MAPK-induced Ser727 phosphorylation promotes sumoylation of STAT1

Institute of Medical Technology, University of Tampere, FIN-33014 Tampere, Finland.
Biochemical Journal (Impact Factor: 4.4). 02/2008; 409(1):179-85. DOI: 10.1042/BJ20070620
Source: PubMed


STAT1 (signal transducer and activator of transcription 1) is a critical mediator of IFN-gamma (interferon-gamma)-induced gene responses, and its function is regulated through phosphorylation of Tyr701 and Ser727. MAPK (mitogen-activated protein kinase) pathways mediate phosphorylation of Ser727 in response to microbial infections, stress stimuli and growth factors. Recently, STAT1 was found to become modified by PIAS (protein inhibitor of activated STAT)-mediated SUMO-1 (small ubiquitin-related modifier-1) conjugation at Lys703, but the regulation of this modification is largely unknown. Here, we have investigated the role of MAPK-induced Ser727 phosphorylation in regulation of STAT1 SUMOylation. Activation of the p38MAPK pathway by upstream activating kinase, MKK6 (MAPK kinase-6) or osmotic stress enhanced the SUMOylation of STAT1, which was counteracted by the p38MAPK inhibitor SB202190 or by dominant-negative p38MAPK. Activation of the ERK1/2 (extracellular-signal-regulated kinase 1/2) pathway by Raf-1 also enhanced Ser727 phosphorylation and SUMOylation of STAT1, and this induction was counteracted by PD98059 inhibitor. Mutation of Ser727 to alanine abolished the p38MAPK-induced SUMOylation. Furthermore, S727D and S727E mutations, which mimic the phosphorylation of Ser727, enhanced the basal SUMOylation of STAT1 and interaction between PIAS1 and STAT1. Taken together, these results identify Ser727 phosphorylation as a regulator of STAT1 SUMOylation and highlight the central role of Ser727 in co-ordination of STAT1 functions in cellular responses.

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Available from: Olli Silvennoinen, Apr 09, 2014
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    • "Besides, there is accumulating evidence that p38 MAPK can also mediate the STAT1 Ser727 phosphorylation [48], [50]. This event would enhance PIAS1 (protein inhibitor of activated STAT1) binding and SUMO-1 (small ubiquitin-related modifier-1) conjugation to STAT1 [51]. PIAS are a family of proteins implicated in the inhibition of STAT-mediated gene activation through many mechanisms, such as inhibiting DNA binding and promoting SUMO conjugation of STAT1 [40]. "
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    ABSTRACT: Background Many advances have been recently made focused on the valuable help of dietary polyphenols in chronic inflammatory diseases. On the other hand, current treatment options for intestinal bowel disease patients are unsatisfying and, for this reason, it is estimated that many patients use dietary supplements to achieve extra benefits. Aim The aim of this work was to analyze under a mechanistic perspective the anti-inflammatory potential of resveratrol, a natural polyphenolic compound, and to compare it with a pharmaceutical agent, 5-aminosalicylic acid, using the intestinal HT-29 cell line, as a cellular model. Methodology and Principal Findings In the present study, HT-29 colon epithelial cells were pre-treated with 25 µM resveratrol and/or 500 µM 5-aminosalicylic acid and then exposed to a combination of cytokines (IL-1α, TNF-α, IFN-γ) for a certain period of time. Our data showed that resveratrol, used in a concentration 20 times lower than 5-aminosalicylic acid, was able to significantly reduce NO and PGE2 production, iNOS and COX-2 expression and reactive oxidant species formation induced by the cytokine challenge. However, as already verified with 5-aminosalicylic acid, in spite of not exhibiting any effect on IkB-α degradation, resveratrol down-regulated JAK-STAT pathway, decreasing the levels of activated STAT1 in the nucleus. Additionally, resveratrol decreased the cytokine-stimulated activation of SAPK/JNK pathway but did not counteract the cytokine-triggered negative feedback mechanism of STAT1, through p38 MAPK. Conclusion/Significance Taken together, our results show that resveratrol may be considered a future nutraceutical approach, promoting remission periods, limiting the inflammatory process and preventing colorectal cancer, which is common in these patients.
    Full-text · Article · Oct 2014 · PLoS ONE
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    • "U3A cells were transfected either with HA-tagged STAT1 WT or STAT1 E705Q or STAT1 Y701F mutants together with His-tagged SUMO-1. Cells were left unstimulated or treated with IFN-γ and osmotic shock to induce STAT1 Tyr701 phosphorylation and STAT1 sumoylation, respectively [12]. STAT1 WT and the STAT1 mutants were oligoprecipitated from the whole cell lysates and the phosphorylation of STAT1 was detected with anti-pSTAT1 antibody. "
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    ABSTRACT: Background STAT1 is an essential transcription factor for interferon-γ-mediated gene responses. A distinct sumoylation consensus site (ψKxE) 702IKTE705 is localized in the C-terminal region of STAT1, where Lys703 is a target for PIAS-induced SUMO modification. Several studies indicate that sumoylation has an inhibitory role on STAT1-mediated gene expression but the molecular mechanisms are not fully understood. Results Here, we have performed a structural and functional analysis of sumoylation in STAT1. We show that deconjugation of SUMO by SENP1 enhances the transcriptional activity of STAT1, confirming a negative regulatory effect of sumoylation on STAT1 activity. Inspection of molecular model indicated that consensus site is well exposed to SUMO-conjugation in STAT1 homodimer and that the conjugated SUMO moiety is directed towards DNA, thus able to form a sterical hindrance affecting promoter binding of dimeric STAT1. In addition, oligoprecipitation experiments indicated that sumoylation deficient STAT1 E705Q mutant has higher DNA-binding activity on STAT1 responsive gene promoters than wild-type STAT1. Furthermore, sumoylation deficient STAT1 E705Q mutant displayed enhanced histone H4 acetylation on interferon-γ-responsive promoter compared to wild-type STAT1. Conclusions Our results suggest that sumoylation participates in regulation of STAT1 responses by modulating DNA-binding properties of STAT1.
    Full-text · Article · Oct 2012 · BMC Biochemistry
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    • "Many SUMO substrates have a highly conserved motif containing a SUMO consensus site and a proline-directed phosphorylation site (ΨKxExxSP), implying possible phosphorylation-dependent SUMO modification (PDSM) [18]. However, there have been several reports showing that cross talk between phosphorylation and SUMOylation of substrates does not rely on such a motif [26], [27]. Importantly, p45 contains a Ser-169 PKA recognition site and a Lys-368 SUMOylation site. "
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    Full-text · Article · Sep 2012 · PLoS ONE
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