a Schematic of Triton X-100 extraction to determine protein solubility. b Protein aggregation upon LONP1 knockdown and its rescue by protease-deficient LONP1. Triton X-100 extraction and Western blotting were used to examine protein solubility in LONP1 knockdown 143B cells re-expressing doxycycline (DOX)-inducible RNAi-resistant LONP1WT and protease-deficient LONP1S855A. c Protein insolubility with CDDO treatment, and its rescue by drug treatment or TIM44 knockdown. Triton X-100 extraction and Western blotting were used to examine protein solubility in 143B cells treated with vehicle (-) or CDDO. Additional drug treatment (CCCP or CHX) or TIM44 knockdown was performed as indicated. d Solubility of OXA1L-FLAG. Mitochondria were isolated from 143B cells expressing doxycycline (DOX)-inducible OXA1L-FLAG and analyzed by Triton X-100 extraction and Western blotting. Expression was induced by DOX for 16 h in the absence or presence of 2 μM CDDO. cyt, cytosol; mito, mitochondria. e Visualization of OXA1L-FLAG aggregation. OXA1L-FLAG was induced by DOX in the absence or presence of 2 μM CDDO, and visualized by anti-FLAG immunostaining. Tom20 was used as a mitochondrial marker. Scale bar, 10 μm. f Temporal features of OXA1L aggregation. Triton X-100 extraction and Western blotting were used to examine OXA1L-FLAG solubility. Cells were treated with DOX and 2 μM CDDO for 24 h simultaneously or treated with DOX for 24 h, and after DOX removal, treated with 2 μM CDDO for an additional 24 h.