12 research outputs found
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Inhibition of Cell Migration by PITENINs: The Role of ARF6
We have previously reported the development of small molecule phosphatidylinositol-3,4,5-trisphosphate (PIP3) antagonists (PITs) that block pleckstrin homology (PH) domain interaction, including activation of Akt, and show anti-tumor potential. Here we show that the same molecules inhibit growth factor-induced actin remodeling, lamellipodia formation and, ultimately, cell migration and invasion, consistent with an important role of PIP3 in these processes. In vivo, a PIT-1 analog displays significant inhibition on tumor angiogenesis and metastasis. ADP ribosylation factor 6 (ARF6) was recently identified as an important mediator of cytoskeleton and cell motility, which is regulated by PIP3-dependent membrane translocation of the guanine nucleotide exchange factors (GEFs) such as ADP-ribosylation factor nucleotide binding-site opener (ARNO) and general receptor for 3-phosphoinositides (GRP1). We demonstrate that PITs inhibit PIP3/ARNO or GRP1 PH domain binding and membrane localization, resulting in the inhibition of ARF6 activation. Importantly, we show that expression of the constitutively active mutant of Arf6 attenuates inhibition of lamellipodia formation and cell migration by PITs, confirming that inhibition of Arf6 contributes to inhibition of these processes by PITs. Overall, our studies demonstrate the feasibility of developing specific small molecule targeting PIP3 binding by PH domains as potential anti-cancer agents that can simultaneously interfere with cancer development at multiple points
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Akt Regulates TNFα Synthesis Downstream of RIP1 Kinase Activation during Necroptosis
Necroptosis is a regulated form of necrotic cell death that has been implicated in the pathogenesis of various diseases including intestinal inflammation and systemic inflammatory response syndrome (SIRS). In this work, we investigated the signaling mechanisms controlled by the necroptosis mediator receptor interacting protein-1 (RIP1) kinase. We show that Akt kinase activity is critical for necroptosis in L929 cells and plays a key role in TNFα production. During necroptosis, Akt is activated in a RIP1 dependent fashion through its phosphorylation on Thr308. In L929 cells, this activation requires independent signaling inputs from both growth factors and RIP1. Akt controls necroptosis through downstream targeting of mammalian Target of Rapamycin complex 1 (mTORC1). Akt activity, mediated in part through mTORC1, links RIP1 to JNK activation and autocrine production of TNFα. In other cell types, such as mouse lung fibroblasts and macrophages, Akt exhibited control over necroptosis-associated TNFα production without contributing to cell death. Overall, our results provide new insights into the mechanism of necroptosis and the role of Akt kinase in both cell death and inflammatory regulation
Akt Regulates TNF? Synthesis Downstream of RIP1 Kinase Activation during Necroptosis
Necroptosis is a regulated form of necrotic cell death that has been implicated in the pathogenesis of various diseases including intestinal inflammation and systemic inflammatory response syndrome (SIRS). In this work, we investigated the signaling mechanisms controlled by the necroptosis mediator receptor interacting protein-1 (RIP1) kinase. We show that Akt kinase activity is critical for necroptosis in L929 cells and plays a key role in TNF? production. During necroptosis, Akt is activated in a RIP1 dependent fashion through its phosphorylation on Thr308. In L929 cells, this activation requires independent signaling inputs from both growth factors and RIP1. Akt controls necroptosis through downstream targeting of mammalian Target of Rapamycin complex 1 (mTORC1). Akt activity, mediated in part through mTORC1, links RIP1 to JNK activation and autocrine production of TNF?. In other cell types, such as mouse lung fibroblasts and macrophages, Akt exhibited control over necroptosis-associated TNF? production without contributing to cell death. Overall, our results provide new insights into the mechanism of necroptosis and the role of Akt kinase in both cell death and inflammatory regulation
In vitro cytotoxicity of novel pro-apoptotic agent DM-PIT-1 in PEG-PE-based micelles alone and in combination with TRAIL
A HPLC method for the quantitative determination of N-(2-hydroxy-5-nitrophenylcarbamothioyl)-3,5-dimethylbenzamide in biological samples
Akt contributes to necroptosis induced by zVAD.fmk and TNFα.
<p>(A,B) Necroptosis was induced by zVAD.fmk or TNFα (full serum, A) or growth factors/zVAD.fmk (serum free, B) in the presence of inhibitors of Akt (Akt inhibitor VIII), JNK (SP600125), p38 (PD169316), and Erk (UO126). Cell viability was determined after 24 hrs. (C) L929 cells transfected with Akt1, Akt2, and Akt3 siRNAs for 72 hrs were treated with zVAD.fmk or TNFα for 9 hrs. Cell viability and Akt expression levels were determined after 24 hrs. In all graphs, average±SD was plotted.</p
RIP1 kinase-dependent phosphorylation of Akt and JNK during necroptosis.
<p>(A) L929 cells were treated with zVAD.fmk or TNFα for 9 hr, followed by western blotting with indicated antibodies. (B,C) L929 cells were treated with zVAD.fmk (B) or bFGF/zVAD.fmk (serum free conditions, C) and samples were collected at the indicated time points for western blot. (D) Nec-1 was added to the cells stimulated with bFGF or bFGF/zVAD (serum free conditions) for 15 min or 9 hr followed by western blot with the indicated antibodies.</p
bFGF and IGF-1 promote necroptosis in concert with zVAD.fmk.
<p>(A) L929 cells were treated with TNFα or zVAD.fmk under normal serum (10% FBS) or serum free conditions. Cell viability was determined after 24 hr using the CellTiter-Glo Viability assay. The concentrations of all necroptosis-inducing agents are listed in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056576#s4" target="_blank"><i>Materials and Methods</i></a> section or indicated in the figures. (B) Cells were treated with zVAD.fmk, the indicated growth factors, and Nec-1 under serum free conditions for 24 hrs followed by measurement of cell viability. (C) Cells under serum free conditions were treated with FGF, zVAD.fmk, or both for 24 hrs followed by viability assay. (D) Cell death was induced by zVAD.fmk or TNFα under full serum condition in the presence of 2 µM PD173074 and 20 µM PD166866. In all graphs, average±SD was plotted.</p
Late Thr308 phosphorylation of Akt contributes to necroptosis.
<p>(A) L929 cells were treated with zVAD.fmk and bFGF or PDGF, with or without Nec-1, for the indicated periods of time. (B,C) L929 cells were stimulated by zVAD.fmk or TNFα (B) or bFGF/zVAD.fmk under serum free conditions (C). Akt inh. VIII was added 15 min before necroptotic stimulation (Pre) or at indicated times after stimulation. Viability was measured 24 hr after activation of necroptosis. (D) L929 cells were stimulated with bFGF/zVAD under serum free conditions. PD173074 was added 15 min before or 1 hr after FGF/zVAD. Samples for western blot were collected at 15 min and 9 hr time points. (E) Cells were pretreated with PD173074 or it was added 1 hr after bFGF/zVAD.fmk, followed by viability assessment at 24 hr. In all graphs, average±SD was plotted.</p
mTORC1 contributes to the regulation of necroptosis.
<p>(A) L929 cells were treated with zVAD.fmk or TNFα for 9 hr and harvested for western blot. (B) Cell under serum free condition were treated with bFGF or bFGF/zVAD.fmk for the indicated amounts of time, followed by western blotting using the indicated antibodies. (C) Necroptosis was induced by zVAD.fmk or TNFα in L929 cell in the presence of inhibitors of Akt(Akt inh. VIII) and mTOR (rapamycin, Torin-1 and PI-103). (D) L929 cells with mTOR siRNA knockdown were harvested for western blot or treated with zVAD.fmk or TNFα for 24 hrs. Cell viability was determined 24 hr after activation of necroptosis. In all graphs, average±SD was plotted.</p