title: Protein kinase Cbeta isoform down-regulates the expression of MDR3 P-glycoprotein in human Chang liver cells.
abstract: The MDR3 protein is a transporter of phosphatidylcholine on the canalicular membrane of human hepatocytes. Previously we showed that the expression of MDR3 mRNA was down-regulated by phorbol 12-myristate 13-acetate (PMA) in human Chang liver cells. In the present study, to elucidate the isoform of protein kinase C (PKC), which influences the level of MDR3 protein, we investigated the effects of PKC-specific inhibitors and antisense oligonucleotides. The level of protein decreased around 50% after treatment for 3-5 days using the dosage of PMA effective against the mRNA expression. The half-life of the MDR3 protein was estimated to be about 5 days. This decrease was antagonized by GF109203X, a non-selective inhibitor of PKCs, and Gö6976, a selective inhibitor for PKCalpha/beta. These inhibitors also suppressed the reduction in MDR3 protein. To specify the isoform of PKC, the cells were treated with antisense oligonucleotide of PKCalpha or PKCbeta. The suppressive effects on MDR3 mRNA of PMA were attenuated in antisense PKCbeta-treated cells, but those in antisense PKCalpha-treated cells were not attenuated. These suggested that PKCbeta plays a regulatory role in the expression of MDR3.
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3, Kanagawa-machi, Kanazawa 920-1181, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Suzuki
authors.forename: Hisao
authors.initials: H
authors.lastname: Hayashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Takagi
authors.forename: Takaaki
authors.initials: T
authors.lastname: Kondo
authors.forename: Kenzo
authors.initials: K
authors.lastname: Takagi
authors.forename: Jun
authors.initials: J
authors.lastname: Ueyama
authors.forename: Shinya
authors.initials: S
authors.lastname: Wakusawa
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000096:biosynthesis* / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis* / Q000235:genetics; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D008099:Liver; D008301:Maleimides / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D064546:Protein Kinase C beta; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D002227:Carbazoles; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; C081021:Go 6976; C095122:multidrug resistance protein 3; D011493:Protein Kinase C; D064546:Protein Kinase C beta; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate