Nuclear localization of human spermine oxidase isoforms - possible implications in drug response and disease etiology
Nuclear localization of human spermine oxidase isoforms - possible implications in drug response and disease etiology
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DOI：
10.1111/j.1742-4658.2008.06419.x
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发表时间：
2008-06-01
期刊：
影响因子：
5.4
通讯作者：
Casero, Robert A., Jr.
中科院分区：
文献类型：
--
作者：
Murray-Stewart, Tracy;Wang, Yanlin;Casero, Robert A., Jr.
最近发现精胺通过精胺氧化酶（SMO）直接氧化精胺作为一种机制，通过特定的抗肿瘤多胺类似物发挥其细胞毒性作用，激发了人们对多胺分解代谢途径的研究兴趣。精胺氧化的一个主要副产物是H（2）O（2），一种有毒活性氧的来源。最近的靶向小干扰RNA研究已经证实，SMO产生的活性氧直接导致氧化应激，能够诱导细胞凋亡和潜在的致突变DNA损伤。在本研究中，我们描述了人类精胺氧化酶基因的第二种催化活性剪接变体蛋白，命名为SMO 5，其底物特异性和亲和力与最初鉴定的人类精胺氧化酶-1 SMO/PAOh 1相当，因此是H（2）O（2）的额外来源。重要的是，这些SMO亚型中的任一种在NCI-H157人非小细胞肺癌细胞中的过表达导致SMO蛋白在细胞核中的显著定位，如通过共聚焦显微镜所确定的。此外，细胞系过度表达SMO/PAOh 1或SMO 5表现出增加精胺氧化在细胞核中，伴随着个别核多胺浓度的改变。因此，细胞核中精胺的氧化增加，增加了与DNA密切相关的高活性H（2）O（2）的产生，并降低了细胞核中精胺的水平，从而改变了精胺在清除自由基和屏蔽DNA中的保护作用，导致这些细胞中氧化性DNA损伤的可能性总体增加。因此，这些研究的结果具有相当大的意义，无论是在针对多胺氧化作为一种抗肿瘤的策略，并在关于精胺氧化酶在炎症诱导的致癌作用的潜在作用。
The recent discovery of the direct oxidation of spermine via spermine oxidase (SMO) as a mechanism through which specific antitumor polyamine analogues exert their cytotoxic effects has fueled interest in the study of the polyamine catabolic pathway. A major byproduct of spermine oxidation is H(2)O(2), a source of toxic reactive oxygen species. Recent targeted small interfering RNA studies have confirmed that SMO-produced reactive oxygen species are directly responsible for oxidative stress capable of inducing apoptosis and potentially mutagenic DNA damage. In the present study, we describe a second catalytically active splice variant protein of the human spermine oxidase gene, designated SMO5, which exhibits substrate specificities and affinities comparable to those of the originally identified human spermine oxidase-1, SMO/PAOh1, and, as such, is an additional source of H(2)O(2). Importantly, overexpression of either of these SMO isoforms in NCI-H157 human non-small cell lung carcinoma cells resulted in significant localization of SMO protein in the nucleus, as determined by confocal microscopy. Furthermore, cell lines overexpressing either SMO/PAOh1 or SMO5 demonstrated increased spermine oxidation in the nucleus, with accompanying alterations in individual nuclear polyamine concentrations. This increased oxidation of spermine in the nucleus therefore increases the production of highly reactive H(2)O(2) in close proximity to DNA, as well as decreases nuclear spermine levels, thus altering the protective roles of spermine in free radical scavenging and DNA shielding, and resulting in an overall increased potential for oxidative DNA damage in these cells. The results of these studies therefore have considerable significance both with respect to targeting polyamine oxidation as an antineoplastic strategy, and in regard to the potential role of spermine oxidase in inflammation-induced carcinogenesis.