Oxidative Stress Triggers STAT3 Tyrosine Phosphorylation and Nuclear Translocation in Human Lymphocytes

Abstract

Oxidizing agents are powerful activators of factors responsible for the transcriptional activation of cytokine-encoding genes involved in tissue injury. In this study we show evidence that STAT3 is a transcription factor whose activity is modulated by H 2 O 2 in human lymphocytes, in which endogenous catalase had previously been inhibited. H 2 O 2 -induced nuclear translocation of STAT3 to form sequence-specific DNA-bound complexes was evidenced by immunoblotting of nuclear fractions and electrophoretic mobility shift assays, and vanadate was found to strongly synergize with STATs (signal transducers and activators of transcription) are a class of transcription factors bearing SH2 domains that become activated upon tyrosine phosphorylation. STATs are often activated by members of the JAK family of protein-tyrosine kinases (PTKs) in response to cytokine stimulation. This activation mechanism involves the SH2 domain-dependent recruitment of the STATs to tyrosine-phosphorylated cytokine receptors. The STATs then become phosphorylated by receptorassociated JAKs, which induces their dimerization via reciprocal SH2-phosphotyrosine interaction. STAT dimers then enter the nucleus and bind to specific DNA elements, thereby activating the transcription of a number of genes. The JAK-STAT pathway has been the subject of many recent comprehensive reviews (17-21). STAT3, a well characterized 92-kDa protein, has been shown to become activated by both epidermal growth factor and interleukin-6 in human A-431 cells (22). Because the ROI generated in response to various external stimuli can play a role both as regulators of transcription factors, including nuclear factors B (2, 23) and AT (24), and as inhibitors of protein-tyrosine phosphatases (PTPases) (25-27), we have investigated whether H 2 O 2 and other oxidizing agents could modulate STAT3 function in human lymphocytes. Enhanced phosphotyrosine accumulation could then result from the combined effects of increased phosphorylation and decreased dephosphorylation. Moreover, the DNA binding activity of STATs is known to depend primarily on tyrosine phosphorylation (19, 28 -31), although serine phosphorylation is also important in modulating the binding affinity of STAT3 (32-34). Here we show for the first time that STAT3 is phosphorylated on tyrosine residue(s), translocated to the nucleus, and elicited to bind to specific DNA elements upon lymphocyte treatment with H 2 O 2 . An additive effect between H 2 O 2 and vanadate was also evidenced suggesting that inhibition of tyrosine phosphatase(s)

Sequential activation of JAKs, STATs and xanthine dehydrogenase/oxidase by hypoxia in lung microvascular endothelial cells

“…It has been reported that hypoxia strongly activates the p38 MAPK and Rho kinase in rat pulmonary microvascular endothelial cells . Other studies have also demonstrated that peroxide treatment results in STAT3 tyrosine phosphorylation and nuclear translocation (Carballo et al, 1999]. These data suggest that hypoxia-induced tyrosine phosphorylation or activation of STATs in LMVEC may be mediated through multiple signaling pathways involving JAKs, p38 and PI3K.…”

Two Vicinal Cysteines Confer a Peculiar Redox Regulation to Low Molecular Weight Protein Tyrosine Phosphatase in Response to Platelet-derived Growth Factor Receptor Stimulation

“…It has been reported that the H 2 O 2 produced upon growth factor stimulation is really a cellular second messenger directly influencing many signal transducers such as the STAT proteins, p70 s6k, protein kinase D, and PTPs (33)(34)(35)(36). We have already demonstrated that LMW-PTP is a key regulator of PDGF-R phosphorylation upon recruitment to the membrane when cells are stimulated with the growth factor (5,6,10).…”

Critical role of PA28γ in hepatitis C virus-associated steatogenesis and hepatocarcinogenesis

“…Enhancement of ROS production may trigger double-stranded DNA breaks and result in the development of HCC (30,32,33). HCV core protein could enhance the protein carbonylation in the liver of the transgenic mice in the presence but not in the absence of PA28␥ (SI Fig.…”