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Ujlaky-Nagy L, Szöllősi J, Vereb G. Disrupting EGFR-HER2 Transactivation by Pertuzumab in HER2-Positive Cancer: Quantitative Analysis Reveals EGFR Signal Input as Potential Predictor of Therapeutic Outcome. Int J Mol Sci 2024; 25:5978. [PMID: 38892166 PMCID: PMC11173106 DOI: 10.3390/ijms25115978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 05/26/2024] [Accepted: 05/27/2024] [Indexed: 06/21/2024] Open
Abstract
Pertuzumab (Perjeta®), a humanized antibody binding to the dimerization arm of HER2 (Human epidermal growth factor receptor-2), has failed as a monotherapy agent in HER2 overexpressing malignancies. Since the molecular interaction of HER2 with ligand-bound EGFR (epidermal growth factor receptor) has been implied in mitogenic signaling and malignant proliferation, we hypothesized that this interaction, rather than HER2 expression and oligomerization alone, could be a potential molecular target and predictor of the efficacy of pertuzumab treatment. Therefore, we investigated static and dynamic interactions between HER2 and EGFR molecules upon EGF stimulus in the presence and absence of pertuzumab in HER2+ EGFR+ SK-BR-3 breast tumor cells using Förster resonance energy transfer (FRET) microscopy and fluorescence correlation and cross-correlation spectroscopy (FCS/FCCS). The consequential activation of signaling and changes in cell proliferation were measured by Western blotting and MTT assay. The autocorrelation functions of HER2 diffusion were best fitted by a three-component model corrected for triplet formation, and among these components the slowly diffusing membrane component revealed aggregation induced by EGFR ligand binding, as evidenced by photon-counting histograms and co-diffusing fractions. This aggregation has efficiently been prevented by pertuzumab treatment, which also inhibited the post-stimulus interaction of EGFR and HER2, as monitored by changes in FRET efficiency. Overall, the data demonstrated that pertuzumab, by hindering post-stimulus interaction between EGFR and HER2, inhibits EGFR-evoked HER2 aggregation and phosphorylation and leads to a dose-dependent decrease in cell proliferation, particularly when higher amounts of EGF are present. Consequently, we propose that EGFR expression on HER2-positive tumors could be taken into consideration as a potential biomarker when predicting the outcome of pertuzumab treatment.
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Affiliation(s)
- László Ujlaky-Nagy
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
- HUN-REN-UD Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
| | - János Szöllősi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
- HUN-REN-UD Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
| | - György Vereb
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
- HUN-REN-UD Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
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2
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Nederveen-Schippers LM, Pathak P, Keizer-Gunnink I, Westphal AH, van Haastert PJM, Borst JW, Kortholt A, Skakun V. Combined FCS and PCH Analysis to Quantify Protein Dimerization in Living Cells. Int J Mol Sci 2021; 22:ijms22147300. [PMID: 34298920 PMCID: PMC8307594 DOI: 10.3390/ijms22147300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 06/25/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022] Open
Abstract
Protein dimerization plays a crucial role in the regulation of numerous biological processes. However, detecting protein dimers in a cellular environment is still a challenge. Here we present a methodology to measure the extent of dimerization of GFP-tagged proteins in living cells, using a combination of fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) analysis of single-color fluorescence fluctuation data. We named this analysis method brightness and diffusion global analysis (BDGA) and adapted it for biological purposes. Using cell lysates containing different ratios of GFP and tandem-dimer GFP (diGFP), we show that the average brightness per particle is proportional to the fraction of dimer present. We further adapted this methodology for its application in living cells, and we were able to distinguish GFP, diGFP, as well as ligand-induced dimerization of FKBP12 (FK506 binding protein 12)-GFP. While other analysis methods have only sporadically been used to study dimerization in living cells and may be prone to errors, this paper provides a robust approach for the investigation of any cytosolic protein using single-color fluorescence fluctuation spectroscopy.
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Affiliation(s)
- Laura M. Nederveen-Schippers
- Department of Cell Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands; (L.M.N.-S.); (P.P.); (I.K.-G.); (P.J.M.v.H.)
| | - Pragya Pathak
- Department of Cell Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands; (L.M.N.-S.); (P.P.); (I.K.-G.); (P.J.M.v.H.)
| | - Ineke Keizer-Gunnink
- Department of Cell Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands; (L.M.N.-S.); (P.P.); (I.K.-G.); (P.J.M.v.H.)
| | - Adrie H. Westphal
- Laboratory of Biochemistry, Wageningen University & Research, 6708 WE Wageningen, The Netherlands; (A.H.W.); (J.W.B.)
| | - Peter J. M. van Haastert
- Department of Cell Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands; (L.M.N.-S.); (P.P.); (I.K.-G.); (P.J.M.v.H.)
| | - Jan Willem Borst
- Laboratory of Biochemistry, Wageningen University & Research, 6708 WE Wageningen, The Netherlands; (A.H.W.); (J.W.B.)
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands; (L.M.N.-S.); (P.P.); (I.K.-G.); (P.J.M.v.H.)
- Correspondence: (A.K.); (V.S.)
| | - Victor Skakun
- Department of Systems Analysis and Computer Simulation, Belarusian State University, 220030 Minsk, Belarus
- Correspondence: (A.K.); (V.S.)
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3
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Lerner E, Barth A, Hendrix J, Ambrose B, Birkedal V, Blanchard SC, Börner R, Sung Chung H, Cordes T, Craggs TD, Deniz AA, Diao J, Fei J, Gonzalez RL, Gopich IV, Ha T, Hanke CA, Haran G, Hatzakis NS, Hohng S, Hong SC, Hugel T, Ingargiola A, Joo C, Kapanidis AN, Kim HD, Laurence T, Lee NK, Lee TH, Lemke EA, Margeat E, Michaelis J, Michalet X, Myong S, Nettels D, Peulen TO, Ploetz E, Razvag Y, Robb NC, Schuler B, Soleimaninejad H, Tang C, Vafabakhsh R, Lamb DC, Seidel CAM, Weiss S. FRET-based dynamic structural biology: Challenges, perspectives and an appeal for open-science practices. eLife 2021; 10:e60416. [PMID: 33779550 PMCID: PMC8007216 DOI: 10.7554/elife.60416] [Citation(s) in RCA: 125] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 02/09/2021] [Indexed: 12/18/2022] Open
Abstract
Single-molecule FRET (smFRET) has become a mainstream technique for studying biomolecular structural dynamics. The rapid and wide adoption of smFRET experiments by an ever-increasing number of groups has generated significant progress in sample preparation, measurement procedures, data analysis, algorithms and documentation. Several labs that employ smFRET approaches have joined forces to inform the smFRET community about streamlining how to perform experiments and analyze results for obtaining quantitative information on biomolecular structure and dynamics. The recent efforts include blind tests to assess the accuracy and the precision of smFRET experiments among different labs using various procedures. These multi-lab studies have led to the development of smFRET procedures and documentation, which are important when submitting entries into the archiving system for integrative structure models, PDB-Dev. This position paper describes the current 'state of the art' from different perspectives, points to unresolved methodological issues for quantitative structural studies, provides a set of 'soft recommendations' about which an emerging consensus exists, and lists openly available resources for newcomers and seasoned practitioners. To make further progress, we strongly encourage 'open science' practices.
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Affiliation(s)
- Eitan Lerner
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, and The Center for Nanoscience and Nanotechnology, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of JerusalemJerusalemIsrael
| | - Anders Barth
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-UniversitätDüsseldorfGermany
| | - Jelle Hendrix
- Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre and Biomedical Research Institute (BIOMED), Hasselt UniversityDiepenbeekBelgium
| | - Benjamin Ambrose
- Department of Chemistry, University of SheffieldSheffieldUnited Kingdom
| | - Victoria Birkedal
- Department of Chemistry and iNANO center, Aarhus UniversityAarhusDenmark
| | - Scott C Blanchard
- Department of Structural Biology, St. Jude Children's Research HospitalMemphisUnited States
| | - Richard Börner
- Laserinstitut HS Mittweida, University of Applied Science MittweidaMittweidaGermany
| | - Hoi Sung Chung
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUnited States
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität MünchenPlanegg-MartinsriedGermany
| | - Timothy D Craggs
- Department of Chemistry, University of SheffieldSheffieldUnited Kingdom
| | - Ashok A Deniz
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Jiajie Diao
- Department of Cancer Biology, University of Cincinnati School of MedicineCincinnatiUnited States
| | - Jingyi Fei
- Department of Biochemistry and Molecular Biology and The Institute for Biophysical Dynamics, University of ChicagoChicagoUnited States
| | - Ruben L Gonzalez
- Department of Chemistry, Columbia UniversityNew YorkUnited States
| | - Irina V Gopich
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUnited States
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Howard Hughes Medical InstituteBaltimoreUnited States
| | - Christian A Hanke
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-UniversitätDüsseldorfGermany
| | - Gilad Haran
- Department of Chemical and Biological Physics, Weizmann Institute of ScienceRehovotIsrael
| | - Nikos S Hatzakis
- Department of Chemistry & Nanoscience Centre, University of CopenhagenCopenhagenDenmark
- Denmark Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of CopenhagenCopenhagenDenmark
| | - Sungchul Hohng
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National UniversitySeoulRepublic of Korea
| | - Seok-Cheol Hong
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science and Department of Physics, Korea UniversitySeoulRepublic of Korea
| | - Thorsten Hugel
- Institute of Physical Chemistry and Signalling Research Centres BIOSS and CIBSS, University of FreiburgFreiburgGermany
| | - Antonino Ingargiola
- Department of Chemistry and Biochemistry, and Department of Physiology, University of California, Los AngelesLos AngelesUnited States
| | - Chirlmin Joo
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of TechnologyDelftNetherlands
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of OxfordOxfordUnited Kingdom
| | - Harold D Kim
- School of Physics, Georgia Institute of TechnologyAtlantaUnited States
| | - Ted Laurence
- Physical and Life Sciences Directorate, Lawrence Livermore National LaboratoryLivermoreUnited States
| | - Nam Ki Lee
- School of Chemistry, Seoul National UniversitySeoulRepublic of Korea
| | - Tae-Hee Lee
- Department of Chemistry, Pennsylvania State UniversityUniversity ParkUnited States
| | - Edward A Lemke
- Departments of Biology and Chemistry, Johannes Gutenberg UniversityMainzGermany
- Institute of Molecular Biology (IMB)MainzGermany
| | - Emmanuel Margeat
- Centre de Biologie Structurale (CBS), CNRS, INSERM, Universitié de MontpellierMontpellierFrance
| | | | - Xavier Michalet
- Department of Chemistry and Biochemistry, and Department of Physiology, University of California, Los AngelesLos AngelesUnited States
| | - Sua Myong
- Department of Biophysics, Johns Hopkins UniversityBaltimoreUnited States
| | - Daniel Nettels
- Department of Biochemistry and Department of Physics, University of ZurichZurichSwitzerland
| | - Thomas-Otavio Peulen
- Department of Bioengineering and Therapeutic Sciences, University of California, San FranciscoSan FranciscoUnited States
| | - Evelyn Ploetz
- Physical Chemistry, Department of Chemistry, Center for Nanoscience (CeNS), Center for Integrated Protein Science Munich (CIPSM) and Nanosystems Initiative Munich (NIM), Ludwig-Maximilians-UniversitätMünchenGermany
| | - Yair Razvag
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, and The Center for Nanoscience and Nanotechnology, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of JerusalemJerusalemIsrael
| | - Nicole C Robb
- Warwick Medical School, University of WarwickCoventryUnited Kingdom
| | - Benjamin Schuler
- Department of Biochemistry and Department of Physics, University of ZurichZurichSwitzerland
| | - Hamid Soleimaninejad
- Biological Optical Microscopy Platform (BOMP), University of MelbourneParkvilleAustralia
| | - Chun Tang
- College of Chemistry and Molecular Engineering, PKU-Tsinghua Center for Life Sciences, Beijing National Laboratory for Molecular Sciences, Peking UniversityBeijingChina
| | - Reza Vafabakhsh
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | - Don C Lamb
- Physical Chemistry, Department of Chemistry, Center for Nanoscience (CeNS), Center for Integrated Protein Science Munich (CIPSM) and Nanosystems Initiative Munich (NIM), Ludwig-Maximilians-UniversitätMünchenGermany
| | - Claus AM Seidel
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-UniversitätDüsseldorfGermany
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, and Department of Physiology, University of California, Los AngelesLos AngelesUnited States
- Department of Physiology, CaliforniaNanoSystems Institute, University of California, Los AngelesLos AngelesUnited States
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4
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Ulbricht C, Leben R, Rakhymzhan A, Kirchhoff F, Nitschke L, Radbruch H, Niesner RA, Hauser AE. Intravital quantification reveals dynamic calcium concentration changes across B cell differentiation stages. eLife 2021; 10:56020. [PMID: 33749591 PMCID: PMC8060033 DOI: 10.7554/elife.56020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/19/2021] [Indexed: 01/31/2023] Open
Abstract
Calcium is a universal second messenger present in all eukaryotic cells. The mobilization and storage of Ca2+ ions drives a number of signaling-related processes, stress-responses, or metabolic changes, all of which are relevant for the development of immune cells and their adaption to pathogens. Here, we introduce the Förster resonance energy transfer (FRET)-reporter mouse YellowCaB expressing the genetically encoded calcium indicator TN-XXL in B lymphocytes. Calcium-induced conformation change of TN-XXL results in FRET-donor quenching measurable by two-photon fluorescence lifetime imaging. For the first time, using our novel numerical analysis, we extract absolute cytoplasmic calcium concentrations in activated B cells during affinity maturation in vivo. We show that calcium in activated B cells is highly dynamic and that activation introduces a persistent calcium heterogeneity to the lineage. A characterization of absolute calcium concentrations present at any time within the cytosol is therefore of great value for the understanding of long-lived beneficial immune responses and detrimental autoimmunity.
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Affiliation(s)
- Carolin Ulbricht
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Rheumatology and Clinical Immunology, Charitéplatz 1, Berlin, Germany.,Immune Dynamics, Deutsches Rheuma-Forschungszentrum Berlin, ein Institut der Leibniz-Gemeinschaft, Berlin, Germany
| | - Ruth Leben
- Biophysical Analytics, Deutsches Rheuma-Forschungszentrum, ein Institut der Leibniz-Gemeinschaft, Berlin, Germany
| | - Asylkhan Rakhymzhan
- Biophysical Analytics, Deutsches Rheuma-Forschungszentrum, ein Institut der Leibniz-Gemeinschaft, Berlin, Germany
| | | | - Lars Nitschke
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Helena Radbruch
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Neuropathology, Charitéplatz 1, Berlin, Germany
| | - Raluca A Niesner
- Biophysical Analytics, Deutsches Rheuma-Forschungszentrum, ein Institut der Leibniz-Gemeinschaft, Berlin, Germany.,Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Anja E Hauser
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Rheumatology and Clinical Immunology, Charitéplatz 1, Berlin, Germany.,Immune Dynamics, Deutsches Rheuma-Forschungszentrum Berlin, ein Institut der Leibniz-Gemeinschaft, Berlin, Germany
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5
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Lau D, Walsh JC, Dickson CF, Tuckwell A, Stear JH, Hunter DJB, Bhumkar A, Shah V, Turville SG, Sierecki E, Gambin Y, Böcking T, Jacques DA. Rapid HIV-1 Capsid Interaction Screening Using Fluorescence Fluctuation Spectroscopy. Anal Chem 2021; 93:3786-3793. [PMID: 33593049 DOI: 10.1021/acs.analchem.0c04250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The HIV capsid is a multifunctional protein capsule that mediates the delivery of the viral genetic material into the nucleus of the target cell. Host cell proteins bind to a number of repeating binding sites on the capsid to regulate steps in the replication cycle. Here, we develop a fluorescence fluctuation spectroscopy method using self-assembled capsid particles as the bait to screen for fluorescence-labeled capsid-binding analytes ("prey" molecules) in solution. The assay capitalizes on the property of the HIV capsid as a multivalent interaction platform, facilitating high sensitivity detection of multiple prey molecules that have accumulated onto capsids as spikes in fluorescence intensity traces. By using a scanning stage, we reduced the measurement time to 10 s without compromising on sensitivity, providing a rapid binding assay for screening libraries of potential capsid interactors. The assay can also identify interfaces for host molecule binding by using capsids with defects in known interaction interfaces. Two-color coincidence detection using the fluorescent capsid as the bait further allows the quantification of binding levels and determination of binding affinities. Overall, the assay provides new tools for the discovery and characterization of molecules used by the HIV capsid to orchestrate infection. The measurement principle can be extended for the development of sensitive interaction assays, utilizing natural or synthetic multivalent scaffolds as analyte-binding platforms.
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Affiliation(s)
- Derrick Lau
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - James C Walsh
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Claire F Dickson
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Andrew Tuckwell
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Jeffrey H Stear
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Dominic J B Hunter
- The Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Akshay Bhumkar
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Vaibhav Shah
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Stuart G Turville
- The Kirby Institute, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Emma Sierecki
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Yann Gambin
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - David A Jacques
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
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Perego E, Köster S. Exploring early time points of vimentin assembly in flow by fluorescence fluctuation spectroscopy. LAB ON A CHIP 2021; 21:735-745. [PMID: 33491697 DOI: 10.1039/d0lc00985g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Despite the importance for cellular processes, the dynamics of molecular assembly, especially on fast time scales, is not yet fully understood. To this end, we present a multi-layer microfluidic device and combine it with fluorescence fluctuation spectroscopy. We apply this innovative combination of methods to investigate the early steps in assembly of vimentin intermediate filaments (IFs). These filaments, together with actin filaments and microtubules, constitute the cytoskeleton of cells of mesenchymal origin and greatly influence their mechanical properties. We are able to directly follow the two-step assembly process of vimentin IFs and quantify the time scale of the first lateral step to tens of ms with a lag time of below 3 ms. Although demonstrated for a specific biomolecular system here, our method may potentially be employed for a wide range of fast molecular reactions in biological or, more generally, soft matter systems, as it allows for a precise quantification of the kinetics underlying the aggregation and assembly.
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Affiliation(s)
- Eleonora Perego
- Institute for X-Ray Physics, University of Göttingen, 37077 Göttingen, Germany.
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, 37077 Göttingen, Germany. and Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Germany
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7
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Gunther G, Malacrida L, Jameson DM, Gratton E, Sánchez SA. LAURDAN since Weber: The Quest for Visualizing Membrane Heterogeneity. Acc Chem Res 2021; 54:976-987. [PMID: 33513300 PMCID: PMC8552415 DOI: 10.1021/acs.accounts.0c00687] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Any chemist studying the interaction of molecules with lipid assemblies will eventually be confronted by the topic of membrane bilayer heterogeneity and may ultimately encounter the heterogeneity of natural membranes. In artificial bilayers, heterogeneity is defined by phase segregation that can be in the nano- and micrometer range. In biological bilayers, heterogeneity is considered in the context of small (10-200 nm) sterol and sphingolipid-enriched heterogeneous and highly dynamic domains. Several techniques can be used to assess membrane heterogeneity in living systems. Our approach is to use a fluorescent reporter molecule immersed in the bilayer, which, by changes in its spectroscopic properties, senses physical-chemistry aspects of the membrane. This dye in combination with microscopy and fluctuation techniques can give information about membrane heterogeneity at different temporal and spatial levels: going from average fluidity to number and diffusion coefficient of nanodomains. LAURDAN (6-dodecanoyl-2-(dimethylamino) naphthalene), is a fluorescent probe designed and synthesized in 1979 by Gregorio Weber with the purpose to study the phenomenon of dipolar relaxation. The spectral displacement observed when LAURDAN is either in fluid or gel phase permitted the use of the technique in the field of membrane dynamics. The quantitation of the spectral displacement was first addressed by the generalized polarization (GP) function in the cuvette, a ratio of the difference in intensity at two wavelengths divided by their sum. In 1997, GP measurements were done for the first time in the microscope, adding to the technique the spatial resolution and allowing the visualization of lipid segregation both in liposomes and cells. A new prospective to the membrane heterogeneity was obtained when LAURDAN fluorescent lifetime measurements were done in the microscope. Two channel lifetime imaging provides information on membrane polarity and dipole relaxation (the two parameters responsible for the spectral shift of LAURDAN), and the application of phasor analysis allows pixel by pixel understanding of these two parameters in the membrane. To increase temporal resolution, LAURDAN GP was combined with fluctuation correlation spectroscopy (FCS) and the motility of nanometric highly packed structures in biological membranes was registered. Lately the application of phasor analysis to spectral images from membranes labeled with LAURDAN allows us to study the full spectra pixel by pixel in an image. All these methodologies, using LAURDAN, offer the possibility to address different properties of membranes depending on the question being asked. In this Account, we will focus on the principles, advantages, and limitations of different approaches to orient the reader to select the most appropriate technique for their research.
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Affiliation(s)
- German Gunther
- Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone P. 1007, Santiago 8380492, Chile
| | - Leonel Malacrida
- Advanced Microscopy and Biophotonics Unit, Hospital de Clínicas, Universidad de la República, Montevideo-Uruguay. Advanced Bioimaging Unit, Institut Pasteur Montevideo, Av. Italia s/n, 90600 Montevideo, Uruguay
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, Hawaii 96813, United States
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, 3210 Natural Sciences II, University of California, Irvine, Irvine, California 92697-2725, United States
| | - Susana A Sánchez
- Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Edmundo Larenas 129, Concepción 4070371, Chile
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8
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Wang H, Song S, Cheng H, Tan YW. State-of-the-Art Technologies for Understanding Brassinosteroid Signaling Networks. Int J Mol Sci 2020; 21:E8179. [PMID: 33142942 PMCID: PMC7662629 DOI: 10.3390/ijms21218179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 01/02/2023] Open
Abstract
Brassinosteroids, the steroid hormones of plants, control physiological and developmental processes through its signaling pathway. The major brassinosteroid signaling network components, from the receptor to transcription factors, have been identified in the past two decades. The development of biotechnologies has driven the identification of novel brassinosteroid signaling components, even revealing several crosstalks between brassinosteroid and other plant signaling pathways. Herein, we would like to summarize the identification and improvement of several representative brassinosteroid signaling components through the development of new technologies, including brassinosteroid-insensitive 1 (BRI1), BRI1-associated kinase 1 (BAK1), BR-insensitive 2 (BIN2), BRI1 kinase inhibitor 1 (BKI1), BRI1-suppressor 1 (BSU1), BR signaling kinases (BSKs), BRI1 ethyl methanesulfonate suppressor 1 (BES1), and brassinazole resistant 1 (BZR1). Furthermore, improvement of BR signaling knowledge, such as the function of BKI1, BES1 and its homologous through clustered regularly interspaced short palindromic repeats (CRISPR), the regulation of BIN2 through single-molecule methods, and the new in vivo interactors of BIN2 identified by proximity labeling are described. Among these technologies, recent advanced methods proximity labeling and single-molecule methods will be reviewed in detail to provide insights to brassinosteroid and other phytohormone signaling pathway studies.
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Affiliation(s)
- Haijiao Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475001, China;
| | - Song Song
- Department of Basic Courses, Zhejiang University of Water Resources and Electric Power, Hangzhou 310018, China;
| | - Huaqiang Cheng
- State Key Laboratory of Surface Physics, Multiscale Research Institute of Complex Systems, Department of Physics, Fudan University, Shanghai 200433, China;
| | - Yan-Wen Tan
- State Key Laboratory of Surface Physics, Multiscale Research Institute of Complex Systems, Department of Physics, Fudan University, Shanghai 200433, China;
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9
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Controlled division of cell-sized vesicles by low densities of membrane-bound proteins. Nat Commun 2020; 11:905. [PMID: 32060284 PMCID: PMC7021675 DOI: 10.1038/s41467-020-14696-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 01/24/2020] [Indexed: 11/12/2022] Open
Abstract
The proliferation of life on earth is based on the ability of single cells to divide into two daughter cells. During cell division, the plasma membrane undergoes a series of morphological transformations which ultimately lead to membrane fission. Here, we show that analogous remodeling processes can be induced by low densities of proteins bound to the membranes of cell-sized lipid vesicles. Using His-tagged fluorescent proteins, we are able to precisely control the spontaneous curvature of the vesicle membranes. By fine-tuning this curvature, we obtain dumbbell-shaped vesicles with closed membrane necks as well as neck fission and complete vesicle division. Our results demonstrate that the spontaneous curvature generates constriction forces around the membrane necks and that these forces can easily cover the force range found in vivo. Our approach involves only one species of membrane-bound proteins at low densities, thereby providing a simple and extendible module for bottom-up synthetic biology. Membrane fission of a cell into two daughters is a core ability of cell-based life. Here the authors show that in artificial cells division can be controlled by regulating membrane curvature using low protein density.
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10
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11
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Fluorescence fluctuation spectroscopy: an invaluable microscopy tool for uncovering the biophysical rules for navigating the nuclear landscape. Biochem Soc Trans 2019; 47:1117-1129. [DOI: 10.1042/bst20180604] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 11/17/2022]
Abstract
Abstract
Nuclear architecture is fundamental to the manner by which molecules traverse the nucleus. The nucleoplasm is a crowded environment where dynamic rearrangements in local chromatin compaction locally redefine the space accessible toward nuclear protein diffusion. Here, we review a suite of methods based on fluorescence fluctuation spectroscopy (FFS) and how they have been employed to interrogate chromatin organization, as well as the impact this structural framework has on nuclear protein target search. From first focusing on a set of studies that apply FFS to an inert fluorescent tracer diffusing inside the nucleus of a living cell, we demonstrate the capacity of this technology to measure the accessibility of the nucleoplasm. Then with a baseline understanding of the exploration volume available to nuclear proteins during target search, we review direct applications of FFS to fluorescently labeled transcription factors (TFs). FFS can detect changes in TF mobility due to DNA binding, as well as the formation of TF complexes via changes in brightness due to oligomerization. Collectively, we find that FFS-based methods can uncover how nuclear proteins in general navigate the nuclear landscape.
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12
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Cutrale F, Rodriguez D, Hortigüela V, Chiu CL, Otterstrom J, Mieruszynski S, Seriola A, Larrañaga E, Raya A, Lakadamyali M, Fraser SE, Martinez E, Ojosnegros S. Using enhanced number and brightness to measure protein oligomerization dynamics in live cells. Nat Protoc 2019; 14:616-638. [DOI: 10.1038/s41596-018-0111-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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13
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Raicu V. Extraction of information on macromolecular interactions from fluorescence micro-spectroscopy measurements in the presence and absence of FRET. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 199:340-348. [PMID: 29631099 DOI: 10.1016/j.saa.2018.03.075] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 03/26/2018] [Indexed: 06/08/2023]
Abstract
Investigations of static or dynamic interactions between proteins or other biological macromolecules in living cells often rely on the use of fluorescent tags with two different colors in conjunction with adequate theoretical descriptions of Förster Resonance Energy Transfer (FRET) and molecular-level micro-spectroscopic technology. One such method based on these general principles is FRET spectrometry, which allows determination of the quaternary structure of biomolecules from cell-level images of the distributions, or spectra of occurrence frequency of FRET efficiencies. Subsequent refinements allowed combining FRET frequency spectra with molecular concentration information, thereby providing the proportion of molecular complexes with various quaternary structures as well as their binding/dissociation energies. In this paper, we build on the mathematical principles underlying FRET spectrometry to propose two new spectrometric methods, which have distinct advantages compared to other methods. One of these methods relies on statistical analysis of color mixing in subpopulations of fluorescently tagged molecules to probe molecular association stoichiometry, while the other exploits the color shift induced by FRET to also derive geometric information in addition to stoichiometry. The appeal of the first method stems from its sheer simplicity, while the strength of the second consists in its ability to provide structural information.
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Affiliation(s)
- Valerică Raicu
- Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, United States of America.
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14
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Gunther G, Jameson DM, Aguilar J, Sánchez SA. Scanning fluorescence correlation spectroscopy comes full circle. Methods 2018; 140-141:52-61. [DOI: 10.1016/j.ymeth.2018.01.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/23/2018] [Accepted: 01/30/2018] [Indexed: 11/26/2022] Open
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15
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Gambin Y, Giles N, O'Carroll A, Polinkovsky M, Hunter D, Sierecki E. Single-Molecule Fluorescence Reveals the Oligomerization and Folding Steps Driving the Prion-like Behavior of ASC. J Mol Biol 2017; 430:491-508. [PMID: 29288634 DOI: 10.1016/j.jmb.2017.12.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 12/01/2017] [Accepted: 12/17/2017] [Indexed: 10/24/2022]
Abstract
Single-molecule fluorescence has the unique ability to quantify small oligomers and track conformational changes at a single-protein level. Here we tackled one of the most extreme protein behaviors, found recently in an inflammation pathway. Upon danger recognition in the cytosol, NLRP3 recruits its signaling adaptor, ASC. ASC start polymerizing in a prion-like manner and the system goes in "overdrive" by producing a single micron-sized "speck." By precisely controlling protein expression levels in an in vitro translation system, we could trigger the polymerization of ASC and mimic formation of specks in the absence of inflammasome nucleators. We utilized single-molecule spectroscopy to fully characterize prion-like behaviors and self-propagation of ASC fibrils. We next used our controlled system to monitor the conformational changes of ASC upon fibrillation. Indeed, ASC consists of a PYD and CARD domains, separated by a flexible linker. Individually, both domains have been found to form fibrils, but the structure of the polymers formed by the full-length ASC proteins remains elusive. For the first time, using single-molecule Förster resonance energy transfer, we studied the relative positions of the CARD and PYD domains of full-length ASC. An unexpectedly large conformational change occurred upon ASC fibrillation, suggesting that the CARD domain folds back onto the PYD domain. However, contradicting current models, the "prion-like" conformer was not initiated by binding of ASC to the NLRP3 platform. Rather, using a new method, hybrid between Photon Counting Histogram and Number and Brightness analysis, we showed that NLRP3 forms hexamers with self-binding affinities around 300nM. Overall our data suggest a new mechanism, where NLRP3 can initiate ASC polymerization simply by increasing the local concentration of ASC above a supercritical level.
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Affiliation(s)
- Yann Gambin
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, NSW 2052, Australia; The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia.
| | - Nichole Giles
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, NSW 2052, Australia; The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia
| | - Ailís O'Carroll
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, NSW 2052, Australia; The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia
| | - Mark Polinkovsky
- The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia
| | - Dominic Hunter
- The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia
| | - Emma Sierecki
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Kensington, NSW 2052, Australia; The Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia.
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16
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Elson EL. Introduction to fluorescence correlation Spectroscopy-Brief and simple. Methods 2017; 140-141:3-9. [PMID: 29155128 DOI: 10.1016/j.ymeth.2017.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/13/2017] [Indexed: 02/04/2023] Open
Affiliation(s)
- Elliot L Elson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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17
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Qu C, Jing B, Wang S, Zhu Y. Distinct Effects of Multivalent Macroion and Simple Ion on the Structure and Local Electric Environment of a Weak Polyelectrolyte in Aqueous Solution. J Phys Chem B 2017; 121:8829-8837. [DOI: 10.1021/acs.jpcb.7b05387] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chen Qu
- Department of Chemical
and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Benxin Jing
- Department of Chemical
and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Chemical Engineering and
Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Shengqin Wang
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*Stat), 117602 Singapore
| | - Yingxi Zhu
- Department of Chemical
and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Chemical Engineering and
Materials Science, Wayne State University, Detroit, Michigan 48202, United States
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18
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Li J, Barylko B, Eichorst JP, Mueller JD, Albanesi JP, Chen Y. Association of Endophilin B1 with Cytoplasmic Vesicles. Biophys J 2017; 111:565-576. [PMID: 27508440 DOI: 10.1016/j.bpj.2016.06.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 01/21/2023] Open
Abstract
Endophilins are SH3- and BAR domain-containing proteins implicated in membrane remodeling and vesicle formation. Endophilins A1 and A2 promote the budding of endocytic vesicles from the plasma membrane, whereas endophilin B1 has been implicated in vesicle budding from intracellular organelles, including the trans-Golgi network and late endosomes. We previously reported that endophilins A1 and A2 exist almost exclusively as soluble dimers in the cytosol. Here, we present results of fluorescence fluctuation spectroscopy analyses indicating that, in contrast, the majority of endophilin B1 is present in multiple copies on small, highly mobile cytoplasmic vesicles. Formation of these vesicles was enhanced by overexpression of wild-type dynamin 2, but suppressed by expression of a catalytically inactive dynamin 2 mutant. Using dual-color heterospecies partition analysis, we identified the epidermal growth factor receptor on endophilin B1 vesicles. Moreover, a proportion of endophilin B1 vesicles also contained caveolin, whereas clathrin was almost undetectable on those vesicles. These results raise the possibility that endophilin B1 participates in dynamin 2-dependent formation of a population of transport vesicles distinct from those generated by A-type endophilins.
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Affiliation(s)
- Jinhui Li
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | | | - John P Eichorst
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | | | - Yan Chen
- Department of Physics, University of Minnesota, Minneapolis, Minnesota.
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19
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Jiang Y, Pryse KM, Melnykov A, Genin GM, Elson EL. Investigation of Nanoscopic Phase Separations in Lipid Membranes Using Inverse FCS. Biophys J 2017; 112:2367-2376. [PMID: 28591609 PMCID: PMC5475253 DOI: 10.1016/j.bpj.2017.04.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 04/04/2017] [Accepted: 04/05/2017] [Indexed: 11/16/2022] Open
Abstract
Measurement of the sizes of nanoscopic particles is a difficult challenge, especially in two-dimensional systems such as cell membranes. We have extended inverse fluorescence correlation spectroscopy (iFCS) to endow it with unique advantages for measuring particle size from the nano- to the microscale. We have augmented iFCS with an analysis of moments of fluorescence fluctuations and used it to measure stages of phase separation in model lipid bilayer membranes. We observed two different pathways for the growth of phase domains. In one, nanoscopic gel domains appeared first and then gradually grew to micrometer size. In the other, the domains reached micrometer size quickly, and their number gradually increased. These measurements demonstrate the value of iFCS measurements through their ability, to our knowledge, to provide new information about the mechanism of lipid phase separation and potentially about the physical basis of naturally occurring nanodomains such as lipid rafts.
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Affiliation(s)
- Yanfei Jiang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Kenneth M Pryse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Artem Melnykov
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Guy M Genin
- Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, Missouri
| | - Elliot L Elson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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20
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Schneider M, Walta S, Cadek C, Richtering W, Willbold D. Fluorescence correlation spectroscopy reveals a cooperative unfolding of monomeric amyloid-β 42 with a low Gibbs free energy. Sci Rep 2017; 7:2154. [PMID: 28526839 PMCID: PMC5438374 DOI: 10.1038/s41598-017-02410-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 04/11/2017] [Indexed: 11/10/2022] Open
Abstract
The amyloid-beta peptide (Aβ) plays a major role in the progression of Alzheimer's disease. Due to its high toxicity, the 42 amino acid long isoform Aβ42 has become of considerable interest. The Aβ42 monomer is prone to aggregation down to the nanomolar range which makes conventional structural methods such as NMR or X-ray crystallography infeasible. Conformational information, however, will be helpful to understand the different aggregation pathways reported in the literature and will allow to identify potential conditions that favour aggregation-incompetent conformations. In this study, we applied fluorescence correlation spectroscopy (FCS) to investigate the unfolding of Alexa Fluor 488 labelled monomeric Aβ42 using guanidine hydrochloride as a denaturant. We show that our Aβ42 pre-treatment and the low-nanomolar concentrations, typically used for FCS measurements, strongly favour the presence of monomers. Our results reveal that there is an unfolding/folding behaviour of monomeric Aβ42. The existence of a cooperative unfolding curve suggests the presence of structural elements with a Gibbs free energy of unfolding of about 2.8 kcal/mol.
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Affiliation(s)
- Mario Schneider
- Institut für Physikalische Biologie, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Stefan Walta
- Institute of Physical Chemistry, RWTH Aachen University, JARA - Soft Matter Science, Aachen, Germany
| | - Chris Cadek
- Institut für Physikalische Biologie, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, JARA - Soft Matter Science, Aachen, Germany
| | - Dieter Willbold
- Institut für Physikalische Biologie, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany. .,Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, Jülich, Germany.
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21
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Abdollah-Nia F, Gelfand MP, Van Orden A. Artifact-Free and Detection-Profile-Independent Higher-Order Fluorescence Correlation Spectroscopy for Microsecond-Resolved Kinetics. 1. Multidetector and Sub-Binning Approach. J Phys Chem B 2017; 121:2373-2387. [DOI: 10.1021/acs.jpcb.7b00407] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Farshad Abdollah-Nia
- Department of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Martin P. Gelfand
- Department of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Alan Van Orden
- Department of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
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22
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Abdollah-Nia F, Gelfand MP, Van Orden A. Artifact-Free and Detection-Profile-Independent Higher-Order Fluorescence Correlation Spectroscopy for Microsecond-Resolved Kinetics. 2. Mixtures and Reactions. J Phys Chem B 2017; 121:2388-2399. [DOI: 10.1021/acs.jpcb.7b00408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Farshad Abdollah-Nia
- Department
of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Martin P. Gelfand
- Department
of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Alan Van Orden
- Department
of Physics and ‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
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23
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Liang EI, Mah EJ, Yee AF, Digman MA. Correlation of focal adhesion assembly and disassembly with cell migration on nanotopography. Integr Biol (Camb) 2017; 9:145-155. [PMID: 28092391 PMCID: PMC5399776 DOI: 10.1039/c6ib00193a] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Selective cell adhesion is desirable to control cell growth and migration on biomedical implants. Mesenchymal cell migration is regulated through focal adhesions (FAs) and can be modulated by their microenvironment, including changes in surface topography. We use the Number and Molecular Brightness (N&B) imaging analysis to provide a unique perspective on FA assembly and disassembly. This imaging analysis generates a map of real-time fluctuations of protein monomers, dimers, and higher order aggregates of FA proteins, such as paxillin during assembly and disassembly. We show a dynamic view of how nanostructured surfaces (nanoline gratings or nanopillars) regulate single molecular dynamics. In particular, we report that the smallest nanopillars (100 nm spacing) gave rise to a low population of disassembling adhesion clusters of ∼2 paxillin proteins whereas the larger nanopillars (380 nm spacing) gave rise to a much larger population of larger disassembling clusters of ∼3-5 paxillin proteins. Cells were more motile on the smaller nanopillars (spaced 100-130 nm apart) compared to all other surfaces studied. Thus, physical nanotopography influences cell motility, adhesion size, and adhesion assembly and disassembly. We report for the first time, with single molecular detection, how nanotopography influences cell motility and protein reorganization in adhesions.
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Affiliation(s)
- Elena I Liang
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697, USA.
| | - Emma J Mah
- Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697, USA
| | - Albert F Yee
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697, USA. and Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697, USA
| | - Michelle A Digman
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697, USA. and Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697, USA
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24
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Beta 2-adrenergic receptor homodimers: Role of transmembrane domain 1 and helix 8 in dimerization and cell surface expression. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:1445-1455. [PMID: 27993566 DOI: 10.1016/j.bbamem.2016.12.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 12/05/2016] [Accepted: 12/08/2016] [Indexed: 11/22/2022]
Abstract
Even though there are hundreds of reports in the published literature supporting the hypothesis that G protein-coupled receptors (GPCR) form and function as dimers this remains a highly controversial area of research and mechanisms governing homodimer formation are poorly understood. Crystal structures revealing homodimers have been reported for many different GPCR. For adrenergic receptors, a potential dimer interface involving transmembrane domain 1 (TMD1) and helix 8 (H8) was identified in crystal structures of the beta1-adrenergic (β1-AR) and β2-AR. The purpose of this study was to investigate a potential role for TMD1 and H8 in dimerization and plasma membrane expression of functional β2-AR. Charged residues at the base of TMD1 and in the distal portion of H8 were replaced, singly and in combination, with non-polar residues or residues of opposite charge. Wild type and mutant β2-AR, tagged with YFP and expressed in HEK293 cells, were evaluated for plasma membrane expression and function. Homodimer formation was evaluated using bioluminescence resonance energy transfer, bimolecular fluorescence complementation, and fluorescence correlation spectroscopy. Amino acid substitutions at the base of TMD1 and in the distal portion of H8 disrupted homodimer formation and caused receptors to be retained in the endoplasmic reticulum. Mutations in the proximal region of H8 did not disrupt dimerization but did interfere with plasma membrane expression. This study provides biophysical evidence linking a potential TMD1/H8 interface with ER export and the expression of functional β2-AR on the plasma membrane. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
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25
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Molteni M, Ferri F. Commercial counterboard for 10 ns software correlator for photon and fluorescence correlation spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:113108. [PMID: 27910545 DOI: 10.1063/1.4966983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A 10 ns time resolution, multi-tau software correlator, capable of computing simultaneous autocorrelation (A-A, B-B) and cross (A-B) correlation functions at count rates up to ∼10 MHz, with no data loss, has been developed in LabVIEW and C++ by using the National Instrument timer/counterboard (NI PCIe-6612) and a fast Personal Computer (PC) (Intel Core i7-4790 Processor 3.60 GHz ). The correlator works by using two algorithms: for large lag times (τ ≳ 1 μs), a classical time-mode scheme, based on the measure of the number of pulses per time interval, is used; differently, for τ ≲ 1 μs a photon-mode (PM) scheme is adopted and the correlation function is retrieved from the sequence of the photon arrival times. Single auto- and cross-correlation functions can be processed online in full real time up to count rates of ∼1.8 MHz and ∼1.2 MHz, respectively. Two autocorrelation (A-A, B-B) and a cross correlation (A-B) functions can be simultaneously processed in full real time only up to count rates of ∼750 kHz. At higher count rates, the online processing takes place in a delayed modality, but with no data loss. When tested with simulated correlation data and latex spheres solutions, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.
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Affiliation(s)
- Matteo Molteni
- Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, Università dell'Insubria, Via Valleggio 11, 22100 Como, Italy
| | - Fabio Ferri
- Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, Università dell'Insubria, Via Valleggio 11, 22100 Como, Italy
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26
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Qu C, Shi Y, Jing B, Gao H, Zhu Y. Probing the Inhomogeneous Charge Distribution on Annealed Polyelectrolyte Star Polymers in Dilute Aqueous Solutions. ACS Macro Lett 2016; 5:402-406. [PMID: 35614712 DOI: 10.1021/acsmacrolett.6b00111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformational structure of a polyelectrolyte chain in dilute aqueous solution is strongly coupled with its surrounding electrostatic environment. With the introduction of branched topology, the distribution of counterions in the vicinity of a polyelectrolyte chain becomes highly inhomogeneous, giving rise to complex structures of branched polyelectrolytes in dilute aqueous solution. To directly probe the local electrostatic conditions near a branched polyelectrolyte in aqueous solutions, star-shaped poly(2-vinylpyridine) (P2VP) polymers with precise labeling of one single fluorophore at different locations, for example, the star center or the terminal group of one arm, were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl-terminated P2VP macromonomers. Using fluorescence correlation spectroscopy (FCS) combined with photon counting histogram (PCH) analysis, the conformational structures and local electric potential of P2VP star polyelectrolytes were investigated in dilute aqueous solutions of varied pH at a single molecule level. Despite the same hydrodynamic radius of P2VP stars, pH-sensitive fluorophores labeled at different locations sensitively differentiated the higher electric potential at the star center from the lower electric potential at the periphery in dilute aqueous solutions.
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Affiliation(s)
| | | | - Benxin Jing
- Department
of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | | | - Yingxi Zhu
- Department
of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
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27
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Stoddart LA, Kilpatrick LE, Briddon SJ, Hill SJ. Probing the pharmacology of G protein-coupled receptors with fluorescent ligands. Neuropharmacology 2015; 98:48-57. [PMID: 25979488 DOI: 10.1016/j.neuropharm.2015.04.033] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 04/23/2015] [Accepted: 04/29/2015] [Indexed: 01/01/2023]
Abstract
G protein-coupled receptors control a wide range of physiological processes and are the target for many clinically used drugs. Understanding the way in which receptors bind agonists and antagonists, their organisation in the membrane and their regulation after agonist binding are important properties which are key to developing new drugs. One way to achieve this knowledge is through the use of fluorescent ligands, which have been used to study the expression and function of receptors in endogenously expressing systems. Fluorescent ligands with appropriate imaging properties can be used in conjunction with confocal microscopy to investigate the regulation of receptors after activation. Alternatively, through the use of single molecule microscopy, they can probe the spatial organisation of receptors within the membrane. This review focuses on the techniques in which fluorescent ligands have been used and the novel aspects of G protein-coupled receptor pharmacology which have been uncovered. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'.
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Affiliation(s)
- Leigh A Stoddart
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Laura E Kilpatrick
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Stephen J Briddon
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Stephen J Hill
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, UK
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Lowe AR, Tang JH, Yassif J, Graf M, Huang WYC, Groves JT, Weis K, Liphardt JT. Importin-β modulates the permeability of the nuclear pore complex in a Ran-dependent manner. eLife 2015; 4. [PMID: 25748139 PMCID: PMC4375889 DOI: 10.7554/elife.04052] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 02/27/2015] [Indexed: 11/13/2022] Open
Abstract
Soluble karyopherins of the importin-β (impβ) family use RanGTP to transport cargos directionally through the nuclear pore complex (NPC). Whether impβ or RanGTP regulate the permeability of the NPC itself has been unknown. In this study, we identify a stable pool of impβ at the NPC. A subpopulation of this pool is rapidly turned-over by RanGTP, likely at Nup153. Impβ, but not transportin-1 (TRN1), alters the pore's permeability in a Ran-dependent manner, suggesting that impβ is a functional component of the NPC. Upon reduction of Nup153 levels, inert cargos more readily equilibrate across the NPC yet active transport is impaired. When purified impβ or TRN1 are mixed with Nup153 in vitro, higher-order, multivalent complexes form. RanGTP dissolves the impβ•Nup153 complexes but not those of TRN1•Nup153. We propose that impβ and Nup153 interact at the NPC's nuclear face to form a Ran-regulated mesh that modulates NPC permeability. DOI:http://dx.doi.org/10.7554/eLife.04052.001 In our cells, genetic material is contained within the nucleus, which is separated from the rest of the cell by a double-layered membrane called the nuclear envelope. Within this membrane there are pores that allow proteins and other molecules to enter and exit the nucleus. Small molecules can pass through these pores unaided, which is known as ‘passive’ transport. However, larger cargos need help from transport receptor proteins in a process called ‘active’ transport. Large cargos bind to transport receptors, such as importin-β, in the cytoplasm and are then guided through the pore. Once the cargo and importin-β are inside the nucleus, a protein called RanGTP binds to importin-β to release the cargo. It is thought that importin-β and RanGTP are only important for the active transport of cargo. Here, Lowe et al. studied how importin-β interacts with the pore. The experiments show that in the absence of RanGTP, importin-β accumulates inside the pore and binds to a protein called Nup153, which is part of the complex of proteins that makes up the pore. However, when RanGTP is present, some of the importin-β is displaced from Nup153 and leaves the pore, which makes it easier for cargo to pass through. Further experiments show that when Nup153 and importin-β are mixed, they associate into a gel-like material that can be ‘melted’ by RanGTP. Lowe et al. propose a model for how RanGTP may control the flow of cargo through the nuclear pore by affecting the binding of importin-β to Nup153. Lowe et al.'s findings suggest that passive and active transport of cargo across the nuclear pore are fundamentally connected and suggest that RanGTP provides the cell with an additional layer of control over nucleocytoplasmic transport. DOI:http://dx.doi.org/10.7554/eLife.04052.002
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Affiliation(s)
- Alan R Lowe
- Institute for Structural and Molecular Biology, University College London and Birkbeck College, London, United Kingdom
| | - Jeffrey H Tang
- Department of Physics, University of California, Berkeley, Berkeley, United States
| | - Jaime Yassif
- Department of Physics, University of California, Berkeley, Berkeley, United States
| | - Michael Graf
- Section of Life Sciences and Technologies, École polytechnique fédérale de Lausanne, Lausanne, Switzerland
| | - William Y C Huang
- Department of Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Jay T Groves
- QB3, University of California, Berkeley, Berkeley, United States
| | - Karsten Weis
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Jan T Liphardt
- Department of Physics, University of California, Berkeley, Berkeley, United States
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Herrick-Davis K, Grinde E, Lindsley T, Teitler M, Mancia F, Cowan A, Mazurkiewicz JE. Native serotonin 5-HT2C receptors are expressed as homodimers on the apical surface of choroid plexus epithelial cells. Mol Pharmacol 2015; 87:660-73. [PMID: 25609374 DOI: 10.1124/mol.114.096636] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are a prominent class of plasma membrane proteins that regulate physiologic responses to a wide variety of stimuli and therapeutic agents. Although GPCR oligomerization has been studied extensively in recombinant cells, it remains uncertain whether native receptors expressed in their natural cellular environment are monomers, dimers, or oligomers. The goal of this study was to determine the monomer/oligomer status of a native GPCR endogenously expressed in its natural cellular environment. Native 5-HT2C receptors in choroid plexus epithelial cells were evaluated using fluorescence correlation spectroscopy (FCS) with photon counting histogram (PCH). An anti-5-HT2C fragment antigen binding protein was used to label native 5-HT2C receptors. A known monomeric receptor (CD-86) served as a control for decoding the oligomer status of native 5-HT2C receptors by molecular brightness analysis. FCS with PCH revealed molecular brightness values for native 5-HT2C receptors equivalent to the molecular brightness of a homodimer. 5-HT2C receptors displayed a diffusion coefficient of 5 × 10(-9) cm(2)/s and were expressed at 32 receptors/μm(2) on the apical surface of choroid plexus epithelial cells. The functional significance and signaling capabilities of the homodimer were investigated in human embryonic kidney 293 cells using agonists that bind in a wash-resistant manner to one or both protomers of the homodimer. Whereas agonist binding to one protomer resulted in G protein activation, maximal stimulation required occupancy of both protomers. This study is the first to demonstrate the homodimeric structure of 5-HT2C receptors endogenously expressed in their native cellular environment, and identifies the homodimer as a functional signaling unit.
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Ellinor Grinde
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Tara Lindsley
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Milt Teitler
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Filippo Mancia
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Ann Cowan
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
| | - Joseph E Mazurkiewicz
- Center for Neuropharmacology & Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., T.L., M.T., J.E.M.); Department of Physiology and Cellular Biophysics, Columbia University, New York, New York (F.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
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30
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Weatherill EE, Wallace MI. Combining Single-Molecule Imaging and Single-Channel Electrophysiology. J Mol Biol 2015; 427:146-57. [DOI: 10.1016/j.jmb.2014.07.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 07/07/2014] [Accepted: 07/07/2014] [Indexed: 12/29/2022]
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Ranjit S, Dvornikov A, Holland DA, Reinhart GD, Jameson DM, Gratton E. Application of three-photon excitation FCS to the study of protein oligomerization. J Phys Chem B 2014; 118:14627-31. [PMID: 25438088 PMCID: PMC4275161 DOI: 10.1021/jp511126x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
Three-photon excitation fluorescence
correlation spectroscopy was
used to detect oligomerization equilibria of rat liver phosphofructokinase.
The fluorescence intensity produced by the three-photon excitation
of tryptophan was collected using the DIVER microscope. In this home-built
upright microscope, a large area photomultiplier, placed directly
below the sample, is used as the detector. The lack of optical elements
in the microscope detection path results in a significantly improved
detection efficiency in the UV region down to about 300 nm, which
encompasses the fluorescence emission from tryptophan. The three-photon
excitation autocorrelation decays obtained for phosphofructokinase
in the presence of F6P showed the presence of large oligomers. Substitution
of F6P with ATP in the buffer medium results in dissociation of the
large oligomers, which is reported by the decreased autocorrelation
amplitude. The three-photon excitation process was verified from the
slope of the log–log plot of intensity against laser power.
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Affiliation(s)
- Suman Ranjit
- Laboratory for Fluorescence Dynamics, Biomedical Engineering, University of California, Irvine , Irvine, California 92697, United States
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32
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Youker RT, Teng H. Measuring protein dynamics in live cells: protocols and practical considerations for fluorescence fluctuation microscopy. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:90801. [PMID: 25260867 PMCID: PMC4183152 DOI: 10.1117/1.jbo.19.9.090801] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 08/12/2014] [Accepted: 07/31/2014] [Indexed: 06/03/2023]
Abstract
Quantitative analysis of protein complex stoichiometries and mobilities are critical for elucidating the mechanisms that regulate cellular pathways. Fluorescence fluctuation spectroscopy (FFS) techniques can measure protein dynamics, such as diffusion coefficients and formation of complexes, with extraordinary precision and sensitivity. Complete calibration and characterization of the microscope instrument is necessary in order to avoid artifacts during data acquisition and to capitalize on the full capabilities of FFS techniques. We provide an overview of the theory behind FFS techniques, discuss calibration procedures, provide protocols, and give practical considerations for performing FFS experiments. One important parameter recovered from FFS measurements is the relative molecular brightness that can correlate with oligomerization. Three methods for measuring molecular brightness (fluorescence correlation spectroscopy, photon-counting histogram, and number and brightness analysis) recover similar values when measuring samples under ideal conditions in vitro. However, examples are given illustrating that these different methods used for calculating molecular brightness of fluorescent molecules in cells are not always equivalent. Methods relying on spot measurements are more prone to bleaching and movement artifacts that can lead to underestimation of brightness values. We advocate for the use of multiple FFS techniques to study molecular brightnesses to overcome and compliment limitations of individual techniques.
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Affiliation(s)
- Robert T. Youker
- University of Pittsburgh School of
Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania
15261, United States
- Western Carolina University,
Department of Biology, Cullowhee, North Carolina 28723, United
States
| | - Haibing Teng
- Carnegie Mellon University,
Molecular Biosensor and Imaging Center (MBIC), Pittsburgh, Pennsylvania 15213,
United States
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33
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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: 103] [Impact Index Per Article: 10.3] [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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Anthony NR, Berland KM. τFCS: multi-method global analysis enhances resolution and sensitivity in fluorescence fluctuation measurements. PLoS One 2014; 9:e90456. [PMID: 24587370 PMCID: PMC3938748 DOI: 10.1371/journal.pone.0090456] [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: 10/04/2013] [Accepted: 02/03/2014] [Indexed: 11/18/2022] Open
Abstract
Fluorescence fluctuation methods have become invaluable research tools for characterizing the molecular-level physical and chemical properties of complex systems, such as molecular concentrations, dynamics, and the stoichiometry of molecular interactions. However, information recovery via curve fitting analysis of fluctuation data is complicated by limited resolution and challenges associated with identifying accurate fit models. We introduce a new approach to fluorescence fluctuation spectroscopy that couples multi-modal fluorescence measurements with multi-modal global curve fitting analysis. This approach yields dramatically enhanced resolution and fitting model discrimination capabilities in fluctuation measurements. The resolution enhancement allows the concentration of a secondary species to be accurately measured even when it constitutes only a few percent of the molecules within a sample mixture, an important new capability that will allow accurate measurements of molecular concentrations and interaction stoichiometry of minor sample species that can be functionally important but difficult to measure experimentally. We demonstrate this capability using τFCS, a new fluctuation method which uses simultaneous global analysis of fluorescence correlation spectroscopy and fluorescence lifetime data, and show that τFCS can accurately recover the concentrations, diffusion coefficients, lifetimes, and molecular brightness values for a two component mixture over a wide range of relative concentrations.
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Affiliation(s)
- Neil R. Anthony
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
| | - Keith M. Berland
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
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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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Golebiewska U, Zurawsky C, Scarlata S. Defining the oligomerization state of γ-synuclein in solution and in cells. Biochemistry 2014; 53:293-9. [PMID: 24367999 DOI: 10.1021/bi401479a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
γ-Synuclein is expressed at high levels in neuronal cells and in multiple invasive cancers. Like its family member α-synuclein, γ-synuclein is thought to be natively unfolded but does not readily form fibrils. The function of γ-synuclein is unknown, but we have found that it interacts strongly with the enzyme phospholipase Cβ (PLCβ), altering its interaction with G proteins. As a first step in determining its role, we have characterized its oligomerization using fluorescence homotransfer, photon-counting histogram analysis, and native gel electrophoresis. We found that when its expressed in Escherichia coli and purified, γ-synuclein appears monomeric on chromatographs under denaturing conditions, but under native conditions, it appears as oligomers of varying sizes. We followed the monomer-to-tetramer association by labeling the protein with fluorescein and following the concentration-dependent loss in fluorescence anisotropy resulting from fluorescence homotransfer. We also performed photon-counting histogram analysis at increasing concentrations of fluorescein-labeled γ-synuclein and found concentration-dependent oligomerization. Addition of PLCβ2, a strong γ-synuclein binding partner whose cellular expression is correlated with γ-synuclein, results in disruption of γ-synuclein oligomers. Similarly, its binding to lipid membranes promotes the monomer form. When we exogenously express γ-synuclein or microinject purified protein into cells, the protein appears monomeric. Our studies show that even though purified γ-synuclein form oligomers, when binding partners are present, as in cells, it dissociates to a monomer to bind these partners, which in turn may modify protein function and integrity.
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Affiliation(s)
- Urszula Golebiewska
- Department of Physiology & Biophysics, Stony Brook University , Stony Brook, New York 11794, United States
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37
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Bag N, Wohland T. Imaging fluorescence fluctuation spectroscopy: new tools for quantitative bioimaging. Annu Rev Phys Chem 2013; 65:225-48. [PMID: 24328446 DOI: 10.1146/annurev-physchem-040513-103641] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fluorescence fluctuation spectroscopy (FFS) techniques provide information at the single-molecule level with excellent time resolution. Usually applied at a single spot in a sample, they have been recently extended into imaging formats, referred to as imaging FFS. They provide spatial information at the optical diffraction limit and temporal information in the microsecond to millisecond range. This review provides an overview of the different modalities in which imaging FFS techniques have been implemented and discusses present imaging FFS capabilities and limitations. A combination of imaging FFS and nanoscopy would allow one to record information with the detailed spatial information of nanoscopy, which is ∼20 nm and limited only by fluorophore size and labeling density, and the time resolution of imaging FFS, limited by the fluorescence lifetime. This combination would provide new insights into biological events by providing spatiotemporal resolution at unprecedented levels.
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Affiliation(s)
- Nirmalya Bag
- Departments of Biological Sciences and Chemistry, and NUS Center for Bio-Imaging Sciences (CBIS), National University of Singapore, 117557 Singapore; ,
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38
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Herrick-Davis K, Grinde E, Cowan A, Mazurkiewicz JE. Fluorescence correlation spectroscopy analysis of serotonin, adrenergic, muscarinic, and dopamine receptor dimerization: the oligomer number puzzle. Mol Pharmacol 2013; 84:630-42. [PMID: 23907214 DOI: 10.1124/mol.113.087072] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The issue of G protein-coupled receptor (GPCR) oligomer status has not been resolved. Although many studies have provided evidence in favor of receptor-receptor interactions, there is no consensus as to the exact oligomer size of class A GPCRs. Previous studies have reported monomers, dimers, tetramers, and higher-order oligomers. In the present study, this issue was examined using fluorescence correlation spectroscopy (FCS) with photon counting histogram (PCH) analysis, a sensitive method for monitoring diffusion and oligomer size of plasma membrane proteins. Six different class A GPCRs were selected from the serotonin (5-HT2A), adrenergic (α1b-AR and β2-AR), muscarinic (M1 and M2), and dopamine (D1) receptor families. Each GPCR was C-terminally labeled with green fluorescent protein (GFP) or yellow fluorescent protein (YFP) and expressed in human embryonic kidney 293 cells. FCS provided plasma membrane diffusion coefficients on the order of 7.5 × 10(-9) cm(2)/s. PCH molecular brightness analysis was used to determine the GPCR oligomer size. Known monomeric (CD-86) and dimeric (CD-28) receptors with GFP and YFP tags were used as controls to determine the molecular brightness of monomers and dimers. PCH analysis of fluorescence-tagged GPCRs revealed molecular brightness values that were twice the monomeric controls and similar to the dimeric controls. Reduced χ(2) analyses of the PCH data best fit a model for a homogeneous population of homodimers, without tetramers or higher-order oligomers. The homodimer configuration was unaltered by agonist treatment and was stable over a 10-fold range of receptor expression level. The results of this study demonstrate that biogenic amine receptors freely diffusing within the plasma membrane are predominantly homodimers.
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., J.E.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
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39
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Wu B, Singer RH, Mueller JD. Time-integrated fluorescence cumulant analysis and its application in living cells. Methods Enzymol 2013; 518:99-119. [PMID: 23276537 DOI: 10.1016/b978-0-12-388422-0.00005-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Time-integrated fluorescence cumulant analysis (TIFCA) is a data analysis technique for fluorescence fluctuation spectroscopy (FFS) that extracts information from the cumulants of the integrated fluorescence intensity. It is the first exact theory that describes the effect of sampling time on FFS experiment. Rebinning of data to longer sampling times helps to increase the signal/noise ratio of the experimental cumulants of the photon counts. The sampling time dependence of the cumulants encodes both brightness and diffusion information of the sample. TIFCA analysis extracts this information by fitting the cumulants to model functions. Generalization of TIFCA to multicolor FFS experiment is straightforward. Here, we present an overview of the theory, its implementation, as well as the benefits and requirements of TIFCA. The questions of why, when, and how to use TIFCA will be discussed. We give several examples of practical applications of TIFCA, particularly focused on measuring molecular interaction in living cells.
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Affiliation(s)
- Bin Wu
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York, USA
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40
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Crevenna AH, Naredi-Rainer N, Schönichen A, Dzubiella J, Barber DL, Lamb DC, Wedlich-Söldner R. Electrostatics control actin filament nucleation and elongation kinetics. J Biol Chem 2013; 288:12102-13. [PMID: 23486468 DOI: 10.1074/jbc.m113.456327] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment.
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Affiliation(s)
- Alvaro H Crevenna
- AG Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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41
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42
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43
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Selmke M, Braun M, Schachoff R, Cichos F. Photothermal signal distribution analysis (PhoSDA). Phys Chem Chem Phys 2013; 15:4250-7. [DOI: 10.1039/c3cp44092c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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44
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Fluorescence correlation spectroscopy and photon-counting histogram analysis of receptor-receptor interactions. Methods Cell Biol 2013; 117:181-96. [PMID: 24143978 DOI: 10.1016/b978-0-12-408143-7.00010-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) performed using a laser scanning confocal microscope is a technique with single-molecule sensitivity that is becoming more accessible to cell biologists. In this chapter, we describe the use of FCS for the analysis of diffusion coefficients and receptor-receptor interactions in live cells in culture. In particular, we describe a protocol to collect fluorescence fluctuation data from fluorescence-tagged receptors as they diffuse into an out of a small laser-illuminated observation volume using a commercially available system such as the Zeiss ConfoCor 3 or LSM-780 microscope. Autocorrelation analysis of the fluctuations in fluorescence intensity provides information about the diffusion time and number of fluorescent molecules in the observation volume. A photon-counting histogram can be used to examine the relationship between fluorescence intensity and the number of fluorescent molecules to estimate the average molecular brightness of the sample. Since molecular brightness is directly proportional to the number of fluorescent molecules, it can be used to monitor receptor-receptor interactions and to decode the number of receptor monomers present in an oligomeric complex.
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45
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Wang F, Shi Y, Luo S, Chen Y, Zhao J. Conformational Transition of Poly(N-isopropylacrylamide) Single Chains in Its Cononsolvency Process: A Study by Fluorescence Correlation Spectroscopy and Scaling Analysis. Macromolecules 2012. [DOI: 10.1021/ma301780f] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fei Wang
- Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yi Shi
- Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Shuangjiang Luo
- Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yongming Chen
- Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiang Zhao
- Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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46
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Skakun VV, Engel R, Borst JW, Apanasovich VV, Visser AJWG. Simultaneous diffusion and brightness measurements and brightness profile visualization from single fluorescence fluctuation traces of GFP in living cells. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:1055-64. [PMID: 23064964 DOI: 10.1007/s00249-012-0864-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 09/12/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) and photon-counting histogram (PCH) analysis use the same experimental fluorescence intensity fluctuations, but each analytical method focuses on a different property of the signal. The time-dependent decay of the correlation of fluorescence fluctuations is measured in FCS yielding, for instance, molecular diffusion coefficients. The amplitude distribution of these fluctuations is calculated by PCH analysis yielding information about the molecular brightness of fluorescent species. Analysis of both FCS and PCH results in the molecular concentration of the sample. Using a previously described global analysis procedure we report here precise, simultaneous measurements of diffusion constants and brightness values from single fluorescence fluctuation traces of green-fluorescent protein (GFP, S65T) in the cytoplasm of Dictyostelium cells. The use of a polynomial profile in PCH analysis, describing the detected three-dimensional shape of the confocal volume, enabled us to obtain well fitting results for GFP in cells. We could visualize the polynomial profile and show its deviation from a Gaussian profile.
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Affiliation(s)
- Victor V Skakun
- Department of Systems Analysis and Computer Simulation, Belarusian State University, 220030 Minsk, Belarus.
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47
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Herrick-Davis K, Grinde E, Lindsley T, Cowan A, Mazurkiewicz JE. Oligomer size of the serotonin 5-hydroxytryptamine 2C (5-HT2C) receptor revealed by fluorescence correlation spectroscopy with photon counting histogram analysis: evidence for homodimers without monomers or tetramers. J Biol Chem 2012; 287:23604-14. [PMID: 22593582 PMCID: PMC3390635 DOI: 10.1074/jbc.m112.350249] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/05/2012] [Indexed: 11/06/2022] Open
Abstract
Fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) are techniques with single molecule sensitivity that are well suited for examining the biophysical properties of protein complexes in living cells. In the present study, FCS and PCH were applied to determine the diffusion coefficient and oligomeric size of G-protein-coupled receptors. FCS was used to record fluctuations in fluorescence intensity arising from fluorescence-tagged 5-hydroxytryptamine 2C (5-HT(2C)) receptors diffusing within the plasma membrane of HEK293 cells and rat hippocampal neurons. Autocorrelation analysis yielded diffusion coefficients ranging from 0.8 to 1.2 μm(2)/s for fluorescence-tagged receptors. Because the molecular brightness of a fluorescent protein is directly proportional to the number of fluorescent proteins traveling together within a protein complex, it can be used to determine the oligomeric size of the protein complex. FCS and PCH analysis of fluorescence-tagged 5-HT(2C) receptors provided molecular brightness values that were twice that of GFP and YFP monomeric controls, similar to a dimeric GFP control, and unaltered by 5-HT. Bimolecular fluorescence complementation of the N- and C-terminal halves of YFP attached to 5-HT(2C) receptors was observed in endoplasmic reticulum/Golgi and plasma membranes with a brightness equal to monomeric YFP. When GFP-tagged 5-HT(2C) receptors were co-expressed with a large excess of untagged, non-fluorescent 5-HT(2C) receptors, the molecular brightness was reduced by half. PCH analysis of the FCS data were best described by a one-component dimer model without monomers or tetramers. Therefore, it is concluded that 5-HT(2C) receptors freely diffusing within the plasma membrane are dimeric.
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MESH Headings
- Animals
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Cells, Cultured
- Diffusion/drug effects
- Endoplasmic Reticulum/metabolism
- Fluorescence
- Golgi Apparatus/metabolism
- Green Fluorescent Proteins/chemistry
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- HEK293 Cells
- Hippocampus/cytology
- Humans
- Luminescent Proteins/chemistry
- Luminescent Proteins/genetics
- Luminescent Proteins/metabolism
- Microscopy, Confocal
- Mutation
- Neurons/cytology
- Neurons/drug effects
- Neurons/metabolism
- Protein Multimerization
- Protein Transport/drug effects
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2C/chemistry
- Receptor, Serotonin, 5-HT2C/genetics
- Receptor, Serotonin, 5-HT2C/metabolism
- Serotonin/pharmacology
- Spectrometry, Fluorescence/methods
- Transfection
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA.
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48
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Xu Q, Lin WC, Petit RS, Groves JT. EphA2 receptor activation by monomeric Ephrin-A1 on supported membranes. Biophys J 2012; 101:2731-9. [PMID: 22261062 DOI: 10.1016/j.bpj.2011.10.039] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 10/07/2011] [Accepted: 10/31/2011] [Indexed: 01/22/2023] Open
Abstract
The receptor tyrosine kinase EphA2 interacts with its glycosylphosphatidylinositol (GPI)-linked ephrin-A1 ligand in a juxtacrine configuration. The soluble ephrin-A1 protein, without its GPI membrane linker, fails to activate EphA2. However, preclustered ephrin-A1 protein is active in solution and has been frequently used to trigger the EphA2 receptor. Although this approach has yielded insights into EphA2 signaling, preclustered ligands bypass natural receptor clustering processes and thus mask any role of clustering as a signal regulatory mechanism. Here, we present EphA2-expressing cells with a fusion protein of monomeric ephrin-A1 (mEA1) and enhanced monomeric yellow fluorescent protein that is linked to a supported lipid bilayer via a nickel-decahistidine anchor. The mEA1 is homogeneously dispersed, laterally mobile, and monomeric as measured by fluorescence imaging, correlation spectroscopy, and photon counting histogram analysis, respectively. Ephrin-A1 presented in this manner activates EphA2 on the surface of MDA-MB-231 human breast cancer cells, as measured by EphA2 phosphorylation and degradation. Spatial mutation experiments in which nanopatterns on the underlying substrate restrict mEA1 movement in the supported lipid bilayer reveal spatio-mechanical regulation of this signaling pathway, consistent with recently reported observations using a synthetically cross-linked ephrin-A1 dimer.
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Affiliation(s)
- Qian Xu
- Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California, USA
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49
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Abstract
Molecular interactions are at the origin of life. How molecules get at different locations in the cell and how they locate their partners is a major and partially unresolved question in biology that is paramount to signaling. Spatio-temporal correlations of fluctuating fluorescently tagged molecules reveal how they move, interact, and bind in the different cellular compartments. Methods based on fluctuations represent a remarkable technical advancement in biological imaging. Here we discuss image analysis methods based on spatial and temporal correlation of fluctuations, raster image correlation spectroscopy, number and brightness, and spatial cross-correlations that give us information about how individual molecules move in cells and interact with partners at the single molecule level. These methods can be implemented with a standard laser scanning microscope and produce a cellular level spatio-temporal map of molecular interactions.
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Affiliation(s)
- Michelle A Digman
- Laboratory for Fluorescence Dynamics, University of California, Irvine, CA, USA.
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50
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Skinner JP, Chi L, Ozeata PF, Ramsay CS, O'Hara RL, Calfin BB, Tetin SY. Introduction of the mass spread function for characterization of protein conjugates. Anal Chem 2011; 84:1172-7. [PMID: 22128896 DOI: 10.1021/ac202239j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Traditionally, characterization of protein molecules conjugated with molecular probes is performed by UV-vis spectroscopy. This method determines the average incorporation ratio but does not yield information about the label distribution. Electrospray ionization mass spectroscopy (ESI-MS) allows direct measurement of the fraction of protein containing a given number of labels. However, for a glycosylated protein, this analysis can be severely limited due to spectral overlap of the labels and carbohydrates. To address this problem, we introduce the mass spread function (MSF) for conjugation analysis. By treating the ESI-MS spectrum of conjugated protein as the spectrum before conjugation convolved with the MSF, we are able to quantify the labeled protein population using a binomial distribution function. We first applied this procedure for characterization of labeled antibody F(ab')(2) fragments which do not contain carbohydrates. We then apply the MSF to fit spectra of entire conjugated monoclonal antibodies and quantify the distribution of labels in the presence of glycans.
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Affiliation(s)
- Joseph P Skinner
- Diagnostics Research, Abbott Diagnostics Division, 100 Abbott Park Road, Abbott Park, Illinois 60064, United States
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