title: Aβ40 Reduces P-Glycoprotein at the Blood-Brain Barrier through the Ubiquitin-Proteasome Pathway.
abstract: Failure to clear amyloid-β (Aβ) from the brain is in part responsible for Aβ brain accumulation in Alzheimer's disease (AD). A critical protein for clearing Aβ across the blood-brain barrier is the efflux transporter P-glycoprotein (P-gp) in the luminal plasma membrane of the brain capillary endothelium. P-gp is reduced at the blood-brain barrier in AD, which has been shown to be associated with Aβ brain accumulation. However, the mechanism responsible for P-gp reduction in AD is not well understood. Here we focused on identifying critical mechanistic steps involved in reducing P-gp in AD. We exposed isolated rat brain capillaries to 100 nm Aβ40, Aβ40, aggregated Aβ40, and Aβ42. We observed that only Aβ40 triggered reduction of P-gp protein expression and transport activity levels; this occurred in a dose- and time-dependent manner. To identify the steps involved in Aβ-mediated P-gp reduction, we inhibited protein ubiquitination, protein trafficking, and the ubiquitin-proteasome system, and monitored P-gp protein expression, transport activity, and P-gp-ubiquitin levels. Thus, exposing brain capillaries to Aβ40 triggers ubiquitination, internalization, and proteasomal degradation of P-gp. These findings may provide potential therapeutic targets within the blood-brain barrier to limit P-gp degradation in AD and improve Aβ brain clearance.
  
  
  CONCLUSIONS
  The mechanism reducing blood-brain barrier P-glycoprotein (P-gp) in Alzheimer's disease is poorly understood. In the present study, we focused on defining this mechanism. We demonstrate that Aβ40 drives P-gp ubiquitination, internalization, and proteasome-dependent degradation, reducing P-gp protein expression and transport activity in isolated brain capillaries. These findings may provide potential therapeutic avenues within the blood-brain barrier to limit P-gp degradation in Alzheimer's disease and improve Aβ brain clearance.
authors: Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky 40536, Department of Pharmacy Practice and Pharmaceutical Sciences, College of Pharmacy, University of Minnesota, Duluth, Minnesota 55812, anika.hartz@uky.edu.
authors: Anika M S
authors: AM
authors: Hartz
authors: Sanders-Brown Center on Aging and.
authors: Yu
authors: http://orcid.org/0000-0002-1051-6313
authors: Y
authors: Zhong
authors: Department of Pharmacy Practice and Pharmaceutical Sciences, College of Pharmacy, University of Minnesota, Duluth, Minnesota 55812.
authors: Andrea
authors: A
authors: Wolf
authors: Sanders-Brown Center on Aging and.
authors: Harry
authors: H
authors: LeVine
authors: Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, and.
authors: David S
authors: DS
authors: Miller
authors: Department of Pharmacy Practice and Pharmaceutical Sciences, College of Pharmacy, University of Minnesota, Duluth, Minnesota 55812, Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536.
authors: Björn
authors: B
authors: Bauer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D002196:Capillaries / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D025801:Ubiquitin / Q000187:drug effects*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D025801:Ubiquitin; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D046988:Proteasome Endopeptidase Complex
keywords: Alzheimer's disease; P-glycoprotein; blood–brain barrier; transporter; ubiquitin–proteasome system