Localization of the placental BCRP/ ABCG2 transporter to lipid rafts: Role for cholesterol in mediating efflux activity

Abstract

Introduction The breast cancer resistance protein (BCRP/ABCG2) is an efflux transporter in the placental barrier. By transporting chemicals from the fetal to the maternal circulation, BCRP limits fetal exposure to a range of drugs, toxicants, and endobiotics such as bile acids and hormones. The purpose of the present studies was to 1) determine whether BCRP localizes to highly-ordered, cholesterol-rich lipid raft microdomains in placenta microvillous membranes, and 2) determine the impact of cholesterol on BCRP-mediated placental transport in vitro. Methods BCRP expression was analyzed in lipid rafts isolated from placentas from healthy, term pregnancies and BeWo trophoblasts by density gradient ultracentrifugation. BeWo cells were also tested for their ability to efflux BCRP substrates after treatment with the cholesterol sequestrant methyl-β-cyclodextrin (MβCD, 5mM, 1 h) or the cholesterol synthesis inhibitor pravastatin (200μM, 48 h). Results and Discussion BCRP was found to co-localize with lipid raft proteins in detergent-resistant, lipid raft-containing fractions from placental microvillous membranes and BeWo cells. Treatment of BeWo cells with MβCD redistributed BCRP protein into higher density non-lipid raft fractions. Repletion of the cells with cholesterol restored BCRP localization to lipid raft-containing fractions. Treatment of BeWo cells with MβCD or pravastatin increased cellular retention of two BCRP substrates, the fluorescent dye Hoechst 33342 and the mycotoxin zearalenone. Repletion with cholesterol restored BCRP transporter activity. Taken together, these data demonstrate that cholesterol may play a critical role in the post-translational regulation of BCRP in placental lipid rafts.

Structural basis of small-molecule inhibition of human multidrug transporter ABCG2

“…5a). It was previously demonstrated that membrane cholesterol has an essential role for ABCG2 function, and it was proposed that ABCG2 is mainly localized in lipid rafts of the plasma membrane, where the cholesterol concentration is high [41,42]. Thus, the ordered cholesterol molecules visualized in our structure are likely to be of functional importance.…”

Venetoclax, a BCL-2 Inhibitor, Enhances the Efficacy of Chemotherapeutic Agents in Wild-Type ABCG2-Overexpression-Mediated MDR Cancer Cells

“…As a "half-transporter", ABCG2 most likely exists as homodimers [29]. ABCG2 was discovered in many organs in humans, including liver, kidney, GI tract, CNS, testes, ovaries, adrenal glands and placenta [30]. Substrates of ABCG2 span across different classes, including, but not limited to, topoisomerase inhibitors (mitoxantrone, topotecan, SN-38), antimetabolites (methotrexate), tyrosine kinase inhibitors (imatinib, gefitinib) and non-chemotherapeutic drugs (cimetidine, sulfasalazine, rosuvastatin) [31][32][33][34][35][36][37].…”

Dual TTK/CLK2 inhibitor, CC‐671, selectively antagonizes ABCG2‐mediated multidrug resistance in lung cancer cells

“…16 ABCG2 is expressed in a wide range of tissues and localized on the membrane of several major physiological barriers, including the blood-brain barrier 17 and placenta. 18 It has been suggested that ABCG2 exerts the protective role by reducing the cellular accumulation of toxins. 19,20 However, ABCG2 expression can affect the pharmacokinetic parameters of anticancer drugs.…”