The Keap1 BTB/POZ Dimerization Function Is Required to Sequester Nrf2 in Cytoplasm

Abstract

Transactivation of phase II detoxification enzymes and antioxidant proteins is mediated by the Cap'NCollar transcription factor, Nrf2, which is sequestered in the cytoplasm by the actin-binding protein Keap1. Mutation of a conserved serine (S104A) within the Keap1 BTB/POZ domain disrupts Keap1 dimerization and eliminates the ability of Keap1 to sequester Nrf2 in the cytoplasm and repress Nrf2 transactivation. Disruption of endogenous Keap1 dimerization using BTB/POZ dominant negative proteins also inhibits the ability of Keap1 to retain Nrf2 in the cytoplasm. Exposure to an electrophilic agent that induces Nrf2 release and nuclear translocation disrupts formation of a Keap1 complex in vivo. Collectively, these data support the conclusion that Keap1 dimerization is required for Nrf2 sequestration and transcriptional repression. Furthermore, exposure to inducing agents disrupts the Keap1 dimerization function and results in Nrf2 release.

Phosphorylation of Nrf2 in the transcription activation domain by casein kinase 2 (CK2) is critical for the nuclear translocation and transcription activation function of Nrf2 in IMR‐32 neuroblastoma cells

“…Keap1 has been reported to inhibit Nrf2 by binding and sequestrating Nrf2 in the cytoplasm [25] and by targeting Nrf2 to the ubiquitin 26S proteasome degradation pathway [26]. Thus inhibition of the 26S proteasome pathway by MG132 leads to accumulation of the Nrf2 protein as shown in Figures 1 and 4.…”

Flunarizine induces Nrf2-mediated transcriptional activation of heme oxygenase-1 in protection of auditory cells from cisplatin

“…Inactive Nrf 2 is localized in the cytoplasm, in part or totally, as a consequence of binding to cytoskeleton-associated protein, Keap1. 31 Recently, it has also been reported that MAP kinases, including ERKs, JNKs, and p38, are implicated in phosphorylation and stabilization of Nrf2 to facilitate its nuclear translocation 32 and binding to distinct but very similar DNA elements, individually or alternatively referred to as Maf recognition element (MARE), 33 stress-response element (StRE), 29 or antioxidant-response element (ARE). 34 In addition, PI3K/Akt signaling pathway also regulates AREs activation via the nuclear translocation of Nrf2.…”

The Keap1–Nrf2 pathway: promising therapeutic target to counteract ROS-mediated damage in cancers and neurodegenerative diseases

“…It is the nearest homologue of the kelch protein of Drosophila, which binds to actin (Itoh et al 1999;Zipper and Mulcahy 2002). Keap1 acts as a substrate adapter protein for the E3 ubiquitin ligase complex formed by Cul3 and Rbx1 and targets Nf-E2/Nrf2 for ubiquitination and degradation by the proteasome (McMahon et al 2004;Bryan et al 2013) (Fig.…”