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Assessment of golgi apparatus versus plasma membrane-localized multi-drug resistance-associated protein 1

Allyn M Kaufmann1, Alana J Toro-Ramos, Jeffrey P Krise

  • 1Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047, USA.

Molecular Pharmaceutics
|June 19, 2008
PubMed

Insights

Multidrug resistance-associated protein 1 (MRP1) can function at the Golgi apparatus, not just the plasma membrane. This finding suggests potential issues in the secretory pathway of some cancer cells.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • ATP-binding cassette superfamily proteins, including multidrug resistance-associated protein 1 (MRP1), are traditionally localized to the plasma membrane (PM).
  • Previous studies indicated MRP1's presence on the Golgi apparatus in multidrug-resistant (MDR) human leukemic cells, but its functional significance and prevalence were unclear.

Purpose of the Study:

  • To investigate the functionality of MRP1 at the Golgi apparatus.
  • To determine if MRP1 localization affects its transport activity.
  • To explore the prevalence and potential causes of aberrant Golgi localization of MRP1 in human leukemic cell lines.

Main Methods:

  • Transfection of MRP1-deficient HeLa cells with MRP1-enhanced green fluorescent protein (MRP1-EGFP).
  • Induction of Golgi localization using monensin treatment.
  • Comparative evaluation of MRP1-mediated substrate (sulforhodamine 101) efflux from the cytosol.

Main Results:

  • MRP1-EGFP localized to the PM in untreated cells and to the Golgi apparatus in monensin-treated cells.
  • The rate of decline in cytosolic sulforhodamine 101 fluorescence was similar, irrespective of MRP1 localization (PM vs. Golgi).
  • Human leukemic cell lines exhibited an inefficient Golgi to PM secretory pathway, potentially explaining Golgi localization of MRP1.

Conclusions:

  • MRP1 demonstrates functionality when localized to the Golgi apparatus.
  • The transport activity of MRP1 is not strictly dependent on its plasma membrane localization.
  • Defective secretory pathways may contribute to the aberrant Golgi localization of MRP1 in certain cancer cells.

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