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Antonella Viola

Publications and source records attributed to Antonella Viola.

17 recordsLinked to original sources
PubMed2006

Orchestration of lymphocyte chemotaxis by mitochondrial dynamics.

Lymphocyte traffic is required to maintain homeostasis and perform appropriate immunological reactions. To migrate into inflamed tissues, lymphocytes must acquire spatial and functional asymmetries. Mitochondria are highly dynamic organelles that distribute in the cytoplasm to meet specific cellular needs, but whether this is essential to lymphocyte functions is unknown. We show that mitochondria specifically concentrate at the uropod during lymphocyte migration by a process involving rearrangements of their shape. Mitochondrial fission facilitates relocation of the organelles and promotes lymphocyte chemotaxis, whereas mitochondrial fusion inhibits both processes. Our data substantiate a new role for mitochondrial dynamics and suggest that mitochondria redistribution is required to regulate the motor of migrating cells.

Adenosine Triphosphate↗
PubMed2006

CD28 interaction with filamin-A controls lipid raft accumulation at the T-cell immunological synapse.

During physiological T-cell stimulation by antigen presenting cells (APCs), a major T-cell membrane rearrangement is known to occur leading to the organization of 'supramolecular activation clusters' at the immunological synapse. A possible role for the synapse is the generation of membrane compartments where signalling may be organized and propagated. Thus, engagement of the costimulatory molecule CD28 at the immunological synapse promotes the organization of a signalling compartment by inducing cytoskeletal changes and lipid raft accumulation. We identified the actin-binding protein Filamin-A (FLNa) as a novel molecular partner of CD28. We found that, after physiological stimulation, CD28 associated with and recruited FLNa into the immunological synapse, where FLNa organized CD28 signalling. FLNa knockdown by short interfering RNA (siRNA) inhibited CD28-mediated raft accumulation at the immunological synapse and T-cell costimulation. Together, our data indicate that CD28 binding to FLNa is required to induce the T-cell cytoskeletal rearrangements leading to recruitment of lipid microdomains and signalling mediators into the immunological synapse.

CD28 Antigens↗
PubMed2006

Tbx1 regulates population, proliferation and cell fate determination of otic epithelial cells.

The T-box transcription factor Tbx1 is required for inner ear morphogenesis. Tbx1 null mutants have a small otocyst that fails to grow and remodel and does not give rise to the vestibular and cochlear apparata. Here we show that Tbx1 expression-driven cell tracing identifies a population of otic epithelial cells that contributes to most of the otocyst. Tbx1 is essential for the contribution of this population to the inner ear. Ablation of Tbx1 after this cell population has established itself in the otocyst, restores marker expression lost in germ line mutants, but causes severe reduction in mitotic activity, cell autonomously. Furthermore, timed cell fate mapping demonstrates that loss of Tbx1 switches the fate of some members of the Tbx1-dependent cell population, from non-neurogenic to neurogenic, an event associated with activation of the Delta-Notch pathway. Finally, tissue-specific ablation of Tbx1 demonstrates that, while the abovementioned phenotypic abnormalities are due to loss of epithelial expression of Tbx1, cochlear morphogenesis requires mesodermal Tbx1 expression. We conclude that the main functions of Tbx1 in the inner ear are to control, cell-autonomously, contribution, size and fate of a large population of otic epithelial cells, and, cell non-autonomously, cochlear morphogenesis.

Animals↗
PubMed2006

T cells and their partners: The chemokine dating agency.

Chemokines and their receptors have long been recognized as key molecules directing leukocyte migration between blood, lymph and tissues. Evidence accumulated in recent years indicates that, in addition to their chemotactic functions, chemokine receptors are highly versatile players fine-tuning immune responses. Chemokine receptors and ligands have been implicated in dendritic-cell maturation, signal transmission at the immunological synapse between T lymphocytes and their cellular partners, and in the polarization of immune responses. These findings identify new roles for chemokines in T-cell triggering and activation of effector functions, and suggest that these small cytokines represent key conductors of adaptive immunity.

Chemokines↗
PubMed2005

Boosting antitumor responses of T lymphocytes infiltrating human prostate cancers.

Immunotherapy may provide valid alternative therapy for patients with hormone-refractory metastatic prostate cancer. However, if the tumor environment exerts a suppressive action on antigen-specific tumor-infiltrating lymphocytes (TIL), immunotherapy will achieve little, if any, success. In this study, we analyzed the modulation of TIL responses by the tumor environment using collagen gel matrix-supported organ cultures of human prostate carcinomas. Our results indicate that human prostatic adenocarcinomas are infiltrated by terminally differentiated cytotoxic T lymphocytes that are, however, in an unresponsive status. We demonstrate the presence of high levels of nitrotyrosines in prostatic TIL, suggesting a local production of peroxynitrites. By inhibiting the activity of arginase and nitric oxide synthase, key enzymes of L-arginine metabolism that are highly expressed in malignant but not in normal prostates, reduced tyrosine nitration and restoration of TIL responsiveness to tumor were achieved. The metabolic control exerted by the tumor on TIL function was confirmed in a transgenic mouse prostate model, which exhibits similarities with human prostate cancer. These results identify a novel and dominant mechanism by which cancers induce immunosuppression in situ and suggest novel strategies for tumor immunotherapy.

Adenocarcinoma↗
PubMed2005

T cell costimulation by chemokine receptors.

Signals mediated by chemokine receptors may compete with T cell receptor stop signals and determine the duration of T cell-antigen-presenting cell interactions. Here we show that during T cell stimulation by antigen-presenting cells, T cell chemokine receptors coupled to G(q) and/or G(11) protein were recruited to the immunological synapse by a G(i)-independent mechanism. When chemokine receptors were sequestered at the immunological synapse, T cells became insensitive to chemotactic gradients, formed more stable conjugates and finally responded with enhanced proliferation and cytokine production. We suggest that chemokine receptor trapping at the immunological synapse enhances T cell activation by improving T cell-antigen-presenting cell attraction and impeding the 'distraction' of successfully engaged T cells by other chemokine sources.

Antigen-Presenting Cells↗
PubMed2004

CD28 and lipid rafts coordinate recruitment of Lck to the immunological synapse of human T lymphocytes.

In T lymphocytes, the Src family kinase Lck associates lipid rafts and accumulates at the immunological synapse (IS) during T cell stimulation by APCs. Using CD4- or CD28-deficient murine T cells, it was suggested that recruitment of Lck to the IS depends on CD4, whereas CD28 sustains Lck activation. However, in human resting T cells, CD28 is responsible for promoting recruitment of lipid rafts to the IS by an unknown mechanism. Thus, we performed a series of experiments to determine 1) whether Lck is recruited to the IS through lipid rafts; and 2) whether Lck recruitment to the IS of human resting T cells depends on CD4 or on CD28 engagement. We found that CD28, but not CD4, stimulation induced recruitment of Lck into detergent-resistant domains as well as its accumulation at the IS. We also found that Lck recruitment to the IS depends on the CD28 COOH-terminal PxxPP motif. Thus, the CD28-3A mutant, generated by substituting the prolines in positions 208, 211, and 212 with alanines, failed to induce Lck and lipid raft accumulation at the synapse. These results indicate that CD28 signaling orchestrates both Lck and lipid raft recruitment to the IS to amplify T cell activation.

Amino Acid Motifs↗
PubMed2004

The inner side of T cell lipid rafts.

A key question in understanding the functional role of lipid rafts is whether lipid microdomains at the plasma membrane outer leaflet are coupled to lipid microdomains at the inner leaflet. By using a cyan-fluorescent protein (CFP) targeted to inner plasma membrane rafts of Jurkat T cells, we found that raft domains at the outer and inner leaflets are physically coupled and that this coupling requires cholesterol. Interestingly, TCR/CD3 cross-linking induces co-capping of the raft bilayer independently of cholesterol or signaling events, indicating that cholesterol-extracting drugs are unable to destroy TCR-lipid rafts interaction.

CD3 Complex↗
PubMed2004

Physiological T cell activation starts and propagates in lipid rafts.

Lipid rafts are plasma membrane compartments enriched in key signaling molecules. We have previously shown that in T lymphocytes anti-CD3 stimulation is insensitive to cholesterol extraction by methyl-beta-cyclodextrin (MbetaCD), suggesting that anti-CD3 induced signal transduction is independent of raft integrity. Here we show that, in contrast to T cell stimulation by anti-CD3 antibodies, T cell activation by a physiological ligand is mediated by signaling events taking place in lipid raft. Indeed, cholesterol depletion by MbetaCD resulted in reduced T cell activation in response to Epstein Barr Virus (EBV)-transformed B cells pulsed with a bacterial superantigen. Moreover, T cell stimulation by pulsed EBV-B cells, but not by anti-CD3 antibodies, induced recruitment of active Lck in detergent-resistant membranes, where the signal transduction is organized and amplified.

Antibodies↗
PubMed2004

Lipid rafts in lymphocyte activation.

The existence of sphingolipid- and cholesterol-rich membrane microdomains called "lipid rafts", as well as their role in lymphocyte biology, has been widely debated during the last few years. Plasma membrane microdomains seem to be primarily involved in initiation and propagation of the signal transduction cascade associated with lymphocyte activation. In this review, we discuss the recent literature suggesting that, during lymphocyte activation and chemotaxis, lipid rafts act as platforms to compartmentalise signalling and facilitate specific protein-protein interactions.

Animals↗
PubMed2003

TBX1 is required for inner ear morphogenesis.

TBX1 is thought to be a critical gene in the pathogenesis of del22q11/DiGeorge syndrome (DGS). Morphological abnormalities of the external ear and hearing impairment (conductive or sensorineural) affect the majority of patients. Here we show that homozygous mutation of the mouse homolog Tbx1 is associated with severe inner ear defects that prevent the formation of the cochlea and of the vestibulum. Consistent with phenotypic abnormalities, Tbx1 is expressed early in otocyst development in the otic epithelium and in the periotic mesenchyme. Tbx1 loss-of-function blocks inner ear development at early otocyst stage and after neurogenesis. Analysis of chimeras suggests that Tbx1 function is required in the otic epithelium cell autonomously, but abnormalities of the periotic mesenchyme indicate that the pathogenesis of the inner ear phenotype is complex. We propose a model where Tbx1 is required for expansion of a subpopulation of otic epithelial cells, which is required to form the vestibular and auditory organs. Our data suggest that Tbx1 deletion in del22q11 patients may cause not only external and middle ear defects but also sensorineural and vestibular phenotypes observed in these patients.

Animals↗
PubMed2003

Lymphocyte lipid rafts: structure and function.

Evidence has accumulated over the past few years to suggest that specialized plasma membrane regions enriched in cholesterol and glycolipids, called 'lipid rafts', are primarily involved in the initiation and propagation of the signal transduction cascade associated with lymphocyte activation. Considering the multitude of recent and often contradictory data, however, it appears that a critical reconsideration of the role of lipid rafts in lymphocyte activation is necessary and timely, particularly in light of a series of new experimental results that challenge the traditional view of the role of lipid rafts in lymphocyte activation.

Animals↗
PubMed2002

Vav cooperates with CD28 to induce NF-kappaB activation via a pathway involving Rac-1 and mitogen-activated kinase kinase 1.

CD28-delivered costimulatory signals are required to induce NF-kappaB activation in response to TCR stimulation. We have recently demonstrated that the mitogen-activated kinase kinase 1 (MEKK1), a kinase known to regulate the c-jun N-terminal kinase (JNK) pathway, is also involved in the CD28- and TCR-induced inhibitor of kappaB factor (IkappaB) kinases (IKK) and NF-kappaB activation. Searching for molecules that couple TCR and CD28 to MEKK1, we found that the guanine nucleotide exchange factor Vav synergized with CD28 stimulation in Jurkat cells to induce NF-kappaB transcriptional activity through the activation of IKKalpha and IKKbeta. Dominant negative mutants of Vav inhibited TCR- and CD28-NF-kappaB-dependent transcription by interfering with the activation of the IKK complex. Blocking Rac signaling downstream of Vav by dominant negative RacN17 exerts similar effects on IKK and NF-kappaB activation after TCR/CD28 stimulation. Finally, Vav-induced NF-kappaB activation in CD28 costimulated cells was inhibited by dominant negative MEKK(KM). These results identify Vav, Rac-1 and MEKK1 as components of a common pathway regulating both NF-kappaB and AP-1 that contributes to full activation of the CD28 response element (CD28RE).

CD28 Antigens↗
PubMed2002

Lipid rafts and T cell receptor signaling: a critical re-evaluation.

The current model suggesting that raft integrity is required for T cell activation is mostly (but not exclusively) based on the use of drugs, such as methyl-beta-cyclodextrin (M beta CD), that disorganize rafts and inhibit T cell receptor (TCR)-induced Ca2+ influx. Here we show that conditions that disrupt lipid raft integrity do not inhibit TCR triggering in Jurkat cells and normal T lymphocytes. Indeed, we found that the reported inhibition of TCR-induced Ca2+ influx by M beta CD treatment is mainly due to (a) nonspecific depletion of intracellular Ca2+ stores and (b) plasma membrane depolarization of T cells. When these side-effects are taken into account, raft disorganization does not alter TCR-dependent Ca2+ signaling. In line with these results, also TCR-induced tyrosine phosphorylation is not inhibited by dispersion of lipid rafts. By contrast, in the same conditions, Ca2+ signaling via the glycosylphosphatidylinositol (GPI)-anchored protein CD59 is totally abolished. These results indicate that, while signaling through GPI-anchored proteins requires lipid raft integrity, CD3-dependent TCR activation occurs independently of cholesterol extraction.

CD59 Antigens↗
PubMedDate not supplied

Lipid rafts in lymphocyte activation and migration.

Functional polarization of leukocytes is a requisite to accomplish immune function. Immune synapse formation or chemotaxis requires asymmetric redistribution of membrane receptors, signaling molecules and the actin cytoskeleton. There is increasing evidence that compartmentalization of the plasma membrane into distinct lipid microdomains is pivotal in establishing and maintaining leukocyte polarity. Specific rafts assemble into large-scale domains to create plasma membrane asymmetries at specific cell locations, thus coordinating temporally and spatially cell signaling in these processes. In this review we discuss the roles of lipid rafts as organizers of T lymphocyte polarity during cell activation and migration.

Actins↗