scholarly journals Recombinant glycosyl-phosphatidylinositol-anchored proteins are not associated with protein kinases in transfected thymoma cells

1994 ◽  
Vol 304 (3) ◽  
pp. 853-859 ◽  
Author(s):  
P M Clissold
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Signal Sequence ◽  
Phosphatidyl Inositol ◽  
Protein Tyrosine Kinases ◽  
Receptor Protein ◽  
Protein Tyrosine ◽  
Stable Transfectants

The cross-linking by antibody of some glycosyl-phosphatidyl-inositol (GPI)-anchored proteins on the plasma membrane of T cells leads to cell activation. Phosphorylation of proteins on tyrosine residues has a central role in the control of T cell activation, and non-receptor protein tyrosine kinases can be coprecipitated with immune complexes of GPI-anchored proteins in T cell lysates. In order to investigate the nature of this interaction, two recombinant GPI-anchored proteins were constructed (using the GPI signal sequence from Thy-1), and their associations with protein tyrosine kinases in stable transfectants of a mouse thymoma have been investigated. One recombinant GPI protein is the extracellular domain of the human complement receptor-1, normally an integral membrane protein, and the other is the secreted protein, human tissue inhibitor of metalloproteinases. The latter protein should be foreign to the cell surface and yet has been expressed as a GPI-anchored protein at levels equivalent to the highly expressed antigens Thy-1 and Ly6.A2 on mouse thymoma cells. Neither of the two recombinant proteins, when immunoprecipitated from NP40 lysates of transfected cells, was associated with protein tyrosine kinases in contrast with the natural endogenous GPI-anchored proteins Thy-1 and Ly6.A2 in non-transfected parental cells. Moreover, high expression of foreign recombinant GPI protein appears to interfere with the association of the natural GPI proteins with protein tyrosine kinases.

scholarly journals Genetic Evidence of a Role for Lck in T-Cell Receptor Function Independent or Downstream of ZAP-70/Syk Protein Tyrosine Kinases

1998 ◽  
Vol 18 (5) ◽  
pp. 2855-2866 ◽  
Author(s):  
Jane Wong ◽  
David Straus ◽  
Andrew C. Chan
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Interleukin 2 ◽  
Protein Tyrosine Kinases ◽  
Homologous Region ◽  
Activation Markers ◽  
Protein Tyrosine ◽  
Signaling Events

ABSTRACT T-cell antigen receptor (TCR) engagement results in sequential activation of the Src protein tyrosine kinases (PTKs) Lck and Fyn and the Syk PTKs, ZAP-70 and Syk. While the Src PTKs mediate the phosphorylation of TCR-associated signaling subunits and the phosphorylation and activation of the Syk PTKs, the lack of a constitutively active Syk PTK has prohibited the analysis of Lck function downstream of these initiating signaling events. We describe here the generation of an activated Syk family PTK by substituting the kinase domain of Syk for the homologous region in ZAP-70 (designated as KS for kinase swap). Expression of the KS chimera resulted in its autophosphorylation, the phosphorylation of cellular proteins, the upregulation of T-cell activation markers, and the induction of interleukin-2 gene synthesis in a TCR-independent fashion. The KS chimera and downstream ZAP-70 or Syk substrates, such as SLP-76, were still phosphorylated when expressed in Lck-deficient JCaM1.6 T cells. However, expression of the KS chimera in JCaM1.6 cells failed to rescue downstream signaling events, demonstrating a functional role for Lck beyond the activation of the ZAP-70 and Syk PTKs. These results indicate that downstream TCR signaling pathways may be differentially regulated by ZAP-70 and Lck PTKs and provide a mechanism by which effector functions may be selectively activated in response to TCR stimulation.

scholarly journals Regulation of pp56lck during T-cell activation: functional implications for the src-like protein tyrosine kinases.

1987 ◽  
Vol 6 (9) ◽  
pp. 2727-2734 ◽  
Author(s):  
J. D. Marth ◽  
D. B. Lewis ◽  
C. B. Wilson ◽  
M. E. Gearn ◽  
E. G. Krebs ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Protein Tyrosine Kinases ◽  
Protein Tyrosine ◽  
Functional Implications

scholarly journals PAH- and PCB-induced Alterations of Protein Tyrosine Kinase and Cytokine Gene Transcription in Harbor Seal (Phoca Vitulina) PBMC

2005 ◽  
Vol 12 (2) ◽  
pp. 91-97 ◽  
Author(s):  
Jennifer C. C. Neale ◽  
Thomas P. Kenny ◽  
Ronald S. Tjeerdema ◽  
M. Eric Gershwin
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Critical Role ◽  
Harbor Seal ◽  
Lymphocyte Function ◽  
Altered Expression ◽  
Protein Tyrosine

Mechanisms underlyingin vitroimmunomodulatory effects of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were investigated in harbor seal peripheral leukocytes, via real-time PCR. We examined the relative genetic expression of the protein tyrosine kinases (PTKs)FynandItk, which play a critical role in T cell activation, and IL-2, a cytokine of central importance in initiating adaptive immune responses. IL-1, the macrophage-derived pro-inflammatory cytokine of innate immunity, was also included as a measure of macrophage function. Harbor seal PBMC were exposed to the prototypic immunotoxic PAH benzo[a]pyrene (BaP), 3,3',4,4',5,5'-hexachlorobiphenyl (CB-169), a model immunotoxic PCB, or DMSO (vehicle control). Exposure of Con A-stimulated harbor seal PBMC to both BaP and CB-169 produced significantly altered expression in all four targets relative to vehicle controls. The PTKsFynandItkwere both up-regulated following exposure to BaP and CB-169. In contrast, transcripts for IL-2 and IL-1 were decreased relative to controls by both treatments. Our findings are consistent with those of previous researchers working with human and rodent systems and support a hypothesis of contaminant-altered lymphocyte function mediated (at least in part) by disruption of T cell receptor (TCR) signaling and cytokine production.

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.

scholarly journals Itk and Fyn Make Independent Contributions to T Cell Activation

1997 ◽  
Vol 186 (12) ◽  
pp. 2069-2073 ◽  
Author(s):  
X. Charlene Liao ◽  
Dan R. Littman ◽  
Arthur Weiss
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Protein Tyrosine Kinases ◽  
Tcr Signaling ◽  
Peripheral T Cells ◽  
Tcr Signal Transduction ◽  
Deficient Mice ◽  
Nonreceptor Protein Tyrosine Kinases

Itk is a member of the Btk/Tec/Itk family of nonreceptor protein tyrosine kinases (PTKs), and has been implicated in T cell antigen receptor (TCR) signal transduction. Lck and Fyn are the Src-family nonreceptor PTKs that are involved in TCR signaling. To address the question of how these members of different families of PTKs functionally contribute to T cell development and to T cell activation, mice deficient for both Itk and either Lck or Fyn were generated. The Itk/Lck doubly deficient mice exhibited a phenotype similar to that of Lck-deficient mice. The phenotype of the Itk/Fyn doubly deficient mice was similar to that of Itk deficient mice. However the Itk/Fyn doubly deficient mice exhibited a more severe defect in TCR-induced proliferation of thymocytes and peripheral T cells than did mice deficient in either kinase alone. These data support the notion that Itk and Fyn both make independent contributions to TCR-induced T cell activation.

scholarly journals Cooperative Inhibition of  T-Cell Antigen Receptor Signaling by a Complex between a Kinase and a Phosphatase

1999 ◽  
Vol 189 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Jean-François Cloutier ◽  
André Veillette
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Tyrosine Kinases ◽  
Cell Activation ◽  
Tyrosine Phosphatase ◽  
Antigen Receptor ◽  
Negative Regulator ◽  
Tcr Signaling ◽  
Protein Tyrosine

Antigen receptor–triggered T-cell activation is mediated by the sequential action of the Src and Syk/Zap-70 families of protein tyrosine kinases (PTKs). Previously, we reported that another PTK termed p50csk was a potent negative regulator of T-cell receptor (TCR) signaling because of its ability to inactivate Src-related kinases. This inhibitory effect required the catalytic activity of Csk, as well as its Src homology (SH)3 and SH2 domains. Subsequent studies uncovered that, via its SH3 domain, p50csk was associated with PEP, a proline-enriched protein tyrosine phosphatase (PTP) of unknown function expressed in hemopoietic cells. Herein, we have attempted to identify the role of the Csk-PEP complex in T lymphocytes. The results of our experiments showed that, like Csk, PEP was a strong repressor of TCR signaling. This property was dependent on the phosphatase activity of PEP, as well as on the sequence mediating its binding to p50csk. Through reconstitution experiments in Cos-1 cells, evidence was obtained that Csk and PEP act synergistically to inhibit protein tyrosine phosphorylation by Src-related kinases, and that this effect requires their association. Finally, experiments with a substrate-trapping mutant of PEP suggested that PEP functions by dephosphorylating and inactivating the PTKs responsible for T-cell activation. In addition to giving novel insights into the mechanisms involved in the negative regulation of T-cell activation, these findings indicate that the association of an inhibitory PTK with a PTP constitutes a more efficient means of inhibiting signal transduction by Src family kinases in vivo.

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