The Golgi Stacking Protein GORASP2 Regulates Mouse Primordial Follicle Activation by Suppressing the Autophagy Lysosome Pathway via RAP1 Competing With mTOR for RAPTOR Binding

Primordial follicle pool is the foundation of female reproductive life and abnormal primordial follicle activation may lead to severe diseases such as premature ovarian failure and premature ovarian insufficiency. Golgi reassembly stacking protein 2 (GORASP2) plays an important role in autophagy by regulating autophagy maturation through glycosylation modification. In the current study we found that GORASP2 is a key factor in mammalian primordial follicle activation through autophagy lysosome pathway. Knocking down of Gorasp2 in the ovaries of newborn mice led to decreased number of activated primary follicles, and the level of FSH (Follicle-stimulating Hormone) in the primary follicles was increased. Comparing with negative control ovaries, transcription profiling showed differentially expressed genes were mainly enriched in the autophagic lysosome, HIF-1 signaling pathway and PI3K-AKT signaling pathway. We found that the ratio of autophagy marker protein LC3-II/LC3-I increased and the level of SQSTM1 protein decreased by Western blot, indicating an elevated autophagy level in GORASP2-knockdown ovaries. Further examination demonstrated that the small G protein Rap1, a member of the Ras superfamily was activated after GORASP2 inhibition and the phosphorylation of mTOR was inhibited by disrupting the mTOR-Raptor interaction, thus initiating autophagy in primordial follicles. In addition, levels of ROS and ATP were increased and citrate lyase was decreased, suggesting a putative disrupted mitochondrial function. Finally, AKT signaling pathways were blocked and may also affect the developmental potential of these affected primordial follicles. In summary, our study emphasized the Golgi stacking protein GORASP2 as an important regulator in primordial follicle activation by participating in the initiation of autophagy, providing an experimental basis for the involvement of Golgi related components in the activation process of primordial follicles through autophagy pathway. This study also shed light upon the deeper understanding of primordial follicle activation related diseases and may contribute a new angle for their future treatment.