A Gβγ stimulated adenylyl cyclase is involved in <i>xenopus laevis</i> oocyte maturation

Guzmán, Leonardo; Romo, Ximena; Grandy, Rodrigo A.; Soto, Ximena; Montecino, Martín; Hinrichs, Maríavictoria; Olate, Juan

doi:10.1002/jcp.20102

Cited by 18 publications

(14 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on these observations it has been proposed that both proteins, Gsa-GTP and Gbg, are constitutively up-regulating AC activity, keeping frog oocytes arrested at the G2/M transition of the cell cycle. The recently cloned Xenopus oocyte AC type 7, which is activated by Gsa-GTP and Gbg (Guzman et al, 2005;Sheng et al, 2005a), strongly supports the above proposal.…”

supporting

confidence: 68%

xRic‐8 is a GEF for Gsα and participates in maintaining meiotic arrest in Xenopus laevis oocytes

Romo

Pastén

Martinez

et al. 2007

Journal Cellular Physiology

Self Cite

View full text Add to dashboard Cite

Immature stage VI Xenopus oocytes are arrested at the G(2)/M border of meiosis I until exposed to progesterone, which induces meiotic resumption through a non-genomic mechanism. One of the earliest events produced by this hormone is inhibition of the plasma membrane enzyme adenylyl cyclase (AC), with the concomitant drop in intracellular cAMP levels and reinitiation of the cell cycle. Recently Gsalpha and Gbetagamma have been shown to play an important role as positive regulators of Xenopus oocyte AC, maintaining the oocyte in the arrested state. However, a question that still remains unanswered, is how the activated state of Gsalpha and Gbetagamma is achieved in the immature oocyte, since no receptor or ligand have been found to be required. Here we provide evidence that xRic-8 can act in vitro and in vivo as a GEF for Gsalpha. Overexpression of xRic-8, through mRNA injection, greatly inhibits progesterone induced oocyte maturation and endogenous xRic-8 mRNA depletion, through siRNA microinjection, induces spontaneous oocyte maturation. These results suggest that xRic-8 is participating in the immature oocyte by keeping Gsalpha-Gbetagamma-AC signaling complex in an activated state and therefore maintaining G2 arrest.

show abstract

supporting

confidence: 68%

xRic‐8 is a GEF for Gsα and participates in maintaining meiotic arrest in Xenopus laevis oocytes

Romo

Pastén

Martinez

et al. 2007

Journal Cellular Physiology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Evidence supporting a mutual requirement for both G␣ s and G␤␥ has come from studies on AC isoforms in oocytes. An ortholog of AC7 was cloned from Xenopus oocytes, which is a G␤␥-activated isoform (46,47). Similar to findings in mammals (48), G␤␥ stimulation of AC in oocyte membranes was dependent on G␣ s activation, and interference with AC/G␤␥ association accelerated progesterone-induced GVBD (46).…”

Section: Discussionmentioning

confidence: 56%

The Role of Xenopus Membrane Progesterone Receptor β in Mediating the Effect of Progesterone on Oocyte Maturation

Ben‐Yehoshua

Lewellyn

Thomas³

et al. 2007

Molecular Endocrinology

101

View full text Add to dashboard Cite

Rapid, nongenomic membranal effects of progesterone were demonstrated in amphibian oocytes more than 30 y ago. Recently, a distinct family of membrane progestin receptors (mPRs) has been cloned in fish and other vertebrate species. In this study we explore the role of mPR in promoting oocyte maturation in Xenopus laevis. RT-PCR analysis indicates that Xenopus oocytes contain transcripts for the mPRbeta ortholog, similar to what has been reported in zebrafish oocytes, and Western blotting shows that the protein is expressed on the oocyte plasma membrane. Microinjection of mPRbeta-specific antibodies into oocytes resulted in a dramatic inhibition of progesterone-dependent oocyte maturation, whereas microinjection of mRNA encoding Myc-Xenopus mPR (XmPR)beta resulted in an accelerated rate of progesterone-induced oocyte maturation, concomitant with membranal localization of the protein. Binding studies in mammalian cells expressing XmPRbeta confirmed specific binding of progesterone by the expressed protein. These results suggest that XmPRbeta is a physiological progesterone receptor involved in initiating the resumption of meiosis during maturation of Xenopus oocytes.

show abstract

“…Second, over-expression of either Gα s or Gβγ inhibits steroid-triggered oocyte maturation, while reduction of Gα s or Gβγ levels or activity leads to enhanced maturation in response to steroids [13][14][15][16]. Third, stimulation of overexpressed Gα s -or Gβγ-coupled receptors markedly inhibits steroid-triggered oocyte maturation [17,18]. Finally, by using over-expressed Gβγ-regulated inward rectifying potassium channels (GIRKs) as markers of endogenous Gβγ signaling in oocytes, constitutive Gβγ signaling is detected that is reduced within minutes after steroid stimulation (Hammes, in press).…”

Section: Meiosis In Frog Oocytesmentioning

confidence: 99%

Gβγ signaling reduces intracellular cAMP to promote meiotic progression in mouse oocytes

Gill

Hammes

2007

Steroids

View full text Add to dashboard Cite

In nearly every vertebrate species, elevated intracellular cAMP maintains oocytes in prophase I of meiosis. Prior to ovulation, gonadotropins trigger various intra-ovarian processes, including the breakdown of gap junctions, the activation of EGF receptors, and the secretion of steroids. These events in turn decrease intracellular cAMP levels in select oocytes to allow meiotic progression, or maturation, to resume. Studies suggest that cAMP levels are kept elevated in resting oocytes by constitutive G protein signaling, and that the drop in intracellular cAMP that accompanies maturation is due to attenuation of this inhibitory G protein-mediated signaling. Interestingly, one of these G protein regulators of meiotic arrest is the Gα s protein, which stimulates adenylyl cyclase to raise intracellular cAMP in two important animal models of oocyte development: Xenopus leavis frogs and mice. In addition to Gα s , constitutive Gβ γ activity similarly stimulates adenylyl cyclase to raise cAMP and prevent maturation in Xenopus oocytes; however, the role of Gβ γ in regulating meiosis in mouse oocytes has not been examined. Here we show that Gβγ does not contribute to the maintenance of murine oocyte meiotic arrest. In fact, contrary to observations in frog oocytes, Gβγ signaling in mouse oocytes reduces cAMP and promotes oocyte maturation, suggesting that Gβγ might in fact play a positive role in promoting oocyte maturation. These observations emphasize that, while many general concepts and components of meiotic regulation are conserved from frogs to mice, specific differences exist that may lead to important insights regarding ovarian development in vertebrates.

show abstract

A Gβγ stimulated adenylyl cyclase is involved in xenopus laevis oocyte maturation

Cited by 18 publications

References 41 publications

xRic‐8 is a GEF for Gsα and participates in maintaining meiotic arrest in Xenopus laevis oocytes

xRic‐8 is a GEF for Gsα and participates in maintaining meiotic arrest in Xenopus laevis oocytes

The Role of Xenopus Membrane Progesterone Receptor β in Mediating the Effect of Progesterone on Oocyte Maturation

Gβγ signaling reduces intracellular cAMP to promote meiotic progression in mouse oocytes

Contact Info

Product

Resources

About