| MDR1/ABCB1 belongs to the Mdr/Tap subfamily of the ATP binding casette transporter superfamily (1). MDR1 serves as an efflux pump for xenobiotic compounds with broad substrate specificity. Its substrates include therapeutic agents, such as actinomycin D, etoposide, imatinib, and doxorubicin, as well as endogenous molecules, such as β-amyloids, steroid hormones, lipids, phospholipids, cholesterol, and cytokines (2). Research studies have shown that MDR1 reduces drug accumulation in cancer cells, allowing the development of drug resistance (3-5). On the other hand, MDR1 expressed in the plasma membrane of cells in the blood-brain, blood-cerebral spinal fluid, or blood-placenta barriers restricts the permeability of drugs into these organs from the apical or serosal side (6,7). MDR1 is also expressed in normal tissues with excretory function such as small intestine, liver, and kidney (7). Intracellular MDR1 has been detected in the ER, vesicles, and nuclear envelope, and has been associated with cell trafficking machinery (8). Other reported functions of MDR1 include viral resistance, cytokine trafficking (9,10), and lipid homeostasis in the peripheral and central nervous system (11-13). |
