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Windham IA, Powers AE, Ragusa JV, Wallace ED, Zanellati MC, Williams VH, Wagner CH, White KK, Cohen S. APOE traffics to astrocyte lipid droplets and modulates triglyceride saturation and droplet size. J Cell Biol 2024; 223:e202305003. [PMID: 38334983 PMCID: PMC10857907 DOI: 10.1083/jcb.202305003] [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: 05/02/2023] [Revised: 12/01/2023] [Accepted: 01/08/2024] [Indexed: 02/10/2024] Open
Abstract
The E4 variant of APOE strongly predisposes individuals to late-onset Alzheimer's disease. We demonstrate that in response to lipogenesis, apolipoprotein E (APOE) in astrocytes can avoid translocation into the endoplasmic reticulum (ER) lumen and traffic to lipid droplets (LDs) via membrane bridges at ER-LD contacts. APOE knockdown promotes fewer, larger LDs after a fatty acid pulse, which contain more unsaturated triglyceride after fatty acid pulse-chase. This LD size phenotype was rescued by chimeric APOE that targets only LDs. Like APOE depletion, APOE4-expressing astrocytes form a small number of large LDs enriched in unsaturated triglyceride. Additionally, the LDs in APOE4 cells exhibit impaired turnover and increased sensitivity to lipid peroxidation. Our data indicate that APOE plays a previously unrecognized role as an LD surface protein that regulates LD size and composition. APOE4 causes aberrant LD composition and morphology. Our study contributes to accumulating evidence that APOE4 astrocytes with large, unsaturated LDs are sensitized to lipid peroxidation, which could contribute to Alzheimer's disease risk.
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Affiliation(s)
- Ian A. Windham
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Alex E. Powers
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Joey V. Ragusa
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - E. Diane Wallace
- Mass Spectrometry Core Laboratory, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Maria Clara Zanellati
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Victoria H. Williams
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Colby H. Wagner
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kristen K. White
- Microscopy Services Laboratory, Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah Cohen
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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2
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Walia K, Sharma A, Paul S, Chouhan P, Kumar G, Ringe R, Sharma M, Tuli A. SARS-CoV-2 virulence factor ORF3a blocks lysosome function by modulating TBC1D5-dependent Rab7 GTPase cycle. Nat Commun 2024; 15:2053. [PMID: 38448435 PMCID: PMC10918171 DOI: 10.1038/s41467-024-46417-2] [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: 06/12/2023] [Accepted: 02/26/2024] [Indexed: 03/08/2024] Open
Abstract
SARS-CoV-2, the causative agent of COVID-19, uses the host endolysosomal system for entry, replication, and egress. Previous studies have shown that the SARS-CoV-2 virulence factor ORF3a interacts with the lysosomal tethering factor HOPS complex and blocks HOPS-mediated late endosome and autophagosome fusion with lysosomes. Here, we report that SARS-CoV-2 infection leads to hyperactivation of the late endosomal and lysosomal small GTP-binding protein Rab7, which is dependent on ORF3a expression. We also observed Rab7 hyperactivation in naturally occurring ORF3a variants encoded by distinct SARS-CoV-2 variants. We found that ORF3a, in complex with Vps39, sequesters the Rab7 GAP TBC1D5 and displaces Rab7 from this complex. Thus, ORF3a disrupts the GTP hydrolysis cycle of Rab7, which is beneficial for viral production, whereas the Rab7 GDP-locked mutant strongly reduces viral replication. Hyperactivation of Rab7 in ORF3a-expressing cells impaired CI-M6PR retrieval from late endosomes to the trans-Golgi network, disrupting the biosynthetic transport of newly synthesized hydrolases to lysosomes. Furthermore, the tethering of the Rab7- and Arl8b-positive compartments was strikingly reduced upon ORF3a expression. As SARS-CoV-2 egress requires Arl8b, these findings suggest that ORF3a-mediated hyperactivation of Rab7 serves a multitude of functions, including blocking endolysosome formation, interrupting the transport of lysosomal hydrolases, and promoting viral egress.
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Affiliation(s)
- Kshitiz Walia
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
| | - Abhishek Sharma
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Sankalita Paul
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, Punjab, India
| | - Priya Chouhan
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
| | - Gaurav Kumar
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Rajesh Ringe
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Mahak Sharma
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, Punjab, India
| | - Amit Tuli
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India.
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3
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Kovács Z, Bajusz C, Szabó A, Borkúti P, Vedelek B, Benke R, Lipinszki Z, Kristó I, Vilmos P. A bipartite NLS motif mediates the nuclear import of Drosophila moesin. Front Cell Dev Biol 2024; 12:1206067. [PMID: 38450250 PMCID: PMC10915024 DOI: 10.3389/fcell.2024.1206067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 02/08/2024] [Indexed: 03/08/2024] Open
Abstract
The ERM protein family, which consists of three closely related proteins in vertebrates, ezrin, radixin, and moesin (ERM), is an ancient and important group of cytoplasmic actin-binding and organizing proteins. With their FERM domain, ERMs bind various transmembrane proteins and anchor them to the actin cortex through their C-terminal F-actin binding domain, thus they are major regulators of actin dynamics in the cell. ERMs participate in many fundamental cellular processes, such as phagocytosis, microvilli formation, T-cell activation and tumor metastasis. We have previously shown that, besides its cytoplasmic activities, the single ERM protein of Drosophila melanogaster, moesin, is also present in the cell nucleus, where it participates in gene expression and mRNA export. Here we study the mechanism by which moesin enters the nucleus. We show that the nuclear import of moesin is an NLS-mediated, active process. The nuclear localization sequence of the moesin protein is an evolutionarily highly conserved, conventional bipartite motif located on the surface of the FERM domain. Our experiments also reveal that the nuclear import of moesin does not require PIP2 binding or protein activation, and occurs in monomeric form. We propose, that the balance between the phosphorylated and non-phosphorylated protein pools determines the degree of nuclear import of moesin.
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Affiliation(s)
- Zoltán Kovács
- HUN-REN Biological Research Centre, Szeged, Hungary
- Doctoral School of Multidisciplinary Medical Science, University of Szeged, Szeged, Hungary
| | - Csaba Bajusz
- HUN-REN Biological Research Centre, Szeged, Hungary
| | - Anikó Szabó
- HUN-REN Biological Research Centre, Szeged, Hungary
| | | | | | - Réka Benke
- HUN-REN Biological Research Centre, Szeged, Hungary
| | - Zoltán Lipinszki
- HUN-REN Biological Research Centre, Institute of Biochemistry, MTA SZBK Lendület Laboratory of Cell Cycle Regulation, Szeged, Hungary
| | | | - Péter Vilmos
- HUN-REN Biological Research Centre, Szeged, Hungary
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Han J, Bhatta R, Liu Y, Bo Y, Elosegui-Artola A, Wang H. Metabolic glycan labeling immobilizes dendritic cell membrane and enhances antitumor efficacy of dendritic cell vaccine. Nat Commun 2023; 14:5049. [PMID: 37598185 PMCID: PMC10439884 DOI: 10.1038/s41467-023-40886-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 08/14/2023] [Indexed: 08/21/2023] Open
Abstract
Dendritic cell (DC) vaccine was among the first FDA-approved cancer immunotherapies, but has been limited by the modest cytotoxic T lymphocyte (CTL) response and therapeutic efficacy. Here we report a facile metabolic labeling approach that enables targeted modulation of adoptively transferred DCs for developing enhanced DC vaccines. We show that metabolic glycan labeling can reduce the membrane mobility of DCs, which activates DCs and improves the antigen presentation and subsequent T cell priming property of DCs. Metabolic glycan labeling itself can enhance the antitumor efficacy of DC vaccines. In addition, the cell-surface chemical tags (e.g., azido groups) introduced via metabolic glycan labeling also enable in vivo conjugation of cytokines onto adoptively transferred DCs, which further enhances CTL response and antitumor efficacy. Our DC labeling and targeting technology provides a strategy to improve the therapeutic efficacy of DC vaccines, with minimal interference upon the clinical manufacturing process.
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Affiliation(s)
- Joonsu Han
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Rimsha Bhatta
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Yusheng Liu
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Yang Bo
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Alberto Elosegui-Artola
- Cell and Tissue Mechanobiology Laboratory, Francis Crick Institute, London, UK
- Department of Physics, King's College London, London, UK
| | - Hua Wang
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Cancer Center at Illinois (CCIL), Urbana, IL, 61801, USA.
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Carle College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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5
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Windham IA, Ragusa JV, Wallace ED, Wagner CH, White KK, Cohen S. APOE traffics to astrocyte lipid droplets and modulates triglyceride saturation and droplet size. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.28.538740. [PMID: 37162939 PMCID: PMC10168303 DOI: 10.1101/2023.04.28.538740] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The E4 variant of APOE strongly predisposes individuals to late-onset Alzheimer's disease. We demonstrate that in response to neutral lipid synthesis, apolipoprotein E (APOE) in astrocytes can avoid translocation into the ER lumen and traffic to lipid droplets (LDs) via membrane bridges at ER-LD contacts. APOE knockdown promotes fewer, larger LDs containing more unsaturated triglyceride. This LD size distribution phenotype was rescued by chimeric APOE that targets only LDs. APOE4 - expressing astrocytes also form a small number of large LDs enriched in unsaturated triglyceride. Additionally, the larger LDs in APOE4 cells exhibit impaired turnover and increased sensitivity to lipid peroxidation. Our data indicate that APOE plays a previously unrecognized role as an LD surface protein that regulates LD size and composition. APOE4 is a toxic gain of function variant that causes aberrant LD composition and morphology. We propose that APOE4 astrocytes with large, unsaturated LDs are sensitized to lipid peroxidation or lipotoxicity, which could contribute to Alzheimer's disease risk. Summary Windham et al . discover that APOE in astrocytes can traffic to lipid droplets (LDs), where it modulates LD composition and size. Astrocytes expressing the Alzheimer's risk variant APOE4 form large LDs with impaired turnover and increased peroxidation sensitivity.
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Saebi A, Brown JS, Marando VM, Hartrampf N, Chumbler NM, Hanna S, Poskus M, Loas A, Kiessling LL, Hung DT, Pentelute BL. Rapid Single-Shot Synthesis of the 214 Amino Acid-Long N-Terminal Domain of Pyocin S2. ACS Chem Biol 2023; 18:518-527. [PMID: 36821521 PMCID: PMC10460144 DOI: 10.1021/acschembio.2c00862] [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] [Indexed: 02/24/2023]
Abstract
The impermeable outer membrane of Pseudomonas aeruginosa is bypassed by antibacterial proteins known as S-type pyocins. Because of their properties, pyocins are investigated as a potential new class of antimicrobials against Pseudomonas infections. Their production and modification, however, remain challenging. To address this limitation, we employed automated fast-flow peptide synthesis for the rapid production of a pyocin S2 import domain. The N-terminal domain sequence (PyS2NTD) was synthesized in under 10 h and purified to yield milligram quantities of the desired product. To our knowledge, the 214 amino acid sequence of PyS2NTD is among the longest peptides produced from a "single-shot" synthesis, i.e., made in a single stepwise route without the use of ligation techniques. Biophysical characterization of the PyS2NTD with circular dichroism was consistent with the literature reports. Fluorescently labeled PyS2NTD binds to P. aeruginosa expressing the cognate ferripyoverdine receptor and is taken up into the periplasm. This selective uptake was validated with confocal and super resolution microscopy, flow cytometry, and fluorescence recovery after photobleaching. These modified, synthetic S-type pyocin domains can be used to probe import mechanisms of P. aeruginosa and leveraged to develop selective antimicrobial agents that bypass the outer membrane.
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Affiliation(s)
- Azin Saebi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Joseph S Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Victoria M Marando
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Nina Hartrampf
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Nicole M Chumbler
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, United States
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, United States
| | - Stephanie Hanna
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Mackenzie Poskus
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Andrei Loas
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Laura L Kiessling
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Deborah T Hung
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, United States
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, United States
| | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
- The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
- Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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7
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D'Acunto M. Quantum biology. π-π entanglement signatures in Protein-DNA interactions. Phys Biol 2022; 19. [PMID: 35263721 DOI: 10.1088/1478-3975/ac5bda] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 03/09/2022] [Indexed: 11/11/2022]
Abstract
DNA biological functions are carried out by individual proteins that interact with specific sequences along DNA to prime molecular processes required by cellular metabolism. Protein-DNA interactions include DNA replication, gene expression and its regulation, DNA repair, DNA restriction and modification by endonucleases, generally classified as enzymatic functions, or transcription factors functions. To find specific binding target sequences and finalize their activities, proteins must operate in symbiosis with cellular crowded environment identifying extremely small cognate sequences along the DNA chain, ranging from 15-20 bps for repressors to 4-6 bps for restriction enzymes in less than one second.
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Affiliation(s)
- Mario D'Acunto
- Istituto di Biofisica, Via Moruzzi 1, Pisa, 56124, ITALY
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8
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Warrington SJ, Strutt H, Strutt D. Use of Fluorescence Recovery After Photobleaching (FRAP) to Measure In Vivo Dynamics of Cell Junction-Associated Polarity Proteins. Methods Mol Biol 2022; 2438:1-30. [PMID: 35147932 DOI: 10.1007/978-1-0716-2035-9_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Here, we present a detailed protocol for fluorescence recovery after photobleaching (FRAP) to measure the dynamics of junctional populations of proteins in living tissue. Specifically, we describe how to perform FRAP in Drosophila pupal wings on fluorescently tagged core planar polarity proteins, which exhibit relatively slow junctional turnover. We provide a step-by-step practical guide to performing FRAP, and list a series of controls and optimizations to do before conducting a FRAP experiment. Finally, we describe how to present the FRAP data for publication.
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Affiliation(s)
| | - Helen Strutt
- School of Biosciences, University of Sheffield, Sheffield, UK
| | - David Strutt
- School of Biosciences, University of Sheffield, Sheffield, UK.
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9
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Ilangumaran Ponmalar I, Sarangi NK, Basu JK, Ayappa KG. Pore Forming Protein Induced Biomembrane Reorganization and Dynamics: A Focused Review. Front Mol Biosci 2021; 8:737561. [PMID: 34568431 PMCID: PMC8459938 DOI: 10.3389/fmolb.2021.737561] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
Pore forming proteins are a broad class of pathogenic proteins secreted by organisms as virulence factors due to their ability to form pores on the target cell membrane. Bacterial pore forming toxins (PFTs) belong to a subclass of pore forming proteins widely implicated in bacterial infections. Although the action of PFTs on target cells have been widely investigated, the underlying membrane response of lipids during membrane binding and pore formation has received less attention. With the advent of superresolution microscopy as well as the ability to carry out molecular dynamics (MD) simulations of the large protein membrane assemblies, novel microscopic insights on the pore forming mechanism have emerged over the last decade. In this review, we focus primarily on results collated in our laboratory which probe dynamic lipid reorganization induced in the plasma membrane during various stages of pore formation by two archetypal bacterial PFTs, cytolysin A (ClyA), an α-toxin and listeriolysin O (LLO), a β-toxin. The extent of lipid perturbation is dependent on both the secondary structure of the membrane inserted motifs of pore complex as well as the topological variations of the pore complex. Using confocal and superresolution stimulated emission depletion (STED) fluorescence correlation spectroscopy (FCS) and MD simulations, lipid diffusion, cholesterol reorganization and deviations from Brownian diffusion are correlated with the oligomeric state of the membrane bound protein as well as the underlying membrane composition. Deviations from free diffusion are typically observed at length scales below ∼130 nm to reveal the presence of local dynamical heterogeneities that emerge at the nanoscale-driven in part by preferential protein binding to cholesterol and domains present in the lipid membrane. Interrogating the lipid dynamics at the nanoscale allows us further differentiate between binding and pore formation of β- and α-PFTs to specific domains in the membrane. The molecular insights gained from the intricate coupling that occurs between proteins and membrane lipids and receptors during pore formation are expected to improve our understanding of the virulent action of PFTs.
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Affiliation(s)
| | - Nirod K. Sarangi
- School of Chemical Science, Dublin City University, Dublin, Ireland
| | - Jaydeep K. Basu
- Department of Physics, Indian Institute of Science, Bangalore, India
| | - K. Ganapathy Ayappa
- Center for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India
- Department of Chemical Engineering, Indian Institute of Science, Bengaluru, India
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10
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Long L, Pang XX, Zeng FM, Zhan XH, Xie YH, Pan F, Wang W, Liao LD, Xu XE, Li B, Wang LD, Chang ZJ, Li EM, Xu LY. Promotion of rs3746804 (p. L267P) polymorphism to intracellular SLC52A3a trafficking and riboflavin transportation in esophageal cancer cells. Amino Acids 2021; 53:1197-1209. [PMID: 34223992 DOI: 10.1007/s00726-021-03025-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 06/21/2021] [Indexed: 02/05/2023]
Abstract
Riboflavin is an essential micronutrient for normal cellular growth and function. Lack of dietary riboflavin is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). Previous studies have identified that the human riboflavin transporter SLC52A3a isoform (encoded by SLC52A3) plays a prominent role in esophageal cancer cell riboflavin transportation. Furthermore, SLC52A3 gene single nucleotide polymorphisms rs3746804 (T>C, L267P) and rs3746803 (C >T, T278M) are associated with ESCC risk. However, whether SLC52A3a (p.L267P) and (p.T278M) act in riboflavin transportation in esophageal cancer cell remains inconclusive. Here, we constructed the full-length SLC52A3a protein fused to green fluorescent protein (GFP-SLC52A3a-WT and mutants L267P, T278M, and L267P/T278M). It was confirmed by immunofluorescence-based confocal microscopy that SLC52A3a-WT, L267P, T278M, and L267P/T278M expressed in cell membrane, as well as in a variety of intracellular punctate structures. The live cell confocal imaging showed that SLC52A3a-L267P and L267P/T278M increased the intracellular trafficking of SLC52A3a in ESCC cells. Fluorescence recovery after photobleaching of GFP-tagged SLC52A3a meant that intracellular trafficking of SLC52A3a-L267P and L267P/T278M was rapid dynamics process, leading to its stronger ability to transport riboflavin. Taken together, the above results indicated that the rs3746804 (p.L267P) polymorphism promoted intracellular trafficking of SLC52A3a and riboflavin transportation in ESCC cells.
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Affiliation(s)
- Lin Long
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Xiao-Xiao Pang
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
- Department of Pathology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, 510000, Guangdong, China
| | - Fa-Min Zeng
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Xiu-Hui Zhan
- Research Center of Translational Medicine, Department of Spine Surgery, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Ying-Hua Xie
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Feng Pan
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Wei Wang
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Lian-Di Liao
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Xiu-E Xu
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China
| | - Bin Li
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, Changchun, China
| | - Li-Dong Wang
- Henan Key Laboratory for Cancer Research, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhi-Jie Chang
- State Key Laboratory of Membrane Biology, School of Medicine, Tsinghua University, Beijing, China
| | - En-Min Li
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China.
| | - Li-Yan Xu
- Institute of Oncologic Pathology, Department of Biochemistry and Molecular Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China.
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11
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Sanders DW, Jumper CC, Ackerman PJ, Bracha D, Donlic A, Kim H, Kenney D, Castello-Serrano I, Suzuki S, Tamura T, Tavares AH, Saeed M, Holehouse AS, Ploss A, Levental I, Douam F, Padera RF, Levy BD, Brangwynne CP. SARS-CoV-2 requires cholesterol for viral entry and pathological syncytia formation. eLife 2021; 10:e65962. [PMID: 33890572 PMCID: PMC8104966 DOI: 10.7554/elife.65962] [Citation(s) in RCA: 128] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/01/2021] [Indexed: 12/27/2022] Open
Abstract
Many enveloped viruses induce multinucleated cells (syncytia), reflective of membrane fusion events caused by the same machinery that underlies viral entry. These syncytia are thought to facilitate replication and evasion of the host immune response. Here, we report that co-culture of human cells expressing the receptor ACE2 with cells expressing SARS-CoV-2 spike, results in synapse-like intercellular contacts that initiate cell-cell fusion, producing syncytia resembling those we identify in lungs of COVID-19 patients. To assess the mechanism of spike/ACE2-driven membrane fusion, we developed a microscopy-based, cell-cell fusion assay to screen ~6000 drugs and >30 spike variants. Together with quantitative cell biology approaches, the screen reveals an essential role for biophysical aspects of the membrane, particularly cholesterol-rich regions, in spike-mediated fusion, which extends to replication-competent SARS-CoV-2 isolates. Our findings potentially provide a molecular basis for positive outcomes reported in COVID-19 patients taking statins and suggest new strategies for therapeutics targeting the membrane of SARS-CoV-2 and other fusogenic viruses.
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Affiliation(s)
- David W Sanders
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Chanelle C Jumper
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Paul J Ackerman
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Dan Bracha
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Anita Donlic
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Hahn Kim
- Princeton University Small Molecule Screening Center, Princeton UniversityPrincetonUnited States
- Department of Chemistry, Princeton UniversityPrincetonUnited States
| | - Devin Kenney
- Department of Microbiology, Boston University School of MedicineBostonUnited States
- National Emerging Infectious Diseases Laboratories, Boston UniversityBostonUnited States
| | - Ivan Castello-Serrano
- Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesvilleUnited States
| | - Saori Suzuki
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Tomokazu Tamura
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Alexander H Tavares
- National Emerging Infectious Diseases Laboratories, Boston UniversityBostonUnited States
- Department of Biochemistry, Boston University School of MedicineBostonUnited States
| | - Mohsan Saeed
- National Emerging Infectious Diseases Laboratories, Boston UniversityBostonUnited States
- Department of Biochemistry, Boston University School of MedicineBostonUnited States
| | - Alex S Holehouse
- Department of Biochemistry and Molecular Biophysics, Washington University School of MedicineSt. LouisUnited States
| | - Alexander Ploss
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Ilya Levental
- Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesvilleUnited States
| | - Florian Douam
- Department of Microbiology, Boston University School of MedicineBostonUnited States
- National Emerging Infectious Diseases Laboratories, Boston UniversityBostonUnited States
| | - Robert F Padera
- Department of Pathology, Brigham and Women’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Bruce D Levy
- Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
- Howard Hughes Medical InstitutePrincetonUnited States
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12
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Lippert AH, Dimov IB, Winkel AK, Humphrey J, McColl J, Chen KY, Santos AM, Jenkins E, Franze K, Davis SJ, Klenerman D. Soft Polydimethylsiloxane-Supported Lipid Bilayers for Studying T Cell Interactions. Biophys J 2021; 120:35-45. [PMID: 33248128 PMCID: PMC7820804 DOI: 10.1016/j.bpj.2020.11.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/22/2020] [Accepted: 11/17/2020] [Indexed: 12/23/2022] Open
Abstract
Much of what we know about the early stages of T cell activation has been obtained from studies of T cells interacting with glass-supported lipid bilayers that favor imaging but are orders of magnitude stiffer than typical cells. We developed a method for attaching lipid bilayers to polydimethylsiloxane polymer supports, producing "soft bilayers" with physiological levels of mechanical resistance (Young's modulus of 4 kPa). Comparisons of T cell behavior on soft and glass-supported bilayers revealed that whereas late stages of T cell activation are thought to be substrate-stiffness dependent, early calcium signaling was unaffected by substrate rigidity, implying that early steps in T cell receptor triggering are not mechanosensitive. The exclusion of large receptor-type phosphatases was observed on the soft bilayers, however, even though it is yet to be demonstrated at authentic cell-cell contacts. This work sets the stage for an imaging-based exploration of receptor signaling under conditions closely mimicking physiological cell-cell contact.
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Affiliation(s)
- Anna H Lippert
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
| | - Ivan B Dimov
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Alexander K Winkel
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Jane Humphrey
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - James McColl
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kevin Y Chen
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ana M Santos
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Edward Jenkins
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Simon J Davis
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
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13
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Greig J, Bulgakova NA. Fluorescence Recovery After Photobleaching to Study the Dynamics of Membrane-Bound Proteins In Vivo Using the Drosophila Embryo. Methods Mol Biol 2021; 2179:145-159. [PMID: 32939719 DOI: 10.1007/978-1-0716-0779-4_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The epithelial-to-mesenchymal transition is a highly dynamic cell process and tools such as fluorescence recovery after photobleaching (FRAP), which allow the study of rapid protein dynamics, enable the following of this process in vivo. This technique uses a short intense pulse of photons to disrupt the fluorescence of a tagged protein in a region of a sample. The fluorescent signal intensity after this bleaching is then recorded and the signal recovery used to provide an indicator of the dynamics of the protein of interest. This technique can be applied to any fluorescently tagged protein, but membrane-bound proteins present an interesting challenge as they are spatially confined and subject to specialized cellular trafficking. Several methods of analysis can be applied which can disentangle these various processes and enable the extraction of information from the recovery curves. Here we describe this technique when applied to the quantification of the plasma membrane-bound E-cadherin protein in vivo using the epidermis of the late embryo of Drosophila melanogaster (Drosophila) as an example of this technique.
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Affiliation(s)
- Joshua Greig
- Department of Biomedical Science and Bateson Centre, The University of Sheffield, Sheffield, UK
| | - Natalia A Bulgakova
- Department of Biomedical Science and Bateson Centre, The University of Sheffield, Sheffield, UK.
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14
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Shen Z, Guo Z, Zhou L, Wang Y, Zhang J, Hu J, Zhang Y. Biomembrane induced in situ self-assembly of peptide with enhanced antimicrobial activity. Biomater Sci 2020; 8:2031-2039. [PMID: 32083626 DOI: 10.1039/c9bm01785b] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Antimicrobial peptides (AMPs) as biocides are of great interest because they have the ability to combat antibiotic resistance. Normally, natural AMPs need to be rationally designed or modified for practical use as an antibiotic. Here, a novel AMP, termed FF8, which is a cationic octapeptide composed of arginine, lysine, and phenylalanine, was designed. The FF8 was found to self-assemble into nanofibers when induced by a negatively charged lipid membrane or pH is above 9.4. The fibers on the membrane broke the lipid membrane, forming pores and significantly reducing its fluidity. FF8 also exhibited enhanced antibacterial activity by significantly increasing the permeability of the inner and outer membranes of Escherichia coli (E. coli) and maintaining the pores of the inner membrane of cells, which caused continuous membrane leakage. Because of its high antibacterial activity, cytocompatibility, and cost-effectiveness, FF8 is a promising antibacterial material.
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Affiliation(s)
- Zhiwei Shen
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen Guo
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and University of Chinese Academy of Sciences, Beijing 100049, China
| | - Limin Zhou
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
| | - Yujiao Wang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinjin Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
| | - Jun Hu
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
| | - Yi Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China and Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
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15
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Song D, Jo Y, Choi JM, Jung Y. Client proximity enhancement inside cellular membrane-less compartments governed by client-compartment interactions. Nat Commun 2020; 11:5642. [PMID: 33159068 PMCID: PMC7648067 DOI: 10.1038/s41467-020-19476-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 10/16/2020] [Indexed: 01/17/2023] Open
Abstract
Membrane-less organelles or compartments are considered to be dynamic reaction centers for spatiotemporal control of diverse cellular processes in eukaryotic cells. Although their formation mechanisms have been steadily elucidated via the classical concept of liquid-liquid phase separation, biomolecular behaviors such as protein interactions inside these liquid compartments have been largely unexplored. Here we report quantitative measurements of changes in protein interactions for the proteins recruited into membrane-less compartments (termed client proteins) in living cells. Under a wide range of phase separation conditions, protein interaction signals were vastly increased only inside compartments, indicating greatly enhanced proximity between recruited client proteins. By employing an in vitro phase separation model, we discovered that the operational proximity of clients (measured from client-client interactions) could be over 16 times higher than the expected proximity from actual client concentrations inside compartments. We propose that two aspects should be considered when explaining client proximity enhancement by phase separation compartmentalization: (1) clients are selectively recruited into compartments, leading to concentration enrichment, and more importantly, (2) recruited clients are further localized around compartment-forming scaffold protein networks, which results in even higher client proximity.
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Affiliation(s)
- Daesun Song
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Yongsang Jo
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Jeong-Mo Choi
- Natural Science Research Institute, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
- Department of Chemistry, Pusan National University, Busan, 46241, Republic of Korea
| | - Yongwon Jung
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea.
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16
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Adams RL, Wente SR. Dbp5 associates with RNA-bound Mex67 and Nab2 and its localization at the nuclear pore complex is sufficient for mRNP export and cell viability. PLoS Genet 2020; 16:e1009033. [PMID: 33002012 PMCID: PMC7553267 DOI: 10.1371/journal.pgen.1009033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 10/13/2020] [Accepted: 08/06/2020] [Indexed: 01/04/2023] Open
Abstract
In Saccharomyces cerevisiae, the mRNA export receptor Mex67 is recruited to mature nuclear transcripts to mediate mRNA export through the nuclear pore complex (NPC) to the cytoplasm. Mex67 binds transcripts through adaptor proteins such as the poly(A) binding protein Nab2. When a transcript reaches the cytoplasmic face of the NPC, the DEAD-box protein Dbp5 acts to induce a local structural change to release Nab2 and Mex67 in an essential process termed mRNP remodeling. It is unknown how certain proteins (Nab2, Mex67) are released during Dbp5-mediated mRNP remodeling, whereas others remain associated. Here, we demonstrate that Dbp5 associates in close proximity with Mex67 and Nab2 in a cellular complex. Further, fusion of Dbp5 to Nup159 anchors Dbp5 at the cytoplasmic face of the NPC and is sufficient for cell viability. Thus, we speculate that the essential role of Dbp5 in remodeling exporting mRNPs requires its localization to the NPC and is separable from other subcellular functions of Dbp5. This work supports a model where the diverse nuclear, cytoplasmic and NPC functions of Dbp5 in the mRNA lifecycle are not interdependent and that Dbp5 is locally recruited through complex protein-protein interactions to select regions of transcripts for specific removal of transport proteins at the NPC.
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Affiliation(s)
- Rebecca L. Adams
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Susan R. Wente
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
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17
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Using FRAP to Quantify Changes in Transcription Factor Dynamics After Cell Stimulation: Cell Culture, FRAP, Data Analysis, and Visualization. Methods Mol Biol 2020. [PMID: 32979202 DOI: 10.1007/978-1-0716-0989-7_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Here we show how to measure the mobility of transcription factors using fluorescence recovery after photobleaching (FRAP). Transcription factors are DNA-binding proteins that, upon binding to specific DNA motifs, regulate transcription of their target genes. FRAP is a simple, fast, and cost-effective method, and is a widely used quantitative method to measure the dynamics of fluorescently labeled molecules in solution, membranes, and inside living cells. Dynamics, specified by the immobile fraction, recovery half-time, diffusion constant, and ratio of molecules contributing to different phases of FRAP recovery, can be quantified by FRAP. This can be useful to understand their function in gene regulation. This tutorial is intended to familiarize the reader with the FRAP procedure to quantify transcription factor dynamics using a standard confocal microscope and analysis using MATLAB (MathWorks®). This article will guide the reader through the preconditions of FRAP, and a detailed and step-by-step procedure of preparing cells, bleaching protocol, data analysis in MATLAB, and visualization of the FRAP data.
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18
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Alshareedah I, Kaur T, Banerjee PR. Methods for characterizing the material properties of biomolecular condensates. Methods Enzymol 2020; 646:143-183. [PMID: 33453924 PMCID: PMC7849318 DOI: 10.1016/bs.mie.2020.06.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biomolecular condensates are membrane-less sub-cellular compartments that perform a plethora of important functions in signaling and storage. The material properties of biomolecular condensates such as viscosity, surface tension, viscoelasticity, and macromolecular diffusion play important roles in regulating their biological functions. Aberrations in these properties have been implicated in various neurodegenerative disorders and certain types of cancer. Unraveling the molecular driving forces that control the fluid structure and dynamics of biomolecular condensates across different length- and time-scales necessitates the application of innovative biophysical methodologies. In this chapter, we discuss major experimental techniques that are widely used to study the material states and dynamics of biomolecular condensates as well as their practical and conceptual limitations. We end this chapter with a discussion on more advanced tools that are currently emerging to address the complex fluid dynamics of these condensates.
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Affiliation(s)
| | - Taranpreet Kaur
- Department of Physics, University at Buffalo, Buffalo, NY, United States
| | - Priya R Banerjee
- Department of Physics, University at Buffalo, Buffalo, NY, United States.
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19
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Hatori Y, Kubo T, Sato Y, Inouye S, Akagi R, Seyama T. Visualization of the Redox Status of Cytosolic Glutathione Using the Organelle- and Cytoskeleton-Targeted Redox Sensors. Antioxidants (Basel) 2020; 9:antiox9020129. [PMID: 32028573 PMCID: PMC7070464 DOI: 10.3390/antiox9020129] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 01/22/2020] [Accepted: 01/31/2020] [Indexed: 01/10/2023] Open
Abstract
Glutathione is a small thiol-containing peptide that plays a central role in maintaining cellular redox homeostasis. Glutathione serves as a physiologic redox buffer by providing thiol electrons for catabolizing harmful oxidants and reversing oxidative effects on biomolecules. Recent evidence suggests that the balance of reduced and oxidized glutathione (GSH/GSSG) defines the redox states of Cys residues in proteins and fine-tunes their stabilities and functions. To elucidate the redox balance of cellular glutathione at subcellular resolution, a number of redox-sensitive green fluorescent protein (roGFP) variants have been developed. In this study, we constructed and functionally validated organelle- and cytoskeleton-targeted roGFP and elucidated the redox status of the cytosolic glutathione at a subcellular resolution. These new redox sensors firmly established a highly reduced redox equilibrium of cytosolic glutathione, wherein significant deviation was observed among cells. By targeting the sensor to the cytosolic and lumen sides of the Golgi membrane, we identified a prominent redox gradient across the biological membrane at the Golgi body. The results demonstrated that organelle- and cytoskeleton-targeted sensors enable the assessment of glutathione oxidation near the cytosolic surfaces of different organelle membranes.
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Affiliation(s)
- Yuta Hatori
- Faculty of Pharmacy, Yasuda Women’s University, Hiroshima 731-0153, Japan; (T.K.); (Y.S.); (R.A.); (T.S.)
- Correspondence:
| | - Takanori Kubo
- Faculty of Pharmacy, Yasuda Women’s University, Hiroshima 731-0153, Japan; (T.K.); (Y.S.); (R.A.); (T.S.)
| | - Yuichiro Sato
- Faculty of Pharmacy, Yasuda Women’s University, Hiroshima 731-0153, Japan; (T.K.); (Y.S.); (R.A.); (T.S.)
| | - Sachiye Inouye
- Department of Pharmacy, Faculty of Pharmaceutical Sciences, Sanyo-Onoda City University, Yamaguchi 756-0884, Japan;
| | - Reiko Akagi
- Faculty of Pharmacy, Yasuda Women’s University, Hiroshima 731-0153, Japan; (T.K.); (Y.S.); (R.A.); (T.S.)
| | - Toshio Seyama
- Faculty of Pharmacy, Yasuda Women’s University, Hiroshima 731-0153, Japan; (T.K.); (Y.S.); (R.A.); (T.S.)
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20
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Gibbs E, Perrone B, Hassan A, Kümmerle R, Kriwacki R. NPM1 exhibits structural and dynamic heterogeneity upon phase separation with the p14ARF tumor suppressor. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 310:106646. [PMID: 31751897 PMCID: PMC6934896 DOI: 10.1016/j.jmr.2019.106646] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 11/04/2019] [Accepted: 11/08/2019] [Indexed: 06/10/2023]
Abstract
Nucleophosmin (NPM1) is an abundant nucleolar protein that aids in the maturation of pre-ribosomal particles and participates in oncogenic stress responses through its interaction with the Alternative Reading Frame tumor suppressor (p14ARF). NPM1 mediates multiple mechanisms of phase separation which contribute to the liquid-like properties of nucleoli. However, the effects of phase separation on the structure and dynamics of NPM1 are poorly understood. Here we show that NPM1 undergoes phase separation with p14ARF in vitro, forming condensates that immobilize both proteins. We probed the structure and dynamics of NPM1 within the condensed phase using solid-state NMR spectroscopy. Our results demonstrate that within the condensed phase, the NPM1 oligomerization domain forms an immobile scaffold, while the central intrinsically disordered region and the C-terminal nucleic acid binding domain exhibit relative mobility.
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Affiliation(s)
- Eric Gibbs
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States
| | - Barbara Perrone
- Bruker Switzerland AG, Industriestrasse 26, CH-8117 Fällanden, Switzerland
| | - Alia Hassan
- Bruker Switzerland AG, Industriestrasse 26, CH-8117 Fällanden, Switzerland
| | - Rainer Kümmerle
- Bruker Switzerland AG, Industriestrasse 26, CH-8117 Fällanden, Switzerland
| | - Richard Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, United States.
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21
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Kang M, Day CA, Kenworthy AK. A novel computational framework for D(t) from Fluorescence Recovery after Photobleaching data reveals various anomalous diffusion types in live cell membranes. Traffic 2019; 20:867-880. [PMID: 31452286 DOI: 10.1111/tra.12690] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 08/23/2019] [Accepted: 08/23/2019] [Indexed: 01/20/2023]
Abstract
Diffusion of proteins and lipids in lipid membranes plays a pivotal role in almost all aspects of cellular biology, including motility, exo-/endocytosis and signal transduction. For this reason, gaining a detailed understanding of membrane structure and function has long been a major area of cell biology research. To better elucidate this structure-function relationship, various tools have been developed for diffusion measurements, including Fluorescence Recovery After Photobleaching (FRAP). Because of the complexity of cellular microenvironments, biological diffusion is often correlated over time and described by a time-dependent diffusion coefficient, D(t), although the underlying mechanisms are not fully understood. Since D(t) provides important information regarding cellular structures, such as the existence of subresolution barriers to diffusion, many efforts have been made to quantify D(t) by FRAP assuming a single power law, D(t) = Γt α - 1 where Γ and α are transport coefficient and anomalous exponent. However, straightforward approaches to quantify a general form of D(t) are lacking. In this study, we develop a novel mathematical and computational framework to compute the mean square displacement of diffusing molecules and diffusion coefficient D(t) from each individual time point of confocal FRAP data without the single power law assumption. Additionally, we developed an auxiliary equation for D(t) which can readily distinguish normal diffusion or single power law anomalous diffusion from other types of anomalous diffusion directly from FRAP data. Importantly, by applying this approach to FRAP data from a variety of membrane markers, we demonstrate the single power law anomalous diffusion assumption is not sufficient to describe various types of D(t) of membrane proteins. Lastly, we discuss how our new approaches can be applied to other fluorescence microscopy tools such as Fluorescence Correlation Spectroscopy (FCS) and Single Particle Tracking (SPT).
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Affiliation(s)
- Minchul Kang
- Department of Mathematics, Texas A&M University-Commerce, Commerce, Texas
| | - Charles A Day
- The Hormel Institute, University of Minnesota, Austin, Minnesota
| | - Anne K Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.,Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee.,Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee
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22
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The ERC1 scaffold protein implicated in cell motility drives the assembly of a liquid phase. Sci Rep 2019; 9:13530. [PMID: 31537859 PMCID: PMC6753080 DOI: 10.1038/s41598-019-49630-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 08/07/2019] [Indexed: 12/18/2022] Open
Abstract
Several cellular processes depend on networks of proteins assembled at specific sites near the plasma membrane. Scaffold proteins assemble these networks by recruiting relevant molecules. The scaffold protein ERC1/ELKS and its partners promote cell migration and invasion, and assemble into dynamic networks at the protruding edge of cells. Here by electron microscopy and single molecule analysis we identify ERC1 as an extended flexible dimer. We found that ERC1 scaffolds form cytoplasmic condensates with a behavior that is consistent with liquid phases that are modulated by a predicted disordered region of ERC1. These condensates specifically host partners of a network relevant to cell motility, including liprin-α1, which was unnecessary for the formation of condensates, but influenced their dynamic behavior. Phase separation at specific sites of the cell periphery may represent an elegant mechanism to control the assembly and turnover of dynamic scaffolds needed for the spatial localization and processing of molecules.
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23
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EGF Receptor Stalls upon Activation as Evidenced by Complementary Fluorescence Correlation Spectroscopy and Fluorescence Recovery after Photobleaching Measurements. Int J Mol Sci 2019; 20:ijms20133370. [PMID: 31323980 PMCID: PMC6650801 DOI: 10.3390/ijms20133370] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 07/04/2019] [Accepted: 07/05/2019] [Indexed: 12/28/2022] Open
Abstract
To elucidate the molecular details of the activation-associated clustering of epidermal growth factor receptors (EGFRs), the time course of the mobility and aggregation states of eGFP tagged EGFR in the membranes of Chinese hamster ovary (CHO) cells was assessed by in situ mobility assays. Fluorescence correlation spectroscopy (FCS) was used to probe molecular movements of small ensembles of molecules over short distances and time scales, and to report on the state of aggregation. The diffusion of larger ensembles of molecules over longer distances (and time scales) was investigated by fluorescence recovery after photobleaching (FRAP). Autocorrelation functions could be best fitted by a two-component diffusion model corrected for triplet formation and blinking. The slow, 100–1000 ms component was attributed to membrane localized receptors moving with free Brownian diffusion, whereas the fast, ms component was assigned to cytosolic receptors or their fragments. Upon stimulation with 50 nM EGF, a significant decrease from 0.11 to 0.07 μm2/s in the diffusion coefficient of membrane-localized receptors was observed, followed by recovery to the original value in ~20 min. In contrast, the apparent brightness of diffusing species remained the same. Stripe FRAP experiments yielded a decrease in long-range molecular mobility directly after stimulation, evidenced by an increase in the recovery time of the slow component from 13 to 21.9 s. Our observations are best explained by the transient attachment of ligand-bound EGFRs to immobile or slowly moving structures such as the cytoskeleton or large, previously photobleached receptor aggregates.
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24
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Janáček J, Brejchová J, Svoboda P. Determination of δ-opioid receptor molecules mobility in living cells plasma membrane by novel method of FRAP analysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1346-1354. [PMID: 31071299 DOI: 10.1016/j.bbamem.2019.04.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 04/09/2019] [Accepted: 04/29/2019] [Indexed: 11/18/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) is the preferred method for analyzing the lateral mobility of fluorescently-tagged proteins in the plasma membranes (PMs) of live cells. FRAP experiments are described as being easy to perform; however, the analysis of the acquired data can be difficult. The evaluation procedure must be properly combined with the imaging setup of the confocal microscope to provide unbiased results. With the aim of increasing the accuracy of determining the diffusion coefficient (D) and mobile fraction (Mf) of PM proteins, we developed a novel method for FRAP analysis in the equatorial plane of the cell. This method is based on the calculation of photobleaching characteristics, derived from the light intensity profile and optical parameters of the confocal microscope, and on the model of fluorescent molecule diffusion in PM regions outside of the focal plane. Furthermore, cell movement artifacts in the FRAP data are ameliorated by using a region of interest, which is not fixed but instead moves adaptively in coordination with the movement of cells. When this method was used to determine the mobility of the δ-opioid receptor-eYFP in HEK293 cells, a highly significant decrease in receptor mobility was detected in cholesterol-depleted cells. This decrease was fully reversible by the replenishment of cholesterol levels. Our results demonstrate the crucial role played by cholesterol in the dynamic organization of δ-opioid receptors in the PM under in vivo conditions. Our method may be applied for the determination of the D and Mf values of other PM proteins.
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Affiliation(s)
- Jiří Janáček
- Department of Biomathematics, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 14220 Prague 4, Czech Republic.
| | - Jana Brejchová
- Department of Biomathematics, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Petr Svoboda
- Department of Biomathematics, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 14220 Prague 4, Czech Republic
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25
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Membrane phospholipid alteration causes chronic ER stress through early degradation of homeostatic ER-resident proteins. Sci Rep 2019; 9:8637. [PMID: 31201345 PMCID: PMC6572771 DOI: 10.1038/s41598-019-45020-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/29/2019] [Indexed: 12/31/2022] Open
Abstract
Phospholipid homeostasis in biological membranes is essential to maintain functions of organelles such as the endoplasmic reticulum. Phospholipid perturbation has been associated to cellular stress responses. However, in most cases, the implication of membrane lipid changes to homeostatic cellular response has not been clearly defined. Previously, we reported that Saccharomyces cerevisiae adapts to lipid bilayer stress by upregulating several protein quality control pathways such as the endoplasmic reticulum-associated degradation (ERAD) pathway and the unfolded protein response (UPR). Surprisingly, we observed certain ER-resident transmembrane proteins, which form part of the UPR programme, to be destabilised under lipid bilayer stress. Among these, the protein translocon subunit Sbh1 was prematurely degraded by membrane stiffening at the ER. Moreover, our findings suggest that the Doa10 complex recognises free Sbh1 that becomes increasingly accessible during lipid bilayer stress, perhaps due to the change in ER membrane properties. Premature removal of key ER-resident transmembrane proteins might be an underlying cause of chronic ER stress as a result of lipid bilayer stress.
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White MR, Mitrea DM, Zhang P, Stanley CB, Cassidy DE, Nourse A, Phillips AH, Tolbert M, Taylor JP, Kriwacki RW. C9orf72 Poly(PR) Dipeptide Repeats Disturb Biomolecular Phase Separation and Disrupt Nucleolar Function. Mol Cell 2019; 74:713-728.e6. [PMID: 30981631 DOI: 10.1016/j.molcel.2019.03.019] [Citation(s) in RCA: 109] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 02/12/2019] [Accepted: 03/18/2019] [Indexed: 12/11/2022]
Abstract
Repeat expansion in the C9orf72 gene is the most common cause of the neurodegenerative disorder amyotrophic lateral sclerosis (C9-ALS) and is linked to the unconventional translation of five dipeptide-repeat polypeptides (DPRs). The two enriched in arginine, poly(GR) and poly(PR), infiltrate liquid-like nucleoli, co-localize with the nucleolar protein nucleophosmin (NPM1), and alter the phase separation behavior of NPM1 in vitro. Here, we show that poly(PR) DPRs bind tightly to a long acidic tract within the intrinsically disordered region of NPM1, altering its phase separation with nucleolar partners to the extreme of forming large, soluble complexes that cause droplet dissolution in vitro. In cells, poly(PR) DPRs disperse NPM1 from nucleoli and entrap rRNA in static condensates in a DPR-length-dependent manner. We propose that R-rich DPR toxicity involves disrupting the role of phase separation by NPM1 in organizing ribosomal proteins and RNAs within the nucleolus.
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Affiliation(s)
- Michael R White
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Peipei Zhang
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Christopher B Stanley
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Devon E Cassidy
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Amanda Nourse
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Molecular Interaction Analysis Shared Resource, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Aaron H Phillips
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michele Tolbert
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - J Paul Taylor
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN 38105, USA.
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27
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Kaur T, Alshareedah I, Wang W, Ngo J, Moosa MM, Banerjee PR. Molecular Crowding Tunes Material States of Ribonucleoprotein Condensates. Biomolecules 2019; 9:biom9020071. [PMID: 30791483 PMCID: PMC6406554 DOI: 10.3390/biom9020071] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 02/05/2019] [Accepted: 02/05/2019] [Indexed: 12/19/2022] Open
Abstract
Ribonucleoprotein (RNP) granules are membraneless liquid condensates that dynamically form, dissolve, and mature into a gel-like state in response to a changing cellular environment. RNP condensation is largely governed by promiscuous attractive inter-chain interactions mediated by low-complexity domains (LCDs). Using an archetypal disordered RNP, fused in sarcoma (FUS), here we study how molecular crowding impacts the RNP liquid condensation. We observe that the liquid–liquid coexistence boundary of FUS is lowered by polymer crowders, consistent with an excluded volume model. With increasing bulk crowder concentration, the RNP partition increases and the diffusion rate decreases in the condensed phase. Furthermore, we show that RNP condensates undergo substantial hardening wherein protein-dense droplets transition from viscous fluid to viscoelastic gel-like states in a crowder concentration-dependent manner. Utilizing two distinct LCDs that broadly represent commonly occurring sequence motifs driving RNP phase transitions, we reveal that the impact of crowding is largely independent of LCD charge and sequence patterns. These results are consistent with a thermodynamic model of crowder-mediated depletion interaction, which suggests that inter-RNP attraction is enhanced by molecular crowding. The depletion force is likely to play a key role in tuning the physical properties of RNP condensates within the crowded cellular space.
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Affiliation(s)
- Taranpreet Kaur
- Department of Physics, University at Buffalo, SUNY, NY 14260, USA.
| | | | - Wei Wang
- Department of Physics, University at Buffalo, SUNY, NY 14260, USA.
| | - Jason Ngo
- Department of Physics, University at Buffalo, SUNY, NY 14260, USA.
| | - Mahdi Muhammad Moosa
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Priya R Banerjee
- Department of Physics, University at Buffalo, SUNY, NY 14260, USA.
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Ferrolino MC, Mitrea DM, Michael JR, Kriwacki RW. Compositional adaptability in NPM1-SURF6 scaffolding networks enabled by dynamic switching of phase separation mechanisms. Nat Commun 2018; 9:5064. [PMID: 30498217 PMCID: PMC6265330 DOI: 10.1038/s41467-018-07530-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/08/2018] [Indexed: 12/18/2022] Open
Abstract
The nucleolus, the site for ribosome biogenesis contains hundreds of proteins and several types of RNA. The functions of many non-ribosomal nucleolar proteins are poorly understood, including Surfeit locus protein 6 (SURF6), an essential disordered protein with roles in ribosome biogenesis and cell proliferation. SURF6 co-localizes with Nucleophosmin (NPM1), a highly abundant protein that mediates the liquid-like features of the granular component region of the nucleolus through phase separation. Here, we show that electrostatically-driven interactions between disordered regions of NPM1 and SURF6 drive liquid-liquid phase separation. We demonstrate that co-existing heterotypic (NPM1-SURF6) and homotypic (NPM1-NPM1) scaffolding interactions within NPM1-SURF6 liquid-phase droplets dynamically and seamlessly interconvert in response to variations in molecular crowding and protein concentrations. We propose a mechanism wherein NPM1-dependent nucleolar scaffolds are modulated by non-ribosomal proteins through active rearrangements of interaction networks that can possibly contribute to the directionality of ribosomal biogenesis within the liquid-like nucleolus. The nucleolus is a membrane-less organelle and both Nucleophosmin (NPM1) and Surfeit locus protein 6 (SURF6) are abundant proteins within the nucleolus. Here the authors employ biophysical methods to study the properties of NPM1-S6N droplets and provide insights into the role of SURF6 in maintaining and modulating the liquid-like structure of the nucleolus.
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Affiliation(s)
- Mylene C Ferrolino
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - J Robert Michael
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA. .,Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN, USA.
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29
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Piniella D, Martínez-Blanco E, Ibáñez I, Bartolomé-Martín D, Porlan E, Díez-Guerra J, Giménez C, Zafra F. Identification of novel regulatory partners of the glutamate transporter GLT-1. Glia 2018; 66:2737-2755. [PMID: 30394597 DOI: 10.1002/glia.23524] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/27/2018] [Accepted: 07/30/2018] [Indexed: 01/23/2023]
Abstract
We used proximity-dependent biotin identification (BioID) to find proteins that potentially interact with the major glial glutamate transporter, GLT-1, and we studied how these interactions might affect its activity. GTPase Rac1 was one protein identified, and interfering with its GTP/GDP cycle in mixed primary rat brain cultures affected both the clustering of GLT-1 at the astrocytic processes and the transport kinetics, increasing its uptake activity at low micromolar glutamate concentrations in a manner that was dependent on the effector kinase PAK1 and the actin cytoskeleton. Interestingly, the same manipulations had a different effect on another glial glutamate transporter, GLAST, inhibiting its activity. Importantly, glutamate acts through metabotropic receptors to stimulate the activity of Rac1 in astrocytes, supporting the existence of cross-talk between extracellular glutamate and the astrocytic form of the GLT-1 regulated by Rac1. CDC42EP4/BORG4 (a CDC42 effector) was also identified in the BioID screen, and it is a protein that regulates the assembly of septins and actin fibers, influencing the organization of the cytoskeleton. We found that GLT-1 interacts with septins, which reduces its lateral mobility at the cell surface. Finally, the G-protein subunit GNB4 dampens the activity of GLT-1, as revealed by its response to the activator peptide mSIRK, both in heterologous systems and in primary brain cultures. This effect occurs rapidly and thus, it is unlikely to depend on cytoskeletal dynamics. These novel interactions shed new light on the events controlling GLT-1 activity, thereby helping us to better understand how glutamate homeostasis is maintained in the brain.
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Affiliation(s)
- Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Elena Martínez-Blanco
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Eva Porlan
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Javier Díez-Guerra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
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30
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Mitrea DM, Chandra B, Ferrolino MC, Gibbs EB, Tolbert M, White MR, Kriwacki RW. Methods for Physical Characterization of Phase-Separated Bodies and Membrane-less Organelles. J Mol Biol 2018; 430:4773-4805. [PMID: 30017918 PMCID: PMC6503534 DOI: 10.1016/j.jmb.2018.07.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/04/2018] [Accepted: 07/09/2018] [Indexed: 12/17/2022]
Abstract
Membrane-less organelles are cellular structures which arise through the phenomenon of phase separation. This process enables compartmentalization of specific sets of macromolecules (e.g., proteins, nucleic acids), thereby regulating cellular processes by increasing local concentration, and modulating the structure and dynamics of their constituents. Understanding the connection between structure, material properties and function of membrane-less organelles requires inter-disciplinary approaches, which address length and timescales that span several orders of magnitude (e.g., Ångstroms to micrometer, picoseconds to hours). In this review, we discuss the wide variety of methods that have been applied to characterize the morphology, rheology, structure and dynamics of membrane-less organelles and their components, in vitro and in live cells.
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Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| | - Bappaditya Chandra
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mylene C Ferrolino
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Eric B Gibbs
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michele Tolbert
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michael R White
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA.
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31
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Moustakim M, Felce SL, Zaarour N, Farnie G, McCann FE, Brennan PE. Target Identification Using Chemical Probes. Methods Enzymol 2018; 610:27-58. [PMID: 30390803 DOI: 10.1016/bs.mie.2018.09.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Chemical probes are small molecules with potency and selectivity for a single or small number of protein targets. A good chemical probe engages its target intracellularly and is accompanied by a chemically similar, but inactive molecule to be used as a negative control in cellular phenotypic screening. The utility of these chemical probes is ultimately governed by how well they are developed and characterized. Chemical probes either as single entities, or in chemical probes sets are being increasingly used to interrogate the biological relevance of a target in a disease model. This chapter lays out the core properties of chemical probes, summarizes the seminal and emerging techniques used to demonstrate robust intracellular target engagement. Translation of target engagement assays to disease-relevant phenotypic assays using primary patient-derived cells and tissues is also reviewed. Two examples of epigenetic chemical probe discovery and utility are presented whereby target engagement pointed to novel disease associations elucidated from poorly understood protein targets. Finally, a number of examples are discussed whereby chemical probe sets, or "chemogenomic libraries" are used to illuminate new target-disease links which may represent future directions for chemical probe utility.
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Affiliation(s)
- Moses Moustakim
- Nuffield Department of Medicine, Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Suet Ling Felce
- Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, United Kingdom
| | - Nancy Zaarour
- Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, United Kingdom; Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Gillian Farnie
- Nuffield Department of Medicine, Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, United Kingdom.
| | - Fiona E McCann
- Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, United Kingdom; Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom.
| | - Paul E Brennan
- Nuffield Department of Medicine, Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, United Kingdom; Nuffield Department of Medicine, Alzheimer's Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, United Kingdom.
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32
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Agarwal SR, Gratwohl J, Cozad M, Yang PC, Clancy CE, Harvey RD. Compartmentalized cAMP Signaling Associated With Lipid Raft and Non-raft Membrane Domains in Adult Ventricular Myocytes. Front Pharmacol 2018; 9:332. [PMID: 29740315 PMCID: PMC5925456 DOI: 10.3389/fphar.2018.00332] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/21/2018] [Indexed: 11/23/2022] Open
Abstract
Aim: Confining cAMP production to discrete subcellular locations makes it possible for this ubiquitous second messenger to elicit unique functional responses. Yet, factors that determine how and where the production of this diffusible signaling molecule occurs are incompletely understood. The fluid mosaic model originally proposed that signal transduction occurs through random interactions between proteins diffusing freely throughout the plasma membrane. However, it is now known that the movement of membrane proteins is restricted, suggesting that the plasma membrane is segregated into distinct microdomains where different signaling proteins can be concentrated. In this study, we examined what role lipid raft and non-raft membrane domains play in compartmentation of cAMP signaling in adult ventricular myocytes. Methods and Results: The freely diffusible fluorescence resonance energy transfer-based biosensor Epac2-camps was used to measure global cytosolic cAMP responses, while versions of the probe targeted to lipid raft (Epac2-MyrPalm) and non-raft (Epac2-CAAX) domains were used to monitor local cAMP production near the plasma membrane. We found that β-adrenergic receptors, which are expressed in lipid raft and non-raft domains, produce cAMP responses near the plasma membrane that are distinctly different from those produced by E-type prostaglandin receptors, which are expressed exclusively in non-raft domains. We also found that there are differences in basal cAMP levels associated with lipid raft and non-raft domains, and that this can be explained by differences in basal adenylyl cyclase activity associated with each of these membrane environments. In addition, we found evidence that phosphodiesterases 2, 3, and 4 work together in regulating cAMP activity associated with both lipid raft and non-raft domains, while phosphodiesterase 3 plays a more prominent role in the bulk cytoplasmic compartment. Conclusion: These results suggest that different membrane domains contribute to the formation of distinct pools of cAMP under basal conditions as well as following receptor stimulation in adult ventricular myocytes.
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Affiliation(s)
- Shailesh R Agarwal
- Department of Pharmacology, University of Nevada, Reno, Reno, NV, United States
| | - Jackson Gratwohl
- Department of Pharmacology, University of Nevada, Reno, Reno, NV, United States
| | - Mia Cozad
- Department of Pharmacology, University of Nevada, Reno, Reno, NV, United States
| | - Pei-Chi Yang
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
| | - Robert D Harvey
- Department of Pharmacology, University of Nevada, Reno, Reno, NV, United States
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Robinson SW, Bourgognon JM, Spiers JG, Breda C, Campesan S, Butcher A, Mallucci GR, Dinsdale D, Morone N, Mistry R, Smith TM, Guerra-Martin M, Challiss RAJ, Giorgini F, Steinert JR. Nitric oxide-mediated posttranslational modifications control neurotransmitter release by modulating complexin farnesylation and enhancing its clamping ability. PLoS Biol 2018; 16:e2003611. [PMID: 29630591 PMCID: PMC5890968 DOI: 10.1371/journal.pbio.2003611] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 02/20/2018] [Indexed: 11/18/2022] Open
Abstract
Nitric oxide (NO) regulates neuronal function and thus is critical for tuning neuronal communication. Mechanisms by which NO modulates protein function and interaction include posttranslational modifications (PTMs) such as S-nitrosylation. Importantly, cross signaling between S-nitrosylation and prenylation can have major regulatory potential. However, the exact protein targets and resulting changes in function remain elusive. Here, we interrogated the role of NO-dependent PTMs and farnesylation in synaptic transmission. We found that NO compromises synaptic function at the Drosophila neuromuscular junction (NMJ) in a cGMP-independent manner. NO suppressed release and reduced the size of available vesicle pools, which was reversed by glutathione (GSH) and occluded by genetic up-regulation of GSH-generating and de-nitrosylating glutamate-cysteine-ligase and S-nitroso-glutathione reductase activities. Enhanced nitrergic activity led to S-nitrosylation of the fusion-clamp protein complexin (cpx) and altered its membrane association and interactions with active zone (AZ) and soluble N-ethyl-maleimide-sensitive fusion protein Attachment Protein Receptor (SNARE) proteins. Furthermore, genetic and pharmacological suppression of farnesylation and a nitrosylation mimetic mutant of cpx induced identical physiological and localization phenotypes as caused by NO. Together, our data provide evidence for a novel physiological nitrergic molecular switch involving S-nitrosylation, which reversibly suppresses farnesylation and thereby enhances the net-clamping function of cpx. These data illustrate a new mechanistic signaling pathway by which regulation of farnesylation can fine-tune synaptic release.
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Affiliation(s)
- Susan W. Robinson
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | | | - Jereme G. Spiers
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Carlo Breda
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Susanna Campesan
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Adrian Butcher
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Giovanna R. Mallucci
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - David Dinsdale
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Nobuhiro Morone
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Raj Mistry
- Department of Molecular and Cell Biology, University of Leicester, Leicester, United Kingdom
| | - Tim M. Smith
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | | | - R. A. John Challiss
- Department of Molecular and Cell Biology, University of Leicester, Leicester, United Kingdom
| | - Flaviano Giorgini
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Joern R. Steinert
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
- * E-mail:
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Systems for localized release to mimic paracrine cell communication in vitro. J Control Release 2018; 278:24-36. [PMID: 29601931 DOI: 10.1016/j.jconrel.2018.03.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 03/24/2018] [Accepted: 03/26/2018] [Indexed: 12/27/2022]
Abstract
Paracrine cell communication plays a pivotal role for signal exchange between proximal cells in vivo. However, this localized, gradient type release of mediators at very low concentrations (pg/ml), relevant during physiological and pathological processes, is rarely reflected within in vitro approaches. This review gives an overview on state-of-the-art approaches, which transfer the paracrine cell-to-cell communication into in vitro cell culture model setups. The traditional methods like trans-well assays and more advanced microfluidic approaches are included. The review focusses on systems for localized release, mostly based on microparticles, which tightly mimic the paracrine interaction between single cells in 3D microenvironments. Approaches based on single microparticles, with the main focus on affinity-controlled storage and release of cytokines, are reviewed and their importance for understanding paracrine communication is highlighted. Various methods to study the cytokine release and their advantages and disadvantages are discussed. Basic principles of the release characteristics, like diffusion mechanisms, are quantitatively described, including the formation of resulting gradients around the local sources. In vitro cell experiments using such localized microparticle release systems in approaches to increase understanding of stem cell behavior within their niches and regulation of wound healing are highlighted as examples of successful localized release systems for mimicking paracrine cell communication.
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35
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Mathew MP, Donaldson JG. Distinct cargo-specific response landscapes underpin the complex and nuanced role of galectin-glycan interactions in clathrin-independent endocytosis. J Biol Chem 2018; 293:7222-7237. [PMID: 29581232 DOI: 10.1074/jbc.ra118.001802] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/22/2018] [Indexed: 02/01/2023] Open
Abstract
Clathrin-independent endocytosis (CIE) is a form of endocytosis that lacks a defined cytoplasmic machinery. Here, we asked whether glycan interactions, acting from the outside, could be a part of that endocytic machinery. We show that the perturbation of global cellular patterns of protein glycosylation by modulation of metabolic flux affects CIE. Interestingly, these changes in glycosylation had cargo-specific effects. For example, in HeLa cells, GlcNAc treatment, which increases glycan branching, increased major histocompatibility complex class I (MHCI) internalization but inhibited CIE of the glycoprotein CD59 molecule (CD59). The effects of knocking down the expression of galectin 3, a carbohydrate-binding protein and an important player in galectin-glycan interactions, were also cargo-specific and stimulated CD59 uptake. By contrast, inhibition of all galectin-glycan interactions by lactose inhibited CIE of both MHCI and CD59. None of these treatments affected clathrin-mediated endocytosis, implying that glycosylation changes specifically affect CIE. We also found that the galectin lattice tailors membrane fluidity and cell spreading. Furthermore, changes in membrane dynamics mediated by the galectin lattice affected macropinocytosis, an altered form of CIE, in HT1080 cells. Our results suggest that glycans play an important and nuanced role in CIE, with each cargo being affected uniquely by alterations in galectin and glycan profiles and their interactions. We conclude that galectin-driven effects exist on a continuum from stimulatory to inhibitory, with distinct CIE cargo proteins having unique response landscapes and with different cell types starting at different positions on these conceptual landscapes.
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Affiliation(s)
- Mohit P Mathew
- Cell Biology and Physiology Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
| | - Julie G Donaldson
- Cell Biology and Physiology Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
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36
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Overlapping expression patterns and functions of three paralogous P5B ATPases in Caenorhabditis elegans. PLoS One 2018; 13:e0194451. [PMID: 29547664 PMCID: PMC5856429 DOI: 10.1371/journal.pone.0194451] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/02/2018] [Indexed: 11/19/2022] Open
Abstract
P5B ATPases are present in the genomes of diverse unicellular and multicellular eukaryotes, indicating that they have an ancient origin, and that they are important for cellular fitness. Inactivation of ATP13A2, one of the four human P5B ATPases, leads to early-onset Parkinson's disease (Kufor-Rakeb Syndrome). The presence of an invariant PPALP motif within the putative substrate interaction pocket of transmembrane segment M4 suggests that all P5B ATPases might have similar transport specificity; however, the identity of the transport substrate(s) remains unknown. Nematodes of the genus Caenorhabditis possess three paralogous P5B ATPase genes, catp-5, catp-6 and catp-7, which probably originated from a single ancestral gene around the time of origin of the Caenorhabditid clade. By using CRISPR/Cas9, we have systematically investigated the expression patterns, subcellular localization and biological functions of each of the P5B ATPases of C. elegans. We find that each gene has a unique expression pattern, and that some tissues express more than one P5B. In some tissues where their expression patterns overlap, different P5Bs are targeted to different subcellular compartments (e.g., early endosomes vs. plasma membrane), whereas in other tissues they localize to the same compartment (plasma membrane). We observed lysosomal co-localization between CATP-6::GFP and LMP-1::RFP in transgenic animals; however, this was an artifact of the tagged LMP-1 protein, since anti-LMP-1 antibody staining of native protein revealed that LMP-1 and CATP-6::GFP occupy different compartments. The nematode P5Bs are at least partially redundant, since we observed synthetic sterility in catp-5(0); catp-6(0) and catp-6(0) catp-7(0) double mutants. The double mutants exhibit defects in distal tip cell migration that resemble those of ina-1 (alpha integrin ortholog) and vab-3 (Pax6 ortholog) mutants, suggesting that the nematode P5Bs are required for ina-1and/or vab-3 function. This is potentially a conserved regulatory interaction, since mammalian ATP13A2, alpha integrin and Pax6 are all required for proper dopaminergic neuron function.
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Metabolic flux-driven sialylation alters internalization, recycling, and drug sensitivity of the epidermal growth factor receptor (EGFR) in SW1990 pancreatic cancer cells. Oncotarget 2018; 7:66491-66511. [PMID: 27613843 PMCID: PMC5341816 DOI: 10.18632/oncotarget.11582] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 08/01/2016] [Indexed: 12/12/2022] Open
Abstract
In prior work we reported that advanced stage, drug-resistant pancreatic cancer cells (the SW1990 line) can be sensitized to the EGFR-targeting tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib by treatment with 1,3,4-O-Bu3ManNAc (Bioorg. Med. Chem. Lett. (2015) 25(6):1223-7). Here we provide mechanistic insights into how this compound inhibits EGFR activity and provides synergy with TKI drugs. First, we showed that the sialylation of the EGFR receptor was at most only modestly enhanced (by ∼20 to 30%) compared to overall ∼2-fold increase in cell surface levels of this sugar. Second, flux-driven sialylation did not alter EGFR dimerization as has been reported for cancer cell lines that experience increased sialylation due to spontaneous mutations. Instead, we present evidence that 1,3,4-O-Bu3ManNAc treatment weakens the galectin lattice, increases the internalization of EGFR, and shifts endosomal trafficking towards non-clathrin mediated (NCM) endocytosis. Finally, by evaluating downstream targets of EGFR signaling, we linked synergy between 1,3,4-O-Bu3ManNAc and existing TKI drugs to a shift from clathrin-coated endocytosis (which allows EGFR signaling to continue after internalization) towards NCM endocytosis, which targets internalized moieties for degradation and thereby rapidly diminishes signaling.
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Sala K, Raimondi A, Tonoli D, Tacchetti C, de Curtis I. Identification of a membrane-less compartment regulating invadosome function and motility. Sci Rep 2018; 8:1164. [PMID: 29348417 PMCID: PMC5773524 DOI: 10.1038/s41598-018-19447-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 12/27/2017] [Indexed: 02/07/2023] Open
Abstract
Depletion of liprin-α1, ERC1 or LL5 scaffolds inhibits extracellular matrix degradation by invasive cells. These proteins co-accumulate near invadosomes in NIH-Src cells, identifying a novel invadosome–associated compartment distinct from the core and adhesion ring of invadosomes. Depletion of either protein perturbs the organization of invadosomes without influencing the recruitment of MT1-MMP metalloprotease. Liprin-α1 is not required for de novo formation of invadosomes after their disassembly by microtubules and Src inhibitors, while its depletion inhibits invadosome motility, thus affecting matrix degradation. Fluorescence recovery after photobleaching shows that the invadosome–associated compartment is dynamic, while correlative light immunoelectron microscopy identifies bona fide membrane–free invadosome–associated regions enriched in liprin-α1, which is virtually excluded from the invadosome core. The results indicate that liprin-α1, LL5 and ERC1 define a novel dynamic membrane-less compartment that regulates matrix degradation by affecting invadosome motility.
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Affiliation(s)
- Kristyna Sala
- Cell Adhesion Unit - Division of Neuroscience, IRCSS San Raffaele Scientific Institute, 20132, Milano, Italy
| | - Andrea Raimondi
- Experimental Imaging Center, IRCSS San Raffaele Scientific Institute, 20132, Milano, Italy
| | - Diletta Tonoli
- Cell Adhesion Unit - Division of Neuroscience, IRCSS San Raffaele Scientific Institute, 20132, Milano, Italy
| | - Carlo Tacchetti
- Experimental Imaging Center, IRCSS San Raffaele Scientific Institute, 20132, Milano, Italy.,San Raffaele Vita-Salute University, via Olgettina 58, 20132, Milano, Italy
| | - Ivan de Curtis
- Cell Adhesion Unit - Division of Neuroscience, IRCSS San Raffaele Scientific Institute, 20132, Milano, Italy. .,San Raffaele Vita-Salute University, via Olgettina 58, 20132, Milano, Italy.
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Liao D, Mei H, Hu Y, Newman DK, Newman PJ. CRISPR-mediated deletion of the PECAM-1 cytoplasmic domain increases receptor lateral mobility and strengthens endothelial cell junctional integrity. Life Sci 2018; 193:186-193. [PMID: 29122551 DOI: 10.1016/j.lfs.2017.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 10/24/2017] [Accepted: 11/04/2017] [Indexed: 10/18/2022]
Abstract
AIMS PECAM-1 is an abundant endothelial cell surface receptor that becomes highly enriched at endothelial cell-cell junctions, where it functions to mediate leukocyte transendothelial migration, sense changes in shear and flow, and maintain the vascular permeability barrier. Homophilic interactions mediated by the PECAM-1 extracellular domain are known to be required for PECAM-1 to perform these functions; however, much less is understood about the role of its cytoplasmic domain in these processes. MAIN METHODS CRISPR/Cas9 gene editing technology was employed to generate human endothelial cell lines that either lack PECAM-1 entirely, or express mutated PECAM-1 missing the majority of its cytoplasmic domain (∆CD-PECAM-1). The endothelial barrier function was evaluated by Electric Cell-substrate Impedance Sensing, and molecular mobility was assessed by fluorescence recovery after photobleaching. KEY FINDINGS We found that ∆CD-PECAM-1 concentrates normally at endothelial cell junctions, but has the unexpected property of conferring increased baseline barrier resistance, as well as a more rapid rate of recovery of vascular integrity following thrombin-induced disruption of the endothelial barrier. Fluorescence recovery after photobleaching analysis revealed that ∆CD-PECAM-1 exhibits increased mobility within the plane of the plasma membrane, thus allowing it to redistribute more rapidly back to endothelial cell-cell borders to reform the vascular permeability barrier. SIGNIFICANCE The PECAM-1 cytoplasmic domain plays a novel role in regulating the rate and extent of vascular permeability following thrombotic or inflammatory challenge.
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Affiliation(s)
- Danying Liao
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI, United States; Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, China
| | - Heng Mei
- Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, China
| | - Yu Hu
- Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, China
| | - Debra K Newman
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI, United States; Department of Pharmacology, Medical College of Wisconsin, Milwaukee, United States; Department of Microbiology, Medical College of Wisconsin, Milwaukee, United States; The Cardiovascular Center, Medical College of Wisconsin, Milwaukee, United States
| | - Peter J Newman
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI, United States; Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, China; Department of Pharmacology, Medical College of Wisconsin, Milwaukee, United States; Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, United States; The Cardiovascular Center, Medical College of Wisconsin, Milwaukee, United States.
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40
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Hatori Y, Inouye S, Akagi R, Seyama T. Local redox environment beneath biological membranes probed by palmitoylated-roGFP. Redox Biol 2017; 14:679-685. [PMID: 29179107 PMCID: PMC5704182 DOI: 10.1016/j.redox.2017.11.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 12/31/2022] Open
Abstract
Production of reactive oxygen species (ROS) and consequent glutathione oxidation are associated with various physiological processes and diseases, including cell differentiation, senescence, and inflammation. GFP-based redox sensors provide a straight-forward approach to monitor ROS levels and glutathione oxidation within a living cell at the subcellular resolution. We utilized palmitoylated versions of cytosolic glutathione and hydrogen peroxide sensors (Grx1-roGFP2 and roGFP2-Orp1, respectively) and demonstrated a unique redox environment near biological membranes. In HeLa cells, cytosolic glutathione was practically completely reduced (EGSH/GSSG = − 333 mV) and hydrogen peroxide level was under the detectable range. In contrast, the cytoplasmic milieu near membranes of intracellular vesicles exhibited significant glutathione oxidation (EGSH/GSSG > − 256 mV) and relatively high H2O2 production, which was not observed for the plasma membrane. These vesicles colocalized with internalized EGFR, suggesting that H2O2 production and glutathione oxidation are characteristics of cytoplasmic surfaces of the endocytosed vesicles. The results visually illustrate local redox heterogeneity within the cytosol for the first time. Palmitoylated versions of redox sensors were constructed. The sensors successfully visualized local redox environment near membranes. The cytosol is oxidative near endocytosed vesicles containing EGFR.
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Affiliation(s)
- Yuta Hatori
- Department of Pharmacy, Yasuda Women's University, Hiroshima, Japan.
| | - Sachiye Inouye
- Department of Pharmacy, Yasuda Women's University, Hiroshima, Japan
| | - Reiko Akagi
- Department of Pharmacy, Yasuda Women's University, Hiroshima, Japan
| | - Toshio Seyama
- Department of Pharmacy, Yasuda Women's University, Hiroshima, Japan
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Quantitative analysis of molecular partition towards lipid membranes using surface plasmon resonance. Sci Rep 2017; 7:45647. [PMID: 28358389 PMCID: PMC5372468 DOI: 10.1038/srep45647] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 03/01/2017] [Indexed: 12/27/2022] Open
Abstract
Understanding the interplay between molecules and lipid membranes is fundamental when studying cellular and biotechnological phenomena. Partition between aqueous media and lipid membranes is key to the mechanism of action of many biomolecules and drugs. Quantifying membrane partition, through adequate and robust parameters, is thus essential. Surface Plasmon Resonance (SPR) is a powerful technique for studying 1:1 stoichiometric interactions but has limited application to lipid membrane partition data. We have developed and applied a novel mathematical model for SPR data treatment that enables determination of kinetic and equilibrium partition constants. The method uses two complementary fitting models for association and dissociation sensorgram data. The SPR partition data obtained for the antibody fragment F63, the HIV fusion inhibitor enfuvirtide, and the endogenous drug kyotorphin towards POPC membranes were compared against data from independent techniques. The comprehensive kinetic and partition models were applied to the membrane interaction data of HRC4, a measles virus entry inhibitor peptide, revealing its increased affinity for, and retention in, cholesterol-rich membranes. Overall, our work extends the application of SPR beyond the realm of 1:1 stoichiometric ligand-receptor binding into a new and immense field of applications: the interaction of solutes such as biomolecules and drugs with lipids.
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LeftyA decreases Actin Polymerization and Stiffness in Human Endometrial Cancer Cells. Sci Rep 2016; 6:29370. [PMID: 27404958 PMCID: PMC4941646 DOI: 10.1038/srep29370] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 06/16/2016] [Indexed: 12/27/2022] Open
Abstract
LeftyA, a cytokine regulating stemness and embryonic differentiation, down-regulates cell proliferation and migration. Cell proliferation and motility require actin reorganization, which is under control of ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1). The present study explored whether LeftyA modifies actin cytoskeleton, shape and stiffness of Ishikawa cells, a well differentiated endometrial carcinoma cell line. The effect of LeftyA on globular over filamentous actin ratio was determined utilizing Western blotting and flow cytometry. Rac1 and PAK1 transcript levels were measured by qRT-PCR as well as active Rac1 and PAK1 by immunoblotting. Cell stiffness (quantified by the elastic modulus), cell surface area and cell volume were studied by atomic force microscopy (AFM). As a result, 2 hours treatment with LeftyA (25 ng/ml) significantly decreased Rac1 and PAK1 transcript levels and activity, depolymerized actin, and decreased cell stiffness, surface area and volume. The effect of LeftyA on actin polymerization was mimicked by pharmacological inhibition of Rac1 and PAK1. In the presence of the Rac1 or PAK1 inhibitor LeftyA did not lead to significant further actin depolymerization. In conclusion, LeftyA leads to disruption of Rac1 and Pak1 activity with subsequent actin depolymerization, cell softening and cell shrinkage.
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Luo N, Yan A, Yang Z. Measuring Exocytosis Rate Using Corrected Fluorescence Recovery After Photoconversion. Traffic 2016; 17:554-64. [PMID: 26822068 DOI: 10.1111/tra.12380] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/25/2016] [Accepted: 01/25/2016] [Indexed: 12/31/2022]
Abstract
Exocytosis plays crucial roles in regulating the distribution and function of plasma membrane (PM) and extracellular matrix proteins. However, measuring the exocytosis rate of a specific protein by conventional methods is very difficult because of exocytosis-independent trafficking such as endocytosis, which also affects membrane protein distribution. Here, we describe a novel method, corrected fluorescence recovery after photoconversion, in which exocytosis-dependent and -independent trafficking events are measured simultaneously to accurately determine exocytosis rate. In this method, the protein-of-interest is tagged with Dendra2, a green-to-red photoconvertible fluorescent protein. Following the photoconversion of PM-localized Dendra2, both the recovery of the green signal and the changes in the photoconverted red signal are measured, and the rate of exocytosis is calculated from the changing rates of these two signals.
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Affiliation(s)
- Nan Luo
- Center for Plant Cell Biology, Institute of Integrated Genome Biology, University of California, Riverside, CA, USA.,Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - An Yan
- Center for Plant Cell Biology, Institute of Integrated Genome Biology, University of California, Riverside, CA, USA.,Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA.,Current address: Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Zhenbiao Yang
- Center for Plant Cell Biology, Institute of Integrated Genome Biology, University of California, Riverside, CA, USA.,Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
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44
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Fluorescence Recovery After Photobleaching Analysis of the Diffusional Mobility of Plasma Membrane Proteins: HER3 Mobility in Breast Cancer Cell Membranes. Methods Mol Biol 2016; 1376:97-105. [PMID: 26552678 DOI: 10.1007/978-1-4939-3170-5_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The fluorescence recovery after photobleaching (FRAP) method is a straightforward means of assessing the diffusional mobility of membrane-associated proteins that is readily performed with current confocal microscopy instrumentation. We describe here the specific application of the FRAP method in characterizing the lateral diffusion of genetically encoded green fluorescence protein (GFP)-tagged plasma membrane receptor proteins. The method is exemplified in an examination of whether the previously observed segregation of the mammalian HER3 receptor protein in discrete plasma membrane microdomains results from its physical interaction with cellular entities that restrict its mobility. Our FRAP measurements of the diffusional mobility of GFP-tagged HER3 reporters expressed in MCF7 cultured breast cancer cells showed that despite the observed segregation of HER3 receptors within plasma membrane microdomains their diffusion on the macroscopic scale is not spatially restricted. Thus, in FRAP analyses of various HER3 reporters a near-complete recovery of fluorescence after photobleaching was observed, indicating that HER3 receptors are not immobilized by long-lived physical interactions with intracellular species. An examination of HER3 proteins with varying intracellular domain sequence truncations also indicated that a proposed formation of oligomeric HER3 networks, mediated by physical interactions involving specific HER3 intracellular domain sequences, either does not occur or does not significantly reduce HER3 mobility on the macroscopic scale.
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Sánchez MF, Dodes Traian MM, Levi V, Carrer DC. One-Photon Lithography for High-Quality Lipid Bilayer Micropatterns. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:11943-11950. [PMID: 26452154 DOI: 10.1021/acs.langmuir.5b02934] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A relevant question in cell biology with broad implications in biomedicine is how the organization and dynamics of interacting membranes modulate signaling cascades that involve cell-cell contact. The functionalization of surfaces with supported lipid bilayers containing tethered proteins is a particularly useful method to present ligands with membrane-like mobility to cells. Here, we present a method to generate micrometer-sized patches of lipid bilayers decorated with proteins. The method uses an economic microcontact printing technique based on one-photon lithography that can be easily implemented in a commercial laser scanning microscope. We verified that both proteins and lipids freely diffuse within the patterned bilayer, as assessed by z-scan fluorescence correlation spectroscopy and fluorescence recovery after photobleaching. These results suggest that the supported lipid bilayer patterns constitute an optimal system to explore processes involving direct interactions between cells. We also illustrate possible applications of this method by exploring the interaction of cells expressing the Fas receptor and patterns of lipid bilayers containing an agonist antibody against Fas.
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Affiliation(s)
- M Florencia Sánchez
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), CONICET-Universidad Nacional de Córdoba , Friuli 2434, CC389, 5000 Córdoba, Argentina
| | - Martín M Dodes Traian
- Departamento de Química Biológica-IQUIBICEN Facultad de Ciencias Exactas, Universidad de Buenos Aires, Ciudad Universitaria , 1428 Buenos Aires, Argentina
| | - Valeria Levi
- Departamento de Química Biológica-IQUIBICEN Facultad de Ciencias Exactas, Universidad de Buenos Aires, Ciudad Universitaria , 1428 Buenos Aires, Argentina
| | - Dolores C Carrer
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), CONICET-Universidad Nacional de Córdoba , Friuli 2434, CC389, 5000 Córdoba, Argentina
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46
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Kang M, Andreani M, Kenworthy AK. Validation of Normalizations, Scaling, and Photofading Corrections for FRAP Data Analysis. PLoS One 2015; 10:e0127966. [PMID: 26017223 PMCID: PMC4446327 DOI: 10.1371/journal.pone.0127966] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 04/22/2015] [Indexed: 01/14/2023] Open
Abstract
Fluorescence Recovery After Photobleaching (FRAP) has been a versatile tool to study transport and reaction kinetics in live cells. Since the fluorescence data generated by fluorescence microscopy are in a relative scale, a wide variety of scalings and normalizations are used in quantitative FRAP analysis. Scaling and normalization are often required to account for inherent properties of diffusing biomolecules of interest or photochemical properties of the fluorescent tag such as mobile fraction or photofading during image acquisition. In some cases, scaling and normalization are also used for computational simplicity. However, to our best knowledge, the validity of those various forms of scaling and normalization has not been studied in a rigorous manner. In this study, we investigate the validity of various scalings and normalizations that have appeared in the literature to calculate mobile fractions and correct for photofading and assess their consistency with FRAP equations. As a test case, we consider linear or affine scaling of normal or anomalous diffusion FRAP equations in combination with scaling for immobile fractions. We also consider exponential scaling of either FRAP equations or FRAP data to correct for photofading. Using a combination of theoretical and experimental approaches, we show that compatible scaling schemes should be applied in the correct sequential order; otherwise, erroneous results may be obtained. We propose a hierarchical workflow to carry out FRAP data analysis and discuss the broader implications of our findings for FRAP data analysis using a variety of kinetic models.
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Affiliation(s)
- Minchul Kang
- School of Science, Technology & Engineering Management, St. Thomas University, Miami Gardens, Florida, USA
- * E-mail:
| | - Manuel Andreani
- School of Science, Technology & Engineering Management, St. Thomas University, Miami Gardens, Florida, USA
| | - Anne K. Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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A customized light sheet microscope to measure spatio-temporal protein dynamics in small model organisms. PLoS One 2015; 10:e0127869. [PMID: 26000610 PMCID: PMC4441442 DOI: 10.1371/journal.pone.0127869] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 04/20/2015] [Indexed: 12/24/2022] Open
Abstract
We describe a customizable and cost-effective light sheet microscopy (LSM) platform for rapid three-dimensional imaging of protein dynamics in small model organisms. The system is designed for high acquisition speeds and enables extended time-lapse in vivo experiments when using fluorescently labeled specimens. We demonstrate the capability of the setup to monitor gene expression and protein localization during ageing and upon starvation stress in longitudinal studies in individual or small groups of adult Caenorhabditis elegans nematodes. The system is equipped to readily perform fluorescence recovery after photobleaching (FRAP), which allows monitoring protein recovery and distribution under low photobleaching conditions. Our imaging platform is designed to easily switch between light sheet microscopy and optical projection tomography (OPT) modalities. The setup permits monitoring of spatio-temporal expression and localization of ageing biomarkers of subcellular size and can be conveniently adapted to image a wide range of small model organisms and tissue samples.
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Cui Y, Irudayaraj J. Inside single cells: quantitative analysis with advanced optics and nanomaterials. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2014; 7:387-407. [PMID: 25430077 DOI: 10.1002/wnan.1321] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/17/2014] [Accepted: 10/29/2014] [Indexed: 01/08/2023]
Abstract
Single-cell explorations offer a unique window to inspect molecules and events relevant to mechanisms and heterogeneity constituting the central dogma of biology. A large number of nucleic acids, proteins, metabolites, and small molecules are involved in determining and fine-tuning the state and function of a single cell at a given time point. Advanced optical platforms and nanotools provide tremendous opportunities to probe intracellular components with single-molecule accuracy, as well as promising tools to adjust single-cell activity. To obtain quantitative information (e.g., molecular quantity, kinetics, and stoichiometry) within an intact cell, achieving the observation with comparable spatiotemporal resolution is a challenge. For single-cell studies, both the method of detection and the biocompatibility are critical factors as they determine the feasibility, especially when considering live-cell analysis. Although a considerable proportion of single-cell methodologies depend on specialized expertise and expensive instruments, it is our expectation that the information content and implication will outweigh the costs given the impact on life science enabled by single-cell analysis.
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Affiliation(s)
- Yi Cui
- Department of Agricultural and Biological Engineering, Bindley Bioscience Center and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
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Assessing cellular efficacy of bromodomain inhibitors using fluorescence recovery after photobleaching. Epigenetics Chromatin 2014; 7:14. [PMID: 25097667 PMCID: PMC4115480 DOI: 10.1186/1756-8935-7-14] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Accepted: 06/23/2014] [Indexed: 12/19/2022] Open
Abstract
Background Acetylation of lysine residues in histone tails plays an important role in the regulation of gene transcription. Bromdomains are the readers of acetylated histone marks, and, consequently, bromodomain-containing proteins have a variety of chromatin-related functions. Moreover, they are increasingly being recognised as important mediators of a wide range of diseases. The first potent and selective bromodomain inhibitors are beginning to be described, but the diverse or unknown functions of bromodomain-containing proteins present challenges to systematically demonstrating cellular efficacy and selectivity for these inhibitors. Here we assess the viability of fluorescence recovery after photobleaching (FRAP) assays as a target agnostic method for the direct visualisation of an on-target effect of bromodomain inhibitors in living cells. Results Mutation of a conserved asparagine crucial for binding to acetylated lysines in the bromodomains of BRD3, BRD4 and TRIM24 all resulted in reduction of FRAP recovery times, indicating loss of or significantly reduced binding to acetylated chromatin, as did the addition of known inhibitors. Significant differences between wild type and bromodomain mutants for ATAD2, BAZ2A, BRD1, BRD7, GCN5L2, SMARCA2 and ZMYND11 required the addition of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) to amplify the binding contribution of the bromodomain. Under these conditions, known inhibitors decreased FRAP recovery times back to mutant control levels. Mutation of the bromodomain did not alter FRAP recovery times for full-length CREBBP, even in the presence of SAHA, indicating that other domains are primarily responsible for anchoring CREBBP to chromatin. However, FRAP assays with multimerised CREBBP bromodomains resulted in a good assay to assess the efficacy of bromodomain inhibitors to this target. The bromodomain and extraterminal protein inhibitor PFI-1 was inactive against other bromodomain targets, demonstrating the specificity of the method. Conclusions Viable FRAP assays were established for 11 representative bromodomain-containing proteins that broadly cover the bromodomain phylogenetic tree. Addition of SAHA can overcome weak binding to chromatin, and the use of tandem bromodomain constructs can eliminate masking effects of other chromatin binding domains. Together, these results demonstrate that FRAP assays offer a potentially pan-bromodomain method for generating cell-based assays, allowing the testing of compounds with respect to cell permeability, on-target efficacy and selectivity.
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50
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Conway JRW, Carragher NO, Timpson P. Developments in preclinical cancer imaging: innovating the discovery of therapeutics. Nat Rev Cancer 2014; 14:314-28. [PMID: 24739578 DOI: 10.1038/nrc3724] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Integrating biological imaging into early stages of the drug discovery process can provide invaluable readouts of drug activity within complex disease settings, such as cancer. Iterating this approach from initial lead compound identification in vitro to proof-of-principle in vivo analysis represents a key challenge in the drug discovery field. By embracing more complex and informative models in drug discovery, imaging can improve the fidelity and statistical robustness of preclinical cancer studies. In this Review, we highlight how combining advanced imaging with three-dimensional systems and intravital mouse models can provide more informative and disease-relevant platforms for cancer drug discovery.
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Affiliation(s)
- James R W Conway
- Garvan Institute of Medical Research and The Kinghorn Cancer Centre Sydney, St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, New South Wales 2010, Sydney, Australia
| | - Neil O Carragher
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, EH4 2XR, UK
| | - Paul Timpson
- Garvan Institute of Medical Research and The Kinghorn Cancer Centre Sydney, St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, New South Wales 2010, Sydney, Australia
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