Characterization of protein kinase C in early Xenopus embryogenesis

Abstract

Recently, we presented evidence that protein kinase C (PKC) is involved in mediating the endogenous signals that induced competent Xenopus ectoderm to differentiate to neural tissue. We report here that PKC is already strongly activated in neural-induced ectoderm from midgastrula embryos and that this activation runs parallel with an increase in the level of inositol phosphates. We further identify several proteins that are phosphorylated, both in natural neural-induced ectoderm and in TPA-treated ectoderm, suggesting that they are phosphorylated through the PKC route. We found no major changes in PKC activity among different pregastrula stages, including the unfertilized egg. However, PKC isolated from animal, ectodermal cells is highly sensitive to Ca2+ and can be activated by low concentrations, (6–25 microM) of arachidonic acid, while PKC isolated from vegetal, endodermal cells is more insensitive to Ca2+ and cannot be activated by arachidonic acid. These results suggest that different PKC isozymes are present in animal and vegetal cells.

RNA binding properties and evoultionary conservation of the Xenopus multifinger protein Xfin

“…It is known that PKC and phosphoinositol phosphate play an essential role in both maturation and fertilization events (see, for Xenopus, refs. 43 and 44), as well as in early embryogenesis (45): in our opinion, an attractive possibility is that Xfi,n activity might be regulated through the PKC/inositol phosphate pathway.…”