CREB activity is required for mTORC1 signaling-induced primordial follicle activation in mice

• Published in: Histochemistry and cell biology Vol. 154; no. 3; pp. 287 - 299
• Main Authors: Li, Jia, Zhang, Yu, Zheng, Nana, Li, Biao, Yang, Jing, Zhang, Chunyu, Xia, Guoliang, Zhang, Meijia
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2020
• Subjects: Animals; Apoptosis - drug effects; Biochemistry; Biomedical and Life Sciences; Biomedicine; Cell Biology; Cell Proliferation - drug effects; Cyclic AMP Response Element-Binding Protein - metabolism; Developmental Biology; Female; Male; Mechanistic Target of Rapamycin Complex 1 - genetics; Mechanistic Target of Rapamycin Complex 1 - metabolism; Mice; Mice, Inbred ICR; Naphthols - pharmacology; Organophosphates - pharmacology; Original Paper; Ovarian Follicle - drug effects; Ovarian Follicle - metabolism; Phosphorylation; Signal Transduction - genetics; Stem Cell Factor - antagonists & inhibitors; Stem Cell Factor - metabolism; Tissue Culture Techniques; Vanadium Compounds - antagonists & inhibitors; Vanadium Compounds - pharmacology; Primordial follicle activation; CREB; KITL; mTORC1
• ISSN: 0948-6143; 1432-119X
• DOI: 10.1007/s00418-020-01888-4

In mammals, progressive activation of primordial follicles is essential for maintenance of the reproductive lifespan. Several reports have demonstrated that mitogen-activated protein kinases 3 and 1 (MAPK3/1)–mammalian target of rapamycin complex 1 (mTORC1) signaling in pre-granulosa cells promotes primordial follicle activation by increasing KIT ligand (KITL) expression and then stimulating phosphatidylinositol 3 kinase signaling in oocytes. However, the mechanism of mTORC1 signaling in the promotion of KITL expression is unclear. Immunofluorescence staining results showed that phosphorylated cyclic AMP response element-binding protein (CREB) was mainly expressed in pre-granulosa cells. The CREB inhibitor KG-501 and CREB knockdown by Creb siRNA significantly suppressed primordial follicle activation, reduced pre-granulosa cell proliferation and dramatically increased oocyte apoptosis. Western blotting results demonstrated that both the MAPK3/1 inhibitor U0126 and mTORC1 inhibitor rapamycin significantly decreased the levels of phosphorylated CREB, indicating that MAPK3/1–mTORC1 signaling is required for CREB activation. Furthermore, CREB could bind to the Kitl promoter region, and KG-501 significantly decreased the expression levels of KITL. In addition, KG-501 and CREB knockdown significantly decreased the levels of phosphorylated Akt, leading to a reduced number of oocytes with Foxo3a nuclear export. KG-501 also inhibited bpV (HOpic)-stimulated primordial follicle activation. Taken together, the results show that CREB is required for MAPK3/1–mTORC1 signaling-promoted KITL expression followed by the activation of primordial follicles.