1
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Rogers J, Ma R, Foote A, Hu Y, Salaita K. Force-Induced Site-Specific Enzymatic Cleavage Probes Reveal That Serial Mechanical Engagement Boosts T Cell Activation. J Am Chem Soc 2024; 146:7233-7242. [PMID: 38451498 PMCID: PMC10958510 DOI: 10.1021/jacs.3c08137] [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: 07/28/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 03/08/2024]
Abstract
The T cell membrane is studded with >104 T cell receptors (TCRs) that are used to scan target cells to identify short peptide fragments associated with viral infection or cancerous mutation. These peptides are presented as peptide-major-histocompatibility complexes (pMHCs) on the surface of virtually all nucleated cells. The TCR-pMHC complex forms at cell-cell junctions, is highly transient, and experiences mechanical forces. An important question in this area pertains to the role of the force duration in immune activation. Herein, we report the development of force probes that autonomously terminate tension within a time window following mechanical triggering. Force-induced site-specific enzymatic cleavage (FUSE) probes tune the tension duration by controlling the rate of a force-triggered endonuclease hydrolysis reaction. This new capability provides a method to study how the accumulated force duration contributes to T cell activation. We screened DNA sequences and identified FUSE probes that disrupt mechanical interactions with F > 7.1 piconewtons (pN) between TCRs and pMHCs. This rate of disruption, or force lifetime (τF), is tunable from tens of minutes down to 1.9 min. T cells challenged with FUSE probes with F > 7.1 pN presenting cognate antigens showed up to a 23% decrease in markers of early activation. FUSE probes with F > 17.0 pN showed weaker influence on T cell triggering further showing that TCR-pMHC with F > 17.0 pN are less frequent compared to F > 7.1 pN. Taken together, FUSE probes allow a new strategy to investigate the role of force dynamics in mechanotransduction broadly and specifically suggest a model of serial mechanical engagement boosting TCR activation.
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Affiliation(s)
- Jhordan Rogers
- Department
of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Rong Ma
- Department
of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Alexander Foote
- Department
of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Yuesong Hu
- Department
of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Khalid Salaita
- Department
of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
- Wallace
H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, United States
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2
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Robertson IB, Mulvaney R, Dieckmann N, Vantellini A, Canestraro M, Amicarella F, O'Dwyer R, Cole DK, Harper S, Dushek O, Kirk P. Tuning the potency and selectivity of ImmTAC molecules by affinity modulation. Clin Exp Immunol 2024; 215:105-119. [PMID: 37930865 PMCID: PMC10847821 DOI: 10.1093/cei/uxad120] [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: 06/01/2023] [Revised: 09/08/2023] [Accepted: 10/31/2023] [Indexed: 11/08/2023] Open
Abstract
T-cell-engaging bispecifics have great clinical potential for the treatment of cancer and infectious diseases. The binding affinity and kinetics of a bispecific molecule for both target and T-cell CD3 have substantial effects on potency and specificity, but the rules governing these relationships are not fully understood. Using immune mobilizing monoclonal TCRs against cancer (ImmTAC) molecules as a model, we explored the impact of altering affinity for target and CD3 on the potency and specificity of the redirected T-cell response. This class of bispecifics binds specific target peptides presented by human leukocyte antigen on the cell surface via an affinity-enhanced T-cell receptor and can redirect T-cell activation with an anti-CD3 effector moiety. The data reveal that combining a strong affinity TCR with an intermediate affinity anti-CD3 results in optimal T-cell activation, while strong affinity of both targeting and effector domains significantly reduces maximum cytokine release. Moreover, by optimizing the affinity of both parts of the molecule, it is possible to improve the selectivity. These results could be effectively modelled based on kinetic proofreading with limited signalling. This model explained the experimental observation that strong binding at both ends of the molecules leads to reduced activity, through very stable target-bispecific-effector complexes leading to CD3 entering a non-signalling dark state. These findings have important implications for the design of anti-CD3-based bispecifics with optimal biophysical parameters for both activity and specificity.
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Affiliation(s)
- Ian B Robertson
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Rachel Mulvaney
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Nele Dieckmann
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Alessio Vantellini
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Martina Canestraro
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | | | - Ronan O'Dwyer
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - David K Cole
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Stephen Harper
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
| | - Omer Dushek
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Peter Kirk
- Immunocore Limited, Drug Discovery and Protein Engineering, Abingdon, Oxon, UK
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3
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Rogers J, Ma R, Hu Y, Salaita K. Force-induced site-specific enzymatic cleavage probes reveal that serial mechanical engagement boosts T cell activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.07.552310. [PMID: 37609308 PMCID: PMC10441320 DOI: 10.1101/2023.08.07.552310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
The surface of T cells is studded with T cell receptors (TCRs) that are used to scan target cells to identify peptide-major histocompatibility complexes (pMHCs) signatures of viral infection or cancerous mutation. It is now established that the TCR-pMHC complex is highly transient and experiences mechanical forces that augment the fidelity of T cell activation. An important question in this area pertains to the role of force duration in immune activation. Herein, we report the development of force probes that autonomously terminate tension within a time window following mechanical triggering. Force-induced site-specific enzymatic cleavage (FUSE) probes tune tension duration by controlling the rate of a force-triggered endonuclease hydrolysis reaction. This new capability provides a method to study how accumulated force duration contributes to T cell activation. We screened DNA sequences and identified FUSE probes that disrupt mechanical interactions with F >7.1 piconewtons (pN) between TCRs and pMHCs. Force lifetimes (τF) are tunable from tens of min down to 1.9 min. T cells challenged with FUSE probes presenting cognate antigens with τF of 1.9 min demonstrated dampened markers of early activation, thus demonstrating that repeated mechanical sampling boosts TCR activation. Repeated mechanical sampling F >7.1 pN was found to be particularly critical at lower pMHC antigen densities, wherein the T cell activation declined by 23% with τF of 1.9 min. FUSE probes with F >17.0 pN response showed weaker influence on T cell triggering further showing that TCR-pMHC with F >17.0 pN are less frequent compared to F >7.1 pN. Taken together, FUSE probes allow a new strategy to investigate the role of force dynamics in mechanotransduction broadly and specifically suggest a model of serial mechanical engagement in antigen recognition.
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Affiliation(s)
- Jhordan Rogers
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia, 30322, USA
| | - Rong Ma
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia, 30322, USA
| | - Yuesong Hu
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia, 30322, USA
| | - Khalid Salaita
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia, 30322, USA
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, 30332, USA
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4
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Pineros-Rodriguez M, Richez L, Khadra A. Theoretical quantification of the polyvalent binding of nanoparticles coated with peptide-major histocompatibility complex to T cell receptor-nanoclusters. Math Biosci 2023; 358:108995. [PMID: 36924879 DOI: 10.1016/j.mbs.2023.108995] [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: 09/30/2022] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 03/17/2023]
Abstract
Nanoparticles (NPs) coated with peptide-major histocompatibility complexes (pMHCs) can be used as a therapy to treat autoimmune diseases. They do so by inducing the differentiation and expansion of disease-suppressing T regulatory type 1 (Tr1) cells by binding to their T cell receptors (TCRs) expressed as TCR-nanoclusters (TCRnc). Their efficacy can be controlled by adjusting NP size and number of pMHCs coated on them (referred to as valence). The binding of these NPs to TCRnc on T cells is thus polyvalent and occurs at three levels: the TCR-pMHC, NP-TCRnc and T cell levels. In this study, we explore how this polyvalent interaction is manifested and examine if it can facilitate T cell activation downstream. This is done by developing a multiscale biophysical model that takes into account the three levels of interactions and the geometrical complexity of the binding. Using the model, we quantify several key parameters associated with this interaction analytically and numerically, including the insertion probability that specifies the number of remaining pMHC binding sites in the contact area between T cells and NPs, the dwell time of interaction between NPs and TCRnc, carrying capacity of TCRnc, the distribution of covered and bound TCRs, and cooperativity in the binding of pMHCs within the contact area. The model was fit to previously published dose-response curves of interferon-γ obtained experimentally by stimulating a population of T cells with increasing concentrations of NPs at various valences and NP sizes. Exploring the parameter space of the model revealed that for an appropriate choice of the contact area angle, the model can produce moderate jumps between dose-response curves at low valences. This suggests that the geometry and kinetics of NP binding to TCRnc can act in synergy to facilitate T cell activation.
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Affiliation(s)
| | - Louis Richez
- Quantitative Life Sciences Program, McGill University, Montreal, Canada
| | - Anmar Khadra
- Department of Physiology, McGill University, Montreal, Canada.
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5
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Filali L, Puissegur MP, Cortacero K, Cussat-Blanc S, Khazen R, Van Acker N, Frenois FX, Abreu A, Lamant L, Meyer N, Vergier B, Müller S, McKenzie B, Valitutti S. Ultrarapid lytic granule release from CTLs activates Ca 2+-dependent synaptic resistance pathways in melanoma cells. SCIENCE ADVANCES 2022; 8:eabk3234. [PMID: 35171665 PMCID: PMC8849291 DOI: 10.1126/sciadv.abk3234] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Human cytotoxic T lymphocytes (CTLs) exhibit ultrarapid lytic granule secretion, but whether melanoma cells mobilize defense mechanisms with commensurate rapidity remains unknown. We used single-cell time-lapse microscopy to offer high spatiotemporal resolution analyses of subcellular events in melanoma cells upon CTL attack. Target cell perforation initiated an intracellular Ca2+ wave that propagated outward from the synapse within milliseconds and triggered lysosomal mobilization to the synapse, facilitating membrane repair and conferring resistance to CTL induced cytotoxicity. Inhibition of Ca2+ flux and silencing of synaptotagmin VII limited synaptic lysosomal exposure and enhanced cytotoxicity. Multiplexed immunohistochemistry of patient melanoma nodules combined with automated image analysis showed that melanoma cells facing CD8+ CTLs in the tumor periphery or peritumoral area exhibited significant lysosomal enrichment. Our results identified synaptic Ca2+ entry as the definitive trigger for lysosomal deployment to the synapse upon CTL attack and highlighted an unpredicted defensive topology of lysosome distribution in melanoma nodules.
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Affiliation(s)
- Liza Filali
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
| | - Marie-Pierre Puissegur
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
| | - Kevin Cortacero
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
| | - Sylvain Cussat-Blanc
- Institut de Recherche en Informatique de Toulouse (IRIT) - University Toulouse Capitole Centre national de la recherche scientifique (CNRS) UMR5505, Artificial and Natural Intelligence Toulouse Institute, Toulouse, France
| | - Roxana Khazen
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
| | - Nathalie Van Acker
- Department of Pathology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
| | - François-Xavier Frenois
- Department of Pathology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
| | - Arnaud Abreu
- Department of Pathology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
| | - Laurence Lamant
- Department of Pathology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
| | - Nicolas Meyer
- Department of Dermatology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
| | - Béatrice Vergier
- Service de Pathologie, CHU de Bordeaux, Bordeaux, France
- Equipe INSERM U1053-UMR BaRITOn (Eq 3), Université de Bordeaux, Bordeaux, France
| | - Sabina Müller
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
| | - Brienne McKenzie
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
- Corresponding author. (S.V.); (B.M.)
| | - Salvatore Valitutti
- INSERM U1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Université de Toulouse III-Paul Sabatier, 31057 Toulouse, France
- Department of Pathology, Institut Universitaire du Cancer-Oncopole de Toulouse, 31059 Toulouse, France
- Corresponding author. (S.V.); (B.M.)
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6
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Abstract
T cells initiate and regulate adaptive immune responses that can clear infections. To do this, they use their T cell receptors (TCRs) to continually scan the surfaces of other cells for cognate peptide antigens presented on major histocompatibility complexes (pMHCs). Experimental work has established that as few 1-10 pMHCs are sufficient to activate T cells. This sensitivity is remarkable in light of a number of factors, including the observation that the TCR and pMHC are short molecules relative to highly abundant long surface molecules, such as CD45, that can hinder initial binding, and moreover, the TCR/pMHC interaction is of weak affinity with solution lifetimes of approximately 1 second. Here, we review experimental and mathematical work that has contributed to uncovering molecular mechanisms of T cell sensitivity. We organize the mechanisms by where they act in the pathway to activate T cells, namely mechanisms that (a) promote TCR/pMHC binding, (b) induce rapid TCR signaling, and (c) amplify TCR signaling. We discuss work showing that high sensitivity reduces antigen specificity unless molecular feedbacks are invoked. We conclude by summarizing a number of open questions.
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Affiliation(s)
| | - Omer Dushek
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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7
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WEDAGEDERA JANAKR, BURROUGHS NJ. COMPARISON OF A DUAL STRATEGY FOR T-CELL ACTIVATION UNDER INHIBITION OF THE CD4 RECEPTOR. J BIOL SYST 2018. [DOI: 10.1142/s0218339018500158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We consider a stochastic model for T-cell activation proposed in Refs. [1] and [2] to compare the specificity and sensitivity of two different strategies for T-cell activation that utilize the history of phosphorylation of T-cell receptor (TCR). We compare these two strategies when the temporal signals/events that are essential for progressive T-cell activation are suppressed by blockade of CD4 receptor that may have caused by disease or therapeutic effects.3–6 We show that under these conditions, a threshold-strategy which is capable of maintaining a threshold (for total number of phosphorylated TCRs by time [Formula: see text]) for a further duration [Formula: see text] performs better in discriminating agonist peptides than a single-threshold strategy (reached by time [Formula: see text]) leading to T-cell activation using the Wentzell-Friedlin theory for large deviations for stochastic processes.7,8
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Affiliation(s)
- JANAK R. WEDAGEDERA
- Certara UK Limited, Simcyp Division, Level 2-Acero, 1 Concourse Way, Sheffield S1 2BJ, United Kingdom
| | - N. J. BURROUGHS
- Mathematics Institute and Warwick Systems, Biology Centre, University of Warwick, Coventry CV4 7AL, United Kingdom
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8
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Ali Q, Mustafa IH, Elkamel A, Touboul E, Gruy F, Lambert C. Mathematical modelling of T-cells activation dynamics for CD3 molecules recycling process. CAN J CHEM ENG 2016. [DOI: 10.1002/cjce.22607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Qasim Ali
- Department of Applied Mathematics; University of Western Ontario; London ON Canada
| | - Ibrahim H. Mustafa
- Biomedical Engineering Department; Helwan University; Cairo Egypt
- Department of Chemical Engineering; University of Waterloo; Waterloo ON Canada
| | - Ali Elkamel
- Department of Chemical Engineering; University of Waterloo; Waterloo ON Canada
| | - Eric Touboul
- Henry Fayol Institute; ENSM - Saint Étienne France
| | - Frederic Gruy
- Center for Biomedical and Healthcare Engineering; ENSM - Saint Étienne France
| | - Claude Lambert
- CHU - Saint Etienne, Immunology Lab; University Hospital; F 42055, Saint-Étienne France
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9
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Kajita MK, Yokota R, Aihara K, Kobayashi TJ. Experimental and theoretical bases for mechanisms of antigen discrimination by T cells. Biophysics (Nagoya-shi) 2015; 11:85-92. [PMID: 27493520 PMCID: PMC4736787 DOI: 10.2142/biophysics.11.85] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 02/01/2015] [Indexed: 12/01/2022] Open
Abstract
Interaction only within specific molecules is a requisite for accurate operations of a biochemical reaction in a cell where bulk of background molecules exist. While structural specificity is a well-established mechanism for specific interaction, biophysical and biochemical experiments indicate that the mechanism is not sufficient for accounting for the antigen discrimination by T cells. In addition, the antigen discrimination by T cells also accompanies three intriguing properties other than the specificity: sensitivity, speed, and concentration compensation. In this work, we review experimental and theoretical works on the antigen discrimination by focusing on these four properties and show future directions towards understanding of the fundamental principle for molecular discrimination.
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Affiliation(s)
- Masashi K Kajita
- Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan
| | - Ryo Yokota
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan
| | - Kazuyuki Aihara
- Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan; Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan
| | - Tetsuya J Kobayashi
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan
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10
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Asymptotic Analysis of First Passage Time Problems Inspired by Ecology. Bull Math Biol 2014; 77:83-125. [DOI: 10.1007/s11538-014-0053-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 12/08/2014] [Indexed: 01/31/2023]
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11
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12
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Abstract
Leukocytes play a critical role in recognizing and responding to infection and cancer. Central to this function is an array of cell-surface receptors that lack sequence homology. Many of these receptors have in common the fact that their signaling involves phosphorylation of cytoplasmic domains by extrinsic tyrosine kinases. These non-catalytic tyrosine-phosphorylated receptors (NTRs) share a number of other features, including small size and optimal stimulation by surface-associated ligands. We argue here that NTRs are also likely to share the same kinetic-segregation triggering mechanism, which involves segregation of the engaged NTR from receptor tyrosine phosphatases with large ectodomains such as CD45 and CD148. NTRs signal through tyrosine-containing cytoplasmic motifs, which recruit distinct cytoplasmic signaling proteins when phosphorylated, transducing activatory or inhibitory signals. They have two features that make them uniquely well suited to their role in immune recognition of infection and cancer. Their modular structure enables the coupling of many rapidly evolving receptors with diverse ligand specificities to the same conserved signaling machinery. Their similarity in size and shared signaling machinery enables them to colocalize at cell-cell interfaces when they engage ligands, facilitating the integration of activatory and inhibitory signals from multiple receptors at the cell surface.
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Affiliation(s)
- Omer Dushek
- Sir William Dunn School of Pathology, University of Oxford, UK
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13
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Chung W, Abel SM, Chakraborty AK. Protein clusters on the T cell surface may suppress spurious early signaling events. PLoS One 2012; 7:e44444. [PMID: 22973450 PMCID: PMC3433417 DOI: 10.1371/journal.pone.0044444] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 08/06/2012] [Indexed: 12/16/2022] Open
Abstract
T cells play an important role in the adaptive immune system, quickly activating effector functions in response to small numbers of antigenic peptides but rarely activating in response to constant interaction with most endogenous peptides. Emerging experimental evidence suggests that key membrane-bound signaling proteins such as the T cell receptor and the adaptor protein Lat are spatially organized into small clusters on the T cell membrane. We use spatially resolved, stochastic computer simulations to study how the inhomogeneous distribution of molecules affects the portion of the T cell signaling network in which the kinase ZAP-70, originating in T cell receptor clusters, phosphorylates Lat. To gain insight into the effects of protein clustering, we compare the signaling response from membranes with clustered proteins to the signaling response from membranes with homogeneously distributed proteins. Given a fixed amount of ZAP-70 (a proxy for degree of TCR stimulation) that must diffuse into contact with Lat molecules, the spatially homogeneous system responds faster and results in higher levels of phosphorylated Lat. Analysis of the spatial distribution of proteins demonstrates that, in the homogeneous system, nearest ZAP-70 and Lat proteins are closer on average and fewer Lat molecules share the same closest ZAP-70 molecule, leading to the faster response time. The results presented here suggest that spatial clustering of proteins on the T cell membrane may suppress the propagation of signal from ZAP-70 to Lat, thus providing a regulatory mechanism by which T cells suppress transient, spurious signals induced by stimulation of T cell receptors by endogenous peptides. Because this suppression of spurious signals may occur at a cost to sensitivity, we discuss recent experimental results suggesting other potential mechanisms by which ZAP-70 and Lat may interact to initiate T cell activation.
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Affiliation(s)
- Woo Chung
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Steven M. Abel
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Arup K. Chakraborty
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Ragon Institute of MGH, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Harvard, Charlestown, Massachusetts, United States of America
- * E-mail:
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14
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Currie J, Castro M, Lythe G, Palmer E, Molina-París C. A stochastic T cell response criterion. J R Soc Interface 2012; 9:2856-70. [PMID: 22745227 PMCID: PMC3479899 DOI: 10.1098/rsif.2012.0205] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The adaptive immune system relies on different cell types to provide fast and coordinated responses, characterized by recognition of pathogenic challenge, extensive cellular proliferation and differentiation, as well as death. T cells are a subset of the adaptive immune cellular pool that recognize immunogenic peptides expressed on the surface of antigen-presenting cells by means of specialized receptors on their membrane. T cell receptor binding to ligand determines T cell responses at different times and locations during the life of a T cell. Current experimental evidence provides support to the following: (i) sufficiently long receptor–ligand engagements are required to initiate the T cell signalling cascade that results in productive signal transduction and (ii) counting devices are at work in T cells to allow signal accumulation, decoding and translation into biological responses. In the light of these results, we explore, with mathematical models, the timescales associated with T cell responses. We consider two different criteria: a stochastic one (the mean time it takes to have had N receptor–ligand complexes bound for at least a dwell time, τ, each) and one based on equilibrium (the time to reach a threshold number N of receptor–ligand complexes). We have applied mathematical models to previous experiments in the context of thymic negative selection and to recent two-dimensional experiments. Our results indicate that the stochastic criterion provides support to the thymic affinity threshold hypothesis, whereas the equilibrium one does not, and agrees with the ligand hierarchy experimentally established for thymic negative selection.
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Affiliation(s)
- James Currie
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds LS2 9JT, UK
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15
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Martin GV, Yun Y, Conforti L. Modulation of T cell activation by localized K⁺ accumulation at the immunological synapse--a mathematical model. J Theor Biol 2012; 300:173-82. [PMID: 22285786 DOI: 10.1016/j.jtbi.2012.01.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 12/21/2011] [Accepted: 01/11/2012] [Indexed: 01/06/2023]
Abstract
The response of T cells to antigens (T cell activation) is marked by an increase in intracellular Ca²⁺ levels. Voltage-gated and Ca²⁺-dependent K⁺ channels control the membrane potential of human T cells and regulate Ca²⁺ influx. This regulation is dependent on proper accumulation of K⁺ channels at the immunological synapse (IS) a signaling zone that forms between a T cell and antigen presenting cell. It is believed that the IS provides a site for regulation of the activation response and that K⁺ channel inhibition occurs at the IS, but the underlying mechanisms are unknown. A mathematical model was developed to test whether K⁺ efflux through K⁺ channels leads to an accumulation of K⁺ in the IS cleft, ultimately reducing K⁺ channel function and intracellular Ca²⁺ concentration ([Ca²⁺](i)). Simulations were conducted in models of resting and activated T cell subsets, which express different levels of K⁺ channels, by varying the K⁺ diffusion constant and the spatial localization of K⁺ channels at the IS. K⁺ accumulation in the IS cleft was calculated to increase K⁺ concentration ([K⁺]) from its normal value of 5.0 mM to 5.2-10.0 mM. Including K⁺ accumulation in the model of the IS reduced calculated K⁺ current by 1-12% and consequently, reduced calculated [Ca²⁺](i) by 1-28%. Significant reductions in K⁺ current and [Ca²⁺](i) only occurred in activated T cell simulations when most K⁺ channels were centrally clustered at the IS. The results presented show that the localization of K⁺ channels at the IS can produce a rise in [K⁺] in the IS cleft and lead to a substantial decrease in K⁺ currents and [Ca²⁺](i) in activated T cells thus providing a feedback inhibitory mechanism during T cell activation.
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Affiliation(s)
- Geoffrey V Martin
- Department of Internal Medicine, 231 A. Sabin Way, Division of Nephrology, University of Cincinnati, Cincinnati, OH 45267-0585, USA
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16
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Choudhuri K, Dustin ML. Signaling microdomains in T cells. FEBS Lett 2010; 584:4823-31. [PMID: 20965175 DOI: 10.1016/j.febslet.2010.10.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 10/12/2010] [Accepted: 10/13/2010] [Indexed: 01/22/2023]
Abstract
Sub-micron scale signaling domains induced in the plasma membrane of cells are thought to play important roles in signal transduction. In T cells, agonist MHC-peptide complexes induce small diffraction-limited domains enriched in T cell receptor (TCR) and signaling molecules. These microclusters serve as transient platforms for signal initiation and are required for sustained signaling in T cells, although each microcluster functions for only a couple of minutes. How they are formed, and what mechanisms promote and regulate signaling within TCR microclusters is largely unknown, although it is clear that TCR engagement and dynamic reorganization of cortical actin are involved. Here, we review current understanding of signaling within microclusters in T cells, and speculate on how these structures may form, initiate biochemical signals, and serve as sites of both signal integration and amplification, while also facilitating appropriate termination of TCR and related signaling.
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Affiliation(s)
- Kaushik Choudhuri
- Helen L and Martin S Kimmel Center for Biology and Medicine of the Skirball Institute of Biomolecular Medicine, New York, NY 10016, USA
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17
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Govern CC, Paczosa MK, Chakraborty AK, Huseby ES. Fast on-rates allow short dwell time ligands to activate T cells. Proc Natl Acad Sci U S A 2010; 107:8724-9. [PMID: 20421471 PMCID: PMC2889346 DOI: 10.1073/pnas.1000966107] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two contrasting theories have emerged that attempt to describe T-cell ligand potency, one based on the t(1/2) of the interaction and the other based on the equilibrium affinity (K(D)). Here, we have identified and studied an extensive set of T-cell receptor (TCR)-peptide-MHC (pMHC) interactions for CD4(+) cells that have differential K(D)s and kinetics of binding. Our data indicate that ligands with a short t(1/2) can be highly stimulatory if they have fast on-rates. Simple models suggest these fast kinetic ligands are stimulatory because the pMHCs bind and rebind the same TCR several times. Rebinding occurs when the TCR-pMHC on-rate outcompetes TCR-pMHC diffusion within the cell membrane, creating an aggregate t(1/2) (t(a)) that can be significantly longer than a single TCR-pMHC encounter. Accounting for t(a), ligand potency is K(D)-based when ligands have fast on-rates (k(on)) and t(1/2)-dependent when they have slow k(on). Thus, TCR-pMHC k(on) allow high-affinity short t(1/2) ligands to follow a kinetic proofreading model.
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Affiliation(s)
| | - Michelle K. Paczosa
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01655; and
| | - Arup K. Chakraborty
- Departments of Chemical Engineering
- Chemistry, and
- Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
- Ragon Institute, Charlestown, MA 02129
| | - Eric S. Huseby
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01655; and
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18
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Aleksic M, Dushek O, Zhang H, Shenderov E, Chen JL, Cerundolo V, Coombs D, van der Merwe PA. Dependence of T cell antigen recognition on T cell receptor-peptide MHC confinement time. Immunity 2010; 32:163-74. [PMID: 20137987 PMCID: PMC2862301 DOI: 10.1016/j.immuni.2009.11.013] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 10/02/2009] [Accepted: 11/20/2009] [Indexed: 12/18/2022]
Abstract
T cell receptor (TCR) binding to diverse peptide-major histocompatibility complex (pMHC) ligands results in various degrees of T cell activation. Here we analyze which binding properties of the TCR-pMHC interaction are responsible for this variation in pMHC activation potency. We have analyzed activation of the 1G4 cytotoxic T lymphocyte clone by cognate pMHC variants and performed thorough correlation analysis of T cell activation with 1G4 TCR-pMHC binding properties measured in solution. We found that both the on rate (kon) and off rate (koff) contribute to activation potency. Based on our results, we propose a model in which rapid TCR rebinding to the same pMHC after chemical dissociation increases the effective half-life or “confinement time” of a TCR-pMHC interaction. This confinement time model clarifies the role of kon in T cell activation and reconciles apparently contradictory reports on the role of TCR-pMHC binding kinetics and affinity in T cell activation.
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Affiliation(s)
- Milos Aleksic
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
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19
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Chakraborty AK, Das J. Pairing computation with experimentation: a powerful coupling for understanding T cell signalling. Nat Rev Immunol 2010; 10:59-71. [DOI: 10.1038/nri2688] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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20
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Dushek O, Das R, Coombs D. A role for rebinding in rapid and reliable T cell responses to antigen. PLoS Comput Biol 2009; 5:e1000578. [PMID: 19956745 PMCID: PMC2775163 DOI: 10.1371/journal.pcbi.1000578] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Accepted: 10/23/2009] [Indexed: 01/13/2023] Open
Abstract
Experimental work has shown that T cells of the immune system rapidly and specifically respond to antigenic molecules presented on the surface of antigen-presenting-cells and are able to discriminate between potential stimuli based on the kinetic parameters of the T cell receptor-antigen bond. These antigenic molecules are presented among thousands of chemically similar endogenous peptides, raising the question of how T cells can reliably make a decision to respond to certain antigens but not others within minutes of encountering an antigen presenting cell. In this theoretical study, we investigate the role of localized rebinding between a T cell receptor and an antigen. We show that by allowing the signaling state of individual receptors to persist during brief unbinding events, T cells are able to discriminate antigens based on both their unbinding and rebinding rates. We demonstrate that T cell receptor coreceptors, but not receptor clustering, are important in promoting localized rebinding, and show that requiring rebinding for productive signaling reduces signals from a high concentration of endogenous pMHC. In developing our main results, we use a relatively simple model based on kinetic proofreading. However, we additionally show that all our results are recapitulated when we use a detailed T cell receptor signaling model. We discuss our results in the context of existing models and recent experimental work and propose new experiments to test our findings.
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Affiliation(s)
- Omer Dushek
- Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
- Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
| | - Raibatak Das
- Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Daniel Coombs
- Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
- Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, Canada
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21
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McKenzie HW, Lewis MA, Merrill EH. First passage time analysis of animal movement and insights into the functional response. Bull Math Biol 2008; 71:107-29. [PMID: 18825463 DOI: 10.1007/s11538-008-9354-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 08/28/2008] [Indexed: 11/28/2022]
Abstract
Movement plays a role in structuring the interactions between individuals, their environment, and other species. Although movement models coupled with empirical data are widely used to study animal distribution, they have seldom been used to study search time. This paper proposes first passage time as a novel approach for understanding the effect of the landscape on animal movement and search time. In the context of animal movement, first passage time is the time taken for an animal to reach a specified site for the first time. We synthesize current first passage time theory and derive a general first passage time equation for animal movement. This equation is related to the Fokker-Planck equation, which is used to describe the distribution of animals in the landscape. We illustrate the first passage time method by analyzing the effect of territorial behavior on the time required for a red fox to locate prey throughout its home range. Using first passage time to compute search times, we consider the effect of two different searching modes on a functional response. We show that random searching leads to a Holling type III functional response. First passage time analysis provides a new tool for studying how animal movement may influence ecological processes.
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Affiliation(s)
- Hannah W McKenzie
- Centre for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada.
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