國家衛生研究院 NHRI:Item 3990099045/2793
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    Please use this identifier to cite or link to this item: http://ir.nhri.org.tw/handle/3990099045/2793


    Title: Suppression of MEK/ERK signaling pathway enhances cisplatin-induced NF-kappa B activation by protein phosphatase 4-mediated NF-kappa B p65 Thr dephosphorylation
    Authors: Yeh, PY;Yeh, KH;Chuang, SE;Song, YC;Cheng, AL
    Contributors: National Institute of Cancer Research
    Abstract: 87We previously reported that suppression of the MEK/ERK pathway increases drug resistance of SiHa cells. In this study, we further characterized the underlying mechanism of this phenomenon. Pretreatment of SiHa cells with MEK/ERK inhibitor enhanced cisplatin-induced NF-kappaB activation. However, results of immunoblotting analysis showed that neither cisplatin nor MEK/ERK inhibitors induced marked IkappaBalpha degradation, suggesting that suppression of the MEK/ERK signaling pathway may enhance cisplatin-induced NF-kappaB activation via mechanisms other than the conventional pathway. Previous findings that protein phosphatase 4 (PP4), a nuclear serine/threonine phosphatase, directly interacts with and activates NF-kappaB led us to examine the phosphorylation status of NF-kappaB p65. Coincident with activation of NF-kappaB, cisplatin induced Ser phosphorylation but decreased Thr phosphorylation of NF-kappaB p65. Suppression of the MEK/ERK pathway further enhanced cisplatin-induced Thr dephosphorylation but did not affect cisplatin-induced Ser phosphorylation of NF-kappaB p65. Further, in parallel with Thr dephosphorylation, the protein level of nuclear PP4 was increased in cisplatin-treated cells and was further increased by suppression of the MEK/ERK pathway. SiHa cells were then transfected by a sense or an antisense PP4 gene. PP4-overexpressing cells showed a decrease in Thr phosphorylation of NF-kappaB p65 to nearly undetectable levels, and both basal and cisplatin-induced NF-kappaB activities were higher than those in parental cells. By contrast, cisplatin, either alone or with MEK/ERK inhibitors, induced little NF-kappaB activation in antisense PP4-transfected cells. Coprecipitated complex kinase assay revealed a fragment of NF-kappaB p65 (amino acids 279-444) to contain potential phosphorylation sites that directly interact with PP4. Further studies by site-directed mutagenesis suggested that Thr(435) was the major phosphorylation site.
    Keywords: Biochemistry & Molecular Biology
    Date: 2004-06-18
    Relation: Journal of Biological Chemistry. 2004 Jun;279(25):26143-26148.
    Link to: http://dx.doi.org/10.1074/jbc.M402362200
    JIF/Ranking 2023: http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=NHRI&SrcApp=NHRI_IR&KeyISSN=1083-351X&DestApp=IC2JCR
    Cited Times(WOS): https://www.webofscience.com/wos/woscc/full-record/WOS:000222003000028
    Cited Times(Scopus): http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=2942702021
    Appears in Collections:[Shuang-En Chuang] Periodical Articles

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