Expression of heme oxygenase-1 in response to proteasomal inhibition.
Heme oxygenase-1 (HO-1) is an antioxidant, antiapoptotic and cytoprotective enzyme, catalysing the degradation of heme to carbon monoxide, biliverdin and ferrous iron. Recent studies indicated that expression of HO-1 is under the control of proapoptotic transcription factor p53 and antioxidant transcription factor Nrf2. Whether each of these transcription factors act independently or there is a cooperation between them in inducing HO-1 expression remains to be elucidated. In this study, we examined the expression of HO-1 in B16F10 melanoma and 4T1 breast cancer cells after cell exposure to proteasome inhibitors. We found that HO-1 protein level is increased by about 70% in p53-wt B16F10 cells in response to proteasome inhibitor MG132 after 6 h. Likewise, a 6.8 fold increase in HO-1 level was observed after cell exposure to the highly specific proteasome inhibitor bortezomib after 6 h of treatment in B16F10 cells. Whereas no induction of HO-1 was observed in p53-null 4T1 cells after treatment with bortezomib for 6 h. Next, we aligned HO-1 untranslated region with a consensus p53-responsive element. This bioinformatic analysis identified a p53-responsive element within the untranslated region of HO-1. Then, we examined HO-1 expression after a prolonged exposure to bortezomib in both B16F10 and 4T1 cell. These analyses similarly indicated that HO-1 is strongly induced in B16F10 cells in a dosedependent; contrary to our expectations, a strong induction of HO-1 is also observed in 4T1 cells. Therefore, it is concluded that HO-1 expression is under the control of p53 during early time points of proteasomal inhibition. However, during prolonged incubation with proteasome inhibitors, HO-1 expression can be induced in a p53-independent manner, suggesting participation of other protein(s) with longer half-lives.
Dumlupınar University, Art and Science Faculty, Department of Biology, Kütahya, Turkey. ayerlikaya@dumlupinar.edu.tr
Azmi
A
Yerlikaya
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D005260:Female; D016158:Genes, p53; D051547:Heme Oxygenase-1 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008546:Melanoma, Experimental / Q000188:drug therapy / Q000201:enzymology; D051379:Mice; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology; D012045:Regulatory Sequences, Nucleic Acid
D001897:Boronic Acids; D007976:Leupeptins; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib; D051547:Heme Oxygenase-1; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde