Regulation of S33/S37 phosphorylated β-catenin in normal and transformed cells

Einat Sadot, Maralice Conacci-Sorrell, Jacob Zhurinsky, Dalia Zhnizer, Zeev Lando, Dorit Zharhary, Zvi Kam, Avri Ben-Ze'ev, Benjamin Geiger

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Abstract

A novel phosphorylation-specific antibody (αpβ-catenin) was generated against a peptide corresponding to amino acids 33-45 of human β-catenin, which contained phosphorylated serines at positions 33 and 37. This antibody is specific to phosphorylated β-catenin and reacts neither with the non-phosphorylated protein nor with phosphorylated or non-phosphorylated plakoglobin. It weakly interacts with S33Y β-catenin but not with the S37A mutant. pβ-catenin is hardly detectable in normal cultured cells and accumulates (up to 55% of total β-catenin) upon overexpression of the protein or after blocking its degradation by the proteasome. Inhibition of both GSK-3β and the proteasome resulted in a rapid (t1/2=10 minutes) and reversible reduction in pβ-catenin levels, suggesting that the protein can undergo dephosphorylation in live cells, at a rate comparable to its phosphorylation by GSK-3β. pβ-catenin interacts with LEF-1, but fails to form a ternary complex with DNA, suggesting that it is transcriptionally inactive. Immunofluorescence microscopy indicated that pβ-catenin accumulates in the nuclei of MDCK and BCAP cells when overexpressed and is transiently associated with adherens junctions shortly after their formation. pβ-catenin only weakly interacts with co-transfected N-cadherin, although it forms a complex with the ubiquitin ligase component β-TrCP. SW480 colon cancer cells that express a truncated APC, at position 1338, contain high levels of pβ-catenin, whereas HT29 cells, expressing APC truncated at position 1555, accumulate non-phosphorylated β-catenin, suggesting that the 1338-1555 amino acid region of APC is involved in the differential regulation of the dephosphorylation and degradation of pβ-catenin.

Original languageEnglish (US)
Pages (from-to)2771-2780
Number of pages10
JournalJournal of Cell Science
Volume115
Issue number13
Publication statusPublished - Jul 1 2002

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Keywords

  • β-catenin
  • APC
  • GSK-3β

ASJC Scopus subject areas

  • Cell Biology

Cite this

Sadot, E., Conacci-Sorrell, M., Zhurinsky, J., Zhnizer, D., Lando, Z., Zharhary, D., ... Geiger, B. (2002). Regulation of S33/S37 phosphorylated β-catenin in normal and transformed cells. Journal of Cell Science, 115(13), 2771-2780.