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Karl K, Del Piccolo N, Light T, Roy T, Dudeja P, Ursachi VC, Fafilek B, Krejci P, Hristova K. Ligand bias underlies differential signaling of multiple FGFs via FGFR1. eLife 2024; 12:RP88144. [PMID: 38568193 PMCID: PMC10990489 DOI: 10.7554/elife.88144] [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] [Indexed: 04/05/2024] Open
Abstract
The differential signaling of multiple FGF ligands through a single fibroblast growth factor (FGF) receptor (FGFR) plays an important role in embryonic development. Here, we use quantitative biophysical tools to uncover the mechanism behind differences in FGFR1c signaling in response to FGF4, FGF8, and FGF9, a process which is relevant for limb bud outgrowth. We find that FGF8 preferentially induces FRS2 phosphorylation and extracellular matrix loss, while FGF4 and FGF9 preferentially induce FGFR1c phosphorylation and cell growth arrest. Thus, we demonstrate that FGF8 is a biased FGFR1c ligand, as compared to FGF4 and FGF9. Förster resonance energy transfer experiments reveal a correlation between biased signaling and the conformation of the FGFR1c transmembrane domain dimer. Our findings expand the mechanistic understanding of FGF signaling during development and bring the poorly understood concept of receptor tyrosine kinase ligand bias into the spotlight.
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Affiliation(s)
- Kelly Karl
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins UniversityBaltimoreUnited States
| | - Nuala Del Piccolo
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins UniversityBaltimoreUnited States
| | - Taylor Light
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins UniversityBaltimoreUnited States
| | - Tanaya Roy
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins UniversityBaltimoreUnited States
| | - Pooja Dudeja
- Department of Biology, Faculty of Medicine, Masaryk UniversityBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
| | - Vlad-Constantin Ursachi
- Department of Biology, Faculty of Medicine, Masaryk UniversityBrnoCzech Republic
- International Clinical Research Center, St. Anne's University HospitalBrnoCzech Republic
| | - Bohumil Fafilek
- Department of Biology, Faculty of Medicine, Masaryk UniversityBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
- International Clinical Research Center, St. Anne's University HospitalBrnoCzech Republic
| | - Pavel Krejci
- Department of Biology, Faculty of Medicine, Masaryk UniversityBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
- International Clinical Research Center, St. Anne's University HospitalBrnoCzech Republic
| | - Kalina Hristova
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins UniversityBaltimoreUnited States
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McKenzie DM, Wirth D, Pogorelov TV, Hristova K. Utility of FRET in studies of membrane protein oligomerization: The concept of the effective dissociation constant. Biophys J 2023; 122:4113-4120. [PMID: 37735871 PMCID: PMC10598290 DOI: 10.1016/j.bpj.2023.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 08/07/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023] Open
Abstract
The activity of many membrane receptors is controlled through their lateral association into dimers or higher-order oligomers. Although Förster resonance energy transfer (FRET) measurements have been used extensively to characterize the stability of receptor dimers, the utility of FRET in studies of larger oligomers has been limited. Here we introduce an effective equilibrium dissociation constant that can be extracted from FRET measurements for EphA2, a receptor tyrosine kinase (RTK) known to form active oligomers of heterogeneous distributions in response to its ligand ephrinA1-Fc. The newly introduced effective equilibrium dissociation constant has a well-defined physical meaning and biological significance. It denotes the receptor concentration for which half of the receptors are monomeric and inactive, and the other half are associated into oligomers and are active, irrespective of the exact oligomer size. This work introduces a new dimension to the utility of FRET in studies of membrane receptor association and signaling in the plasma membrane.
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Affiliation(s)
- Daniel M McKenzie
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, Maryland
| | - Daniel Wirth
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, Maryland
| | - Taras V Pogorelov
- Department of Chemistry, Center for Biophysics and Quantitative Biology, School of Chemical Sciences, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, Maryland.
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Stoneman MR, Raicu V. Fluorescence-Based Detection of Proteins and Their Interactions in Live Cells. J Phys Chem B 2023. [PMID: 37205844 DOI: 10.1021/acs.jpcb.3c01419] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Recent advances in fluorescence-based microscopy techniques, such as single molecule fluorescence, Förster resonance energy transfer (FRET), fluorescence intensity fluctuations analysis, and super-resolution microscopy have expanded our ability to study proteins in greater detail within their native cellular environment and to investigate the roles that protein interactions play in biological functions, such as inter- and intracellular signaling and cargo transport. In this Perspective, we provide an up-to-date overview of the current state of the art in fluorescence-based detection of proteins and their interactions in living cells with an emphasis on recent developments that have facilitated the characterization of the spatial and temporal organization of proteins into oligomeric complexes in the presence and absence of natural and artificial ligands. Further advancements in this field will only deepen our understanding of the underlying mechanisms of biological processes and help develop new therapeutic targets.
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Affiliation(s)
- Michael R Stoneman
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Valerică Raicu
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
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Zapata-Mercado E, Biener G, McKenzie DM, Wimley WC, Pasquale EB, Raicu V, Hristova K. The efficacy of receptor tyrosine kinase EphA2 autophosphorylation increases with EphA2 oligomer size. J Biol Chem 2022; 298:102370. [PMID: 35970390 PMCID: PMC9512837 DOI: 10.1016/j.jbc.2022.102370] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 08/09/2022] [Accepted: 08/10/2022] [Indexed: 11/30/2022] Open
Abstract
The receptor tyrosine kinase (RTK) EphA2 is expressed in epithelial and endothelial cells and controls the assembly of cell-cell junctions. EphA2 has also been implicated in many diseases, including cancer. Unlike most RTKs, which signal predominantly as dimers, EphA2 readily forms high-order oligomers upon ligand binding. Here, we investigated if a correlation exists between EphA2 signaling properties and the size of the EphA2 oligomers induced by multiple ligands, including the widely used ephrinA1-Fc ligand, the soluble monomeric m-ephrinA1, and novel engineered peptide ligands. We used fluorescence intensity fluctuation (FIF) spectrometry to characterize the EphA2 oligomer populations induced by the different ligands. Interestingly, we found that different monomeric and dimeric ligands induce EphA2 oligomers with widely different size distributions. Our comparison of FIF brightness distribution parameters and EphA2 signaling parameters reveals that the efficacy of EphA2 phosphorylation on tyrosine 588, an autophosphorylation response contributing to EphA2 activation, correlates with EphA2 mean oligomer size. However, we found that other characteristics, such as the efficacy of AKT inhibition and ligand bias coefficients, appear to be independent of EphA2 oligomer size. Taken together, this work highlights the utility of FIF in RTK signaling research and demonstrates a quantitative correlation between the architecture of EphA2 signaling complexes and signaling features.
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Affiliation(s)
- Elmer Zapata-Mercado
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Gabriel Biener
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin, USA
| | - Daniel M McKenzie
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - William C Wimley
- Tulane University School of Medicine, Department of Biochemistry and Molecular Biology, New Orleans, Louisiana, USA
| | - Elena B Pasquale
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA.
| | - Valerica Raicu
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin, USA; Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin, USA.
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, USA.
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Wirth D, Paul MD, Pasquale EB, Hristova K. Direct quantification of ligand-induced lipid and protein microdomains with distinctive signaling properties. CHEMSYSTEMSCHEM 2022; 4:e202200011. [PMID: 36337751 PMCID: PMC9634703 DOI: 10.1002/syst.202200011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Indexed: 11/08/2022]
Abstract
Lipid rafts are ordered lipid domains that are enriched in saturated lipids, such as the ganglioside GM1. While lipid rafts are believed to exist in cells and to serve as signaling platforms through their enrichment in signaling components, they have not been directly observed in the plasma membrane without treatments that artificially cluster GM1 into large lattices. Here, we report that microscopic GM1-enriched domains can form, in the plasma membrane of live mammalian cells expressing the EphA2 receptor tyrosine kinase in response to its ligand ephrinA1-Fc. The GM1-enriched microdomains form concomitantly with EphA2-enriched microdomains. To gain insight into how plasma membrane heterogeneity controls signaling, we quantify the degree of EphA2 segregation and study initial EphA2 signaling steps in both EphA2-enriched and EphA2-depleted domains. By measuring dissociation constants, we demonstrate that the propensity of EphA2 to oligomerize is similar in EphA2-enriched and -depleted domains. However, surprisingly, EphA2 interacts preferentially with its downstream effector SRC in EphA2-depleted domains. The ability to induce microscopic GM1-enriched domains in live cells using a ligand for a transmembrane receptor will give us unprecedented opportunities to study the biophysical chemistry of lipid rafts.
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Affiliation(s)
- Daniel Wirth
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218
| | - Michael D. Paul
- Program in Molecular Biophysics, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218
| | - Elena B. Pasquale
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Road, La Jolla, CA 92037
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218
- Program in Molecular Biophysics, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218
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Regulation of the EphA2 receptor intracellular region by phosphomimetic negative charges in the kinase-SAM linker. Nat Commun 2021; 12:7047. [PMID: 34857764 PMCID: PMC8639986 DOI: 10.1038/s41467-021-27343-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 11/11/2021] [Indexed: 11/22/2022] Open
Abstract
Eph receptor tyrosine kinases play a key role in cell-cell communication. Lack of structural information on the entire multi-domain intracellular region of any Eph receptor has hindered understanding of their signaling mechanisms. Here, we use integrative structural biology to investigate the structure and dynamics of the EphA2 intracellular region. EphA2 promotes cancer malignancy through a poorly understood non-canonical form of signaling involving serine/threonine phosphorylation of the linker connecting its kinase and SAM domains. We show that accumulation of multiple linker negative charges, mimicking phosphorylation, induces cooperative changes in the EphA2 intracellular region from more closed to more extended conformations and perturbs the EphA2 juxtamembrane segment and kinase domain. In cells, linker negative charges promote EphA2 oligomerization. We also identify multiple kinases catalyzing linker phosphorylation. Our findings suggest multiple effects of linker phosphorylation on EphA2 signaling and imply that coordination of different kinases is necessary to promote EphA2 non-canonical signaling. Eph receptor tyrosine kinases and their ephrin ligands mediate cell-cell communication. Here, the authors assess the structure and dynamics of the EphA2 intracellular region and uncover complex effects of phosphorylation within the linker region between EphA2 kinase and SAM domains.
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Biener G, Stoneman MR, Raicu V. Fluorescence intensity fluctuation analysis of receptor oligomerization in membrane domains. Biophys J 2021; 120:3028-3039. [PMID: 34214533 DOI: 10.1016/j.bpj.2021.06.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 06/02/2021] [Accepted: 06/11/2021] [Indexed: 11/26/2022] Open
Abstract
Fluorescence micrographs of the plasma membrane of cells expressing fluorescently labeled G protein-coupled receptors (GPCRs) often exhibit small clusters of pixels (or puncta) with intensities that are higher than those of the surrounding pixels. Although studies of GPCR interactions in uniform membrane areas abound, understanding the details of the GPCR interactions within such puncta as well as the nature of the membrane formations underlying the puncta is hampered by the lack of adequate experimental techniques. Here, we introduce an enhancement of a recently developed method termed fluorescence intensity fluctuation spectrometry, which permits analysis of protein-protein interactions within the puncta in live cell membranes. We applied the novel fluorescence intensity fluctuation data analysis protocol to previously published data from cells expressing human secretin receptors and determined that the oligomer size increases with receptor concentration and duration of treatment with cognate ligand, not only within uniform regions of the membrane (in agreement with previous publications) but also within the puncta. In addition, we found that the number density and fractional area of the puncta increased after treatment with ligand. This method could be applied for probing the evolution in the time of the chain of events that begins with ligand binding and continues with coated pits formation and receptor internalization for other GPCRs and, indeed, other membrane receptors in living cells.
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Affiliation(s)
- Gabriel Biener
- Physics Department, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Michael R Stoneman
- Physics Department, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Valerică Raicu
- Physics Department, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin; Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin.
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P120 catenin potentiates constitutive E-cadherin dimerization at the plasma membrane and regulates trans binding. Curr Biol 2021; 31:3017-3027.e7. [PMID: 34019823 DOI: 10.1016/j.cub.2021.04.061] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 11/09/2020] [Accepted: 04/26/2021] [Indexed: 11/23/2022]
Abstract
Cadherins are essential adhesion proteins that regulate tissue cohesion and paracellular permeability by assembling dense adhesion plaques at cell-to-cell contacts. Adherens junctions are central to a wide range of tissue functions; identifying protein interactions that potentiate their assembly and regulation has been the focus of research for over 2 decades. Here, we present evidence for a new, unexpected mechanism of cadherin oligomerization on cells. Fully quantified spectral imaging fluorescence resonance energy transfer (FSI-FRET) and fluorescence intensity fluctuation (FIF) measurements directly demonstrate that E-cadherin forms constitutive lateral (cis) dimers at the plasma membrane. Results further show that binding of the cytosolic protein p120ctn binding to the intracellular region is required for constitutive E-cadherin dimerization. This finding differs from a model that attributes lateral (cis) cadherin oligomerization solely to extracellular domain interactions. The present, novel findings are further supported by studies of E-cadherin mutants that uncouple p120ctn binding or with cells in which p120ctn was knocked out using CRISPR-Cas9. Quantitative affinity measurements further demonstrate that uncoupling p120ctn binding reduces the cadherin trans binding affinity and cell adhesion. These findings transform the current model of cadherin assembly at cell surfaces and identify the core building blocks of cadherin-mediated intercellular adhesions. They also identify a new role for p120ctn and reconcile findings that implicate both the extracellular and intracellular cadherin domains in cadherin clustering and intercellular cohesion.
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