title: Deciphering the H-Ras pathway in Xenopus oocyte.
abstract: Xenopus oocytes are arrested in prophase of the first meiotic division. In response to progesterone, they re-enter meiosis and arrest again in metaphase of the second meiotic division. This process, called meiotic maturation, is under the control of the Cyclin B-Cdc2 complex, M phase promoting factor (MPF). Injection of a constitutively active Xenopus H-Ras protein activates MPF, suggesting that Ras proteins could be implicated in the progesterone transduction pathway. The aim of this study was (1) to elucidate the pathway triggered by H-Ras leading to MPF activation in Xenopus oocytes and (2) to investigate whether endogenous H-Ras is involved in the physiological process of meiotic maturation. We generated three constitutively active double mutants, each of them recruiting a single effector in mammalian cells, mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K) or RalGDS. Our results show that the activation of a PI3K-related enzyme is crucial for H-Ras-induced MPF activation, whereas the recruitment of either MAPK or RalGDS is not. However, although the H-Ras/PI3K pathway is functional in Xenopus oocytes, it is not the physiological transducer of progesterone responsible for meiotic resumption.
authors.affiliation: Laboratoire de Biologie du Développement, UMR-CNRS 7622, Université Pierre et Marie Curie, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Gaffré
authors.forename: A
authors.initials: A
authors.lastname: Dupré
authors.forename: R
authors.initials: R
authors.lastname: Valuckaite
authors.forename: K
authors.initials: K
authors.lastname: Suziedelis
authors.forename: C
authors.initials: C
authors.lastname: Jessus
authors.forename: O
authors.initials: O
authors.lastname: Haccard
mesh_terms: D000818:Animals; D002455:Cell Division; D005260:Female; D011905:Genes, ras; D016296:Mutagenesis; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D014982:Xenopus laevis / Q000235:genetics / Q000502:physiology*
chemical_list: D012333:RNA, Messenger