The Ubiquitin-conjugating Enzyme UbcM2 Can Regulate the Stability and Activity of the Antioxidant Transcription Factor Nrf2

Abstract

The transcription factor nuclear factor E2-related factor 2 (Nrf2) induces the expression of antioxidant gene products that neutralize reactive oxygen species and restore redox homeostasis. Nrf2 is constitutively degraded by the ubiquitin proteolytic system in unperturbed cells, but this turnover is arrested in response to oxidative stress, thereby leading to Nrf2 accumulation. Yet, a mechanistic understanding of how Nrf2 stabilization and transcriptional activation are coupled remains to be determined. We have discovered that the ubiquitin-conjugating enzyme UbcM2 is a novel regulator of Nrf2. Recombinant Nrf2 and UbcM2 form a complex upon alkylation of a non-catalytic cysteine in UbcM2, Cys-136. Substitution of this cysteine with a phenylalanine (C136F) to mimic cysteine oxidation/alkylation results in constitutive binding of UbcM2 to Nrf2 and an increased half-life of the transcription factor in vivo. We provide evidence that UbcM2 and Nrf2 form a nuclear complex utilizing the DNA binding, Neh1 domain, of Nrf2. Finally, we demonstrate that UbcM2 can enhance the transcriptional activity of endogenous Nrf2 and that Cys-136 and the active-site cysteine, Cys-145, jointly contribute to this regulation. Collectively, these data identify UbcM2 as a novel component of the Nrf2 regulatory circuit and position cysteine 136 as a putative redox sensor in this signaling pathway. This work implicates UbcM2 in the restoration of redox homeostasis following oxidative stress.

NRF2 targeting: a promising therapeutic strategy in chronic obstructive pulmonary disease

“…Moreover, phosphatidylinositol 3-kinase could contribute to the depolymerization and disruption of the actin cytoskeleton, concomitant dysregulation of KEAP1 and subsequent NRF2 nuclear accumulation [27]. In addition, a recent study suggested that the ubiquitin conjugating enzyme UBCM2, through its function as a redox sensor, can enhance NRF2 stability and activity during oxidative stress [28]. The nuclear import and export of KEAP1 and/or NRF2 leads to the cytoplasmic-nuclear shuttling of NRF2 [29].…”

Endoplasmic reticulum stress and Nrf2 signaling in cardiovascular diseases

“…The Neh1 domain contains the bZIP motif, which allows Nrf2 to bind to the antioxidant response element (ARE) sequence. In addition, this domain can interact with E2 ubiquitin conjugating enzyme to regulate the Nrf2 protein stability [51]. The Neh2 domain, located in the most N-terminal region, acts as a negative regulatory domain by binding to the Nrf2 inhibitor Keap1 [45].…”

Ubiquitin–proteasome pathway and cellular responses to oxidative stress

“…When a cell is exposed to oxidative stress, Nrf2 dissociates from the Keap1/Cul3 complex and translocates into the nucleus, leading to activation of ARE-mediated gene expression [188]. A recent study indicates that a specific ubiquitin conjugating enzyme, UbcM2, acts as a redox sensor and a regulator of Nrf2 activation [189]. When the function of the UPP was impaired or inhibited, Nrf2 accumulated in cells and activated the expression of many antioxidant enzymes [186, 190–192].…”