1
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Silwane B, Wilson M, Kataky R. An Electrochemistry and Computational Study at an Electrified Liquid-Liquid Interface for Studying Beta-Amyloid Aggregation. MEMBRANES 2023; 13:584. [PMID: 37367788 DOI: 10.3390/membranes13060584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/22/2023] [Accepted: 05/29/2023] [Indexed: 06/28/2023]
Abstract
Amphiphilic peptides, such as Aß amyloids, can adsorb at an interface between two immiscible electrolyte solutions (ITIES). Based on previous work (vide infra), a hydrophilic/hydrophobic interface is used as a simple biomimetic system for studying drug interactions. The ITIES provides a 2D interface to study ion-transfer processes associated with aggregation, as a function of Galvani potential difference. Here, the aggregation/complexation behaviour of Aβ(1-42) is studied in the presence of Cu (II) ions, together with the effect of a multifunctional peptidomimetic inhibitor (P6). Cyclic and differential pulse voltammetry proved to be particularly sensitive to the detection of the complexation and aggregation of Aβ(1-42), enabling estimations of changes in lipophilicity upon binding to Cu (II) and P6. At a 1:1 ratio of Cu (II):Aβ(1-42), fresh samples showed a single DPV (Differential Pulse Voltammetry) peak half wave transfer potential (E1/2) at 0.40 V. Upon increasing the ratio of Cu (II) two-fold, fluctuations were observed in the DPVs, indicating aggregation. The approximate stoichiometry and binding properties of Aβ(1-42) during complexation with Cu (II) were determined by performing a differential pulse voltammetry (DPV) standard addition method, which showed two binding regimes. A pKa of 8.1 was estimated, with a Cu:Aβ1-42 ratio~1:1.7. Studies using molecular dynamics simulations of peptides at the ITIES show that Aβ(1-42) strands interact through the formation of β-sheet stabilised structures. In the absence of copper, binding/unbinding is dynamic, and interactions are relatively weak, leading to the observation of parallel and anti-parallel arrangements of β-sheet stabilised aggregates. In the presence of copper ions, strong binding occurs between a copper ion and histidine residues on two peptides. This provides a convenient geometry for inducing favourable interactions between folded β-sheet structures. Circular Dichroism spectroscopy (CD spectroscopy) was used to support the aggregation behaviour of the Aβ(1-42) peptides following the addition of Cu (II) and P6 to the aqueous phase.
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Affiliation(s)
- Bongiwe Silwane
- Department of Chemistry, Durham University, Durham DH1 3LE, UK
| | - Mark Wilson
- Department of Chemistry, Durham University, Durham DH1 3LE, UK
| | - Ritu Kataky
- Department of Chemistry, Durham University, Durham DH1 3LE, UK
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2
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Watabe M, Yoshimura H, Arjunan SNV, Kaizu K, Takahashi K. Signaling activations through G-protein-coupled-receptor aggregations. Phys Rev E 2020; 102:032413. [PMID: 33076007 DOI: 10.1103/physreve.102.032413] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 08/31/2020] [Indexed: 06/11/2023]
Abstract
Eukaryotic cells transmit extracellular signal information to cellular interiors through the formation of a ternary complex made up of a ligand (or agonist), G-protein, and G-protein-coupled receptor (GPCR). Previously formalized theories of ternary complex formation have mainly assumed that observable states of receptors can only take the form of monomers. Here, we propose a multiary complex model of GPCR signaling activations via the vector representation of various unobserved aggregated receptor states. Our results from model simulations imply that receptor aggregation processes can govern cooperative effects in a regime inaccessible by previous theories. In particular, we show how the affinity of ligand-receptor binding can be largely varied by various oligomer formations in the low concentration range of G-protein stimulus.
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Affiliation(s)
- Masaki Watabe
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Hideaki Yoshimura
- School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Satya N V Arjunan
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Lowy Cancer Research Centre, The University of New South Wales, Sydney 2052, Australia
| | - Kazunari Kaizu
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Koichi Takahashi
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa 252-8520, Japan
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3
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Watabe M, Arjunan SNV, Chew WX, Kaizu K, Takahashi K. Cooperativity transitions driven by higher-order oligomer formations in ligand-induced receptor dimerization. Phys Rev E 2019; 100:062407. [PMID: 31962468 DOI: 10.1103/physreve.100.062407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Indexed: 06/10/2023]
Abstract
While cooperativity in ligand-induced receptor dimerization has been linked with receptor-receptor couplings via minimal representations of physical observables, effects arising from higher-order oligomer, e.g., trimer and tetramer, formations of unobserved receptors have received less attention. Here we propose a dimerization model of ligand-induced receptors in multivalent form representing physical observables under basis vectors of various aggregated receptor states. Our simulations of multivalent models not only reject Wofsy-Goldstein parameter conditions for cooperativity, but show that higher-order oligomer formations can shift cooperativity from positive to negative.
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Affiliation(s)
- Masaki Watabe
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Satya N V Arjunan
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Lowy Cancer Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Wei Xiang Chew
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Physics Department, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Kazunari Kaizu
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Koichi Takahashi
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa 252-8520, Japan
- Department of Biosciences and Informatics, Keio University, Yokohama, Kanagawa 223-8522, Japan
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4
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Watabe M, Arjunan SNV, Chew WX, Kaizu K, Takahashi K. Simulation of live-cell imaging system reveals hidden uncertainties in cooperative binding measurements. Phys Rev E 2019; 100:010402. [PMID: 31499827 DOI: 10.1103/physreve.100.010402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Indexed: 06/10/2023]
Abstract
We propose a computational method to quantitatively evaluate the systematic uncertainties that arise from undetectable sources in biological measurements using live-cell imaging techniques. We then demonstrate this method in measuring the biological cooperativity of molecular binding networks, in particular, ligand molecules binding to cell-surface receptor proteins. Our results show how the nonstatistical uncertainties lead to invalid identifications of the measured cooperativity. Through this computational scheme, the biological interpretation can be more objectively evaluated and understood under a specific experimental configuration of interest.
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Affiliation(s)
- Masaki Watabe
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Satya N V Arjunan
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Lowy Cancer Research Centre, The University of New South Wales, Sydney, Australia
| | - Wei Xiang Chew
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Physics Department, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Kazunari Kaizu
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
| | - Koichi Takahashi
- Laboratory for Biologically Inspired Computing, RIKEN Center for Biosystems Dynamics Research, Suita, Osaka 565-0874, Japan
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa 252-8520, Japan
- Department of Biosciences and Informatics, Keio University, Yokohama, Kanagawa 223-8522, Japan
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6
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Carbohydrate-dependent binding of langerin to SodC, a cell wall glycoprotein of Mycobacterium leprae. J Bacteriol 2014; 197:615-25. [PMID: 25422308 DOI: 10.1128/jb.02080-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Langerhans cells participate in the immune response in leprosy by their ability to activate T cells that recognize the pathogen, Mycobacterium leprae, in a langerin-dependent manner. We hypothesized that langerin, the distinguishing C-type lectin of Langerhans cells, would recognize the highly mannosylated structures in pathogenic Mycobacterium spp. The coding region for the extracellular and neck domain of human langerin was cloned and expressed to produce a recombinant active trimeric form of human langerin (r-langerin). Binding assays performed in microtiter plates, by two-dimensional (2D) Western blotting, and by surface plasmon resonance demonstrated that r-langerin possessed carbohydrate-dependent affinity to glycoproteins in the cell wall of M. leprae. This lectin, however, yielded less binding to mannose-capped lipoarabinomannan (ManLAM) and even lower levels of binding to phosphatidylinositol mannosides. However, the superoxide dismutase C (SodC) protein of the M. leprae cell wall was identified as a langerin-reactive ligand. Tandem mass spectrometry verified the glycosylation of a recombinant form of M. leprae SodC (rSodC) produced in Mycobacterium smegmatis. Analysis of r-langerin affinity by surface plasmon resonance revealed a carbohydrate-dependent affinity of rSodC (equilibrium dissociation constant [KD] = 0.862 μM) that was 20-fold greater than for M. leprae ManLAM (KD = 18.69 μM). These data strongly suggest that a subset of the presumptively mannosylated M. leprae glycoproteins act as ligands for langerin and may facilitate the interaction of M. leprae with Langerhans cells.
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Gutenkunst RN, Coombs D, Starr T, Dustin ML, Goldstein B. A biophysical model of cell adhesion mediated by immunoadhesin drugs and antibodies. PLoS One 2011; 6:e19701. [PMID: 21629715 PMCID: PMC3100730 DOI: 10.1371/journal.pone.0019701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 04/07/2011] [Indexed: 12/29/2022] Open
Abstract
A promising direction in drug development is to exploit the ability of natural killer cells to kill antibody-labeled target cells. Monoclonal antibodies and drugs designed to elicit this effect typically bind cell-surface epitopes that are overexpressed on target cells but also present on other cells. Thus it is important to understand adhesion of cells by antibodies and similar molecules. We present an equilibrium model of such adhesion, incorporating heterogeneity in target cell epitope density, nonspecific adhesion forces, and epitope immobility. We compare with experiments on the adhesion of Jurkat T cells to bilayers containing the relevant natural killer cell receptor, with adhesion mediated by the drug alefacept. We show that a model in which all target cell epitopes are mobile and available is inconsistent with the data, suggesting that more complex mechanisms are at work. We hypothesize that the immobile epitope fraction may change with cell adhesion, and we find that such a model is more consistent with the data, although discrepancies remain. We also quantitatively describe the parameter space in which binding occurs. Our model elaborates substantially on previous work, and our results offer guidance for the refinement of therapeutic immunoadhesins. Furthermore, our comparison with data from Jurkat T cells also points toward mechanisms relating epitope immobility to cell adhesion.
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Affiliation(s)
- Ryan N. Gutenkunst
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
| | - Daniel Coombs
- Department of Mathematics and Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Toby Starr
- Department of Pathology, New York University School of Medicine and Program in Molecular Pathogenesis, Skirball Institute of Biomolecular Medicine, New York, New York, United States of America
| | - Michael L. Dustin
- Department of Pathology, New York University School of Medicine and Program in Molecular Pathogenesis, Skirball Institute of Biomolecular Medicine, New York, New York, United States of America
| | - Byron Goldstein
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
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8
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Mayawala K, Vlachos DG, Edwards JS. The role of reaction engineering in cancer biology: Bio-imaging informatics reveals implications of the plasma membrane heterogeneities. Chem Eng Sci 2007. [DOI: 10.1016/j.ces.2007.01.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Özcan F, Klein P, Lemmon MA, Lax I, Schlessinger J. On the nature of low- and high-affinity EGF receptors on living cells. Proc Natl Acad Sci U S A 2006; 103:5735-40. [PMID: 16571657 PMCID: PMC1458642 DOI: 10.1073/pnas.0601469103] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The small subpopulation of high-affinity EGF receptors (EGFRs) on living cells revealed by Scatchard analysis of (125)I-EGF binding results was discovered nearly three decades ago, yet not much is known about the underlying mechanism. After the determination of the structure of different forms of EGFR extracellular domain it was proposed that the monomeric tethered configuration corresponds to the majority of low-affinity receptors, whereas the extended dimeric configuration corresponds to the minority of the high-affinity class of EGFRs. Mathematical modeling of EGF-binding experiments to different conformational mutants of EGFR has shown that the high-affinity class of EGFR on living cells does not correspond to the extended configuration of EGFR and can only be accounted for by including in the mathematical model an additional binding event that is attributed to the dynamic nature of EGFR on living cells. To circumvent this problem we have performed similar experiments in the background of an EGFR mutant that does not form high-affinity sites. Quantitative analysis and mathematical modeling of these data show that release of the intramolecular tether causes a 2-fold increase in EGF-binding affinity, whereas elimination of the dimerization arm reduces EGF-binding affinity by approximately 6-fold. These experiments confirm the salient features of the structural model for EGFR regulation and argue further that the intramolecular tether provides only limited autoinhibitory control of EGFR activity and that the low-affinity class of EGF-binding sites on living cells reflects interconverting, tethered, and extended receptor configurations.
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Affiliation(s)
- Ferruh Özcan
- *Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520; and
| | - Peter Klein
- *Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520; and
| | - Mark A. Lemmon
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6059
| | - Irit Lax
- *Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520; and
| | - Joseph Schlessinger
- *Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520; and
- To whom correspondence should be addressed. E-mail:
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10
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Mayawala K, Vlachos DG, Edwards JS. Heterogeneities in EGF receptor density at the cell surface can lead to concave up scatchard plot of EGF binding. FEBS Lett 2005; 579:3043-7. [PMID: 15896781 DOI: 10.1016/j.febslet.2005.04.059] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Revised: 03/30/2005] [Accepted: 04/12/2005] [Indexed: 11/18/2022]
Abstract
The mechanism responsible for the concave up nature of the Scatchard plot of epidermal growth factor (EGF) binding on EGF receptor (EGFR) has been a controversial issue for more than a decade. Past efforts to mechanistically simulate the concave up nature of the Scatchard plot of EGF binding have shown that negative cooperativity in EGF binding on an EGFR dimer or inclusion of some external site or binding event can describe this behavior. However, herein we show that heterogeneity in the density of EGFR due to localization in certain regions of the plasma membrane, which has been experimentally reported, can also lead to concave up shape of the Scatchard plot of the EGF binding on EGFR.
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Affiliation(s)
- Kapil Mayawala
- Department of Chemical Engineering, University of Delaware, 150 Academy Street, Newark, DE 19716, USA
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11
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Mattoon D, Klein P, Lemmon MA, Lax I, Schlessinger J. The tethered configuration of the EGF receptor extracellular domain exerts only a limited control of receptor function. Proc Natl Acad Sci U S A 2004; 101:923-8. [PMID: 14732693 PMCID: PMC327118 DOI: 10.1073/pnas.0307286101] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Quantitative epidermal growth factor (EGF)-binding experiments have shown that the EGF-receptor (EGFR) is displayed on the surface of intact cells in two forms, a minority of high-affinity and a majority of low-affinity EGFRs. On the basis of the three-dimensional structure of the extracellular ligand binding domain of the EGFR, it was proposed that the intramolecularly tethered and autoinhibited configuration corresponds to the low-affinity receptor, whereas the extended configuration accounts for the high-affinity EGFRs on intact cells. Here we test this model by analyzing the properties of EGFRs mutated in the specific regions responsible for receptor autoinhibition and dimerization, respectively. Our results show that mutagenic disruption of the autoinhibitory tether in EGFR results in a decrease in the dissociation rate of EGF without a detectable change in EGFR activation and signaling through EGFR even in response to stimulation with low concentrations of EGF. Mutagenic disruption of the dimerization arm, on the other hand, increased the rate of EGF dissociation and impaired EGFR activation and signaling via the EGFR. This study demonstrates that the extended configuration of EGFR does not account for the apparent high-affinity EGF-binding to EGFR on intact cells. Furthermore, the autoinhibition conferred by the tethered configuration of the extracellular ligand-binding domain provides only a limited control of EGFR function.
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Affiliation(s)
- Dawn Mattoon
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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12
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Klein P, Mattoon D, Lemmon MA, Schlessinger J. A structure-based model for ligand binding and dimerization of EGF receptors. Proc Natl Acad Sci U S A 2004; 101:929-34. [PMID: 14732694 PMCID: PMC327119 DOI: 10.1073/pnas.0307285101] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
On the basis of the 3D structures of the extracellular ligand-binding domains of the epidermal growth factor (EGF) receptor (EGFR) and ErbB3, a mechanism has been proposed for how the extracellular region of the EGFR is maintained in an autoinhibited configuration and for how EGF binding induces EGFR dimerization and activation. We have attempted to derive a mathematical model for EGF binding to the EGFR and for ligand-induced receptor dimerization and activation that uses this structural information and can explain the characteristic concave-up curvilinear Scatchard plots seen when EGF binding to intact EGFR is studied in living cells. We show that these curvilinear plots cannot be accounted for by simply ascribing different affinities to the autoinhibited and extended (dimeric) configurations of the receptor seen in structural studies. Concave-up plots can only be obtained by including in the mathematical model an additional binding event in which occupied EGFR dimers bind to an "external site." The external site may represent receptor interactions with coated-pit regions in the cell membrane or with other cellular components involved in receptor endocytosis and turnover. We conclude in this study and in the accompanying article that the active extended EGFR configuration binds EGF 5- to 20-fold more strongly than the autoinhibited monomeric receptor configuration. However, these extended receptors do not correspond directly with the "high-affinity" EGF-binding sites seen in EGF-binding studies on intact cells.
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Affiliation(s)
- Peter Klein
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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13
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Bolander FF. Kinetics. Mol Endocrinol 2004. [DOI: 10.1016/b978-012111232-5/50005-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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14
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Raguin O, Gruaz-Guyon A, Barbet J. Equilibrium expert: an add-in to Microsoft Excel for multiple binding equilibrium simulations and parameter estimations. Anal Biochem 2002; 310:1-14. [PMID: 12413467 DOI: 10.1016/s0003-2697(02)00289-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An add-in to Microsoft Excel was developed to simulate multiple binding equilibriums. A partition function, readily written even when the equilibrium is complex, describes the experimental system. It involves the concentrations of the different free molecular species and of the different complexes present in the experiment. As a result, the software is not restricted to a series of predefined experimental setups but can handle a large variety of problems involving up to nine independent molecular species. Binding parameters are estimated by nonlinear least-square fitting of experimental measurements as supplied by the user. The fitting process allows user-defined weighting of the experimental data. The flexibility of the software and the way it may be used to describe common experimental situations and to deal with usual problems such as tracer reactivity or nonspecific binding is demonstrated by a few examples. The software is available free of charge upon request.
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Affiliation(s)
- Olivier Raguin
- CNRS GDR 2352, Immunociblage des tumeurs, Marseille, France
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16
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Junghans RP. Cruel antibody fictions! Cellular antigen enumeration by 'saturation' binding. IMMUNOLOGY TODAY 1999; 20:401-6. [PMID: 10532789 DOI: 10.1016/s0167-5699(97)01178-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- R P Junghans
- Dept of Medicine and Committee on Immunology, Harvard Institute of Human Genetics, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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17
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Abstract
Exogenous electric fields induce cellular responses including redistribution of integral membrane proteins, reorganization of microfilament structures, and changes in intracellular calcium ion concentration ([Ca2+]i). Although increases in [Ca2+]i caused by application of direct current electric fields have been documented, quantitative measurements of the effects of alternating current (ac) electric fields on [Ca2+]i are lacking and the Ca2+ pathways that mediate such effects remain to be identified. Using epifluorescence microscopy, we have examined in a model cell type the [Ca2+]i response to ac electric fields. Application of a 1 or 10 Hz electric field to human hepatoma (Hep3B) cells induces a fourfold increase in [Ca2+]i (from 50 nM to 200 nM) within 30 min of continuous field exposure. Depletion of Ca2+ in the extracellular medium prevents the electric field-induced increase in [Ca2+]i, suggesting that Ca2+ influx across the plasma membrane is responsible for the [Ca2+]i increase. Incubation of cells with the phospholipase C inhibitor U73122 does not inhibit ac electric field-induced increases in [Ca2+]i, suggesting that receptor-regulated release of intracellular Ca2+ is not important for this effect. Treatment of cells with either the stretch-activated cation channel inhibitor GdCl3 or the nonspecific calcium channel blocker CoCl2 partially inhibits the [Ca2+]i increase induced by ac electric fields, and concomitant treatment with both GdCl3 and CoCl2 completely inhibits the field-induced [Ca2+]i increase. Since neither Gd3+ nor Co2+ is efficiently transported across the plasma membrane, these data suggest that the increase in [Ca2+]i induced by ac electric fields depends entirely on Ca2+ influx from the extracellular medium.
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Affiliation(s)
- M R Cho
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, Massachusetts 02115, USA
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18
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Leigh BR, Burke PA, Hong AM, O'Donnell RT, Howell LP, Miers LA, DeNardo GL, DeNardo SJ. Preclinical evaluation of chimeric L6 antibody for the treatment of Kaposi's sarcoma with radioimmunotherapy. Cancer Biother Radiopharm 1999; 14:113-9. [PMID: 10850294 DOI: 10.1089/cbr.1999.14.113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
L6 is a murine IgG2a monoclonal antibody with panadenocarcinoma reactivity. Chimeric L6 (ChL6), the variable region of murine L6 combined with a human IgG1 constant region, has been used in clinical trials for the delivery of radioimmunotherapy to patients with breast cancer. AIDS-associated Kaposi's sarcoma (KS), a malignancy of vascular endothelium, may be an excellent candidate for systemic radioimmunotherapy because KS is well vascularized and radioresponsive. Because ChL6 has been noted to bind vascular endothelium, our hypothesis was that ChL6 will recognize and bind KS tumors making this a potentially useful antibody for the treatment of KS with radioimmunotherapy. To test this hypothesis, 4 human KS spindle cell cultures established from cutaneous punch biopsy specimens (KS-MR, KS-NO, KS-JD and KS 6-3E) and one well-characterized human KS cell line (KS Y-1) were assessed for L6 immunoreactivity. All 5 cell cultures were L6 positive by immunohistochemistry. KS Y-1 cells grown as nude mouse xenografts were also L6 positive by immunohistochemistry. Competitive binding assays performed on the KS Y-1 and KS 6-3E cell cultures showed high density and high affinity cell binding. Biodistribution experiments performed on nude mice with KS Y-1 xenografts demonstrate tumor targeting by ChL6. These findings indicate that ChL6 may be a useful antibody for the radioimmunotherapy of KS. Future experiments will assess the therapeutic efficacy of radiolabeled ChL6 with and without concurrent systemic radiosensitizing chemotherapy.
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MESH Headings
- Acquired Immunodeficiency Syndrome/complications
- Adenocarcinoma/immunology
- Animals
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal/pharmacokinetics
- Antibodies, Monoclonal/therapeutic use
- Antibodies, Neoplasm/immunology
- Antibodies, Neoplasm/therapeutic use
- Binding, Competitive
- Female
- Humans
- Immunoconjugates/immunology
- Immunoconjugates/pharmacokinetics
- Immunoconjugates/therapeutic use
- Immunoglobulin G/immunology
- Immunoglobulin G/therapeutic use
- Iodine Radioisotopes/therapeutic use
- Mice
- Mice, Inbred BALB C
- Mice, Nude
- Radioimmunotherapy
- Recombinant Fusion Proteins/immunology
- Recombinant Fusion Proteins/pharmacokinetics
- Recombinant Fusion Proteins/therapeutic use
- Sarcoma, Kaposi/radiotherapy
- Tissue Distribution
- Transplantation, Heterologous
- Tumor Cells, Cultured/immunology
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Affiliation(s)
- B R Leigh
- Department of Radiation Oncology, University of California, Davis, Medical Center, Sacramento 95817, USA.
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19
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Whitty A, Raskin N, Olson DL, Borysenko CW, Ambrose CM, Benjamin CD, Burkly LC. Interaction affinity between cytokine receptor components on the cell surface. Proc Natl Acad Sci U S A 1998; 95:13165-70. [PMID: 9789059 PMCID: PMC23746 DOI: 10.1073/pnas.95.22.13165] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The anti-common gamma chain (gammac) mAb CP.B8 is shown to inhibit interleukin 4 (IL-4)-dependent proliferation of phytohemagglutinin (PHA) activated T cells noncompetitively with respect to cytokine by blocking the IL-4-induced heterodimerization of IL-4Ralpha and gammac receptor chains. Affinities for the binding of IL-4 to Cos-7 cells transfected with huIL-4Ralpha, and to PHA blasts expressing both IL-4Ralpha and gammac, were used to estimate the affinity of the key interaction between gammac and the binary IL-4Ralpha.IL-4 complex on the cell surface. This affinity was defined in terms of the dimensionless ratio [IL-4Ralpha.IL-4.gammac]/[IL-4Ralpha.IL-4], which we designate KR. The results show that on PHA blasts this interaction is relatively weak; KR approximately 9, implying that approximately 10% of the limiting IL-4Ralpha chain remains free of gammac even at saturating concentrations of IL-4. This quantitative treatment establishes KR as a key measure of the coupling between ligand binding and receptor activation, providing a basis for functional distinctions between different receptors that are activated by ligand-induced receptor dimerization.
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Affiliation(s)
- A Whitty
- Biogen, Inc., 14 Cambridge Center, Cambridge, MA 02142, USA
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Strohner P, Sarrach D, Reich JG. Use of a modified binding model for the investigation of affinity dependence on antibody concentration in immunoassay systems. J Immunol Methods 1997; 203:113-22. [PMID: 9149804 DOI: 10.1016/s0022-1759(97)00022-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Affinity parameters obtained from standard calibration curves of radioimmunoassays (RIA) have been shown to decrease with increasing antibody concentration. A modified binding model was introduced in which not only binding capacity but also affinity was influenced by the antibody concentration. This allows a consistent overall description of RIA standards and titration curves for the characterization of binding assays.
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Sulzer B, Perelson AS. Equilibrium binding of multivalent ligands to cells: effects of cell and receptor density. Math Biosci 1996; 135:147-85. [PMID: 8768219 DOI: 10.1016/0025-5564(96)00022-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We study the equilibrium binding properties of multivalent ligands to cell surface receptors. We examine the effects of cell density and number of receptors per cell, that is, receptor concentration, on ligand binding. These parameters can significantly affect the formation of receptor aggregates and cross-links. We then use our general results to show that ligand-induced cell proliferation may be self-limiting, since ligand depletion reduces the signal received by individual cells once the cell population has expanded. We discuss the concept of avidity and show its limitations. As a specific example, we examine the binding of haptenated polymers to B cells and reinterpret experiments related to the immunon theory of B-cell activation.
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Affiliation(s)
- B Sulzer
- Los Alamos National Laboratory, New Mexico 87545, USA
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Bolander FF. Kinetics. Mol Endocrinol 1994. [DOI: 10.1016/b978-0-12-111231-8.50009-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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