Regulation of phorbol ester-mediated TRAF1 induction in human colon cancer cells through a PKC/RAF/ERK/NF-κB-dependent pathway

Xiaofu Wang, Qingding Wang, Wanqin Hu, B. Mark Evers

Research output: Contribution to journalArticlepeer-review

76 Scopus citations

Abstract

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are cytoplasmic adapter proteins that link a wide variety of cell surface receptors to the apoptotic signaling cascade. The purpose of this study was to delineate the signaling pathways and TRAF1 promoter elements responsible for phorbol ester-mediated TRAF1 induction in human colon cancers. Here, we found that the PKC activators, phorbol 12-myristate 13-acetate (PMA) and bryostatin I, induced TRAF1 mRNA expression; pretreatment with actinomycin D blocked PMA-mediated TRAF1 expression suggesting induction at the transcriptional level. In contrast, expression of other TRAFs (TRAF2, 3 and 4) was minimally altered by PMA. Various PKC isoform-selective inhibitors blocked PMA-mediated TRAF1 mRNA and promoter stimulation; rottlerin, a selective PKCδ inhibitor, had no effect suggesting that Ca2+-dependent PKC isoforms (e.g., PKCα and βI) play a role in TRAF1 regulation. In addition, the MEK/ERK inhibitors, PD98059 and UO126, suppressed PMA-stimulated TRAF1 promoter activity indicating a role for ERK in TRAF1 induction. Moreover, cotransfection of a dominant-negative Raf-1 (Raf-C4) significantly reduced PMA-stimulated TRAF1 promoter activity whereas transfection of dominant-negative Ras or treatment with Ras inhibitors had minimal to no effect on TRAF1 induction suggesting dependence on Raf, but not Ras, activation. Finally, site-specific mutagenesis of functional NF-κB sites (particularly the most proximal site) in the TRAF1 promoter significantly decreased PMA-mediated promoter activity. In conclusion, our results demonstrate selective induction of TRAF1 in human colon cancer cells through a Ca2+ -dependent PKC/Raf-1/ERK/NF-κB-dependent pathway.

Original languageEnglish
Pages (from-to)1885-1895
Number of pages11
JournalOncogene
Volume23
Issue number10
DOIs
StatePublished - Mar 11 2004

Bibliographical note

Funding Information:
We thank Eileen Figueroa, Mary Lou Mraz and Karen Martin for manuscript preparation. We also thank Drs Mark Hellmich and Kathleen O’Connor and members of the Evers laboratory for helpful comments and discussion. This work was supported by Grants RO1 DK48498 and PO1 DK35408 from the National Institutes of Health.

Keywords

  • Colon cancer
  • ERK
  • NF-κB
  • PKC
  • TRAF

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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