The present invention provides several modified ABC
transporter polypeptides that exhibit novel localization in the
plasma membrane of polarized and non-polarized cells. The modified ABC
transporter of the invention comprises the
amino acid sequence of a native apically targeted ABC
transporter, in particular cMOAT, MDR3 or MRP4, wherein the terminal
tripeptide T-K-F motif of said native ABC transporter is mutated. The isolated modified ABC transporter polypeptide of the invention, and the
nucleotide sequence encoding said polypeptide, have utility in the following applications: First, they are used to induce a
drug resistant phenotype in a
cell. Second, they are used to protect non-polarized cells during
chemotherapy and other therapeutic applications. Third, they are used to produce novel
cell lines that are used to screen for novel agonists or antagonists of the corresponding native ABC transporter polypeptides.