TAILIEUCHUNG - Báo cáo khoa học: New insights into the P-glycoprotein-mediated effluxes of rhodamines

Multidrug resistance (MDR) in tumour cells is often caused by the overexpression of the plasma drug transporter P-glycoprotein (P-gp). This protein is an active efflux pump for chemotherapeutic drugs,natural products and theadvancesof recent years,we still have an unclear view of the molecular mechanismby which P-gp transports such a wide diversity of compounds across themembrane. | Eur. J. Biochem. 270 476-4185 2003 FEBS 2003 doi New insights into the P-glycoprotein-mediated effluxes of rhodamines Chatchanok Loetchutinat Chantarawan Saengkhae Carole Marbeuf-Gueye and Arlette Garnier-Suillerot Laboratoire de Physicochimie Biomoléculaire et Cellulaire LPBC-CSSB UMR CNRS 7033 Universite Paris Nord Bobigny France Multidrug resistance MDR in tumour cells is often caused by the overexpression of the plasma drug transporter P-glycoprotein P-gp . This protein is an active efflux pump for chemotherapeutic drugs natural products and hydrophobic peptides. Despite the advances of recent years we sti 11 have an unclear view of the molecular mechanism by which P-gp transports such a wide diversity of compounds across the membrane. Measurement of the kinetic characteristics of substrate transport is a powerful approach to enhancing our understanding of their function and mechanism. The aim of the present study was to further characterize the transport of several rhodamine analogues either positively charged or zwitterionic. We took advantage of the intrinsic fluorescence of rhodamines and performed a flow-cytometric analysis of dye accumulation in the wild-type drug sensitive K562 that do not express P-gp and its MDR subline that display high levels of MDR. The measurements were made in real time using intact cells. The kinetic parameter ka VM km which is a measure of the efficiency of the P-gp-mediated efflux of a substrate was similar for almost all the rhodamine analogues tested. In addition these values were compared with those determined previously for the P-gp-mediated efflux of anthuacycline. Our conclusion is that the compounds of these two classes of molecules anthracyclines and rhodam-ines are substrates of P-gp and that their pumping rates at limiting low substrate concentration are similar. The findings presented here are the first to show quantitative information about the kinetic parameters for P-gp-mediated .

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