IGF-1 Inhibits Apoptosis of Porcine Primary Granulosa Cell by Targeting Degradation of BimEL

Abstract

Insulin-like growth factor-1 (IGF-1) is an intra-ovarian growth factor that plays important endocrine or paracrine roles during ovarian development. IGF-1 affects ovarian function and female fertility through reducing apoptosis of granulosa cells, yet the underlying mechanism remains poorly characterized. Here, we aimed to address these knowledge gaps using porcine primary granulosa cells and examining the anti-apoptotic mechanisms of IGF-1. IGF-1 prevented the granulosa cell from apoptosis, as shown by TUNEL and Annexin V/PI detection, and gained the anti-apoptotic index, the ratio of Bcl-2/Bax. This process was partly mediated by reducing the pro-apoptotic BimEL (Bcl-2 Interacting Mediator of Cell Death-Extra Long) protein level. Western blotting showed that IGF-1 promoted BimEL phosphorylation through activating p-ERK1/2, and that the proteasome system was responsible for degradation of phosphorylated BimEL. Meanwhile, IGF-1 enhanced the Beclin1 level and the rate of LC3 II/LC3 I, indicating that autophagy was induced by IGF-1. By blocking the proteolysis processes of both proteasome and autophagy flux with MG132 and chloroquine, respectively, the BimEL did not reduce and the phosphorylated BimEL protein accumulated, thereby indicating that both proteasome and autophagy pathways were involved in the degradation of BimEL stimulated by IGF-1. In conclusion, IGF-1 inhibited porcine primary granulosa cell apoptosis via degradation of pro-apoptotic BimEL. This study is critical for us to further understand the mechanisms of follicular survival and atresia regulated by IGF-1. Moreover, it provides a direction for the treatment of infertility caused by ovarian dysplasia, such as polycystic ovary syndrome and the improvement of assisted reproductive technology.

Degradation of Mutant Protein Aggregates within the Endoplasmic Reticulum of Vasopressin Neurons

“…The LC3-II/LC3-I ratio was also increased in the chloroquine group compared with the control ( Figure S7 B). This is consistent with previous studies showing that LC3-II, a substitute of autophagic degradation, was increased relative to LC3-I when autophagic degradation was inhibited by the lysosome inhibitor chloroquine ( Han et al., 2019 ).…”

Kurarinone attenuates hydrogen peroxide‐induced oxidative stress and apoptosis through activating the PI3K/Akt signaling by upregulating IGF1 expression in human ovarian granulosa cells

“…IGF1 is a growth‐related factor of granulosa cells, and it has been reported to constrain granulosa cell apoptosis through regulating expression of BCL‐2‐interacting mediator of cell death (Bim) 17 . Our study firstly confirmed that IGF1 acted as a target of kurarinone, and kurarinone upregulated IGF1 expression in H 2 O 2 ‐treated KGN cells.…”

“…There were 8 overlapping targets (HRAS, FGFR2, PPARG, FGFR1, LGALS3, IGF1, ST14 and AKT1) by matching the two groups of targets (Figure 4A). Among these targets, IGF1 was the only one that has been reported to be associated with granulosa cell function 17 . Moreover, IGF1 functions as one important upstream of the PI3K/Akt signaling 30–32 .…”

IGF-1 as a Potential Therapy for Spinocerebellar Ataxia Type 3

“…Autophagy can clear aggregated misfolding proteins by inducing the expression of autophagy-related proteins including Beclin1, p62, and LC3. IGF-1 induces autophagy by upregulating the Beclin1 and LC3-II levels [ 64 ]. Wen et al reported that the intramuscular injection of human IGF-1 with a self-complementary adeno-associated virus vector in the cells and mouse models of ALS could upregulate mitochondrial autophagy and suppress mitochondrial apoptosis [ 22 ].…”