DEVELOPMENTAL EXPRESSION OF THE PROTEIN-KINASE-C FAMILY IN RAT HIPPOCAMPUS

Protein kinase C (PKC) is a heterogeneous family of ten or more isofor ms which plays an important role in neuronal signal transduction. Isof orms from all subclasses are prominently expressed in the rat hippocam pus, as demonstrated by immunoblot with isozyme-specific antisera: Ca2 +-dependent (alpha, beta I, beta II and gamma), Ca2+-independent (delt a, epsilon and a newly characterized PKC related to eta) and atypical( zeta). In addition, the zeta isoform is also found as the free, consti tutively active catalytic domain, protein kinase M zeta (PKM zeta). Tw o distinct patterns of expression of PKC isozymes in rat hippocampus a re found during development from E18 to P28. PKC zeta, PKM zeta and PK C delta are present at birth and their expression does not increase po stnatally. In contrast, the other isoforms are expressed only at low l evels at birth and then increase in the first 4 weeks postnatally. The se two patterns of expression suggest distinct functions for PKC isozy mes during development.