scholarly journals Dynamic changes in the mobility of LAT in aggregated lipid rafts upon T cell activation

2003 ◽  
Vol 160 (1) ◽  
pp. 125-135 ◽  
Author(s):  
Natsuko Tanimura ◽  
Masakazu Nagafuku ◽  
Yasuko Minaki ◽  
Yukio Umeda ◽  
Fumie Hayashi ◽  
...  
Keyword(s):  
T Cell ◽  
Lipid Rafts ◽  
T Cell Activation ◽  
Binding Sites ◽  
Cell Activation ◽  
Cell Receptor ◽  
Live Cells ◽  
Receptor Stimulation ◽  
Dynamic Changes ◽  
Phospholipase Cγ1

Lipid rafts are known to aggregate in response to various stimuli. By way of raft aggregation after stimulation, signaling molecules in rafts accumulate and interact so that the signal received at a given membrane receptor is amplified efficiently from the site of aggregation. To elucidate the process of lipid raft aggregation during T cell activation, we analyzed the dynamic changes of a raft-associated protein, linker for activation of T cells (LAT), on T cell receptor stimulation using LAT fused to GFP (LAT-GFP). When transfectants expressing LAT-GFP were stimulated with anti-CD3–coated beads, LAT-GFP aggregated and formed patches at the area of bead contact. Photobleaching experiments using live cells revealed that LAT-GFP in patches was markedly less mobile than that in nonpatched regions. The decreased mobility in patches was dependent on raft organization supported by membrane cholesterol and signaling molecule binding sites, especially the phospholipase Cγ1 binding site in the cytoplasmic domain of LAT. Thus, although LAT normally moves rapidly at the plasma membrane, it loses its mobility and becomes stably associated with aggregated rafts to ensure organized and sustained signal transduction required for T cell activation.

The molecular machinery for cAMP-dependent immunomodulation in T-cells

2006 ◽  
Vol 34 (4) ◽  
pp. 476-479 ◽  
Author(s):  
K. Taskén ◽  
A.J. Stokka
Keyword(s):  
T Cell ◽  
Immune Responses ◽  
Lipid Rafts ◽  
T Cell Activation ◽  
Negative Feedback ◽  
Cell Activation ◽  
Cell Receptor ◽  
Membrane Microdomains ◽  
Type I ◽  
Anchoring Protein

cAMP inhibits Src-family kinase signalling by PKA (protein kinase A)-mediated phosphorylation and activation of Csk (C-terminal Src kinase). The PKA type I–Csk pathway is assembled and localized in membrane microdomains (lipid rafts) and regulates immune responses activated through the TCR (T-cell receptor). PKA type I is targeted to the TCR–CD3 complex during T-cell activation via an AKAP (A-kinase-anchoring protein) that serves as a scaffold for the cAMP–PKA/Csk pathway in lipid rafts of the plasma membrane during T-cell activation. Displacement of PKA by anchoring disruption peptides prevents cAMP/PKA type I-mediated inhibition of T-cell activation. These findings provide functional evidence that PKA type I regulation of T-cell responses is dependent on AKAP anchoring. Furthermore, we show that upon TCR/CD28 co-ligation, β-arrestin in complex with PDE4 (phosphodiesterase 4) is recruited to lipid rafts. The CD28-mediated recruitment of PDE4 to lipid rafts potentiates T-cell immune responses and counteracts the local, TCR-induced production of cAMP that produces negative feedback in the absence of a co-receptor stimulus. The specific recruitment of PDE4 thus serves to abrogate the negative feedback by cAMP which is elicited in the absence of a co-receptor stimulus.

scholarly journals T-Cell Receptor Microclusters Critical for T-Cell Activation Are Formed Independently of Lipid Raft Clustering

2010 ◽  
Vol 30 (14) ◽  
pp. 3421-3429 ◽  
Author(s):  
Akiko Hashimoto-Tane ◽  
Tadashi Yokosuka ◽  
Chitose Ishihara ◽  
Machie Sakuma ◽  
Wakana Kobayashi ◽  
...  
Keyword(s):  
T Cell ◽  
Lipid Rafts ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Lipid Raft ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Resonance Energy ◽  
Careful Analysis ◽  
Cell Receptor

ABSTRACT We studied the function of lipid rafts in generation and signaling of T-cell receptor microclusters (TCR-MCs) and central supramolecular activation clusters (cSMACs) at immunological synapse (IS). It has been suggested that lipid raft accumulation creates a platform for recruitment of signaling molecules upon T-cell activation. However, several lipid raft probes did not accumulate at TCR-MCs or cSMACs even with costimulation and the fluorescence resonance energy transfer (FRET) between TCR or LAT and lipid raft probes was not induced at TCR-MCs under the condition of positive induction of FRET between CD3ζ and ZAP-70. The analysis of LAT mutants revealed that raft association is essential for the membrane localization but dispensable for TCR-MC formation. Careful analysis of the accumulation of raft probes in the cell interface revealed that their accumulation occurred after cSMAC formation, probably due to membrane ruffling and/or endocytosis. These results suggest that lipid rafts control protein translocation to the membrane but are not involved in the clustering of raft-associated molecules and therefore that the lipid rafts do not serve as a platform for T-cell activation.

scholarly journals Enhancement of lymphocyte responsiveness by a gain-of-function mutation of ZAP-70.

1996 ◽  
Vol 16 (12) ◽  
pp. 6765-6774 ◽  
Author(s):  
Q Zhao ◽  
A Weiss
Keyword(s):  
T Cell ◽  
B Cell ◽  
Cell Line ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cell Receptor ◽  
Sh2 Domain ◽  
Inhibitory Protein ◽  
Receptor Stimulation

The protein tyrosine kinase ZAP-70 plays an essential role in T-cell activation and development. After T-cell receptor stimulation, ZAP-70 is associated with the receptor and is phosphorylated on many tyrosine residues, including tyrosine 292 (Y-292), in the region between the C-terminal SH2 domain and the kinase domain (interdomain B). Here we show that a mutation of Y-292 (292F) or deletion of interdomain B enhanced the ability of ZAP-70 to reconstitute B-cell receptor stimulation-dependent NF-AT induction in a B-cell line deficient in Syk. In contrast, in a T-cell line, expression of 292F led to basal NF-AT induction independent of T-cell receptor stimulation. These results demonstrate that the role of Y-292 is to negatively regulate the function of ZAP-70 in lymphocytes. This appears to be a dominant function of interdomain B because deletion of most of interdomain B also resulted in a mutant of ZAP-70 with enhanced ability to reconstitute Syk-deficient DT-40 B cells. Since our biochemical studies did not reveal an effect of the 292F mutation on either the kinase activity of ZAP-70 or on the ability of ZAP-70 to bind to the receptor, we propose a model in which Y-292 interacts with an inhibitory protein to negatively regulate ZAP-70 function.

scholarly journals Induction of lysosomal and plasma membrane-bound sialidases in human T-cells via T-cell receptor

2004 ◽  
Vol 380 (2) ◽  
pp. 425-433 ◽  
Author(s):  
Peng WANG ◽  
Ji ZHANG ◽  
Hong BIAN ◽  
Ping WU ◽  
Reshma KUVELKAR ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cell Receptor ◽  
Th2 Cytokines ◽  
Receptor Stimulation ◽  
Human T Cell ◽  
Human T Cells

Among the three isoenzymes of neuraminidase (Neu) or sialidase, Neu-1 has been suggested to be induced by cell activation and to be involved in IL (interleukin)-4 biosynthesis in murine T-cells. In the present study, we found that antigen-induced airway eosinophilia, a typical response dependent on Th2 (T-helper cell type 2) cytokines, as well as mRNA expression of Th2 cytokines, including IL-4, are suppressed in Neu-1-deficient mice, thereby demonstrating the in vivo role of murine Neu-1 in regulation of Th2 cytokines. To elucidate the roles of various sialidases in human T-cell activation, we investigated their tissue distribution, gene induction and function. Neu-1 is the predominant isoenzyme at the mRNA level in most tissues and cells in both mice and humans, including T-cells. T-cells also have significant levels of Neu-3 mRNAs, albeit much lower than those of Neu-1, whereas the levels of Neu-2 mRNAs are minimal. In human T-cells, both Neu-1 and Neu-3 mRNAs are significantly induced by T-cell-receptor stimulation, as is sialidase activity against 4-methylumbelliferyl-N-acetylneuramic acid (a substrate for both Neu-1 and Neu-3) and the ganglioside GD1a [NeuAcα2-3Galβ1-3GalNAcβ1-4(NeuAcα2-3)Galβ1-4Glcβ1-cer] (a substrate for Neu-3, but not for Neu-1). The expression of the two sialidase genes may be under differential regulation. Western blot analysis and enzymic comparison with recombinant sialidases have revealed that Neu-3 is induced as a major isoform in activated cells. The induction of Neu-1 and Neu-3 in T-cells is unique. In human monocytes and neutrophils stimulated with various agents, the only observation of sialidase induction has been by IL-1 in neutrophils. Functionally, a major difference has been observed in Jurkat T-cell lines over-expressing Neu-1- and Neu-3. Upon T-cell receptor stimulation, IL-2, interferon-γ, IL-4 and IL-13 are induced in the Neu-1 line, whereas in the Neu-3 line the same cytokines are induced, with the exception of IL-4. Taken together, these results suggest an important immunoregulatory role for both Neu-1 and Neu-3 in humans.

scholarly journals Surface Cytotoxic T Lymphocyte–associated Antigen 4 Partitions Within Lipid Rafts and Relocates to the Immunological Synapse under Conditions of Inhibition of T Cell Activation

2002 ◽  
Vol 195 (10) ◽  
pp. 1337-1347 ◽  
Author(s):  
Peter J. Darlington ◽  
Miren L. Baroja ◽  
Thu A. Chau ◽  
Eric Siu ◽  
Vincent Ling ◽  
...  
Keyword(s):  
T Cell ◽  
Lipid Rafts ◽  
T Cell Activation ◽  
T Lymphocyte ◽  
Lipid Raft ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Cytotoxic T Lymphocyte ◽  
Cell Receptor ◽  
Subcellular Fractionation

T cell activation through the T cell receptor (TCR) involves partitioning of receptors into discrete membrane compartments known as lipid rafts, and the formation of an immunological synapse (IS) between the T cell and antigen-presenting cell (APC). Compartmentalization of negative regulators of T cell activation such as cytotoxic T lymphocyte–associated antigen-4 (CTLA-4) is unknown. Recent crystal structures of B7-ligated CTLA-4 suggest that it may form lattices within the IS which could explain the mechanism of action of this molecule. Here, we show that after T cell stimulation, CTLA-4 coclusters with the TCR and the lipid raft ganglioside GM1 within the IS. Using subcellular fractionation, we show that most lipid raft-associated CTLA-4 is on the T cell surface. Such compartmentalization is dependent on the cytoplasmic tail of CTLA-4 and can be forced with a glycosylphosphatidylinositol-anchor in CTLA-4. The level of CTLA-4 within lipid rafts increases under conditions of APC-dependent TCR–CTLA-4 coligation and T cell inactivation. However, raft localization, although necessary for inhibition of T cell activation, is not sufficient for CTLA-4–mediated negative signaling. These data demonstrate that CTLA-4 within lipid rafts migrates to the IS where it can potentially form lattice structures and inhibit T cell activation.

Association of CD26 with CD45RA outside lipid rafts attenuates cord blood T-cell activation

Blood ◽  
2004 ◽  
Vol 103 (3) ◽  
pp. 1002-1010 ◽  
Author(s):  
Seiji Kobayashi ◽  
Kei Ohnuma ◽  
Masahiko Uchiyama ◽  
Kouichi Iino ◽  
Satoshi Iwata ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cord Blood ◽  
Lipid Rafts ◽  
T Cell Receptor ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cell Receptor ◽  
Cell Protein ◽  
Membrane Microdomains

AbstractCD26 is a T-cell activation antigen that contains dipeptidyl peptidase IV activity and binds adenosine deaminase. Recent work showed that specialized membrane microdomains, also known as lipid rafts, play a key role in T-cell signaling. In this study, we investigate the role of CD26 in cord blood T-cell activation and signal transduction. We demonstrated that different expression levels of CD26 were observed between cord blood T cells (CBTCs) and peripheral blood T cells (PBTCs) and that CD26+CD45RA+ CBTCs were different compared with CD26+CD45RA+ PBTCs. Moreover, the comitogenic effect of CD26 was not as pronounced in CBTCs as in PBTCs. We also showed that CD26 cross-linking induced less phosphorylation of T-cell receptor-signaling molecules, lymphoid T-cell protein tyrosine kinase (Lck), zeta-associated protein 70 (ZAP-70), T-cell receptor ζ (TCRζ), and linker for activator of T cells (LAT) in CBTCs than in PBTCs. Furthermore, CD26 molecules associated with CD45RA molecules outside lipid rafts in CBTCs. Our results suggest that strong physical linkage of CD26 with CD45RA outside lipid rafts may be responsible for the attenuation of T-cell activation signaling through CD26, which may be responsible for immature immune response and the low incidence of severe graft-versus-host disease in cord blood transplantation. (Blood. 2004;103:1002-1010)

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