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Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β

Elizabeth Roundhill1, Doug Turnbull2, Susan Burchill3

  • 1Children's Cancer Research Group, Leeds Institute of Cancer and Pathology, St. James's University Hospital, Leeds, United Kingdom; and e.a.roundhill@leeds.ac.uk.

FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology
|January 2, 2016
PubMed

Insights

Multidrug resistance-associated protein 1 (MRP-1) in Ewing sarcoma mitochondria is linked to doxorubicin resistance. Targeting mitochondrial MRP-1 enhances chemotherapy effectiveness, offering new therapeutic strategies for this cancer.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Overexpression of plasma membrane multidrug resistance-associated protein 1 (MRP-1) in Ewing sarcoma (ES) correlates with poor patient outcomes.
  • MRP-1 is also found in mitochondria, suggesting a role in chemoresistance beyond the cell surface.

Purpose of the Study:

  • To investigate the submitochondrial localization of MRP-1 in ES.
  • To elucidate the mechanism of MRP-1 transport into mitochondria.
  • To determine the role of mitochondrial MRP-1 in doxorubicin resistance.

Main Methods:

  • Differential centrifugation and digitonin solubilization to determine mitochondrial localization.
  • Immunoprecipitation, immunofluorescence, and HSP knockout (shRNA, inhibitors) to study chaperone interactions.
  • Cell viability assays to assess doxorubicin cytotoxicity after disrupting mitochondrial MRP-1 efflux.

Main Results:

  • Mitochondrial MRP-1 is glycosylated and located on the outer mitochondrial membrane, co-expressed with HSP90.
  • MRP-1 interacts with HSP90 and HSP70; HSP90β inhibition reduces mitochondrial MRP-1 expression.
  • Disrupting mitochondrial MRP-1 efflux significantly enhances doxorubicin's cytotoxic effect (CI < 0.9).

Conclusions:

  • Mitochondrial MRP-1 is localized to the outer mitochondrial membrane and is a client protein of HSP90β.
  • HSP90β mediates the mitochondrial import or stabilization of MRP-1.
  • Mitochondrial MRP-1 plays a role in doxorubicin resistance in Ewing sarcoma, representing a potential therapeutic target.
Keywords:
ABC transporterEwing’s sarcomadoxorubicinmultidrug resistance

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