DJ-1 deficiency did not affect MAP1b-LC ubiquitination and functions of ubiquitin proteasomes. A, B Flag-MAP1b-LC was transfected into DJ-1 KD SH-SY5Y cells or scramble controls for 48 hours. The Flag-MAP1b-LC was immunoprecipated and immunoprobed with ubiquitin antibody. The asterisk indicated IgG heavy chain and "#" indicated IgG light chain. C, the proteasome activity of scramble and DJ-1 KD SH-SY5Y cells was measured by the fluorescent peptides succinyl-Leu-Leu-Val-Tyr-AFC, Z-Leu-Leu-Glu-AMC, or Boc-Leu-Arg-Arg-AMC, respectively. D, the proteasome activity of wild type (n = 9) and DJ-1 KO (n = 5) mice brain was measured.