A G? stimulated adenylyl cyclase is involved in xenopus laevis oocyte maturationData deposition: The sequence reported in this article has been deposited in the GenBank database (accession no. AY462195).

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 ? heterodimer is involved in oocyte maturation arrest. Since AC is the proposed target for G? action, we considered of importance to identify and characterize the G? 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 G? was capable to activate oocyte AC only in the presence of the activated form of Gas (Gas-GTP?S), which is in agreement with the G? 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-G? 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 G?-activated AC is playing an important role in Xenopus oocyte meiotic arrest in a Gas-GTP dependent manner. 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]