The product of the ABC half-transporter gene ABCG2 (BCRP/MXR/ABCP) is expressed in the plasma membrane.
The products of the ABC gene family can be generally classified as either full-transporters of half-transporters. Full-transporters are expressed in the plasma membrane, whereas half-transporters are usually found in intracellular membranes. Recently, an ABC half-transporter, the ABCG2 gene product Breast Cancer/Mitoxantrone Resistance Protein (BCRP/MXR), has been shown to cause mitoxantrone and topotecan resistance. The purpose of this study was to determine the expression and the intracellular localization of this protein in various drug-resistant cell lines. BCRP/MXR expression was determined by Western blot and immunohistochemistry. This protein is highly overexpressed in several drug-resistant cell lines and localizes predominantly to the plasma membrane, instead of to intracellular membranes as seen with all other known half-transporters. Therefore, BCRP/MXR is unique among the ABC half-transporters by being localized to the plasma membrane.
Rocchi
E
E
Wadsworth Center, New York State Department of Health, Albany, New York 12201, USA.
Khodjakov
A
A
Volk
E L
EL
Yang
C H
CH
Litman
T
T
Bates
S E
SE
Schneider
E
E
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D014407:Tumor Cells, Cultured
D018528:ATP-Binding Cassette Transporters