1
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Vieira MFM, Hernandez G, Zhong Q, Arbesú M, Veloso T, Gomes T, Martins ML, Monteiro H, Frazão C, Frankel G, Zanzoni A, Cordeiro TN. The pathogen-encoded signalling receptor Tir exploits host-like intrinsic disorder for infection. Commun Biol 2024; 7:179. [PMID: 38351154 PMCID: PMC10864410 DOI: 10.1038/s42003-024-05856-9] [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: 11/23/2022] [Accepted: 01/26/2024] [Indexed: 02/16/2024] Open
Abstract
The translocated intimin receptor (Tir) is an essential type III secretion system (T3SS) effector of attaching and effacing pathogens contributing to the global foodborne disease burden. Tir acts as a cell-surface receptor in host cells, rewiring intracellular processes by targeting multiple host proteins. We investigated the molecular basis for Tir's binding diversity in signalling, finding that Tir is a disordered protein with host-like binding motifs. Unexpectedly, also are several other T3SS effectors. By an integrative approach, we reveal that Tir dimerises via an antiparallel OB-fold within a highly disordered N-terminal cytosolic domain. Also, it has a long disordered C-terminal cytosolic domain partially structured at host-like motifs that bind lipids. Membrane affinity depends on lipid composition and phosphorylation, highlighting a previously unrecognised host interaction impacting Tir-induced actin polymerisation and cell death. Furthermore, multi-site tyrosine phosphorylation enables Tir to engage host SH2 domains in a multivalent fuzzy complex, consistent with Tir's scaffolding role and binding promiscuity. Our findings provide insights into the intracellular Tir domains, highlighting the ability of T3SS effectors to exploit host-like protein disorder as a strategy for host evasion.
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Affiliation(s)
- Marta F M Vieira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Guillem Hernandez
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Qiyun Zhong
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Miguel Arbesú
- Department of NMR-supported Structural Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- InstaDeep Ltd, 5 Merchant Square, London, UK
| | - Tiago Veloso
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Tiago Gomes
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Maria L Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Hugo Monteiro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Carlos Frazão
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | - Gad Frankel
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Andreas Zanzoni
- Aix-Marseille Université, Inserm, TAGC, UMR_S1090, Marseille, France
| | - Tiago N Cordeiro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal.
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2
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Prakaash D, Cook GP, Acuto O, Kalli AC. Multi-scale simulations of the T cell receptor reveal its lipid interactions, dynamics and the arrangement of its cytoplasmic region. PLoS Comput Biol 2021; 17:e1009232. [PMID: 34280187 PMCID: PMC8321403 DOI: 10.1371/journal.pcbi.1009232] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 07/29/2021] [Accepted: 07/01/2021] [Indexed: 12/27/2022] Open
Abstract
The T cell receptor (TCR-CD3) initiates T cell activation by binding to peptides of Major Histocompatibility Complexes (pMHC). The TCR-CD3 topology is well understood but the arrangement and dynamics of its cytoplasmic tails remains unknown, limiting our grasp of the signalling mechanism. Here, we use molecular dynamics simulations and modelling to investigate the entire TCR-CD3 embedded in a model membrane. Our study demonstrates conformational changes in the extracellular and transmembrane domains, and the arrangement of the TCR-CD3 cytoplasmic tails. The cytoplasmic tails formed highly interlaced structures while some tyrosines within the immunoreceptor tyrosine-based activation motifs (ITAMs) penetrated the hydrophobic core of the membrane. Interactions between the cytoplasmic tails and phosphatidylinositol phosphate lipids in the inner membrane leaflet led to the formation of a distinct anionic lipid fingerprint around the TCR-CD3. These results increase our understanding of the TCR-CD3 dynamics and the importance of membrane lipids in regulating T cell activation.
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Affiliation(s)
- Dheeraj Prakaash
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds, United Kingdom
- Astbury Center for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Graham P. Cook
- Leeds Institute of Medical Research at St James’s, School of Medicine, University of Leeds, Leeds, United Kingdom
| | - Oreste Acuto
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Antreas C. Kalli
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds, United Kingdom
- Astbury Center for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail:
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3
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Branfield S, Washington AV. The enigmatic nature of the triggering receptor expressed in myeloid cells -1 (TLT- 1). Platelets 2021; 32:753-760. [PMID: 33560928 DOI: 10.1080/09537104.2021.1881948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Receptors are important pharmacological targets on cells. The Triggering Receptor Expressed on Myeloid Cells (TREM) - Like Transcript - 1 is an abundant, yet little understood, platelet receptor. It is a single Ig domain containing receptor isolated in the α-granules of resting platelets and brought to the platelet surface upon activation. On platelets, the integrin αIIbβ3 is the major receptor having roughly 80,000 copies. αIIbβ3 is a heterodimeric multidomain structure that mediates platelet aggregation through its interaction with the plasma protein fibrinogen. Anti-platelet drugs have successfully targeted αIIbβ3 to control thrombosis. Like αIIbβ3, TLT-1 also binds fibrinogen, making its role in platelet function somewhat obscure. In this review, we highlight the known structural features of TLT-1 and present the challenges of understanding TLT-1 function. In our analysis of the dynamics of the platelet surface after activation we propose a model in which TLT-1 supports αIIbβ3 function as a mechanoreceptor that may direct platelets toward immune function.
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Affiliation(s)
- Siobhan Branfield
- , Department of Biology, University of Puerto Rico- Rio Piedras- Molecular Science Research Center, San Juan, Puerto Rico
| | - A Valance Washington
- , Department of Biology, University of Puerto Rico- Rio Piedras- Molecular Science Research Center, San Juan, Puerto Rico
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4
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Clemens L, Dushek O, Allard J. Intrinsic Disorder in the T Cell Receptor Creates Cooperativity and Controls ZAP70 Binding. Biophys J 2020; 120:379-392. [PMID: 33285117 PMCID: PMC7840419 DOI: 10.1016/j.bpj.2020.11.2266] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 10/24/2020] [Accepted: 11/19/2020] [Indexed: 12/31/2022] Open
Abstract
Many immunoreceptors have cytoplasmic domains that are intrinsically disordered (i.e., have high configurational entropy), have multiple sites of posttranslational modification (e.g., tyrosine phosphorylation), and participate in nonlinear signaling pathways (e.g., exhibiting switch-like behavior). Several hypotheses to explain the origin of these nonlinearities fall under the broad hypothesis that modification at one site changes the immunoreceptor’s entropy, which in turn changes further modification dynamics. Here, we use coarse-grain simulation to study three scenarios, all related to the chains that constitute the T cell receptor (TCR). We find that first, if phosphorylation induces local changes in the flexibility of the TCR ζ-chain, this naturally leads to rate enhancements and cooperativity. Second, we find that TCR CD3ɛ can provide a switch by modulating its residence in the plasma membrane. By constraining our model to be consistent with the previous observation that both basic residues and phosphorylation control membrane residence, we find that there is only a moderate rate enhancement of 10% between first and subsequent phosphorylation events. Third, we find that volume constraints do not limit the number of ZAP70s that can bind the TCR but that entropic penalties lead to a 200-fold decrease in binding rate by the seventh ZAP70, potentially explaining the observation that each TCR has around six ZAP70 molecules bound after receptor triggering. In all three scenarios, our results demonstrate that phenomena that change an immunoreceptor chain’s entropy (stiffening, confinement to a membrane, and multiple simultaneous binding) can lead to nonlinearities (rate enhancement, switching, and negative cooperativity) in how the receptor participates in signaling. These polymer-entropy-driven nonlinearities may augment the nonlinearities that arise from, e.g., kinetic proofreading and cluster formation. They also suggest different design strategies for engineered receptors, e.g., whether or not to put signaling modules on one chain or multiple clustered chains.
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Affiliation(s)
- Lara Clemens
- Center for Complex Biological Systems, University of California Irvine, Irvine, California
| | - Omer Dushek
- Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Jun Allard
- Center for Complex Biological Systems, University of California Irvine, Irvine, California; Department of Mathematics and Department of Physics and Astronomy, University of California Irvine, Irvine, California.
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5
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Schamel WW, Alarcon B, Minguet S. The TCR is an allosterically regulated macromolecular machinery changing its conformation while working. Immunol Rev 2020; 291:8-25. [PMID: 31402501 DOI: 10.1111/imr.12788] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 05/30/2019] [Indexed: 12/13/2022]
Abstract
The αβ T-cell receptor (TCR) is a multiprotein complex controlling the activation of T cells. Although the structure of the complete TCR is not known, cumulative evidence supports that the TCR cycles between different conformational states that are promoted either by thermal motion or by force. These structural transitions determine whether the TCR engages intracellular effectors or not, regulating TCR phosphorylation and signaling. As for other membrane receptors, ligand binding selects and stabilizes the TCR in active conformations, and/or switches the TCR to activating states that were not visited before ligand engagement. Here we review the main models of TCR allostery, that is, ligand binding at TCRαβ changes the structure at CD3 and ζ. (a) The ITAM and proline-rich sequence exposure model, in which the TCR's cytoplasmic tails shield each other and ligand binding exposes them for phosphorylation. (b) The membrane-ITAM model, in which the CD3ε and ζ tails are sequestered inside the membrane and again ligand binding exposes them. (c) The mechanosensor model in which ligand binding exerts force on the TCR, inducing structural changes that allow signaling. Since these models are complementary rather than competing, we propose a unified model that aims to incorporate all existing data.
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Affiliation(s)
- Wolfgang W Schamel
- Department of Immunology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.,Center of Chronic Immunodeficiency CCI, University Clinics and Medical Faculty, Freiburg, Germany
| | - Balbino Alarcon
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | - Susana Minguet
- Department of Immunology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.,Center of Chronic Immunodeficiency CCI, University Clinics and Medical Faculty, Freiburg, Germany
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6
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Blumenthal D, Burkhardt JK. Multiple actin networks coordinate mechanotransduction at the immunological synapse. J Cell Biol 2020; 219:e201911058. [PMID: 31977034 PMCID: PMC7041673 DOI: 10.1083/jcb.201911058] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 12/31/2019] [Accepted: 01/02/2020] [Indexed: 12/26/2022] Open
Abstract
Activation of naive T cells by antigen-presenting cells (APCs) is an essential step in mounting an adaptive immune response. It is known that antigen recognition and T cell receptor (TCR) signaling depend on forces applied by the T cell actin cytoskeleton, but until recently, the underlying mechanisms have been poorly defined. Here, we review recent advances in the field, which show that specific actin-dependent structures contribute to the process in distinct ways. In essence, T cell priming involves a tug-of-war between the cytoskeletons of the T cell and the APC, where the actin cytoskeleton serves as a mechanical intermediate that integrates force-dependent signals. We consider each of the relevant actin-rich T cell structures separately and address how they work together at the topologically and temporally complex cell-cell interface. In addition, we address how this mechanobiology can be incorporated into canonical immunological models to improve how these models explain T cell sensitivity and antigenic specificity.
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Affiliation(s)
| | - Janis K. Burkhardt
- Department of Pathology and Laboratory Medicine, Children’s Hospital of Philadelphia Research Institute and Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
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7
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Dube N, Marzinek JK, Glen RC, Bond PJ. The structural basis for membrane assembly of immunoreceptor signalling complexes. J Mol Model 2019; 25:277. [PMID: 31456056 DOI: 10.1007/s00894-019-4165-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 08/15/2019] [Indexed: 11/25/2022]
Abstract
Immunoreceptors are TM complexes that consist of separate ligand-binding and signal-transducing modules. Mounting evidence suggests that interactions with the local environment may influence the architecture of these TM domains, which assemble via crucial sets of conserved ionisable residues, and also control the peripheral association of immunoreceptor tyrosine-based activation motifs (ITAMs) whose phosphorylation triggers cytoplasmic signalling cascades. We now report a molecular dynamics (MD) simulation study of the archetypal T cell receptor (TCR) and its cluster of differentiation 3 (CD3) signalling partners, along with the analogous DNAX-activation protein of 12 kDa (DAP12)/natural killer group 2C (NKG2C) complex. Based on > 15 μs of explicitly solvated, atomic-resolution sampling, we explore molecular aspects of immunoreceptor complex stability in different functionally relevant states. A novel alchemical approach is used to simulate the cytoplasmic CD3ε tail at different depths within lipid bilayer models, revealing that the conformation and cytoplasmic exposure of ITAMs are highly sensitive to local enrichment by different lipid species and to phosphorylation. Furthermore, simulations of the TCR and DAP12 TM domains in various states of oligomerisation suggest that, during the early stages of assembly, stable membrane insertion is facilitated by the interfacial lipid/solvent environment and/or partial ionisation of charged residues. Collectively, our results indicate that the architecture and mechanisms of signal transduction in immunoreceptor complexes are tightly regulated by interactions with the microenvironment.
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Affiliation(s)
- Namita Dube
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
- Tata Institute of Fundamental Research, 36/P, Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad, 500107, India
| | - Jan K Marzinek
- Bioinformatics Institute (A*STAR), 30 Biopolis Str., #07-01 Matrix, Singapore, 138671, Singapore
| | - Robert C Glen
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
- Division of Integrative Systems Medicine and Digestive Diseases, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Peter J Bond
- Bioinformatics Institute (A*STAR), 30 Biopolis Str., #07-01 Matrix, Singapore, 138671, Singapore.
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore.
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8
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Connolly A, Gagnon E. Electrostatic interactions: From immune receptor assembly to signaling. Immunol Rev 2019; 291:26-43. [DOI: 10.1111/imr.12769] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 04/30/2019] [Indexed: 12/21/2022]
Affiliation(s)
- Audrey Connolly
- Institut de Recherche en Immunologie et Cancérologie/Institute for Research in Immunology and Cancer Montréal Québec Canada
- Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine Université de Montréal Montréal Québec Canada
| | - Etienne Gagnon
- Institut de Recherche en Immunologie et Cancérologie/Institute for Research in Immunology and Cancer Montréal Québec Canada
- Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine Université de Montréal Montréal Québec Canada
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9
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Cheng H, Schwell V, Curtis BR, Fazlieva R, Roder H, Campbell KS. Conformational Changes in the Cytoplasmic Region of KIR3DL1 upon Interaction with SHP-2. Structure 2019; 27:639-650.e2. [PMID: 30773397 DOI: 10.1016/j.str.2019.01.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 11/07/2018] [Accepted: 01/18/2019] [Indexed: 12/29/2022]
Abstract
KIR3DL1 is an inhibitory killer cell immunoglobulin-like receptor (KIR) that negatively regulates natural killer cell cytotoxicity. The KIR3DL1 cytoplasmic region (3DL1-cyto) is disordered and can be dissected into three segments: (I) H340-V351; (II) M352-D371; and (III) P372-P423. NMR studies indicate that segment II can dynamically adopt a loop-like conformation, and segments I and III can form dynamic helices that may mediate binding to membranes, particularly in the region around the N-terminal (N) immunoreceptor tyrosine-based inhibitory motif (ITIM), consistent with its role in signaling. Furthermore, individual SH2 domains of SHP-2 strongly engage with the unphosphorylated N-ITIM of 3DL1-cyto, while binding of the tandem SHP-2 SH2 domains to the bis-phosphorylated ITIMs results in more extensive conformational changes in segments I and III. The findings enhance our understanding of KIR function and how ITIMs in a target receptor operate in concert to engage the tandem SH2 domains of SHP-2.
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Affiliation(s)
- Hong Cheng
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
| | - Vered Schwell
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Brett R Curtis
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Ruzaliya Fazlieva
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Heinrich Roder
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Kerry S Campbell
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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10
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Natarajan K, Jiang J, May NA, Mage MG, Boyd LF, McShan AC, Sgourakis NG, Bax A, Margulies DH. The Role of Molecular Flexibility in Antigen Presentation and T Cell Receptor-Mediated Signaling. Front Immunol 2018; 9:1657. [PMID: 30065727 PMCID: PMC6056622 DOI: 10.3389/fimmu.2018.01657] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 07/04/2018] [Indexed: 01/20/2023] Open
Abstract
Antigen presentation is a cellular process that involves a number of steps, beginning with the production of peptides by proteolysis or aberrant synthesis and the delivery of peptides to cellular compartments where they are loaded on MHC class I (MHC-I) or MHC class II (MHC-II) molecules. The selective loading and editing of high-affinity immunodominant antigens is orchestrated by molecular chaperones: tapasin/TAP-binding protein, related for MHC-I and HLA-DM for MHC-II. Once peptide/MHC (pMHC) complexes are assembled, following various steps of quality control, they are delivered to the cell surface, where they are available for identification by αβ receptors on CD8+ or CD4+ T lymphocytes. In addition, recognition of cell surface peptide/MHC-I complexes by natural killer cell receptors plays a regulatory role in some aspects of the innate immune response. Many of the components of the pathways of antigen processing and presentation and of T cell receptor (TCR)-mediated signaling have been studied extensively by biochemical, genetic, immunological, and structural approaches over the past several decades. Until recently, however, dynamic aspects of the interactions of peptide with MHC, MHC with molecular chaperones, or of pMHC with TCR have been difficult to address experimentally, although computational approaches such as molecular dynamics (MD) simulations have been illuminating. Studies exploiting X-ray crystallography, cryo-electron microscopy, and multidimensional nuclear magnetic resonance (NMR) spectroscopy are beginning to reveal the importance of molecular flexibility as it pertains to peptide loading onto MHC molecules, the interactions between pMHC and TCR, and subsequent TCR-mediated signals. In addition, recent structural and dynamic insights into how molecular chaperones define peptide selection and fine-tune the MHC displayed antigen repertoire are discussed. Here, we offer a review of current knowledge that highlights experimental data obtained by X-ray crystallography and multidimensional NMR methodologies. Collectively, these findings strongly support a multifaceted role for protein plasticity and conformational dynamics throughout the antigen processing and presentation pathway in dictating antigen selection and recognition.
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Affiliation(s)
- Kannan Natarajan
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Jiansheng Jiang
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Nathan A May
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Michael G Mage
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Lisa F Boyd
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Andrew C McShan
- Department of Chemistry and Biochemistry, University of California at Santa Cruz, Santa Cruz, CA, United States
| | - Nikolaos G Sgourakis
- Department of Chemistry and Biochemistry, University of California at Santa Cruz, Santa Cruz, CA, United States
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - David H Margulies
- Molecular Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
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11
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Zimmermann K, Eells R, Heinrich F, Rintoul S, Josey B, Shekhar P, Lösche M, Stern LJ. The cytosolic domain of T-cell receptor ζ associates with membranes in a dynamic equilibrium and deeply penetrates the bilayer. J Biol Chem 2017; 292:17746-17759. [PMID: 28893902 PMCID: PMC5663876 DOI: 10.1074/jbc.m117.794370] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 08/21/2017] [Indexed: 11/06/2022] Open
Abstract
Interactions between lipid bilayers and the membrane-proximal regions of membrane-associated proteins play important roles in regulating membrane protein structure and function. The T-cell antigen receptor is an assembly of eight single-pass membrane-spanning subunits on the surface of T lymphocytes that initiates cytosolic signaling cascades upon binding antigens presented by MHC-family proteins on antigen-presenting cells. Its ζ-subunit contains multiple cytosolic immunoreceptor tyrosine-based activation motifs involved in signal transduction, and this subunit by itself is sufficient to couple extracellular stimuli to intracellular signaling events. Interactions of the cytosolic domain of ζ (ζcyt) with acidic lipids have been implicated in the initiation and regulation of transmembrane signaling. ζcyt is unstructured in solution. Interaction with acidic phospholipids induces structure, but its disposition when bound to lipid bilayers is controversial. Here, using surface plasmon resonance and neutron reflection, we characterized the interaction of ζcyt with planar lipid bilayers containing mixtures of acidic and neutral lipids. We observed two binding modes of ζcyt to the bilayers in dynamic equilibrium: one in which ζcyt is peripherally associated with lipid headgroups and one in which it penetrates deeply into the bilayer. Such an equilibrium between the peripherally bound and embedded forms of ζcyt apparently controls accessibility of the immunoreceptor tyrosine-based activation signal transduction pathway. Our results reconcile conflicting findings of the ζ structure reported in previous studies and provide a framework for understanding how lipid interactions regulate motifs to tyrosine kinases and may regulate the T-cell antigen receptor biological activities for this cell-surface receptor system.
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Affiliation(s)
| | | | - Frank Heinrich
- the Departments of Physics and
- the National Institute of Standards and Technology (NIST) Center for Neutron Research, Gaithersburg, Maryland 20899
| | | | | | | | - Mathias Lösche
- the Departments of Physics and
- the National Institute of Standards and Technology (NIST) Center for Neutron Research, Gaithersburg, Maryland 20899
- Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, and
| | - Lawrence J Stern
- From the Departments of Pathology and
- Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
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12
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Natarajan K, McShan AC, Jiang J, Kumirov VK, Wang R, Zhao H, Schuck P, Tilahun ME, Boyd LF, Ying J, Bax A, Margulies DH, Sgourakis NG. An allosteric site in the T-cell receptor Cβ domain plays a critical signalling role. Nat Commun 2017; 8:15260. [PMID: 28508865 PMCID: PMC5440810 DOI: 10.1038/ncomms15260] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 03/14/2017] [Indexed: 12/21/2022] Open
Abstract
The molecular mechanism through which the interaction of a clonotypic αβ T-cell receptor (TCR) with a peptide-loaded major histocompatibility complex (p/MHC) leads to T-cell activation is not yet fully understood. Here we exploit a high-affinity TCR (B4.2.3) to examine the structural changes that accompany binding to its p/MHC ligand (P18-I10/H2-Dd). In addition to conformational changes in complementarity-determining regions (CDRs) of the TCR seen in comparison of unliganded and bound X-ray structures, NMR characterization of the TCR β-chain dynamics reveals significant chemical shift effects in sites removed from the MHC-binding site. Remodelling of electrostatic interactions near the Cβ H3 helix at the membrane-proximal face of the TCR, a region implicated in interactions with the CD3 co-receptor, suggests a possible role for an allosteric mechanism in TCR signalling. The contribution of these TCR residues to signal transduction is supported by mutagenesis and T-cell functional assays.
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MESH Headings
- Allosteric Site/immunology
- Animals
- Complementarity Determining Regions/chemistry
- Complementarity Determining Regions/metabolism
- Crystallography, X-Ray
- Major Histocompatibility Complex/immunology
- Mice
- Molecular Dynamics Simulation
- Mutagenesis
- Peptides/metabolism
- Protein Binding/immunology
- Protein Domains/immunology
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Signal Transduction/immunology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
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Affiliation(s)
- Kannan Natarajan
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Andrew C. McShan
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Jiansheng Jiang
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Vlad K Kumirov
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Rui Wang
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Huaying Zhao
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Peter Schuck
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Mulualem E. Tilahun
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Lisa F. Boyd
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Jinfa Ying
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - David H. Margulies
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Nikolaos G. Sgourakis
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
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13
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Gagnon E, Connolly A, Dobbins J, Wucherpfennig KW. Studying Dynamic Plasma Membrane Binding of TCR-CD3 Chains During Immunological Synapse Formation Using Donor-Quenching FRET and FLIM-FRET. Methods Mol Biol 2017; 1584:259-289. [PMID: 28255707 DOI: 10.1007/978-1-4939-6881-7_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Over the last decade, advancements in the time and space resolution of microscopy technologies have enabled dissection of the molecular events involved in T cell Immunological Synapse (IS) formation. Using a combination of Förster Resonance Energy Transfer (FRET) and Fluorescence Lifetime Imagining Microscopy (FLIM), we have demonstrated dynamic plasma membrane binding by cytoplasmic domains of T cell receptor (TCR)-associated CD3 chains and other T cell transmembrane receptors. We have developed methods for imaging such membrane binding both at steady state and during receptor triggering at the IS. Plasma membrane binding by cytoplasmic domains may represent a novel mechanism for regulating the signaling function of important receptors in the immune system.
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Affiliation(s)
- Etienne Gagnon
- Department of Microbiology and Immunology, Institute for Research in Immunology and Cancer, Université de Montréal, PO Box 6128, Downtown Station, Montreal, Canada, H3C 3J7.
| | - Audrey Connolly
- Department of Microbiology and Immunology, Institute for Research in Immunology and Cancer, Université de Montréal, PO Box 6128, Downtown Station, Montreal, Canada, H3C 3J7
| | - Jessica Dobbins
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA
- Program in Immunology, Harvard Medical School, Boston, MA, 02115, USA
| | - Kai W Wucherpfennig
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA
- Program in Immunology, Harvard Medical School, Boston, MA, 02115, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA
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14
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Leconte J, Bagherzadeh Yazdchi S, Panneton V, Suh WK. Inducible costimulator (ICOS) potentiates TCR-induced calcium flux by augmenting PLCγ1 activation and actin remodeling. Mol Immunol 2016; 79:38-46. [PMID: 27693916 DOI: 10.1016/j.molimm.2016.09.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 09/12/2016] [Accepted: 09/26/2016] [Indexed: 11/16/2022]
Abstract
The inducible costimulator (ICOS) is a T cell costimulatory receptor that plays crucial roles in T cell differentiation and function. So far, ICOS has been shown to activate three signaling components: phosphoinositide 3-kinase (PI3K), intracellular calcium mobilization, and TANK binding kinase 1 (TBK1). By generating a knock-in strain of mice in which the ICOS gene is modified such that the ICOS-mediated PI3K pathway is selectively abrogated while the capacity of ICOS to mobilize intracellular calcium remains intact, we have shown that ICOS-mediated PI3K activation is required for some but not all T cell responses. This suggests that the ICOS-calcium signaling axis may explain some of the PI3K-independent ICOS functions. Further, a recent in vivo imaging study indicated that ICOS-dependent intracellular calcium flux facilitates cognate T cell-B cell interactions within the germinal center. However, how ICOS promotes TCR-mediated calcium flux has not been clear. Here we identified a membrane proximal motif in the cytoplasmic tail of ICOS that is essential for ICOS-assisted calcium signaling and demonstrate that ICOS can induce calcium flux independently of other signaling motifs. We also provide evidence that ICOS potentiates phospholipase Cγ1 (PLCγ1) activation to enhance calcium release from the intracellular pool. In parallel, acute ligation of ICOS without TCR co-engagement leads to activation of small GTPases, RhoA and Cdc42, consistent with the capacity of ICOS to induce actin remodeling. Importantly, interruption of actin dynamics during acute TCR or TCR-ICOS co-ligation severely impairs calcium flux in T cells even in the presence of activated PLCγ1. Thus, ICOS potentiates TCR-induced calcium flux by enhancing PLCγ1 activation and actin remodeling in a coordinated manner.
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Affiliation(s)
- Julien Leconte
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC H2W 1R7, Canada; Department of Microbiology, Infectiology, and Immunology, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Sahar Bagherzadeh Yazdchi
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC H2W 1R7, Canada; Department of Microbiology and Immunology, McGill University, Montreal, QC H3A 2B4, Canada
| | - Vincent Panneton
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC H2W 1R7, Canada; Department of Microbiology, Infectiology, and Immunology, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Woong-Kyung Suh
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC H2W 1R7, Canada; Department of Microbiology, Infectiology, and Immunology, University of Montreal, Montreal, QC H3T 1J4, Canada; Department of Microbiology and Immunology, McGill University, Montreal, QC H3A 2B4, Canada; Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada.
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15
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Dobbins J, Gagnon E, Godec J, Pyrdol J, Vignali DAA, Sharpe AH, Wucherpfennig KW. Binding of the cytoplasmic domain of CD28 to the plasma membrane inhibits Lck recruitment and signaling. Sci Signal 2016; 9:ra75. [PMID: 27460989 DOI: 10.1126/scisignal.aaf0626] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The T cell costimulatory receptor CD28 is required for the full activation of naïve T cells and for the development and maintenance of Foxp3(+) regulatory T (Treg) cells. We showed that the cytoplasmic domain of CD28 was bound to the plasma membrane in resting cells and that ligand binding to CD28 resulted in its release. Membrane binding by the CD28 cytoplasmic domain required two clusters of basic amino acid residues, which interacted with the negatively charged inner leaflet of the plasma membrane. These same clusters of basic residues also served as interaction sites for Lck, a Src family kinase critical for CD28 function. This signaling complex was further stabilized by the Lck-mediated phosphorylation of CD28 Tyr(207) and the subsequent binding of the Src homology 2 (SH2) domain of Lck to this phosphorylated tyrosine. Mutation of the basic clusters in the CD28 cytoplasmic domain reduced the recruitment to the CD28-Lck complex of protein kinase Cθ (PKCθ), which serves as a key effector kinase in the CD28 signaling pathway. Consequently, mutation of either a basic cluster or Tyr(207) impaired CD28 function in mice as shown by the reduced thymic differentiation of FoxP3(+) Treg cells. On the basis of these results, we propose a previously undescribed model for the initiation of CD28 signaling.
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Affiliation(s)
- Jessica Dobbins
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA. Program in Immunology, Harvard Medical School, Boston, MA 02115, USA
| | - Etienne Gagnon
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Jernej Godec
- Program in Immunology, Harvard Medical School, Boston, MA 02115, USA. Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Jason Pyrdol
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Dario A A Vignali
- Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA. Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA
| | - Arlene H Sharpe
- Program in Immunology, Harvard Medical School, Boston, MA 02115, USA. Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Kai W Wucherpfennig
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA. Program in Immunology, Harvard Medical School, Boston, MA 02115, USA. Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA.
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16
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Fealey ME, Mahling R, Rice AM, Dunleavy K, Kobany SEG, Lohese KJ, Horn B, Hinderliter A. Synaptotagmin I's Intrinsically Disordered Region Interacts with Synaptic Vesicle Lipids and Exerts Allosteric Control over C2A. Biochemistry 2016; 55:2914-26. [PMID: 27191789 DOI: 10.1021/acs.biochem.6b00085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Synaptotagmin I (Syt I) is a vesicle-localized integral membrane protein that senses the calcium ion (Ca(2+)) influx to trigger fast synchronous release of neurotransmitter. How the cytosolic domains of Syt I allosterically communicate to propagate the Ca(2+) binding signal throughout the protein is not well understood. In particular, it is unclear whether the intrinsically disordered region (IDR) between Syt I's transmembrane helix and first C2 domain (C2A) plays an important role in allosteric modulation of Ca(2+) binding. Moreover, the structural propensity of this IDR with respect to membrane lipid composition is unknown. Using differential scanning and isothermal titration calorimetry, we found that inclusion of the IDR does indeed allosterically modulate Ca(2+) binding within the first C2 domain. Additionally through application of nuclear magnetic resonance, we found that Syt I's IDR interacts with membranes whose lipid composition mimics that of a synaptic vesicle. These findings not only indicate that Syt I's IDR plays a role in regulating Syt I's Ca(2+) sensing but also indicate the IDR is exquisitely sensitive to the underlying membrane lipids. The latter observation suggests the IDR is a key route for communication of lipid organization to the adjacent C2 domains.
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Affiliation(s)
- Michael E Fealey
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States.,Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Ryan Mahling
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - Anne M Rice
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - Katie Dunleavy
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - Stephanie E G Kobany
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - K Jean Lohese
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - Benjamin Horn
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States
| | - Anne Hinderliter
- Department of Chemistry and Biochemistry, University of Minnesota-Duluth , Duluth, Minnesota 55812, United States.,Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota , Minneapolis, Minnesota 55455, United States
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17
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Structural biology of intrinsically disordered proteins: Revisiting unsolved mysteries. Biochimie 2016; 125:112-8. [PMID: 27004461 DOI: 10.1016/j.biochi.2016.03.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 03/17/2016] [Indexed: 01/30/2023]
Abstract
The emergence of intrinsically disordered proteins (IDPs) has challenged the classical protein structure-function paradigm by introducing a new paradigm of "coupled binding and folding". This paradigm suggests that IDPs fold upon binding to their partners. Further studies, however, revealed a novel and previously unrecognized phenomenon of "uncoupled binding and folding" suggesting that IDPs do not necessarily fold upon interaction with their lipid and protein partners. The complex and often unusual biophysics of IDPs makes structural characterization of these proteins and their complexes not only challenging but often resulting in opposite conclusions. For this reason, some crucial questions in this field remain unsolved for well over a decade. Considering an important role of IDPs in cellular regulation, signaling and control in health and disease, more efforts are needed to solve these mysteries. Here, I focus on two long-standing contradictions in the literature concerning dimerization and membrane-binding activities of IDPs. Molecular explanation of these discrepancies is provided. I also demonstrate how resolution of these critical issues in the field of IDPs results in our expanded understanding of cell function and has multiple applications in biology and medicine.
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18
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López CA, Sethi A, Goldstein B, Wilson BS, Gnanakaran S. Membrane-mediated regulation of the intrinsically disordered CD3ϵ cytoplasmic tail of the TCR. Biophys J 2015; 108:2481-2491. [PMID: 25992726 PMCID: PMC4457001 DOI: 10.1016/j.bpj.2015.03.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 01/27/2015] [Accepted: 03/02/2015] [Indexed: 10/23/2022] Open
Abstract
The regulation of T-cell-mediated immune responses depends on the phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) on T-cell receptors. Although many details of the signaling cascades are well understood, the initial mechanism and regulation of ITAM phosphorylation remains unknown. We used molecular dynamics simulations to study the influence of different compositions of lipid bilayers on the membrane association of the CD3ϵ cytoplasmic tails of the T-cell receptors. Our results show that binding of CD3ϵ to membranes is modulated by both the presence of negatively charged lipids and the lipid order of the membrane. Free-energy calculations reveal that the protein-membrane interaction is favored by the presence of nearby basic residues and the ITAM tyrosines. Phosphorylation minimizes membrane association, rendering the ITAM motif more accessible to binding partners. In systems mimicking biological membranes, the CD3ϵ chain localization is modulated by different facilitator lipids (e.g., gangliosides or phosphoinositols), revealing a plausible regulatory effect on activation through the regulation of lipid composition in cell membranes.
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Affiliation(s)
- Cesar A López
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico
| | - Anurag Sethi
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Byron Goldstein
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico
| | - Bridget S Wilson
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - S Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico; New Mexico Consortium, Los Alamos, New Mexico.
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19
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Sigalov AB. Unusual biophysics of immune signaling-related intrinsically disordered proteins. SELF NONSELF 2014; 1:271-281. [PMID: 21487502 DOI: 10.4161/self.1.4.13641] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 09/15/2010] [Accepted: 09/15/2010] [Indexed: 11/19/2022]
Abstract
Intrinsically disordered (ID) regions, the regions that lack a well-defined three-dimensional structure under physiological conditions, are preferentially located in the cytoplasmic segments of plasma membrane proteins, many of which are known to be involved in cell signaling. This is in line with our studies that demonstrated that cytoplasmic domains of signaling subunits of immune receptors, including those of ζ, CD3ε, CD3δ and CD3γ chains of T cell receptor, Igα and Igβ chains of B cell receptor as well as the Fc receptor γ chain represent a novel class of ID proteins (IDPs). The domains all have one or more copies of an immunoreceptor tyrosine-based activation motif, tyrosine residues of which are phosphorylated upon receptor engagement in an early and obligatory event in the signaling cascade. Our studies of these IDPs revealed several unusual biophysical phenomena, including (1) the specific dimerization of disordered protein molecules, (2) the fast and slow dimerization equilibrium, depending on the protein, (3) no disorder-to-order transition and the lack of significant chemical shift and peak intensity changes upon dimerization or interaction with a well-folded partner protein and (4) the dual mode of binding to model membranes (with and without folding), depending on the lipid bilayer stability. Here, I highlight several of these studies that not only facilitate a rethinking process of the fundamental paradigms in protein biophysics but also open new perspectives on the molecular mechanisms involved in receptor signaling.
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20
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Sgourakis NG, Natarajan K, Ying J, Vogeli B, Boyd LF, Margulies DH, Bax A. The structure of mouse cytomegalovirus m04 protein obtained from sparse NMR data reveals a conserved fold of the m02-m06 viral immune modulator family. Structure 2014; 22:1263-1273. [PMID: 25126960 DOI: 10.1016/j.str.2014.05.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 05/23/2014] [Accepted: 05/27/2014] [Indexed: 11/19/2022]
Abstract
Immunoevasins are key proteins used by viruses to subvert host immune responses. Determining their high-resolution structures is key to understanding virus-host interactions toward the design of vaccines and other antiviral therapies. Mouse cytomegalovirus encodes a unique set of immunoevasins, the m02-m06 family, that modulates major histocompatibility complex class I (MHC-I) antigen presentation to CD8+ T cells and natural killer cells. Notwithstanding the large number of genetic and functional studies, the structural biology of immunoevasins remains incompletely understood, largely because of crystallization bottlenecks. Here we implement a technology using sparse nuclear magnetic resonance data and integrative Rosetta modeling to determine the structure of the m04/gp34 immunoevasin extracellular domain. The structure reveals a β fold that is representative of the m02-m06 family of viral proteins, several of which are known to bind MHC-I molecules and interfere with antigen presentation, suggesting its role as a diversified immune regulation module.
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Affiliation(s)
- Nikolaos G Sgourakis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kannan Natarajan
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jinfa Ying
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Beat Vogeli
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lisa F Boyd
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - David H Margulies
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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21
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Popovic M, Zlatev V, Hodnik V, Anderluh G, Felli IC, Pongor S, Pintar A. Flexibility of the PDZ-binding motif in the micelle-bound form of Jagged-1 cytoplasmic tail. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1818:1706-16. [PMID: 22465068 DOI: 10.1016/j.bbamem.2012.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 03/13/2012] [Accepted: 03/14/2012] [Indexed: 01/07/2023]
Abstract
Human Jagged-1, one of the ligands of Notch receptors, is a transmembrane protein composed of a large extracellular region and a 125-residue cytoplasmic tail which bears a C-terminal PDZ recognition motif. To investigate the interaction between Jagged-1 cytoplasmic tail and the inner leaflet of the plasma membrane we determined, by solution NMR, the secondary structure and dynamics of the recombinant protein corresponding to the intracellular region of Jagged-1, J1_tmic, bound to negatively charged lysophospholipid micelles. NMR showed that the PDZ binding motif is preceded by four alpha-helical segments and that, despite the extensive interaction between J1_tmic and the micelle, the PDZ binding motif remains highly flexible. Binding of J1_tmic to negatively charged, but not to zwitterionic vesicles, was confirmed by surface plasmon resonance. To study the PDZ binding region in more detail, we prepared a peptide corresponding to the last 24 residues of Jagged-1, J1C24, and different phosphorylated variants of it. J1C24 displays a marked helical propensity and undergoes a coil-helix transition in the presence of negatively charged, but not zwitterionic, lysophospholipid micelles. Phosphorylation at different positions drastically decreases the helical propensity of the peptides and abolishes the coil-helix transition triggered by lysophospholipid micelles. We propose that phosphorylation of residues upstream of the PDZ binding motif may shift the equilibrium from an ordered, membrane-bound, interfacial form of Jagged-1 C-terminal region to a more disordered form with an increased accessibility of the PDZ recognition motif, thus playing an indirect role in the interaction between Jagged-1 and the PDZ-containing target protein.
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Affiliation(s)
- Matija Popovic
- International Centre for Genetic Engineering and Biotechnology, AREA Science Park Padriciano 99, 1-34149 Trieste, Italy
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22
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Herbert C, Schieborr U, Saxena K, Juraszek J, De Smet F, Alcouffe C, Bianciotto M, Saladino G, Sibrac D, Kudlinzki D, Sreeramulu S, Brown A, Rigon P, Herault JP, Lassalle G, Blundell TL, Rousseau F, Gils A, Schymkowitz J, Tompa P, Herbert JM, Carmeliet P, Gervasio FL, Schwalbe H, Bono F. Molecular mechanism of SSR128129E, an extracellularly acting, small-molecule, allosteric inhibitor of FGF receptor signaling. Cancer Cell 2013; 23:489-501. [PMID: 23597563 DOI: 10.1016/j.ccr.2013.02.018] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 12/12/2012] [Accepted: 02/19/2013] [Indexed: 01/12/2023]
Abstract
The fibroblast growth factor (FGF)/fibroblast growth factor receptor (FGFR) signaling network plays an important role in cell growth, survival, differentiation, and angiogenesis. Deregulation of FGFR signaling can lead to cancer development. Here, we report an FGFR inhibitor, SSR128129E (SSR), that binds to the extracellular part of the receptor. SSR does not compete with FGF for binding to FGFR but inhibits FGF-induced signaling linked to FGFR internalization in an allosteric manner, as shown by crystallography studies, nuclear magnetic resonance, Fourier transform infrared spectroscopy, molecular dynamics simulations, free energy calculations, structure-activity relationship analysis, and FGFR mutagenesis. Overall, SSR is a small molecule allosteric inhibitor of FGF/FGFR signaling, acting via binding to the extracellular part of the FGFR.
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Affiliation(s)
- Corentin Herbert
- E2C and LGCR-SDI Department, Sanofi Research and Development, 31100 Toulouse, France
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23
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Sigalov AB. Interplay Between Protein Order, Disorder and Oligomericity in Receptor Signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 725:50-73. [DOI: 10.1007/978-1-4614-0659-4_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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24
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Orekhov VY, Jaravine VA. Analysis of non-uniformly sampled spectra with multi-dimensional decomposition. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2011; 59:271-92. [PMID: 21920222 DOI: 10.1016/j.pnmrs.2011.02.002] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 02/21/2011] [Indexed: 05/04/2023]
Affiliation(s)
- Vladislav Yu Orekhov
- Swedish NMR Centre, University of Gothenburg, Box 465, 40530 Gothenburg, Sweden.
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25
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Sigalov AB. Uncoupled binding and folding of immune signaling-related intrinsically disordered proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 106:525-36. [DOI: 10.1016/j.pbiomolbio.2011.08.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 08/10/2011] [Indexed: 10/17/2022]
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26
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Residues within a lipid-associated segment of the PECAM-1 cytoplasmic domain are susceptible to inducible, sequential phosphorylation. Blood 2011; 117:6012-23. [PMID: 21464369 DOI: 10.1182/blood-2010-11-317867] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing receptors inhibit cellular responsiveness to immunoreceptor tyrosine-based activation motif (ITAM)-linked receptors. Although tyrosine phosphorylation is central to the initiation of both inhibitory ITIM and stimulatory ITAM signaling, the events that regulate receptor phosphorylation are incompletely understood. Previous studies have shown that ITAM tyrosines engage in structure-inducing interactions with the plasma membrane that must be relieved for phosphorylation to occur. Whether ITIM phosphorylation is similarly regulated and the mechanisms responsible for release from plasma membrane interactions to enable phosphorylation, however, have not been defined. PECAM-1 is a dual ITIM-containing receptor that inhibits ITAM-dependent responses in hematopoietic cells. We found that the PECAM-1 cytoplasmic domain is unstructured in an aqueous environment but adopts an α-helical conformation within a localized region on interaction with lipid vesicles that mimic the plasma membrane. The lipid-interacting segment contains the C-terminal ITIM tyrosine and a serine residue that undergo activation-dependent phosphorylation. The N-terminal ITIM is excluded from the lipid-interacting segment, and its phosphorylation is secondary to phosphorylation of the membrane-interacting C-terminal ITIM. On the basis of these findings, we propose a novel model for regulation of inhibitory signaling by ITIM-containing receptors that relies on reversible plasma membrane interactions and sequential ITIM phosphorylation.
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27
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Mittag T, Kay LE, Forman-Kay JD. Protein dynamics and conformational disorder in molecular recognition. J Mol Recognit 2010; 23:105-16. [PMID: 19585546 DOI: 10.1002/jmr.961] [Citation(s) in RCA: 196] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Recognition requires protein flexibility because it facilitates conformational rearrangements and induced-fit mechanisms upon target binding. Intrinsic disorder is an extreme on the continuous spectrum of possible protein dynamics and its role in recognition may seem counterintuitive. However, conformational disorder is widely found in many eukaryotic regulatory proteins involved in processes such as signal transduction and transcription. Disordered protein regions may in fact confer advantages over folded proteins in binding. Rapidly interconverting and diverse conformers may create mean electrostatic fields instead of presenting discrete charges. The resultant "polyelectrostatic" interactions allow for the utilization of post-translational modifications as a means to change the net charge and thereby modify the electrostatic interaction of a disordered region. Plasticity of disordered protein states enables steric advantages over folded proteins and allows for unique binding configurations. Disorder may also have evolutionary advantages, as it facilitates alternative splicing, domain shuffling and protein modularity. As proteins exist in a continuous spectrum of disorder, so do their complexes. Indeed, disordered regions in complexes may control the degree of motion between domains, mask binding sites, be targets of post-translational modifications, permit overlapping binding motifs, and enable transient binding of different binding partners, making them excellent candidates for signal integrators and explaining their prevalence in eukaryotic signaling pathways. "Dynamic" complexes arise if more than two transient protein interfaces are involved in complex formation of two binding partners in a dynamic equilibrium. "Disordered" complexes, in contrast, do not involve significant ordering of interacting protein segments but rely exclusively on transient contacts. The nature of these interactions is not well understood yet but advancements in the structural characterization of disordered states will help us gain insights into their function and their implications for health and disease.
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Affiliation(s)
- Tanja Mittag
- Program in Molecular Structure and Function, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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Sigalov AB. The SCHOOL of nature: II. Protein order, disorder and oligomericity in transmembrane signaling. SELF/NONSELF 2010; 1:89-102. [PMID: 21487511 PMCID: PMC3065667 DOI: 10.4161/self.1.2.11590] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 02/20/2010] [Accepted: 02/22/2010] [Indexed: 11/19/2022]
Abstract
Recent reports have revealed that many proteins that do not adopt globular structures under native conditions, thus termed intrinsically disordered proteins (IDPs), are involved in cell signaling. Intriguingly, physiologically relevant oligomerization of IDPs has been recently observed and shown to exhibit unique biophysical characteristics, including the lack of significant changes in chemical shift and peak intensity upon binding. In this work, I summarize several distinct features of protein disorder that are especially important as related to receptor-mediated transmembrane signal transduction. I also hypothesize that interactions of IDPs with their protein or lipid partners represent a general biphasic process with the "no disorder-to-order" fast interaction which, depending on the interacting partner, may or may not be accompanied by the slow formation of a secondary structure. Further, I suggest signaling-related functional connections between protein order, disorder, and oligomericity and hypothesize that receptor oligomerization induced or tuned upon ligand binding outside the cell is translated across the membrane into protein oligomerization inside the cell, thus providing a general platform, the Signaling Chain HOmoOLigomerization (SCHOOL) platform, for receptor-mediated signaling. This structures our current multidisciplinary knowledge and views of the mechanisms governing the coupling of recognition to signal transduction and cell response. Importantly, this approach not only reveals previously unrecognized striking similarities in the basic mechanistic principles of function of numerous functionally diverse and unrelated surface membrane receptors, but also suggests the similarity between therapeutic targets, thus opening new horizons for both fundamental and clinically relevant studies.
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Sigalov AB. Membrane binding of intrinsically disordered proteins: Critical importance of an appropriate membrane model. SELF NONSELF 2010; 1:129-132. [PMID: 21487515 DOI: 10.4161/self.1.2.11547] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 11/19/2022]
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Sigalov AB. Protein intrinsic disorder and oligomericity in cell signaling. ACTA ACUST UNITED AC 2010; 6:451-61. [DOI: 10.1039/b916030m] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Sigalov AB, Hendricks GM. Membrane binding mode of intrinsically disordered cytoplasmic domains of T cell receptor signaling subunits depends on lipid composition. Biochem Biophys Res Commun 2009; 389:388-93. [PMID: 19733547 DOI: 10.1016/j.bbrc.2009.09.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 09/01/2009] [Indexed: 02/08/2023]
Abstract
Intrinsically disordered cytoplasmic domains of T cell receptor (TCR) signaling subunits including zeta(cyt) and CD3epsilon(cyt) all contain one or more copies of an immunoreceptor tyrosine-based activation motif (ITAM), tyrosine residues of which are phosphorylated upon receptor triggering. Membrane binding-induced helical folding of zeta(cyt) and CD3epsilon(cyt) ITAMs is thought to control TCR activation. However, the question whether or not lipid binding of zeta(cyt) and CD3epsilon(cyt) is necessarily accompanied by a folding transition of ITAMs remains open. In this study, we investigate whether the membrane binding mechanisms of zeta(cyt) and CD3epsilon(cyt) depend on the membrane model used. Circular dichroic and fluorescence data indicate that binding of zeta(cyt) and CD3epsilon(cyt) to detergent micelles and unstable vesicles is accompanied by a disorder-to-order transition, whereas upon binding to stable vesicles these proteins remain unfolded. Using electron microscopy and dynamic light scattering, we show that upon protein binding, unstable vesicles fuse and rupture. In contrast, stable vesicles remain intact under these conditions. This suggests different membrane binding modes for zeta(cyt) and CD3epsilon(cyt) depending on the bilayer stability: (1) coupled binding and folding, and (2) binding without folding. These findings explain the long-standing puzzle in the literature and highlight the importance of the choice of an appropriate membrane model for protein-lipid interactions studies.
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Sigalov AB, Kim WM, Saline M, Stern LJ. The intrinsically disordered cytoplasmic domain of the T cell receptor zeta chain binds to the nef protein of simian immunodeficiency virus without a disorder-to-order transition. Biochemistry 2009; 47:12942-4. [PMID: 19012413 DOI: 10.1021/bi801602p] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intrinsically disordered proteins are thought to undergo coupled binding and folding upon interaction with their folded partners. In this study, we investigate whether binding of the intrinsically disordered T cell receptor zeta cytoplasmic tail to the well-folded simian immunodeficiency virus Nef core domain is accompanied by a disorder-to-order transition. We show that zeta forms a 1:1 complex with Nef and remains unfolded in the complex. Thus, our findings oppose the generally accepted view of the behavior of intrinsically disordered proteins and provide new evidence of the existence of specific interactions for unfolded protein molecules.
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Affiliation(s)
- Alexander B Sigalov
- Department of Pathology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01655, USA.
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Jaravine VA, Zhuravleva AV, Permi P, Ibraghimov I, Orekhov VY. Hyperdimensional NMR spectroscopy with nonlinear sampling. J Am Chem Soc 2008; 130:3927-36. [PMID: 18311971 DOI: 10.1021/ja077282o] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An approach is described for joint interleaved recording, real-time processing, and analysis of NMR data sets. The method employs multidimensional decomposition to find common information in a set of conventional triple-resonance spectra recorded in the nonlinear sampling mode, and builds a model of hyperdimensional (HD) spectrum. While preserving sensitivity per unit of measurement time and allowing for maximal spectral resolution, the approach reduces data collection time on average by 2 orders of magnitude compared to the conventional method. The 7-10 dimensional HD spectrum, which is represented as a set of deconvoluted 1D vectors, is easy to handle and amenable for automated analysis. The method is exemplified by automated assignment for two protein systems of low and high spectral complexity: ubiquitin (globular, 8 kDa) and zetacyt (naturally disordered, 13 kDa). The collection and backbone assignment of the data sets are achieved in real time after approximately 1 and 10 h, respectively. The approach removes the most critical time bottlenecks in data acquisition and analysis. Thus, it can significantly increase the value of NMR spectroscopy in structural biology, for example, in high-throughput structural genomics applications.
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Affiliation(s)
- Victor A Jaravine
- Swedish NMR Centre, Göteborg University, Box 465, 40530 Göteborg, Sweden
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Tian C, Vanoye CG, Kang C, Welch RC, Kim HJ, George AL, Sanders CR. Preparation, functional characterization, and NMR studies of human KCNE1, a voltage-gated potassium channel accessory subunit associated with deafness and long QT syndrome. Biochemistry 2007; 46:11459-72. [PMID: 17892302 PMCID: PMC2565491 DOI: 10.1021/bi700705j] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
KCNE1, also known as minK, is a member of the KCNE family of membrane proteins that modulate the function of KCNQ1 and certain other voltage-gated potassium channels (KV). Mutations in human KCNE1 cause congenital deafness and congenital long QT syndrome, an inherited predisposition to potentially life-threatening cardiac arrhythmias. Although its modulation of KCNQ1 function has been extensively characterized, many questions remain regarding KCNE1's structure and location within the channel complex. In this study, KCNE1 was overexpressed in Escherichia coli and purified. Micellar solutions of the protein were then microinjected into Xenopus oocytes expressing KCNQ1 channels, followed by electrophysiological recordings aimed at testing whether recombinant KCNE1 can co-assemble with the channel. Nativelike modulation of channel properties was observed following injection of KCNE1 in lyso-myristoylphosphatidylglycerol (LMPG) micelles, indicating that KCNE1 is not irreversibly misfolded and that LMPG is able to act as a vehicle for delivering membrane proteins into the membranes of viable cells. 1H-15N TROSY NMR experiments indicated that LMPG micelles are well-suited for structural studies of KCNE1, leading to assignment of its backbone resonances and to relaxation studies. The chemical shift data confirmed that KCNE1's secondary structure includes several alpha-helices and demonstrated that its distal C-terminus is disordered. Surprisingly, for KCNE1 in LMPG micelles, there appears to be a break in alpha-helicity at sites 59-61, near the middle of the transmembrane segment, a feature that is accompanied by increased local backbone mobility. Given that this segment overlaps with sites 57-59, which are known to play a critical role in modulating KCNQ1 channel activation kinetics, this unusual structural feature likely has considerable functional relevance.
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Affiliation(s)
| | | | | | | | | | | | - Charles R. Sanders
- To whom correspondence should be addressed: E-mail: ; phone: 615−936−3756; fax: 615−936−2211
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Popovic M, De Biasio A, Pintar A, Pongor S. The intracellular region of the Notch ligand Jagged-1 gains partial structure upon binding to synthetic membranes. FEBS J 2007; 274:5325-36. [PMID: 17892488 DOI: 10.1111/j.1742-4658.2007.06053.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Notch ligands are membrane-spanning proteins made of a large extracellular region, a transmembrane segment, and a approximately 100-200 residue cytoplasmic tail. The intracellular region of Jagged-1, one of the five ligands to Notch receptors in man, mediates protein-protein interactions through the C-terminal PDZ binding motif, is involved in receptor/ligand endocytosis triggered by mono-ubiquitination, and, as a consequence of regulated intramembrane proteolysis, can be released into the cytosol as a signaling fragment. The intracellular region of Jagged-1 may then exist in at least two forms: as a membrane-tethered protein located at the interface between the membrane and the cytoplasm, and as a soluble nucleocytoplasmic protein. Here, we report the characterization, in different environments, of a recombinant protein corresponding to the human Jagged-1 intracellular region (J1_tmic). In solution, J1_tmic behaves as an intrinsically disordered protein, but displays a significant helical propensity. In the presence of SDS micelles and phospholipid vesicles, used to mimick the interface between the plasma membrane and the cytosol, J1_tmic undergoes a substantial conformational change. We show that the interaction of J1_tmic with SDS micelles drives partial helix formation, as measured by circular dichroism, and that the helical content depends on pH in a reversible manner. An increase in the helical content is observed also in the presence of vesicles made of negatively charged, but not zwitterionic, phospholipids. We propose that this partial folding may have implications in the interactions of J1_tmic with its binding partners, as well as in its post-translational modifications.
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Affiliation(s)
- Matija Popovic
- Protein Structure and Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology, Padriciano, Trieste, Italy
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