Proteomics Reveals Blood−Brain Barrier Membrane Protein Remodeling in Amyloid-β Pathology

Abstract

The protective function of the blood−brain barrier (BBB) is achieved by membrane proteins expressed in the endothelial cells of brain microvessels, such as tight junction proteins, receptors, and transporters, which regulate the passage of solutes, including nutrients, drugs, and metabolites. In Alzheimer’s disease (AD), characterized by the accumulation of amyloid-β (Aβ) plaques, BBB dysfunction has been widely reported. However, quantitative information on Aβ-associated changes in the membrane proteome in the brain microvasculature remains limited. Here, we investigated the changes in abundances of membrane proteins playing roles in BBB function in the isolated brain microvessels of a mouse model mimicking human Aβ pathology, 5xFAD mice, versus corresponding wild-type (WT) mice using a state-of-the-art liquid chromatography tandem mass spectrometry (LC−MS/MS)-based data-independent acquisition (DIA) quantitative proteomics. In addition, we applied quantitative targeted absolute proteomics to evaluate the impact of Aβ1−42 on the absolute protein abundance of multiple transporters in an in vitro model of brain endothelial cells, hCMEC/D3. We identified changes in the protein abundance of numerous proteins involved in BBB integrity, including tight junction-associated proteins and proteins implicated in Aβ transport and clearance, in the brain microvasculature of 5xFAD mice. Furthermore, Aβ1−42 treatment altered GLUT1 protein abundance and the gene expression of SLC27A1 and SLC22A2 in hCMEC/D3 cells, which play roles in nutrient transport and drug disposition at the BBB. The present study provides novel insights into Aβ-associated molecular alterations in brain microvascular membrane proteins and advances our understanding of BBB changes in AD. The results may support the development of BBB-targeted therapeutic approaches and strategies for optimizing brain drug delivery in AD.