Neuronal ROS-induced glial lipid droplet formation is altered by loss of Alzheimer’s disease–associated genes

Significance Multiple studies have implicated dozens of risk loci that may be associated with Alzheimer’s disease (AD), but common mechanisms underlying how they may contribute to disease onset or progression remain elusive. This study identifies cell-specific roles for Drosophila orthologs of AD risk genes in lipid droplet formation that, when disrupted, lead to neurodegeneration. Our work reinforces a critical role for the sequestration of peroxidated lipids in glia, and places Apolipoprotein E ε4 (APOE4) with other AD risk factors in the transfer process of lipids from neurons to glia to form lipid droplets. A growing list of Alzheimer’s disease (AD) genetic risk factors is being identified, but the contribution of each variant to disease mechanism remains largely unknown. We have previously shown that elevated levels of reactive oxygen species (ROS) induces lipid synthesis in neurons leading to the sequestration of peroxidated lipids in glial lipid droplets (LD), delaying neurotoxicity. This neuron-to-glia lipid transport is APOD/E-dependent. To identify proteins that modulate these neuroprotective effects, we tested the role of AD risk genes in ROS-induced LD formation and demonstrate that several genes impact neuroprotective LD formation, including homologs of human ABCA1, ABCA7, VLDLR, VPS26, VPS35, AP2A, PICALM, and CD2AP. Our data also show that ROS enhances Aβ42 phenotypes in flies and mice. Finally, a peptide agonist of ABCA1 restores glial LD formation in a humanized APOE4 fly model, highlighting a potentially therapeutic avenue to prevent ROS-induced neurotoxicity. This study places many AD genetic risk factors in a ROS-induced neuron-to-glia lipid transfer pathway with a critical role in protecting against neurotoxicity.