The cell biology of APOE in the brain.

1. Trends Cell Biol. 2024 Apr;34(4):338-348. doi: 10.1016/j.tcb.2023.09.004. Epub 2023 Oct 5. The cell biology of APOE in the brain. Windham IA(1), Cohen S(2). Author information: (1)Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, NC, USA. (2)Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, NC, USA. Electronic address: sarahcoh@med.unc.edu. Apolipoprotein E (APOE) traffics lipids in the central nervous system. The E4 variant of APOE is a major genetic risk factor for Alzheimer's disease (AD) and a multitude of other neurodegenerative diseases, yet the molecular mechanisms by which APOE4 drives disease are still unclear. A growing collection of studies in iPSC models, knock-in mice, and human postmortem brain tissue have demonstrated that APOE4 expression in astrocytes and microglia is associated with the accumulation of cytoplasmic lipid droplets, defects in endolysosomal trafficking, impaired mitochondrial metabolism, upregulation of innate immune pathways, and a transition into a reactive state. In this review, we collate these developments and suggest testable mechanistic hypotheses that could explain common APOE4 phenotypes. Copyright © 2023 Elsevier Ltd. All rights reserved. DOI: 10.1016/j.tcb.2023.09.004 PMCID: PMC10995109 PMID: 37805344 [Indexed for MEDLINE] Conflict of interest statement: Declaration of interests The authors declare no competing interests.