GSK-3β regulates cell growth, migration, and angiogenesis via Fbw7 and USP28-dependent degradation of HIF-1α

The hypoxia-inducible transcription factor-1 alpha (HIF-1 alpha) is a major regulator of angiogenesis, carcinogenesis, and various processes by which cells adapt to hypoxic conditions. Therefore, the identification of critical players regulating HIF-1 alpha is not only important for the understanding of angiogenesis and different cancer phenotypes, but also for unraveling new therapeutic options. We report a novel mechanism by which HIF-1 alpha is degraded after glycogen synthase kinase-3 (GSK-3)-induced phosphorylation and recruitment of the ubiquitin ligase and tumor suppressor F-box and WD protein Fbw7. Further, experiments with GSK-3 beta and Fbw7-deficient cells revealed that GSK-3 beta and Fbw7-dependent HIF-1 alpha degradation can be antagonized by ubiquitin-specific protease 28 (USP28). In agreement with this, Fbw7 and USP28 reciprocally regulated cell migration and angiogenesis in an HIF-1 alpha-dependent manner. Therefore, we have identified a new pathway that could be targeted at the level of GSK-3, Fbw7, or USP28 to influence HIF-1 alpha-dependent processes like angiogenesis and metastasis. (Blood. 2012;119(5): 1292-1301)