Abstract
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.
2005 Wiley-Liss, Inc.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenylyl Cyclases / genetics
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Adenylyl Cyclases / isolation & purification
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Adenylyl Cyclases / metabolism*
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Animals
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Cell Differentiation / genetics
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Cell Differentiation / physiology*
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Cell Membrane / genetics
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Cell Membrane / metabolism
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Female
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GTP-Binding Protein alpha Subunits / genetics
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GTP-Binding Protein alpha Subunits / metabolism
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GTP-Binding Protein beta Subunits / genetics
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GTP-Binding Protein beta Subunits / metabolism*
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GTP-Binding Protein gamma Subunits / genetics
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GTP-Binding Protein gamma Subunits / metabolism*
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Gene Expression Regulation, Developmental / genetics
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Guanosine 5'-O-(3-Thiotriphosphate) / genetics
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Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
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Molecular Sequence Data
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Oocytes / cytology
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Oocytes / growth & development*
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Oocytes / metabolism*
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Peptide Fragments / genetics
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Peptide Fragments / isolation & purification
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Peptide Fragments / pharmacology
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Progesterone / metabolism
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Progesterone / pharmacology
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Protein Isoforms / genetics
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Protein Isoforms / isolation & purification
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Protein Isoforms / metabolism
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Xenopus Proteins / genetics
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Xenopus Proteins / isolation & purification
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Xenopus Proteins / metabolism
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Xenopus laevis / genetics
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Xenopus laevis / metabolism*
Substances
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G-protein Beta gamma
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GTP-Binding Protein alpha Subunits
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GTP-Binding Protein beta Subunits
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GTP-Binding Protein gamma Subunits
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Peptide Fragments
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Protein Isoforms
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Xenopus Proteins
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Guanosine 5'-O-(3-Thiotriphosphate)
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Progesterone
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Adenylyl Cyclases
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adenylyl cyclase 2
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adenylyl cyclase 7