Studies with chemical and genetic modifiers of PKC6 suggested that cAMP-induced translocation of NTCP to the plasma membrane (PM) may be mediated via PKC6. However, whether PKC6 is necessary
has not been conclusively established. In addition, PKC6 has been reported to variably affect p38 MAPK activation in non-hepatic cells. However, it is not known whether p38 MAPK is also regulated by PKC6 in hepatocytes. The aim of the present study was to determine the role of PKC6 in cAMP-mediated NTCP translocation and p38 MAPK activation in hepatocytes. All studies were conducted in hepatocytes isolated from 6-8 weeks click here old C57BL/6 WT and PKC6 knockout (KO) mice. A biotinylation method was used to determine PM NTCP. Activations of p38 MAPK and its upstream kinases (MKK3/6, MKK4) were determined using immunoblot analysis of phosphorylated (active) forms. Expressions of
PKC isoforms were determined using immunoblot analysis. Liver function tests and histology were normal in PKC6 KO mice. In addition, expressions of PKCĪ“, PKCe and PKCZ were not altered in PKC6 KO hepato-cytes compared to WT hepatocytes, indicating selleck chemicals llc no compensatory increases in other PKC isoforms in the absence of PKC6. As in rat hepatocytes and hepatic cell lines, cAMP increased PM NTCP in hepatocytes isolated from WT mice. However, cAMP failed to increase PM NTCP in hepatocytes from PKC6 KO mice, indicating that PKC6 is necessary for cAMP-induced PM translocation of mouse NTCP. As previously observed in rat hepatocytes, p38 MAPK was activated by cAMP, taurour-sodeoxycholate (TUDC) and taurolithocholate (TLC) in hepato-cytes from WT mice. However, cAMP, TUDC or TLC failed to increase p38 MAPK phosphorylation in PKC6 KO hepato-cytes. Interestingly, basal phosphorylation of p38 MAPK was 3 fold higher in hepatocytes from PKC6 KO mice compared to WT mice, indicating that p38 MAPK
is negatively regulated by PKC6. To determine GPX6 whether upstream kinases are activated in the absence of PKC6, we compared the basal level of phosphorylation (activation status) of MKK3/6 and MKK4 between WT and PKC6 KO hepatocytes. However, the basal level of phosphorylation of MKK3/6 and MKK4 were comparable between hepatocytes from PKC6 KO and WT mice. The possibility that PKC6 may negatively regulate p38 MAPK in hepatocytes by activating p38 MAPK associated phosphatases remains to be studied. Taken together, these results suggest that PKC6 facilitates cAMP-induced NTCP translocation and negatively regulates p38 MAPK activation in hepatocytes by mechanisms that do not involve upstream kinases. Disclosures: The following people have nothing to disclose: Se Won Park, Christopher M. Schonhoff, Cynthia R. Webster, Mohammed S. Anwer Introduction: Osteopontin (OPN) is a matricellular protein that is highly upregulated in tissue fibrosis and cancers.