Positive diepoxybutane test in a patient with Nijmegen breakage syndrome.
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Adolescent↗
Biomedical subjects
S Danielian
Publications and source records attributed to S Danielian.
Coupling of GTP-binding to the T cell receptor (TCR) zeta-chain with TCR-mediated signal transduction.
The zeta-subunit of the TCR binds GTP and is a well characterized substrate for a TCR-activated tyrosine kinase. To examine the possible coupling of GTP-binding to zeta with TCR-mediated signal transduction, a mutant (termed J32-3.2) of the T cell line Jurkat (J32) was used. Anti-TCR/CD3 stimulation of the TCR/CD3+ J32-3.2 cells resulted in a weak stimulation of both the phosphatidyl inositol and tyrosine kinase signal transduction pathways, as measured by changes in the level of free intracellular calcium, tyrosine phosphorylation of TCR-zeta, CD3-epsilon and ZAP-70, p56lck, or p59fyn tyrosine kinase activity and IL-2 gene activation. The impaired responsiveness of J32-3.2 cells to anti-TCR/CD3 mAb correlated with a low basal level of GTP-binding to zeta. Furthermore, in J32-3.2 cells TCR activation by antibody ligation caused a weaker increase in GTP-binding to the zeta-chain, as compared with that of wild-type J32 cells, which indicates for the first time that GTP-binding to zeta can be modulated by extracellular signals and suggest that the role of GTP-binding to zeta is to couple the TCR to intracellular signal transduction mechanisms.
Amino Acid Sequence↗
[Implication of tyrosine kinase p56lck in the activation of T lymphocytes].
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Antigens, CD↗
[The tyrosine kinases of the Src family: properties and roles in cells].
The protein tyrosine kinases (PTK) are implicated in cell proliferation processes. Furthermore, a number of viral oncogenes encode constitutively active variants of tyrosine kinases and several growth factor receptors possess intrinsic tyrosine kinase activity. The regulation and biological function of the kinase activity of Src family PTK are not yet well established. However, three of these kinases (src, yes and fgr) have been initially identified as products of viral oncogenes and a fourth (lck) is activated and overexpressed in certain lymphomas. In fact, several biological systems implicate and early and transient activation of Scr family PTK.
Genes, src↗
The lymphocyte-specific tyrosine protein kinase p56lck is endocytosed in Jurkat cells stimulated via CD2.
Incubation of the human T cells, Jurkat, with two sets of activating anti-CD2 mAb (T11(2) + T11(3), D66 + T11(1)) induced delocalization of p56lck and CD2 receptors from the plasma membrane and increased the tyrosine kinase activity of p56lck. The anti-CD2 mAb combination (T11(2) + T11(3)) that produced the most rapid increase in p56lck kinase activity also induced the most rapid delocalization of the kinase. In stimulated cells, both p56lck and CD2 receptors are detected in cytoplasmic vesicles. The internalization of p56lck in endocytic vesicles was established by confocal microscopy. By double staining it was shown that only part of the p56lck colocalized with the internalized CD2 receptor suggesting distinct sorting processes. Internalization of p56lck appeared to be specific of CD2 stimulation as: 1) in Jurkat cells triggered with an anti-CD3 mAb, p56lck was not internalized whereas CD3 receptors were completely endocytosed; 2) when cells were stimulated via CD4, the kinase and CD4 receptors remained associated with the plasma membrane. In addition, internalization of p56lck upon stimulation of CD2 receptors was not modified in CD2+/CD3-Jurkat cells indicating that CD3 is not involved in this process. The identification of different subcellular localizations of p56lck in resting and stimulated T cells should represent an important step in the definition of its functional activity.
Antigens, Differentiation, T-Lymphocyte↗
Both T cell receptor (TcR)-CD3 complex and CD2 increase the tyrosine kinase activity of p56lck. CD2 can mediate TcR-CD3-independent and CD45-dependent activation of p56lck.
T cell activation by triggering the T cell receptor (TcR)-CD3 complex leads to a dramatic increase in tyrosine phosphorylation of multiple cellular proteins. To date, there has been no direct evidence on the identity of the tyrosine kinase activity implicated in this signaling pathway. In this study, we demonstrate that activation of human T cells with anti-CD3 monoclonal antibody increases tyrosine kinase activity of p56lck. This extends our previous findings which demonstrated the involvement of p56lck kinase activity in the CD2 signal transduction pathway. The results from peripheral blood lymphocytes and Jurkat cell line showed in both cases an early and transient change in the specific activity of p56lck, followed by a shift to a higher apparent molecular mass. Therefore, to test directly the role of TcR-CD3 in CD2-induced activation of p56lck, we utilized mutant variants of the Jurkat cell line lacking in cell surface TcR-CD3. We found that cell surface expression of TcR-CD3 is not required for the activation of p56lck via CD2 but is necessary for the appearance of the reduced-electrophoretic-mobility form of p56lck observed after CD2 triggering. By isolating CD45- mutants from Jurkat cells, we observed that surface expression of the tyrosine phosphatase CD45 is required in order to increase p56lck activity following CD2 stimulation, while CD4-induced activation of the kinase remained unchanged. These data provide evidence for a specific functional linkage between CD2 and p56lck, in which CD45 may play an essential role.
Antibodies, Monoclonal↗
The tyrosine kinase activity of p56lck is increased in human T cells activated via CD2.
An early biochemical event associated with T cell activation is tyrosine phosphorylation. We have previously shown that p56lck, a lymphocyte-specific protein tyrosine kinase, is hyperphosphorylated on serine and tyrosine residues 15 minutes after activation via CD2 with a concomitant shift to a higher molecular mass. We now demonstrate that the tyrosine kinase activity of p56lck is increased within seconds following CD2 triggering. This activity decreases thereafter correlating with the appearance of changes in phosphorylation previously described. These results suggest that p56lck may play an important role in the CD2 activation pathway.
Antigens, CD↗
The retarded electrophoretic migration of p56lck induced by vanadate in lymphoma cells correlates with modified kinase activity.
p56lck is a src related lymphocyte specific tyrosine protein kinase which undergoes specific changes during T-cell activation, particularly the appearance of slow migrating forms. To analyze these forms, LSTRA cells were treated with vanadate. This resulted in increased phosphorylation of p56lck with the appearance of slow migrating forms. Renaturation of the p56lck bands after gel migration showed that vanadate mostly increased the activity of the lower band of p56lck. The upper bands had a reduced specific activity. In addition, the upper bands from vanadate treated cells displayed additional phosphorylated sites.
Animals↗
Phosphorylation of p56lck by external ATP in intact cells.
Recent studies have suggested a role for extracellular ATP. In this report we show that extracellular labelled ATP crosses the plasma membrane of intact lymphoma cells and peripheral blood lymphocytes and phosphorylates p56lck a tyrosine protein kinase specific of lymphoid cells. Two other phosphoproteins of 92Kd and 35Kd become detectable on alkali treated gels. Phosphorylation occurs within minutes following addition of ATP. ATP, GTP, ADP and an ATP analog prevent phosphorylation but not AMP nor Pi; trypsinization of cells abolishes labelling. The possible involvement of P2 purinergic receptors is discussed.
Adenosine Triphosphate↗
High pp60c-src level in human platelet dense bodies.
Phosphoproteins phosphorylated in vivo were examined in resting and thrombin-activated human blood platelets. Thrombin-stimulation resulted in an overall increase in labeled proteins containing phosphotyrosine. The most prominent was a protein of 60 Kd. By electroblotting, the 60 Kd protein was identified as the pp60c-src, the normal cellular homolog of the transforming protein of Rous sarcoma virus. We have examined the intracellular distribution of the pp60c-src within platelets. Use of immunoprecipitation and electrotransfer to study isolated membranes, alpha-granules, lysosomes, and dense granules (also termed dense bodies) revealed that pp60c-src was highly enriched in dense bodies. In view of the prominent role of these granules in platelet function, We postulate that protein phosphorylation by activated pp60c-src is involved in early steps of platelet activation.
Blood Platelets↗
The lymphocyte-specific protein tyrosine kinase p56lck is hyperphosphorylated on serine and tyrosine residues within minutes after activation via T cell receptor or CD2.
Human T cells can be activated and induced to proliferate through either the antigen-specific receptor complex (TcR-CD3) or the CD2 surface molecule. Following stimulation, both serine and tyrosine phosphorylation of cellular protein have been demonstrated to occur. p56lck, a protein tyrosine kinase associated to the inner face of the plasma membrane, is almost exclusively expressed in lymphoid cells, especially T cells. Within minutes after activation of a human T cell-derived line (Jurkat) via stimulation of either the TcR-CD3 complex or the CD2 glycoprotein, we observed a hyperphorphosylation of p56lck. A concomitant shift to a higher molecular weight in sodium dodecyl sulfate-polyacrylamide gel was also observed. Similar changes were obtained with phorbol 12-myristate 13-acetate. Tryptic phosphopeptide analysis of the hyperphosphorylated form of p56lck yielded new phosphorylated sites in serine residues and an increased tyrosine phosphorylation. These results suggest that p56lck may be intimately connected to the signaling pathway in T cell activation.
Antigens, Differentiation, T-Lymphocyte↗