Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.2.3.23 (GAS)
 957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of urokinase plasminogen activator (uPA) to its specific receptor (uPAR) facilitates migration of vascular smooth muscle cells (VSMC). However, the signaling cascade utilized by the urokinase receptor is only incompletely understood. We investigated intracellular uPA/uPAR signaling in human aortic VSMC from the cell membrane to the nucleus. uPA binding to VSMC induced a rapid and pronounced increase in tyrosine phosphorylation of several proteins with molecular masses of 53-60, 85-90, and 130-140 kDa. By using co-immunoprecipitation techniques and in vitro kinase assays, the uPAR-associated proteins were identified as Janus (Jak) and Src non-receptor protein-tyrosine kinases (PTK) Jak1, Tyk2, and p59(fyn), p53/56(lyn), p53/59(hck), and p55(fgr). Furthermore, uPA induced a time-dependent reversible translocation of the Stat1 (signal transducer and activator of transcription) protein to the VSMC nuclei, as shown by confocal microscopy studies. Using an electrophoretic mobility shift assay, we then demonstrated that Stat1 is rapidly activated in response to stimulation with uPA and specifically binds to the DNA regulatory elements GAS (interferon-gamma activation site) and ISRE (interferon-stimulated response element). Mobility supershift experiments confirmed DNA-protein complexes containing Stat1 protein. Migration experiments with double immunofluorescence staining revealed polarization of uPAR, and colocalization with Jak1 and Tyk2 to the leading edge of the migrating cells. Under the same conditions, Jak2, Jak3, and the Src-PTKs remained randomly distributed over the entire body of the cells. Our studies therefore suggest that, in VSMC, the uPAR-signaling complex utilizes at least two different mechanisms, a direct signaling pathway utilizing the Jak/Stat cascade and a second signal transduction mechanism via Src-like protein-tyrosine kinases. uPA-induced signaling via Jak/Stat is most likely involved in the regulation of cell migration, while the functional purpose of the uPA-associated Src-PTK activation remains to be elucidated.
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PMID:The Jak/Stat pathway and urokinase receptor signaling in human aortic vascular smooth muscle cells. 941 82

To study constitutive Janus kinase signaling, chimeric proteins were generated between the pointed domain of the ets transcription factor TEL and the cytosolic tyrosine kinase Jak2. The effects of these proteins on interleukin-3 (IL-3)-dependent proliferation of the hematopoietic cell line, Ba/F3, were studied. Fusion of TEL to the functional kinase (JH1) domain of Jak2 resulted in conversion of Ba/F3 cells to factor-independence. Importantly, fusion of TEL to the Jak2 pseudokinase (JH2) domain or a kinase-inactive Jak2 JH1 domain had no effect on IL-3-dependent proliferation of Ba/F3 cells. Active TEL-Jak2 constructs (consisting of either Jak2 JH1 or Jak2 JH2+JH1 domain fusions) were constitutively tyrosine-phosphorylated but did not affect phosphorylation of endogeneous Jak1, Jak2, or Jak3. TEL-Jak2 activation resulted in the constitutive tyrosine phosphorylation of Stat1, Stat3, and Stat5 as determined by detection of phosphorylation using activation-specific antibodies and by binding of each protein to a preferential GAS sequence in electrophoretic mobility shift assays. Elucidation of signaling events downstream of TEL-Jak2 activation may provide insight into the mechanism of leukemogenesis mediated by this oncogenic fusion protein.
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PMID:Fusion of the ets transcription factor TEL to Jak2 results in constitutive Jak-Stat signaling. 1036 Nov 34

We previously demonstrated that Jak3 is a primary response gene for G-CSF and ectopic overexpression of Jak3 can accelerate granulocytic differentiation of normal mouse bone marrow cells induced by G-CSF and GM-CSF. To gain insight into the regulation of G-CSF-induced transcription of Jak3, we constructed deletion and linker scanning mutants of the Jak3 promoter sequences and performed luciferase reporter assays in the murine myeloid cell line 32Dcl3, with and without G-CSF stimulation. These experiments showed that mutation of a -67 to -85 element, which contained a putative Sp1 binding site, or mutation of a -44 to -53 GAS element resulted in a marked reduction of Jak3 promoter activity. Electrophoretic mobility shift assays revealed that Sp1 and Stat3 present in nuclear lysates of 32Dcl3 cells stimulated with G-CSF can bind to the -67 to -85 element and -44 to -53 GAS element, respectively. In addition, cotransfection of a constitutively active mutant of Stat3 along with a Jak3 promoter/luciferase reporter resulted in enhanced Jak3 promoter activity. Together, these results demonstrate that activation of Jak3 transcription during G-CSF- induced granulocytic differentiation is mediated by the combined action of Sp1 and Stat3, a mechanism also shown to be important in IL-6-induced monocytic differentiation.
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PMID:Granulocyte colony-stimulating factor-induced upregulation of Jak3 transcription during granulocytic differentiation is mediated by the cooperative action of Sp1 and Stat3. 1651 16