Effects of protein kinase C stimulation and free Ca2+ rise in mammalian egg activation

R. Colonna, C. Tatone, A. Malgaroli, F. Eusebi, F. Mangia

Research output: Contribution to journalArticlepeer-review

Abstract

Protein phosphorylation activity, chromosome segregation, and cortical granule exocytosis (CGE) have been studied in mouse eggs activated parthenogenetically by specific PKC stimulators such as 4β-phorbol 12-myristate 13-acetate (PMA) and 1-oleyl-2-acetylglycerol (OAG), or by agents inducing an immediate increase in cytosolic calcium concentration ([Ca2+](i)) such as ethanol and Ca-ionophore A23187. When protein phosphorylation activity of mouse eggs was analyzed 10 min after different activation treatments, the phosphorylation of a 32 kDa polypeptide was a feature common to all different parthenogenetic agents used. The appearance of such labeling was independent of an increasing [Ca2+](i), as indicated by direct measurements of 1) cytosolic Ca2+ concentration with fura-2 and 2) exogenous Ca2+ entrance into activated eggs. Emission of the second polar body was blocked in PMA-elicited parthenogenones, whereas it was apparently normal in OAG-treated eggs, unless the eggs were continuously exposed to OAG. CGE was almost immediate in ethanol-activated eggs, but in PMA-treated cells, it occurred significantly later, with a timing corresponding to that found for the appearance of sustained Ca2+ oscillations in this system. Here, we propose that in mammalian eggs 1) PKC stimulation represents an early regulatory step in egg activation; 2) this kinase activity is turned off before the second meiotic cleavage; and 3) cytosolic free Ca2+ rise is essential for CGE occurrence.

Original languageEnglish
Pages (from-to)171-183
Number of pages13
JournalGamete Research
Volume24
Issue number2
Publication statusPublished - 1989

ASJC Scopus subject areas

  • Developmental Biology
  • Genetics

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