The classical progesterone receptor mediates Xenopus oocyte maturation through a nongenomic mechanism.
Xenopus laevis oocytes are physiologically arrested at G(2) of meiosis I. Resumption of meiosis, or oocyte maturation, is triggered by progesterone. Progesterone-induced Xenopus oocyte maturation is mediated via an extranuclear receptor and is independent of gene transcription. The identity of this extranuclear oocyte progesterone receptor (PR), however, has remained a longstanding problem. We have isolated the amphibian homologue of human PR from a Xenopus oocyte cDNA library. The cloned Xenopus progesterone receptor (xPR) functioned in heterologous cells as a progesterone-regulated transcription activator. However, endogenous xPR was excluded from the oocyte nucleus and instead appeared to be a cytosolic protein not associated with any membrane structures. Injection of xPR mRNA into Xenopus oocytes accelerated the progesterone-induced oocyte maturation and reduced the required concentrations of progesterone. In enucleated oocytes, xPR accelerated the progesterone-induced mitogen-activated protein kinase activation. These data suggest that xPR is the long sought after Xenopus oocyte receptor responsible for progesterone-induced oocyte maturation.
Bayaa
M
M
Loeb Research Institute, Ottawa Hospital, 1053 Carling Avenue, Ottawa, ON, Canada.
Booth
R A
RA
Sheng
Y
Y
Liu
X J
XJ
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary; D018858:Germinal Center; D006801:Humans; D008540:Meiosis / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D011817:Rabbits; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014982:Xenopus laevis / Q000378:metabolism / Q000502:physiology
D018076:DNA, Complementary; D011980:Receptors, Progesterone; D015534:Trans-Activators