The Hypoxia-controlled FBXL14 Ubiquitin Ligase Targets SNAIL1 for Proteasome Degradation

• Published in: The Journal of biological chemistry Vol. 285; no. 6; pp. 3794 - 3805
• Main Authors: Viñas-Castells, Rosa, Beltran, Manuel, Valls, Gabriela, Gómez, Irene, García, José Miguel, Montserrat-Sentís, Bàrbara, Baulida, Josep, Bonilla, Félix, de Herreros, Antonio García, Díaz, Víctor M
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 05-02-2010
• Subjects: Animals; Binding Sites; Blotting, Western; Cell Hypoxia; Cell Line; Cell Line, Tumor; Down-Regulation; F-Box Proteins - genetics; F-Box Proteins - metabolism; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Immunoprecipitation; Mice; Mutation; NIH 3T3 Cells; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphorylation; Proteasome Endopeptidase Complex - metabolism; Protein Binding; Protein Synthesis, Post-Translational Modification, and Degradation; RNA Interference; Snail Family Transcription Factors; Transcription Factors - genetics; Transcription Factors - metabolism; Transfection; Twist-Related Protein 1 - genetics; Twist-Related Protein 1 - metabolism; Ubiquitin-Protein Ligases - genetics; Ubiquitin-Protein Ligases - metabolism; Ubiquitination
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.065995

The transcription factor SNAIL1 is a master regulator of epithelial to mesenchymal transition. SNAIL1 is a very unstable protein,
and its levels are regulated by the E3 ubiquitin ligase β-TrCP1 that interacts with SNAIL1 upon its phosphorylation by GSK-3β.
Here we show that SNAIL1 polyubiquitylation and degradation may occur in conditions precluding SNAIL1 phosphorylation by GSK-3β,
suggesting that additional E3 ligases participate in the control of SNAIL1 protein stability. In particular, we demonstrate
that the F-box E3 ubiquitin ligase FBXl14 interacts with SNAIL1 and promotes its ubiquitylation and proteasome degradation
independently of phosphorylation by GSK-3β. In vivo , inhibition of FBXl14 using short hairpin RNA stabilizes both ectopically expressed and endogenous SNAIL1. Moreover, the expression of FBXl14 is potently down-regulated during hypoxia, a condition that increases the levels of SNAIL1 protein but not SNAIL1 mRNA. FBXL14 mRNA is decreased in tumors with a high expression of two proteins up-regulated in hypoxia, carbonic anhydrase 9 and TWIST1.
In addition, Twist1 small interfering RNA prevents hypoxia-induced Fbxl14 down-regulation and SNAIL1 stabilization in NMuMG cells. Altogether, these results demonstrate the existence of an alternative
mechanism controlling SNAIL1 protein levels relevant for the induction of SNAIL1 during hypoxia.