u-PAR, in addition to regulating cell surface plasminogen activation, is thought to activate intracellular signal transduction cascades responsible for induction of gene expression, in particular C-/OT (Durnler et al (1994) Febs Lett 343:103-6 and PAI-2 (Dear et al (1997) Febs Lett 402:265-72). The recent identification of u-PAR bound sc-u-PA in association with activated Janus Kinase 1 (JAK-1) and its substrate, the Signal Transducer and Activator of Transcription (STAT-1) within triton X-100 insoluble complexes containing caveolae, (Ruthner et al. (19%) Fibrinolysis 10:Suppl 3, Abst 49) prompted us to postulate that IFN responsive genes, classically described as utilising the JAK/STAT signal transduction pathway may be responsive to u-PA/u-PAR mediated induction of JAK/STAT activity. To test our hypothesis HT-1080 fibrosaroma cells were transiently transfected with a 900 base pair promoter fragment of the IFN responsive gene 2'-5'oligonucleotide synthetase (Hu 250AS) fused to the Chloramphenicol Acetyl Transferase (CAT) gene. Transfected HT1080 cells were stimulated with 1 uM HMW-u-PA under serum free conditions for 16 hours, harvested and CAT assay performed. u-PA treatment resulted in a two fold induction in CAT activity over control cells. We next determined whether ISRE's could independently convey the inductive effects of u-PA To this end HT1080 cells were transiently transfected with a promoter construct harbouring three ISRE sequences in tandem fused to the CAT reporter gene u-PA treatment of transfected cells also resulted in a two fold induction in CAT activity suggesting the involvement of ISRE's in u-PAR mediated modulation of IFN responsive genes. Our results demonstrate that in addition to activating c-fos and PAI-2 gene expression u-PAR occupancy also results in transactivation of Interferon responsive promoters presumably utilising the JAK-1/STAT pathway.
|Number of pages||1|
|Journal||Fibrinolysis and Proteolysis|
|Issue number||SUPPL. 3|
|Publication status||Published - 1 Dec 1997|