beta-Amyloid efflux mediated by p-glycoprotein

A large body of evidence suggests that an increase in the brain beta -amylo id (A beta) burden contributes to the etiology of Alzheimer's disease (AD). Much is now known about the intracellular processes regulating the product ion of A beta, however, less is known regarding its secretion from cells. W e now report that p-glycoprotein (p-gp), an ATP-binding cassette (ABC) tran sporter, is an A beta efflux pump, Pharmacological blockade of p-gp rapidly decrease extracellular levels of A beta secretion. In vitro binding studie s showed that addition of synthetic human A beta1-40 and A beta1-42 peptide s to hamster mdr1-enriched vesicles labeled with the fluorophore MIANS resu lted in saturable quenching, suggesting that both peptides interact directl y with the transporter. Finally, we were able to directly measure transport of A beta peptides across the plasma membranes of p-gp enriched vesicles, and showed that this phenomenon was both ATP- and p-gp-dependent. Taken tog ether, our study suggests a novel mechanism of A beta detachment from cellu lar membranes, and represents an obvious route towards identification of su ch a mechanism in the brain.