title: [Impact on tyrosinase expression and export from endoplasmic reticulum by inhibition of 26S proteasome].
abstract: OBJECTIVE
  To determine the impact on tyrosinase expression and export from endoplasmic reticulum by inhibition of 26S proteasome.
  
  
  METHODS
  Western blot was used to detect 26S proteasome from 8 vitiligo patients and 4 healthy controls. Melanocytes were incubated with proteasome inhibitor (lactacystin) and further detected as follows: cell survival by MTT assay, proteasome activity with fluorescence, ultrastructure observation with electron microscope, co-localization of tyrosinase and calreticulin (endoplasmic reticulum marker) by confocal laser scanning microscopy and 26S proteasome and tyrosinase with Western blot.
  
  
  RESULTS
  The 26S proteasome expression level from lesions of vitiligo (1.05 ± 0.40) was significantly lower than the donor sites (1.82 ± 0.88) and the healthy controls (1.88 ± 0.16) (P < 0.05). But no significant difference existed between the latter two groups (P > 0.05). Compared to the untreated group, a 12-h incubation of 10 µmol/L lactacystin showed inhibitory effects on melanocytes (0.999 ± 0.110 vs 1.372 ± 0.127, P < 0.05) and significantly decreased proteasome activity (0.234 ± 0.019 vs 1, P < 0.01). Expansion rate of endoplasmic reticulum in the lactacystin group (1.91 ± 0.17) was significantly higher than that of the untreated cells (1.17 ± 0.11) (P < 0.05). More tyrosinase co-localized with calreticulin in endoplasmic reticulum in lactacystin-treated cells was observed than that of the untreated group. Compared with the untreated group, significantly decreased levels of tyrosinase (146 ± 10 vs 269 ± 8, P < 0.01) and tyrosinase activity (0.159 ± 0.017 vs 0.221 ± 0.019, P < 0.01) were shown in the lactacystin group (P < 0.05).
  
  
  CONCLUSIONS
  Significantly decrease of 26S proteasome is found in lesions of vitiligo patients. Inhibition of 26S proteasome may lead to expansion of endoplasmic reticulum of melanocytes, impact export of tyrosinase from melanocyte endoplasmic reticulum and expression of tyrosinase.
authors: Department of Dermatology, Third People's Hospital of Hangzhou, Hangzhou 310009, China.
authors: Wen
authors: W
authors: Xu
authors: Fu-quan
authors: FQ
authors: Lin
authors: Ji-feng
authors: JF
authors: Liu
authors: Li-fang
authors: LF
authors: Fu
authors: Wei-song
authors: WS
authors: Hong
authors: Miao-ni
authors: MN
authors: Zhou
authors: Ai-e
authors: AE
authors: Xu
authors: Cui-ping
authors: CP
authors: Guan
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000328:Adult; D016022:Case-Control Studies; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008544:Melanocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014820:Vitiligo / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: D015853:Cysteine Proteinase Inhibitors; C067713:lactacystin; D014442:Monophenol Monooxygenase; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000111:Acetylcysteine