β‐Amyloid efflux mediated by p‐glycoprotein

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Abstract
A large body of evidence suggests that an increase in the brain β-amyloid (Aβ) burden contributes to the etiology of Alzheimer's disease (AD). Much is now known about the intracellular processes regulating the production of Aβ, however, less is known regarding its secretion from cells. We now report that p-glycoprotein (p-gp), an ATP-binding cassette (ABC) transporter, is an Aβ efflux pump. Pharmacological blockade of p-gp rapidly decrease extracellular levels of Aβ secretion. In vitro binding studies showed that addition of synthetic human Aβ1–40 and Aβ1–42 peptides to hamster mdr1-enriched vesicles labeled with the fluorophore MIANS resulted in saturable quenching, suggesting that both peptides interact directly with the transporter. Finally, we were able to directly measure transport of Aβ peptides across the plasma membranes of p-gp enriched vesicles, and showed that this phenomenon was both ATP- and p-gp-dependent. Taken together, our study suggests a novel mechanism of Aβ detachment from cellular membranes, and represents an obvious route towards identification of such a mechanism in the brain.