Disrupting SORL1-retromer endosomal recycling in mice drives the age-dependent neurodegenerative signature of Alzheimer's disease

MRI studies have mapped the atrophic signature that distinguishes Alzheimer's disease (AD), isolating regions differentially vulnerable to its age-dependent neurodegenerative process. An endosomal recycling pathway regulated by the interaction of SORL1 with retromer is pathogenically disrupted in AD. Here we test the hypothesis, that the pathway might drive the neurodegenerative process, via multiple yearlong studies in over 140 wildtype and SORL1 deficient mice, modeling SORL1's causative mutations. MRI studies revealed that SORL1 deficiency induced an age-dependent AD-pattern of atrophy, centered on the trans-entorhinal cortex, and that atrophy was prevented by SORL1 restoration, secondary to overexpressing the retromer protein VPS26b. Postmortem studies validated that the atrophy reflects neuronal loss. Proteomic profiling revealed that the atrophy is associated with reductions in cell death suppressors, one of which was then found deficient in the trans-entorhinal cortex of AD patients. Besides supporting the hypothesis, when taken together with other findings the results suggest that SORL1-retromer disruptions represent a therapeutically-amenable common 'neurodegeneration pathway' in AD.