Turku Centre for Biotechnology, University of Turku and Abo Akademi University, Turku, Finland.
Exp Cell Res. 2010 Apr 15;316(7):1169-78. doi: 10.1016/j.yexcr.2010.02.012. Epub 2010 Feb 12.
Cellular oxygen tension is sensed by a family of prolyl hydroxylases (PHD1-3) that regulate the degradation of hypoxia-inducible factors (HIF-1alpha and -2alpha). The PHD2 isoform is considered as the main downregulator of HIF in normoxia. Our previous results have shown that nuclear translocation of PHD2 associates with poorly differentiated tumor phenotype implying that nuclear PHD2 expression is advantageous for tumor growth. Here we show that a pool of PHD2 is shuttled between the nucleus and the cytoplasm. In line with this, accumulation of wild type PHD2 in the nucleus was detected in human colon adenocarcinomas and in cultured carcinoma cells. The PHD2 isoforms showing high nuclear expression increased anchorage-independent carcinoma cell growth. However, retention of PHD2 in the cytoplasm inhibited the anchorage-independent cell growth. A region that inhibits the nuclear localization of PHD2 was identified and the deletion of the region promoted anchorage-independent growth of carcinoma cells. Finally, the cytoplasmic PHD2, as compared with the nuclear PHD2, less efficiently downregulated HIF expression. Forced HIF-1alpha or -2alpha expression decreased and attenuation of HIF expression increased the anchorage-independent cell growth. However, hydroxylase-inactivating mutations in PHD2 had no effect on cell growth. The data imply that nuclear PHD2 localization promotes malignant cancer phenotype.
细胞氧张力由一组脯氨酰羟化酶（PHD1-3）感知，它们调节缺氧诱导因子（HIF-1alpha 和 -2alpha）的降解。PHD2 同工型被认为是常氧下 HIF 的主要下调因子。我们之前的结果表明，PHD2 的核转位与肿瘤分化不良的表型有关，这意味着核 PHD2 的表达有利于肿瘤生长。在这里，我们表明 PHD2 的一部分在核和细胞质之间穿梭。与此一致的是，在人结肠腺癌和培养的癌细胞中检测到野生型 PHD2 在核内的积累。表现出高核表达的 PHD2 同工型增加了非锚定依赖性癌细胞的生长。然而，PHD2 在细胞质中的保留抑制了非锚定依赖性细胞的生长。确定了抑制 PHD2 核定位的区域，该区域的缺失促进了癌细胞的非锚定依赖性生长。最后，与核 PHD2 相比，细胞质 PHD2 下调 HIF 表达的效率较低。强制表达 HIF-1alpha 或 -2alpha 减少了 HIF 表达的衰减，增加了非锚定依赖性细胞的生长。然而，PHD2 中的羟化酶失活突变对细胞生长没有影响。数据表明，核 PHD2 定位促进了恶性癌症表型。
