ODC (ornithine decarboxylase) is the rate-limiting enzyme in polyamine biosynthesis. Polyamines are essential for cellular growth and differentiation but enhanced ODC activity is associated with cell transformation. Post-translationally, ODC is negatively regulated through members of the antizyme family. Antizymes inhibit ODC activity, promote ODC degradation through the 26 S proteasome and regulate polyamine transport. Besides the ubiquitously expressed antizymes 1 and 2, there is the tissue-specific antizyme 3 and an yet uncharacterized antizyme 4. Antizyme 1 has been shown to be negatively regulated through the AZI (antizyme inhibitor) that binds antizyme 1 with higher affinity compared with ODC. In the present study, we show by yeast two- and three-hybrid protein–protein interaction studies that AZI interacts with all members of the antizyme family and is capable of disrupting the interaction between each antizyme and ODC. In a yeast-based ODC complementation assay, we show that human ODC is able to complement fully the function of the yeast homologue of ODC. Co-expression of antizymes resulted in ODC inhibition and cessation of yeast growth. The antizyme-induced growth inhibition could be reversed by addition of putrescine or by the co-expression of AZI. The protein interactions could be confirmed by immunoprecipitation of the human ODC–antizyme 2–AZI complexes. In summary, we conclude that human AZI is capable of acting as a general inhibitor for all members of the antizyme family and that the previously not yet characterized antizyme 4 is capable of binding ODC and inhibiting its enzymic activity similar to the other members of the antizyme family.
Research Article| December 14 2004
Regulation of all members of the antizyme family by antizyme inhibitor
Ursula MANGOLD 1
1Center for Functional Genomics, Aventis Pharma GmbH, 82152 Martinsried, Germany
1To whom correspondence should be addressed. Present address: Department of Vascular Biology, Children's Hospital, Harvard Medical School, Boston, MA 02115, U.S.A. (email Ursula.Mangold@childrens.harvard.edu).
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Ursula MANGOLD, Ekkehard LEBERER; Regulation of all members of the antizyme family by antizyme inhibitor. Biochem J 1 January 2005; 385 (1): 21–28. doi: https://doi.org/10.1042/BJ20040547
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