title: Distinct P-glycoprotein precursors are overproduced in independently isolated drug-resistant cell lines.
abstract: A family of P-glycoproteins are overproduced in multidrug-resistant cells derived from the murine macrophage-like line J774.2. To determine whether individual family members are overproduced in response to different drugs, the P-glycoprotein precursors in several independently isolated cell lines, which were selected for resistance to vinblastine or taxol, were compared. Individual cell lines selected with vinblastine overproduced P-glycoprotein precursors of either 120 or 125 kDa. Taxol-selected cell lines overproduced either the 125-kDa precursor or both precursors simultaneously. Two similar but distinct peptide maps for the mature P-glycoproteins were observed. These maps corresponded to each precursor regardless of the drug used for selection. One vinblastine-resistant cell line switched from the 125- to the 120-kDa precursor when grown in increasing concentrations of drug. This change coincided with the overexpression of a distinct subset of mRNA species that code for P-glycoprotein. It is concluded that precursor expression is not drug-specific. These data suggest that individual overproduced P-glycoprotein family members are translated as distinct polypeptides. The results may help to explain the diversity in the multidrug-resistant phenotype.
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D004351:Drug Resistance; D005786:Gene Expression Regulation; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008970:Molecular Weight; D017239:Paclitaxel; D010449:Peptide Mapping; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000470:Alkaloids; D008562:Membrane Glycoproteins; D011498:Protein Precursors; D012333:RNA, Messenger; D014747:Vinblastine; D017239:Paclitaxel; D003078:Colchicine