Upregulation of PKC δ‐ and downregulation of PKC α‐mRNA and protein by a phorbol ester in human T84 cells

Protein kinase C (PKC) family members are downregulated by chronic activation at the protein level in most cell types. In T84 human epithelia] cells 12-O-tetradecanoyl phorbol 13-acetate (TPA) caused persistent translocation of PKC delta to the membrane compartment and a 400% increase of PKC delta-mRNA after 24 h. In contrast, PKC alpha protein was completely downregulated and its mRNA was decreased to 60% of control levels after 24 h. This is the first report of PKC delta-mRNA upregulation by TPA which was previously only shown for PKCbeta. In view of the antimitogenic actions of PKC delta this pattern of regulation may serve to preserve growth control even in the presence of chronic cell activation.