Structure of the Chicken CD3ϵδ/γ Heterodimer and Its Assembly with the αβT Cell Receptor

Berry, Richard; Headey, Stephen J.; Call, Melissa; McCluskey, James; Tregaskes, Clive A.; Kaufman, Jim; Koh, Ruide; Scanlon, M.J.; Call, Matthew E.; Rossjohn, Jamie

doi:10.1074/jbc.m113.544965

Cited by 13 publications

(10 citation statements)

References 54 publications

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“…S2). This system has been shown to faithfully recapitulate the cotranslational folding and assembly of multisubunit receptors (19,22,(25)(26)(27)(28)(29), and the use of conformation-specific antibodies and specialized affinity tags allows isolation of receptor complexes of well-defined composition and stoichiometry with very high sensitivity and specificity (19,22). For this screen, in vitro-transcribed mRNAs encoding each TCRαβ combination were cotranslated with a master mix of CD3 and ζ mRNAs and allowed to fold and assemble before treatment with copper(II)-o-phenanthroline (CuPhe) to catalyze intramembrane disulfide bond formation.…”

Section: Resultsmentioning

confidence: 99%

A conserved αβ transmembrane interface forms the core of a compact T-cell receptor–CD3 structure within the membrane

Krshnan

Park

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The T-cell antigen receptor (TCR) is an assembly of eight type I single-pass membrane proteins that occupies a central position in adaptive immunity. Many TCR-triggering models invoke an alteration in receptor complex structure as the initiating event, but both the precise subunit organization and the pathway by which ligandinduced alterations are transferred to the cytoplasmic signaling domains are unknown. Here, we show that the receptor complex transmembrane (TM) domains form an intimately associated eighthelix bundle organized by a specific interhelical TCR TM interface. The salient features of this core structure are absolutely conserved between αβ and γδ TCR sequences and throughout vertebrate evolution, and mutations at key interface residues caused defects in the formation of stable TCRαβ:CD3δe:CD3γe:ζζ complexes. These findings demonstrate that the eight TCR-CD3 subunits form a compact and precisely organized structure within the membrane and provide a structural basis for further investigation of conformationally regulated models of transbilayer TCR signaling.T-cell receptor | transmembrane structure | NMR | MD simulation | cysteine cross-linking T he antigen-specific T-cell response depends critically upon the ability of the T-cell receptor (TCR) to signal the recognition of activating ligands. The variable TCR proteins (α, β, δ, and γ) that bind to these ligands have no intrinsic intracellular signaling capability and transmit information through the noncovalently associated CD3δe, CD3γe, and ζζ modules containing cytoplasmic immunoreceptor tyrosine-based activation motifs (ITAMs) that are phosphorylated by the Src-family kinase Lck. The mechanism by which antigen sensing is translated from ligand binding at the distal end of the TCR to phosphorylation events at the cytoplasmic tails of the associated signaling modules remains an important open question in T-cell biology. A mounting pool of evidence implicates ligand-induced alterations in receptor structure (1) and/or TCR-CD3 configuration (2-6) as the triggering event. Changes in the structured extracellular (EC) domains are proposed to translate, through an unknown mechanism, into alterations in the CD3 and ζζ cytoplasmic tails, converting them to a conformation that is receptive to phosphorylation by Lck and binding of other proximal signaling components (7-12). This type of signaling model implies a pathway between EC and cytoplasmic domains that may involve alterations in the subunit transmembrane (TM) domains with respect to each other and/ or the lipid bilayer (13-16). Consistent with this view, Kuhns and colleagues (17) recently reported a ligand-induced change in intersubunit proximity at the TM-juxtamembrane juncture in the ζζ dimer and proposed that this "mechanical switch" is coupled to signal initiation at the ζζ cytoplasmic tails. However, the nature of the upstream structural changes that trigger this switch, and whether it is required for signal initiation, remain to be determined. Tracing possible transbilayer conformational pathway...

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Section: Resultsmentioning

confidence: 99%

A conserved αβ transmembrane interface forms the core of a compact T-cell receptor–CD3 structure within the membrane

Krshnan

Park

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In addition to concealing flexibility, the X-ray structures available are also incomplete and lack the core components necessary for signal transduction (Figures 1B,C). While the structures of TCR-pMHC, pMHC-CD8 (26–29), CD3 heterodimers (30–34), and CD8 homo/heterodimers (35, 36) have been determined, critically informative complexes such as CD8 and/or CD3 in complex with TCR-pMHC or even just TCR-CD3 are lacking due to the poor affinity of soluble CD3 and CD8 for the TCR and MHC, respectively (33, 37, 38). Also absent, due to technical challenges, are the stalk regions, membrane-spanning domains, and intracellular tails of the TCR, MHC, and CD8 and CD3 molecules, which play a role in complex assembly, the spatial organization of the components and signal transmission (39–46).…”

Section: X-ray Crystallography: Pioneering Atomic Resolution Detailsmentioning

confidence: 99%

Integrating Experiment and Theory to Understand TCR-pMHC Dynamics

Buckle

Borg

2018

Front. Immunol.

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The conformational dynamism of proteins is well established. Rather than having a single structure, proteins are more accurately described as a conformational ensemble that exists across a rugged energy landscape, where different conformational sub-states interconvert. The interaction between αβ T cell receptors (TCR) and cognate peptide-MHC (pMHC) is no exception, and is a dynamic process that involves substantial conformational change. This review focuses on technological advances that have begun to establish the role of conformational dynamics and dynamic allostery in TCR recognition of the pMHC and the early stages of signaling. We discuss how the marriage of molecular dynamics (MD) simulations with experimental techniques provides us with new ways to dissect and interpret the process of TCR ligation. Notably, application of simulation techniques lags behind other fields, but is predicted to make substantial contributions. Finally, we highlight integrated approaches that are being used to shed light on some of the key outstanding questions in the early events leading to TCR signaling.

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“…The recent NMR structure of chicken CD3εp reveals a unique dimer interface with surface exposed, non-conserved residues clustered to a single face of the heterodimer ( 53 ). These, among other details, suggest that the orientation of the two CD3εp heterodimers in a given TCR complex in non-mammals is similar to that shown in Figure 1 for the mammalian counterparts.…”

Section: Vertebrate Evolution Of the αβTcr Complex: Conjoint Cd3 Molementioning

confidence: 99%

Structural Features of the αβTCR Mechanotransduction Apparatus That Promote pMHC Discrimination

et al. 2015

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The αβTCR was recently revealed to function as a mechanoreceptor. That is, it leverages mechanical energy generated during immune surveillance and at the immunological synapse to drive biochemical signaling following ligation by a specific foreign peptide–MHC complex (pMHC). Here, we review the structural features that optimize this transmembrane (TM) receptor for mechanotransduction. Specialized adaptations include (1) the CβFG loop region positioned between Vβ and Cβ domains that allosterically gates both dynamic T cell receptor (TCR)–pMHC bond formation and lifetime; (2) the rigid super β-sheet amalgams of heterodimeric CD3εγ and CD3εδ ectodomain components of the αβTCR complex; (3) the αβTCR subunit connecting peptides linking the extracellular and TM segments, particularly the oxidized CxxC motif in each CD3 heterodimeric subunit that facilitates force transfer through the TM segments and surrounding lipid, impacting cytoplasmic tail conformation; and (4) quaternary changes in the αβTCR complex that accompany pMHC ligation under load. How bioforces foster specific αβTCR-based pMHC discrimination and why dynamic bond formation is a primary basis for kinetic proofreading are discussed. We suggest that the details of the molecular rearrangements of individual αβTCR subunit components can be analyzed utilizing a combination of structural biology, single-molecule FRET, optical tweezers, and nanobiology, guided by insightful atomistic molecular dynamic studies. Finally, we review very recent data showing that the pre-TCR complex employs a similar mechanobiology to that of the αβTCR to interact with self-pMHC ligands, impacting early thymic repertoire selection prior to the CD4+CD8+ double positive thymocyte stage of development.

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Structure of the Chicken CD3ϵδ/γ Heterodimer and Its Assembly with the αβT Cell Receptor

Cited by 13 publications

References 54 publications

A conserved αβ transmembrane interface forms the core of a compact T-cell receptor–CD3 structure within the membrane

A conserved αβ transmembrane interface forms the core of a compact T-cell receptor–CD3 structure within the membrane

Integrating Experiment and Theory to Understand TCR-pMHC Dynamics

Structural Features of the αβTCR Mechanotransduction Apparatus That Promote pMHC Discrimination

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