressing channelrhodopsin, and the animals rapidly frozen. We found that docked vesicles fuse along a broad active zone in response to a single stimulus, and are replenished with a time constant of about 2 s. Endocytosis occurs within 50 ms adjacent to the dense projection and after 1 s adjacent to adherens junctions. These studies suggest that synaptic vesicle endocytosis may occur on a millisecond time scale following a single physiological stimulus in the intact nervous system and is unlikely to conform to current models of endocytosis. DOI:http://dx.doi.org/10.7554/eLife.00723.001.
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Affiliation(s)
- Shigeki Watanabe
- Department of Biology , Howard Hughes Medical Institute, University of Utah , Salt Lake City , United States
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89
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Abstract
Clathrin-mediated endocytosis (CME) is conserved among eukaryotes and has been extensively analyzed at a molecular level. Here, we present an analysis of CME in the human fungal pathogen Candida albicans that shows the same modular structure as those in other fungi and mammalian cells. Intriguingly, C. albicans is perfectly viable in the absence of Arp2/3, an essential component of CME in other systems. In C. albicans, Arp2/3 function remains essential for CME as all 15 proteins tested that participate in CME, including clathrin, lose their characteristic dynamics observed in wild-type (WT) cells. However, since arp2/3 cells are still able to endocytose lipids and fluid-phase markers, but not the Ste2 and Mup1 plasma membrane proteins, there must be an alternate clathrin-independent pathway we term Arp2/3-independent endocytosis (AIE). Characterization of AIE shows that endocytosis in arp2 mutants relies on actin cables and other Arp2/3-independent actin structures, as inhibition of actin functions prevented cargo uptake in arp2/3 mutants. Transmission electron microscopy (TEM) showed that arp2/3 mutants still formed invaginating tubules, cell structures whose proper functions are believed to heavily rely on Arp2/3. Finally, Prk1 and Sjl2, two proteins involved in patch disassembly during CME, were not correctly localized to sites of endocytosis in arp2 mutants, implying a role of Arp2/3 in CME patch disassembly. Overall, C. albicans contains an alternative endocytic pathway (AIE) that relies on actin cable function to permit clathrin-independent endocytosis (CIE) and provides a system to further explore alternate endocytic routes that likely exist in fungal species. There is a well-established process of endocytosis that is generally used by eukaryotic cells termed clathrin-mediated endocytosis (CME). Although the details are somewhat different between lower and higher eukaryotes, CME appears to be the dominant endocytic process in all eukaryotes. While fungi such as Saccharomyces cerevisiae have proven excellent models for dissecting the molecular details of endocytosis, loss of CME is so detrimental that it has been difficult to study alternate pathways functioning in its absence. Although the fungal pathogen Candida albicans has a CME pathway that functions similarly to that of S. cerevisiae, inactivation of this pathway does not compromise growth of yeast-form C. albicans. In these cells, lipids and fluid-phase molecules are still endocytosed in an actin-dependent manner, but membrane proteins are not. Thus, C. albicans provides a powerful model for the analysis of CME-independent endocytosis in lower eukaryotes.
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90
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Yamaoka S, Shimono Y, Shirakawa M, Fukao Y, Kawase T, Hatsugai N, Tamura K, Shimada T, Hara-Nishimura I. Identification and dynamics of Arabidopsis adaptor protein-2 complex and its involvement in floral organ development. THE PLANT CELL 2013; 25:2958-69. [PMID: 23975897 PMCID: PMC3784591 DOI: 10.1105/tpc.113.114082] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 07/16/2013] [Accepted: 08/06/2013] [Indexed: 05/18/2023]
Abstract
The adaptor protein-2 (AP-2) complex is a heterotetramer involved in clathrin-mediated endocytosis of cargo proteins from the plasma membrane in animal cells. The homologous genes of AP-2 subunits are present in the genomes of plants; however, their identities and roles in endocytic pathways are not clearly defined in plants. Here, we reveal the molecular composition of the AP-2 complex of Arabidopsis thaliana and its dynamics on the plasma membrane. We identified all of the α-, β-, σ-, and μ-subunits of the AP-2 complex and detected a weak interaction of the AP-2 complex with clathrin heavy chain. The μ-subunit protein fused to green fluorescent protein (AP2M-GFP) was localized to the plasma membrane and to the cytoplasm. Live-cell imaging using a variable-angle epifluorescence microscope revealed that AP2M-GFP transiently forms punctate structures on the plasma membrane. Homozygous ap2m mutant plants exhibited abnormal floral structures, including reduced stamen elongation and delayed anther dehiscence, which led to a failure of pollination and a subsequent reduction of fertility. Our study provides a molecular basis for understanding AP-2-dependent endocytic pathways in plants and their roles in floral organ development and plant reproduction.
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Affiliation(s)
- Shohei Yamaoka
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yuki Shimono
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Makoto Shirakawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Yoichiro Fukao
- Plant Global Educational Project, Nara Institute of Science and Technology, Ikoma 630-0192, Japan
| | - Takashi Kawase
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Noriyuki Hatsugai
- Research Center for Cooperative Projects, Hokkaido University, Sapporo 060-8638, Japan
| | - Kentaro Tamura
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Tomoo Shimada
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Ikuko Hara-Nishimura
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Address correspondence to
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91
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Zeng MH, Liu SH, Yang MX, Zhang YJ, Liang JY, Wan XR, Liang H. Characterization of a gene encoding clathrin heavy chain in maize up-regulated by salicylic acid, abscisic acid and high boron supply. Int J Mol Sci 2013; 14:15179-98. [PMID: 23880865 PMCID: PMC3742294 DOI: 10.3390/ijms140715179] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 07/01/2013] [Accepted: 07/16/2013] [Indexed: 02/06/2023] Open
Abstract
Clathrin, a three-legged triskelion composed of three clathrin heavy chains (CHCs) and three light chains (CLCs), plays a critical role in clathrin-mediated endocytosis (CME) in eukaryotic cells. In this study, the genes ZmCHC1 and ZmCHC2 encoding clathrin heavy chain in maize were cloned and characterized for the first time in monocots. ZmCHC1 encodes a 1693-amino acid-protein including 29 exons and 28 introns, and ZmCHC2 encodes a 1746-amino acid-protein including 28 exons and 27 introns. The high similarities of gene structure, protein sequences and 3D models among ZmCHC1, and Arabidopsis AtCHC1 and AtCHC2 suggest their similar functions in CME. ZmCHC1 gene is predominantly expressed in maize roots instead of ubiquitous expression of ZmCHC2. Consistent with a typical predicted salicylic acid (SA)-responsive element and four predicted ABA-responsive elements (ABREs) in the promoter sequence of ZmCHC1, the expression of ZmCHC1 instead of ZmCHC2 in maize roots is significantly up-regulated by SA or ABA, suggesting that ZmCHC1 gene may be involved in the SA signaling pathway in maize defense responses. The expressions of ZmCHC1 and ZmCHC2 genes in maize are down-regulated by azide or cold treatment, further revealing the energy requirement of CME and suggesting that CME in plants is sensitive to low temperatures.
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Affiliation(s)
| | | | | | | | | | - Xiao-Rong Wan
- Authors to whom correspondence should be addressed; E-Mails: (X.-R.W.); (H.L.); Tel./Fax: +86-20-8900-3168 (X.-R.W. & H.L.)
| | - Hong Liang
- Authors to whom correspondence should be addressed; E-Mails: (X.-R.W.); (H.L.); Tel./Fax: +86-20-8900-3168 (X.-R.W. & H.L.)
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92
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Boulant S, Stanifer M, Kural C, Cureton DK, Massol R, Nibert ML, Kirchhausen T. Similar uptake but different trafficking and escape routes of reovirus virions and infectious subvirion particles imaged in polarized Madin-Darby canine kidney cells. Mol Biol Cell 2013; 24:1196-207. [PMID: 23427267 PMCID: PMC3623640 DOI: 10.1091/mbc.e12-12-0852] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/07/2013] [Accepted: 02/11/2013] [Indexed: 12/27/2022] Open
Abstract
Polarized epithelial cells that line the digestive, respiratory, and genitourinary tracts form a barrier that many viruses must breach to infect their hosts. Current understanding of cell entry by mammalian reovirus (MRV) virions and infectious subvirion particles (ISVPs), generated from MRV virions by extracellular proteolysis in the digestive tract, are mostly derived from in vitro studies with nonpolarized cells. Recent live-cell imaging advances allow us for the first time to visualize events at the apical surface of polarized cells. In this study, we used spinning-disk confocal fluorescence microscopy with high temporal and spatial resolution to follow the uptake and trafficking dynamics of single MRV virions and ISVPs at the apical surface of live polarized Madin-Darby canine kidney cells. Both types of particles were internalized by clathrin-mediated endocytosis, but virions and ISVPs exhibited strikingly different trafficking after uptake. While virions reached early and late endosomes, ISVPs did not and instead escaped the endocytic pathway from an earlier location. This study highlights the broad advantages of using live-cell imaging combined with single-particle tracking for identifying key steps in cell entry by viruses.
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Affiliation(s)
- Steeve Boulant
- Department of Cell Biology, Harvard Medical School and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
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93
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Jin AJ, Lafer EM, Peng JQ, Smith PD, Nossal R. Unraveling protein-protein interactions in clathrin assemblies via atomic force spectroscopy. Methods 2013; 59:316-27. [PMID: 23270814 PMCID: PMC3608793 DOI: 10.1016/j.ymeth.2012.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 12/08/2012] [Accepted: 12/14/2012] [Indexed: 01/14/2023] Open
Abstract
Atomic force microscopy (AFM), single molecule force spectroscopy (SMFS), and single particle force spectroscopy (SPFS) are used to characterize intermolecular interactions and domain structures of clathrin triskelia and clathrin-coated vesicles (CCVs). The latter are involved in receptor-mediated endocytosis (RME) and other trafficking pathways. Here, we subject individual triskelia, bovine-brain CCVs, and reconstituted clathrin-AP180 coats to AFM-SMFS and AFM-SPFS pulling experiments and apply novel analytics to extract force-extension relations from very large data sets. The spectroscopic fingerprints of these samples differ markedly, providing important new information about the mechanism of CCV uncoating. For individual triskelia, SMFS reveals a series of events associated with heavy chain alpha-helix hairpin unfolding, as well as cooperative unraveling of several hairpin domains. SPFS of clathrin assemblies exposes weaker clathrin-clathrin interactions that are indicative of inter-leg association essential for RME and intracellular trafficking. Clathrin-AP180 coats are energetically easier to unravel than the coats of CCVs, with a non-trivial dependence on force-loading rate.
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Affiliation(s)
- Albert J Jin
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, DHHS, Bethesda, MD 20892, United States.
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Kim I, Pan W, Jones SA, Zhang Y, Zhuang X, Wu D. Clathrin and AP2 are required for PtdIns(4,5)P2-mediated formation of LRP6 signalosomes. ACTA ACUST UNITED AC 2013; 200:419-28. [PMID: 23400998 PMCID: PMC3575536 DOI: 10.1083/jcb.201206096] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
PtdIns(4,5)P2 promotes the assembly of LRP6 signalosomes at the cell surface via the recruitment of AP2 and clathrin. Canonical Wnt signaling is initiated by the binding of Wnt proteins to their receptors, low-density lipoprotein-related protein 5 and 6 (LRP5/6) and frizzled proteins, leading to phosphatidylinositol (4,5)bisphosphate (PtdIns(4,5)P2) production, signalosome formation, and LRP phosphorylation. However, the mechanism by which PtdIns(4,5)P2 regulates the signalosome formation remains unclear. Here we show that clathrin and adaptor protein 2 (AP2) were part of the LRP6 signalosomes. The presence of clathrin and AP2 in the LRP6 signalosomes depended on PtdIns(4,5)P2, and both clathrin and AP2 were required for the formation of LRP6 signalosomes. In addition, WNT3A-induced LRP6 signalosomes were primarily localized at cell surfaces, and WNT3A did not induce marked LRP6 internalization. However, rapid PtdIns(4,5)P2 hydrolysis induced artificially after WNT3A stimulation could lead to marked LRP6 internalization. Moreover, we observed WNT3A-induced LRP6 and clathrin clustering at cell surfaces using super-resolution fluorescence microscopy. Therefore, we conclude that PtdIns(4,5)P2 promotes the assembly of LRP6 signalosomes via the recruitment of AP2 and clathrin and that LRP6 internalization may not be a prerequisite for Wnt signaling to β-catenin stabilization.
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Affiliation(s)
- Ingyu Kim
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA
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95
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Adung'a VO, Gadelha C, Field MC. Proteomic analysis of clathrin interactions in trypanosomes reveals dynamic evolution of endocytosis. Traffic 2013; 14:440-57. [PMID: 23305527 DOI: 10.1111/tra.12040] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 01/07/2013] [Accepted: 01/10/2012] [Indexed: 01/09/2023]
Abstract
Endocytosis is a vital cellular process maintaining the cell surface, modulating signal transduction and facilitating nutrient acquisition. In metazoa, multiple endocytic modes are recognized, but for many unicellular organisms the process is likely dominated by the ancient clathrin-mediated pathway. The endocytic system of the highly divergent trypanosomatid Trypanosoma brucei exhibits many unusual features, including a restricted site of internalization, dominance of the plasma membrane by GPI-anchored proteins, absence of the AP2 complex and an exceptionally high rate. Here we asked if the proteins subtending clathrin trafficking in trypanosomes are exclusively related to those of higher eukaryotes or if novel, potentially taxon-specific proteins operate. Co-immunoprecipitation identified twelve T. brucei clathrin-associating proteins (TbCAPs), which partially colocalized with clathrin. Critically, eight TbCAPs are restricted to trypanosomatid genomes and all of these are required for robust cell proliferation. A subset, TbCAP100, TbCAP116, TbCAP161 and TbCAP334, were implicated in distinct endocytic steps by detailed analysis of knockdown cells. Coupled with the absence of orthologs for many metazoan and fungal endocytic factors, these data suggest that clathrin interactions in trypanosomes are highly lineage-specific, and indicate substantial evolutionary diversity within clathrin-mediated endocytosis mechanisms across the eukaryotes.
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Affiliation(s)
- Vincent O Adung'a
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK
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96
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Levayer R. [Regulation of intercellular adhesion during epithelial morphogenesis]. Biol Aujourdhui 2012; 206:219-36. [PMID: 23171844 DOI: 10.1051/jbio/2012021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Indexed: 11/14/2022]
Abstract
The epithelium is one of the most abundant tissues in metazoans. It is required to generate stable chemical and mechanical barriers between physiological compartments (fluid matrix/external environment). This function is based on multiple intercellular junctions, which insulate and stabilize cell-cell contacts in the tissue. Despite this apparent robustness, epithelia can be extensively remodeled during wound healing, embryogenesis and tumor progression. The capacity to be remodeled while keeping tissue cohesion requires a perfect balance between stability and plasticity of intercellular junctions. The balance is partially regulated by intercellular adhesion, which is mostly based on adherens junctions and the transmembrane protein E-cadherin. The aim of this review is to report the molecular basis of the balance between plasticity and robustness in the epithelium. We will first present the minimal physical framework used to describe epithelial cell shape. We will then describe the main processes involved in intercellular adhesion regulation and their functions during epithelial morphogenesis. Eventually, we will analyze the relationship and the coupling between adhesive forces and cortical tension.
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Affiliation(s)
- Romain Levayer
- Institut de Biologie du Developpement de Marseille Luminy, Marseille, France.
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97
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Plasma membrane reshaping during endocytosis is revealed by time-resolved electron tomography. Cell 2012; 150:508-20. [PMID: 22863005 DOI: 10.1016/j.cell.2012.05.046] [Citation(s) in RCA: 247] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 04/04/2012] [Accepted: 05/17/2012] [Indexed: 12/22/2022]
Abstract
Endocytosis, like many dynamic cellular processes, requires precise temporal and spatial orchestration of complex protein machinery to mediate membrane budding. To understand how this machinery works, we directly correlated fluorescence microscopy of key protein pairs with electron tomography. We systematically located 211 endocytic intermediates, assigned each to a specific time window in endocytosis, and reconstructed their ultrastructure in 3D. The resulting virtual ultrastructural movie defines the protein-mediated membrane shape changes during endocytosis in budding yeast. It reveals that clathrin is recruited to flat membranes and does not initiate curvature. Instead, membrane invagination begins upon actin network assembly followed by amphiphysin binding to parallel membrane segments, which promotes elongation of the invagination into a tubule. Scission occurs on average 9 s after initial bending when invaginations are ∼100 nm deep, releasing nonspherical vesicles with 6,400 nm2 mean surface area. Direct correlation of protein dynamics with ultrastructure provides a quantitative 4D resource.
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98
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Cocucci E, Aguet F, Boulant S, Kirchhausen T. The first five seconds in the life of a clathrin-coated pit. Cell 2012; 150:495-507. [PMID: 22863004 DOI: 10.1016/j.cell.2012.05.047] [Citation(s) in RCA: 279] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 01/12/2012] [Accepted: 05/31/2012] [Indexed: 10/28/2022]
Abstract
Coated pits assemble by growth of a clathrin lattice, which is linked by adaptors to the underlying membrane. How does this process start? We used live-cell TIRF imaging with single-molecule EGFP sensitivity and high temporal resolution to detect arrival of the clathrin triskelions and AP2 adaptors that initiate coat assembly. Unbiased object identification and trajectory tracking, together with a statistical model, yield the arrival times and numbers of individual proteins, as well as experimentally confirmed estimates of the extent of substitution of endogenous by expressed, fluorescently tagged proteins. Pits initiate by coordinated arrival of clathrin and AP2, which is usually detected as two sequential steps, each of one triskelion with two adaptors. PI-4,5-P2 is essential for initiation. The accessory proteins FCHo1/2 are not; instead, they are required for sustained growth. This objective picture of coated pit initiation also shows that methods outlined here will be broadly useful for studies of dynamic assemblies in living cells.
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Affiliation(s)
- Emanuele Cocucci
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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99
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Henry A, Hislop J, Grove J, Thorn K, Marsh M, von Zastrow M. Regulation of endocytic clathrin dynamics by cargo ubiquitination. Dev Cell 2012; 23:519-32. [PMID: 22940114 PMCID: PMC3470869 DOI: 10.1016/j.devcel.2012.08.003] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 06/21/2012] [Accepted: 08/04/2012] [Indexed: 12/21/2022]
Abstract
VIDEO ABSTRACT Some endocytic cargoes control clathrin-coated pit (CCP) maturation, but it is not known how such regulation is communicated. We found that μ-opioid neuropeptide receptors signal to their enclosing CCPs by ubiquitination. Nonubiquitinated receptors delay CCPs at an intermediate stage of maturation, after clathrin lattice assembly is complete but before membrane scission. Receptor ubiquitination relieves this inhibition, effectively triggering CCP scission and producing a receptor-containing endocytic vesicle. The ubiquitin modification that conveys this endocytosis-promoting signal is added to the receptor's first cytoplasmic loop, catalyzed by the Smurf2 ubiquitin ligase, and coordinated with activation-dependent receptor phosphorylation and clustering through Smurf2 recruitment by the endocytic adaptor beta-arrestin. Epsin1 detects the signal at the CCP and is required for ubiquitin-promoted scission. This cargo-to-coat communication system mediates a biochemical checkpoint that ensures appropriate receptor ubiquitination for later trafficking, and it controls specific receptor loading into CCPs by sensing when a sufficient quorum is reached.
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Affiliation(s)
- Anastasia G. Henry
- Program in Cell Biology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - James N. Hislop
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Joe Grove
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Kurt Thorn
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Mark Marsh
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Mark von Zastrow
- Program in Cell Biology, University of California, San Francisco, San Francisco, CA 94158, USA
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
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