Dual regulation of Snail by GSK-3beta-mediated phosphorylation in control of epithelial-mesenchymal transition.
The phenotypic changes of increased motility and invasiveness of cancer cells are reminiscent of the epithelial-mesenchymal transition (EMT) that occurs during embryonic development. Snail, a zinc-finger transcription factor, triggers this process by repressing E-cadherin expression; however, the mechanisms that regulate Snail remain elusive. Here we find that Snail is highly unstable, with a short half-life about 25 min. We show that GSK-3beta binds to and phosphorylates Snail at two consensus motifs to dually regulate the function of this protein. Phosphorylation of the first motif regulates its beta-Trcp-mediated ubiquitination, whereas phosphorylation of the second motif controls its subcellular localization. A variant of Snail (Snail-6SA), which abolishes these phosphorylations, is much more stable and resides exclusively in the nucleus to induce EMT. Furthermore, inhibition of GSK-3beta results in the upregulation of Snail and downregulation of E-cadherin in vivo. Thus, Snail and GSK-3beta together function as a molecular switch for many signalling pathways that lead to EMT.
Pubmed ID: 15448698 RIS Download
Amino Acid Motifs | Binding Sites | Breast Neoplasms | Cadherins | Cell Line, Tumor | Cell Nucleus | Consensus Sequence | Cysteine Endopeptidases | DNA-Binding Proteins | Enzyme Inhibitors | Epithelial Cells | Gene Expression Regulation, Neoplastic | Glycogen Synthase Kinase 3 | Humans | Leupeptins | Lithium | Mesoderm | Multienzyme Complexes | Mutation | Phosphorylation | Proteasome Endopeptidase Complex | Protein Binding | Substrate Specificity | Transcription Factors | Zinc Fingers