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Microinjection of acylphosphatase blocks Xenopus laevis oocytes maturation induced by ras-p21
Abstract:
Ras proteins induce germinal vesicle breakdown (GVBD) when microinjected into Xenopus laevis oocytes. The mechanism of action is still unresolved, although several hypotheses have been proposed. Acylphosphatase is a cytosolic enzyme that specifically catalyses the hydrolysis of the carboxylphosphate bond of acylphosphate for the removal of acylphosphate residues of various membrane pumps. A direct effect of acylphosphatase on the regulation of ionic balance of a cell by interaction with ionic membrane pumps has been proposed. We have analyzed the effect of microinjecting acylphosphatase, by itself or along with ras-p21 proteins or progesterone, into oocytes. The enzyme alone is unable to induce GVBD, but increases oocyte maturation induced by progesterone. By contrast, acylphosphatase blocked GVBD induced by microinjection of oncogenic ras-p21. These data suggest that acylphosphatase acts synergistically or antagonistically with factors involved in proliferating signals by altering the intracellular ionic conditions of the cell, conforming the hypothesis that the intracellular ionic condition of the cell is important in the induction of proliferating signals, and that its perturbation may have a serious effect on signal transduction.
Insights
Acylphosphatase affects oocyte maturation by modulating ionic balance. It enhances progesterone-induced maturation but inhibits ras-p21-induced germinal vesicle breakdown (GVBD), impacting cell proliferation signals.
Area of Science:
- Cellular Biology
- Molecular Biology
- Biochemistry
Background:
- Ras proteins are known to induce germinal vesicle breakdown (GVBD) in Xenopus laevis oocytes, but the precise mechanism remains unclear.
- Acylphosphatase is a cytosolic enzyme involved in hydrolyzing acylphosphate bonds, potentially regulating cellular ionic balance through interaction with membrane pumps.
Purpose of the Study:
- To investigate the role of acylphosphatase in oocyte maturation and its interaction with signaling pathways like Ras.
- To determine if acylphosphatase influences GVBD induced by Ras proteins or progesterone.
Main Methods:
- Microinjection of acylphosphatase, ras-p21 proteins, and progesterone into Xenopus laevis oocytes.
- Observation and analysis of germinal vesicle breakdown (GVBD) and oocyte maturation.
- Assessment of acylphosphatase's independent and combined effects with other agents.
Main Results:
- Acylphosphatase alone did not induce GVBD but potentiated progesterone-induced oocyte maturation.
- Acylphosphatase significantly blocked GVBD induced by microinjected oncogenic ras-p21.
- These findings suggest acylphosphatase modulates cellular ionic conditions, influencing signal transduction pathways.
Conclusions:
- Acylphosphatase plays a dual role, synergizing with maturation signals and antagonizing Ras-mediated proliferation signals.
- The study supports the hypothesis that intracellular ionic conditions are critical for initiating proliferating signals and that their disruption affects signal transduction.