Glutamate transporter-1 (GLT-1) dynamics are implicated in excitotoxicity and Alzheimer’s disease (AD) progression. Early stages of AD are often marked by hyperactivity and increased epileptiform activity preceding cognitive decline. Previously, we identified a direct interaction between GLT-1 and Presenilin 1 (PS1) in the brain, highlighting GLT-1 as a promising target in AD research. This study reports the significance of this interaction and uncovers a novel role of GLT-1 in modulating amyloid-beta (Aβ) production. Overexpression of GLT-1 in cells reduces the levels of Aβ40 and Aβ42 by decreasing γ-secretase activity pertinent to APP processing and induces a more “open” PS1 conformation, resulting in decreased Aβ42/40 ratio. Inhibition of the GLT-1/PS1 interaction using cell-permeable peptides produced an opposing effect on Aβ, highlighting the pivotal role of this interaction in regulating Aβ levels. These findings emphasize the potential of targeting the GLT-1/PS1 interaction as a novel therapeutic strategy for AD.

The amyloid precursor protein (APP) is cleaved by β- and γ-secretases, resulting in the generation of β-amyloid (Aβ). Aβ peptides accumulate in the brain of Alzheimer's disease, and the removal of toxic Aβ species using antibodies slows the progression of the disease. However, the potential physiological function(s) of APP and its family members remains elusive. Various studies, including ours, reported that APP C99 is primarily processed by γ-secretase in the endo-lysosomal compartments. Here, we report using a series of complementary assays that the endo-lysosomal membrane in APP/amyloid precursor-like protein 2 (APLP2) deficient mouse embryonic fibroblast cells is more vulnerable to leakage caused by oxidative stress, adeno-associated virus, or tau incubation, compared with that in WT controls. The increased vulnerability of the endo-lysosomal membrane is, in part, rescued by APP overexpression, suggesting the contribution of both APP and APLP2. Mechanistically, we observed distinct lipid profiles, including increased cholesterol and Hex1Cer, between the membrane of APP/APLP2 dKO and that of WT mouse embryonic fibroblast cells. Furthermore, we uncovered higher APP expression in primary neurons from the cerebellum of mouse embryos compared with those from the cortex, and the endo-lysosomal membrane in the cerebellum neurons is less vulnerable to leakage than that in the cortical neurons. Taken together, our findings suggest an unrecognized role of APP and its family member in the regulation of endo-lysosomal membrane vulnerability.

Mutations in the genes encoding APP, Presenilin-1 (PSEN1), and PSEN2 result in early-onset Alzheimer’s disease (AD). Previous studies, using iPSC-derived neurons and/or knock-in mice, elucidated the characteristics of neurons expressing familial AD (fAD) mutations. Here, we employ biochemical and state-of-the-art fluorescence imaging assays and report the discovery of a unique subpopulation of wild-type neurons strikingly recapitulating key phenotypes previously identified in the fAD neurons, including the favored production of longer over shorter β-amyloid (Aβ) peptides, endo-lysosomal abnormalities, and increased vulnerability phenotypes in response to toxic insults. Importantly, mechanistic studies define inefficient γ-secretase and impaired endo-lysosomes as the upstream events of increased neuronal susceptibility. This discovery of the unique population of neurons with disease phenotypes would open a new avenue to develop novel therapeutics targeting neuronal vulnerability.

Glutamate transporter-1 (GLT-1) dynamics are implicated in excitotoxicity and Alzheimer's disease (AD) progression. Early stages of AD are often marked by hyperactivity and increased epileptiform activity preceding cognitive decline. Previously, we identified a direct interaction between GLT-1 and Presenilin 1 (PS1) in the brain, highlighting GLT-1 as a promising target in AD research. This study reports the significance of this interaction and uncovers a novel role of GLT-1 in modulating amyloid-beta (Aβ) production. Overexpression of GLT-1 in cells reduces the levels of Aβ40 and Aβ42 by decreasing γ-secretase activity pertinent to APP processing and induces a more "open" PS1 conformation, resulting in decreased Aβ42/40 ratio. Inhibition of the GLT-1/PS1 interaction using cell-permeable peptides produced an opposing effect on Aβ, highlighting the pivotal role of this interaction in regulating Aβ levels. These findings emphasize the potential of targeting GLT-1/PS1 interaction as a novel therapeutic strategy for AD.