scholarly journals Aggregation of Lipid Rafts Accompanies Signaling via the T Cell Antigen Receptor

1999 ◽  
Vol 147 (2) ◽  
pp. 447-461 ◽  
Author(s):  
Peter W. Janes ◽  
Steven C. Ley ◽  
Anthony I. Magee
Keyword(s):  
T Cell ◽  
Tyrosine Phosphorylation ◽  
Lipid Rafts ◽  
Antigen Receptor ◽  
Cross Linking ◽  
Tcr Signaling ◽  
T Cell Antigen Receptor ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Associated Proteins

The role of lipid rafts in T cell antigen receptor (TCR) signaling was investigated using fluorescence microscopy. Lipid rafts labeled with cholera toxin B subunit (CT-B) and cross-linked into patches displayed characteristics of rafts isolated biochemically, including detergent resistance and colocalization with raft-associated proteins. LCK, LAT, and the TCR all colocalized with lipid patches, although TCR association was sensitive to nonionic detergent. Aggregation of the TCR by anti-CD3 mAb cross-linking also caused coaggregation of raft-associated proteins. However, the protein tyrosine phosphatase CD45 did not colocalize to either CT-B or CD3 patches. Cross-linking of either CD3 or CT-B strongly induced tyrosine phosphorylation and recruitment of a ZAP-70(SH2)2–green fluorescent protein (GFP) fusion protein to the lipid patches. Also, CT-B patching induced signaling events analagous to TCR stimulation, with the same dependence on expression of key TCR signaling molecules. Targeting of LCK to rafts was necessary for these events, as a nonraft- associated transmembrane LCK chimera, which did not colocalize with TCR patches, could not reconstitute CT-B–induced signaling. Thus, our results indicate a mechanism whereby TCR engagement promotes aggregation of lipid rafts, which facilitates colocalization of LCK, LAT, and the TCR whilst excluding CD45, thereby triggering protein tyrosine phosphorylation.

Rosmarinic acid inhibits Ca2+-dependent pathways of T-cell antigen receptor-mediated signaling by inhibiting the PLC-γ1 and Itk activity

Blood ◽  
2003 ◽  
Vol 101 (9) ◽  
pp. 3534-3542 ◽  
Author(s):  
Mi-Ae Kang ◽  
Su-Young Yun ◽  
Jonghwa Won
Keyword(s):  
T Cells ◽  
T Cell ◽  
Signaling Pathways ◽  
Tyrosine Phosphorylation ◽  
Rosmarinic Acid ◽  
Antigen Receptor ◽  
Tcr Signaling ◽  
T Cell Antigen Receptor ◽  
Cell Antigen Receptor ◽  
Cell Antigen

Rosmarinic acid (RosA) is a hydroxylated compound frequently found in herbal plants and is mostly responsible for anti-inflammatory and antioxidative activity. Previously, we observed that RosA inhibited T-cell antigen receptor (TCR)– induced interleukin 2 (IL-2) expression and subsequent T-cell proliferation in vitro. In this study, we investigated in detail inhibitory mechanism of RosA on TCR signaling, which ultimately activates IL-2 promoter by activating transcription factors, such as nuclear factor of activated T cells (NF-AT) and activating protein-1 (AP-1). Interestingly, RosA inhibited NF-AT activation but not AP-1, suggesting that RosA inhibits Ca2+- dependent signaling pathways only. Signaling events upstream of NF-AT activation, such as the generation of inositol 1,4,5-triphosphate and Ca2+ mobilization, and tyrosine phosphorylation of phospholipase C-γ1 (PLC-γ1) were strongly inhibited by RosA. Tyrosine phosphorylation of PLC-γ1 is largely dependent on 3 kinds of protein tyrosine kinases (PTKs), ie, Lck, ZAP-70, and Itk. We found that RosA efficiently inhibited TCR-induced tyrosine phosphorylation and subsequent activation of Itk but did not inhibit Lck or ZAP-70. ZAP-70–dependent signaling pathways such as the tyrosine phosphorylation of LAT and SLP-76 and serine/threonine phosphorylation of mitogen-activated protein kinases (MAPKs) were intact in the presence of RosA, confirming that RosA suppresses TCR signaling in a ZAP-70–independent manner. Therefore, we conclude that RosA inhibits TCR signaling leading to Ca2+ mobilization and NF-AT activation by blocking membrane-proximal events, specifically, the tyrosine phosphorylation of inducible T cells kinase (Itk) and PLC-γ1.

scholarly journals Differential T-Cell Antigen Receptor Signaling Mediated by the Src Family Kinases Lck and Fyn

2000 ◽  
Vol 20 (4) ◽  
pp. 1426-1435 ◽  
Author(s):  
Michael F. Denny ◽  
Barbara Patai ◽  
David B. Straus
Keyword(s):  
Signal Transduction ◽  
T Cell ◽  
Tyrosine Phosphorylation ◽  
Antigen Receptor ◽  
Alternative Form ◽  
Tcr Signaling ◽  
T Cell Antigen Receptor ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Tcr Signal Transduction

ABSTRACT Src family tyrosine kinases play a key role in T-cell antigen receptor (TCR) signaling. They are responsible for the initial tyrosine phosphorylation of the receptor, leading to the recruitment of the ZAP-70 tyrosine kinase, as well as the subsequent phosphorylation and activation of ZAP-70. Molecular and genetic evidence indicates that both the Fyn and Lck members of the Src family can participate in TCR signal transduction; however, it is unclear to what extent they utilize the same signal transduction pathways and activate the same downstream events. We have addressed this issue by examining the ability of Fyn to mediate TCR signal transduction in an Lck-deficient T-cell line (JCaM1). Fyn was able to induce tyrosine phosphorylation of the TCR and recruitment of the ZAP-70 kinase, but the pattern of TCR phosphorylation was altered and activation of ZAP-70 was defective. Despite this, the SLP-76 adapter protein was inducibly tyrosine phosphorylated, and both the Ras–mitogen-activated protein kinase and the phosphatidylinositol 4,5-biphosphate signaling pathways were activated. TCR stimulation of JCaM1/Fyn cells induced the expression of the CD69 activation marker and inhibited cell growth, but NFAT activation and the production of interleukin-2 were markedly reduced. These results indicate that Fyn mediates an alternative form of TCR signaling which is independent of ZAP-70 activation and generates a distinct cellular phenotype. Furthermore, these findings imply that the outcome of TCR signal transduction may be determined by which Src family kinase is used to initiate signaling.

Hydroxychloroquine inhibits calcium signals in T cells: a new mechanism to explain its immunomodulatory properties

Blood ◽  
2000 ◽  
Vol 95 (11) ◽  
pp. 3460-3466 ◽  
Author(s):  
Frederick D. Goldman ◽  
Andrew L. Gilman ◽  
Clay Hollenback ◽  
Roberta M. Kato ◽  
Brett A. Premack ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tyrosine Phosphorylation ◽  
Antigen Receptor ◽  
Calcium Signal ◽  
Dependent Manner ◽  
Tcr Signaling ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Immunomodulatory Properties

Abstract Hydroxychloroquine (HCQ), a lysosomotropic amine, is an immunosuppressive agent presently being evaluated in bone marrow transplant patients to treat graft-versus-host disease. While its immunosuppressive properties have been attributed primarily to its ability to interfere with antigen processing, recent reports demonstrate HCQ also blocks T-cell activation in vitro. To more precisely define the T-cell inhibitory effects of HCQ, the authors evaluated T-cell antigen receptor (TCR) signaling events in a T-cell line pretreated with HCQ. In a concentration-dependent manner, HCQ inhibited anti-TCR–induced up-regulation of CD69 expression, a distal TCR signaling event. Proximal TCR signals, including inductive protein tyrosine phosphorylation, tyrosine phosphorylation of phospholipase C γ1, and total inositol phosphate production, were unaffected by HCQ. Strikingly, anti-TCR-crosslinking–induced calcium mobilization was significantly inhibited by HCQ, particularly at the highest concentrations tested (100 μmol/L) in both T-cell lines and primary T cells. HCQ, in a dose-dependent fashion, also reduced a B-cell antigen receptor calcium signal, indicating this effect may be a general property of HCQ. Inhibition of the calcium signal correlated directly with a reduction in the size of thapsigargin-sensitive intracellular calcium stores in HCQ-treated cells. Together, these findings suggest that disruption of TCR-crosslinking–dependent calcium signaling provides an additional mechanism to explain the immunomodulatory properties of HCQ.

scholarly journals Distinct tyrosine phosphorylation sites in ZAP-70 mediate activation and negative regulation of antigen receptor function.

1996 ◽  
Vol 16 (9) ◽  
pp. 5026-5035 ◽  
Author(s):  
G Kong ◽  
M Dalton ◽  
J Bubeck Wardenburg ◽  
D Straus ◽  
T Kurosaki ◽  
...  
Keyword(s):  
T Cell ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Antigen Receptor ◽  
B Cell Antigen Receptor ◽  
Receptor Signaling ◽  
T Cell Antigen Receptor ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Antigen Receptor Signaling

Biochemical and genetic evidence has implicated two families of protein tyrosine kinases (PTKs), the Src- and Syk-PTKs, in T- and B-cell antigen receptor signaling. ZAP-70 is a member of the Syk-PTKs that associates with the T-cell antigen receptor and undergoes tyrosine phosphorylation following receptor activation. Three tyrosine residues, Tyr-292, -492, and -493, have been identified as sites of phosphorylation following T-cell antigen receptor engagement. Utilizing ZAP-70- and Syk-deficient lymphocytes (Syk-DT40 cells), we provide biochemical and functional evidence that heterologous trans-phosphorylation of Tyr-493 by a Src-PTK is required for antigen receptor-mediated activation of both the calcium and ras pathways. In contrast, cells expressing mutations at Tyr-292 or -492 demonstrate hyperactive T- and B-cell antigen receptor phenotypes. Thus, phosphorylation of ZAP-70 mediates both activation and inactivation of antigen receptor signaling.

scholarly journals Extensive temporally regulated reorganization of the lipid raft proteome following T-cell antigen receptor triggering

2003 ◽  
Vol 369 (2) ◽  
pp. 301-309 ◽  
Author(s):  
Luca BINI ◽  
Sonia PACINI ◽  
Sabrina LIBERATORI ◽  
Silvia VALENSIN ◽  
Michela PELLEGRINI ◽  
...  
Keyword(s):  
T Cell ◽  
Lipid Rafts ◽  
Antigen Receptor ◽  
Temporal Analysis ◽  
Membrane Microdomains ◽  
T Cell Antigen Receptor ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Dynamic Structures ◽  
Tcr Signalling

Signalling by immunoreceptors is orchestrated at specific plasma membrane microdomains, referred to as lipid rafts. Here we present a proteomics approach to the temporal analysis of protein association with lipid rafts following T-cell antigen receptor (TCR) triggering. We show that TCR engagement promotes the temporally regulated recruitment of proteins participating in the TCR signalling cascade to lipid rafts. Furthermore, TCR triggering results in profound modifications in the composition of lipid rafts involving a number of proteins associated either directly or indirectly with both plasma and intracellular membranes. Raft-associated proteins can be clustered according to their temporal profile of raft association. The data identify lipid rafts as highly dynamic structures and reveal a dramatic impact of surface TCR triggering not only on components of the TCR signalling machinery but also on proteins implicated in a number of diverse cellular processes.

scholarly journals ZAP-70-Independent Ca2+ Mobilization and Erk Activation in Jurkat T Cells in Response to T-Cell Antigen Receptor Ligation

2001 ◽  
Vol 21 (21) ◽  
pp. 7137-7149 ◽  
Author(s):  
Xiaochuan Shan ◽  
Richard Balakir ◽  
Gabriel Criado ◽  
Jason S. Wood ◽  
Maria-Cristina Seminario ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tyrosine Phosphorylation ◽  
Antigen Receptor ◽  
Jurkat Cells ◽  
Jurkat T Cells ◽  
T Cell Antigen Receptor ◽  
Erk Activation ◽  
Cell Antigen Receptor ◽  
Cell Antigen

ABSTRACT The tyrosine kinase ZAP-70 has been implicated as a critical intermediary between T-cell antigen receptor (TCR) stimulation and Erk activation on the basis of the ability of dominant negative ZAP-70 to inhibit TCR-stimulated Erk activation, and the reported inability of anti-CD3 antibodies to activate Erk in ZAP-70-negative Jurkat cells. However, Erk is activated in T cells receiving a partial agonist signal, despite failing to activate ZAP-70. This discrepancy led us to reanalyze the ZAP-70-negative Jurkat T-cell line P116 for its ability to support Erk activation in response to TCR/CD3 stimulation. Erk was activated by CD3 cross-linking in P116 cells. However, this response required a higher concentration of anti-CD3 antibody and was delayed and transient compared to that in Jurkat T cells. Activation of Raf-1 and MEK-1 was coincident with Erk activation. Remarkably, the time course of Ras activation was comparable in the two cell lines, despite proceeding in the absence of LAT tyrosine phosphorylation in the P116 cells. CD3 stimulation of P116 cells also induced tyrosine phosphorylation of phospholipase C-γ1 (PLCγ1) and increased the intracellular Ca2+ concentration. Protein kinase C (PKC) inhibitors blocked CD3-stimulated Erk activation in P116 cells, while parental Jurkat cells were refractory to PKC inhibition. The physiologic relevance of these signaling events is further supported by the finding of PLCγ1 tyrosine phosphorylation, Erk activation, and CD69 upregulation in P116 cells on stimulation with superantigen and antigen-presenting cells. These results demonstrate the existence of two pathways leading to TCR-stimulated Erk activation in Jurkat T cells: a ZAP-70-independent pathway requiring PKC and a ZAP-70-dependent pathway that is PKC independent.

Sign in / Sign up

Export Citation Format

Share Document