Genuine Functions of P-Glycoprotein (ABCB1)

Title: Genuine Functions of P-Glycoprotein (ABCB1)

Volume: 9 Issue: 2

Author(s): Takaharu Mizutani, Masatoshi Masuda, Emi Nakai, Kenji Furumiya, Hiroshi Togawa, Yutaka Nakamura, Yuko Kawai, Keiko Nakahira, Shigeko Shinkai and Kazuhiko Takahashi

Affiliation:

Keywords: P-glycoprotein, ABCB1, apoptosis, sphingomyelin, PAF, ceramide

Abstract: P-glycoprotein (P-gp, ABCB1, MDR1) was recognized as a drug-exporting protein from cancer cells three decade ago. Apart from the multidrug transporter side effects of P-gp, normal physiological functions of P-gp have been reported. P-gp could be responsible for translocating platelet-activating factor (PAF) across the plasma membrane and PAF inhibited drug transport mediated by P-gp in cancer cells. P-gp regulated the translocation of sphingomyelin (SM) and GlcCer, and short chain C6-NBD-GlcCer was found in the apical medium of P-gp cells exclusively and not in the basolateral membrane. SM plays an important role in the esterification of cholesterol. High expression of P-gp prevents stem-cell differentiation, leading to the proliferation and amplification of this cell repertoire, and functional P-gp plays a fundamental role in regulating programmed cell death, apoptosis. The transporter function of P-gp is therefore necessary to protect cells from death. P-gp can translocate both C6-NBD-PC and C6-NBD-PE across the apical membrane. This PC translocation was also confirmed with [3H]choline radioactivity. Progesterone is not transported by P-gp, but blocks P-gp-mediated efflux of other drugs and P-gp can mediate the transport of a variety of steroids. Cells transfected with human P-gp esterified more cholesterol. P-gp might also be involved in the transport of cytokines, particularly IL-1β, IL-2, IL-4 and IFNα, out of activated normal lymphocytes into the surrounding medium. P-gp expression is also associated with a volume-activated chloride channel, thus P-gp is bifunctional with both transport and channel regulators. We also present information about P-gp polymorphism and new structural concepts, “gate” and “twist”, of the P-gp structure.

Cite this article as:

Mizutani Takaharu, Masuda Masatoshi, Nakai Emi, Furumiya Kenji, Togawa Hiroshi, Nakamura Yutaka, Kawai Yuko, Nakahira Keiko, Shinkai Shigeko and Takahashi Kazuhiko, Genuine Functions of P-Glycoprotein (ABCB1), Current Drug Metabolism 2008; 9 (2) . https://dx.doi.org/10.2174/138920008783571756