The Axin1 scaffold protein promotes formation of a degradation complex for c-Myc

Hugh K. Arnold, Xiaoli Zhang, Colin J. Daniel, Deanne Tibbitts, Julie Escamilla-Powers, Amy Farrell, Sara Tokarz, Charlie Morgan, Rosalie C. Sears

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

Expression of the c-Myc proto-oncoprotein is tightly regulated in normal cells. Phosphorylation at two conserved residues, threonine58 (T58) and serine62 (S62), regulates c-Myc protein stability. In cancer cells, c-Myc can become aberrantly stabilized associated with altered T58 and S62 phosphorylation. A complex signalling cascade involving GSK3β kinase, the Pin1 prolyl isomerase, and the PP2A-B56α phosphatase controls phosphorylation at these sites. We report here a novel role for the tumour suppressor scaffold protein Axin1 in facilitating the formation of a degradation complex for c-Myc containing GSK3β, Pin1, and PP2A-B56α. Although knockdown of Axin1 decreases the association of c-Myc with these proteins, reduces T58 and enhances S62 phosphorylation, and increases c-Myc stability, acute expression of Axin1 reduces c-Myc levels and suppresses c-Myc transcriptional activity. Moreover, the regulation of c-Myc by Axin1 is impaired in several tested cancer cell lines with known stabilization of c-Myc or loss of Axin1. This study provides critical insight into the regulation of c-Myc expression, how this can be disrupted in three cancer types, and adds to our knowledge of the tumour suppressor activity of Axin1.

Original languageEnglish (US)
Pages (from-to)500-512
Number of pages13
JournalEMBO Journal
Volume28
Issue number5
DOIs
StatePublished - Mar 4 2009

Keywords

  • Axin1
  • GSK3β
  • PP2A-B56α
  • Pin1
  • c-Myc

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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  • Cite this

    Arnold, H. K., Zhang, X., Daniel, C. J., Tibbitts, D., Escamilla-Powers, J., Farrell, A., Tokarz, S., Morgan, C., & Sears, R. C. (2009). The Axin1 scaffold protein promotes formation of a degradation complex for c-Myc. EMBO Journal, 28(5), 500-512. https://doi.org/10.1038/emboj.2008.279