title: Polyamines directly promote antizyme-mediated degradation of ornithine decarboxylase by the proteasome.
abstract: Ornithine decarboxylase (ODC), a ubiquitin-independent substrate of the proteasome, is a homodimeric protein with a rate-limiting function in polyamine biosynthesis. Polyamines regulate ODC levels by a feedback mechanism mediated by ODC antizyme (OAZ). Higher cellular polyamine levels trigger the synthesis of OAZ and also inhibit its ubiquitin-dependent proteasomal degradation. OAZ binds ODC monomers and targets them to the proteasome. Here, we report that polyamines, aside from their role in the control of OAZ synthesis and stability, directly enhance OAZ-mediated ODC degradation by the proteasome. Using a stable mutant of OAZ, we show that polyamines promote ODC degradation inSaccharomyces cerevisiae cells even when OAZ levels are not changed. Furthermore, polyamines stimulated thein vitrodegradation of ODC by the proteasome in a reconstituted system using purified components. In these assays, spermine shows a greater effect than spermidine. By contrast, polyamines do not have any stimulatory effect on the degradation of ubiquitin-dependent substrates.
authors.affiliation: Institute for Genetics, University of Cologne, Biocenter, Zülpicher Str. 47a, D-50674 Cologne, Germany.
authors.forename: R R
authors.initials: RR
authors.lastname: Beenukumar
authors.affiliation: Institute for Genetics, University of Cologne, Biocenter, Zülpicher Str. 47a, D-50674 Cologne, Germany. ; Present address: Karolinska Institute, Department for Cell- and Molecular Biology, Von Eulers väg 3, 171 77 Stockholm.
authors.forename: Daniela
authors.initials: D
authors.lastname: Gödderz
authors.affiliation: Institute for Genetics, University of Cologne, Biocenter, Zülpicher Str. 47a, D-50674 Cologne, Germany. ; Present address: Center for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500007, India.
authors.forename: R
authors.initials: R
authors.lastname: Palanimurugan
authors.affiliation: Institute for Genetics, University of Cologne, Biocenter, Zülpicher Str. 47a, D-50674 Cologne, Germany.
authors.forename: R J
authors.initials: RJ
authors.lastname: Dohmen
keywords: ODC; antizyme; polyamines; proteasome; ubiquitin