SUMO1 promotes Aβ production via the modulation of autophagy

Autophagy is one of the main mechanisms in the pathophysiology of neurodegenerative disease. The accumulation of autophagic vacuoles (AVs) in affected neurons is responsible for amyloid-beta (A beta) production. Previously, we reported that SUMO1 (small ubiquitin-like modifier 1) increases A beta levels. In this study, we explored the mechanisms underlying this. We investigated whether AV formation is necessary for A beta production by SUMO1. Overexpression of SUMO1 increased autophagic activation, inducing the formation of LC3-II-positive AVs in neuroglioma H4 cells. Consistently, autophagic activation was decreased by the depletion of SUMO1 with small hairpin RNA (shRNA) in H4 cells. The SUMO1-mediated increase in A beta was reduced by the autophagy inhibitors (3-methyladenine or wortmannin) or genetic inhibitors (siRNA targeting ATG5, ATG7, ATG12, or HIF1A/, respectively. Accumulation of SUMO1, ATG12, and LC3 was seen in amyloid precursor protein transgenic mice. Our results suggest that SUMO1 accelerates the accumulation of AVs and promotes A beta production, which is a key mechanism for understanding the AV-mediated pathophysiology of Alzheimer disease.