Constitutively Oxidized CXXC Motifs within the CD3 Heterodimeric Ectodomains of the T Cell Receptor Complex Enforce the Conformation of Juxtaposed Segments

Brazin, Kristine N.; Mallis, Robert J.; Li, Chen; Keskin, Derin B.; Arthanari, Haribabu; Gao, Yuanwei; Wu, Shiaw‐Lin; Karger, Barry L.; Wagner, Gerhard; Reinherz, Ellis L.

doi:10.1074/jbc.m114.574996

Cited by 27 publications

(24 citation statements)

References 56 publications

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“…1 D-F and 3C). The TCR and CD3 ECD-TM domain "connecting peptides" are highly conserved and affect TCR-CD3 function when altered (32)(33)(34)(35)(36)(37). Given the longer length of the TCR connecting peptides relative to the CD3 connecting peptides, there is sufficient space for the TCR to be placed over the CD3 ECDs, consistent with what was observed for our pMHC-TCR-CD3 complexes (Fig.…”

Section: Discussionsupporting

confidence: 76%

“…Our data provide a structural framework that can potentially begin to reconcile disparate observations about how the TCR relays a ligation event to signaling. Such observations include studies showing that monomeric pMHC possesses little to no ability to induce signaling regardless of affinity (49), there exist signaling-permissive and -nonpermissive pMHC-TCR docking geometries (48), conformational changes occur in the TCR upon pMHC ligation (46,(50)(51)(52), the CD4 and CD8 coreceptors are required to place Lck relative to the CD3 ITAMs (53, 54), phosphatases are occluded from the T-cell Ag-presenting cell synapse (18,26,55), and mechanotransduction appears to be important for TCR signaling (19,36,(56)(57)(58)(59) (Fig. 4).…”

Section: Discussionmentioning

confidence: 99%

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Molecular architecture of the αβ T cell receptor–CD3 complex

Birnbaum

Berry

Hsiao

et al. 2014

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

109

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αβ T-cell receptor (TCR) activation plays a crucial role for T-cell function. However, the TCR itself does not possess signaling domains. Instead, the TCR is noncovalently coupled to a conserved multisubunit signaling apparatus, the CD3 complex, that comprises the CD3eγ, CD3eδ, and CD3ζζ dimers. How antigen ligation by the TCR triggers CD3 activation and what structural role the CD3 extracellular domains (ECDs) play in the assembled TCR-CD3 complex remain unclear. Here, we use two complementary structural approaches to gain insight into the overall organization of the TCR-CD3 complex. Small-angle X-ray scattering of the soluble TCR-CD3eδ complex reveals the CD3eδ ECDs to sit underneath the TCR α-chain. The observed arrangement is consistent with EM images of the entire TCR-CD3 integral membrane complex, in which the CD3eδ and CD3eγ subunits were situated underneath the TCR α-chain and TCR β-chain, respectively. Interestingly, the TCR-CD3 transmembrane complex bound to peptide-MHC is a dimer in which two TCRs project outward from a central core composed of the CD3 ECDs and the TCR and CD3 transmembrane domains. This arrangement suggests a potential ligand-dependent dimerization mechanism for TCR signaling. Collectively, our data advance our understanding of the molecular organization of the TCR-CD3 complex, and provides a conceptual framework for the TCR activation mechanism.T-cell receptor | electron microscopy | small-angle X-ray scattering T cells are key mediators of the adaptive immune response.Each αβ T cell contains a unique αβ T-cell receptor (TCR), which binds antigens (Ags) displayed by major histocompatibility complexes (MHCs) and MHC-like molecules (1). The TCR serves as a remarkably sensitive driver of cellular function: although TCR ligands typically bind quite weakly (1-200 μM), even a handful of TCR ligands are sufficient to fully activate a T cell (2, 3). The TCR does not possess intracellular signaling domains, uncoupling Ag recognition from T-cell signaling. The TCR is instead noncovalently associated with a multisubunit signaling apparatus, consisting of the CD3eγ and CD3eδ heterodimers and the CD3ζζ homodimer, which collectively form the TCR-CD3 complex (4, 5). The CD3γ/δ/e subunits each consist of a single extracellular Ig domain and a single immunoreceptor tyrosine-based activation motif (ITAM), whereas CD3ζ has a short extracellular domain (ECD) and three ITAMs (6-11). The TCR-CD3 complex exists in 1:1:1:1 stoichiometry for the αβTCR: CD3eγ:CD3eδ:CD3ζζ dimers (12). Phosphorylation of the intracellular CD3 ITAMs and recruitment of the adaptor Nck lead to T-cell activation, proliferation, and survival (13,14). Understanding the underlying principles of TCR-CD3 architecture and T-cell signaling is of therapeutic interest. For example, TCR-CD3 is the target of therapeutic antibodies such as the immunosuppressant OKT3 (15), and there is increasing interest in manipulating T cells in an Ag-dependent manner by using naturally occurring and engineered TCRs (16).Assembly of the TCR-CD3 complex is p...

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Molecular architecture of the αβ T cell receptor–CD3 complex

Birnbaum

Berry

Hsiao

et al. 2014

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

109

View full text Add to dashboard Cite

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“…As a consequence, CD3 would be situated between the TCR and T cell membrane, which is consistent with the greater length of the TCR ␣ and ␤ chain stalk regions (21 and 16 residues, respectively) than those of CD3⑀␥ and CD3⑀␦ (each ϳ9 residues). Mutational studies have demonstrated the importance of these highly conserved stalks for the assembly and function of the TCR-CD3 complex (41)(42)(43)(44)(45). Extension of our NMR analysis to the MS2-3C8 ␣ chain will define the docking site for CD3 ECDs on the TCR more completely.…”

Section: Discussionmentioning

confidence: 99%

Identification of the Docking Site for CD3 on the T Cell Receptor β Chain by Solution NMR

Rangarajan

Kerzic

et al. 2015

Journal of Biological Chemistry

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“…Ligation impacts disposition and function of the associated CD3 dimers (CD3 γ, CD3 δ, and CD3ζζ) as well as the transmembrane domains of the TCR heterodimer and CD3 subunits that interdigitate in the membrane to signal into the cytoplasm (8,9). A cascade of intracellular events involving phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) on the CD3 cytoplasmic domains with subsequent ZAP70 activation and downstream signaling follows (10,11).…”

mentioning

confidence: 99%

Mechanosensing drives acuity of αβ T-cell recognition

Feng

Brazin

Kobayashi

et al. 2017

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

Self Cite

156

197

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T lymphocytes use surface αβ T-cell receptors (TCRs) to recognize peptides bound to MHC molecules (pMHCs) on antigen-presenting cells (APCs). How the exquisite specificity of high-avidity T cells is achieved is unknown but essential, given the paucity of foreign pMHC ligands relative to the ubiquitous self-pMHC array on an APC. Using optical traps, we determine physicochemical triggering thresholds based on load and force direction. Strikingly, chemical thresholds in the absence of external load require orders of magnitude higher pMHC numbers than observed physiologically. In contrast, force applied in the shear direction (∼10 pN per TCR molecule) triggers T-cell Ca 2+ flux with as few as two pMHC molecules at the interacting surface interface with rapid positional relaxation associated with similarly directed motor-dependent transport via ∼8-nm steps, behaviors inconsistent with serial engagement during initial TCR triggering. These synergistic directional forces generated during cell motility are essential for adaptive T-cell immunity against infectious pathogens and cancers.mechanosensor | T-cell receptor | T-cell activation | optical tweezers | cellular force relaxation T he T-cell receptor (TCR) expressed on T lymphocytes of the adaptive immune system is a stout and squat (12-nm wide × 8-nm tall) multisubunit surface complex with a ligand binding moiety that is an αβ disulfide-linked heterodimer buttressed by the associated invariant CD3 subunits (1-3). The αβ chains are each encoded by V and J gene segments and in the case of the β, a D segment as well (4). The clone-specific TCR unique to each T lymphocyte endows mammals with the capacity to detect perturbations in host cellular function resulting from myriad infectious pathogens, physical damage (thermal, irradiation, etc.), or premalignant or malignant cellular transformations while averting strong self-reactivities that could induce autoimmunity (5).Signaling is initiated through ligation of the clonotype by its cognate antigenic peptide bound to an MHC molecule (pMHC) and displayed on the surface of antigen-presenting cells (APCs) (6, 7). Ligation impacts disposition and function of the associated CD3 dimers (CD3 γ, CD3 δ, and CD3ζζ) as well as the transmembrane domains of the TCR heterodimer and CD3 subunits that interdigitate in the membrane to signal into the cytoplasm (8, 9). A cascade of intracellular events involving phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) on the CD3 cytoplasmic domains with subsequent ZAP70 activation and downstream signaling follows (10, 11). Membrane-associated CD8 and CD4 coreceptors, marking cytotoxic T lymphocytes (CTLs) and helper T cells, respectively, function to bring the membrane-anchored Src family tyrosine kinase Lck to the TCR-pMHC complex for the initiation of ITAM phosphorylation. Signaling, in turn, leads to a transient rise of cytosolic Ca 2+ and other biochemical events resulting in transcriptional activation, ultimately resulting in developmental decisions or effector functi...

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Constitutively Oxidized CXXC Motifs within the CD3 Heterodimeric Ectodomains of the T Cell Receptor Complex Enforce the Conformation of Juxtaposed Segments

Cited by 27 publications

References 56 publications

Molecular architecture of the αβ T cell receptor–CD3 complex

Molecular architecture of the αβ T cell receptor–CD3 complex

Identification of the Docking Site for CD3 on the T Cell Receptor β Chain by Solution NMR

Mechanosensing drives acuity of αβ T-cell recognition

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