The effect of phorbol esters on the expression of mRNA for the alpha subunit of calcium/calmodulin dependent protein kinase II in rabbit renal proximal tubules.

Calcium-calmodulin dependent protein kinase II (CaM-KII) has been implicated in the inhibition of Na(+)-H+ exchange activity in the brush border of the renal proximal convoluted tubule. Conversely, the activity of the antiporter is stimulated in response to phosphorylation by calcium-phospholipid dependent protein kinase (PKC). In these experiments, we explored the potential for direct interaction between these two protein kinases by determining the effect of PKC activation by tumor promoting phorbol esters on the expression of mRNA for CaM-KII in the rabbit renal proximal tubule. The results indicate that activation of PKC reduced the steady-state levels of the mRNA for the alpha subunit of CaM-KII in a dose and time dependent manner. This suggests a novel mechanism by which PKC can antagonize the action of CaM-KII in selected tissues.