LAMTOR1 sorts APP to late endosomes via AP-3-mediated trafficking.

β-Amyloid precursor protein (APP), an amyloid β-peptide (Aβ) generating protein, plays a central role in Alzheimer's disease (AD). Its intracellular trafficking and proteolytic processing are precisely regulated, but the mechanisms remain elusive. Here, we identified LAMTOR1 as a novel APP intracellular domain binding partner that sorts APP from early endosomes to late endosomes. Knockout of LAMTOR1 decreased APP trafficking to late endosomes, which promoted its amyloidogenic processing on early endosomes, resulting in increased Aβ. Conditional knockout of LAMTOR1 in Camk2a-expressing neurons impaired memory function in AD mouse model. Furthermore, the targeting of APP to late endosomes is mediated by adaptor protein complex 3 (AP-3). AP-3 bound to LAMTOR1, and its depletion caused accumulation of LAMTOR1 and APP within early endosomes, subsequently increasing Aβ. Thus, LAMTOR1 functions as a regulator of APP trafficking to late endosomes and may serve as a potential therapeutic target for AD.