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Bap29varP, a variant of Bap29, influences the cell surface expression of the human P-glycoprotein

Prema S Rao1, Ulrich Bickel, Kalkunte S Srivenugopal

  • 1The Anticancer Resistance Research Group and The Cancer Biology Center, Department of Pharmaceutical Sciences, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA. us.rao@ttuhsc.edu

International Journal of Oncology
|December 22, 2007
PubMed

Insights

A newly identified protein, Bap29varP, acts as a chaperone influencing P-glycoprotein (Pgp) trafficking. This protein is crucial for Pgp processing and its movement to the cell surface, impacting multidrug resistance.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • P-glycoprotein (Pgp) is a key factor in multidrug resistance.
  • The mechanism of Pgp targeting to the plasma membrane (PM) is not fully understood.

Purpose of the Study:

  • To identify proteins that regulate Pgp trafficking.
  • To elucidate the role of Bap29varP in Pgp processing and localization.

Main Methods:

  • Yeast two-hybrid analysis to identify interacting proteins.
  • Expression studies in human cancer cell lines (MCF-7, MCF-7/Adr(R), HT-29).
  • Immunofluorescence and Western blot analysis to determine protein localization and molecular mass.

Main Results:

  • A novel endoplasmic reticulum (ER)-bound Bap29 isoform, Bap29varP, was identified as a Pgp-interacting protein.
  • MCF-7/Adr(R) cells express both Bap29varP and Pgp, unlike drug-sensitive MCF-7 cells.
  • Overexpression of Bap29varP caused Pgp to accumulate in the ER and vesicles.
  • Pgp expressed in MCF-7 cells (without Bap29varP) remained in the ER with a lower molecular mass.
  • Pgp expressed in Bap29varP-positive HT-29 cells was localized at the PM.

Conclusions:

  • Bap29varP acts as an essential chaperone for Pgp.
  • Bap29varP influences Pgp processing and trafficking to the cell surface.
  • This interaction is critical for Pgp function in multidrug resistance.

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