title: Ursodeoxycholic acid modulates the ubiquitin-proteasome degradation pathway of p53.
abstract: p53/Mdm-2 interaction is a prime target of ursodeoxycholic acid (UDCA) for regulating apoptosis in primary rat hepatocytes. Here, we further explored the role of UDCA in downregulating p53 by Mdm-2. UDCA reduced the stability of p53 by decreasing protein half-life. Although proteasomal activity was slightly increased with UDCA, the effect was also observed for other bile acids. More importantly, immunoprecipitation assays revealed that UDCA promoted p53 ubiquitination, therefore leading to increased p53 degradation. In this regard, proteasome inhibition after UDCA pre-treatment resulted in accumulation of ubiquitinated p53, which in turn was prevented in cells overexpressing a mutated form of p53 that does not undergo Mdm-2 ubiquitination. The involvement of Mdm-2 in UDCA-mediated response was further confirmed by siRNA-mediated gene silencing experiments. Finally, the protective effect of UDCA against p53-induced apoptosis was abolished after inhibition of proteasome activity and prevention of p53 ubiquitination by Mdm-2. These findings suggest that UDCA protects cells from p53-mediated apoptosis by promoting its degradation via the Mdm-2-ubiquitin-proteasome pathway.
authors.affiliation: Research Institute for Medicines and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon, Lisbon 1649-003, Portugal.
authors.forename: Joana D
authors.initials: JD
authors.lastname: Amaral
authors.forename: Rui E
authors.initials: RE
authors.lastname: Castro
authors.forename: Susana
authors.initials: S
authors.lastname: Solá
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Steer
authors.forename: Cecília M P
authors.initials: CM
authors.lastname: Rodrigues
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D019610:Cytoprotection; D006207:Half-Life; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D051381:Rats; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects; D014580:Ursodeoxycholic Acid / Q000494:pharmacology*
chemical_list: D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; D014580:Ursodeoxycholic Acid; C497208:Mdm2 protein, rat; D051736:Proto-Oncogene Proteins c-mdm2; D046988:Proteasome Endopeptidase Complex