Chymotrypsin‐like activity was measured using fluorogenic substrate; Suc‐LLVY‐AMC to measure proteasome activity in homogenates of hSOD1‐WT‐ and hSOD1‐G93A‐expressing NSC‐34 differentiated cells as above in the presence or absence of P110 (1 μM/24 h). Activity levels were quantified and presented as fold change of MOCK (empty vector).