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García-Arribas AB, Alonso A, Goñi FM. Cholesterol interactions with ceramide and sphingomyelin. Chem Phys Lipids 2016; 199:26-34. [PMID: 27132117 DOI: 10.1016/j.chemphyslip.2016.04.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/05/2016] [Accepted: 04/06/2016] [Indexed: 01/10/2023]
Abstract
Sphingolipids contain in their polar heads chemical groups allowing them to establish a complex network of H-bonds (through different OH and NHgroups) with other lipids in the bilayer. In the recent years the specific interaction of sphingomyelin (SM) with cholesterol (Chol) has been examined, largely in the context of the "lipid raft" hypothesis. Formation of SM-Ceramide (Cer) complexes, proposed to exist in cell membranes in response to stress, has also been described. More recently, a delicate balance of phase formation and transformation in ternary mixtures of SM, Chol and Cer, with mutual displacement of Chol and Cer from their interaction with SM is considered to exist. In addition, data demonstrating direct Chol-Cer interaction are becoming available.
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Affiliation(s)
- Aritz B García-Arribas
- Biofisika Institute (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, 48080 Bilbao, Spain
| | - Alicia Alonso
- Biofisika Institute (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, 48080 Bilbao, Spain
| | - Felix M Goñi
- Biofisika Institute (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, 48080 Bilbao, Spain.
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52
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Li H, Zhang Y, Ha V, Lykotrafitis G. Modeling of band-3 protein diffusion in the normal and defective red blood cell membrane. SOFT MATTER 2016; 12:3643-3653. [PMID: 26977476 DOI: 10.1039/c4sm02201g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We employ a two-component red blood cell (RBC) membrane model to simulate lateral diffusion of band-3 proteins in the normal RBC and in the RBC with defective membrane proteins. The defects reduce the connectivity between the lipid bilayer and the membrane skeleton (vertical connectivity), or the connectivity of the membrane skeleton itself (horizontal connectivity), and are associated with the blood disorders of hereditary spherocytosis (HS) and hereditary elliptocytosis (HE) respectively. Initially, we demonstrate that the cytoskeleton limits band-3 lateral mobility by measuring the band-3 macroscopic diffusion coefficients in the normal RBC membrane and in a lipid bilayer without the cytoskeleton. Then, we study band-3 diffusion in the defective RBC membrane and quantify the relation between band-3 diffusion coefficients and percentage of protein defects in HE RBCs. In addition, we illustrate that at low spectrin network connectivity (horizontal connectivity) band-3 subdiffusion can be approximated as anomalous diffusion, while at high horizontal connectivity band-3 diffusion is characterized as confined diffusion. Our simulations show that the band-3 anomalous diffusion exponent depends on the percentage of protein defects in the membrane cytoskeleton. We also confirm that the introduction of attraction between the lipid bilayer and the spectrin network reduces band-3 diffusion, but we show that this reduction is lower than predicted by the percolation theory. Furthermore, we predict that the attractive force between the spectrin filament and the lipid bilayer is at least 20 times smaller than the binding forces at band-3 and glycophorin C, the two major membrane binding sites. Finally, we explore diffusion of band-3 particles in the RBC membrane with defects related to vertical connectivity. We demonstrate that in this case band-3 diffusion can be approximated as confined diffusion for all attraction levels between the spectrin network and the lipid bilayer. By comparing the diffusion coefficients measured in horizontal vs. vertical defects, we conclude that band-3 mobility is primarily controlled by the horizontal connectivity.
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Affiliation(s)
- He Li
- Division of Applied Mathematics, Brown University, Providence, RI 02912, USA
| | - Yihao Zhang
- Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, Unit 3139, Storrs, CT 06269-3139, USA.
| | - Vi Ha
- Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, Unit 3139, Storrs, CT 06269-3139, USA.
| | - George Lykotrafitis
- Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, Unit 3139, Storrs, CT 06269-3139, USA. and Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
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53
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Carquin M, D'Auria L, Pollet H, Bongarzone ER, Tyteca D. Recent progress on lipid lateral heterogeneity in plasma membranes: From rafts to submicrometric domains. Prog Lipid Res 2015; 62:1-24. [PMID: 26738447 DOI: 10.1016/j.plipres.2015.12.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/22/2015] [Accepted: 12/22/2015] [Indexed: 12/29/2022]
Abstract
The concept of transient nanometric domains known as lipid rafts has brought interest to reassess the validity of the Singer-Nicolson model of a fluid bilayer for cell membranes. However, this new view is still insufficient to explain the cellular control of surface lipid diversity or membrane deformability. During the past decades, the hypothesis that some lipids form large (submicrometric/mesoscale vs nanometric rafts) and stable (>min vs s) membrane domains has emerged, largely based on indirect methods. Morphological evidence for stable submicrometric lipid domains, well-accepted for artificial and highly specialized biological membranes, was further reported for a variety of living cells from prokaryot es to yeast and mammalian cells. However, results remained questioned based on limitations of available fluorescent tools, use of poor lipid fixatives, and imaging artifacts due to non-resolved membrane projections. In this review, we will discuss recent evidence generated using powerful and innovative approaches such as lipid-specific toxin fragments that support the existence of submicrometric domains. We will integrate documented mechanisms involved in the formation and maintenance of these domains, and provide a perspective on their relevance on membrane deformability and regulation of membrane protein distribution.
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Affiliation(s)
- Mélanie Carquin
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ludovic D'Auria
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Hélène Pollet
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ernesto R Bongarzone
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Donatienne Tyteca
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium.
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54
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Caetano FA, Dirk BS, Tam JHK, Cavanagh PC, Goiko M, Ferguson SSG, Pasternak SH, Dikeakos JD, de Bruyn JR, Heit B. MIiSR: Molecular Interactions in Super-Resolution Imaging Enables the Analysis of Protein Interactions, Dynamics and Formation of Multi-protein Structures. PLoS Comput Biol 2015; 11:e1004634. [PMID: 26657340 PMCID: PMC4676698 DOI: 10.1371/journal.pcbi.1004634] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/27/2015] [Indexed: 11/18/2022] Open
Abstract
Our current understanding of the molecular mechanisms which regulate cellular processes such as vesicular trafficking has been enabled by conventional biochemical and microscopy techniques. However, these methods often obscure the heterogeneity of the cellular environment, thus precluding a quantitative assessment of the molecular interactions regulating these processes. Herein, we present Molecular Interactions in Super Resolution (MIiSR) software which provides quantitative analysis tools for use with super-resolution images. MIiSR combines multiple tools for analyzing intermolecular interactions, molecular clustering and image segmentation. These tools enable quantification, in the native environment of the cell, of molecular interactions and the formation of higher-order molecular complexes. The capabilities and limitations of these analytical tools are demonstrated using both modeled data and examples derived from the vesicular trafficking system, thereby providing an established and validated experimental workflow capable of quantitatively assessing molecular interactions and molecular complex formation within the heterogeneous environment of the cell. In this paper we present the software package Molecular Interactions in Super Resolution (MIiSR), which provides a series of quantitative analytical tools for measuring molecular interactions and the formation of higher-order molecular complexes in super-resolution microscopy images.
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Affiliation(s)
- Fabiana A. Caetano
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Brennan S. Dirk
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - Joshua H. K. Tam
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - P. Craig Cavanagh
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - Maria Goiko
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada
| | | | - Stephen H. Pasternak
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
- Department of Clinical Neurological Sciences, Schulich School of Medicine, The University of Western Ontario, London, Ontario, Canada
| | - Jimmy D. Dikeakos
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - John R. de Bruyn
- Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada
| | - Bryan Heit
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- * E-mail:
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55
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Płóciennikowska A, Zdioruk MI, Traczyk G, Świątkowska A, Kwiatkowska K. LPS-induced clustering of CD14 triggers generation of PI(4,5)P2. J Cell Sci 2015; 128:4096-111. [PMID: 26446256 DOI: 10.1242/jcs.173104] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 09/30/2015] [Indexed: 01/08/2023] Open
Abstract
Bacterial lipopolysaccharide (LPS) induces strong pro-inflammatory reactions after sequential binding to CD14 protein and TLR4 receptor. Here, we show that CD14 controls generation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] in response to LPS binding. In J774 cells and HEK293 cells expressing CD14 exposed to 10-100 ng/ml LPS, the level of PI(4,5)P2 rose in a biphasic manner with peaks at 5-10 min and 60 min. After 5-10 min of LPS stimulation, CD14 underwent prominent clustering in the plasma membrane, accompanied by accumulation of PI(4,5)P2 and type-I phosphatidylinositol 4-phosphate 5-kinase (PIP5K) isoforms Iα and Iγ (encoded by Pip5k1a and Pip5k1c, respectively) in the CD14 region. Clustering of CD14 with antibodies, without LPS and TLR4 participation, was sufficient to trigger PI(4,5)P2 elevation. The newly generated PI(4,5)P2 accumulated in rafts, which also accommodated CD14 and a large portion of PIP5K Iα and PIP5K Iγ. Silencing of PIP5K Iα and PIP5K Iγ, or application of drugs interfering with PI(4,5)P2 synthesis and availability, abolished the LPS-induced PI(4,5)P2 elevation and inhibited downstream pro-inflammatory reactions. Taken together, these data indicate that LPS induces clustering of CD14, which triggers PI(4,5)P2 generation in rafts that is required for maximal pro-inflammatory signaling of TLR4.
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Affiliation(s)
- Agnieszka Płóciennikowska
- Nencki Institute of Experimental Biology, Laboratory of Molecular Membrane Biology, 3 Pasteur St., Warsaw 02-093, Poland
| | - Mykola I Zdioruk
- Nencki Institute of Experimental Biology, Laboratory of Molecular Membrane Biology, 3 Pasteur St., Warsaw 02-093, Poland
| | - Gabriela Traczyk
- Nencki Institute of Experimental Biology, Laboratory of Molecular Membrane Biology, 3 Pasteur St., Warsaw 02-093, Poland
| | - Anna Świątkowska
- Nencki Institute of Experimental Biology, Laboratory of Molecular Membrane Biology, 3 Pasteur St., Warsaw 02-093, Poland
| | - Katarzyna Kwiatkowska
- Nencki Institute of Experimental Biology, Laboratory of Molecular Membrane Biology, 3 Pasteur St., Warsaw 02-093, Poland
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Bossa GV, Roth J, May S. Modeling Lipid-Lipid Correlations across a Bilayer Membrane Using the Quasi-chemical Approximation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9924-9932. [PMID: 26302019 DOI: 10.1021/acs.langmuir.5b01719] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mixed fluid-like lipid membranes exhibit interactions not only among the lipids within a given leaflet but also across the bilayer. The ensuing collective interleaflet coupling of entire membrane domains has been modeled previously using various mean-field approaches. Yet, also on the level of individual lipids have correlations across the bilayer been observed experimentally for binary mixtures of charged/uncharged lipids with mismatching combinations of short and long acyl chain lengths. The present study proposes a lattice gas model to quantify these correlations. To this end, we represent a macroscopically homogeneous lipid bilayer by two coupled two-dimensional lattice gases that we study using the quasi-chemical approximation. We demonstrate that the rationalization of previous experimental results is only possible if besides two-body lipid-lipid interactions within and across the bilayer our model also accounts for an additional multibody interaction mechanism, namely the local hydrophobic height mismatch created by pairing short and long chain lipids together. The robustness of the quasi-chemical approximation is verified by comparison with Monte Carlo simulations.
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Affiliation(s)
- Guilherme Volpe Bossa
- Department of Physics, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Joseph Roth
- Department of Physics, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Sylvio May
- Department of Physics, North Dakota State University , Fargo, North Dakota 58108-6050, United States
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57
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Jenkins PM, He M, Bennett V. Dynamic spectrin/ankyrin-G microdomains promote lateral membrane assembly by opposing endocytosis. SCIENCE ADVANCES 2015; 1:e1500301. [PMID: 26523289 PMCID: PMC4624203 DOI: 10.1126/sciadv.1500301] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Current physical models for plasma membranes emphasize dynamic 10- to 300-nm compartments at thermodynamic equilibrium but subject to thermal fluctuations. However, epithelial lateral membranes contain micrometer-sized domains defined by an underlying membrane skeleton composed of spectrin and its partner ankyrin-G. We demonstrate that these spectrin/ankyrin-G domains exhibit local microtubule-dependent movement on a time scale of minutes and encounter most of the lateral membranes within an hour. Spectrin/ankyrin-G domains exclude clathrin and clathrin-dependent cargo, and inhibit both receptor-mediated and bulk endocytosis. Moreover, inhibition of endocytosis fully restores lateral membrane height in spectrin- or ankyrin-G-depleted cells. These findings support a non-equilibrium cellular-scale model for epithelial lateral membranes, where spectrin/ankyrin-G domains actively patrol the plasma membrane, analogous to "window washers," and promote columnar morphology by blocking membrane uptake.
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Affiliation(s)
- Paul M. Jenkins
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Meng He
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Vann Bennett
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
- Howard Hughes Medical Institute, Durham, NC 27710, USA
- Corresponding author. E-mail:
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58
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Ullrich A, Böhme MA, Schöneberg J, Depner H, Sigrist SJ, Noé F. Dynamical Organization of Syntaxin-1A at the Presynaptic Active Zone. PLoS Comput Biol 2015; 11:e1004407. [PMID: 26367029 PMCID: PMC4569342 DOI: 10.1371/journal.pcbi.1004407] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 06/15/2015] [Indexed: 01/10/2023] Open
Abstract
Synaptic vesicle fusion is mediated by SNARE proteins forming in between synaptic vesicle (v-SNARE) and plasma membrane (t-SNARE), one of which is Syntaxin-1A. Although exocytosis mainly occurs at active zones, Syntaxin-1A appears to cover the entire neuronal membrane. By using STED super-resolution light microscopy and image analysis of Drosophila neuro-muscular junctions, we show that Syntaxin-1A clusters are more abundant and have an increased size at active zones. A computational particle-based model of syntaxin cluster formation and dynamics is developed. The model is parametrized to reproduce Syntaxin cluster-size distributions found by STED analysis, and successfully reproduces existing FRAP results. The model shows that the neuronal membrane is adjusted in a way to strike a balance between having most syntaxins stored in large clusters, while still keeping a mobile fraction of syntaxins free or in small clusters that can efficiently search the membrane or be traded between clusters. This balance is subtle and can be shifted toward almost no clustering and almost complete clustering by modifying the syntaxin interaction energy on the order of only 1 kBT. This capability appears to be exploited at active zones. The larger active-zone syntaxin clusters are more stable and provide regions of high docking and fusion capability, whereas the smaller clusters outside may serve as flexible reserve pool or sites of spontaneous ectopic release.
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Affiliation(s)
- Alexander Ullrich
- Department of Mathematics, Freie Universität Berlin, Berlin, Germany
| | - Mathias A. Böhme
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Berlin, Berlin, Germany
| | | | - Harald Depner
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stephan J. Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Berlin, Berlin, Germany
| | - Frank Noé
- Department of Mathematics, Freie Universität Berlin, Berlin, Germany
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59
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Lipid-bilayer-assisted two-dimensional self-assembly of DNA origami nanostructures. Nat Commun 2015; 6:8052. [PMID: 26310995 PMCID: PMC4560778 DOI: 10.1038/ncomms9052] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 07/10/2015] [Indexed: 12/21/2022] Open
Abstract
Self-assembly is a ubiquitous approach to the design and fabrication of novel supermolecular architectures. Here we report a strategy termed ‘lipid-bilayer-assisted self-assembly' that is used to assemble DNA origami nanostructures into two-dimensional lattices. DNA origami structures are electrostatically adsorbed onto a mica-supported zwitterionic lipid bilayer in the presence of divalent cations. We demonstrate that the bilayer-adsorbed origami units are mobile on the surface and self-assembled into large micrometre-sized lattices in their lateral dimensions. Using high-speed atomic force microscopy imaging, a variety of dynamic processes involved in the formation of the lattice, such as fusion, reorganization and defect filling, are successfully visualized. The surface modifiability of the assembled lattice is also demonstrated by in situ decoration with streptavidin molecules. Our approach provides a new strategy for preparing versatile scaffolds for nanofabrication and paves the way for organizing functional nanodevices in a micrometer space. Self-assembly is a useful method to fabricate novel supramolecular architectures. Here, the authors use lipid-bilayer-assisted self-assembly to obtain two-dimensional crystalline DNA origami lattices, imaging dynamic assembly phenomena using high-speed atomic force microscopy.
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60
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E-cadherin junction formation involves an active kinetic nucleation process. Proc Natl Acad Sci U S A 2015; 112:10932-7. [PMID: 26290581 DOI: 10.1073/pnas.1513775112] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Epithelial (E)-cadherin-mediated cell-cell junctions play important roles in the development and maintenance of tissue structure in multicellular organisms. E-cadherin adhesion is thus a key element of the cellular microenvironment that provides both mechanical and biochemical signaling inputs. Here, we report in vitro reconstitution of junction-like structures between native E-cadherin in living cells and the extracellular domain of E-cadherin (E-cad-ECD) in a supported membrane. Junction formation in this hybrid live cell-supported membrane configuration requires both active processes within the living cell and a supported membrane with low E-cad-ECD mobility. The hybrid junctions recruit α-catenin and exhibit remodeled cortical actin. Observations suggest that the initial stages of junction formation in this hybrid system depend on the trans but not the cis interactions between E-cadherin molecules, and proceed via a nucleation process in which protrusion and retraction of filopodia play a key role.
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61
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Šolman M, Ligabue A, Blaževitš O, Jaiswal A, Zhou Y, Liang H, Lectez B, Kopra K, Guzmán C, Härmä H, Hancock JF, Aittokallio T, Abankwa D. Specific cancer-associated mutations in the switch III region of Ras increase tumorigenicity by nanocluster augmentation. eLife 2015; 4:e08905. [PMID: 26274561 PMCID: PMC4563131 DOI: 10.7554/elife.08905] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/13/2015] [Indexed: 01/09/2023] Open
Abstract
Hotspot mutations of Ras drive cell transformation and tumorigenesis. Less frequent mutations in Ras are poorly characterized for their oncogenic potential. Yet insight into their mechanism of action may point to novel opportunities to target Ras. Here, we show that several cancer-associated mutations in the switch III region moderately increase Ras activity in all isoforms. Mutants are biochemically inconspicuous, while their clustering into nanoscale signaling complexes on the plasma membrane, termed nanocluster, is augmented. Nanoclustering dictates downstream effector recruitment, MAPK-activity, and tumorigenic cell proliferation. Our results describe an unprecedented mechanism of signaling protein activation in cancer. DOI:http://dx.doi.org/10.7554/eLife.08905.001 Cancer is a disease that develops when cells within the body acquire genetic mutations that allow them to grow and divide rapidly. Many human cancers have mutations in a gene that encodes a protein called Ras, which promotes cell growth and division by controlling the activities of other proteins. Ras congregates at the membrane that surrounds the cell and can assemble into clusters (called nanoclusters) that each contain six to eight Ras proteins. The tight packing of the proteins in these nanoclusters increases the amount of Ras in the membrane locally, which allows Ras to interact with other proteins more efficiently to promote growth and cell division. In normal cells, other proteins control when Ras is active. However, in many cancer cells, Ras is active all the time due to mutations that occur in three ‘hotspots’ within its gene. Other mutations in the gene that encodes Ras are also found in cancer cells, but these are less common and it is not clear how they alter the activity of the protein. Here, Solman et al. used microscopy and biochemical techniques to study the effects of some of the less common mutations on Ras activity in human cells. The experiments show that several mutations that alter a region of Ras called the ‘switch III region’ moderately increase the activity of Ras. The mutations probably alter the way that Ras sits in the membrane, which in turn changes the way it interacts with other proteins and the membrane so that more Ras nanoclusters form. Solman et al.'s findings reveal a new way that Ras can be activated in cancer cells. The next challenge is to develop drugs that block the formation of Ras nanoclusters and to find out if they have the potential to be used to treat cancer. DOI:http://dx.doi.org/10.7554/eLife.08905.002
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Affiliation(s)
- Maja Šolman
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
| | - Alessio Ligabue
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
| | - Olga Blaževitš
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
| | - Alok Jaiswal
- Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Yong Zhou
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, United States
| | - Hong Liang
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, United States
| | - Benoit Lectez
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
| | - Kari Kopra
- Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Camilo Guzmán
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
| | - Harri Härmä
- Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Turku, Finland
| | - John F Hancock
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, United States
| | - Tero Aittokallio
- Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Daniel Abankwa
- Turku Centre for Biotechnology, Åbo Akademi University, Turku, Finland
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62
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Ashdown GW, Cope A, Wiseman PW, Owen DM. Molecular flow quantified beyond the diffraction limit by spatiotemporal image correlation of structured illumination microscopy data. Biophys J 2015; 107:L21-3. [PMID: 25418107 DOI: 10.1016/j.bpj.2014.09.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/11/2014] [Accepted: 09/16/2014] [Indexed: 12/01/2022] Open
Abstract
We combine total internal reflection fluorescence structured illumination microscopy with spatiotemporal image correlation spectroscopy to quantify the flow velocities and directionality of filamentous-actin at the T cell immunological synapse. These techniques demonstrate it is possible to image retrograde flow of filamentous-actin at superresolution and provide flow quantification in the form of velocity histograms and flow vector maps. The flow was found to be retrograde and radially directed throughout the periphery of T-cells during synapse formation.
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Affiliation(s)
- George W Ashdown
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Andrew Cope
- Academic Department of Rheumatology, Centre for Molecular and Cellular Biology of Inflammation, Division of Immunology, Infection and Inflammatory Disease, King's College London, London, United Kingdom
| | - Paul W Wiseman
- Departments of Chemistry and Physics, McGill University, Montreal, Quebec, Canada
| | - Dylan M Owen
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.
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63
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Tanaka A, Nakashima H, Kashimura Y, Sumitomo K. Electrostatically induced planar lipid membrane formation on a cationic hydrogel array by the fusion of small negatively charged unilamellar vesicles. Colloids Surf A Physicochem Eng Asp 2015. [DOI: 10.1016/j.colsurfa.2015.03.049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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64
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Abstract
Galectins are a family of widely expressed β-galactoside-binding lectins in metazoans. The 15 mammalian galectins have either one or two conserved carbohydrate recognition domains (CRDs), with galectin-3 being able to pentamerize; they form complexes that crosslink glycosylated ligands to form a dynamic lattice. The galectin lattice regulates the diffusion, compartmentalization and endocytosis of plasma membrane glycoproteins and glycolipids. The galectin lattice also regulates the selection, activation and arrest of T cells, receptor kinase signaling and the functionality of membrane receptors, including the glucagon receptor, glucose and amino acid transporters, cadherins and integrins. The affinity of transmembrane glycoproteins to the galectin lattice is proportional to the number and branching of their N-glycans; with branching being mediated by Golgi N-acetylglucosaminyltransferase-branching enzymes and the supply of UDP-GlcNAc through metabolite flux through the hexosamine biosynthesis pathway. The relative affinities of glycoproteins for the galectin lattice depend on the activities of the Golgi enzymes that generate the epitopes of their ligands and, thus, provide a means to analyze biological function of lectins and of the 'glycome' more broadly.
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Affiliation(s)
- Ivan R Nabi
- Department of Cellular and Physiological Sciences, Life Sciences Institute, 2350 Health Sciences Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - Jay Shankar
- Department of Cellular and Physiological Sciences, Life Sciences Institute, 2350 Health Sciences Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - James W Dennis
- Department of Medical Genetics and Laboratory Medicine and Pathology, University of Toronto, Toronto, Ontario, Canada M5G 1L5
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65
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Ciesielska A, Kwiatkowska K. Modification of pro-inflammatory signaling by dietary components: The plasma membrane as a target. Bioessays 2015; 37:789-801. [DOI: 10.1002/bies.201500017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Anna Ciesielska
- Nencki Institute of Experimental Biology; Laboratory of Molecular Membrane Biology; Warsaw Poland
| | - Katarzyna Kwiatkowska
- Nencki Institute of Experimental Biology; Laboratory of Molecular Membrane Biology; Warsaw Poland
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66
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Each GPI-anchored protein species forms a specific lipid raft depending on its GPI attachment signal. Glycoconj J 2015; 32:531-40. [DOI: 10.1007/s10719-015-9595-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 04/15/2015] [Accepted: 04/23/2015] [Indexed: 10/23/2022]
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Huang H, Simsek MF, Jin W, Pralle A. Effect of receptor dimerization on membrane lipid raft structure continuously quantified on single cells by camera based fluorescence correlation spectroscopy. PLoS One 2015; 10:e0121777. [PMID: 25811483 PMCID: PMC4374828 DOI: 10.1371/journal.pone.0121777] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 02/10/2015] [Indexed: 02/07/2023] Open
Abstract
Membrane bound cell signaling is modulated by the membrane ultra-structure, which itself may be affected by signaling. However, measuring the interaction of membrane proteins with membrane structures in intact cells in real-time poses considerable challenges. In this paper we present a non-destructive fluorescence method that quantifies these interactions in single cells, and is able to monitor the same cell continuously to observe small changes. This approach combines total internal fluorescence microscopy with fluorescence correlation spectroscopy to measure the protein's diffusion and molecular concentration in different sized areas simultaneously. It correctly differentiates proteins interacting with membrane fences from proteins interacting with cholesterol-stabilized domains, or lipid rafts. This method detects small perturbations of the membrane ultra-structure or of a protein's tendency to dimerize. Through continuous monitoring of single cells, we demonstrate how dimerization of GPI-anchored proteins increases their association with the structural domains. Using a dual-color approach we study the effect of dimerization of one GPI-anchored protein on another type of GPI-anchored protein expressed in the same cell. Scans over the cell surface reveal a correlation between cholesterol stabilized domains and membrane cytoskeleton.
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Affiliation(s)
- Heng Huang
- Department of Physics, University at Buffalo the State University of New York, Buffalo, New York, United States of America
| | - M. Fethullah Simsek
- Department of Physics, University at Buffalo the State University of New York, Buffalo, New York, United States of America
| | - Weixiang Jin
- Department of Physics, University at Buffalo the State University of New York, Buffalo, New York, United States of America
| | - Arnd Pralle
- Department of Physics, University at Buffalo the State University of New York, Buffalo, New York, United States of America
- Department of Biophysics and Physiology, University at Buffalo the State University of New York, Buffalo, New York, United States of America
- * E-mail:
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68
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Trimble WS, Grinstein S. Barriers to the free diffusion of proteins and lipids in the plasma membrane. ACTA ACUST UNITED AC 2015; 208:259-71. [PMID: 25646084 PMCID: PMC4315255 DOI: 10.1083/jcb.201410071] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Biological membranes segregate into specialized functional domains of distinct composition, which can persist for the entire life of the cell. How separation of their lipid and (glyco)protein components is generated and maintained is not well understood, but the existence of diffusional barriers has been proposed. Remarkably, the physical nature of such barriers and the manner whereby they impede the free diffusion of molecules in the plane of the membrane has rarely been studied in depth. Moreover, alternative mechanisms capable of generating membrane inhomogeneity are often disregarded. Here we describe prototypical biological systems where membrane segregation has been amply documented and discuss the role of diffusional barriers and other processes in the generation and maintenance of their structural and functional compartmentalization.
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Affiliation(s)
- William S Trimble
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Sergio Grinstein
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5C 1N8, Canada
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69
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Lin CY, Huang JY, Lo LW. Unraveling the impact of lipid domains on the dimerization processes of single-molecule EGFRs of live cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:886-93. [DOI: 10.1016/j.bbamem.2014.12.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/21/2014] [Accepted: 12/18/2014] [Indexed: 10/24/2022]
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70
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Katoch P, Mitra S, Ray A, Kelsey L, Roberts BJ, Wahl JK, Johnson KR, Mehta PP. The carboxyl tail of connexin32 regulates gap junction assembly in human prostate and pancreatic cancer cells. J Biol Chem 2015; 290:4647-4662. [PMID: 25548281 PMCID: PMC4335205 DOI: 10.1074/jbc.m114.586057] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 12/23/2014] [Indexed: 12/20/2022] Open
Abstract
Connexins, the constituent proteins of gap junctions, are transmembrane proteins. A connexin (Cx) traverses the membrane four times and has one intracellular and two extracellular loops with the amino and carboxyl termini facing the cytoplasm. The transmembrane and the extracellular loop domains are highly conserved among different Cxs, whereas the carboxyl termini, often called the cytoplasmic tails, are highly divergent. We have explored the role of the cytoplasmic tail of Cx32, a Cx expressed in polarized and differentiated cells, in regulating gap junction assembly. Our results demonstrate that compared with the full-length Cx32, the cytoplasmic tail-deleted Cx32 is assembled into small gap junctions in human pancreatic and prostatic cancer cells. Our results further document that the expression of the full-length Cx32 in cells, which express the tail-deleted Cx32, increases the size of gap junctions, whereas the expression of the tail-deleted Cx32 in cells, which express the full-length Cx32, has the opposite effect. Moreover, we show that the tail is required for the clustering of cell-cell channels and that in cells expressing the tail-deleted Cx32, the expression of cell surface-targeted cytoplasmic tail alone is sufficient to enhance the size of gap junctions. Our live-cell imaging data further demonstrate that gap junctions formed of the tail-deleted Cx32 are highly mobile compared with those formed of full-length Cx32. Our results suggest that the cytoplasmic tail of Cx32 is not required to initiate the assembly of gap junctions but for their subsequent growth and stability. Our findings suggest that the cytoplasmic tail of Cx32 may be involved in regulating the permeability of gap junctions by regulating their size.
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Affiliation(s)
- Parul Katoch
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Shalini Mitra
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Anuttoma Ray
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Linda Kelsey
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Brett J Roberts
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - James K Wahl
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Keith R Johnson
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Parmender P Mehta
- From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
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71
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Kuokkanen E, Šuštar V, Mattila PK. Molecular control of B cell activation and immunological synapse formation. Traffic 2015; 16:311-26. [PMID: 25639463 DOI: 10.1111/tra.12257] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/29/2014] [Accepted: 12/29/2014] [Indexed: 02/01/2023]
Abstract
B cells form an essential part of the adaptive immune system by producing specific antibodies that can neutralize toxins and target infected or malignant cells for destruction. During B cell activation, a fundamental role is played by a specialized intercellular structure called the immunological synapse (IS). The IS serves as a platform for B cell recognition of foreign, often pathogenic, antigens on the surface of antigen-presenting cells (APC). This recognition is elicited by highly specific B cell receptors (BCR) that subsequently trigger carefully orchestrated intracellular signaling cascades that lead to cell activation. Furthermore, antigen internalization, essential for full B cell activation and differentiation into antibody producing effector cells or memory cells, occurs in the IS. Recent developments especially in various imaging-based methods have considerably advanced our understanding of the molecular control of B cell activation. Interestingly, the cellular cytoskeleton is emerging as a key player at several stages of B cell activation, including the initiation of receptor signaling. Here, we discuss the functions and molecular mechanisms of the IS and highlight the multifaceted role of the actin cytoskeleton in several aspects of B cell activation.
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Affiliation(s)
- Elina Kuokkanen
- Unit of Pathology, Institute of Biomedicine, University of Turku, Turku, Finland
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72
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Weichert JP, Clark PA, Kandela IK, Vaccaro AM, Clarke W, Longino MA, Pinchuk AN, Farhoud M, Swanson KI, Floberg JM, Grudzinski J, Titz B, Traynor AM, Chen HE, Hall LT, Pazoles CJ, Pickhardt PJ, Kuo JS. Alkylphosphocholine analogs for broad-spectrum cancer imaging and therapy. Sci Transl Med 2015; 6:240ra75. [PMID: 24920661 DOI: 10.1126/scitranslmed.3007646] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Many solid tumors contain an overabundance of phospholipid ethers relative to normal cells. Capitalizing on this difference, we created cancer-targeted alkylphosphocholine (APC) analogs through structure-activity analyses. Depending on the iodine isotope used, radioiodinated APC analog CLR1404 was used as either a positron emission tomography (PET) imaging ((124)I) or molecular radiotherapeutic ((131)I) agent. CLR1404 analogs displayed prolonged tumor-selective retention in 55 in vivo rodent and human cancer and cancer stem cell models. (131)I-CLR1404 also displayed efficacy (tumor growth suppression and survival extension) in a wide range of human tumor xenograft models. Human PET/CT (computed tomography) and SPECT (single-photon emission computed tomography)/CT imaging in advanced-cancer patients with (124)I-CLR1404 or (131)I-CLR1404, respectively, demonstrated selective uptake and prolonged retention in both primary and metastatic malignant tumors. Combined application of these chemically identical APC-based radioisosteres will enable personalized dual modality cancer therapy of using molecular (124)I-CLR1404 tumor imaging for planning (131)I-CLR1404 therapy.
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Affiliation(s)
- Jamey P Weichert
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA.
| | - Paul A Clark
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Irawati K Kandela
- Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Abram M Vaccaro
- Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - William Clarke
- Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Marc A Longino
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Anatoly N Pinchuk
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Mohammed Farhoud
- Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Kyle I Swanson
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - John M Floberg
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Joseph Grudzinski
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Benjamin Titz
- Cellectar Biosciences Inc., 3301 Agriculture Drive, Madison, WI 53716, USA
| | - Anne M Traynor
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Hong-En Chen
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Lance T Hall
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | | | - Perry J Pickhardt
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - John S Kuo
- Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA. Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA.
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73
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Suzuki KG. New Insights into the Organization of Plasma Membrane and Its Role in Signal Transduction. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:67-96. [DOI: 10.1016/bs.ircmb.2015.02.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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74
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Lin CY, Huang JY, Lo LW. Energetic modeling and single-molecule verification of dynamic regulation on receptor complexes by actin corrals and lipid raft domains. J Chem Phys 2014; 141:215102. [DOI: 10.1063/1.4902985] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chien Y. Lin
- Department of Photonics, Chiao Tung University, Hsinchu 300, Taiwan
| | - Jung Y. Huang
- The T.K.B. Research Center of Photonics, Chiao Tung University, Hsinchu 300, Taiwan
| | - Leu-Wei Lo
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Zhunan, Miaoli 350, Taiwan
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75
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Yoshida A, Sakai N, Uekusa Y, Deguchi K, Gilmore JL, Kumeta M, Ito S, Takeyasu K. Probing in vivo dynamics of mitochondria and cortical actin networks using high-speed atomic force/fluorescence microscopy. Genes Cells 2014; 20:85-94. [PMID: 25440894 DOI: 10.1111/gtc.12204] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/06/2014] [Indexed: 12/12/2022]
Abstract
The dynamics of the cell membrane and submembrane structures are closely linked, facilitating various cellular activities. Although cell surface research and cortical actin studies have shown independent mechanisms for the cell membrane and the actin network, it has been difficult to obtain a comprehensive understanding of the dynamics of these structures in live cells. Here, we used a combined atomic force/optical microscope system to analyze membrane-based cellular events at nanometer-scale resolution in live cells. Imaging the COS-7 cell surface showed detailed structural properties of membrane invagination events corresponding to endocytosis and exocytosis. In addition, the movement of mitochondria and the spatiotemporal dynamics of the cortical F-actin network were directly visualized in vivo. Cortical actin microdomains with sizes ranging from 1.7×10(4) to 1.4×10(5) nm2 were dynamically rearranged by newly appearing actin filaments, which sometimes accompanied membrane invaginations, suggesting that these events are integrated with the dynamic regulation of submembrane organizations maintained by actin turnovers. These results provide novel insights into the structural aspects of the entire cell membrane machinery which can be visualized with high temporal and spatial resolution.
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Affiliation(s)
- Aiko Yoshida
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
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76
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Aigal S, Claudinon J, Römer W. Plasma membrane reorganization: A glycolipid gateway for microbes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:858-71. [PMID: 25450969 DOI: 10.1016/j.bbamcr.2014.11.014] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 09/27/2014] [Accepted: 11/11/2014] [Indexed: 02/08/2023]
Abstract
Ligand-receptor interactions, which represent the core for cell signaling and internalization processes are largely affected by the spatial configuration of host cell receptors. There is a growing piece of evidence that receptors are not homogeneously distributed within the plasma membrane, but are rather pre-clustered in nanodomains, or clusters are formed upon ligand binding. Pathogens have evolved many strategies to evade the host immune system and to ensure their survival by hijacking plasma membrane receptors that are most often associated with lipid rafts. In this review, we discuss the early stage molecular and physiological events that occur following ligand binding to host cell glycolipids. The ability of various biological ligands (e.g. toxins, lectins, viruses or bacteria) that bind to glycolipids to induce their own uptake into mammalian cells by creating negative membrane curvature and membrane invaginations is explored. We highlight recent trends in understanding nanoscale plasma membrane (re-)organization and present the benefits of using synthetic membrane systems. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.
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Affiliation(s)
- Sahaja Aigal
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, Schänzlestraβe 18, 79104 Freiburg, Germany; International Max Planck Research School for Molecular and Cellular Biology (IMPRS-MCB), Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany.
| | - Julie Claudinon
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, Schänzlestraβe 18, 79104 Freiburg, Germany
| | - Winfried Römer
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, Schänzlestraβe 18, 79104 Freiburg, Germany.
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77
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Holmes SE, Bachran C, Fuchs H, Weng A, Melzig MF, Flavell SU, Flavell DJ. Triterpenoid saponin augmention of saporin-based immunotoxin cytotoxicity for human leukaemia and lymphoma cells is partially immunospecific and target molecule dependent. Immunopharmacol Immunotoxicol 2014; 37:42-55. [PMID: 25347443 DOI: 10.3109/08923973.2014.971964] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CONTEXT Saponinum album (SA) is a complex mixture of triterpenoid saponins previously shown to augment the cytotoxicity of the type I ribosome-inactivating protein saporin and an EGF-saporin target toxin that could potentially be used to improve the therapeutic window of targeted toxins. OBJECTIVE To investigate the augmentative property of SA on saporin and saporin-based immunotoxins (IT) directed against five different cell surface target molecules on human leukemia and lymphoma cells. MATERIALS AND METHODS After determining the optimum dose of SA for each cell line, the extent of SA-mediated augmentation was established for saporin and five saporin-based ITs using XTT and an annexin V apoptosis assay. Immunospecificity was investigated using three different blocking assays. Dose-scheduling was also investigated using the XTT assay. RESULTS Uncorrected SA-mediated augmentation ranged at best from 31.5 million-fold to, at worse, 174-fold. However, when the calculated fold-increases were adjusted for the non-immunospecific effects of SA on an off-target IT, the true augmentative effects of SA were found to be largely non-immunospecific. Antibody blocking studies demonstrated that the augmentative effect of SA was only partially immunospecific. Separate exposure of target cells to IT and SA at different times demonstrated that immunospecific augmentation of IT by SA could be achieved but only if cells were exposed to IT first and SA second. CONCLUSIONS SA significantly, although variably, augments the cytotoxicity of saporin and saporin-based immunotoxins. Concomitant exposure to both IT and SA can result in non-immunospecific cytotoxicity that can be overcome by temporally separating exposure to each.
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Affiliation(s)
- Suzanne E Holmes
- The Simon Flavell Leukaemia Research Laboratory, Southampton General Hospital , Southampton , UK
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Trojanova J, Kulik A, Janacek J, Kralikova M, Syka J, Turecek R. Distribution of glycine receptors on the surface of the mature calyx of Held nerve terminal. Front Neural Circuits 2014; 8:120. [PMID: 25339867 PMCID: PMC4186306 DOI: 10.3389/fncir.2014.00120] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 09/12/2014] [Indexed: 11/13/2022] Open
Abstract
The physiological functions of glycine receptors (GlyRs) depend on their subcellular locations. In axonal terminals of the central neurons, GlyRs trigger a slow facilitation of presynaptic transmitter release; however, their spatial relationship to the release sites is not known. In this study, we examined the distribution of GlyRs in the rat glutamatergic calyx of Held nerve terminal using high-resolution pre-embedding immunoelectron microscopy. We performed a quantitative analysis of GlyR-associated immunogold (IG) labeling in 3D reconstructed calyceal segments. A variable density of IG particles and their putative accumulations, inferred from the frequency distribution of inter-IG distances, indicated a non-uniform distribution of the receptors in the calyx. Subsequently, increased densities of IG particles were found in calyceal swellings, structures characterized by extensive exocytosis of glutamate. In swellings as well as in larger calyceal stalks, IG particles did not tend to accumulate near the glutamate releasing zones. On the other hand, GlyRs in swellings (but not in stalks) preferentially occupied membrane regions, unconnected to postsynaptic cells and presumably accessible by ambient glycine. Furthermore, the sites with increased GlyR concentrations were found in swellings tightly juxtaposed with GABA/glycinergic nerve endings. Thus, the results support the concept of an indirect mechanism underlying the modulatory effects of calyceal GlyRs, activated by glycine spillover. We also suggest the existence of an activity-dependent mechanism regulating the surface distribution of α homomeric GlyRs in axonal terminals of central neurons.
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Affiliation(s)
- Johana Trojanova
- Department of Auditory Neuroscience, Laboratory of Synaptic Transmission, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic Prague, Czech Republic
| | - Akos Kulik
- Department of Physiology II, University of Freiburg Freiburg, Germany ; BIOSS Centre for Biological Signalling Studies, University of Freiburg Freiburg, Germany
| | - Jiri Janacek
- Department of Biomathematics, Institute of Physiology, Academy of Sciences of the Czech Republic Prague, Czech Republic
| | - Michaela Kralikova
- Department of Auditory Neuroscience, Laboratory of Synaptic Transmission, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic Prague, Czech Republic
| | - Josef Syka
- Department of Auditory Neuroscience, Laboratory of Synaptic Transmission, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic Prague, Czech Republic
| | - Rostislav Turecek
- Department of Auditory Neuroscience, Laboratory of Synaptic Transmission, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic Prague, Czech Republic
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You C, Richter CP, Löchte S, Wilmes S, Piehler J. Dynamic Submicroscopic Signaling Zones Revealed by Pair Correlation Tracking and Localization Microscopy. Anal Chem 2014; 86:8593-602. [DOI: 10.1021/ac501127r] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Changjiang You
- Department
of Biology, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Christian P. Richter
- Department
of Biology, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Sara Löchte
- Department
of Biology, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Stephan Wilmes
- Department
of Biology, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Jacob Piehler
- Department
of Biology, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany
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80
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Tracking single molecules at work in living cells. Nat Chem Biol 2014; 10:524-32. [PMID: 24937070 DOI: 10.1038/nchembio.1558] [Citation(s) in RCA: 218] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 05/21/2014] [Indexed: 11/09/2022]
Abstract
Methods for imaging and tracking single molecules conjugated with fluorescent probes, called single-molecule tracking (SMT), are now providing researchers with the unprecedented ability to directly observe molecular behaviors and interactions in living cells. Current SMT methods are achieving almost the ultimate spatial precision and time resolution for tracking single molecules, determined by the currently available dyes. In cells, various molecular interactions and reactions occur as stochastic and probabilistic processes. SMT provides an ideal way to directly track these processes by observing individual molecules at work in living cells, leading to totally new views of the biochemical and molecular processes used by cells whether in signal transduction, gene regulation or formation and disintegration of macromolecular complexes. Here we review SMT methods, summarize the recent results obtained by SMT, including related superresolution microscopy data, and describe the special concerns when SMT applications are shifted from the in vitro paradigms to living cells.
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81
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Morinaga T, Abe K, Nakayama Y, Yamaguchi N, Yamaguchi N. Activation of Lyn tyrosine kinase through decreased membrane cholesterol levels during a change in its membrane distribution upon cell detachment. J Biol Chem 2014; 289:26327-26343. [PMID: 25104351 DOI: 10.1074/jbc.m114.580001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular membranes, which can serve as scaffolds for signal transduction, dynamically change their characteristics upon cell detachment. Src family kinases undergo post-translational lipid modification and are involved in a wide range of signaling events at the plasma membrane, such as cell proliferation, cell adhesion, and survival. Previously, we showed the differential membrane distributions among the members of Src family kinases by sucrose density gradient fractionation. However, little is known about the regulation of the membrane distribution of Src family kinases upon cell detachment. Here, we show that cell detachment shifts the main peak of the membrane distribution of Lyn, a member of Src family kinase, from the low density to the high density membrane fractions and enhances the kinase activity of Lyn. The change in Lyn distribution upon cell detachment involves both dynamin activity and a decrease in membrane cholesterol. Cell detachment activates Lyn through decreased membrane cholesterol levels during a change in its membrane distribution. Furthermore, cholesterol incorporation decreases Lyn activity and reduces the viability of suspension cells. These results suggest that cell detachment-induced Lyn activation through the change in the membrane distribution of Lyn plays an important role in survival of suspension cells.
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Affiliation(s)
- Takao Morinaga
- Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan
| | - Kohei Abe
- Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan
| | - Yuji Nakayama
- Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan
| | - Noritaka Yamaguchi
- Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan
| | - Naoto Yamaguchi
- Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.
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82
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Song W, Liu C, Seeley-Fallen MK, Miller H, Ketchum C, Upadhyaya A. Actin-mediated feedback loops in B-cell receptor signaling. Immunol Rev 2014; 256:177-89. [PMID: 24117821 DOI: 10.1111/imr.12113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Upon recognizing cognate antigen, B cells mobilize multiple cellular apparatuses to propagate an optimal response. Antigen binding is transduced into cytoplasmic signaling events through B-cell antigen receptor (BCR)-based signalosomes at the B-cell surface. BCR signalosomes are dynamic and transient and are subsequently endocytosed for antigen processing. The function of BCR signalosomes is one of the determining factors for the fate of B cells: clonal expansion, anergy, or apoptosis. Accumulating evidence underscores the importance of the actin cytoskeleton in B-cell activation. We have begun to appreciate the role of actin dynamics in regulating BCR-mediated tonic signaling and the formation of BCR signalosomes. Our recent studies reveal an additional function of the actin cytoskeleton in the downregulation of BCR signaling, consequently contributing to the generation and maintenance of B-cell self-tolerance. In this review, we discuss how actin remodels its organization and dynamics in close coordination with BCR signaling and how actin remodeling in turn amplifies the activation and subsequent downregulation process of BCR signaling, providing vital feedback for optimal BCR activation.
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Affiliation(s)
- Wenxia Song
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
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83
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Starr FW, Hartmann B, Douglas JF. Dynamical clustering and a mechanism for raft-like structures in a model lipid membrane. SOFT MATTER 2014; 10:3036-47. [PMID: 24695573 PMCID: PMC4020150 DOI: 10.1039/c3sm53187b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We use molecular dynamics simulations to examine the dynamical heterogeneity of a model single-component lipid membrane using a coarse-grained representation of lipid molecules. This model qualitatively reproduces the known phase transitions between disordered, ordered, and gel membrane phases, and the phase transitions are accompanied by significant changes in the nature of the lipid dynamics. In particular, lipid diffusion in the liquid-ordered phase is hindered by the transient trapping of molecules by their neighbors, similar to the dynamics of a liquid approaching its glass transition. This transient molecular caging gives rise to two distinct mobility groups within a single-component membrane: lipids that are transiently trapped, and lipids with displacements on the scale of the intermolecular spacing. Most significantly, lipids within these distinct mobility states spatially segregate, creating transient "islands" of enhanced mobility having a size and time scale compatible with lipid "rafts," dynamical structures thought to be important for cell membrane function. Although the dynamic lipid clusters that we observe do not themselves correspond to rafts (which are more complex, multicomponent structures), we hypothesize that such rafts may develop from the same universal mechanism, explaining why raft-like regions should arise, regardless of lipid structural or compositional details. These clusters are strikingly similar to the dynamical clusters found in glass-forming fluids, and distinct from phase-separation clusters. We also show that mobile lipid clusters can be dissected into smaller clusters of cooperatively rearranging molecules. The geometry of these clusters can be understood in the context of branched equilibrium polymers, related to percolation theory. We discuss how these dynamical structures relate to a range observations on the dynamics of lipid membranes.
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Affiliation(s)
- Francis W Starr
- Department of Physics, Wesleyan University, Middletown, CT 06459, USA.
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84
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Miyagawa-Yamaguchi A, Kotani N, Honke K. Expressed glycosylphosphatidylinositol-anchored horseradish peroxidase identifies co-clustering molecules in individual lipid raft domains. PLoS One 2014; 9:e93054. [PMID: 24671047 PMCID: PMC3966864 DOI: 10.1371/journal.pone.0093054] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 03/02/2014] [Indexed: 11/18/2022] Open
Abstract
Lipid rafts that are enriched in glycosylphosphatidylinositol (GPI)-anchored proteins serve as a platform for important biological events. To elucidate the molecular mechanisms of these events, identification of co-clustering molecules in individual raft domains is required. Here we describe an approach to this issue using the recently developed method termed enzyme-mediated activation of radical source (EMARS), by which molecules in the vicinity within 300 nm from horseradish peroxidase (HRP) set on the probed molecule are labeled. GPI-anchored HRP fusion proteins (HRP-GPIs), in which the GPI attachment signals derived from human decay accelerating factor and Thy-1 were separately connected to the C-terminus of HRP, were expressed in HeLa S3 cells, and the EMARS reaction was catalyzed by these expressed HRP-GPIs under a living condition. As a result, these different HRP-GPIs had differences in glycosylation and localization and formed distinct clusters. This novel approach distinguished molecular clusters associated with individual GPI-anchored proteins, suggesting that it can identify co-clustering molecules in individual raft domains.
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Affiliation(s)
- Arisa Miyagawa-Yamaguchi
- Kochi System Glycobiology Center, Kochi University Medical School, Nankoku, Kochi, Japan
- Center for Innovate and Translational Medicine, Kochi University Medical School, Nankoku, Kochi, Japan
| | - Norihiro Kotani
- Kochi System Glycobiology Center, Kochi University Medical School, Nankoku, Kochi, Japan
- Center for Innovate and Translational Medicine, Kochi University Medical School, Nankoku, Kochi, Japan
- Department of Biochemistry, Saitama Medical University, Iruma-gun, Saitama, Japan
| | - Koichi Honke
- Kochi System Glycobiology Center, Kochi University Medical School, Nankoku, Kochi, Japan
- Center for Innovate and Translational Medicine, Kochi University Medical School, Nankoku, Kochi, Japan
- Department of Biochemistry, Kochi University Medical School, Nankoku, Kochi, Japan
- * E-mail:
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85
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Hiramoto-Yamaki N, Tanaka KAK, Suzuki KGN, Hirosawa KM, Miyahara MSH, Kalay Z, Tanaka K, Kasai RS, Kusumi A, Fujiwara TK. Ultrafast diffusion of a fluorescent cholesterol analog in compartmentalized plasma membranes. Traffic 2014; 15:583-612. [PMID: 24506328 PMCID: PMC4265843 DOI: 10.1111/tra.12163] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 02/05/2014] [Accepted: 02/07/2014] [Indexed: 01/20/2023]
Abstract
Cholesterol distribution and dynamics in the plasma membrane (PM) are poorly understood. The recent development of Bodipy488-conjugated cholesterol molecule (Bdp-Chol) allowed us to study cholesterol behavior in the PM, using single fluorescent-molecule imaging. Surprisingly, in the intact PM, Bdp-Chol diffused at the fastest rate ever found for any molecules in the PM, with a median diffusion coefficient (D) of 3.4 µm2/second, which was ∼10 times greater than that of non-raft phospholipid molecules (0.33 µm2/second), despite Bdp-Chol's probable association with raft domains. Furthermore, Bdp-Chol exhibited no sign of entrapment in time scales longer than 0.5 milliseconds. In the blebbed PM, where actin filaments were largely depleted, Bdp-Chol and Cy3-conjugated dioleoylphosphatidylethanolamine (Cy3-DOPE) diffused at comparable Ds (medians = 5.8 and 6.2 µm2/second, respectively), indicating that the actin-based membrane skeleton reduces the D of Bdp-Chol only by a factor of ∼2 from that in the blebbed PM, whereas it reduces the D of Cy3-DOPE by a factor of ∼20. These results are consistent with the previously proposed model, in which the PM is compartmentalized by the actin-based membrane-skeleton fence and its associated transmembrane picket proteins for the macroscopic diffusion of all of the membrane molecules, and suggest that the probability of Bdp-Chol passing through the compartment boundaries, once it enters the boundary, is ∼10× greater than that of Cy3-DOPE. Since the compartment sizes are greater than those of the putative raft domains, we conclude that raft domains coexist with membrane-skeleton-induced compartments and are contained within them.
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Affiliation(s)
- Nao Hiramoto-Yamaki
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS) and Institute for Frontier Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan
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86
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Distinct regions of triadin are required for targeting and retention at the junctional domain of the sarcoplasmic reticulum. Biochem J 2014; 458:407-17. [DOI: 10.1042/bj20130719] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Three regions contribute to triadin localization to the junctional sarcoplasmic reticulum. Dynamics studies revealed that TR3 mediates triadin stability at junctional sites. The stable association of triadin at the junctional sites is facilitated by interactions with calsequestrin-1.
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87
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Sodt AJ, Sandar ML, Gawrisch K, Pastor RW, Lyman E. The molecular structure of the liquid-ordered phase of lipid bilayers. J Am Chem Soc 2014; 136:725-32. [PMID: 24345334 DOI: 10.1021/ja4105667] [Citation(s) in RCA: 173] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Molecular dynamics simulations reveal substructures within the liquid-ordered phase of lipid bilayers. These substructures, identified in a 10 μs all-atom trajectory of liquid-ordered/liquid-disordered coexistence (L(o)/L(d)) are composed of saturated hydrocarbon chains packed with local hexagonal order and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the L(o) phase are in excellent agreement with (2)H NMR measurements; the local hexagonal packing is also consistent with (1)H-MAS NMR spectra of the L(o) phase, NMR diffusion experiments, and small-angle X-ray and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the L(o) regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways.
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Affiliation(s)
- Alexander J Sodt
- National Heart, Lung, and Blood Institute and §National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health , Bethesda, Maryland 20892, United States
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88
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Beutel O, Nikolaus J, Birkholz O, You C, Schmidt T, Herrmann A, Piehler J. High-Fidelity Protein Targeting into Membrane Lipid Microdomains in Living Cells. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306328] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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89
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Beutel O, Nikolaus J, Birkholz O, You C, Schmidt T, Herrmann A, Piehler J. High-Fidelity Protein Targeting into Membrane Lipid Microdomains in Living Cells. Angew Chem Int Ed Engl 2013; 53:1311-5. [DOI: 10.1002/anie.201306328] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 10/04/2013] [Indexed: 12/26/2022]
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90
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Dong G, Wang C, Wu Y, Cong J, Cheng L, Wang M, Zhao P, Tang L, Zhang C, Wu K. Tat peptide-mediated soluble expression of the membrane protein LSECtin-CRD in Escherichia coli. PLoS One 2013; 8:e83579. [PMID: 24358298 PMCID: PMC3865297 DOI: 10.1371/journal.pone.0083579] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 11/05/2013] [Indexed: 12/22/2022] Open
Abstract
The human liver and lymph node sinusoidal endothelial cell C-type lectin (hLSECtin), a type II integral membrane protein, containing a Ca2+-dependent carbohydrate recognition domain (CRD), has a well-established biological activity, yet its three-dimensional structure is unknown due to low expression yields and aggregation into inclusion bodies. Previous study has demonstrated that the HIV-1 virus-encoded Tat peptide (‘YGRKKRRQRRR’) can increase the yields and the solubility of heterologous proteins. However, whether the Tat peptide could promote the high-yield and soluble expression of membrane proteins in Escherichia coli is not known. Therefore, the prokaryotic expression vector pET28b-Tat-hLSECtin-CRD (using pET28b and pET28b-hLSECtin-CRD as controls) was constructed, and transformed into E. coli BL21 (DE3) cells and induced with isopropyl-β-d-thiogalactoside (IPTG) followed with identifying by SDS-PAGE and Western blot. Subsequently, the bacterial subcellular structure, in which overexpressed the heterologous proteins Tat-hLSECtin-CRD and Tat-free hLSECtin-CRD, was analyzed by transmission electron microscope (TEM) respectively, and the mannose-binding activity of Tat-hLSECtin-CRD was also determined. Expectedly, the solubility of Tat-LSECtin-CRD significantly increased compared to Tat-free LSECtin-CRD (**p < 0.01) with prolonged time, and the Tat-LSECtin-CRD had a significant mannose-binding activity. The subcellular structure analysis indicated that the bacterial cells overexpressed Tat-hLSECtin-CRD exhibited denser region compared with controls, while dot denser region aggregated in the two ends of bacterial cells overexpressed Tat-free hLSECtin-CRD. This study provided a novel method for improving the soluble expression of membrane proteins in prokaryotic systems by fusion with the Tat peptide, which may be potentially expanded to the expression of other membrane proteins.
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MESH Headings
- Carbohydrate Metabolism/genetics
- Cloning, Molecular
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Gene Expression Regulation, Bacterial
- Humans
- Lectins, C-Type/chemistry
- Lectins, C-Type/genetics
- Lectins, C-Type/isolation & purification
- Lectins, C-Type/metabolism
- Mannose/metabolism
- Organisms, Genetically Modified
- Peptide Fragments/chemistry
- Peptide Fragments/genetics
- Peptide Fragments/metabolism
- Protein Binding
- Protein Interaction Domains and Motifs/genetics
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/isolation & purification
- Recombinant Fusion Proteins/metabolism
- Solubility
- tat Gene Products, Human Immunodeficiency Virus/chemistry
- tat Gene Products, Human Immunodeficiency Virus/genetics
- tat Gene Products, Human Immunodeficiency Virus/metabolism
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Affiliation(s)
- Guofu Dong
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Changzhen Wang
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Yonghong Wu
- Beijing Institute of Radiation Medicine, State Key Laboratory of Proteomics, Cognitive and Mental Health Research Center of PLA, Beijing, P. R. China
| | - Jianbo Cong
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Li Cheng
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Mingqun Wang
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Pengkai Zhao
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
| | - Li Tang
- Beijing Institute of Radiation Medicine, Department of Genomics and Proteomics, Chinese Human Genome Center, Beijing, P. R. China
- * E-mail: (LT); (CZ); (KW)
| | - Chenggang Zhang
- Beijing Institute of Radiation Medicine, State Key Laboratory of Proteomics, Cognitive and Mental Health Research Center of PLA, Beijing, P. R. China
- * E-mail: (LT); (CZ); (KW)
| | - Ke Wu
- Beijing Institute of Radiation Medicine, Beijing, P. R. China
- * E-mail: (LT); (CZ); (KW)
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91
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Özhan G, Sezgin E, Wehner D, Pfister AS, Kühl SJ, Kagermeier-Schenk B, Kühl M, Schwille P, Weidinger G. Lypd6 enhances Wnt/β-catenin signaling by promoting Lrp6 phosphorylation in raft plasma membrane domains. Dev Cell 2013; 26:331-45. [PMID: 23987510 DOI: 10.1016/j.devcel.2013.07.020] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Revised: 05/23/2013] [Accepted: 07/29/2013] [Indexed: 11/19/2022]
Abstract
Wnt/β-catenin signaling plays critical roles during embryogenesis, tissue homeostasis, and regeneration. How Wnt-receptor complex activity is regulated is not yet fully understood. Here, we identify the Ly6 family protein LY6/PLAUR domain-containing 6 (Lypd6) as a positive feedback regulator of Wnt/β-catenin signaling. lypd6 enhances Wnt signaling in zebrafish and Xenopus embryos and in mammalian cells, and it is required for wnt8-mediated patterning of the mesoderm and neuroectoderm during zebrafish gastrulation. Lypd6 is GPI anchored to the plasma membrane and physically interacts with the Wnt receptor Frizzled8 and the coreceptor Lrp6. Biophysical and biochemical evidence indicates that Lypd6 preferentially localizes to raft membrane domains, where Lrp6 is phosphorylated upon Wnt stimulation. lypd6 knockdown or mislocalization of the Lypd6 protein to nonraft membrane domains shifts Lrp6 phosphorylation to these domains and inhibits Wnt signaling. Thus, Lypd6 appears to control Lrp6 activation specifically in membrane rafts, which is essential for downstream signaling.
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Affiliation(s)
- Günes Özhan
- Biotechnology Center, Technische Universität Dresden, Tatzberg 47, 01307 Dresden, Germany
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92
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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93
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Blouin CM, Lamaze C. Interferon gamma receptor: the beginning of the journey. Front Immunol 2013; 4:267. [PMID: 24027571 PMCID: PMC3760442 DOI: 10.3389/fimmu.2013.00267] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 08/19/2013] [Indexed: 12/17/2022] Open
Abstract
Our view of endocytosis and membrane trafficking of transmembrane receptors has dramatically changed over the last 20 years. Several new endocytic routes have been discovered and mechanistically characterized in mammalian cells. Long considered as a passive means to terminate signaling through down-regulation of the number of activated receptors at the plasma membrane, it is now established that receptor endocytosis and endosomal sorting can be directly linked to the regulation of intracellular signaling pathways. The functional links between membrane trafficking of interferon receptors and JAK/STAT signaling have recently begun to be unraveled. These studies raise the exciting possibility that a certain level of signal specificity can be achieved through endocytosis and selective localization of the activated complexes within cellular membranes. The ongoing development of high-resolution cell imaging techniques with better spatial and temporal resolution gives new means of deciphering the inherent complexity of membrane trafficking and signaling. This should help to better comprehend the molecular mechanisms by which endocytosis and endosomal sorting of interferon receptors can orchestrate signaling selectivity within the JAK/STAT pathway that can be activated by as many as 60 different cytokines, growth factors, and hormones.
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Affiliation(s)
- Cédric M. Blouin
- Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, Institut Curie – Centre de Recherche, Paris, France
- CNRS UMR144, Paris, France
| | - Christophe Lamaze
- Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, Institut Curie – Centre de Recherche, Paris, France
- CNRS UMR144, Paris, France
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94
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The actin cytoskeleton coordinates the signal transduction and antigen processing functions of the B cell antigen receptor. ACTA ACUST UNITED AC 2013; 8:475-485. [PMID: 24999354 DOI: 10.1007/s11515-013-1272-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The B cell antigen receptor (BCR) is the sensor on the B cell surface that surveys foreign molecules (antigen) in our bodies and activates B cells to generate antibody responses upon encountering cognate antigen. The binding of antigen to the BCR induces signaling cascades in the cytoplasm, which provides the first signal for B cell activation. Subsequently, BCRs internalize and target bound antigen to endosomes, where antigen is processed into T cell recognizable forms. T helper cells generate the second activation signal upon binding to antigen presented by B cells. The optimal activation of B cells requires both signals, thereby depending on the coordination of BCR signaling and antigen transport functions. Antigen binding to the BCR also induces rapid remodeling of the cortical actin network of B cells. While being initiated and controlled by BCR signaling, recent studies reveal that this actin remodeling is critical for both the signaling and antigen processing functions of the BCR, indicating a role for actin in coordinating these two pathways. Here we will review previous and recent studies on actin reorganization during BCR activation and BCR-mediated antigen processing, and discuss how actin remodeling translates BCR signaling into rapid antigen uptake and processing while providing positive and negative feedback to BCR signaling.
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95
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Song W, Liu C, Upadhyaya A. The pivotal position of the actin cytoskeleton in the initiation and regulation of B cell receptor activation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:569-78. [PMID: 23886914 DOI: 10.1016/j.bbamem.2013.07.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 07/08/2013] [Accepted: 07/15/2013] [Indexed: 01/14/2023]
Abstract
The actin cytoskeleton is a dynamic cellular network known for its function in cell morphology and motility. Recent studies using high resolution and real time imaging techniques have revealed that actin plays a critical role in signal transduction, primarily by modulating the dynamics and organization of membrane-associated receptors and signaling molecules. This review summarizes what we have learned so far about a regulatory niche of the actin cytoskeleton in the signal transduction of the B cell receptor (BCR). The activation of the BCR is initiated and regulated by a close coordination between the dynamics of surface BCRs and the cortical actin network. The actin cytoskeleton is involved in regulating the signaling threshold of the BCR to antigenic stimulation, the kinetics and amplification of BCR signaling activities, and the timing and kinetics of signaling downregulation. Actin exerts its regulatory function by controlling the kinetics, magnitude, subcellular location, and nature of BCR clustering and BCR signaling complex formation at every stage of signaling. The cortical actin network is remodeled by initial detachment from the plasma membrane, disassembly and subsequent reassembly into new actin structures in response to antigenic stimulation. Signaling responsive actin regulators translate BCR stimulatory and inhibitory signals into a series of actin remodeling events, which enhance signaling activation and down-regulation by modulating the lateral mobility and spatial organization of surface BCR. The mechanistic understanding of actin-mediated signaling regulation in B cells will help us explore B cell-specific manipulations of the actin cytoskeleton as treatments for B cell-mediated autoimmunity and B cell cancer. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Wenxia Song
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA.
| | - Chaohong Liu
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Arpita Upadhyaya
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA
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96
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Hanada K. Co-evolution of sphingomyelin and the ceramide transport protein CERT. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:704-19. [PMID: 23845852 DOI: 10.1016/j.bbalip.2013.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 06/25/2013] [Accepted: 06/25/2013] [Indexed: 12/15/2022]
Abstract
Life creates many varieties of lipids. The choline-containing sphingophospholipid sphingomyelin (SM) exists ubiquitously or widely in vertebrates and lower animals, but is absent or rare in bacteria, fungi, protists, and plants. In the biosynthesis of SM, ceramide, which is synthesized in the endoplasmic reticulum, is transported to the Golgi region by the ceramide transport protein CERT, probably in a non-vesicular manner, and is then converted to SM by SM synthase, which catalyzes the reaction of phosphocholine transfer from phosphatidylcholine (PtdCho) to ceramide. Recent advances in genomics and lipidomics indicate that the phylogenetic occurrence of CERT and its orthologs is nearly parallel to that of SM. Based on the chemistry of lipids together with evolutionary aspects of SM and CERT, several concepts are here proposed. SM may serve as a chemically inert and robust, but non-covalently interactive lipid class at the outer leaflet of the plasma membrane. The functional domains and peptidic motifs of CERT are separated by exon units, suggesting an exon-shuffling mechanism for the generation of an ancestral CERT gene. CERT may have co-evolved with SM to bypass a competing metabolic reaction at the bifurcated point in the anabolism of ceramide. Human CERT is identical to the splicing variant of human Goodpasture antigen-binding protein (GPBP) annotated as an extracellular non-canonical serine/threonine protein kinase. The relationship between CERT and GPBP has also been discussed from an evolutionary aspect. Moreover, using an analogy of "compatible (or osmoprotective) solutes" that can accumulate to very high concentrations in the cytosol without denaturing proteins, choline phospholipids such as PtdCho and SM may act as compatible phospholipids in biomembranes. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.
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Affiliation(s)
- Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
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97
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Hovanyecz P, Guibert E, Pellegrino J, Rodriguez J, Sigot V. Extended cold storage of cultured hepatocytes impairs endocytic uptake during normothermic rewarming. Cryobiology 2013; 66:112-20. [DOI: 10.1016/j.cryobiol.2012.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/23/2012] [Accepted: 12/15/2012] [Indexed: 12/27/2022]
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98
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Westermarck J, Ivaska J, Corthals GL. Identification of protein interactions involved in cellular signaling. Mol Cell Proteomics 2013; 12:1752-63. [PMID: 23481661 DOI: 10.1074/mcp.r113.027771] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Protein-protein interactions drive biological processes. They are critical for all intra- and extracellular functions, and the technologies to analyze them are widely applied throughout the various fields of biological sciences. This study takes an in-depth view of some common principles of cellular regulation and provides a detailed account of approaches required to comprehensively map signaling protein-protein interactions in any particular cellular system or condition. We provide a critical review of the benefits and disadvantages of the yeast two-hybrid method and affinity purification coupled with mass spectrometric procedures for identification of signaling protein-protein interactions. In particular, we emphasize the quantitative and qualitative differences between tandem affinity and one-step purification (such as FLAG and Strep tag) methods. Although applicable to all types of interaction studies, a special section is devoted in this review to aspects that should be considered when attempting to identify signaling protein interactions that often are transient and weak by nature. Finally, we discuss shotgun and quantitative information that can be gleaned by MS-coupled methods for analysis of multiprotein complexes.
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Affiliation(s)
- Jukka Westermarck
- Centre for Biotechnology, University of Turku and Åbo Akademi, Turku, Finland
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99
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Shibata ACE, Chen LH, Nagai R, Ishidate F, Chadda R, Miwa Y, Naruse K, Shirai YM, Fujiwara TK, Kusumi A. Rac1 recruitment to the archipelago structure of the focal adhesion through the fluid membrane as revealed by single-molecule analysis. Cytoskeleton (Hoboken) 2013; 70:161-77. [PMID: 23341328 PMCID: PMC3627312 DOI: 10.1002/cm.21097] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/21/2012] [Accepted: 01/07/2013] [Indexed: 11/10/2022]
Abstract
The focal adhesion (FA) is an integrin-based structure built in/on the plasma membrane (PM), linking the extracellular matrix to the actin stress-fibers, working as cell migration scaffolds. Previously, we proposed the archipelago architecture of the FA, in which FA largely consists of fluid membrane, dotted with small islands accumulating FA proteins: membrane molecules enter the inter-island channels in the FA zone rather freely, and the integrins in the FA-protein islands rapidly exchanges with those in the bulk membrane. Here, we examined how Rac1, a small G-protein regulating FA formation, and its activators αPIX and βPIX, are recruited to the FA zones. PIX molecules are recruited from the cytoplasm to the FA zones directly. In contrast, majorities of Rac1 molecules first arrive from the cytoplasm on the general inner PM surface, and then enter the FA zones via lateral diffusion on the PM, which is possible due to rapid Rac1 diffusion even within the FA zones, slowed only by a factor of two to four compared with that outside. The constitutively-active Rac1 mutant exhibited temporary and all-time immobilizations in the FA zone, suggesting that upon PIX-induced Rac1 activation at the FA-protein islands, Rac1 tends to be immobilized at the FA-protein islands.
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Affiliation(s)
- Akihiro C E Shibata
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan
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100
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You C, Wilmes S, Richter CP, Beutel O, Liße D, Piehler J. Electrostatically controlled quantum dot monofunctionalization for interrogating the dynamics of protein complexes in living cells. ACS Chem Biol 2013. [PMID: 23186299 DOI: 10.1021/cb300543t] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Quantum dots (QD) are powerful labels for probing diffusion and interaction dynamics of proteins on the single molecule level in living cells. Protein cross-linking due to multifunctional QD strongly affects these properties. This becomes particularly critical when labeling interaction partners with QDs for interrogating the dynamics of complexes. We have here implemented a generic method for QD monofunctionalization based on electrostatic repulsion of a highly negatively charged peptide carrier. On the basis of this method, monobiotinylated QDs were prepared with high yield as confirmed by single molecule assays. These QDs were successfully employed for probing the assembly and diffusion dynamics of binary and ternary cytokine-receptor complexes on the surface of living cells by dual color single QD tracking. Thus, sequential and dynamic recruitment of the type I interferon receptor subunits by the ligand could be observed.
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Affiliation(s)
- Changjiang You
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
| | - Stephan Wilmes
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
| | - Christian P. Richter
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
| | - Oliver Beutel
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
| | - Domenik Liße
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
| | - Jacob Piehler
- Division
of Biophysics, Department of Biology, University of Osnabrück, 49076 Osnabrück,
Germany
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