Expression of ERβ induces bovine ovarian granulosa cell autophagy via the AKT/mTOR pathway.

The aim of our study was to determine whether silencing or overexpression of estrogen receptor β (ERβ) regulates cell proliferation, steroidogenesis, autophagy and signalling pathways in bovine ovarian granulosa cells in vitro. In this study, bovine ovarian granulosa cells (BGCs) were cultured and transfected with ERβ siRNA (si-ERβ) or a plasmid overexpressing ERβ (oe-ERβ), and CCK-8 kit was used to assess cell proliferation. Real-time PCR was used to measure gene transcription. Western blotting was used to measure protein expression, and a specific kit was used to measure the production of steroid hormones. The results showed the expression level of ERβ affects BGC proliferation according to the gene transcription levels of FSHR, CYP19A1, HSD3β1 and STAR and the production of E2 and P4. ERβ was identified as an important nuclear receptor that induced BGC autophagy based on the mRNA and protein expression of autophagy-related genes. Furthermore, the role of ERβ in BGC autophagy was confirmed through treatment with rapamycin (RAPA) or 3-methyladenine (3-MA) in BGCs by cotransfection with si-ERβ or oe-ERβ in BGCs. The results related to AKT/mTOR signalling and phosphorylation suggested that ERβ induces BGC autophagy through attenuating AKT/mTOR signalling. In summary, this study demonstrates that silencing or overexpression of ERβ regulates BGC proliferation and function and induces BGC autophagy by targeting AKT/mTOR signalling. These data reveal a novel regulatory mechanism of autophagy via ERβ and provide insights into the role of autophagy in BGCs.