T cell activation requires force generation

Hu, Kenneth H.; Butte, Manish J.

doi:10.1084/jem.2137oia56

Cited by 15 publications

(30 citation statements)

References 17 publications

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“…This paradoxical extension of αβ TCR-pMHC-bond lifetime under force, so-called catch bond behavior, was then observed experimentally (19,33). The importance of force on TCR triggering has been confirmed in other work (34)(35)(36)(37)(38)(39)(40). However, during the initial T-cell surface contact, external (scanning) and internal (retrograde flow) force appear to operate in opposing directions (41).…”

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confidence: 68%

Mechanosensing drives acuity of αβ T-cell recognition

Feng

Brazin

Kobayashi

et al. 2017

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

151

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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confidence: 68%

Mechanosensing drives acuity of αβ T-cell recognition

Feng

Brazin

Kobayashi

et al. 2017

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

151

197

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“…In the context of immune synapse formation, traction stresses generated by T cells enable antigen discrimination and cell activation (11), likely through the enhancement of interaction lifetime upon application of forces to the TCR (54). Previous work, including ours, has characterized these forces and shown that they are dependent on pMHC affinity (11), actin dynamics (9), TCR signaling and calcium influx (8,55), cdc42 activity (11), and stiffness of the opposing substrate (9,10,56). Here, we integrate force measurements with dual-color TIRF imaging to propose a model of force generation in T cells: Dynamic MTs locally modulate NMII filament assembly; lamellipodial actin flow; and, thereby, force generation through the Rho GTPase pathway (Fig.…”

Section: Discussionmentioning

confidence: 97%

Dynamic microtubules regulate cellular contractility during T-cell activation

Hui

Upadhyaya

2017

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

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T-cell receptor (TCR) triggering and subsequent T-cell activation are essential for the adaptive immune response. Recently, multiple lines of evidence have shown that force transduction across the TCR complex is involved during TCR triggering, and that the T cell might use its force-generation machinery to probe the mechanical properties of the opposing antigen-presenting cell, giving rise to different signaling and physiological responses. Mechanistically, actin polymerization and turnover have been shown to be essential for force generation by T cells, but how these actin dynamics are regulated spatiotemporally remains poorly understood. Here, we report that traction forces generated by T cells are regulated by dynamic microtubules (MTs) at the interface. These MTs suppress Rho activation, nonmuscle myosin II bipolar filament assembly, and actin retrograde flow at the T-cell-substrate interface. Our results suggest a novel role of the MT cytoskeleton in regulating force generation during T-cell activation.T lymphocytes, central players in the adaptive immune response, are activated when T-cell receptors (TCRs) on their surface recognize cognate peptide-major histocompatibility complex (pMHC) expressed on the surface of antigen-presenting cells (APCs). A burst of actin polymerization is triggered upon TCR stimulation (1), leading to an enhancement of the cell/APC contact area as the T cell spreads over the surface of the APC (2) and the formation of a macromolecular protein assembly known as the immunological synapse (IS) (3, 4). Accompanying IS formation, T cells also undergo a rapid polarization of the microtubule (MT) cytoskeleton, within 1-2 min after initial contact, that facilitates directional secretion of cytokines and cytolytic factors toward the APC (5-7). Therefore, the contact zone between T cells and APCs is a site at which the MT and actin cytoskeletons could potentially interact to regulate signaling.Recent studies have established that T cells generate significant traction stresses at the cell-cell interface, albeit relatively weak compared with adherent cells (8-11). These forces, which peak 5-10 min after stimulation, facilitate T-cell activation, in part, by inducing conformational changes in the TCR-CD3 complex (12-15). Although actin polymerization/depolymerization dynamics are essential for T cells to maintain dynamic traction stresses and to drive calcium influx and integrin affinity maturation (9, 16, 17), the regulatory pathways that control these cytoskeletal forces are not completely understood. In particular, whether and how the polarized MT cytoskeleton interacts with the actin cytoskeleton and regulates force generation at the T-cell-APC contact remain open questions.MTs in the cell exist in two populations: dynamic/tyrosinated MTs and stable MTs that have undergone posttranslational modifications, including detyrosination and acetylation (18). Previous studies of T-cell activation have elucidated that microtubuleorganizing center (MTOC) translocation is associated with the formati...

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“…A nonlinear response of the ␣␤TCR-pMHC bond was recently shown in biomembrane force probe and optical trap assays where single molecule interactions are probed (21,22). As a consequence of these and additional studies, the role of force in TCR-based signaling is becoming more readily appreciated (21)(22)(23)(24).…”

Section: And References Therein)mentioning

confidence: 93%

Pre-T Cell Receptors (Pre-TCRs) Leverage Vβ Complementarity Determining Regions (CDRs) and Hydrophobic Patch in Mechanosensing Thymic Self-ligands

Das

Mallis

Duke‐Cohan

et al. 2016

Journal of Biological Chemistry

104

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Edited by Peter CresswellThe pre-T cell receptor (pre-TCR) is a pT␣-␤ heterodimer functioning in early ␣␤ T cell development. Although once thought to be ligand-autonomous, recent studies show that preTCRs participate in thymic repertoire formation through recognition of peptides bound to major histocompatibility molecules (pMHC). Using optical tweezers, we probe pre-TCR bonding with pMHC at the single molecule level. Like the ␣␤TCR, the pre-TCR is a mechanosensor undergoing force-based structural transitions that dynamically enhance bond lifetimes and exploiting allosteric control regulated via the C␤ FG loop region. The pre-TCR structural transitions exhibit greater reversibility than TCR␣␤ and ordered force-bond lifetime curves. Higher piconewton force requires binding through both complementarity determining region loops and hydrophobic V␤ patch apposition. This patch functions in the pre-TCR as a surrogate V␣ domain, fostering ligand promiscuity to favor development of ␤ chains with self-reactivity but is occluded by ␣ subunit replacement of pT␣ upon ␣␤TCR formation. At the double negative 3 thymocyte stage where the pre-TCR is first expressed, pre-TCR interaction with self-pMHC ligands imparts growth and survival advantages as revealed in thymic stromal cultures, imprinting fundamental self-reactivity in the T cell repertoire. Collectively, our data imply the existence of sequential mechanosensor ␣␤TCR repertoire tuning via the pre-TCR.The mammalian adaptive immune system protects its host against infectious diseases as well as tumors in a highly specific manner. At the core of ␣␤ T lymphocyte recognition is self-versus non-self-discrimination, a functionality endowed by clonal cell-surface T cell receptors (TCRs) 4 (1-3). In the mammalian thymus, the millions of distinct TCRs expressed create a repertoire that is refined to eliminate unwanted autoreactive specificities prior to export into the peripheral lymphoid compartment (Ref. 4 and references therein).The earliest thymocytes, termed double negative (DN1-4), lack both CD4 and CD8 and expression of ␣␤TCR complexes (hereafter termed ␣␤TCRs) (5). Within the DN3 stage, a pre-TCR complex is generated comprised of a variable TCR␤ chain disulfide-linked to the invariant pT␣ subunit. In turn, the pT␣-␤ heterodimer is noncovalently complexed with the same CD3 dimers as found in the ␣␤TCR, namely CD3⑀␥, CD3⑀␦, and CD3 (1, 2). This pre-TCR complex triggers cellular survival and expansion and, importantly, induces expression of CD4 and CD8 co-receptors so that the thymocytes transit to the DP (CD4 ϩ CD8 ϩ ) thymocyte stage where rearrangement of the TCR␣ gene occurs. Only at the DP stage is the ␣␤TCR expressed. The pre-TCR signaling process, termed ␤ selection, also controls allelic exclusion of the TCR␤ locus in a given cell (6). Pre-TCR signaling components include tyrosine kinases Lck, Fyn, with Notch-1, Notch-1 ligand DL4, interleukin 7, and CXCR4 supporting pre-TCR function (5, 10). Although ␣␤TCR DP thymocyte selection processes involve pMHC-dependent posit...

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T cell activation requires force generation

Cited by 15 publications

References 17 publications

Mechanosensing drives acuity of αβ T-cell recognition

Mechanosensing drives acuity of αβ T-cell recognition

Dynamic microtubules regulate cellular contractility during T-cell activation

Pre-T Cell Receptors (Pre-TCRs) Leverage Vβ Complementarity Determining Regions (CDRs) and Hydrophobic Patch in Mechanosensing Thymic Self-ligands

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