【 TITLE 】SESN2/NRF2 signaling activates as a direct downstream regulator of the PERK pathway against endoplasmic reticulum stress to improve the in vitro maturation of porcine oocytes

【 JOURNAL 】Free Radical Biology and Medicine

​【 NAME 】Hyo-Jin Park, Seul-Gi Yang, and Deog-Bon Koo

【 PUBLISHED 】17 December 2021

【 ISSN 】0891-5849

【 DOI 】https://doi.org/10.1016/j.freeradbiomed.2021.12.258

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【 ABSTRACT 】

 Nuclear erythroid 2-related factor 2 (NRF2) is a critical regulator of oxidative stress in mammalian oocytes. Our

previous study described the protective effects of Sestrin-2 (SESN2) as a stress regulator against endoplasmic

reticulum (ER) stress in porcine oocytes during in vitro maturation (IVM). However, their roles in unfolded

protein response-related signaling pathways in porcine oocyte maturation capacity remain unknown. The purpose

of this study was to evaluate the role of SESN2/NRF2 signaling in H2O2-induced oxidative stress and ER

stress via protein kinase-like ER kinase (PERK) downstream factor during porcine oocyte maturation. Here, we

found that the p-NRF2(Ser40) activation in the nucleus of porcine oocytes was accompanied by PERK signaling

downregulation using western blot and immunofluorescence staining at 44 h after IVM. The total and nuclear

NRF2 protein expression was also induced in porcine oocytes following H2O2 and tunicamycin (Tm) exposure.

Notably, the upregulation of PERK signaling significantly increased the SESN2 and NRF2 signaling in H2O2-and

Tm-exposed porcine cumulus oocyte complexes. Interestingly, inducing the knockdown of the SESN2 gene

expression by siRNA interrupted the NRF2 signaling activation of porcine oocyte maturation, whereas NRF2

expression blockade by ochratoxin A, an NRF2 inhibitor, did not affect the expression level of the SESN2 protein.

Moreover, a defect in SESN2 completely blocked the activity of nuclear NRF2 on spindle assembly in porcine

oocytes. These findings suggest that the PERK/SESN2/NRF2 signaling pathway may play an important role

against ER stress during meiotic maturation and oocyte maturation capacity.

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【 KEYWORDS 】Endoplasmic reticulum stress (ER stress), Protein kinase-like ER kinase (PERK) signal, Nuclear erythroid 2-related factor 2 (NRF2), Sestrin-2 (SESN2), Porcine oocyte, In vitro maturation (IVM)