title: Experimentally induced changes in the endocytic traffic of P-glycoprotein alter drug resistance of cancer cells.
abstract: The MDR-1 gene product, plasma membrane glycoprotein or P-glycoprotein (PGP), has been shown to confer drug resistance to cancer cells by acting as an energy-dependent drug-efflux pump. We have examined the endocytic traffic of PGP in human multidrug-resistant cells and tested whether the traffic and the steady-state intracellular localization of PGP can be experimentally modulated. Here we show that 1) under steady state approximately 70% of cellular PGP is on the surface whereas approximately 30% is intracellular, 2) surface PGP undergoes constitutive endocytosis and recycling, 3) endocytosis of PGP involves clathrin and adaptin complex 2-dependent mechanism, and 4) PGP cycles through a Rab5-responsive endosomal compartment. Biochemical (such as antibody crosslinking of PGP or treatment of cells with chloroquine) and molecular (such as overexpression of Rab5) treatments were used to modulate the endocytic/ recycling traffic of PGP. Such treatments resulted in the redistribution of PGP from the cell surface to intracellular compartments. Cells with such "mislocalized" PGP showed a decrease in multidrug resistance, suggesting that clinically relevant strategies can be attempted by modulating PGP's temporal and spatial distribution within cancer cells.
authors.affiliation: Department of Cell Biology, University of Alabama, Birmingham School of Medicine 35294, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Barroso
authors.forename: R
authors.initials: R
authors.lastname: Samanta
authors.forename: L
authors.initials: L
authors.lastname: Greenberger
authors.forename: E
authors.initials: E
authors.lastname: Sztul
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000906:Antibodies / Q000276:immunology; D002277:Carcinoma / Q000473:pathology / Q000503:physiopathology*; D002462:Cell Membrane / Q000378:metabolism; D002738:Chloroquine / Q000494:pharmacology; D002966:Clathrin / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007414:Intestinal Neoplasms / Q000473:pathology / Q000503:physiopathology*; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology; D014407:Tumor Cells, Cultured; D020696:rab5 GTP-Binding Proteins
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000906:Antibodies; D002966:Clathrin; D003432:Cross-Linking Reagents; D008565:Membrane Proteins; D002738:Chloroquine; D019204:GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins