The ε-Isoform of PKC Mediates the Hypertonic Activation of Cation Channels in Confluent Monolayers of Rat Hepatocytes

Abstract

We were interested whether PKCα, δ, ε or ζ is the isoform actually employed in the activation of hypertonicity-induced cation channels (HICCs) in primary cultures of rat hepatocytes. Quantitative SDS-page and Western-blot experiments revealed that PKCα, δ and ε were stimulated by Indolactam V (as a DAG substitute for activation of c and nPKCs) but that only PKCδ and ε did respond to hypertonic stress. Furthermore, chelation of intracellular Ca⁺⁺ by BAPTA-AM did not alter HICC activation in cable-analysis experiments whereas Indolactam V as well as V8 (an Indolactam derivative specific for PKCδ and ε) activated HICC currents under isotonic conditions. Finally, by use of Rottlerin (as an inhibitor exhibiting a slight preference for PKCδ over ε) PKCε could be identified as the most likely isoform responsible for the activation of the HICC.