ORP1L deficiency disrupts endolysosomal function in neurons and exacerbates amyloid pathology in a mouse model of Alzheimer’s disease

Abstract

Membrane contact sites (MCSs) between the endoplasmic reticulum (ER) and endosomes orchestrate lipid transfer, endosome positioning, and lysosomal homeostasis. Emerging evidence implicates disruption of these contacts in neurodegenerative diseases such as Alzheimer’s disease (AD), yet their precise roles in AD pathogenesis remain unclear. We identified oxysterol-binding protein-related protein 1L (ORP1L) to be a strong candidate mediator of neuronal MCS. In mouse primary hippocampal cultures, ORP1L knockdown (KD) induced lipid droplet accumulation, late endosome mislocalization, and lysosomal dysfunction. ORP1L KD also decreased dendritic complexity and reduced miniature excitatory postsynaptic currents (mEPSCs) frequency. In vivo, AAV-mediated ORP1L silencing in the CA1 region of 5XFAD mice doubled amyloid-β deposition and impaired performance in novel object recognition and contextual fear conditioning. Collectively, our data identify ORP1L as a critical regulator of ER–endosome contact site integrity in neurons and demonstrate that its loss exacerbates both cellular and behavioral AD phenotypes. Targeting ORP1L-mediated MCSs may therefore offer a novel therapeutic strategy to preserve neuronal function in neurodegenerative disorders.