Role of Ab/APP Interaction in the Increase of APP and BACE 1 Convergence Induced by Abeta

ANTONINO, MAGDALENA; MUSSO, JULIANA; FREITES, LEANDRO; ALFREDO LORENZO; BIGNANTE, ELENA A.

Córdoba

Congreso; XXXIII Reunión Anual de la Sociedad Argentina de Investigación en Neurociencias; 2018

Sociedad Argentina de Investigación en Neurociencias

Alzheimer?s disease (AD) is the most prevalent form of dementia linked to aging and is caused by deposition of the beta amyloid (Aβ) peptide in the brain. Aβ peptide originates from cleavage of amyloid precursor protein (APP) by BACE1 and γ-secretase, being BACE1 the limiting enzyme for Aβ production. APP and BACE1 are transmembrane proteins subjected to intense and complex intracellular trafficking and convergence of both proteins in particular intracellular compartments appears to be critical for amyloidogenic processing of APP. However, the mechanism of APP and BACE1 trafficking and identity of amyloidogenic compartments are still matter of intense debate. Interestingly, experimental evidence suggests that deposition of Aβ can increment its own production triggering a feed-forward pathogenic process in AD. However, the mechanism implicated remains unknown.We hypothesize that deposition of Aβ enhance intracellular convergence of APP and BACE1. Furthermore, since pathogenic forms of Aβ binds to APP activating Go and Gβγ signaling, we postulate that this signaling cascade mediates abnormal regulation of APP and BACE1 trafficking increasing their convergence in amyloidogenic compartments.In this study, we used HELA cells, confocal microscopy and quantitative co-localization analysis to determine the impact of Aβ in the subcellular distribution of APP and BACE1. We found that intracellular colocalization of APP and BACE1 is low in basal conditions, and significantly increases in recycling endosomes after 24 hs of treatment with Aβ 10 µM. Notably, in cells expressing APPΔβ (a deletion-mutant form of APP that lacks binding domain to Aβ) colocalization of APPΔβ and BACE1 in recycling endosome was not altered by Aβ treatment, suggesting that it is triggered by Aβ/APP interaction. Moreover, we found that gallein, a specific Gβγ inhibitor, precludes the increment in colocalization of APP and BACE1 after Aβ treatment, indicating that Go protein and Gβγ signaling mediates redistribution of APP and BACE1. Finally, we found that Aβ also increases co-localization of APP and BACE1 in recycling endosomes in primary neuronal cultures, a process that was effectively abrogated by gallein.In conclusion, we found that Aβ increases localization of APP and BACE1 in recycling endosome, a process that is dependent on the interaction of Aβ/APP and mediated by Go/Gβγ signalling.Our data suggests that interaction of aggregated forms of Aβ with APP might underlie a pathologic feed-forward mechanism of amyloidogenesis in AD, and modulating Go/βγ signaling could be a therapeutic approach to halt progression of Aβ deposition in early stages of the disease.