Protein kinase C μ selectively activates the mitogen-activated protein kinase (MAPK) p42 pathway

Here we show that human protein kinase C μ (PKCμ) activates the mitogen-activated protein kinase (MAPK). Transient expression of constitutive active PKCμ leads to an activation of Raf-1 kinase as demonstrated by in vitro phosphorylation of MAPK. PKCμ enhances transcriptional activity of a basal thymidine kinase promotor containing serum response elements (SREs) as shown by luciferase reporter gene assays. SRE driven gene activation by PKCμ is triggered by the Elk-1 ternary complex factor. PKCμ-mediated activation of SRE driven transcription can be inhibited by the MEK1 inhibitor PD98059. In contrast to the activation of the p42/ERK1 MAPK cascade, transient expression of constitutive active PKCμ does neither affect c-jun N-terminal kinase nor p38 MAPK.