Protein kinase Cδ mediates cyclic adenosine monophosphate-stimulated translocation of sodium taurocholate cotransporting polypeptide and multidrug resistant associated protein 2 in rat hepatocytes

Cyclic adenosine monophosphate (CAMP) stimulates translocation of Na+-taurocholate (TC) cotransporting polypeptide (Ntcp) and multidrug resistant associated protein 2 (Mrp2) to the plasma membrane. Because cAMP activates phosphoinositide-3-kinase (PI3K) and protein kinase C (PKC) activation is PI3K-dependent, the aim of the current study was to determine whether cAMP activates conventional and novel PKCs in hepatocytes and whether such activation plays a role in cAMP-stimulated Ntcp and Mrp2 translocation. The effect of cAMP on PKCs, TC uptake, and Ntcp and Mrp2 translocation was studied in isolated rat hepatocytes using a cell-permeable cAMP analog, CPT-cAMP. The activity of PKCs was assessed from membrane translocation of individual PKCs, and phospho-specific antibodies were used to determine PKCS phosphorylation. TC uptake was determined from time-dependent uptake of C-14-TC, and a cell surface biotinylation method was used to determine Ntcp and Mrp2 translocation. CPT-cAMP stimulated nPKC delta but not cPKC alpha or nPKC epsilon, and induced PI3K-dependent phosphorylation of nPKC delta at Thr(505). Rottlerin, an inhibitor of nPKCS, inhibited cAMP-induced nPKCS translocation, TC uptake, and Ntcp and Mrp2 translocation. Bistratene A, an activator of nPKCS, stimulated nPKCS translocation, TC uptake, and Ntcp and Mrp2 translocation. The effects of cAMP and bistratene A on TC uptake and Ntcp and Mrp2 translocation were not additive. Conclusion: These results suggest that cAMP stimulates Ntcp and Mrp2 translocation, at least in part, by activating nPKCS via PI3K-dependent phosphorylation at Thr(505).