Distribution of APP in endo‐lysosomal system induced by Aβ is modulated by Gβγ signaling

Abstract

AbstractBackgroundAlzheimer´s disease is characterized by the deposition of aggregated species of amyloid beta (Aβ) in the brain, which leads to progressive cognitive deficits and dementia. We recently found that Aβ assemblies, oligomers and fibrils, increase APP and BACE1 interaction in recycling endosomes and accumulation of intracellular Aβ42 in human neurons derived from iPSCs by a mechanism dependent of APP/Go/Gβγ signaling (Antonino et al 2022, https://doi.org/10.3389/fcell.2022.852738). Now, we are interested on deepen in the APP trafficking in the endo‐lysosomal pathway in order to understand the mechanism underlying such effect.MethodN2a and human neurons derived from iPSc cultures were transfected with fluorescently tagged proteins (APP‐YFP, BACE‐CH, Rab11‐RFP, LAMP1‐CH, Rab7‐CH, APP‐VN, BACE‐VC). Cultures were treated with vehicle or the Gβγ inhibitor gallein and 30 minutes later with vehicle or 1 µM of Aβ oligomeric or fibrillar. After 24 h of treatment quantitative colocalization analysis and bimolecular fluorescence complementation assays were performed.ResultWe found that Aβ induced an enrichment of APP in recycling endosomes at the expense of a decrement of its levels in lysosomes. This change in APP intracellular distribution is drive by Gβγ signaling. Moreover, we found that the changes on APP distribution correlate with an increase in its interaction with BACE1 and with an increase in the number of recycling endosomes, both events modulated by Gβγ signaling (Figure 1,2).ConclusionTogether, these results suggest that Aβ pathological assemblies induce a re‐direction of APP from its physiological route to lysosomes, to recycling endosomes which favors its encounter with BACE1 and its amyloidogenic processing. These finding elucidate the intracellular process which sustain the feed‐forward mechanisms implicated in the amyloidogenesis induced by pathological assemblies of Aβ.