Conservation of the Nrf2‐Mediated Gene Regulation of Proteasome Subunits and Glucose Metabolism in Zebrafish

Abstract

The Keap1-Nrf2 system is an evolutionarily conserved defense mechanism against oxidative and xenobiotic stress. Besides the exogenous stress response, Nrf2 has been found to regulate numerous cellular functions, including protein turnover and glucose metabolism; however, the evolutionary origins of these functions remain unknown. In the present study, we searched for novel target genes associated with the zebrafish Nrf2 to answer this question. A microarray analysis of zebrafish embryos that overexpressed Nrf2 revealed that 115 candidate genes were targets of Nrf2, including genes encoding proteasome subunits and enzymes involved in glucose metabolism. A real-time quantitative PCR suggested that the expression of 3 proteasome subunits (psma3, psma5, and psmb7) and 2 enzymes involved in glucose metabolism (pgd and fbp1a) were regulated by zebrafish Nrf2. We thus next examined the upregulation of these genes by an Nrf2 activator, diethyl maleate, using Nrf2 mutant zebrafish larvae. The results of real-time quantitative PCR and whole-mount in situ hybridization showed that all of these 5 genes were upregulated by diethyl maleate treatment in an Nrf2-dependent manner, especially in the liver. These findings implied that the Nrf2-mediated regulation of the proteasome subunits and glucose metabolism is evolutionarily conserved among vertebrates.

Nrf2 activation attenuates genetic endoplasmic reticulum stress induced by a mutation in the phosphomannomutase 2 gene in zebrafish

“…Since the conservation of ER stress regulation among vertebrates has been validated using medaka fish and zebrafish (37,57,58), the attenuation of ER stress by Nrf2 activation may be an effective strategy, not only for human health, but also farming animals. The molecular basis of this attenuation is unknown, but enhancement of ER-associated degradation (ERAD) of unfolded and misfolded proteins by Nrf2-dependent up-regulation of proteasome subunits might have contributed (18,49,59).…”

“…The Keap1-Nrf2 system is well conserved among vertebrates, including zebrafish (6)(7)(8), in light of its molecular basis (9-11), activating chemicals and stress (12)(13)(14)(15), target genes (16)(17)(18), and physiological functions (15,19). We previously isolated six mutant zebrafish lines in which Nrf2 is activated without treatment with Nrf2 activators (12).…”

Conservation of the Keap1-Nrf2 System: An Evolutionary Journey through Stressful Space and Time

“…Lineups of Nrf2 target genes are also conserved in zebrafish. Proteins involved in the detoxification pathway, antioxidant proteins, proteasome subunits and pentose phosphate pathway enzymes are also regulated by the Nrf2 system in zebrafish [ 77 , 78 , 79 , 80 ]. This experimental evidence clearly shows that vertebrates have an evolutionarily conserved Keap1-Nrf2 system.…”

“…Second, Mitsuishi et al showed that an active Nrf2 system in cancer cells upregulates the anabolic pathway through the transcriptional activation of pentose phosphate pathway enzymes, which enhances the cell proliferation [ 35 ]. We recently found that a gene encoding the pentose phosphate pathway enzyme phosphogluconate dehydrogenase ( pgd ) is also under the regulation of Nrf2 in zebrafish [ 80 ], suggesting that there is a conserved function among vertebrates. Zebrafish, in addition to mice, will prove a useful model for studying cell proliferation during normal development as well as under pathological conditions.…”

Evaluation of Antioxidant Activity of Spice-Derived Phytochemicals Using Zebrafish

“…In contrast, zebrafish might be useful for a comprehensive phytochemical analysis, since it is easy to prepare thousands of embryos/larvae at once and to perform drug treatments using them [16]. We have studied the Nrf2 pathway using zebrafish for two decades and found that the functions and regulatory mechanism of the Nrf2 pathway are highly conserved among vertebrates [17][18][19][20][21][22][23][24][25][26]. We also established a mutant line of zebrafish Nrf2 (nfe2l2a fh318 ) and demonstrated that the antioxidant activity of zebrafish larvae was increased by the treatment of sulforaphane and other Nrf2-activating compounds in an Nrf2-dependent manner [15,27,28].…”