Department of Biological Sciences, Biomedical Research Center, KAIST, Daejeon, 305-701, Republic of Korea.
Life Sci. 2010 Jan 2;86(1-2):66-72. doi: 10.1016/j.lfs.2009.11.010. Epub 2009 Nov 27.
The phosphatase of regenerating liver (PRL) family is related to tumorigenesis and metastasis in various cancer types. Its overexpression increases cell motility and proliferation via the downregulation of p21 expression. In a previous study, we reported that PRL-1 downregulates p53 and is a target gene of p53. In this study, we investigated whether a member of the PRL family, PRL-3, could regulate p53 like PRL-1 in cancer cells.
To elucidate the role of PRL-3 in regulating p53 in cancer cells, we used a cell culture system to measure protein level, transcriptional level, apoptosis or localization.
We determined that PRL-3 overexpression reduced the activity of the p21 and p53 reporters. Additionally, the levels of endogenous and exogenous p53 protein were reduced in cells transiently expressing PRL-3, whereas the ablation of PRL-3 by siRNA increased levels of the p53 protein. The downregulation of p53 by PRL-3 inhibited p53-mediated apoptosis. However, the phosphatase-dead mutant C104S, prenylated-site mutant C170S, and C104S/C170S PRL-3 evidenced minimal effects on the downregulation of p53 protein as compared with wild-type PRL-3. Further examinations revealed that PRL-3 expression reduced the stability of p53 by inducing the transcription of p53 induced protein with a RING-H2 domain (PIRH2) through early growth response (EGR) and by increasing the phosphorylation of mouse double minute 2 (MDM2), and then both negatively regulated p53.
These findings demonstrated that PRL-3, like PRL-1, can negatively regulate p53 via the activation of PIRH2 and MDM2 in cancer cells.
肝再生磷酸酶（PRL）家族与多种癌症类型的肿瘤发生和转移有关。其过表达通过下调 p21 表达增加细胞迁移和增殖。在之前的研究中，我们报道了 PRL-1 下调 p53 并成为 p53 的靶基因。在这项研究中，我们研究了 PRL 家族的一个成员 PRL-3 是否可以像 PRL-1 那样在癌细胞中调节 p53。
为了阐明 PRL-3 在调节癌细胞中 p53 中的作用，我们使用细胞培养系统来测量蛋白质水平、转录水平、凋亡或定位。
我们确定 PRL-3 过表达降低了 p21 和 p53 报告基因的活性。此外，瞬时表达 PRL-3 的细胞中内源性和外源性 p53 蛋白水平降低，而 siRNA 敲除 PRL-3 则增加了 p53 蛋白水平。PRL-3 下调 p53 抑制了 p53 介导的凋亡。然而，与野生型 PRL-3 相比，磷酸酶失活突变体 C104S、 prenylated-site 突变体 C170S 和 C104S/C170S PRL-3 对 p53 蛋白的下调作用最小。进一步的研究表明，PRL-3 通过早期生长反应 (EGR) 诱导含有 RING-H2 结构域的 p53 诱导蛋白（PIRH2）的转录，以及增加鼠双微基因 2 (MDM2) 的磷酸化，从而降低 p53 的稳定性，进而负调控 p53。
这些发现表明，PRL-3 可以像 PRL-1 一样通过激活癌细胞中的 PIRH2 和 MDM2 负向调节 p53。
