Growth differentiation factor 9 signaling requires ERK1/2 activity in mouse granulosa and cumulus cells

Abstract

SummaryOvarian folliculogenesis is driven by the combined action of endocrine cues and paracrine factors. The oocyte secretes powerful mitogens, such as growth differentiation factor 9 (GDF9), that regulate granulosa cell proliferation, metabolism, steroidogenesis and differentiation. This study investigated the role of the epidermal growth factor receptor (EGFR)-extracellular signal-regulated kinase 1 and 2 (ERK1/2; also known as MAPK3/1) signaling pathway on GDF9 action on granulosa cells. Results show that mitogenic action of the oocyte is prevented by pharmacological inhibition of the EGFR-ERK1/2 pathway. Importantly, EGFR-ERK1/2 activity as well as rous sarcoma oncogene family kinases (SFK) are required for signaling through SMADs, mediating GDF9, activin A and TGF1 mitogenic action in granulosa cells. GDF9 could not activate ERK1/2 or affect EGF-stimulated ERK1/2 in granulosa cells. However, induction of the SMAD3-specific CAGA reporter by GDF9 in granulosa cells required active EGFR, SFKs and ERK1/2 as did GDF9-responsive gene expression. Finally, the EGFR-SFKs-ERK1/2 pathway was shown to be required for the maintenance of phosphorylation of the SMAD3 linker region. Together our results suggest that receptivity of granulosa cells to oocyte-secreted factors, including GDF9, is regulated by the level of activation of the EGFR and resulting ERK1/2 activity, through the requisite permissive phosphorylation of SMAD3 in the linker region. Our results indicate that oocyte-secreted TGF-like ligands and EGFR-ERK1/2 signaling are cooperatively required for the unique granulosa cell response to the signal from oocytes mediating granulosa cell survival and proliferation and hence the promotion of follicle growth and ovulation.

Follicle-stimulating hormone regulates expression and activity of epidermal growth factor receptor in the murine ovarian follicle

“…Because GCs of Fshb −/− follicles contained detectable EGFR (although it was reduced compared with the heterozygotes), we tested whether EGFR signaling activity was impaired. MAPK3 and 1 are the principal effectors of EGFR signaling, and their activation by phosphorylation is necessary for cumulus expansion (21,28,39,50). Upon the addition of EGF, MAPK3/1 phosphorylation increased significantly in Fshb +/− follicles but did not change detectably in Fshb −/− follicles (Fig.…”

“…Oocyte-secreted factors (OSFs), including growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), are essential for EGF-induced Has2, Ptgs2, and Tnfaip6 up-regulation and cumulus expansion (46)(47)(48)(49)(50)(51). Their effects in GCs are transduced by activation of the Sma-and Mad-related proteins (SMAD) pathway.…”

Differences in the participation of TGFB superfamily signalling pathways mediating porcine and murine cumulus cell expansion

“…Su et al (2010) showed that oocytesecreted GDF9 and BMP15 and subsequent activation of SMAD2/3 in CCs is required for expression of the EGF receptor, which is a principle activator of ERK1/2 in CCs. Our studies elucidated the reciprocal relationship, by demonstrating that EGF receptor/ERK1/2 activity is required to maintain phosphorylation of the SMAD3 linker region, required for downstream SMAD2/3 signalling and oocyte-regulated granulosa/CC functions (Sasseville et al 2010). Together, these two studies suggest some form of feedback loop is operating in CCs between GDF9/BMP15-activated SMAD2/3 and EGF receptor/ERK1/2.…”

“…New evidence is emerging from mouse studies of requisite crosstalk between SMAD and MAPK signalling for coordinated oocyte-somatic cell development (Sasseville et al 2010, Su et al 2010. The role of p38 and ERK1/2 MAPK pathways in COC function in nonrodent species is limited, although some information is available for the pig.…”

“…However, it seems highly unlikely that oocyte-secreted factors have minimal or no role in cumulus expansion in these species, given their fundamental role in regulating CC differentiation and the complexity of interactions with other endocrine and local mediators of folliculogenesis (Gilchrist et al 2008). In particular, the recent demonstration of intricate and critical crosstalk between GDF9/BMP15-activated SMAD2/3 signalling and EGF receptor/ERK1/2 signalling in CCs (Sasseville et al 2010, Su et al 2010, illustrates the high level of complexity required to coordinate ovulatory events. Hence, this study was conducted to examine the participation of oocyte paracrine and SMAD signalling and interactions with MAPK signalling, in porcine cumulus expansion.…”