Changes in protein kinase C during vitellogenesis in the crayfish Cherax qyadricarinatus - Possible activation by methyl farnesoate

During ovarian maturation in the crayfish Cherax qundricarinatus, changes i n ovarian protein kinase C (PKC) isoenzymes take place in parallel to yolk accumulation (as shown by immunoblot analysis). Significant changes were re corded in the amounts of specific isoenzymes and in their distribution betw een the cytosol and the membranes. Ovarian maturation was accompanied by th e appearance of high- and low-molecular-weight immunoreactive PKC isoenzyme species. Among the isoenzymes tested, PKC alpha was the most clearly activ ated during ovarian maturation, as shown by significant translocation from the cytosol to the particulate fraction and the appearance of high-molecula r-weight species. Moreover, a similar picture mas obtained in the ovaries o f intersex individuals upon induction of secondary vitellogenesis by androg enic gland ablation. Immunohistological staining showed PKC alpha to be loc alized mainly in the cytosol of premature oocytes, whereas in later maturat ion stages, it was concentrated around the nucleus in a vesicular structure and in the oocyte membrane. In secondary vitellogenic stages, PKC was loca lized in the plasma membrane and apparently in follicular cells. In additio n, its activity was demonstrated by in vitro phosphorylation assays of a cr ash ovarian homogenate. Activation of total PKC phosphorylation of histone, an external substrate, was induced by phosphatidylserine plus 12-O-tetrade canoyl-phorbol-13-acetate (TPA) or methyl farnesoate. Both TPA and methyl f arnesoate stimulated activation of PKC alpha in organ culture, causing its translocation from the cytosol to the membranes and inducing autophosphoryl ation of threonine residues. The changes in PKC isoenzymes during ovarian m aturation in the crayfish suggest their involvement in this process as well as a possible regulatory role for methyl farnesoate through a direct effec t on some PKC isoenzymes. (C) 2000 Academic Press.