title: Confocal microscopic analysis of the interaction between cisplatin and the copper transporter ATP7B in human ovarian carcinoma cells.
abstract: Some cisplatin (DDP)-resistant cells overexpress the copper export transporter ATP7B, and cells molecularly engineered to overexpress ATP7B are resistant to DDP. The interaction of Cu with ATP7B normally triggers its relocalization from the perinuclear region to more peripheral vesicles. To investigate the interaction of DDP with ATP7B, we examined the effect of DDP on the subcellular localization of ATP7B using human ovarian carcinoma cells expressing a cyan fluorescent protein (ECFP)-tagged ATP7B (2008/ECFP-ATP7B). ATP7B expression was confirmed in 2008/ECFP-ATP7B cells by Western blotting, and its functionality was documented by showing that it rendered the cells 1.9-fold resistant to CuSO(4) and 4.1-fold resistant to DDP and also reduced the accumulation of both drugs. There was greater sequestration of Pt into intracellular vesicles in the 2008/ECFP-ATP7B cells than in the 2008/ECFP cells. Confocal digital microscopy revealed that ECFP-ATP7B localized in the perinuclear region in absence of drug exposure and that both Cu and DDP triggered relocalization to more peripheral vesicular structures. A fluorescein-labeled form of DDP that retained cytotoxicity and was subject to the same mechanisms of resistance as DDP colocalized with ECFP-ATP7B in the 2008/ECFP-ATP7B cells, whereas the same fluorochrome lacking the DDP moiety did not. These results provide evidence that DDP directly interacts with ATP7B to trigger its relocalization and that ATP7B mediates resistance to DDP by sequestering it into vesicles of the secretory pathway for export from the cell.
authors.affiliation: Department of Medicine, Chemistry and the Cancer Center, University of California, San Diego, La Jolla, California, USA.
authors.forename: Kuniyuki
authors.initials: K
authors.lastname: Katano
authors.forename: Roohangiz
authors.initials: R
authors.lastname: Safaei
authors.forename: Goli
authors.initials: G
authors.lastname: Samimi
authors.forename: Alison
authors.initials: A
authors.lastname: Holzer
authors.forename: Mika
authors.initials: M
authors.lastname: Tomioka
authors.forename: Murray
authors.initials: M
authors.lastname: Goodman
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Howell
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D001692:Biological Transport; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology*; D003001:Cloning, Molecular; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D000073840:Copper-Transporting ATPases; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D018613:Microscopy, Confocal / Q000379:methods*; D008856:Microscopy, Fluorescence; D008956:Models, Chemical; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D011485:Protein Binding; D013997:Time Factors; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D027682:Cation Transport Proteins; C485182:Cyan Fluorescent Protein; D049452:Green Fluorescent Proteins; D003300:Copper; D000251:Adenosine Triphosphatases; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases; D002945:Cisplatin