High expression of antizyme inhibitor 2, an activator of ornithine decarboxylase in steroidogenic cells of human gonads |
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Authors: | Laura T Mäkitie Kristiina Kanerva Anna Sankila Leif C Andersson |
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Institution: | (1) Department of Pathology, Haartman Institute, University of Helsinki, P.O. Box 21, 00014 Helsinki, Finland;(2) HUSLAB, Helsinki, Finland; |
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Abstract: | High activity of ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine synthesis, is typically present in rapidly
proliferating normal and malignant cells. The mitotically inactive steroidogenic cells in rodent testis and ovaries, however,
also display high ODC activity. The activity of ODC in these cells responds to luteinizing hormone, and inhibition of ODC
reduces the production of steroid hormones. Polyamines and ODC also control proliferation of germ cells and spermiogenesis.
The activity of ODC, especially in proliferating cells, is regulated by antizyme inhibitor (AZIN). This protein displaces
ODC from a complex with its inhibitor, antizyme. We have previously identified and cloned a second AZIN, i.e. antizyme inhibitor
2 (AZIN2), which has the highest levels of expression in brain and in testis. In the present study, we have used immunohistochemistry
and in situ hybridization to localize the expression of AZIN2 in human gonads. We found a robust expression of AZIN2 in steroidogenic
cells: testicular Leydig cells and Leydig cell tumors, in ovarian luteinized cells lining corpus luteum cysts, and in hilus
cells. The results suggest that AZIN2 is not primarily involved in regulating the proliferation of the germinal epithelium,
indicating a different role for AZIN1 and AZIN2 in the regulation of ODC. The localization of AZIN2 implies possible involvement
in the gonadal synthesis and/or release of steroid hormones. |
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