title: Growth differentiation factor 9 signaling requires ERK1/2 activity in mouse granulosa and cumulus cells.
abstract: 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.
authors.affiliation: The Robinson Institute, School of Paediatrics and Reproductive Health, Medical School, University of Adelaide, SA, Adelaide 5005, Australia.
authors.forename: Maxime
authors.initials: M
authors.lastname: Sasseville
authors.forename: Lesley J
authors.initials: LJ
authors.lastname: Ritter
authors.forename: Thao M
authors.initials: TM
authors.lastname: Nguyen
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: David G
authors.initials: DG
authors.lastname: Mottershead
authors.forename: Darryl L
authors.initials: DL
authors.lastname: Russell
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gilchrist
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D054885:Cumulus Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D055429:Growth Differentiation Factor 9 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D048053:Mitogen-Activated Protein Kinase 6 / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D015398:Signal Transduction; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D055429:Growth Differentiation Factor 9; D051900:Smad3 Protein; D066246:ErbB Receptors; C474633:Mapk6 protein, mouse; D048052:Mitogen-Activated Protein Kinase 3; D048053:Mitogen-Activated Protein Kinase 6