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Miao Y, Guo X, Zhu K, Zhao W. Biomolecular condensates tunes immune signaling at the Host-Pathogen interface. CURRENT OPINION IN PLANT BIOLOGY 2023; 74:102374. [PMID: 37148673 DOI: 10.1016/j.pbi.2023.102374] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 04/06/2023] [Accepted: 04/07/2023] [Indexed: 05/08/2023]
Abstract
Membraneless organelles participate in diverse spatiotemporal regulation of cellular signal transduction by recruiting necessary signaling factors. During host-pathogen interactions, the plasma membrane (PM) at the interface between the plant and microbes serves as a central platform for forming multicomponent immune signaling hubs. The macromolecular condensation of the immune complex and regulators is important in regulating immune signaling outputs regarding strength, timing, and crosstalk between signaling pathways. This review discusses mechanisms that regulate specific and crosstalk of plant immune signal transduction pathways through macromolecular assembly and condensation.
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Affiliation(s)
- Yansong Miao
- School of Biological Sciences, Nanyang Technological University, 637551, Singapore; Institute for Digital Molecular Analytics and Science, Nanyang Technological University, 636921, Singapore.
| | - Xiangfu Guo
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 70 Nanyang Drive, 637457, Singapore
| | - Kexin Zhu
- School of Biological Sciences, Nanyang Technological University, 637551, Singapore
| | - Wenting Zhao
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 70 Nanyang Drive, 637457, Singapore; Institute for Digital Molecular Analytics and Science, Nanyang Technological University, 636921, Singapore
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2
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Jangid AK, Kim S, Kim K. Polymeric biomaterial-inspired cell surface modulation for the development of novel anticancer therapeutics. Biomater Res 2023; 27:59. [PMID: 37344853 DOI: 10.1186/s40824-023-00404-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 06/01/2023] [Indexed: 06/23/2023] Open
Abstract
Immune cell-based therapies are a rapidly emerging class of new medicines that directly treat and prevent targeted cancer. However multiple biological barriers impede the activity of live immune cells, and therefore necessitate the use of surface-modified immune cells for cancer prevention. Synthetic and/or natural biomaterials represent the leading approach for immune cell surface modulation. Different types of biomaterials can be applied to cell surface membranes through hydrophobic insertion, layer-by-layer attachment, and covalent conjugations to acquire surface modification in mammalian cells. These biomaterials generate reciprocity to enable cell-cell interactions. In this review, we highlight the different biomaterials (lipidic and polymeric)-based advanced applications for cell-surface modulation, a few cell recognition moieties, and how their interplay in cell-cell interaction. We discuss the cancer-killing efficacy of NK cells, followed by their surface engineering for cancer treatment. Ultimately, this review connects biomaterials and biologically active NK cells that play key roles in cancer immunotherapy applications.
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Affiliation(s)
- Ashok Kumar Jangid
- Department of Chemical and Biochemical Engineering, College of Engineering, Dongguk University, Seoul, South Korea
| | - Sungjun Kim
- Department of Chemical and Biochemical Engineering, College of Engineering, Dongguk University, Seoul, South Korea
| | - Kyobum Kim
- Department of Chemical and Biochemical Engineering, College of Engineering, Dongguk University, Seoul, South Korea.
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3
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Bagheri Y, Ali AA, Keshri P, Chambers J, Gershenson A, You M. Imaging Membrane Order and Dynamic Interactions in Living Cells with a DNA Zipper Probe. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202112033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yousef Bagheri
- Department of Chemistry University of Massachusetts Amherst MA 01003 USA
| | - Ahsan Ausaf Ali
- Department of Chemistry University of Massachusetts Amherst MA 01003 USA
| | - Puspam Keshri
- Department of Chemistry University of Massachusetts Amherst MA 01003 USA
| | - James Chambers
- Institute for Applied Life Sciences University of Massachusetts Amherst MA 01003 USA
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology University of Massachusetts Amherst MA 01003 USA
| | - Mingxu You
- Department of Chemistry University of Massachusetts Amherst MA 01003 USA
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4
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Bagheri Y, Ali AA, Keshri P, Chambers J, Gershenson A, You M. Imaging Membrane Order and Dynamic Interactions in Living Cells with a DNA Zipper Probe. Angew Chem Int Ed Engl 2022; 61:e202112033. [PMID: 34767659 PMCID: PMC8792286 DOI: 10.1002/anie.202112033] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 10/19/2021] [Indexed: 02/03/2023]
Abstract
The cell membrane is a dynamic and heterogeneous structure composed of distinct sub-compartments. Within these compartments, preferential interactions occur among various lipids and proteins. Currently, it is still challenging to image these short-lived membrane complexes, especially in living cells. In this work, we present a DNA-based probe, termed "DNA Zipper", which allows the membrane order and pattern of transient interactions to be imaged in living cells using standard fluorescence microscopes. By fine-tuning the length and binding affinity of DNA duplex, these probes can precisely extend the duration of membrane lipid interactions via dynamic DNA hybridization. The correlation between membrane order and the activation of T-cell receptor signaling has also been studied. These programmable DNA probes function after a brief cell incubation, which can be easily adapted to study lipid interactions and membrane order during different membrane signaling events.
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Affiliation(s)
- Yousef Bagheri
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003 (USA)
| | - Ahsan Ausaf Ali
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003 (USA)
| | - Puspam Keshri
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003 (USA)
| | - James Chambers
- Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA 01003 (USA)
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, MA 01003 (USA)
| | - Mingxu You
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003 (USA)
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5
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Regulation of local GTP availability controls RAC1 activity and cell invasion. Nat Commun 2021; 12:6091. [PMID: 34667203 PMCID: PMC8526568 DOI: 10.1038/s41467-021-26324-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 09/27/2021] [Indexed: 12/04/2022] Open
Abstract
Physiological changes in GTP levels in live cells have never been considered a regulatory step of RAC1 activation because intracellular GTP concentration (determined by chromatography or mass spectrometry) was shown to be substantially higher than the in vitro RAC1 GTP dissociation constant (RAC1-GTP Kd). Here, by combining genetically encoded GTP biosensors and a RAC1 activity biosensor, we demonstrated that GTP levels fluctuating around RAC1-GTP Kd correlated with changes in RAC1 activity in live cells. Furthermore, RAC1 co-localized in protrusions of invading cells with several guanylate metabolism enzymes, including rate-limiting inosine monophosphate dehydrogenase 2 (IMPDH2), which was partially due to direct RAC1-IMPDH2 interaction. Substitution of endogenous IMPDH2 with IMPDH2 mutants incapable of binding RAC1 did not affect total intracellular GTP levels but suppressed RAC1 activity. Targeting IMPDH2 away from the plasma membrane did not alter total intracellular GTP pools but decreased GTP levels in cell protrusions, RAC1 activity, and cell invasion. These data provide a mechanism of regulation of RAC1 activity by local GTP pools in live cells. Changes in intracellular GTP levels are not considered as a regulatory event in RAC1 activation in live cells since total GTP levels are substantially higher than the RAC1 GTP dissociation constant determined in vitro. Here, the authors demonstrate that the availability of free GTP in live cells controls the activity of RAC1 and cell invasion.
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6
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Laursen T, Lam HYM, Sørensen KK, Tian P, Hansen CC, Groves JT, Jensen KJ, Christensen SM. Membrane anchoring facilitates colocalization of enzymes in plant cytochrome P450 redox systems. Commun Biol 2021; 4:1057. [PMID: 34504298 PMCID: PMC8429664 DOI: 10.1038/s42003-021-02604-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 08/25/2021] [Indexed: 01/03/2023] Open
Abstract
Plant metabolism depends on cascade reactions mediated by dynamic enzyme assemblies known as metabolons. In this context, the cytochrome P450 (P450) superfamily catalyze key reactions underpinning the unique diversity of bioactive compounds. In contrast to their soluble bacterial counterparts, eukaryotic P450s are anchored to the endoplasmic reticulum membrane and serve as metabolon nucleation sites. Hence, membrane anchoring appears to play a pivotal role in the evolution of complex biosynthetic pathways. Here, a model membrane assay enabled characterization of membrane anchor dynamics by single molecule microscopy. As a model system, we reconstituted the membrane anchor of cytochrome P450 oxidoreductase (POR), the ubiquitous electron donor to all microsomal P450s. The transmembrane segment in the membrane anchor of POR is relatively conserved, corroborating its functional importance. We observe dynamic colocalization of the POR anchors in our assay suggesting that membrane anchoring might promote intermolecular interactions and in this way impact assembly of metabolic multienzyme complexes.
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Affiliation(s)
- Tomas Laursen
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | - Cecilie Cetti Hansen
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jay T Groves
- Department of Chemistry, University of California, Berkeley, CA, USA
| | | | - Sune M Christensen
- Department of Chemistry, University of California, Berkeley, CA, USA. .,Enzyme Research, Lyngby, Denmark.
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7
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Lee H, Kim N, Rheem HB, Kim BJ, Park JH, Choi IS. A Decade of Advances in Single-Cell Nanocoating for Mammalian Cells. Adv Healthc Mater 2021; 10:e2100347. [PMID: 33890422 DOI: 10.1002/adhm.202100347] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/06/2021] [Indexed: 12/14/2022]
Abstract
Strategic advances in the single-cell nanocoating of mammalian cells have noticeably been made during the last decade, and many potential applications have been demonstrated. Various cell-coating strategies have been proposed via adaptation of reported methods in the surface sciences and/or materials identification that ensure the sustainability of labile mammalian cells during chemical manipulation. Here an overview of the methodological development and potential applications to the healthcare sector in the nanocoating of mammalian cells made during the last decade is provided. The materials used for the nanocoating are categorized into polymers, hydrogels, polyphenolic compounds, nanoparticles, and minerals, and the corresponding strategies are described under the given set of materials. It also suggests, as a future direction, the creation of the cytospace system that is hierarchically composed of the physically separated but mutually interacting cellular hybrids.
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Affiliation(s)
- Hojae Lee
- Center for Cell‐Encapsulation Research Department of Chemistry KAIST Daejeon 34141 Korea
| | - Nayoung Kim
- Center for Cell‐Encapsulation Research Department of Chemistry KAIST Daejeon 34141 Korea
| | - Hyeong Bin Rheem
- Center for Cell‐Encapsulation Research Department of Chemistry KAIST Daejeon 34141 Korea
| | - Beom Jin Kim
- Department of Chemistry University of Ulsan Ulsan 44610 Korea
| | - Ji Hun Park
- Department of Science Education Ewha Womans University Seoul 03760 Korea
| | - Insung S. Choi
- Center for Cell‐Encapsulation Research Department of Chemistry KAIST Daejeon 34141 Korea
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8
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Sun G, Guillon E, Holley SA. Integrin intra-heterodimer affinity inversely correlates with integrin activatability. Cell Rep 2021; 35:109230. [PMID: 34107244 PMCID: PMC8227800 DOI: 10.1016/j.celrep.2021.109230] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 03/13/2021] [Accepted: 05/17/2021] [Indexed: 11/21/2022] Open
Abstract
Integrins are heterodimeric cell surface receptors composed of an α and β subunit that mediate cell adhesion to extracellular matrix proteins such as fibronectin. We previously studied integrin α5β1 activation during zebrafish somitogenesis, and in the present study, we characterize the integrin αV fibronectin receptors. Integrins are activated via a conformational change, and we perform single-molecule biophysical measurements of both integrin activation via fluorescence resonance energy transfer (FRET)-fluorescence lifetime imaging microscopy (FLIM) and integrin intra-heterodimer stability via fluorescence cross-correlation spectroscopy (FCCS) in living embryos. We find that integrin heterodimers that exhibit robust cell surface expression, including αVβ3, αVβ5, and αVβ6, are never activated in this in vivo context, even in the presence of fibronectin matrix. In contrast, activatable integrins, such as integrin αVβ1, and alleles of αVβ3, αVβ5, αVβ6 that are biased to the active conformation exhibit poor cell surface expression and have a higher intra-heterodimer dissociation constant (KD). These observations suggest that a weak integrin intra-heterodimer affinity decreases integrin cell surface stability and increases integrin activatability.
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Affiliation(s)
- Guangyu Sun
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA
| | - Emilie Guillon
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA
| | - Scott A Holley
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA.
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9
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Bagheri Y, Ali AA, You M. Current Methods for Detecting Cell Membrane Transient Interactions. Front Chem 2020; 8:603259. [PMID: 33365301 PMCID: PMC7750205 DOI: 10.3389/fchem.2020.603259] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Accepted: 10/16/2020] [Indexed: 12/28/2022] Open
Abstract
Short-lived cell membrane complexes play a key role in regulating cell signaling and communication. Many of these complexes are formed based on low-affinity and transient interactions among various lipids and proteins. New techniques have emerged to study these previously overlooked membrane transient interactions. Exciting functions of these transient interactions have been discovered in cellular events such as immune signaling, host-pathogen interactions, and diseases such as cancer. In this review, we have summarized current experimental methods that allow us to detect and analyze short-lived cell membrane protein-protein, lipid-protein, and lipid-lipid interactions. These methods can provide useful information about the strengths, kinetics, and/or spatial patterns of membrane transient interactions. However, each method also has its own limitations. We hope this review can be used as a guideline to help the audience to choose proper approaches for studying membrane transient interactions in different membrane trafficking and cell signaling events.
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Affiliation(s)
| | | | - Mingxu You
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
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10
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Ma Y, Lim YJ, Benda A, Lou J, Goyette J, Gaus K. Clustering of the ζ-Chain Can Initiate T Cell Receptor Signaling. Int J Mol Sci 2020; 21:ijms21103498. [PMID: 32429097 PMCID: PMC7279048 DOI: 10.3390/ijms21103498] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/11/2020] [Accepted: 05/13/2020] [Indexed: 11/16/2022] Open
Abstract
T cell activation is initiated when ligand binding to the T cell receptor (TCR) triggers intracellular phosphorylation of the TCR-CD3 complex. However, it remains unknown how biophysical properties of TCR engagement result in biochemical phosphorylation events. Here, we constructed an optogenetic tool that induces spatial clustering of ζ-chain in a light controlled manner. We showed that spatial clustering of the ζ-chain intracellular tail alone was sufficient to initialize T cell triggering including phosphorylation of ζ-chain, Zap70, PLCγ, ERK and initiated Ca2+ flux. In reconstituted COS-7 cells, only Lck expression was required to initiate ζ-chain phosphorylation upon ζ-chain clustering, which leads to the recruitment of tandem SH2 domain of Zap70 from cell cytosol to the newly formed ζ-chain clusters at the plasma membrane. Taken together, our data demonstrated the biophysical relevance of receptor clustering in TCR signaling.
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Affiliation(s)
- Yuanqing Ma
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, The University of New South Wales, 2052 Sydney, Australia; (J.L.); (J.G.)
- ARC Centre of Excellence in Advanced Molecular Imaging, The University of New South Wales, 2052 Sydney, Australia
- Correspondence: (Y.M.); (K.G.)
| | - Yean J. Lim
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, 2601 Canberra, Australia;
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, 31 North Road, 2601 Canberra, Australia
| | - Aleš Benda
- IMCF at BIOCEV, Faculty of Science, Charles University, Průmyslová 595, 25250 Vestec, Czech Republic;
| | - Jieqiong Lou
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, The University of New South Wales, 2052 Sydney, Australia; (J.L.); (J.G.)
- ARC Centre of Excellence in Advanced Molecular Imaging, The University of New South Wales, 2052 Sydney, Australia
- School of Physics, University of Melbourne, Melbourne, VIC 3010, Australia
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Jesse Goyette
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, The University of New South Wales, 2052 Sydney, Australia; (J.L.); (J.G.)
- ARC Centre of Excellence in Advanced Molecular Imaging, The University of New South Wales, 2052 Sydney, Australia
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, The University of New South Wales, 2052 Sydney, Australia; (J.L.); (J.G.)
- ARC Centre of Excellence in Advanced Molecular Imaging, The University of New South Wales, 2052 Sydney, Australia
- Correspondence: (Y.M.); (K.G.)
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11
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Li L, Dwivedi M, Patra S, Erwin N, Möbitz S, Winter R. Probing Colocalization of N-Ras and K-Ras4B Lipoproteins in Model Biomembranes. Chembiochem 2019; 20:1190-1195. [PMID: 30604476 DOI: 10.1002/cbic.201800776] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Indexed: 12/28/2022]
Abstract
Signaling of N-Ras and K-Ras4B proteins depends strongly on their correct localization in the cell membrane. In vivo studies suggest that intermolecular interactions foster the self-association of both N-Ras and K-Ras4B and the formation of nanoclusters in the cell membrane. As sites for effector binding, nanocluster formation is thought to be essential for effective signal transmission of both N-Ras and K-Ras4B. To shed more light on the spatial arrangement and mechanism underlying the proposed cross-talk between spatially segregated Ras proteins, the simultaneous localization of N-Ras and K-Ras4B and their effect on the lateral organization of a heterogeneous model biomembrane has been studied by using AFM and FRET methodology. It is shown that, owing to the different natures of their membrane anchor systems, N-Ras and K-Ras4B not only avoid assembly in bulk solution and do not colocalize, but rather form individual nanoclusters that diffuse independently in the fluid membrane plane.
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Affiliation(s)
- Lei Li
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany.,International Max Planck Research School (IMPRS), in Chemical and Molecular Biology, Otto-Hahn-Strasse 11, 44227, Dortmund, Germany
| | - Mridula Dwivedi
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
| | - Satyajit Patra
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
| | - Nelli Erwin
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany.,International Max Planck Research School (IMPRS), in Chemical and Molecular Biology, Otto-Hahn-Strasse 11, 44227, Dortmund, Germany
| | - Simone Möbitz
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
| | - Roland Winter
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
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12
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Kaliszewski MJ, Shi X, Hou Y, Lingerak R, Kim S, Mallory P, Smith AW. Quantifying membrane protein oligomerization with fluorescence cross-correlation spectroscopy. Methods 2018; 140-141:40-51. [PMID: 29448037 DOI: 10.1016/j.ymeth.2018.02.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/17/2017] [Accepted: 02/07/2018] [Indexed: 01/27/2023] Open
Abstract
Fluorescence cross-correlation spectroscopy (FCCS) is an advanced fluorescence technique that can quantify protein-protein interactions in vivo. Due to the dynamic, heterogeneous nature of the membrane, special considerations must be made to interpret FCCS data accurately. In this study, we describe a method to quantify the oligomerization of membrane proteins tagged with two commonly used fluorescent probes, mCherry (mCH) and enhanced green (eGFP) fluorescent proteins. A mathematical model is described that relates the relative cross-correlation value (fc) to the degree of oligomerization. This treatment accounts for mismatch in the confocal volumes, combinatoric effects of using two fluorescent probes, and the presence of non-fluorescent probes. Using this model, we calculate a ladder of fc values which can be used to determine the oligomer state of membrane proteins from live-cell experimental data. Additionally, a probabilistic mathematical simulation is described to resolve the affinity of different dimeric and oligomeric protein controls.
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Affiliation(s)
| | - Xiaojun Shi
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Yixuan Hou
- Food Animal Health Research Program, Ohio Agriculture Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Ryan Lingerak
- Department of Biology, University of Akron, Akron, OH 44325, USA
| | - Soyeon Kim
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Paul Mallory
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Adam W Smith
- Department of Chemistry, University of Akron, Akron, OH 44325, USA.
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13
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Edler E, Schulze E, Stein M. Membrane localization and dynamics of geranylgeranylated Rab5 hypervariable region. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1335-1349. [PMID: 28455099 DOI: 10.1016/j.bbamem.2017.04.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/18/2017] [Accepted: 04/23/2017] [Indexed: 12/11/2022]
Abstract
The small GTPase Rab5 is a key regulator of endosomal trafficking processes and a marker for the early endosome. The C-terminal hypervariable region (HVR) of Rab5 is post-translationally modified at residues Cys212 and Cys213 to accommodate two geranylgeranyl anchors (C20 carbon chain length) in order to associate Rab5 with the membrane. The structural role of the HVR regarding protein-early endosome membrane recruitment is not resolved due to its high degree of flexibility and lack of crystallographic information. Here, full-atomistic and coarse-grained molecular dynamics simulations of the truncated Rab5 HVR206-215 in three model membranes of increasing complexity (pure phospholipid bilayer, ternary membrane with cholesterol, six-component early endosome) were performed. Specific electrostatic interactions between the HVR206-215 Arg209 residue and the phosphate group of the inositol ring of PI(3)P were detected. This shows that PI(3)P acts as a first contact site of protein recruitment to the early endosome. The free energy change of HVR206-215 extraction from the bilayer was largest for the physiological negatively charged membrane. 5μs coarse-grained simulations revealed an active recruitment of PI(3)P to the HVR206-215 supporting the formation of Rab5- and PI(3)P enriched signaling platforms.
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Affiliation(s)
- Eileen Edler
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
| | - Eric Schulze
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany; International Max Planck Research School (IMPRS) for Advanced Methods in Process and Systems Engineering, Magdeburg, Germany
| | - Matthias Stein
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany.
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14
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Lou HY, Zhao W, Hanson L, Zeng C, Cui Y, Cui B. Dual-Functional Lipid Coating for the Nanopillar-Based Capture of Circulating Tumor Cells with High Purity and Efficiency. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:1097-1104. [PMID: 28059522 PMCID: PMC8491572 DOI: 10.1021/acs.langmuir.6b03903] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Clinical studies of circulating tumor cells (CTC) have stringent demands for high capture purity and high capture efficiency. Nanostructured surfaces have been shown to significantly increase the capture efficiency yet suffer from low capture purity. Here we introduce a dual-functional lipid coating on nanostructured surfaces. The lipid coating serves both as an effective passivation layer that helps prevent nonspecific cell adhesion and as a functionalized layer for antibody-based specific cell capture. In addition, the fluidity of lipid bilayers enables antibody clustering that enhances the cell-surface interaction for efficient cell capture. As a result, the lipid-coating method helps promote both the capture efficiency and capture purity of nanostructure-based CTC capture.
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Affiliation(s)
- Hsin-Ya Lou
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Wenting Zhao
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Lindsey Hanson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Connie Zeng
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yi Cui
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Bianxiao Cui
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Corresponding Author:
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15
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Huang S, Lim SY, Gupta A, Bag N, Wohland T. Plasma membrane organization and dynamics is probe and cell line dependent. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:1483-1492. [PMID: 27998689 DOI: 10.1016/j.bbamem.2016.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/03/2016] [Accepted: 12/08/2016] [Indexed: 01/01/2023]
Abstract
The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an active role and regulates receptor distribution and function by its composition and the interaction of its lipid components with embedded and surrounding proteins. Furthermore, it is not a homogenous fluid but contains lipid and protein domains of various sizes and characteristic lifetimes which are important in regulating receptor function and signaling. The precise lateral organization of the plasma membrane, the differences between the inner and outer leaflet, and the influence of the cytoskeleton are still debated. Furthermore, there is a lack of comparisons of the organization and dynamics of the plasma membrane of different cell types. Therefore, we used four different specific membrane markers to test the lateral organization, the differences between the inner and outer membrane leaflet, and the influence of the cytoskeleton of up to five different cell lines, including Chinese hamster ovary (CHO-K1), Human cervical carcinoma (HeLa), neuroblastoma (SH-SY5Y), fibroblast (WI-38) and rat basophilic leukemia (RBL-2H3) cells by Imaging Total Internal Reflection (ITIR)-Fluorescence Correlation Spectroscopy (FCS). We measure diffusion in the temperature range of 298-310K to measure the Arrhenius activation energy (EArr) of diffusion and apply the FCS diffusion law to obtain information on the spatial organization of the probe molecules on the various cell membranes. Our results show clear differences of the FCS diffusion law and EArr for the different probes in dependence of their localization. These differences are similar in the outer and inner leaflet of the membrane. However, these values can differ significantly between different cell lines raising the question how molecular plasma membrane events measured in different cell lines can be compared. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
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Affiliation(s)
- Shuangru Huang
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore
| | - Shi Ying Lim
- NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore
| | - Anjali Gupta
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore
| | - Nirmalya Bag
- NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore.
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16
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Marita M, Wang Y, Kaliszewski MJ, Skinner KC, Comar WD, Shi X, Dasari P, Zhang X, Smith AW. Class A Plexins Are Organized as Preformed Inactive Dimers on the Cell Surface. Biophys J 2016; 109:1937-45. [PMID: 26536270 DOI: 10.1016/j.bpj.2015.04.043] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 04/10/2015] [Accepted: 04/27/2015] [Indexed: 01/08/2023] Open
Abstract
Plexins are single-pass transmembrane receptors that bind the axon guidance molecules semaphorins. Single-pass transmembrane proteins are an important class of receptors that display a wide variety of activation mechanisms, often involving ligand-dependent dimerization or conformational changes. Resolving the activation mechanism and dimerization state of these receptors is extremely challenging, especially in a live-cell environment. Here, we report on the dimerization state of PlexinA4 and its response to activation by semaphorin binding. Semaphorins are dimeric molecules that activate plexin by binding two copies of plexin simultaneously and inducing formation of a specific active dimer of plexin. An open question is whether there are preexisting plexin dimers that could act as autoinhibitory complexes. We address these questions with pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS is a two-color fluorescence microscopy method that is directly sensitive to protein dimerization in a live-cell environment. With PIE-FCCS, we show that inactive PlexinA4 is dimerized in the live-cell plasma membrane. By comparing the cross correlation of full-length PlexinA4 to control proteins and plexin mutants, we show that dimerization of inactive PlexinA4 requires the Sema domain, but not the cytoplasmic domain. Ligand stimulation with Sema6A does not change the degree of cross correlation, indicating that plexin activation does not lead to higher-order oligomerization. Together, the results suggest that semaphorin activates plexin by disrupting an inhibitory plexin dimer and inducing the active dimer.
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Affiliation(s)
- Morgan Marita
- Department of Chemistry, University of Akron, Akron, Ohio
| | - Yuxiao Wang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California
| | | | | | | | - Xiaojun Shi
- Department of Chemistry, University of Akron, Akron, Ohio
| | - Pranathi Dasari
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Xuewu Zhang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Adam W Smith
- Department of Chemistry, University of Akron, Akron, Ohio.
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17
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Sensitive and Specific Biomimetic Lipid Coated Microfluidics to Isolate Viable Circulating Tumor Cells and Microemboli for Cancer Detection. PLoS One 2016; 11:e0149633. [PMID: 26938471 PMCID: PMC4777486 DOI: 10.1371/journal.pone.0149633] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 02/02/2016] [Indexed: 12/14/2022] Open
Abstract
Here we presented a simple and effective membrane mimetic microfluidic device with antibody conjugated supported lipid bilayer (SLB) "smart coating" to capture viable circulating tumor cells (CTCs) and circulating tumor microemboli (CTM) directly from whole blood of all stage clinical cancer patients. The non-covalently bound SLB was able to promote dynamic clustering of lipid-tethered antibodies to CTC antigens and minimized non-specific blood cells retention through its non-fouling nature. A gentle flow further flushed away loosely-bound blood cells to achieve high purity of CTCs, and a stream of air foam injected disintegrate the SLB assemblies to release intact and viable CTCs from the chip. Human blood spiked cancer cell line test showed the ~95% overall efficiency to recover both CTCs and CTMs. Live/dead assay showed that at least 86% of recovered cells maintain viability. By using 2 mL of peripheral blood, the CTCs and CTMs counts of 63 healthy and colorectal cancer donors were positively correlated with the cancer progression. In summary, a simple and effective strategy utilizing biomimetic principle was developed to retrieve viable CTCs for enumeration, molecular analysis, as well as ex vivo culture over weeks. Due to the high sensitivity and specificity, it is the first time to show the high detection rates and quantity of CTCs in non-metastatic cancer patients. This work offers the values in both early cancer detection and prognosis of CTC and provides an accurate non-invasive strategy for routine clinical investigation on CTCs.
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18
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Smith AW, Huang HH, Endres NF, Rhodes C, Groves JT. Dynamic Organization of Myristoylated Src in the Live Cell Plasma Membrane. J Phys Chem B 2016; 120:867-76. [DOI: 10.1021/acs.jpcb.5b08887] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Adam W. Smith
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Department
of Chemistry, University of Akron, Akron, Ohio 44303, United States
| | - Hector H. Huang
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Nicholas F. Endres
- Howard
Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Christopher Rhodes
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Jay T. Groves
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
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19
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Homogeneous immunoassay for the cancer marker alpha-fetoprotein using single wavelength excitation fluorescence cross-correlation spectroscopy and CdSe/ZnS quantum dots and fluorescent dyes as labels. Mikrochim Acta 2015. [DOI: 10.1007/s00604-015-1694-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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20
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Abstract
The fundamental mechanisms of protein and lipid organization at the plasma membrane have continued to engage researchers for decades. Among proposed models, one idea has been particularly successful which assumes that sterol-dependent nanoscopic phases of different lipid chain order compartmentalize proteins, thereby modulating protein functionality. This model of membrane rafts has sustainably sparked the fields of membrane biophysics and biology, and shifted membrane lipids into the spotlight of research; by now, rafts have become an integral part of our terminology to describe a variety of cell biological processes. But is the evidence clear enough to continue supporting a theoretical concept which has resisted direct proof by observation for nearly twenty years? In this essay, we revisit findings that gave rise to and substantiated the raft hypothesis, discuss its impact on recent studies, and present alternative mechanisms to account for plasma membrane heterogeneity.
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Affiliation(s)
- Eva Sevcsik
- Institute of Applied Physics, Vienna University of Technology, Vienna, Austria
| | - Gerhard J Schütz
- Institute of Applied Physics, Vienna University of Technology, Vienna, Austria
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21
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Smith AW. Detection of rhodopsin dimerization in situ by PIE-FCCS, a time-resolved fluorescence spectroscopy. Methods Mol Biol 2015; 1271:205-19. [PMID: 25697526 DOI: 10.1007/978-1-4939-2330-4_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Rhodopsin self-associates in the plasma membrane. At low concentrations, the interactions are consistent with a monomer-dimer equilibrium (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). At high concentrations in native tissue, higher-order clusters have been observed (Fotiadis et al., Nature 421:127-128, 2003). The physiological role of rhodopsin dimerization is still being investigated, but it is clear that a quantitative assessment is essential to determining the function of rhodopsin clusters in vision. To quantify rhodopsin interactions, I will outline the theory and methodology of a specialized time-resolved fluorescence spectroscopy for measuring membrane protein-protein interactions called pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). The strength of this technique is its ability to quantify rhodopsin interactions in situ (i.e., a live cell plasma membrane). There are two reasons for restricting the scope to live cell membranes. First, the compositional heterogeneity of the plasma membrane creates a complex milieu with thousands of lipid, protein, and carbohydrate species. This makes it difficult to infer quaternary interactions from detergent solubilized samples or construct a model phospholipid bilayer that recapitulates all of the interactions present in native membranes. Second, organizational structure and dynamics is a key feature of the plasma membrane, and fixation techniques like formaldehyde cross-linking and vitrification will modulate the interactions. PIE-FCCS is based on two-color fluorescence imaging with time-correlated single-photon counting (TCSPC) (Becker et al., Rev Sci Instrum 70:1835-1841, 1999). By time-tagging every detected photon, the data can be analyzed as a fluorescence intensity distribution, fluorescence lifetime histogram, or fluorescence (cross-)correlation spectra (FCS/FCCS) (Becker, Advanced time-correlated single-photon counting techniques, Springer, Berlin, 2005). These analysis tools can then be used to quantify protein concentration, mobility, clustering, and Förster resonance energy transfer (FRET). In this paper I will focus on PIE-FCCS, which interleaves two wavelength excitation events in time so that the effects of spectral cross-talk and FRET can be isolated. In this way it is possible to characterize monomer-dimer-oligomer equilibria with high accuracy (Müller et al., Biophys J 89:3508-3522, 2005). Currently, PIE-FCCS requires a customized equipment configuration that will be described below. There is an excellent protocol that outlines traditional FCCS on a commercially available instrument (Bacia and Schwille, Nat Protoc 2:2842-2856, 2007). The PIE-FCCS approach is a relatively recent advance in FCCS that has been used in live cell assays to quantify lipid-anchored protein clustering (Triffo et al., J Am Chem Soc 134:10833-10842, 2012), epidermal growth factor receptor dimerization (Endres et al., Cell 152:543-556, 2013), and recently the dimerization of opsin (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). This paper will outline the theory and instrumentation requirements for PIE-FCCS, as well as the data collection and analysis process.
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Affiliation(s)
- Adam W Smith
- Department of Chemistry, University of Akron, 190 Buchtel Common, Akron, OH, 44325-3601, USA,
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22
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Abstract
The local structure and composition of the outer membrane of an animal cell are important factors in the control of many membrane processes and mechanisms. These include signaling, sorting, and exo- and endocytic processes that are occurring all the time in a living cell. Paradoxically, not only are the local structure and composition of the membrane matters of much debate and discussion, the mechanisms that govern its genesis remain highly controversial. Here, we discuss a swathe of new technological advances that may be applied to understand the local structure and composition of the membrane of a living cell from the molecular scale to the scale of the whole membrane.
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Affiliation(s)
- Thomas S van Zanten
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore, 560065, India
| | - Satyajit Mayor
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore, 560065, India
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23
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Saha S, Lee IH, Polley A, Groves JT, Rao M, Mayor S. Diffusion of GPI-anchored proteins is influenced by the activity of dynamic cortical actin. Mol Biol Cell 2015; 26:4033-45. [PMID: 26378258 PMCID: PMC4710234 DOI: 10.1091/mbc.e15-06-0397] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/07/2015] [Indexed: 12/22/2022] Open
Abstract
Membrane proteins that couple to cortical actin show temperature-independent diffusion. The loss of this coupling and perturbation of cortical actomyosin dynamics render the diffusion temperature dependent. The findings suggest that active fluctuations arising from dynamic actin filaments at the cortex can drive diffusion on the cell membrane. Molecular diffusion at the surface of living cells is believed to be predominantly driven by thermal kicks. However, there is growing evidence that certain cell surface molecules are driven by the fluctuating dynamics of cortical cytoskeleton. Using fluorescence correlation spectroscopy, we measure the diffusion coefficient of a variety of cell surface molecules over a temperature range of 24–37°C. Exogenously incorporated fluorescent lipids with short acyl chains exhibit the expected increase of diffusion coefficient over this temperature range. In contrast, we find that GPI-anchored proteins exhibit temperature-independent diffusion over this range and revert to temperature-dependent diffusion on cell membrane blebs, in cells depleted of cholesterol, and upon acute perturbation of actin dynamics and myosin activity. A model transmembrane protein with a cytosolic actin-binding domain also exhibits the temperature-independent behavior, directly implicating the role of cortical actin. We show that diffusion of GPI-anchored proteins also becomes temperature dependent when the filamentous dynamic actin nucleator formin is inhibited. However, changes in cortical actin mesh size or perturbation of branched actin nucleator Arp2/3 do not affect this behavior. Thus cell surface diffusion of GPI-anchored proteins and transmembrane proteins that associate with actin is driven by active fluctuations of dynamic cortical actin filaments in addition to thermal fluctuations, consistent with expectations from an “active actin-membrane composite” cell surface.
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Affiliation(s)
- Suvrajit Saha
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore 560065, India
| | - Il-Hyung Lee
- Department of Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720
| | | | - Jay T Groves
- Department of Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720
| | - Madan Rao
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore 560065, India Raman Research Institute, Bangalore 560080, India
| | - Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore 560065, India Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
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24
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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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25
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Cross-Scale Integrin Regulation Organizes ECM and Tissue Topology. Dev Cell 2015; 34:33-44. [PMID: 26096733 DOI: 10.1016/j.devcel.2015.05.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 03/23/2015] [Accepted: 04/29/2015] [Indexed: 11/23/2022]
Abstract
The diverse morphologies of animal tissues are underlain by different configurations of adherent cells and extracellular matrix (ECM). Here, we elucidate a cross-scale mechanism for tissue assembly and ECM remodeling involving Cadherin 2, the ECM protein Fibronectin, and its receptor Integrin α5. Fluorescence cross-correlation spectroscopy within the zebrafish paraxial mesoderm mesenchyme reveals a physical association between Integrin α5 on adjacent cell membranes. This Integrin-Integrin complex correlates with conformationally inactive Integrin. Cadherin 2 stabilizes both the Integrin association and inactive Integrin conformation. Thus, Integrin repression within the adherent mesenchymal interior of the tissue biases Fibronectin fibrillogenesis to the tissue surface lacking cell-cell adhesions. Along nascent somite boundaries, Cadherin 2 levels decrease, becoming anti-correlated with levels of Integrin α5. Simultaneously, Integrin α5 clusters and adopts the active conformation and then commences ECM assembly. This cross-scale regulation of Integrin activation organizes a stereotypic pattern of ECM necessary for vertebrate body elongation and segmentation.
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26
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Lee IH, Saha S, Polley A, Huang H, Mayor S, Rao M, Groves JT. Live cell plasma membranes do not exhibit a miscibility phase transition over a wide range of temperatures. J Phys Chem B 2015; 119:4450-9. [PMID: 25747462 DOI: 10.1021/jp512839q] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Lipid/cholesterol mixtures derived from cell membranes as well as their synthetic reconstitutions exhibit well-defined miscibility phase transitions and critical phenomena near physiological temperatures. This suggests that lipid/cholesterol-mediated phase separation plays a role in the organization of live cell membranes. However, macroscopic lipid-phase separation is not generally observed in cell membranes, and the degree to which properties of isolated lipid mixtures are preserved in the cell membrane remain unknown. A fundamental property of phase transitions is that the variation of tagged particle diffusion with temperature exhibits an abrupt change as the system passes through the transition, even when the two phases are distributed in a nanometer-scale emulsion. We support this using a variety of Monte Carlo and atomistic simulations on model lipid membrane systems. However, temperature-dependent fluorescence correlation spectroscopy of labeled lipids and membrane-anchored proteins in live cell membranes shows a consistently smooth increase in the diffusion coefficient as a function of temperature. We find no evidence of a discrete miscibility phase transition throughout a wide range of temperatures: 14-37 °C. This contrasts the behavior of giant plasma membrane vesicles (GPMVs) blebbed from the same cells, which do exhibit phase transitions and macroscopic phase separation. Fluorescence lifetime analysis of a DiI probe in both cases reveals a significant environmental difference between the live cell and the GPMV. Taken together, these data suggest the live cell membrane may avoid the miscibility phase transition inherent to its lipid constituents by actively regulating physical parameters, such as tension, in the membrane.
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Affiliation(s)
- Il-Hyung Lee
- †Department of Chemistry, California Institute for Quantitative Biosciences (QB3), Howard Hughes Medical Institute, University of California, Berkeley, California 94720, United States
| | - Suvrajit Saha
- §National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560065, India
| | - Anirban Polley
- ∥Raman Research Institute, C.V. Raman Avenue, Bangalore 560080, India
| | - Hector Huang
- †Department of Chemistry, California Institute for Quantitative Biosciences (QB3), Howard Hughes Medical Institute, University of California, Berkeley, California 94720, United States
| | - Satyajit Mayor
- §National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560065, India
| | - Madan Rao
- §National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560065, India.,∥Raman Research Institute, C.V. Raman Avenue, Bangalore 560080, India
| | - Jay T Groves
- †Department of Chemistry, California Institute for Quantitative Biosciences (QB3), Howard Hughes Medical Institute, University of California, Berkeley, California 94720, United States.,‡Materials Sciences Division, Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
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Krause MR, Regen SL. The structural role of cholesterol in cell membranes: from condensed bilayers to lipid rafts. Acc Chem Res 2014; 47:3512-21. [PMID: 25310179 DOI: 10.1021/ar500260t] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
CONSPECTUS: Defining the two-dimensional structure of cell membranes represents one of the most daunting challenges currently facing chemists, biochemists, and biophysicists. In particular, the time-averaged lateral organization of the lipids and proteins that make up these natural enclosures has yet to be established. As the classic Singer-Nicolson model of cell membranes has evolved over the past 40 years, special attention has focused on the structural role played by cholesterol, a key component that represents ca. 30% of the total lipids that are present. Despite extensive studies with model membranes, two fundamental issues have remained a mystery: (i) the mechanism by which cholesterol condenses low-melting lipids by uncoiling their acyl chains and (ii) the thermodynamics of the interaction between cholesterol and high- and low-melting lipids. The latter bears directly on one of the most popular notions in modern cell biology, that is, the lipid raft hypothesis, whereby cholesterol is thought to combine with high-melting lipids to form "lipid rafts" that float in a "sea" of low-melting lipids. In this Account, we first describe a chemical approach that we have developed in our laboratories that has allowed us to quantify the interactions between exchangeable mimics of cholesterol and low- and high-melting lipids in model membranes. In essence, this "nearest-neighbor recognition" (NNR) method involves the synthesis of dimeric forms of these lipids that contain a disulfide moiety as a linker. By means of thiolate-disulfide interchange reactions, equilibrium mixtures of dimers are then formed. These exchange reactions are initiated either by adding dithiothreitol to a liposomal dispersion to generate a small amount of thiol monomer or by including a small amount of thiol monomer in the liposomes at pH 5.0 and then raising the pH to 7.4. We then show how such NNR measurements have allowed us to distinguish between two very different mechanisms that have been proposed for cholesterol's condensing effect: (i) an umbrella mechanism in which the acyl chains and cholesterol become more tightly packed as cholesterol content increases because they share limited space under phospholipid headgroups and (ii) a template mechanism whereby cholesterol functions as a planar hydrophobic template at the membrane surface, thereby maximizing hydrophobic interactions and the hydrophobic effect. Specifically, our NNR experiments rule out the umbrella mechanism and provide strong support for the template mechanism. Similar NNR measurements have also allowed us to address the question of whether the interactions between low-melting kinked phospholipids and cholesterol can play a significant role in the formation of lipid rafts. Specifically, these NNR measurements have led to our discovery of a new physical principle in the lipids and membranes area that must be operating in biological membranes, that is, a "push-pull" mechanism, whereby cholesterol is pushed away from low-melting phospholipids and pulled toward high-melting lipids. Thus, to the extent that lipid rafts play a role in the functioning of cell membranes, low-melting phospholipids must be active participants.
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Affiliation(s)
- Martin R. Krause
- Department
of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Steven L. Regen
- Department
of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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28
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Baumgart F, Schütz GJ. Detecting protein association at the T cell plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:791-801. [PMID: 25300585 DOI: 10.1016/j.bbamcr.2014.09.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 09/18/2014] [Accepted: 09/29/2014] [Indexed: 10/24/2022]
Abstract
At the moment, many models on T cell signaling rely on results obtained via rather indirect methodologies, which makes direct comparison and conclusions to the in vivo situation difficult. Recently, a variety of new imaging methods were developed, which have the potential to directly shed light onto the mysteries of protein association at the T cell membrane. While the new modalities are extremely promising, for a broad readership it may be difficult to judge the results, since technological shortcomings are not always obvious. In this review article, we put key questions on the mechanism of protein interactions in the T cell plasma membrane into relation with techniques that allow to address such questions. We discuss applicability of the techniques, their strengths and weaknesses. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.
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Affiliation(s)
- Florian Baumgart
- Vienna University of Technology, Institute for Applied Physics, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria
| | - Gerhard J Schütz
- Vienna University of Technology, Institute for Applied Physics, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria.
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29
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Weidemann T, Mücksch J, Schwille P. Fluorescence fluctuation microscopy: a diversified arsenal of methods to investigate molecular dynamics inside cells. Curr Opin Struct Biol 2014; 28:69-76. [DOI: 10.1016/j.sbi.2014.07.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 07/11/2014] [Indexed: 11/26/2022]
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30
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Lai JM, Shao HJ, Wu JC, Lu SH, Chang YC. Efficient elusion of viable adhesive cells from a microfluidic system by air foam. BIOMICROFLUIDICS 2014; 8:052001. [PMID: 25332725 PMCID: PMC4189394 DOI: 10.1063/1.4893348] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 08/06/2014] [Indexed: 05/15/2023]
Abstract
We developed a new method for releasing viable cells from affinity-based microfluidic devices. The lumen of a microchannel with a U-shape and user-designed microstructures was coated with supported lipid bilayers functionalized by epithelial cell adhesion molecule antibodies to capture circulating epithelial cells of influx solution. After the capturing process, air foam was introduced into channels for releasing target cells and then carrying them to a small area of membrane. The results show that when the air foam is driven at linear velocity of 4.2 mm/s for more than 20 min or at linear velocity of 8.4 mm/s for more than 10 min, the cell releasing efficiency approaches 100%. This flow-induced shear stress is much less than the physiological level (15 dyn/cm(2)), which is necessary to maintain the intactness of released cells. Combining the design of microstructures of the microfluidic system, the cell recovery on the membrane exceeds 90%. Importantly, we demonstrate that the cells released by air foam are viable and could be cultured in vitro. This novel method for releasing cells could power the microfluidic platform for isolating and identifying circulating tumor cells.
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Affiliation(s)
- Jr-Ming Lai
- Genomics Research Center , Academia Sinica, No. 128, Sec 2, Academic Rd., Nankang, Taipei 115, Taiwan
| | - Hung-Jen Shao
- Genomics Research Center , Academia Sinica, No. 128, Sec 2, Academic Rd., Nankang, Taipei 115, Taiwan
| | - Jen-Chia Wu
- Genomics Research Center , Academia Sinica, No. 128, Sec 2, Academic Rd., Nankang, Taipei 115, Taiwan
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31
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Iversen L, Tu HL, Lin WC, Christensen SM, Abel SM, Iwig J, Wu HJ, Gureasko J, Rhodes C, Petit RS, Hansen SD, Thill P, Yu CH, Stamou D, Chakraborty AK, Kuriyan J, Groves JT. Molecular kinetics. Ras activation by SOS: allosteric regulation by altered fluctuation dynamics. Science 2014; 345:50-4. [PMID: 24994643 DOI: 10.1126/science.1250373] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Activation of the small guanosine triphosphatase H-Ras by the exchange factor Son of Sevenless (SOS) is an important hub for signal transduction. Multiple layers of regulation, through protein and membrane interactions, govern activity of SOS. We characterized the specific activity of individual SOS molecules catalyzing nucleotide exchange in H-Ras. Single-molecule kinetic traces revealed that SOS samples a broad distribution of turnover rates through stochastic fluctuations between distinct, long-lived (more than 100 seconds), functional states. The expected allosteric activation of SOS by Ras-guanosine triphosphate (GTP) was conspicuously absent in the mean rate. However, fluctuations into highly active states were modulated by Ras-GTP. This reveals a mechanism in which functional output may be determined by the dynamical spectrum of rates sampled by a small number of enzymes, rather than the ensemble average.
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Affiliation(s)
- Lars Iversen
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Hsiung-Lin Tu
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Wan-Chen Lin
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Sune M Christensen
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Steven M Abel
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
| | - Jeff Iwig
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Hung-Jen Wu
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jodi Gureasko
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Christopher Rhodes
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Rebecca S Petit
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Scott D Hansen
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Peter Thill
- Department of Chemistry, MIT, Cambridge, MA 02139, USA
| | - Cheng-Han Yu
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Dimitrios Stamou
- Department of Chemistry and Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
| | - Arup K Chakraborty
- Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA. Department of Chemistry, MIT, Cambridge, MA 02139, USA. Department of Biological Engineering, MIT, Cambridge, MA 02139, USA. Ragon Institute of Massachusetts General Hospital, MIT, and Harvard, Cambridge, MA 02139, USA. Department of Physics, MIT, Cambridge, MA 02139, USA. Institute for Medical Engineering and Science, MIT, Cambridge, MA 02139, USA
| | - John Kuriyan
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA. Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA. Physical Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jay T Groves
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA. Mechanobiology Institute, National University of Singapore, Singapore. Physical Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Berkeley Education Alliance for Research in Singapore, 1 Create Way, CREATE tower level 11, University Town, Singapore 138602.
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32
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Comar W, Schubert SM, Jastrzebska B, Palczewski K, Smith AW. Time-resolved fluorescence spectroscopy measures clustering and mobility of a G protein-coupled receptor opsin in live cell membranes. J Am Chem Soc 2014; 136:8342-9. [PMID: 24831851 PMCID: PMC4063175 DOI: 10.1021/ja501948w] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Indexed: 01/31/2023]
Abstract
Determining membrane protein quaternary structure is extremely challenging, especially in live cell membranes. We measured the oligomerization of opsin, a prototypical G protein-coupled receptor with pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). Individual cell measurements revealed that opsin is predominantly organized into dimeric clusters. At low concentrations, we observed that the population of oligomers increased linearly with the square of the individual monomer populations. This finding supports a monomer-dimer equilibrium and provides an experimental measurement of the equilibrium constant.
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Affiliation(s)
- William
D. Comar
- The
University of Akron Department of Chemistry, 190 Buchtel Common, Akron, Ohio 44303-3601, United States
| | - Sarah M. Schubert
- The
University of Akron Department of Chemistry, 190 Buchtel Common, Akron, Ohio 44303-3601, United States
| | - Beata Jastrzebska
- Department
of Pharmacology, School of Medicine, Case
Western Reserve University, 2109 Adelbert Road, Cleveland, Ohio 44106-4965, United States
| | - Krzysztof Palczewski
- Department
of Pharmacology, School of Medicine, Case
Western Reserve University, 2109 Adelbert Road, Cleveland, Ohio 44106-4965, United States
| | - Adam W. Smith
- The
University of Akron Department of Chemistry, 190 Buchtel Common, Akron, Ohio 44303-3601, United States
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33
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Greene AC, Lord SJ, Tian A, Rhodes C, Kai H, Groves JT. Spatial organization of EphA2 at the cell-cell interface modulates trans-endocytosis of ephrinA1. Biophys J 2014; 106:2196-205. [PMID: 24853748 PMCID: PMC4052362 DOI: 10.1016/j.bpj.2014.03.043] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 03/26/2014] [Accepted: 03/31/2014] [Indexed: 11/21/2022] Open
Abstract
EphA2 is a receptor tyrosine kinase (RTK) that is sensitive to spatial and mechanical aspects of the cell's microenvironment. Misregulation of EphA2 occurs in many aggressive cancers. Although its juxtacrine signaling geometry (EphA2's cognate ligand ephrinA1 is expressed on the surface of an apposing cell) provides a mechanism by which the receptor may experience extracellular forces, this also renders the system challenging to decode. By depositing living cells on synthetic supported lipid membranes displaying ephrinA1, we have reconstituted key features of the juxtacrine EphA2-ephrinA1 signaling system while maintaining the ability to perturb the spatial and mechanical properties of the membrane-cell interface with precision. In addition, we developed a trans-endocytosis assay to monitor internalization of ephrinA1 from a supported membrane into the apposing cell using a quantitative three-dimensional fluorescence microscopy assay. Using this experimental platform to mimic a cell-cell junction, we found that the signaling complex is not efficiently internalized when lateral reorganization at the membrane-cell contact sites is physically hindered. This suggests that EphA2-ephrinA1 trans-endocytosis is sensitive to the mechanical properties of a cell's microenvironment and may have implications in physical aspects of tumor biology.
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Affiliation(s)
- Adrienne C Greene
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California; Department of Molecular and Cell Biology, University of California, Berkeley, California
| | - Samuel J Lord
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California
| | - Aiwei Tian
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California
| | - Christopher Rhodes
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California; Department of Mechanical Engineering, University of California, Berkeley, California
| | - Hiroyuki Kai
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California
| | - Jay T Groves
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California; Mechanobiology Institute, National University of Singapore, Singapore.
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34
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Recent applications of fluorescence correlation spectroscopy in live systems. FEBS Lett 2014; 588:3571-84. [PMID: 24726724 DOI: 10.1016/j.febslet.2014.03.056] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Revised: 03/29/2014] [Accepted: 03/31/2014] [Indexed: 11/20/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) is a widely used technique in biophysics and has helped address many questions in the life sciences. It provides important advantages compared to other fluorescence and biophysical methods. Its single molecule sensitivity allows measuring proteins within biological samples at physiological concentrations without the need of overexpression. It provides quantitative data on concentrations, diffusion coefficients, molecular transport and interactions even in live organisms. And its reliance on simple fluorescence intensity and its fluctuations makes it widely applicable. In this review we focus on applications of FCS in live samples, with an emphasis on work in the last 5 years, in the hope to provide an overview of the present capabilities of FCS to address biologically relevant questions.
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35
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H-Ras forms dimers on membrane surfaces via a protein-protein interface. Proc Natl Acad Sci U S A 2014; 111:2996-3001. [PMID: 24516166 DOI: 10.1073/pnas.1321155111] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The lipid-anchored small GTPase Ras is an important signaling node in mammalian cells. A number of observations suggest that Ras is laterally organized within the cell membrane, and this may play a regulatory role in its activation. Lipid anchors composed of palmitoyl and farnesyl moieties in H-, N-, and K-Ras are widely suspected to be responsible for guiding protein organization in membranes. Here, we report that H-Ras forms a dimer on membrane surfaces through a protein-protein binding interface. A Y64A point mutation in the switch II region, known to prevent Son of sevenless and PI3K effector interactions, abolishes dimer formation. This suggests that the switch II region, near the nucleotide binding cleft, is either part of, or allosterically coupled to, the dimer interface. By tethering H-Ras to bilayers via a membrane-miscible lipid tail, we show that dimer formation is mediated by protein interactions and does not require lipid anchor clustering. We quantitatively characterize H-Ras dimerization in supported membranes using a combination of fluorescence correlation spectroscopy, photon counting histogram analysis, time-resolved fluorescence anisotropy, single-molecule tracking, and step photobleaching analysis. The 2D dimerization Kd is measured to be ∼1 × 10(3) molecules/µm(2), and no higher-order oligomers were observed. Dimerization only occurs on the membrane surface; H-Ras is strictly monomeric at comparable densities in solution. Analysis of a number of H-Ras constructs, including key changes to the lipidation pattern of the hypervariable region, suggest that dimerization is a general property of native H-Ras on membrane surfaces.
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36
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Antibody conjugated supported lipid bilayer for capturing and purification of viable tumor cells in blood for subsequent cell culture. Biomaterials 2013; 34:5191-9. [DOI: 10.1016/j.biomaterials.2013.03.096] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 03/29/2013] [Indexed: 01/26/2023]
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37
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Coyle MP, Xu Q, Chiang S, Francis MB, Groves JT. DNA-mediated assembly of protein heterodimers on membrane surfaces. J Am Chem Soc 2013; 135:5012-6. [PMID: 23530555 PMCID: PMC3626235 DOI: 10.1021/ja3101215] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a method based on self-assembling oligonucleotides to anchor proteins to a supported membrane surface. This anchoring method allows control of the surface density of multiple proteins. By incorporating additional recognition sequences into the DNA linkers, defined heterodimers can be produced upon the addition of a heterospecific DNA cross-linking strand. Characterization by fluorescence cross-correlation spectroscopy (FCCS) confirmed lateral mobility and the formation of specific heterodimers. We further demonstrate that proteins linked in this manner as either monomers or dimers can form functional interfaces with living cells.
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Affiliation(s)
- Michael P Coyle
- Department of Chemistry and ‡Howard Hughes Medical Institute, University of California , Berkeley, California 94720, United States
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38
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Klotzsch E, Schütz GJ. A critical survey of methods to detect plasma membrane rafts. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120033. [PMID: 23267184 PMCID: PMC3538433 DOI: 10.1098/rstb.2012.0033] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The plasma membrane is still one of the enigmatic cellular structures. Although the microscopic structure is getting clearer, not much is known about the organization at the nanometre level. Experimental difficulties have precluded unambiguous approaches, making the current picture rather fuzzy. In consequence, a variety of different membrane models has been proposed over the years, on the basis of different experimental strategies. Recent data obtained via high-resolution single-molecule microscopy shed new light on the existing hypotheses. We thus think it is a good time for reviewing the consistency of the existing models with the new data. In this paper, we summarize the available models in ten propositions, each of which is discussed critically with respect to the applied technologies and the strengths and weaknesses of the approaches. Our aim is to provide the reader with a sound basis for his own assessment. We close this chapter by exposing our picture of the membrane organization at the nanoscale.
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Affiliation(s)
| | - Gerhard J. Schütz
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8–10, Vienna 1040, Austria
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39
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Daly TA, Almeida PF, Regen SL. Sorting of lipidated peptides in fluid bilayers: a molecular-level investigation. J Am Chem Soc 2012; 134:17245-52. [PMID: 22998217 PMCID: PMC3474883 DOI: 10.1021/ja3074825] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nearest-neighbor recognition (NNR) measurements have been made for two lipidated forms of GlyCys, interacting with analogues of cholesterol and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in the liquid-ordered (l(o)) and liquid-disordered (l(d)) phases. Interaction free energies that have been determined from these measurements have been used in Monte Carlo simulations to quantify the distribution of the peptides between liquid-ordered and liquid-disordered regions. These simulations have shown that significant differences in the lipid chains have a very weak influence on the partitioning of the peptide between these two phases. They have also revealed an insensitivity of the peptide partition coefficient, K(p), to the size of the l(o) and l(d) domains that are present. In a broader context, these findings strongly suggest that the sorting of peripheral proteins in cellular membranes via differential lipidation may be more subtle than previously thought.
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Affiliation(s)
- Trevor A. Daly
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18105
| | - Paulo F. Almeida
- Department of Chemistry and Biochemistry, University of North Carolina at Wilmington, North Carolina 28403
| | - Steven L. Regen
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18105
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