Insulin induction of Xenopus laevis oocyte maturation is inhibited by monoclonal antibody against p21 ras proteins

Microinjection of transforming p21 ras protein induces maturation of Xenopus laevis oocytes, and the induction is blocked by coinjection of monoclonal antibody (Y13-259) against p21 ras proteins. Similar to other inducing agents, the effect of p21 ras protein is mediated via the appearance of maturation or meiosis-promoting factor activity. In addition, the neutralizing antibody markedly reduces oocyte maturation after insulin induction, whereas it fails to inhibit progesterone induction. Our results suggest that insulin induces maturation of oocytes via a different pathway than that of steroidal agents. The induction by insulin is ras dependent, and the action of ras may be directed at the steps before meiosis-promoting factor autocatalytic activation. These results suggest a role of p21 ras protein in the events associated with amphibian oocyte maturation.

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Evidence for a role of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase in thapsigargin and Bcl-2 induced changes in Xenopus laevis oocyte maturation

Oncogene ◽

10.1038/sj.onc.1204153 ◽

2001 ◽

Vol 20 (8) ◽

pp. 933-941 ◽

Cited By ~ 8

Author(s):

E M Kobrinsky ◽

M A Kirchberger

Keyword(s):

Endoplasmic Reticulum ◽

Xenopus Laevis ◽

Oocyte Maturation ◽

Xenopus Laevis Oocyte ◽

Induced Changes

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Testosterone and Progesterone Rapidly Attenuate Plasma Membrane Gβγ-Mediated Signaling in Xenopus laevis Oocytes by Signaling through Classical Steroid Receptors

Molecular Endocrinology ◽

10.1210/me.2006-0301 ◽

2007 ◽

Vol 21 (1) ◽

pp. 186-196 ◽

Cited By ~ 26

Author(s):

Kristen Evaul ◽

Michelle Jamnongjit ◽

Bala Bhagavath ◽

Stephen R. Hammes

Keyword(s):

Xenopus Laevis ◽

G Protein ◽

G Proteins ◽

Oocyte Maturation ◽

Live Cells ◽

Inhibition Mechanism ◽

Xenopus Laevis Oocytes ◽

Xenopus Laevis Oocyte ◽

Potassium Influx

Abstract Many transcription-independent (nongenomic) steroid effects are regulated by G proteins. A well-established, biologically relevant example of steroid/G protein interplay is steroid-triggered oocyte maturation, or meiotic resumption, in Xenopus laevis. Oocyte maturation is proposed to occur through a release of inhibition mechanism whereby constitutive signaling by Gβγ and other G proteins maintains oocytes in meiotic arrest. Steroids (androgens in vivo, and androgens and progesterone in vitro) overcome this inhibition to promote meiotic resumption. To test this model, we used G protein-regulated inward rectifying potassium channels (GIRKs) as markers of Gβγ activity. Overexpression of GIRKs 1 and 2 in Xenopus oocytes resulted in constitutive potassium influx, corroborating the presence of basal Gβγ signaling in resting oocytes. Testosterone and progesterone rapidly reduced potassium influx, validating that steroids attenuate Gβγ activity. Interestingly, reduction of classical androgen receptor (AR) expression by RNA interference abrogated testosterone’s effects on GIRK activity at low, but not high, steroid concentrations. Accordingly, androgens bound to the Xenopus progesterone receptor (PR) at high concentrations, suggesting that, in addition to the AR, the PR might mediate G protein signaling when androgens levels are elevated. In contrast, progesterone bound with high affinity to both the Xenopus PR and AR, indicating that progesterone might signal and promote maturation through both receptors, regardless of its concentration. In sum, these studies introduce a novel method for detecting nongenomic steroid effects on G proteins in live cells in real time, and demonstrate that cross talk may occur between steroids and their receptors during Xenopus oocyte maturation.

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Role of zinc in the control of oocyte maturation in Xenopus laevis

Biomedical Research ◽

10.2220/biomedres.21.165 ◽

2000 ◽

Vol 21 (3) ◽

pp. 165-168 ◽

Cited By ~ 1

Author(s):

KEN-ICHI WATANABE ◽

TOSHINOBU TOKUMOTO ◽

KATSUTOSHI ISHIKAWA

Keyword(s):

Xenopus Laevis ◽

Oocyte Maturation

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Phosphorylation and protein synthetic events in Xenopus laevis oocytes microinjected with pp60v-src

Molecular and Cellular Biology ◽

10.1128/mcb.5.12.3629-3633.1985 ◽

1985 ◽

Vol 5 (12) ◽

pp. 3629-3633

Author(s):

J G Spivack ◽

J L Maller

Keyword(s):

Xenopus Laevis ◽

Oocyte Maturation ◽

Rous Sarcoma Virus ◽

Actinomycin D ◽

Meiotic Maturation ◽

Xenopus Laevis Oocytes ◽

Rous Sarcoma ◽

Contrast Exposure ◽

Sarcoma Virus ◽

Qualitative Changes

Microinjection of purified pp60v-src, the transforming protein of Rous sarcoma virus, into Xenopus laevis oocytes accelerated the rate of progesterone- or insulin-induced meiotic maturation. This acceleration was abolished by incubating the oocytes with cycloheximide or puromycin during a 2-h interval between pp60v-src microinjection and progesterone addition. In contrast, exposure to actinomycin D did not alter the acceleration of maturation by microinjected pp60v-src. Associated with progesterone treatment and pp60v-src microinjection were a number of qualitative changes in phosphoproteins; a few of these changes are common to both stimuli. These results indicate that the action of pp60v-src in oocytes involves both phosphorylation and protein synthetic events that affect oocyte maturation.

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Fetal hyperinsulinemia increases farnesylation of p21 Ras in fetal tissues

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.281.2.e217 ◽

2001 ◽

Vol 281 (2) ◽

pp. E217-E223 ◽

Cited By ~ 13

Author(s):

Elizabeth Stephens ◽

Patti J. Thureen ◽

Marc L. Goalstone ◽

Marianne S. Anderson ◽

J. Wayne Leitner ◽

...

Keyword(s):

Growth Factors ◽

Molecular Mechanisms ◽

Fetal Liver ◽

White Blood Cells ◽

Causative Factor ◽

Ras Proteins ◽

Direct Infusion ◽

Fetal Tissues ◽

P21 Ras

Even though the role of fetal hyperinsulinemia in the pathogenesis of fetal macrosomia in patients with overt diabetes and gestational diabetes mellitus seems plausible, the molecular mechanisms of action of hyperinsulinemia remain largely enigmatic. Recent indications that hyperinsulinemia “primes” various tissues to the mitogenic influence of growth factors by increasing the pool of prenylated Ras proteins prompted us to investigate the effect of fetal hyperinsulinemia on the activitiy of farnesyltransferase (FTase) and the amounts of farnesylated p21 Ras in fetal tissues in the ovine experimental model. Induction of fetal hyperinsulinemia by direct infusion of insulin into the fetus and by either fetal or maternal infusions of glucose resulted in significant increases in the activity of FTase and the amounts of farnesylated p21 Ras in fetal liver, skeletal muscle, fat, and white blood cells. An additional infusion of somatostatin into hyperglycemic fetuses blocked fetal hyperinsulinemia and completely prevented these increases, specifying insulin as the causative factor. We conclude that the ability of fetal hyperinsulinemia to increase the size of the pool of farnesylated p21 Ras may prime fetal tissues to the action of other growth factors and thereby constitute one mechanism by which fetal hyperinsulinemia could induce macrosomia in diabetic pregnancies.

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Embryonic Poly(A)-Binding Protein Stimulates Translation in Germ Cells

Molecular and Cellular Biology ◽

10.1128/mcb.25.5.2060-2071.2005 ◽

2005 ◽

Vol 25 (5) ◽

pp. 2060-2071 ◽

Cited By ~ 43

Author(s):

Gavin S. Wilkie ◽

Philippe Gautier ◽

Diane Lawson ◽

Nicola K. Gray

Keyword(s):

Xenopus Laevis ◽

Oocyte Maturation ◽

Germ Cells ◽

Binding Protein ◽

Expression Patterns ◽

General Role ◽

Early Embryos ◽

Relative Divergence

ABSTRACT The function of poly(A)-binding protein 1 (PABP1) in poly(A)-mediated translation has been extensively characterized. Recently, Xenopus laevis oocytes and early embryos were shown to contain a novel poly(A)-binding protein, ePABP, which has not been described in other organisms. ePABP was identified as a protein that binds AU-rich sequences and prevents shortening of poly(A) tails. Here, we show that ePABP is also expressed in X. laevis testis, suggesting a more general role for ePABP in gametogenesis. We find that ePABP is conserved throughout vertebrates and that mouse and X. laevis cells have similar tissue-specific ePABP expression patterns. Furthermore, we directly assess the role of ePABP in translation. We show that ePABP is associated with polysomes and can activate the translation of reporter mRNAs in vivo. Despite its relative divergence from PABP1, we find that ePABP has similar functional domains and can bind to several PABP1 partners, suggesting that they may use similar mechanisms to activate translation. In addition, we find that PABP1 and ePABP can interact, suggesting that these proteins may be bound simultaneously to the same mRNA. Finally, we show that the activity of both PABP1 and ePABP increases during oocyte maturation, when many mRNAs undergo polyadenylation.

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