Regulation of transcription factor Nrf2 (NF-E2-related factor 2) involves redox-sensitive proteasomal degradation via the E3 ubiquitin ligase Keap1/Cul3. However, Nrf2 is controlled by other mechanisms that have not yet been elucidated. We now show that glycogen synthase kinase 3 (GSK-3) phosphorylates a group of Ser residues in the Neh6 domain of mouse Nrf2 that overlap with an SCF/ß-TrCP destruction motif (DSGIS, residues 334 to 338) and promotes its degradation in a Keap1-independent manner. Nrf2 was stabilized by GSK-3 inhibitors in Keap1-null mouse embryo fibroblasts. Similarly, an Nrf2(?ETGE) mutant, which cannot be degraded via Keap1, accumulated when GSK-3 activity was blocked. Phosphorylation of a Ser cluster in the Neh6 domain of Nrf2 stimulated its degradation because a mutant Nrf2(?ETGE 6S/6A) protein, lacking these Ser residues, exhibited a longer half-life than Nrf2(?ETGE). Moreover, Nrf2(?ETGE 6S/6A) was insensitive to ß-TrCP regulation and exhibited lower levels of ubiquitination than Nrf2(?ETGE). GSK-3ß enhanced ubiquitination of Nrf2(?ETGE) but not that of Nrf2(?ETGE 6S/6A). The Nrf2(?ETGE) protein but not Nrf2(?ETGE 6S/6A) coimmunoprecipitated with ß-TrCP, and this association was enhanced by GSK-3ß. Our results show for the first time that Nrf2 is targeted by GSK-3 for SCF/ß-TrCP-dependent degradation. We propose a "dual degradation" model to describe the regulation of Nrf2 under different pathophysiological conditions.