c-Src Is Required for Oxidative Stress-mediated Activation of Big Mitogen-activated Protein Kinase 1 (BMK1)

Jung

Journal of Biological Chemistry

et al. 2000

101

We have studied a possible role of extracellular zinc ion in the activation of p70S6k, which plays an important role in the progression of cells from the G 1 to S phase of the cell cycle. Treatment of Swiss 3T3 cells with zinc sulfate led to the activation and phosphorylation of p70S6k in a dose-dependent manner. The activation of p70S6k by zinc treatment was biphasic, the early phase being at 30 min followed by the late phase at 120 min. The zinc-induced activation of p70S6k was partially inhibited by down-regulation of phorbol 12-myristate 13-acetate-responsive protein kinase C (PKC) by chronic treatment with phorbol 12-myristate 13-acetate, but this was not significant. Moreover, Go6976, a specific calciumdependent PKC inhibitor, did not significantly inhibit the activation of p70S6k by zinc. These results demonstrate that the zinc-induced activation of p70S6k is not related to PKC. Also, extracellular calcium was not involved in the activation of p70S6k by zinc. Further characterization of the zinc-induced activation of p70S6k using specific inhibitors of the p70S6k signaling pathway, namely rapamycin, wortmannin, and LY294002, showed that zinc acted upstream of mTOR/FRAP/RAFT and phosphatidylinositol 3-kinase (PI3K), because these inhibitors caused the inhibition of zinc-induced p70S6k activity. In addition, Akt, the upstream component of p70S6k, was activated by zinc in a biphasic manner, as was p70S6k. Moreover, dominant interfering alleles of Akt and PDK1 blocked the zinc-induced activation of p70S6k, whereas the lipid kinase activity of PI3K was potently activated by zinc. Taken together, our data suggest that zinc activates p70S6k through the PI3K signaling pathway. p70 S6 kinase (p70S6k) 1 was originally recognized as the kinase that regulates the multiple phosphorylation of the 40 S ribosomal protein S6 in vivo (1-4). Physiological roles of the kinase have been sought using various molecular and pharmacological methods for the past decade. Most worth noting, the inhibition of agonist-induced p70S6k activation in vivo by either microinjecting neutralizing antibodies (5) or by treatment with the immunosuppressant rapamycin to the cell severely impairs the progression of the cell cycle through the G 1 phase (6 -8). This strongly supports that p70S6k plays important roles during cell growth in the G 1 to S cell cycle transition. Further emphasizing the importance of p70S6k at a molecular level is that the kinase is involved in the selective translational regulation of a unique family of mRNAs (9), presumably by mediating the multiple phosphorylation of 40 S ribosomal protein S6. These mRNAs encode for components of the translational apparatus, including ribosomal proteins and translational elongation factors whose increased expression is essential for cell growth and proliferation (10).Recently, Thomas' group (11) has shown that a mutant fly that has lost the p70S6k ortholog displays delayed growth and reduced cell and body size compared with those of the wild type fly. These genetic studies in Drosophil...

Section: Discussionmentioning

confidence: 99%

Extracellular Zinc Activates p70 S6 Kinase through the Phosphatidylinositol 3-Kinase Signaling Pathway

Jung

Journal of Biological Chemistry

et al. 2000

101

Journal of Biological Chemistry

“…Activation of SRC tyrosine kinases has been implicated in the signaling pathways induced by exogenously applied ROS (33)(34)(35). In human neutrophils, endogenous ROS are thought to play an important role in activating SRC tyrosine kinases (36).…”

Section: Discussionmentioning

confidence: 99%

Activation of SRC Tyrosine Kinases in Response to ICAM-1 Ligation in Pulmonary Microvascular Endothelial Cells

Wang

Pfeiffer

Gaarde

2003

Previous studies demonstrated that ICAM-1 ligation on human pulmonary microvascular endothelial cells (ECs) sequentially induces activation of xanthine oxidase and p38 MAPK. Inhibition of these signaling events reduces neutrophil migration to the EC borders. This study examined the role of SRC tyrosine kinases in ICAM-1-initiated signaling within these ECs. Cross-linking ICAM-1 on tumor necrosis factor-␣-pretreated ECs induced an increase in the activity of SRC tyrosine kinases. This increase was inhibited by allopurinol (a xanthine oxidase inhibitor), Me 2 SO (a hydroxyl radical scavenger), or deferoxamine (an iron chelator). Phenylarsine oxide, a tyrosine phosphatase inhibitor, reduced the base-line activity of SRC as well as the increase in SRC activity induced by ICAM-1 cross-linking. Specific inhibition of the protein expression of the SRC homology 2-containing protein-tyrosine phosphatase-2 (SHP-2) by an antisense oligonucleotide prevented the induced SRC activation but had no effect on the basal SRC activity. Activation of SRC tyrosine kinases was accompanied by tyrosine phosphorylation of ezrin at Tyr-146, which was inhibited by PP2, an SRC tyrosine kinase inhibitor. Moreover, PP2 completely inhibited p38 activation, suggesting a role for SRC tyrosine kinases in p38 activation. These data demonstrate that ICAM-1 ligation activates SRC tyrosine kinases and that this activation requires SHP-2 as well as production of reactive oxygen species generated from xanthine oxidase. Activation of SRC tyrosine kinases in turn leads to tyrosine phosphorylation of ezrin, as well as activation of p38, a kinase previously identified to be required for cytoskeletal changes induced by ICAM-1 ligation and for neutrophil migration along the EC surface.Recent studies have provided evidence that ligation of endothelial cell (EC) 1 adhesion molecules including ICAM-1 is capable of initiating outside-in signaling events into ECs upon leukocyte adhesion (reviewed in Refs. 1 and 2). ICAM-1-initiated signaling events into ECs play important roles in modulating neutrophil migration along and/or across endothelium during inflammatory responses. Sans et al. (3) demonstrated that deletion of the ICAM-1 cytoplasmic domain completely inhibits neutrophil transmigration, but not adhesion, in a reconstituted cell line, suggesting a role for ICAM-1-dependent outside-in signaling in mediating neutrophil migration. In addition, inhibition of ICAM-1-inititated signaling events in pulmonary microvascular ECs reduces neutrophil migration along the EC surface to reach EC borders (4).Within the signaling pathways induced through ligation of ICAM-1, activation of SRC tyrosine kinases has been demonstrated in human umbilical vein ECs and rat brain microvascular ECs (5-7). In addition, ligation of ICAM-1 induces activation of LYN, a member of the SRC family tyrosine kinases, in a B cell lymphoma line (8). Each member of the human SRC tyrosine kinase family is composed of a unique region, an SRC homology 2 and 3 domain, a catalytic domain containing r...

“…Therefore, we investigated the role of GDC during plant defense responses in vivo by monitoring the amino acid content in Arabidopsis leaves (Blackwell et al, 1990;Abe et al, 1997;Heineke et al, 2001). The concentration of harpin used was able to cause cell death after 24 h when infiltrated into Arabidopsis leaves, but not after 30 min (in vitro experiments; data not shown).…”

Section: Inhibition Of Gly Decarboxylase Activity By Harpinmentioning

confidence: 99%

Regulation of Plant Glycine Decarboxylase byS-Nitrosylation and Glutathionylation

et al. 2010

Mitochondria play an essential role in nitric oxide (NO) signal transduction in plants. Using the biotin-switch method in conjunction with nano-liquid chromatography and mass spectrometry, we identified 11 candidate proteins that were S-nitrosylated and/or glutathionylated in mitochondria of Arabidopsis (Arabidopsis thaliana) leaves. These included glycine decarboxylase complex (GDC), a key enzyme of the photorespiratory C 2 cycle in C3 plants. GDC activity was inhibited by S-nitrosoglutathione due to S-nitrosylation/S-glutathionylation of several cysteine residues. Gas-exchange measurements demonstrated that the bacterial elicitor harpin, a strong inducer of reactive oxygen species and NO, inhibits GDC activity. Furthermore, an inhibitor of GDC, aminoacetonitrile, was able to mimic mitochondrial depolarization, hydrogen peroxide production, and cell death in response to stress or harpin treatment of cultured Arabidopsis cells. These findings indicate that the mitochondrial photorespiratory system is involved in the regulation of NO signal transduction in Arabidopsis.