mitolactol and azidopine

P-glycoprotein plays a key role in multidrug resistance of tumor cells. In order to elucidate the possible quarternary structure/function relationship of P-glycoprotein, we treated multidrug-resistant human leukemia K562/ADM cells with the crosslinking reagent, disuccinimidyl suberate. In addition to 180K P-glycoprotein, a 340K protein was immunoprecipitated with an anti-P-glycoprotein monoclonal antibody, MRK-16. The 340K protein is most probably a dimeric P-glycoprotein, since only the 180K P-glycoprotein was immunoprecipitated with MRK-16 when K562/ADM cells were treated with the cleavable crosslinking reagent, dithiobis(succinimidylpropionate), and analysed under reduced conditions. The dimeric P-glycoprotein was photolabeled with [3H]azidopine like the 180K monomeric P-glycoprotein and the photolabeling was inhibited by excess amount of vincristine and verapamil. The dimeric P-glycoprotein could be a functionally active form of the protein involved in the transport of antitumor agents.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Dihydropyridines; Doxorubicin; Drug Resistance; Humans; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Macromolecular Substances; Membrane Glycoproteins; Mitolactol; Mitomycins; Precipitin Tests; Succinimides; Tumor Cells, Cultured; Verapamil; Vincristine