title: Proteomic analysis reveals that proteasome subunit beta 6 is involved in hypoxia-induced pulmonary vascular remodeling in rats.
abstract: BACKGROUND
  Chronic hypoxia (CH) is known to be one of the major causes of pulmonary hypertension (PH), which is characterized by sustained elevation of pulmonary vascular resistance resulting from vascular remodeling. In this study, we investigated whether the ubiquitin proteasome system (UPS) was involved in the mechanism of hypoxia-induced pulmonary vascular remodeling. We isolated the distal pulmonary artery (PA) from a previously defined chronic hypoxic pulmonary hypertension (CHPH) rat model, performed proteomic analyses in search of differentially expressed proteins belonging to the UPS, and subsequently identified their roles in arterial remodeling.
  
  
  RESULTS
  Twenty-two proteins were differently expressed between the CH and normoxic group. Among them, the expression of proteasome subunit beta (PSMB) 1 and PSMB6 increased after CH exposure. Given that PSMB1 is a well-known structural subunit and PSMB6 is a functional subunit, we sought to assess whether PSMB6 could be related to the multiple functional changes during the CHPH process. We confirmed the proteomic results by real-time PCR and Western blot. With the increase in quantity of the active subunit, proteasome activity in both cultured pulmonary artery smooth muscle cells (PASMCs) and isolated PA from the hypoxic group increased. An MTT assay revealed that the proteasome inhibitor MG132 was able to attenuate the hypoxia-induced proliferation of PASMC in a dose-dependent manner. Knockdown of PSMB6 using siRNA also prevented hypoxia-induced proliferation.
  
  
  CONCLUSIONS
  The present study revealed the association between increased PSMB6 and CHPH. CH up-regulated proteasome activity and the proliferation of PASMCs, which may have been related to increased PSMB6 expression and the subsequently enhanced functional catalytic sites of the proteasome. These results suggested an essential role of the proteasome during CHPH development, a novel finding requiring further study.
authors.affiliation: Guangzhou Institute of Respiratory Diseases, State Key Laboratory of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, Guangzhou, Guangdong, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.forename: Xin
authors.initials: X
authors.lastname: Yun
authors.forename: Kai
authors.initials: K
authors.lastname: Yang
authors.forename: Dongjiang
authors.initials: D
authors.lastname: Liao
authors.forename: Lichun
authors.initials: L
authors.lastname: Tian
authors.forename: Haiyang
authors.initials: H
authors.lastname: Jiang
authors.forename: Wenju
authors.initials: W
authors.lastname: Lu
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D019295:Computational Biology / Q000379:methods; D004195:Disease Models, Animal; D015870:Gene Expression; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006976:Hypertension, Pulmonary / Q000209:etiology*; D000860:Hypoxia / Q000150:complications*; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D011651:Pulmonary Artery / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats
chemical_list: D012333:RNA, Messenger; C586067:PSMB6 protein, rat; D046988:Proteasome Endopeptidase Complex