The Rac1/p38 Map kinase pathway is required for IFNα-dependent transcriptional activation but not serine phosphorylation of Stat-proteins

Toronto General Research Institute, University of Toronto, Toronto, Ontario, Canada
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2000; 275(36):27634-40. DOI: 10.1074/jbc.M003170200
Source: PubMed


The p38 mitogen-activated protein (MAP) kinase is activated during engagement of the type I interferon (IFN) receptor and mediates signals essential for IFNalpha-dependent transcriptional activation via interferon-stimulated response elements without affecting formation of the ISGF3 complex. In the present study, we provide evidence that the small GTPase Rac1 is activated in a type I IFN-dependent manner and that its function is required for downstream engagement of the p38 MAP kinase pathway. We also demonstrate that p38 is required for IFNalpha-dependent gene transcription via GAS elements and regulates activation of the promoter of the PML gene that mediates growth inhibitory responses. In studies to determine whether the regulatory effects of p38 are mediated by serine phosphorylation of Stat1 or Stat3, we found that the p38 kinase inhibitors SB203580 or SB202190 or overexpression of a dominant negative p38 mutant do not inhibit phosphorylation of Stat1 or Stat3 on Ser-727 in several IFNalpha-sensitive cell lines. Altogether these data demonstrate that the Rac1/p38 MAP kinase signaling cascade plays a critical role in type I IFN signaling, functioning in cooperation with the Stat-pathway, to regulate transcriptional regulation of IFNalpha-sensitive genes and generation of growth inhibitory responses.

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Available from: Peter R Young, May 02, 2015
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    • "In spite of these findings, some studies performed with diverse leukemia cell lines [27] [31] and dendritic cell precursors [32] have established that IFNα-induced Ser727 STAT1 phosphorylation would be independent of p38 activation. These controversial results may reflect a difference in the cell type studied. "
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    ABSTRACT: We have previously demonstrated that tyrosine phosphorylation of STAT1/3 and p38 mitogen-activated protein kinase (p38 MAPK) activation are involved in the apoptotic response triggered by a chimeric cyclic peptide of the interferon-α2b (IFN-α2b) in WISH cells. Since the peptide also induced serine phosphorylation of STAT proteins, in the present study we examined the kinase involved in serine STAT1 phosphorylation and the signaling effectors acting upstream such activation. We first found that p38 MAPK is involved in serine STAT1 phosphorylation, since a reduction of phophoserine-STAT1 levels was evident after incubating WISH cells with cyclic peptide in the presence of a p38 pharmacological inhibitor or a dominant-negative p38 mutant. Next, we demonstrated that the peptide induced activation of protein kinase Cδ (PKCδ). Based on this finding, the role of this kinase was then evaluated. After incubating WISH cells with a PKCδ inhibitor or after decreasing PKCδ expression levels by RNA interference, both peptide-induced serine STAT1 and p38 phosphorylation levels were significantly decreased, indicating that PKCδ functions as an upstream regulator of p38. We also showed that PKCδ and p38 activation stimulated by the peptide was inhibited by a specific pharmacological inhibitor of phosphatidylinositol 3-kinase (PI3K) or by a dominant-negative p85 PI3K-regulatory subunit, suggesting that PI3K is upstream in the signaling cascade. In addition, the role of PI3K and PKCδ in cyclic peptide-induced apoptosis was examined. Both signaling effectors were found to regulate the antiproliferative activity and the apoptotic response triggered by the cyclic peptide in WISH cells. In conclusion, we herein demonstrated that STAT1 serine phosphorylation is mediated by the sequential activation of PI3K, PKCδ and p38 MAPK. This signaling cascade contributes to the antitumor effect induced by the chimeric IFN-α2b cyclic peptide in WISH cells.
    Full-text · Article · Apr 2013 · Experimental Cell Research
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    • "Inhibition of p38 MAP kinase has no effects on the phosphorylation of STAT1 or -2, and formation of the ISGF3 transcriptional complex (Uddin et al., 1999; Platanias et al., 2005). In addition, Type II IFN (IFN gamma) did not activate p38 MAP kinase in several cell lines (Katsoulidis et al., 2005; Uddin et al., 2000). Further, in the bovine uterus, IFNT activates the p38 MAP kinase pathway for induction of PTGS2 in myometrial cells (Doualla-Bell and Koromilas, 2001). "
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    ABSTRACT: The peri-implantation period in mammals is critical with respect to survival of the conceptus (embryo/fetus and associated extraembryonic membranes) and establishment of pregnancy. During this period of pregnancy, reciprocal communication between ovary, conceptus, and endometrium is required for successful implantation and placentation. At this time, interferon tau (IFNT) is synthesized and secreted by the mononuclear trophectodermal cells of the conceptus between days 10 and 21~25. The actions of IFNT to signal pregnancy recognition and induce or increase expression of IFNT-stimulated genes (ISGs), such as ISG15 and OAS, are mediated by the Type I IFN signal transduction pathway. This article reviews the history, signaling pathways of IFNT and the uterine expression of several IFNT-stimulated genes during the peri-implantation period. Collectively, these newly identified genes are believed to be critical to unraveling the mechanism(s) of reciprocal fetal-maternal interactions required for successful implantation and pregnancy.
    Full-text · Article · Dec 2009
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    • "It has been reported that several STAT proteins require serine phosphorylation to regulate a full transcription activity [26] [27] [28]. Concerning IFN action, it has been proposed that p38 MAPK could function as a serine kinase for STAT1 in HeLa cells stimulated with IFNα and IFNγ [45], while other reports rendered opposite results in other cell types [46] [47]. Later, it was demonstrated that a member of the protein kinase C (PKC) family of proteins, PKCδ, mediates serine phosphorylation of STAT1 and behaves as an upstream regulator of p38 MAPK [48] [49]. "
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    ABSTRACT: In the search of mimetic peptides of the interferon-alpha2b molecule (IFN-alpha2b), we have previously designed and synthesized a chimeric cyclic peptide of the IFN-alpha2b that inhibits WISH cell proliferation by inducing an apoptotic response. Here, we first studied the ability of this peptide to activate intracellular signaling pathways and then evaluated the participation of some signals in the induction of apoptosis. Stimulation of WISH cells with the cyclic peptide showed tyrosine phosphorylation of Jak1 and Tyk2 kinases, tyrosine and serine phosphorylation of STAT1 and STAT3 transcription factors and activation of p38 MAPK pathway, although phosphorylation levels or kinetics were in some conditions different to those obtained under IFN-alpha2b stimulus. JNK and p44/42 pathways were not activated by the peptide in WISH cells. We also showed that STAT1 and STAT3 downregulation by RNA interference decreased the antiproliferative activity and the amount of apoptotic cells induced by the peptide. Pharmacological inhibition of p38 MAPK also reduced the peptide growth inhibitory activity and the apoptotic effect. Thus, we demonstrated that the cyclic peptide regulates WISH cell proliferation through the activation of Jak/STAT signaling pathway. In addition, our results indicate that p38 MAPK may also be involved in cell growth regulation. This study suggests that STAT1, STAT3 and p38 MAPK would be mediating the antitumor and apoptotic response triggered by the cyclic peptide in WISH cells.
    Full-text · Article · Nov 2009 · Experimental Cell Research
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