title: Tpl-2 kinase downregulates the activity of p53 and enhances signaling pathways leading to activation of activator protein 1 induced by EGF.
abstract: Tumor progression locus-2 (Tpl-2) kinase is a member of the mitogen-activated protein kinase kinase kinase family that has been implicated in cellular transformation. The enhanced expression of this protein has been shown to activate both the mitogen-activated protein kinase and c-Jun N-terminal kinase pathways. However, the molecular mechanisms responsible for the oncogenic potential of Tpl-2 are still largely unknown. Here, we showed that Tpl-2 interacted with p53 both in vitro and ex vivo. The overexpression of Tpl-2 inhibited the epidermal growth factor (EGF)-induced p53 phosphorylation (Ser15) through upregulating the activity of protein phosphatase 2A, which interacted with p53 stimulated by EGF. Also, the EGF-induced p53 activity was suppressed in the Tpl-2 wild-type (WT)-transfected HEK 293 cells, but had no effect in the Tpl-2-mutant (S413A)-transfected cells. Furthermore, introduction of small interfering RNA-Tpl-2 into HEK 293 cells resulted in decreased cell viability compared with only adenovirus-p53-infected cells. In addition, the Tpl-2 WT, but not Tpl-2 mutant (S413A), showed increased EGF-induced c-fos promoter activity, followed by activator protein 1 (AP-1) transactivation activity, which was associated with the cell transformation prompted by the H-Ras-Tpl-2-AP-1 signaling axis. These results indicated that the Ser413 of Tpl-2 plays an important role in EGF-induced carcinogenesis as well as inactivation of the p53.
authors.affiliation: College of Pharmacy, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759, South Korea.
authors.forename: Prem
authors.initials: P
authors.lastname: Khanal
authors.forename: Kwang-Youl
authors.initials: KY
authors.lastname: Lee
authors.forename: Keon-Wook
authors.initials: KW
authors.lastname: Kang
authors.forename: Bong Seok
authors.initials: BS
authors.lastname: Kang
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Choi
mesh_terms: D000256:Adenoviridae; D000818:Animals; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D015536:Down-Regulation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D011905:Genes, ras / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D007668:Kidney; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D016159:Tumor Suppressor Protein p53; D004815:Epidermal Growth Factor; D020930:MAP Kinase Kinase Kinases; C069937:MAP3K8 protein, human; C489843:Map3k8 protein, mouse; D054648:Protein Phosphatase 2