The phosphatase domains of LAR, CD45, and PTP1B: structural correlations with peptide-based inhibitors1

2000 ◽  
Vol 78 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Nicholas R Glover ◽  
Alan S Tracey
Keyword(s):  
Insulin Receptor ◽  
Charge Distribution ◽  
T Cell Activation ◽  
Active Site ◽  
Cell Activation ◽  
Cell Function ◽  
Protein Tyrosine Phosphatases ◽  
Surface Topology ◽  
X Ray ◽  
Protein Tyrosine

PTP1B is a cytosolic protein tyrosine phosphatase that is a regulator of the kinase activity of the insulin receptor; the two protein tyrosine phosphatases LAR and CD45 are receptor type phosphatases crucially important to cell function. LAR also is involved in regulation of the insulin receptor while CD45 is critical for T-cell activation. Although LAR and CD45 are both transmembrane phosphatases, these enzymes manifest their phosphatase activity through a catalytic cytosolic domain. We have utilized X-ray coordinates of related phosphatases (RPTPalpha and RPTPµ) and comparative protein modeling to obtain molecular models of the D1 catalytic domains of CD45 and LAR. The models were tested using established protocols and found to be comparable to low resolution X-ray structures. The structure obtained for LAR was compared with the recently reported X-ray structure. Both the CD45-D1 and LAR-D1 structures were then compared to and contrasted with PTP1B. The active site of pockets of the three enzymes were found to be very uniform in structure and charge distribution. Also, the gross surface topology around the active site was found to be somewhat similar for the 3 phosphatases. However, there were significant differences in surface topology, and, more importantly, large changes in surface charge distribution. The differences between the surface features of these enzymes provide an explanation for the selectivity of inhibition by a number of peptides.

scholarly journals Positive and negative regulation of T-cell activation through kinases and phosphatases

2003 ◽  
Vol 371 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Tomas MUSTELIN ◽  
Kjetil TASKÉN
Keyword(s):  
T Cell ◽  
Tyrosine Phosphorylation ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Protein Tyrosine Phosphatases ◽  
Negative Regulation ◽  
Intact Cells ◽  
Protein Tyrosine ◽  
Sequence Of Events

The sequence of events in T-cell antigen receptor (TCR) signalling leading to T-cell activation involves regulation of a number of protein tyrosine kinases (PTKs) and the phosphorylation status of many of their substrates. Proximal signalling pathways involve PTKs of the Src, Syk, Csk and Tec families, adapter proteins and effector enzymes in a highly organized tyrosine-phosphorylation cascade. In intact cells, tyrosine phosphorylation is rapidly reversible and generally of a very low stoichiometry even under induced conditions due to the fact that the enzymes removing phosphate from tyrosine-phosphorylated substrates, the protein tyrosine phosphatases (PTPases), have a capacity that is several orders of magnitude higher than that of the PTKs. It follows that a relatively minor change in the PTK/PTPase balance can have a major impact on net tyrosine phosphorylation and thereby on activation and proliferation of T-cells. This review focuses on the involvement of PTKs and PTPases in positive and negative regulation of T-cell activation, the emerging theme of reciprocal regulation of each type of enzyme by the other, as well as regulation of phosphotyrosine turnover by Ser/Thr phosphorylation and regulation of localization of signal components.

Role of protein tyrosine phosphatases in T cell activation

2003 ◽  
Vol 191 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Tomas Mustelin ◽  
Souad Rahmouni ◽  
Nunzio Bottini ◽  
Andres Alonso
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Protein Tyrosine Phosphatases ◽  
Tyrosine Phosphatases ◽  
Protein Tyrosine

scholarly journals Phosphorylation-Dependent Regulation of T-Cell Activation by PAG/Cbp, a Lipid Raft-Associated Transmembrane Adaptor

2003 ◽  
Vol 23 (6) ◽  
pp. 2017-2028 ◽  
Author(s):  
Dominique Davidson ◽  
Marcin Bakinowski ◽  
Matthew L. Thomas ◽  
Vaclav Horejsi ◽  
André Veillette
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Protein Tyrosine Phosphatases ◽  
Dominant Negative ◽  
Negative Regulator ◽  
Cell Fractionation ◽  
Protein Tyrosine

ABSTRACT PAG/Cbp (hereafter named PAG) is a transmembrane adaptor molecule found in lipid rafts. In resting human T cells, PAG is tyrosine phosphorylated and associated with Csk, an inhibitor of Src-related protein tyrosine kinases. These modifications are rapidly lost in response to T-cell receptor (TCR) stimulation. Overexpression of PAG was reported to inhibit TCR-mediated responses in Jurkat T cells. Herein, we have examined the physiological relevance and the mechanism of PAG-mediated inhibition in T cells. Our studies showed that PAG tyrosine phosphorylation and association with Csk are suppressed in response to activation of normal mouse T cells. By expressing wild-type and phosphorylation-defective (dominant-negative) PAG polypeptides in these cells, we found that the inhibitory effect of PAG is dependent on its capacity to be tyrosine phosphorylated and to associate with Csk. PAG-mediated inhibition was accompanied by a repression of proximal TCR signaling and was rescued by expression of a constitutively activated Src-related kinase, implying that it is due to an inactivation of Src kinases by PAG-associated Csk. We also attempted to identify the protein tyrosine phosphatases (PTPs) responsible for dephosphorylating PAG in T cells. Through cell fractionation studies and analyses of genetically modified mice, we established that PTPs such as PEP and SHP-1 are unlikely to be involved in the dephosphorylation of PAG in T cells. However, the transmembrane PTP CD45 seems to play an important role in this process. Taken together, these data provide firm evidence that PAG is a bona fide negative regulator of T-cell activation as a result of its capacity to recruit Csk. They also suggest that the inhibitory function of PAG in T cells is suppressed by CD45. Lastly, they support the idea that dephosphorylation of proteins on tyrosine residues is critical for the initiation of T-cell activation.

Protein-tyrosine phosphatase activity of CD45 is activated by sequential phosphorylation by two kinases

1994 ◽  
Vol 14 (8) ◽  
pp. 5523-5532
Author(s):  
D R Stover ◽  
K A Walsh
Keyword(s):  
T Cell Activation ◽  
Protein Tyrosine Phosphatase ◽  
Time Course ◽  
Cell Activation ◽  
Regulatory Mechanism ◽  
Transmembrane Protein ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine

We describe a potential regulatory mechanism for the transmembrane protein-tyrosine phosphatase CD45. Phosphorylation on both tyrosine and serine residues in vitro results in an activation of CD45 specifically toward one artificial substrate but not another. The activation of these kinases appears to be order dependent, as it is enhanced when phosphorylation of tyrosine precedes that of serine but phosphorylation in the reverse order yields no activation. Any of four protein-tyrosine kinases tested, in combination with the protein-serine/threonine kinase, casein kinase II, was capable of mediating this activation in vitro. The time course of phosphorylation of CD45 in response to T-cell activation is consistent with the possibility that this regulatory mechanism is utilized in vivo.

scholarly journals TRPM2 Is Not Required for T-Cell Activation and Differentiation

2022 ◽  
Vol 12 ◽  
Author(s):  
Niels C. Lory ◽  
Mikolaj Nawrocki ◽  
Martina Corazza ◽  
Joanna Schmid ◽  
Valéa Schumacher ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Transient Receptor Potential ◽  
Cell Function ◽  
Intestinal Inflammation ◽  
Activation Markers

Antigen recognition by the T-cell receptor induces a cytosolic Ca2+ signal that is crucial for T-cell function. The Ca2+ channel TRPM2 (transient receptor potential cation channel subfamily M member 2) has been shown to facilitate influx of extracellular Ca2+ through the plasma membrane of T cells. Therefore, it was suggested that TRPM2 is involved in T-cell activation and differentiation. However, these results are largely derived from in vitro studies using T-cell lines and non-physiologic means of TRPM2 activation. Thus, the relevance of TRPM2-mediated Ca2+ signaling in T cells remains unclear. Here, we use TRPM2-deficient mice to investigate the function of TRPM2 in T-cell activation and differentiation. In response to TCR stimulation in vitro, Trpm2-/- and WT CD4+ and CD8+ T cells similarly upregulated the early activation markers NUR77, IRF4, and CD69. We also observed regular proliferation of Trpm2-/- CD8+ T cells and unimpaired differentiation of CD4+ T cells into Th1, Th17, and Treg cells under specific polarizing conditions. In vivo, Trpm2-/- and WT CD8+ T cells showed equal specific responses to Listeria monocytogenes after infection of WT and Trpm2-/- mice and after transfer of WT and Trpm2-/- CD8+ T cells into infected recipients. CD4+ T-cell responses were investigated in the model of anti-CD3 mAb-induced intestinal inflammation, which allows analysis of Th1, Th17, Treg, and Tr1-cell differentiation. Here again, we detected similar responses of WT and Trpm2-/- CD4+ T cells. In conclusion, our results argue against a major function of TRPM2 in T-cell activation and differentiation.

scholarly journals Actin Cytoskeleton Regulates Calcium Dynamics and NFAT Nuclear Duration

2004 ◽  
Vol 24 (4) ◽  
pp. 1628-1639 ◽  
Author(s):  
Fabiola V. Rivas ◽  
James P. O'Keefe ◽  
Maria-Luisa Alegre ◽  
Thomas F. Gajewski
Keyword(s):  
T Cell ◽  
Actin Cytoskeleton ◽  
T Cell Activation ◽  
Actin Polymerization ◽  
Cell Activation ◽  
Cell Function ◽  
Immunological Synapse ◽  
Interleukin 2 ◽  
Actin Dynamics ◽  
Activated T Cells

ABSTRACT T-cell activation by antigen-presenting cells is accompanied by actin polymerization, T-cell receptor (TCR) capping, and formation of the immunological synapse. However, whether actin-dependent events are required for T-cell function is poorly understood. Herein, we provide evidence for an unexpected negative regulatory role of the actin cytoskeleton on TCR-induced cytokine production. Disruption of actin polymerization resulted in prolonged intracellular calcium elevation in response to anti-CD3, thapsigargin, or phorbol myristate acetate plus ionomycin, leading to persistent NFAT (nuclear factor of activated T cells) nuclear duration. These events were dominant, as the net effect of actin blockade was augmented interleukin 2 promoter activity. Increased surface expression of the plasma membrane Ca2+ ATPase was observed upon stimulation, which was inhibited by cytochalasin D, suggesting that actin polymerization contributes to calcium export. Our results imply a novel role for the actin cytoskeleton in modulating the duration of Ca2+-NFAT signaling and indicate that actin dynamics regulate features of T-cell activation downstream of receptor clustering.

scholarly journals Hypoxia-induced PD-L1/PD-1 crosstalk impairs T-cell function in sleep apnoea

2017 ◽  
Vol 50 (4) ◽  
pp. 1700833 ◽  
Author(s):  
Carolina Cubillos-Zapata ◽  
Jose Avendaño-Ortiz ◽  
Enrique Hernandez-Jimenez ◽  
Victor Toledano ◽  
Jose Casas-Martin ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Intermittent Hypoxia ◽  
Cell Activation ◽  
Cell Function ◽  
Sleep Apnoea ◽  
Orphan Receptor ◽  
Dependent Manner ◽  
Obstructive Sleep

Obstructive sleep apnoea (OSA) is associated with higher cancer incidence, tumour aggressiveness and cancer mortality, as well as greater severity of infections, which have been attributed to an immune deregulation. We studied the expression of programmed cell death (PD)-1 receptor and its ligand (PD-L1) on immune cells from patients with OSA, and its consequences on immune-suppressing activity. We report that PD-L1 was overexpressed on monocytes and PD-1 was overexpressed on CD8+ T-cells in a severity-dependent manner. PD-L1 and PD-1 overexpression were induced in both the human in vitro and murine models of intermittent hypoxia, as well as by hypoxia-inducible factor-1α transfection. PD-L1/PD-1 crosstalk suppressed T-cell proliferation and activation of autologous T-lymphocytes and impaired the cytotoxic activity of CD8+ T-cells. In addition, monocytes from patients with OSA exhibited high levels of retinoic acid related orphan receptor, which might explain the differentiation of myeloid-derived suppressor cells. Intermittent hypoxia upregulated the PD-L1/PD-1 crosstalk in patients with OSA, resulting in a reduction in CD8+ T-cell activation and cytotoxicity, providing biological plausibility to the increased incidence and aggressiveness of cancer and the higher risk of infections described in these patients.

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