Regulation of S33/S37 phosphorylated beta-catenin in normal and transformed cells.
A novel phosphorylation-specific antibody (alphapbeta-catenin) was generated against a peptide corresponding to amino acids 33-45 of human beta-catenin, which contained phosphorylated serines at positions 33 and 37. This antibody is specific to phosphorylated beta-catenin and reacts neither with the non-phosphorylated protein nor with phosphorylated or non-phosphorylated plakoglobin. It weakly interacts ... with S33Y beta-catenin but not with the S37A mutant. pbeta-catenin is hardly detectable in normal cultured cells and accumulates (up to 55% of total beta-catenin) upon overexpression of the protein or after blocking its degradation by the proteasome. Inhibition of both GSK-3beta and the proteasome resulted in a rapid (t1/2=10 minutes) and reversible reduction in pbeta-catenin levels, suggesting that the protein can undergo dephosphorylation in live cells, at a rate comparable to its phosphorylation by GSK-3beta. pbeta-catenin interacts with LEF-1, but fails to form a ternary complex with DNA, suggesting that it is transcriptionally inactive. Immunofluorescence microscopy indicated that pbeta-catenin accumulates in the nuclei of MDCK and BCAP cells when overexpressed and is transiently associated with adherens junctions shortly after their formation. pbeta-catenin only weakly interacts with co-transfected N-cadherin, although it forms a complex with the ubiquitin ligase component beta-TrCP. SW480 colon cancer cells that express a truncated APC, at position 1338, contain high levels of pbeta-catenin, whereas HT29 cells, expressing APC truncated at position 1555, accumulate non-phosphorylated beta-catenin, suggesting that the 1338-1555 amino acid region of APC is involved in the differential regulation of the dephosphorylation and degradation of pbeta-catenin.
Mesh Terms:
Adenomatous Polyposis Coli Protein, Amino Acid Sequence, Animals, Cadherins, Carcinoma, Cattle, Cell Division, Cell Line, Transformed, Cell Transformation, Neoplastic, Colonic Neoplasms, Cysteine Endopeptidases, Cytoskeletal Proteins, DNA, DNA-Binding Proteins, GTP-Binding Proteins, Gene Expression Regulation, Neoplastic, Glycogen Synthase Kinase 3, Humans, Lymphoid Enhancer-Binding Factor 1, Mice, Mice, Inbred BALB C, Multienzyme Complexes, Phosphorylation, Proteasome Endopeptidase Complex, Rats, Serine, Trans-Activators, Transcription Factors, Tumor Cells, Cultured, Up-Regulation, beta Catenin, beta-Transducin Repeat-Containing Proteins
Adenomatous Polyposis Coli Protein, Amino Acid Sequence, Animals, Cadherins, Carcinoma, Cattle, Cell Division, Cell Line, Transformed, Cell Transformation, Neoplastic, Colonic Neoplasms, Cysteine Endopeptidases, Cytoskeletal Proteins, DNA, DNA-Binding Proteins, GTP-Binding Proteins, Gene Expression Regulation, Neoplastic, Glycogen Synthase Kinase 3, Humans, Lymphoid Enhancer-Binding Factor 1, Mice, Mice, Inbred BALB C, Multienzyme Complexes, Phosphorylation, Proteasome Endopeptidase Complex, Rats, Serine, Trans-Activators, Transcription Factors, Tumor Cells, Cultured, Up-Regulation, beta Catenin, beta-Transducin Repeat-Containing Proteins
J. Cell. Sci.
Date: Jul. 01, 2002
PubMed ID: 12077367
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