title: Interaction of P-glycoprotein with protein kinase C in human multidrug resistant carcinoma cells.
abstract: Indirect evidence has suggested that P-glycoprotein (P-gp), the multidrug transporter, is phosphorylated by protein kinase C (PKC) and that phosphorylation modulates its transport function. To address the first premise more directly, ie., that P-gp is phosphorylated by PKC, we investigated the interaction between P-gp and PKC in sensitive and multidrug resistant MCF-7 and KB human carcinoma cell lines. We found that P-gp and PKC were coimmunoprecipitated from the multidrug-resistant cell lines MCF-7/AdrR and KB-V-1, using antibodies to either protein. The association between the two proteins was enhanced by phorbol 12-myristate 13-acetate, an analogue of diacylglycerol that induces translocation of PKC to the plasma membrane. The anti-P-gp immunoprecipitates contained PKC activity as measured by direct phosphorylation reactions. The interaction of PKC with P-gp displayed isozyme specificity: PKC-alpha, -beta, gamma, -epsilon, and -phi, but not -delta, -mu, -zeta, -lambda, were found to coimmunoprecipitate with P-gp. These studies indicate that P-gp closely interacts with PKC and serves as a substrate, and that specific isozymes of this kinase may be involved in the phosphorylation of the multidrug transporter.
authors: Department of Medicine, The Cancer Institute of New Jersey, Piscataway 08854, USA.
authors: J M
authors: JM
authors: Yang
authors: K V
authors: KV
authors: Chin
authors: W N
authors: WN
authors: Hait
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D002277:Carcinoma / Q000188:drug therapy / Q000378:metabolism*; D018432:Drug Resistance, Multiple; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007527:Isoenzymes; D011493:Protein Kinase C