Abstract
Ornithine decarboxylase (ODC) antizyme inhibitor 2 (AZIN2), originally called ODCp, is a regulator of polyamine synthesis that we originally identified and cloned. High expression of ODCp mRNA was found in brain and testis. We reported that AZIN2 is involved in regulation of cellular vesicle transport and / or secretion, but the ultimate physiological role(s) of AZIN2 is still poorly understood. In this study we used a peptide antibody (K3) to human AZIN2 and by immunohistochemistry mapped its expression in various normal tissues. We found high expression in the nervous system, in type 2 pneumocytes in the lung, in megakaryocytes, in gastric parietal cells co-localized with H,K-ATPase beta subunit, in selected enteroendocrine cells, in acinar cells of sweat glands, in podocytes, in macula densa cells and epithelium of collecting ducts in the kidney. The high expression of AZIN2 in various cells with secretory or vesicle transport activity indicates that the polyamine metabolism regulated by AZIN2 is more significantly involved in these events than previously appreciated.
Highlights
The polyamines, putrescine, spermidine and spermine are organic polycations known to be involved in regulation of many fundamental cellular functions like proliferation, differentiation, malignant transformation and apoptosis [1,2]
Since we noticed that cysteine 360, which is critical for Ornithine decarboxylase (ODC) catalytic activity, was substituted by valine in ODC paralog (ODCp) we suggested in the original report that ODCp represents a novel form of ODC antizyme inhibitor [14]
The immunohistochemistry shown in this study is mainly based on an antibody called K3 that reacts with the splicing variants of antizyme inhibitor 2 (AZIN2) containing exons 1 and 2
Summary
The polyamines, putrescine, spermidine and spermine are organic polycations known to be involved in regulation of many fundamental cellular functions like proliferation, differentiation, malignant transformation and apoptosis [1,2]. Ornithine decarboxylase (ODC), which decarboxylates ornithine to generate putrescine, is the rate-limiting enzyme of polyamine synthesis. Elevated ODC activity is typically found in rapidly proliferating cells and in neoplastic tissue. ODC is a transcriptional target of the c-myc oncogene [4] but has itself oncogenic properties. We originally reported that overexpression of human ODC cDNA in NIH3T3 cells induced their malignant transformation [5] with ability to form tumors in athymic mice [6]. Given the cellular impact of ODC its activity is under strict
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