Interferon-Dependent Activation of the Serine Kinase PI 3′-Kinase Requires Engagement of the IRS Pathway but Not the Stat Pathway (original) (raw)
Related papers
2000
Binding of interferon-a (IFN-a) to its receptor on hematopoi-Stat-1, Stat-2, and Stat-3 does not require the function of the IRS-system. Furthermore, THP-1 cells are responsive to etic cells activates the signal transducers and activators of transcription (Stat)-and insulin receptor substrate (IRS)-the protective effect of IFN-a against vesicular stomatitis virus. Both 32D and THP-1 cells were resistant to the growth pathways, and regulates expression of antiproliferative and antiviral activities. However, it remains unknown whether inhibitory effect of IFN-a, but this effect was not reversible by expression of IRS-1 or IRS-2 alone in 32D cells. Taken these two pathways cooperate in the generation of IFN-a responses or function independently, and whether IRS-pro-altogether these data show that: (1) The IRS-system transduces common and distinct signals in response to IFN-a or teins transduce distinct downstream signals in response to IFNs or insulin/insulin-like growth factor (IGF)-1-mediated insulin/IGF-1 stimulation of hematopoietic cells. (2) The IRSpathway operates separately from the Stat-pathway, and its activation. Our data show that in response to IFN-a treatment, IRS-1 functions selectively as a docking protein for function is not essential for the generation of the antiviral effect of IFN-a. (3) Neither the IRS-nor the Stat-pathways the SH2 domains of the p85 subunit of the PI 3-kinase, but not the SH2 domain of Grb-2 which is engaged during insu-alone are sufficient to mediate the antiproliferative effects of IFN-a in hematopoietic cells, and additional signaling ele-lin/IGF-1 signaling. In studies with THP-1 human myelomonocytic cells and 32D mouse myeloid cells, which are IRS-ments are required. ᭧ 1997 by The American Society of Hematology. defective, we found that the IFN-a-regulated activation of From the Section of Hematology-Oncology, Department of Mediduring insulin stimulation are phosphorylated and act as cine, University of Illinois at Chicago and West Side Veterans Affairs docking sites for the SH2 domains of the p85 regulatory
Dual Regulatory Roles of Phosphatidylinositol 3-Kinase in IFN Signaling
The Journal of Immunology, 2008
PI3K is activated by the type I and II IFN receptors, but its precise role in the generation of IFN responses is not well understood. In the present study we used embryonic fibroblasts from mice with targeted disruption of the genes encoding for both the p85␣ and p85 regulatory subunits of PI3-kinase (p85␣ ؊/؊  ؊/؊) to precisely define the role of PI3K in the control of IFN-induced biological responses. Our data demonstrate that PI3K plays dual regulatory roles in the induction of IFN responses by controlling both IFN-␣-and IFN-␥-dependent transcriptional regulation of IFN-sensitive genes and simultaneously regulating the subsequent initiation of mRNA translation for such genes. These processes include the Isg15, Cxcl10, and/or Irf7 genes, whose functions are important in the generation of the biological effects of IFNs. Consistent with this, the induction of IFN antiviral responses is defective in double p85␣/p85 knockout cells. Thus, integration of signals via PI3K is a critical event during engagement of the IFN receptors that complements both the transcriptional activity of Jak-STAT pathways and controls initiation of mRNA translation.
AKT activation and response to interferon-β in human cancer cells
Cancer Biology & Therapy, 2005
Significant growth inhibition and induction of apoptosis by IFN-β in cancer cells including colorectal cancer cells have been observed. We and others have previously reported the Stat 1 induction of TRAIL is a crucial step in the IFN-β induced apoptosis pathway. However, when evaluating the sensitivity of a panel of colorectal cancer cell lines, we found no clear correlation between activation of the Jak/Stat signaling pathway and response to interferon. In the present study, we have evaluated the interaction of the PI3k/Akt pathway and IFN-β induced apoptosis in human colorectal cancer cells. The results demonstrate a correlation between Akt activity, phosphorylation of Bad and resistance to interferon-induced apoptosis in these cells. The association of activation of Akt, phosphorylation of Bad and resistance to IFN-β-induced apoptosis was further supported by the observation that disruption of the pathway in a more resistant cell line led to sensitization, and expression of an activated Akt in a more sensitive cell line led to increased resistance. Taken together, this data indicates that the PI3/Akt kinase pathway may be an important contributor to IFN-β sensitivity and resistance in colorectal cancer cells. This data demonstrates a potential pathway by which cells may develop resistance to IFN, and further elucidation of this process may allow us to better target IFN therapy.
Role of IRS-4 in PI3-K activation by insulin in HepG2 cells, modulation by Angiotensin II
Regulatory Peptides, 2010
Insulin receptor substrate-4 (IRS-4) has a limited tissue expression and its modulation by tyr-phosphorylation is still controversial. We evaluated the participation of IRS-4 in the cross-talk between Angiotensin II (Ang II) and Insulin (Ins) receptors in HepG2 cells. Ins (10− 7 M) induced tyr-phosphorylation of IRS-4 (maximal at 5 min), an effect potentiated by Ang II AT1 receptors. Phosphatydilinositol-3 kinase (PI3-K) inhibitors Wortmanin or LY294002 reduced Ang II effect on tyr-phosphorylation of IRS-4 to a level comparable to that of Ins alone. Physical association between IRS-4 substrate and PI3-K was demonstrated by co-immunoprecipitation. Recruitment of PI3-K by IRS-4 was induced by Ins (10− 7 M, 5 min) not by Ang II (10− 7 M) and this was inhibited by Wortmanin and LY294002. Ang II did not modify either the association or activation of PI3-K in immunocomplexes. The present data provide novel evidence of IRS-4 phosphorylation mediated by Ins, an effect modulated by Ang II. We report also Ins-induced PI3-K activation mediated by IRS-4. Our findings suggest a role for IRS-4 as a docking protein in the Ins signaling pathway that involves PI3-K association and activation. The present data suggest a possible participation of IRS-4 in cell proliferation Ins-induced.
Journal of Biological Chemistry, 2000
The p38 mitogen-activated protein (MAP) kinase is activated during engagement of the type I interferon (IFN) receptor and mediates signals essential for IFN␣dependent transcriptional activation via interferonstimulated 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 IFN␣-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 IFN␣-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 IFN␣-sensitive genes and generation of growth inhibitory responses.
I B kinase (IKK ) regulates the balance between type I and type II interferon responses
Proceedings of the National Academy of Sciences, 2011
Virus infection induces the production of type I and type II interferons (IFN-I and IFN-II), cytokines that mediate the antiviral response. IFN-I (IFN-α and IFN-β) induces the assembly of IFN-stimulated gene factor 3 (ISGF3), a multimeric transcriptional activation complex composed of STAT1, STAT2, and IFN regulatory factor 9. IFN-II (IFN-γ) induces the homodimerization of STAT1 to form the gamma-activated factor (GAF) complex. ISGF3 and GAF bind specifically to unique regulatory DNA sequences located upstream of IFN-I- and IFN-II-inducible genes, respectively, and activate the expression of distinct sets of antiviral genes. The balance between type I and type II IFN pathways plays a critical role in orchestrating the innate and adaptive immune systems. Here, we show that the phosphorylation of STAT1 by IκB kinase epsilon (IKKε) inhibits STAT1 homodimerization, and thus assembly of GAF, but does not disrupt ISGF3 formation. Therefore, virus and/or IFN-I activation of IKKε suppresses GAF-dependent transcription and promotes ISGF3-dependent transcription. In the absence of IKKε, GAF-dependent transcription is enhanced at the expense of ISGF3-mediated transcription, rendering cells less resistant to infection. We conclude that IKKε plays a critical role in regulating the balance between the IFN-I and IFN-II signaling pathways.
Journal of Biological Chemistry, 2004
Interferon (IFN) ␣ induces a caspase-dependent apoptosis that is associated with activation of the proapoptotic Bak and Bax, loss of mitochondrial membrane potential, and release of cytochrome c. In addition to the onset of the classical Jak-STAT pathway, IFN␣ also induced phosphoinositide 3-kinase (PI3K) activity. Pharmacological inhibition of PI3K activity by Ly294002 disrupted IFN-induced apoptosis upstream of mitochondria. Inhibition of mTOR by rapamycin or by overexpression of a kinase dead mutant of mTOR, efficiently blocked IFN␣-induced apoptosis. A PI3K and mTOR-dependent phosphorylation of p70S6 kinase and 4E-BP1 repressor was induced by IFN␣ treatment of cells and was strongly inhibited by Ly294002 or rapamycin. The activation of Jak-STAT signaling upon IFN␣ stimulation was not affected by abrogating PI3K/mTOR pathway. Neither was the expression of several IFN␣ target genes affected, nor the ability of IFN␣ to protect against virus-induced cell death affected by inhibition of the PI3K/mTOR pathway. These data demonstrate that an intact PI3K/ mTOR pathway is necessary for the ability of IFN␣ to induce apoptosis, whereas activation of the Jak-STAT pathway alone appears to be insufficient for this specific IFN␣-induced effect.
Embo Journal, 1999
Two distinct types of interferon, IFN-α/β and IFN-γ, commonly exhibit antiviral activities by transmitting signals to the interior of the cell via their homologous receptors. Receptor stimulation results in the activation of distinct combinations of Janus family protein tyrosine kinases (Jak PTKs); Jak1/Tyk2 and Jak1/Jak2 for IFN-α/β and IFN-γ, respectively. Jak PTK activation by these IFNs is commonly followed by tyrosine phosphorylation of the transcription factor Stat1 at Y701, which is essential for dimerization, translocation to the nucleus and DNA-binding activity. To gain full transcriptional activity, Stat1 also requires serine phosphorylation at S727. In this paper we demonstrate that Pyk2, which belongs to another PTK family, is critical for the Jak-mediated MAPK and Stat1 activation by IFN-γ, but not IFN-α. Pyk2 is selectively associated with Jak2 and activated by IFN-γ. Overexpression of PKM, a dominant interfering form of Pyk2, in NIH 3T3 cells results in a strong inhibition of the IFN-γ-induced activation of Erk2, serine phosphorylation of Stat1 and Stat1-dependent gene transcription. Finally, the antiviral action of IFN-γ, but not IFN-α, is severely impaired by PKM overexpression. Thus, the two types of IFN may utilize distinct Jak-mediated Erk2, and possibly other MAPK activation pathways for their antiviral action.