scholarly journals An essential role for the MAL protein in targeting Lck to the plasma membrane of human T lymphocytes

2008 ◽  
Vol 205 (13) ◽  
pp. 3201-3213 ◽  
Author(s):  
Olga Antón ◽  
Alicia Batista ◽  
Jaime Millán ◽  
Laura Andrés-Delgado ◽  
Rosa Puertollano ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Cell ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
T Cell Signaling ◽  
Microtubule Organizing Center ◽  
Transport Pathway ◽  
Specific Transport ◽  
Transport Vesicles ◽  
Organizing Center

The MAL protein is an essential component of the specialized machinery for apical targeting in epithelial cells. The src family kinase Lck plays a pivotal role in T cell signaling. We show that MAL is required in T cells for efficient expression of Lck at the plasma membrane and activation of IL-2 transcription. To investigate the mechanism by which MAL regulates Lck targeting, we analyzed the dynamics of Lck and found that it travels to the plasma membrane in specific transport carriers containing MAL. Coimmunoprecipitation experiments indicated an association of MAL with Lck. Both carrier formation and partitioning of Lck into detergent-insoluble membranes were ablated in the absence of MAL. Polarization of T cell receptor for antigen (TCR) and microtubule-organizing center to immunological synapse (IS) were also defective. Although partial correction of the latter defects was possible by forced expression of Lck at the plasma membrane, their complete correction, formation of transport vesicles, partitioning of Lck, and restoration of signaling pathways, which are required for IL-2 transcription up-regulation, were achieved by exogenous expression of MAL. We concluded that MAL is required for recruitment of Lck to specialized membranes and formation of specific transport carriers for Lck targeting. This novel transport pathway is crucial for TCR-mediated signaling and IS assembly.

scholarly journals Stochastic model of T Cell repolarization during target elimination (II)

2021 ◽  
Author(s):  
Ivan Hornak ◽  
Heiko Rieger
Keyword(s):  
T Cell ◽  
Immunological Synapse ◽  
Molecular Motor ◽  
Initial Position ◽  
Cell Polarization ◽  
Target Cells ◽  
Microtubule Organizing Center ◽  
Tight Contact ◽  
Organizing Center ◽  
Arbitrary Position

Cytotoxic T lymphocytes (T cells) and natural killer cells form a tight contact, the immunological synapse (IS), with target cells, where they release their lytic granules containing perforin/granzyme and cytokine containing vesicles. During this process the cell repolarizes and moves the microtubule organizing center (MTOC) towards the IS. In the first part of our work we developed a computational model for the molecular-motor-driven motion of the MT cytoskeleton confined between plasma membrane and nucleus during T cell polarization and analyzed different mechanisms (cortical sliding and capture-shrinkage) that have been proposed on the basis of recent experiments. Here we use this model to analyze the dynamics of the MTOC during the repositioning process in situations in which a) the IS is in an arbitrary position with respect to the initial position of the MTOC and b) the T cell has two IS at two arbitrary positions. We observe several scenarios that have also been reported experimentally: the MTOC alternates stochastically (but with a well defined average transition time) between the two IS; it wiggles in between the two IS without transiting to one of the two; or it is at some point pulled to one of the two IS and stays there. Our model allows to predict which scenario emerges in dependency of the mechanisms in action and the number of dyneins present.

scholarly journals Actin reorganization at the centrosomal area and the immune synapse regulates polarized secretory traffic of multivesicular bodies in T lymphocytes

2020 ◽  
Author(s):  
Ana Bello-Gamboa ◽  
Marta Velasco ◽  
Solange Moreno ◽  
Gonzalo Herranz ◽  
Roxana Ilie ◽  
...  
Keyword(s):  
T Cell ◽  
Actin Cytoskeleton ◽  
Cell Receptor ◽  
Multivesicular Bodies ◽  
Microtubule Organizing Center ◽  
Independent Manner ◽  
Actin Reorganization ◽  
Immune Synapse ◽  
Cell Clones ◽  
Organizing Center

ABSTRACTT-cell receptor stimulation induces the convergence of multivesicular bodies towards the microtubule-organizing center (MTOC) and the polarization of the MTOC to the immune synapse (IS). These events lead to exosome secretion at the IS. We describe here that upon IS formation centrosomal area F-actin decreased concomitantly with MTOC polarization to the IS. PKCδ-interfered T cell clones showed a sustained level of centrosomal area F-actin associated with defective MTOC polarization. We analysed the contribution of two actin cytoskeleton-regulatory proteins, FMNL1 and paxillin, to the regulation of cortical and centrosomal F-actin networks. FMNL1β phosphorylation and F-actin reorganization at the IS were inhibited in PKCδ-interfered clones. F-actin depletion at the central region of the IS, a requirement for MTOC polarization, was associated with FMNL1β phosphorylation at its C-terminal, autoregulatory region. Interfering all FMNL1 isoforms prevented MTOC polarization; nonetheless, FMNL1β re-expression restored MTOC polarization in a centrosomal area F-actin reorganization-independent manner. Moreover, PKCδ-interfered clones exhibited decreased paxillin phosphorylation at the MTOC, which suggests an alternative actin cytoskeleton regulatory pathway. Our results infer that PKCδ regulates MTOC polarization and secretory traffic leading to exosome secretion in a coordinated manner by means of two distinct pathways, one involving FMNL1β regulation and controlling F-actin reorganization at the IS, and the other, comprising paxillin phosphorylation potentially controlling centrosomal area F-actin reorganization.

scholarly journals Spatiotemporal Regulation of Signaling: Focus on T Cell Activation and the Immunological Synapse

2020 ◽  
Vol 21 (9) ◽  
pp. 3283
Author(s):  
Esther Garcia ◽  
Shehab Ismail
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
T Cell ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
Signaling Network ◽  
Spatiotemporal Regulation

In a signaling network, not only the functions of molecules are important but when (temporal) and where (spatial) those functions are exerted and orchestrated is what defines the signaling output. To temporally and spatially modulate signaling events, cells generate specialized functional domains with variable lifetime and size that concentrate signaling molecules, enhancing their transduction potential. The plasma membrane is a key in this regulation, as it constitutes a primary signaling hub that integrates signals within and across the membrane. Here, we examine some of the mechanisms that cells exhibit to spatiotemporally regulate signal transduction, focusing on the early events of T cell activation from triggering of T cell receptor to formation and maturation of the immunological synapse.

scholarly journals Negative Regulation of T Cell Receptor–Lipid Raft Interaction by Cytotoxic T Lymphocyte–associated Antigen 4

2003 ◽  
Vol 197 (1) ◽  
pp. 129-135 ◽  
Author(s):  
Shunsuke Chikuma ◽  
John B. Imboden ◽  
Jeffrey A. Bluestone
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
T Lymphocyte ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Cytotoxic T Lymphocyte ◽  
Cell Receptor ◽  
T Cell Signaling ◽  
Signaling Complex

Cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) is an essential negative regulator of T cell activation. Recent evidence suggests that CTLA-4 association with the immunological synapse during contact with antigen-presenting cells is important for its inhibitory function. In the present study, we observed a direct interaction of CTLA-4 with the phosphorylated form of T cell receptor (TCR)ζ within the glycolipid-enriched microdomains associated with the T cell signaling complex. In this setting, CTLA-4 regulated the accumulation/retention of TCRζ in the signaling complex, as the lipid raft fractions from CTLA-4KO T cells contained significantly higher amounts of the TCR components when compared with wild-type littermates. In contrast, coligation of CTLA-4 with the TCR during T cell activation selectively decreased the amount of TCRζ that accumulated in the rafts. These results suggest that CTLA-4 functions to regulate T cell signaling by controlling TCR accumulation and/or retention within this a critical component of the immunological synapse.

scholarly journals Centrosome docking at the immunological synapse is controlled by Lck signaling

2011 ◽  
Vol 192 (4) ◽  
pp. 663-674 ◽  
Author(s):  
Andy Tsun ◽  
Ihjaaz Qureshi ◽  
Jane C. Stinchcombe ◽  
Misty R. Jenkins ◽  
Maike de la Roche ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Cell ◽  
Tyrosine Kinase ◽  
T Cell Receptor ◽  
Cytotoxic T Lymphocytes ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
Target Cells ◽  
Lytic Granules ◽  
Distal Side

Docking of the centrosome at the plasma membrane directs lytic granules to the immunological synapse. To identify signals controlling centrosome docking at the synapse, we have studied cytotoxic T lymphocytes (CTLs) in which expression of the T cell receptor–activated tyrosine kinase Lck is ablated. In the absence of Lck, the centrosome is able to translocate around the nucleus toward the immunological synapse but is unable to dock at the plasma membrane. Lytic granules fail to polarize and release their contents, and target cells are not killed. In CTLs deficient in both Lck and the related tyrosine kinase Fyn, centrosome translocation is impaired, and the centrosome remains on the distal side of the nucleus relative to the synapse. These results show that repositioning of the centrosome in CTLs involves at least two distinct steps, with Lck signaling required for the centrosome to dock at the plasma membrane.

scholarly journals The Polarity Protein Par1b/EMK/MARK2 Regulates T Cell Receptor-Induced Microtubule-Organizing Center Polarization

2009 ◽  
Vol 183 (2) ◽  
pp. 1215-1221 ◽  
Author(s):  
Joseph Lin ◽  
Kirk K. Hou ◽  
Helen Piwnica-Worms ◽  
Andrey S. Shaw
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
Microtubule Organizing Center ◽  
Organizing Center

scholarly journals Stochastic model of T Cell repolarization during target elimination (I)

2019 ◽  
Author(s):  
I. Hornak ◽  
H. Rieger
Keyword(s):  
Plasma Membrane ◽  
T Cell ◽  
Immunological Synapse ◽  
Molecular Motor ◽  
Cell Polarization ◽  
Target Cells ◽  
Microtubule Organizing Center ◽  
Tight Contact ◽  
Sliding Mechanism ◽  
Spatio Temporal

AbstractCytotoxic T lymphocytes (T) and natural killer (NK) cells are the main cytotoxic killer cells of the human body to eliminate pathogen-infected or tumorigenic cells (i.e. target cells). Once a NK or T cell has identified a target cell, they form a tight contact zone, the immunological synapse (IS). One then observes a re-polarization of the cell involving the rotation of the microtubule (MT) half-spindle and a movement of the microtubule organizing center (MTOC) to a position that is just underneath the plasma membrane at the center of the IS. Concomitantly a massive relocation of organelles attached to MTs is observed, including the Golgi apparatus, lytic granules and mitochondria. Since the mechanism of this relocation is still elusive we devise a theoretical model for the molecular motor driven motion of the MT half-spindle confined between plasma membrane and nucleus during T cell polarization. We analyze different scenarios currently discussed in the literature, the cortical sliding and the capture-shrinkage mechanisms, and compare quantitative predictions about the spatio-temporal evolution of MTOC position and spindle morphology with experimental observations. The model predicts the experimentally observed biphasic nature of the repositioning process due to an interplay between spindle geometry and motor forces and confirms the dominance of the capture-shrinkage over the cortical sliding mechanism when MTOC and IS are initially diametrically opposed. We also find that the two mechanisms act synergetically, thereby reducing the resources necessary for repositioning. Moreover, it turns out that the localization of dyneins in the pSMAC facilitates their interaction with the MTs. Our model also opens a way to infer details of the dynein distribution from the experimentally observed features of the MT half-spindle dynamics. In a subsequent publication we will address the issue of general initial configurations and situations in which the T cell established two immunological synapses.

scholarly journals Disc Large Homolog 1 Is Critical for Early T Cell Receptor Micro Cluster Formation and Activation in Human T Cells

Vaccines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1446
Author(s):  
June Guha ◽  
Raj Chari
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Signaling ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Synapse Formation ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
T Cell Signaling

T cell activation by antigen involves multiple sequential steps, including T cell receptor-microcluster TCR-(MC) formation, immunological synapse formation, and phosphorylation of mediators downstream of the TCR. The adaptor protein, Disc Large Homolog 1 (DLG1), is known to regulate proximal TCR signaling and, in turn, T cell activation, acting as a molecular chaperone that organizes specific kinases downstream of antigen recognition. In this study, we used knockdown and knockout technologies in human primary T cells and a human T cell line to demonstrate the role of DLG1 in proximal T cell signaling. High-end confocal microscopy was used for pictorial representation of T cell micro-clusters and colocalization studies. From all these studies, we could demonstrate that DLG1 functions even earlier than immunological synapse formation, to regulate T cell activation by promoting TCR-MC formation. Moreover, we found that DLG1 can act as a bridge between the TCR-ζ chain and ZAP70 while inhibiting binding of the phosphatase SHP1 to TCR-ζ. Together, these effects drive dysregulation of T cell activation in DLG1-deficient T cells. Overall, the activation and survival status of T cell is a critical determinant of effective vaccine response, and DLG1-mediated T cell signaling events can be a driving factor for improving vaccine-designing strategies.

TMEM16F mediates bystander TCR-CD3 membrane dissociation at the immunological synapse and potentiates T cell activation

2021 ◽  
Vol 14 (675) ◽  
pp. eabb5146
Author(s):  
Audrey Connolly ◽  
Rébecca Panes ◽  
Margaux Tual ◽  
Raphaël Lafortune ◽  
Angélique Bellemare-Pelletier ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Cell ◽  
T Cell Activation ◽  
Electrostatic Potential ◽  
Electrostatic Interactions ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
Cytoplasmic Domains ◽  
Dynamic Binding

Electrostatic interactions regulate many aspects of T cell receptor (TCR) activity, including enabling the dynamic binding of the TCR-associated CD3ε and CD3ζ chains to anionic lipids in the plasma membrane to prevent spontaneous phosphorylation. Substantial changes in the electrostatic potential of the plasma membrane occur at the immunological synapse, the interface between a T cell and an antigen-presenting cell. Here, we investigated how the electrostatic interactions that promote dynamic membrane binding of the TCR-CD3 cytoplasmic domains are modulated during signaling and affect T cell activation. We found that Ca2+-dependent activation of the phosphatidylserine scramblase TMEM16F, which was previously implicated in T cell activation, reduced the electrostatic potential of the plasma membrane during immunological synapse formation by locally redistributing phosphatidylserine. This, in turn, increased the dissociation of bystander TCR-CD3 cytoplasmic domains from the plasma membrane and enhanced TCR-dependent signaling and consequently T cell activation. This study establishes the molecular basis for the role of TMEM16F in bystander TCR–induced signal amplification and identifies enhancement of TMEM16F function as a potential therapeutic strategy for promoting T cell activation.

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