The Robinson Institute, School of Paediatrics and Reproductive Health, Medical School, University of Adelaide, SA, Adelaide 5005, Australia.
J Cell Sci. 2010 Sep 15;123(Pt 18):3166-76. doi: 10.1242/jcs.063834. Epub 2010 Aug 24.
Ovarian 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 TGFbeta1 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 TGFbeta-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.
卵巢卵泡发生是由内分泌信号和旁分泌因子的共同作用驱动的。卵母细胞分泌强大的有丝分裂原，如生长分化因子 9（GDF9），调节颗粒细胞增殖、代谢、甾体生成和分化。本研究探讨了表皮生长因子受体（EGFR）-细胞外信号调节激酶 1 和 2（ERK1/2；也称为 MAPK3/1）信号通路在 GDF9 对颗粒细胞作用中的作用。结果表明，EGFR-ERK1/2 通路的药理学抑制可阻止卵母细胞的有丝分裂作用。重要的是，EGFR-ERK1/2 活性以及 Rous 肉瘤致癌基因家族激酶（SFK）是通过 SMAD 介导 GDF9、激活素 A 和 TGFbeta1 有丝分裂作用在颗粒细胞中信号转导所必需的。GDF9 不能激活 ERK1/2 或影响颗粒细胞中的 EGF 刺激的 ERK1/2。然而，GDF9 在颗粒细胞中诱导 SMAD3 特异性 CAGA 报告基因需要活跃的 EGFR、SFKs 和 ERK1/2，就像 GDF9 反应性基因表达一样。最后，证明 EGFR-SFKs-ERK1/2 通路对于 SMAD3 连接区磷酸化的维持是必需的。我们的研究结果表明，包括 GDF9 在内的卵母细胞分泌因子对颗粒细胞的接受能力受到 EGFR 激活水平和由此产生的 ERK1/2 活性的调节，通过 SMAD3 在连接区的必需许可性磷酸化。我们的结果表明，卵母细胞分泌的 TGFbeta 样配体和 EGFR-ERK1/2 信号协同作用，对于卵母细胞介导的颗粒细胞对信号的独特反应是必需的，该信号介导颗粒细胞存活和增殖，从而促进卵泡生长和排卵。
