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P-glycoprotein (Pgp) is one of the ABC transporters responsible for the multidrug resistance of cancer cells. The conformational changes of Pgp that occur in the presence of substrates/modulators or ATP depletion are accompanied by the up-shift of UIC2 monoclonal antibody (mAb) binding. In the case of cyclosporin A, vinblastine or valinomycin, this up-shift was found to be concomitant with the near-complete suppression of labeling with other mAbs specific for Pgp epitopes overlapping with UIC2, while pre-treatment with verapamil or Tween 80 brings about a modest suppression. Here we have extended these observations to 44 Pgp interacting agents, and found that only 8 fall into the cyclosporin-like category, inducing a conformational state characterized by the complete UIC2 dominance. The rest of the drugs either did not affect antibody competition or had a modest effect. Thus, Pgp substrates/modulators can be classified into distinct modalities based on the conformational change they elicit.


Henrietta Nagy, Katalin Goda, Ferenc Fenyvesi, Zsolt Bacsó, Mária Szilasi, János Kappelmayer, György Lustyik, Maurizio Cianfriglia, Gábor Szabó. Distinct groups of multidrug resistance modulating agents are distinguished by competition of P-glycoprotein-specific antibodies. Biochemical and biophysical research communications. 2004 Mar 19;315(4):942-9

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PMID: 14985103

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