An MDR-EGFP Gene Fusion Allows for Direct Cellular Localization, Function and Stability Assessment of P-Glycoprotein

Author(s): Jordi Petriz, Michael M. Gottesman, Josep M. Aran.

Journal Name: Current Drug Delivery

Volume 1 , Issue 1 , 2004

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Abstract:

In cancer and AIDS, overexpression of the MDR1 gene has important implications in the design of chemotherapy protocols because of the ability of its product, the ATPdependent drug efflux pump P-glycoprotein (Pgp), to confer selective advantage to tumor and HIV-infected cells in the form of multidrug resistance. To study Pgp expression and physiology, we designed a translational fusion between the MDR1 and enhanced green fluorescent protein (EGFP) genes. The chimeric protein, Pgp-EGFP, was concentrated mainly in the plasma membrane and in the Golgi when expressed in drug-sensitive KB- 3-1 cells. Doxorubicin, daunorubicin and rhodamine-123 efflux assays confirmed function of the chimeric pump. Also, at the single-cell level, an inverse relationship between Pgp-EGFP expression and nuclear doxorubicin accumulation was demonstrated. Polarized Pgp expression on the apical cell surface was confirmed by transfection of the MDR-EGFP fusion gene into MDCK cells. However, after colchicine selection, Pgp-EGFP was also detectable in the lateral domain of the transfected MDCK monolayers. These results indicate that drug selection affects not only expression, but cellular localization of Pgp. Furthermore, using a tet-based inducible expression system for Pgp-EGFP, we confirmed the stable nature of Pgp (t1 / 2 total Pgp-EGFP= 2.2 days), but revealed that surface-Pgp acquires extra stability as an active pump (t1 / 2 surface Pgp-EGFP= 3.7 days).

Keywords: p-glycoprotein, green fluorescent protein, drug selection, turnover, subcellular localization

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Article Details

VOLUME: 1
ISSUE: 1
Year: 2004
Page: [43 - 56]
Pages: 14
DOI: 10.2174/1567201043480072

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