scholarly journals Analysis of centrosomal area actin reorganization and centrosome polarization upon lymphocyte activation at the immunological synapse

2021 ◽  
Author(s):  
Manuel Izquierdo
Keyword(s):  
Actin Cytoskeleton ◽  
B Lymphocytes ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
T And B Lymphocytes ◽  
Initial Increase ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Actin Reorganization ◽  
Cytoskeleton Reorganization

T cell receptor (TCR) and B cell receptor (BCR) stimulation of T and B lymphocytes, by antigen presented on an antigen-presenting cell (APC) induces the formation of the immunological synapse (IS). IS formation is associated with an initial increase in cortical filamentous actin (F-actin) at the IS, followed by a decrease in F-actin density at the central region of the IS, which contains the secretory domain. This is followed by the convergence of secretion vesicles towards the centrosome, and the polarization of the centrosome to the IS. These reversible, cortical actin cytoskeleton reorganization processes occur during lytic granule secretion in cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, proteolytic granules secretion in B lymphocytes and during cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. In addition, several findings obtained in T and B lymphocytes forming IS show that actin cytoskeleton reorganization also occurs at the centrosomal area. F-actin reduction at the centrosomal area appears to be associated with centrosome polarization. In this chapter we deal with the analysis of centrosomal area F-actin reorganization, as well as the centrosome polarization analysis towards the IS.

scholarly journals Role of Actin Cytoskeleton Reorganization in Polarized Secretory Traffic at the Immunological Synapse

2021 ◽  
Vol 9 ◽  
Author(s):  
Victor Calvo ◽  
Manuel Izquierdo
Keyword(s):  
Actin Cytoskeleton ◽  
B Lymphocytes ◽  
Immunological Synapse ◽  
Biological Significance ◽  
Cell Receptor ◽  
T And B Lymphocytes ◽  
Initial Increase ◽  
Actin Reorganization ◽  
Immune Synapse ◽  
Cytoskeleton Reorganization

T cell receptor (TCR) and B cell receptor (BCR) stimulation by antigen presented on an antigen-presenting cell (APC) induces the formation of the immune synapse (IS), the convergence of secretory vesicles from T and B lymphocytes toward the centrosome, and the polarization of the centrosome to the immune synapse. Immune synapse formation is associated with an initial increase in cortical F-actin at the synapse, followed by a decrease in F-actin density at the central region of the immune synapse, which contains the secretory domain. These reversible, actin cytoskeleton reorganization processes occur during lytic granule degranulation in cytotoxic T lymphocytes (CTL) and cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. Recent evidences obtained in T and B lymphocytes forming synapses show that F-actin reorganization also occurs at the centrosomal area. F-actin reduction at the centrosomal area appears to be involved in centrosome polarization. In this review we deal with the biological significance of both cortical and centrosomal area F-actin reorganization and some of the derived biological consequences.

scholarly journals Coxiella burnetii Induces Reorganization of the Actin Cytoskeleton in Human Monocytes

1998 ◽  
Vol 66 (11) ◽  
pp. 5527-5533 ◽  
Author(s):  
Sonia Meconi ◽  
Véronique Jacomo ◽  
Patrice Boquet ◽  
Didier Raoult ◽  
Jean-Louis Mege ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Coxiella Burnetii ◽  
Actin Polymerization ◽  
Q Fever ◽  
Morphological Changes ◽  
Critical Role ◽  
Filamentous Actin ◽  
Cytoskeleton Reorganization ◽  
Membrane Protrusions ◽  
Actin Protrusions

ABSTRACT Coxiella burnetii, an obligate intracellular bacterium which survives in myeloid cells, causes Q fever in humans. We previously demonstrated that virulent C. burnetiiorganisms are poorly internalized by monocytes compared to avirulent variants. We hypothesized that a differential mobilization of the actin cytoskeleton may account for this distinct phagocytic behavior. Scanning electron microscopy demonstrated that virulent C. burnetii stimulated profound and polymorphic changes in the morphology of THP-1 monocytes, consisting of membrane protrusions and polarized projections. These changes were transient, requiring 5 min to reach their maximum extent and vanishing after 60 min of incubation. In contrast, avirulent variants of C. burnetii did not induce any significant changes in cell morphology. The distribution of filamentous actin (F-actin) was then studied with a specific probe, bodipy phallacidin. Virulent C. burnetii induced a profound and transient reorganization of F-actin, accompanied by an increase in the F-actin content of THP-1 cells. F-actin was colocalized with myosin in cell protrusions, suggesting that actin polymerization and the tension of actin-myosin filaments play a role in C. burnetii-induced morphological changes. In addition, contact between the cell and the bacterium seems to be necessary to induce cytoskeleton reorganization. Bacterial supernatants did not stimulate actin remodeling, and virulent C. burnetii organisms were found in close apposition with F-actin protrusions. The manipulation of the actin cytoskeleton by C. burnetiimay therefore play a critical role in the internalization strategy of this bacterium.

Lysophosphatidic acid-mediated augmentation of cardiomyocyte lipoprotein lipase involves actin cytoskeleton reorganization

2005 ◽  
Vol 288 (6) ◽  
pp. H2802-H2810 ◽  
Author(s):  
Thomas Pulinilkunnil ◽  
Ding An ◽  
Sanjoy Ghosh ◽  
Dake Qi ◽  
Girish Kewalramani ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Lipoprotein Lipase ◽  
Lysophosphatidic Acid ◽  
Actin Polymerization ◽  
Contractile Function ◽  
Rho Kinase ◽  
Filamentous Actin ◽  
Membrane Translocation ◽  
Downstream Effector ◽  
Cytoskeleton Reorganization

The lipoprotein lipase (LPL)-augmenting property of lysophosphatidylcholine requires the formation of lysophosphatidic acid (LPA) ( J Mol Cell Cardiol 37: 931–938, 2004). Given that the actin cytoskeleton has been implicated in regulating cardiomyocyte LPL, we examined whether LPL secretion after LPA involves actin cytoskeleton reassembly. Incubation of myocytes with LPA (1–100 nM) increased basal and heparin-releasable LPL (HR-LPL), an effect that was independent of shifts in LPL mRNA. The influence of LPA on myocyte LPL was reflected at the coronary lumen, with substantial increases of the enzyme at this location. Incubation of myocytes with cytochalasin D not only blocked LPA-induced augmentation of HR-LPL but also abrogated filamentous actin formation. These effects of LPA were likely receptor mediated. Exposure of myocytes to LPA facilitated significant membrane translocation of RhoA and its downstream effector Rho kinase I (ROCK I), and blocking this effect with Y-27632 appreciably reduced basal and HR-LPL activity. Incubation of adipose tissue with LPA also significantly enhanced basal and HR-LPL activity, suggesting that sarcomeric actin likely has a limited role in influencing the LPL secretory function of LPA in the myocyte. Comparable to LPA, hyperglycemia also caused significant membrane translocation of RhoA and ROCK I in hearts isolated from diazoxide-treated animals, effects that were abrogated using insulin. Overall, our data suggest that comparable to hyperglycemia, LPA-induced increases in cardiac LPL occurred via posttranscriptional mechanisms and processes that likely required RhoA activation and actin polymerization. Whether this increase in LPL augments triglyceride deposition in the heart leading to eventual impairment in contractile function is currently unknown.

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.

Mechanical force-activated phospholipase D is mediated by Gα12/13-Rho and calmodulin-dependent kinase in renal epithelial cells

2005 ◽  
Vol 289 (4) ◽  
pp. F826-F834 ◽  
Author(s):  
Jenny Ziembicki ◽  
Rajnish Tandon ◽  
Jeffrey R. Schelling ◽  
John R. Sedor ◽  
R. Tyler Miller ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Actin Cytoskeleton ◽  
Signaling Pathways ◽  
Phospholipase D ◽  
Mdck Cells ◽  
Mechanical Force ◽  
Rgs Proteins ◽  
Filamentous Actin ◽  
Renal Epithelial Cells ◽  
Cytoskeleton Reorganization

The renal glomerulus, the site of plasma ultrafiltration, is exposed to mechanical force in vivo arising from capillary blood pressure and fluid flow. Studies of cultured podocytes demonstrate that they respond to stretch by altering the structure of the actin cytoskeleton, but the mechanisms by which physical force triggers this architectural change and the signaling pathways that lead to generation of second messengers are not defined. In the present study, we found that in renal epithelial cells [podocytes and Madin-Darby canine kidney (MDCK) cells], application of mechanical force to the cell surface through fibronectin-coated ferric beads and exposure of the cells to magnetic force lead to Rho translocation and actin cytoskeleton reorganization. This application of force recruited Rho and filamentous actin (F-actin) to bead loci and subsequently stimulated phospholipase D (PLD), a downstream effector of Rho. Using MDCK cells that stably express regulators of G protein-signaling (RGS) proteins [RGS4 attenuates Gαi and Gαq, and the p115RhoGEF-RGS domain (p115-RGS) attenuates Gα12/13] to define the signaling pathway, we found that mechanical force induced Gα12/13-Rho activation and increased F-actin to stimulate PLD activity. The activation can be partially prevented by the C3 exoenzyme. Pretreatment of the cells with chemical inhibitors of several kinases showed that calmodulin-dependent kinase is also involved in stretch-induced PLD activation by a separate pathway. Taken together, our data demonstrate that in cultured podocytes and MDCK cells, mechanical force leads to actin cytoskeleton reorganization and PLD activation. The signaling pathways for PLD activation involve Gα12/13/Rho/F-actin and calmodulin-dependent kinase.

scholarly journals Lipid Rafts Interaction of the ARID3A Transcription Factor with EZRIN and G-Actin Regulates B-Cell Receptor Signaling

Diseases ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 22
Author(s):  
Christian Schmidt ◽  
Laura Christian ◽  
Tyler A. Smith ◽  
Josephine Tidwell ◽  
Dongkyoon Kim ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Actin Cytoskeleton ◽  
B Cell ◽  
Lipid Rafts ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Actin Binding ◽  
Cortical Actin ◽  
Downstream Signaling ◽  
B Cell Receptor Signaling

Several diseases originate via dysregulation of the actin cytoskeleton. The ARID3A/Bright transcription factor has also been implicated in malignancies, primarily those derived from hematopoietic lineages. Previously, we demonstrated that ARID3A shuttles between the nucleus and the plasma membrane, where it localizes within lipid rafts. There it interacts with components of the B-cell receptor (BCR) to reduce its ability to transmit downstream signaling. We demonstrate here that a direct component of ARID3A-regulated BCR signal strength is cortical actin. ARID3A interacts with actin exclusively within lipid rafts via the actin-binding protein EZRIN, which confines unstimulated BCRs within lipid rafts. BCR ligation discharges the ARID3A–EZRIN complex from lipid rafts, allowing the BCR to initiate downstream signaling events. The ARID3A–EZRIN interaction occurs almost exclusively within unpolymerized G-actin, where EZRIN interacts with the multifunctional ARID3A REKLES domain. These observations provide a mechanism by which a transcription factor directly regulates BCR signaling via linkage to the actin cytoskeleton with consequences for B-cell-related neoplasia.

scholarly journals Multiple actin networks coordinate mechanotransduction at the immunological synapse

2020 ◽  
Vol 219 (2) ◽  
Author(s):  
Daniel Blumenthal ◽  
Janis K. Burkhardt
Keyword(s):  
T Cell ◽  
Actin Cytoskeleton ◽  
Immunological Synapse ◽  
Adaptive Immune Response ◽  
Cell Receptor ◽  
Antigenic Specificity ◽  
Tcr Signaling ◽  
Actin Networks ◽  
Cell Structures ◽  
Underlying Mechanisms

Activation of naive T cells by antigen-presenting cells (APCs) is an essential step in mounting an adaptive immune response. It is known that antigen recognition and T cell receptor (TCR) signaling depend on forces applied by the T cell actin cytoskeleton, but until recently, the underlying mechanisms have been poorly defined. Here, we review recent advances in the field, which show that specific actin-dependent structures contribute to the process in distinct ways. In essence, T cell priming involves a tug-of-war between the cytoskeletons of the T cell and the APC, where the actin cytoskeleton serves as a mechanical intermediate that integrates force-dependent signals. We consider each of the relevant actin-rich T cell structures separately and address how they work together at the topologically and temporally complex cell–cell interface. In addition, we address how this mechanobiology can be incorporated into canonical immunological models to improve how these models explain T cell sensitivity and antigenic specificity.

scholarly journals Actin clearance promotes polarized dynein accumulation at the immunological synapse

2018 ◽  
Author(s):  
Elisa Sanchez ◽  
Xin Liu ◽  
Morgan Huse
Keyword(s):  
T Cell ◽  
Immunological Synapse ◽  
Cell Receptor ◽  
Actin Dynamics ◽  
Synaptic Membrane ◽  
Filamentous Actin ◽  
Antigen Presenting Cell ◽  
Imaging Methodology ◽  
Antigen Presenting ◽  
Cell Effector Function

Immunological synapse (IS) formation between a T cell and an antigen-presenting cell is accompanied by the reorientation of the T cell centrosome toward the interface. This polarization response is thought to enhance the specificity of T cell effector function by enabling the directional secretion of cytokines and cytotoxic factors toward the antigen-presenting cell. Centrosome reorientation is controlled by polarized signaling through diacylglycerol (DAG) and protein kinase C (PKC). This drives the recruitment of the motor protein dynein to the IS, where it pulls on microtubules to reorient the centrosome. Here, we used T cell receptor photoactivation and imaging methodology to investigate the mechanisms controlling dynein accumulation at the synapse. Our results revealed a remarkable spatiotemporal correlation between dynein recruitment to the synaptic membrane and the depletion of cortical filamentous actin (F-actin) from the same region, suggesting that the two events were causally related. Consistent with this hypothesis, we found that pharmacological disruption of F-actin dynamics in T cells impaired both dynein accumulation and centrosome reorientation. DAG and PKC signaling were necessary for synaptic F-actin clearance and dynein accumulation, while calcium signaling and microtubules were dispensable for both responses. Taken together, these data provide mechanistic insight into the polarization of cytoskeletal regulators and highlight the close coordination between microtubule and F-actin architecture at the IS.

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