BRADYKININ INDUCES TRANSLOCATION OF THE PROTEIN-KINASE-C ISOFORM-ALPHA, ISOFORM-EPSILON, AND ISOFORM-ZETA

Bradykinin exerts a broad spectrum of cellular effects on different ti ssues. It is believed that these effects are predominantly mediated by the recently cloned B2 receptor. The mechanism of post-receptor signa l transduction is not known in detail. Involvement of protein kinase C (PKC) was suggested and activation of the classical PKC isoforms alph a and beta was recently demonstrated. The aim of the present study was to investigate whether the B2 receptor also activates new (delta,epsi lon) and atypical (zeta) PKC isoforms. To investigate this, chinese ha mster ovary (CHO) cells, stably transfected with human B2 receptor, we re used. In these cells the PKC isoforms alpha,delta,epsilon and zeta were detected by immunoblotting with specific antibodies. To monitor h ormone-induced PKC translocation plasma membranes were prepared. Stimu lation of the cells with bradykinin resulted in a rapid (30-60 s) tran slocation of the PKC isoforms alpha,epsilon and zeta. Translocation of PKC delta was not detected. The effect of bradykinin was reduced by s imultaneous addition of the receptor antagonist HOE 140, a bradyki nin -related decapeptide. The data show that the B2 receptor in this cell model is able to activate, in addition to the classical PKC isoform al pha, the new PKC isoform epsilon and the atypical PKC isoform zeta. To test whether these effects are as well observed in a non-transfected cell, the experiments were repeated in human foreskin fibroblasts whic h naturally express high levels of B2 receptors. In this cell system s imilar results on PKC alpha,epsilon and zeta were observed, suggesting that all three PKC isoforms are involved in signal transduction of th e B2 receptor.