title: Requirement for Raf and MAP kinase function during the meiotic maturation of Xenopus oocytes.
abstract: The role of Raf and MAPK (mitogen-activated protein kinase) during the maturation of Xenopus oocytes was investigated. Treatment of oocytes with progesterone resulted in a shift in the electrophoretic mobility of Raf at the onset of germinal vesicle breakdown (GVBD), which was coincident with the activation of MAPK. Expression of a kinase-defective mutant of the human Raf-1 protein (KD-RAF) inhibited progesterone-mediated MAPK activation. MAPK activation was also inhibited by KD-Raf in oocytes expressing signal transducers of the receptor tyrosine kinase (RTK) pathway, including an activated tyrosine kinase (Tpr-Met), a receptor tyrosine kinase (EGFr), and Ha-RasV12. KD-RAF completely inhibited GVBD induced by the RTK pathway. In contrast, KD-RAF did not inhibit GVBD and the progression to Meiosis II in progesterone-treated oocytes. Injection of Mos-specific antisense oligodeoxyribonucleotides inhibited MAPK activation in response to progesterone and Tpr-Met, but failed to inhibit these events in oocytes expressing an oncogenic deletion mutant of Raf-1 (delta N'Raf). Injection of antisense oligodeoxyribonucleotides to Mos also reduced the progesterone- and Tpr-Met-induced electrophoretic mobility shift of Xenopus Raf. These results demonstrate that RTKs and progesterone participate in distinct yet overlapping signaling pathways resulting in the activation of maturation or M-phase promoting factor (MPF). Maturation induced by the RTK pathway requires activation of Raf and MAPK, while progesterone-induced maturation does not. Furthermore, the activation of MAPK in oocytes appears to require the expression of Mos.
authors.affiliation: Molecular Mechanisms of Carcinogenesis Laboratory, NCI-Frederick Cancer Research and Development Center, Maryland 21702.
authors.forename: J R
authors.initials: JR
authors.lastname: Fabian
authors.forename: D K
authors.initials: DK
authors.lastname: Morrison
authors.forename: I O
authors.initials: IO
authors.lastname: Daar
mesh_terms: D000818:Animals; D001483:Base Sequence; D004789:Enzyme Activation; D005260:Female; D008540:Meiosis / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D017231:Proto-Oncogene Proteins c-mos / Q000096:biosynthesis; D019908:Proto-Oncogene Proteins c-raf; D015398:Signal Transduction; D014982:Xenopus laevis
chemical_list: D009838:Oligodeoxyribonucleotides; D011518:Proto-Oncogene Proteins; D011374:Progesterone; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017231:Proto-Oncogene Proteins c-mos; D019908:Proto-Oncogene Proteins c-raf; D019950:Mitogen-Activated Protein Kinase 1