title: A therapeutic dose of doxorubicin activates ubiquitin-proteasome system-mediated proteolysis by acting on both the ubiquitination apparatus and proteasome.
abstract: The ubiquitin proteasome system (UPS) degrades abnormal proteins and most unneeded normal proteins, thereby playing a critical role in protein homeostasis in the cell. Proteasome inhibition is effective in treating certain forms of cancer, while UPS dysfunction is increasingly implicated in the pathogenesis of many severe and yet common diseases. It has been previously shown that doxorubicin (Dox) enhances the degradation of a UPS surrogate substrate in mouse hearts. To address the underlying mechanism, in the present study, we report that 1) Dox not only enhances the degradation of an exogenous UPS reporter (GFPu) but also antagonizes the proteasome inhibitor-induced accumulation of endogenous substrates (e.g., beta-catenin and c-Jun) of the UPS in cultured NIH 3T3 cells and cardiomyocytes; 2) Dox facilitates the in vitro degradation of GFPu and c-Jun by the reconstituted UPS via the enhancement of proteasomal function; 3) Dox at a therapeutically relevant dose directly stimulates the peptidase activities of purified 20S proteasomes; and 4) Dox increases, whereas proteasome inhibition decreases, E3 ligase COOH-terminus of heat shock protein cognate 70 in 3T3 cells via a posttranscriptional mechanism. These new findings suggest that Dox activates the UPS by acting directly on both the ubiquitination apparatus and proteasome.
authors.affiliation: Department of Pathophysiology, Guangzhou Medical College, 195 W. Dongfeng Rd., Guangzhou, Guangdong, China. liujinbaol@yahoo.com.cn
authors.forename: Jinbao
authors.initials: J
authors.lastname: Liu
authors.forename: Hanqiao
authors.initials: H
authors.lastname: Zheng
authors.forename: Mingxin
authors.initials: M
authors.lastname: Tang
authors.forename: Youn-Chul
authors.initials: YC
authors.lastname: Ryu
authors.forename: Xuejun
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects* / Q000201:enzymology; D017930:Genes, Reporter; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology; D041681:NIH 3T3 Cells; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D015853:Cysteine Proteinase Inhibitors; D050883:HSC70 Heat-Shock Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D025801:Ubiquitin; D051176:beta Catenin; D004317:Doxorubicin; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde