RESUMEN

Xenopus laevis oocyte maturation is induced by the steroid hormone progesterone through a nongenomic mechanism that implicates the inhibition of the effector system adenylyl cyclase (AC). Recently, it has been shown that the G protein betagamma heterodimer is involved in oocyte maturation arrest. Since AC is the proposed target for Gbetagamma action, we considered of importance to identify and characterize the Gbetagamma regulated AC isoform(s) that are expressed in the Xenopus oocyte. Through biochemical studies, we found that stage VI plasma membrane oocyte AC activity showed attributes of an AC2 isoform. Furthermore, exogenous Gbetagamma was capable to activate oocyte AC only in the presence of the activated form of Galphas (Galphas-GTPgammaS), which is in agreement with the Ggammabeta conditional activation reported for the mammalian AC2 and AC4 isotypes. In order to study the functional role of AC in oocyte maturation we cloned from a Xenopus oocyte cDNA library a gene encoding an AC with high identity to AC7 (xAC7). Based on this sequence, we constructed a minigene encoding the AC-Gbetagamma interacting region (xAC7pep) to block, within the oocyte, this interaction. We found that microinjection of the xAC7pep potentiated progesterone-induced maturation, as did the AC2 minigene. From these results we can conclude that a Gbetagamma-activated AC is playing an important role in Xenopus oocyte meiotic arrest in a Galphas-GTP dependent manner.

Asunto(s)

Adenilil Ciclasas/metabolismo , Diferenciación Celular/fisiología , Subunidades beta de la Proteína de Unión al GTP/metabolismo , Subunidades gamma de la Proteína de Unión al GTP/metabolismo , Oocitos/crecimiento & desarrollo , Oocitos/metabolismo , Xenopus laevis/metabolismo , Adenilil Ciclasas/genética , Adenilil Ciclasas/aislamiento & purificación , Animales , Diferenciación Celular/genética , Membrana Celular/genética , Membrana Celular/metabolismo , Femenino , Subunidades alfa de la Proteína de Unión al GTP/genética , Subunidades alfa de la Proteína de Unión al GTP/metabolismo , Subunidades beta de la Proteína de Unión al GTP/genética , Subunidades gamma de la Proteína de Unión al GTP/genética , Regulación del Desarrollo de la Expresión Génica/genética , Guanosina 5'-O-(3-Tiotrifosfato)/genética , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Datos de Secuencia Molecular , Oocitos/citología , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/aislamiento & purificación , Fragmentos de Péptidos/farmacología , Progesterona/metabolismo , Progesterona/farmacología , Isoformas de Proteínas/genética , Isoformas de Proteínas/aislamiento & purificación , Isoformas de Proteínas/metabolismo , Proteínas de Xenopus/genética , Proteínas de Xenopus/aislamiento & purificación , Proteínas de Xenopus/metabolismo , Xenopus laevis/genética