Regulation of Xenopus oocyte meiosis arrest by G protein βγ subunits

Sheng, Yinglun; Tiberi, Mario; Booth, Ronald A.; Ma, Chunsheng; Li, Ruizhen

doi:10.1016/s0960-9822(01)00123-3

Cited by 69 publications

(86 citation statements)

References 57 publications

(18 reference statements)

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“…Furthermore, since androgens appear to be physiologic mediators of Xenopus laevis oocyte maturation [90], this system serves as an excellent model for studying extranuclear androgen signaling. Using this model system, studies have shown that just as estrogens regulate G protein and kinase signaling in somatic cells, androgen-induced oocyte maturation requires rapid changes in G protein signaling as well as activation of MAPK signaling [75,78,[91][92][93]. Notably, a key regulator of androgen-triggered kinase signaling in oocytes is paxillin because knockdown of its expression abrogates steroid-triggered kinase signaling and downstream maturation [89].…”

Section: Androgenmentioning

confidence: 99%

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

et al. 2011

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Section: Androgenmentioning

confidence: 99%

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

et al. 2011

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“…Evidence supporting this model is plentiful, including the following: First, steroids trigger a rapid decrease in intracellular cAMP with a concomitant decrease in PKA activity [9][10][11][12]. 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].…”

Section: Meiosis In Frog Oocytesmentioning

confidence: 99%

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

Gill

Hammes

2007

Steroids

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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.

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“…[1][2][3]. Progesterone activates the oocyte through a nontranscriptional cytoplasmic signaling pathway that requires one and possibly two types of receptors: XPR1, a conventional transcriptional progesterone receptor that can also initiate cytoplasmic signaling (4,5), and an unidentified G protein-coupled receptor (6)(7)(8). Despite uncertainties about the earliest steps in receptor action, it is well established that progesterone induces two parallel pathways that converge on the activation of cyclin B-cdc2 (Fig.…”

mentioning

confidence: 99%

G ₂ arrest in Xenopus oocytes depends on phosphorylation of cdc25 by protein kinase A

Duckworth

Weaver

Ruderman

2002

Proc. Natl. Acad. Sci. U.S.A.

196

209

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Xenopus oocytes, which are arrested in G2 of meiosis I, contain complexes of cyclin B-cdc2 (M phase-promoting factor) that are kept repressed by inhibitory phosphorylations on cdc2 at Thr-14 and Tyr-15. Progesterone induces a cytoplasmic signaling pathway that leads to activation of cdc25, the phosphatase that removes these phosphorylations, catalyzing entry into M phase. It has been known for 25 years that high levels of cAMP and protein kinase A (PKA) are required to maintain the G 2 arrest and that a drop in PKA activity is required for M phase-promoting factor activation, but no physiological targets of PKA have been identified. We present evidence that cdc25 is a critical target of PKA. (i) In vitro, cdc25 Ser-287 serves as a major site of phosphorylation by PKA, resulting in sequestration by 14-3-3. (ii) Endogenous cdc25 is phosphorylated on Ser-287 in oocytes and dephosphorylated in response to progesterone just before cdc2 dephosphorylation and M-phase entry. (iii) High PKA activity maintains phosphorylation of Ser-287 in vivo, whereas inhibition of PKA by its heat-stable inhibitor (PKI) induces dephosphorylation of Ser-287. (iv) Overexpression of mutant cdc25 (S287A) bypasses the ability of PKA to maintain oocytes in G 2 arrest. These findings argue that cdc25 is a physiologically relevant target of PKA in oocytes. In the early embryonic cell cycles, Ser-287 is phosphorylated during interphase and dephosphorylated just before cdc2 activation and mitotic entry. Thus, in addition to its role in checkpoint arrest, cdc25 Ser-287 serves as a site for regulation during normal, unperturbed cell cycles.

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Regulation of Xenopus oocyte meiosis arrest by G protein βγ subunits

Abstract: An endogenous G protein betagamma dimer, likely including Xenopus Gbeta1, is responsible for maintaining oocyte meiosis arrest. Resumption of meiosis is induced by Gbetagamma scavengers in vitro or, naturally, by progesterone via a mechanism that suppresses the release of Gbetagamma.

Cited by 69 publications

References 57 publications

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

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

G ₂ arrest in Xenopus oocytes depends on phosphorylation of cdc25 by protein kinase A

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Regulation of Xenopus oocyte meiosis arrest by G protein βγ subunits

Abstract: An endogenous G protein betagamma dimer, likely including Xenopus Gbeta1, is responsible for maintaining oocyte meiosis arrest. Resumption of meiosis is induced by Gbetagamma scavengers in vitro or, naturally, by progesterone via a mechanism that suppresses the release of Gbetagamma.

Cited by 69 publications

References 57 publications

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

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

G 2 arrest in Xenopus oocytes depends on phosphorylation of cdc25 by protein kinase A

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G ₂ arrest in Xenopus oocytes depends on phosphorylation of cdc25 by protein kinase A