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

Abstract

Nrf2 plays critical roles in animals' defense against electrophiles and oxidative stress by orchestrating the induction of cytoprotective genes. We previously isolated the zebrafish mutant , which displays up-regulated expression of Nrf2 target genes in an uninduced state. In this paper, we determine that the gene responsible for was the zebrafish homolog of phosphomannomutase 2 (Pmm2), which is a key enzyme in the initial steps of N-glycosylation, and its mutation in humans leads to PMM2-CDG (congenital disorders of glycosylation), the most frequent type of CDG. The larvae exhibited mild defects in N-glycosylation, indicating that the mutation is a hypomorph, as in human PMM2-CDG patients. A gene expression analysis showed that larvae display up-regulation of endoplasmic reticulum (ER) stress, suggesting that the activation of Nrf2 was induced by the ER stress. Indeed, the treatment with the ER stress-inducing compounds up-regulated the expression in an Nrf2-dependent manner. Furthermore, the up-regulation of by the inactivation was diminished by knocking down or out double-stranded RNA-activated protein kinase (PKR)-like ER kinase (PERK), one of the main ER stress sensors, suggesting that Nrf2 was activated in response to the ER stress via the PERK pathway. ER stress-induced activation of Nrf2 was reported previously, but the results have been controversial. Our present study clearly demonstrated that ER stress can indeed activate Nrf2 and this regulation is evolutionarily conserved among vertebrates. Moreover, ER stress induced in mutants was ameliorated by the treatment of the Nrf2-activator sulforaphane, indicating that Nrf2 plays significant roles in the reduction of ER stress.

Repurposing the aldose reductase inhibitor and diabetic neuropathy drug epalrestat for the congenital disorder of glycosylation PMM2-CDG

“…We initially hypothesized that activation of NRF2 would lead to increased PMM2 mRNA levels, which in turn would lead to increased PMM2 protein abundance. Consistent with that hypothesis, treatment of pmm2 zebrafish mutant with the NRF2 activator sulforaphane resulted in rescue of phenotypic defects (Mukaigasa et al, 2018). We know from our studies of yeast PMM2-CDG models that overexpression of F119L mutant PMM2 protein can rescue growth by mass action effects (Lao et al, 2019).…”

“…We propose that aldose reductase inhibition leads to an increase in glucose-1,6-bisphosphate levels as a result of glucose being shunted away from the polyol pathway toward production of phosphorylated glucose. Evidence from epalrestat-treated pmm-2 mutant worms suggests there may also be a minor role for NRF2 as an indirect transcriptional activator of PMM2, which is consistent with a role for NRF2 activation in rescuing hypoglycosylation stress phenotypes a pmm2 mutant zebrafish (Mukaigasa et al, 2018).…”

“…Worm pellets were homogenized and RNA extracted following published protocols (Guthmueller et al, 2011). ER stress markers were selected based on the pmm2 zebrafish model (Mukaigasa et al, 2018). Cq stands for cycle quantification.…”

“…It was recently reported that a pmm2 hypomorphic mutant zebrafish constitutively activates NRF2 and furthermore that the small molecule NRF2 activator sulforaphane ameliorates endoplasmic reticulum (ER)-associated stress markers (Mukaigasa et al, 2018). Therefore, we tested whether epalrestat acts similarly to sulforaphane by interrogating mRNA expression levels of the worm orthologs of the ER stress markers that are induced in a pmm2 hypomorphic mutant zebrafish.…”

Absence of Dipeptidyl Peptidase 3 Increases Oxidative Stress and Causes Bone Loss

“…In fact, as far as we investigated, in many aspects Dpp3 gene inactivation led to a phenotype closely resembling the condition displayed in Nrf2 KO and in Ho-1 KO mouse. (20,63,64) Moreover, because Nrf2 is known to take also part in other important cellular processes, such as proteostasis maintenance and endoplasmic reticulum stress quenching, (65,66) absence of DPP3 might also have a detrimental effect in those Nrf2-related contexts, which have not been addressed here.…”